commit a070db77245acdab7cee5aa2d67e145959aed08c
parent c1a076f8bfe69c7c5f741798f8831de09f9f102a
Author: Christoph Lohmann <20h@r-36.net>
Date: Fri, 21 Dec 2012 18:01:59 +0100
Moving the RFCs to their own rfc folder.
Diffstat:
| add.c | | | 2 | +- |
| proto/rfc1341.txt | | | 5265 | ------------------------------------------------------------------------------- |
| proto/rfc2045.txt | | | 1739 | ------------------------------------------------------------------------------- |
| proto/rfc2046.txt | | | 2467 | ------------------------------------------------------------------------------ |
| proto/rfc2047.txt | | | 843 | ------------------------------------------------------------------------------- |
| proto/rfc2048.txt | | | 1180 | ------------------------------------------------------------------------------- |
| proto/rfc2049.txt | | | 1347 | ------------------------------------------------------------------------------- |
| proto/rfc2183.txt | | | 675 | ------------------------------------------------------------------------------- |
| proto/rfc2231.txt | | | 563 | ------------------------------------------------------------------------------- |
| proto/rfc2387.txt | | | 563 | ------------------------------------------------------------------------------- |
| proto/rfc2425.txt | | | 1851 | ------------------------------------------------------------------------------- |
| proto/rfc2426.txt | | | 2355 | ------------------------------------------------------------------------------- |
| proto/rfc2595.txt | | | 843 | ------------------------------------------------------------------------------- |
| proto/rfc2646.txt | | | 787 | ------------------------------------------------------------------------------- |
| proto/rfc2822.txt | | | 2859 | ------------------------------------------------------------------------------- |
| proto/rfc3501.txt | | | 6051 | ------------------------------------------------------------------------------- |
| proto/rfc4616.txt | | | 619 | ------------------------------------------------------------------------------- |
| proto/rfc5256.txt | | | 1067 | ------------------------------------------------------------------------------- |
| proto/rfc5322.txt | | | 3195 | ------------------------------------------------------------------------------- |
| proto/rfc5804.txt | | | 2747 | ------------------------------------------------------------------------------- |
| proto/rfc822.txt | | | 2901 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc3028.txt | | | 2019 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc3431.txt | | | 451 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc5231.txt | | | 507 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc5260.txt | | | 731 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc5437.txt | | | 787 | ------------------------------------------------------------------------------- |
| proto/sieve/rfc5804.txt | | | 2747 | ------------------------------------------------------------------------------- |
| rfc/rfc1341.txt | | | 5265 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2045.txt | | | 1739 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2046.txt | | | 2467 | ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2047.txt | | | 843 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2048.txt | | | 1180 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2049.txt | | | 1347 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2183.txt | | | 675 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2231.txt | | | 563 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2387.txt | | | 563 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2425.txt | | | 1851 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2426.txt | | | 2355 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2595.txt | | | 843 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2646.txt | | | 787 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2821.txt | | | 4427 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc2822.txt | | | 2859 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc3501.txt | | | 6051 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc4616.txt | | | 619 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc5256.txt | | | 1067 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc5322.txt | | | 3195 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc5804.txt | | | 2747 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/rfc822.txt | | | 2901 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc3028.txt | | | 2019 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc3431.txt | | | 451 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc5231.txt | | | 507 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc5260.txt | | | 731 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc5437.txt | | | 787 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| rfc/sieve/rfc5804.txt | | | 2747 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
54 files changed, 51587 insertions(+), 47160 deletions(-)
diff --git a/add.c b/add.c
@@ -88,7 +88,7 @@ addmain(int argc, char *argv[])
if (flags != NULL) {
flagl = flag_sanitize(flags);
if (flagl == NULL)
- die("Flag parameter seems to be invalid.");
+ die("Flag parameter seems to be invalid.\n");
}
cfg = config_init(cfgn);
diff --git a/proto/rfc1341.txt b/proto/rfc1341.txt
@@ -1,5265 +0,0 @@
-
-
-
-
-
-
- Network Working Group N. Borenstein, Bellcore
- Request for Comments: 1341 N. Freed, Innosoft
- June 1992
-
-
-
- MIME (Multipurpose Internet Mail Extensions):
-
-
- Mechanisms for Specifying and Describing
- the Format of Internet Message Bodies
-
-
- Status of this Memo
-
- This RFC specifies an IAB standards track protocol for the
- Internet community, and requests discussion and suggestions
- for improvements. Please refer to the current edition of
- the "IAB Official Protocol Standards" for the
- standardization state and status of this protocol.
- Distribution of this memo is unlimited.
-
- Abstract
-
- RFC 822 defines a message representation protocol which
- specifies considerable detail about message headers, but
- which leaves the message content, or message body, as flat
- ASCII text. This document redefines the format of message
- bodies to allow multi-part textual and non-textual message
- bodies to be represented and exchanged without loss of
- information. This is based on earlier work documented in
- RFC 934 and RFC 1049, but extends and revises that work.
- Because RFC 822 said so little about message bodies, this
- document is largely orthogonal to (rather than a revision
- of) RFC 822.
-
- In particular, this document is designed to provide
- facilities to include multiple objects in a single message,
- to represent body text in character sets other than US-
- ASCII, to represent formatted multi-font text messages, to
- represent non-textual material such as images and audio
- fragments, and generally to facilitate later extensions
- defining new types of Internet mail for use by cooperating
- mail agents.
-
- This document does NOT extend Internet mail header fields to
- permit anything other than US-ASCII text data. It is
- recognized that such extensions are necessary, and they are
- the subject of a companion document [RFC -1342].
-
- A table of contents appears at the end of this document.
-
-
-
-
-
-
- Borenstein & Freed [Page i]
-
-
-
-
-
-
-
- 1 Introduction
-
- Since its publication in 1982, RFC 822 [RFC-822] has defined
- the standard format of textual mail messages on the
- Internet. Its success has been such that the RFC 822 format
- has been adopted, wholly or partially, well beyond the
- confines of the Internet and the Internet SMTP transport
- defined by RFC 821 [RFC-821]. As the format has seen wider
- use, a number of limitations have proven increasingly
- restrictive for the user community.
-
- RFC 822 was intended to specify a format for text messages.
- As such, non-text messages, such as multimedia messages that
- might include audio or images, are simply not mentioned.
- Even in the case of text, however, RFC 822 is inadequate for
- the needs of mail users whose languages require the use of
- character sets richer than US ASCII [US-ASCII]. Since RFC
- 822 does not specify mechanisms for mail containing audio,
- video, Asian language text, or even text in most European
- languages, additional specifications are needed
-
- One of the notable limitations of RFC 821/822 based mail
- systems is the fact that they limit the contents of
- electronic mail messages to relatively short lines of
- seven-bit ASCII. This forces users to convert any non-
- textual data that they may wish to send into seven-bit bytes
- representable as printable ASCII characters before invoking
- a local mail UA (User Agent, a program with which human
- users send and receive mail). Examples of such encodings
- currently used in the Internet include pure hexadecimal,
- uuencode, the 3-in-4 base 64 scheme specified in RFC 1113,
- the Andrew Toolkit Representation [ATK], and many others.
-
- The limitations of RFC 822 mail become even more apparent as
- gateways are designed to allow for the exchange of mail
- messages between RFC 822 hosts and X.400 hosts. X.400 [X400]
- specifies mechanisms for the inclusion of non-textual body
- parts within electronic mail messages. The current
- standards for the mapping of X.400 messages to RFC 822
- messages specify that either X.400 non-textual body parts
- should be converted to (not encoded in) an ASCII format, or
- that they should be discarded, notifying the RFC 822 user
- that discarding has occurred. This is clearly undesirable,
- as information that a user may wish to receive is lost.
- Even though a user's UA may not have the capability of
- dealing with the non-textual body part, the user might have
- some mechanism external to the UA that can extract useful
- information from the body part. Moreover, it does not allow
- for the fact that the message may eventually be gatewayed
- back into an X.400 message handling system (i.e., the X.400
- message is "tunneled" through Internet mail), where the
- non-textual information would definitely become useful
- again.
-
-
-
-
- Borenstein & Freed [Page 1]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- This document describes several mechanisms that combine to
- solve most of these problems without introducing any serious
- incompatibilities with the existing world of RFC 822 mail.
- In particular, it describes:
-
- 1. A MIME-Version header field, which uses a version number
- to declare a message to be conformant with this
- specification and allows mail processing agents to
- distinguish between such messages and those generated
- by older or non-conformant software, which is presumed
- to lack such a field.
-
- 2. A Content-Type header field, generalized from RFC 1049
- [RFC-1049], which can be used to specify the type and
- subtype of data in the body of a message and to fully
- specify the native representation (encoding) of such
- data.
-
- 2.a. A "text" Content-Type value, which can be used to
- represent textual information in a number of
- character sets and formatted text description
- languages in a standardized manner.
-
- 2.b. A "multipart" Content-Type value, which can be
- used to combine several body parts, possibly of
- differing types of data, into a single message.
-
- 2.c. An "application" Content-Type value, which can be
- used to transmit application data or binary data,
- and hence, among other uses, to implement an
- electronic mail file transfer service.
-
- 2.d. A "message" Content-Type value, for encapsulating
- a mail message.
-
- 2.e An "image" Content-Type value, for transmitting
- still image (picture) data.
-
- 2.f. An "audio" Content-Type value, for transmitting
- audio or voice data.
-
- 2.g. A "video" Content-Type value, for transmitting
- video or moving image data, possibly with audio as
- part of the composite video data format.
-
- 3. A Content-Transfer-Encoding header field, which can be
- used to specify an auxiliary encoding that was applied
- to the data in order to allow it to pass through mail
- transport mechanisms which may have data or character
- set limitations.
-
- 4. Two optional header fields that can be used to further
- describe the data in a message body, the Content-ID and
- Content-Description header fields.
-
-
-
- Borenstein & Freed [Page 2]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- MIME has been carefully designed as an extensible mechanism,
- and it is expected that the set of content-type/subtype
- pairs and their associated parameters will grow
- significantly with time. Several other MIME fields, notably
- including character set names, are likely to have new values
- defined over time. In order to ensure that the set of such
- values is developed in an orderly, well-specified, and
- public manner, MIME defines a registration process which
- uses the Internet Assigned Numbers Authority (IANA) as a
- central registry for such values. Appendix F provides
- details about how IANA registration is accomplished.
-
- Finally, to specify and promote interoperability, Appendix A
- of this document provides a basic applicability statement
- for a subset of the above mechanisms that defines a minimal
- level of "conformance" with this document.
-
- HISTORICAL NOTE: Several of the mechanisms described in
- this document may seem somewhat strange or even baroque at
- first reading. It is important to note that compatibility
- with existing standards AND robustness across existing
- practice were two of the highest priorities of the working
- group that developed this document. In particular,
- compatibility was always favored over elegance.
-
- 2 Notations, Conventions, and Generic BNF Grammar
-
- This document is being published in two versions, one as
- plain ASCII text and one as PostScript. The latter is
- recommended, though the textual contents are identical. An
- Andrew-format copy of this document is also available from
- the first author (Borenstein).
-
- Although the mechanisms specified in this document are all
- described in prose, most are also described formally in the
- modified BNF notation of RFC 822. Implementors will need to
- be familiar with this notation in order to understand this
- specification, and are referred to RFC 822 for a complete
- explanation of the modified BNF notation.
-
- Some of the modified BNF in this document makes reference to
- syntactic entities that are defined in RFC 822 and not in
- this document. A complete formal grammar, then, is obtained
- by combining the collected grammar appendix of this document
- with that of RFC 822.
-
- The term CRLF, in this document, refers to the sequence of
- the two ASCII characters CR (13) and LF (10) which, taken
- together, in this order, denote a line break in RFC 822
- mail.
-
- The term "character set", wherever it is used in this
- document, refers to a coded character set, in the sense of
- ISO character set standardization work, and must not be
-
-
-
- Borenstein & Freed [Page 3]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- misinterpreted as meaning "a set of characters."
-
- The term "message", when not further qualified, means either
- the (complete or "top-level") message being transferred on a
- network, or a message encapsulated in a body of type
- "message".
-
- The term "body part", in this document, means one of the
- parts of the body of a multipart entity. A body part has a
- header and a body, so it makes sense to speak about the body
- of a body part.
-
- The term "entity", in this document, means either a message
- or a body part. All kinds of entities share the property
- that they have a header and a body.
-
- The term "body", when not further qualified, means the body
- of an entity, that is the body of either a message or of a
- body part.
-
- Note : the previous four definitions are clearly circular.
- This is unavoidable, since the overal structure of a MIME
- message is indeed recursive.
-
- In this document, all numeric and octet values are given in
- decimal notation.
-
- It must be noted that Content-Type values, subtypes, and
- parameter names as defined in this document are case-
- insensitive. However, parameter values are case-sensitive
- unless otherwise specified for the specific parameter.
-
- FORMATTING NOTE: This document has been carefully formatted
- for ease of reading. The PostScript version of this
- document, in particular, places notes like this one, which
- may be skipped by the reader, in a smaller, italicized,
- font, and indents it as well. In the text version, only the
- indentation is preserved, so if you are reading the text
- version of this you might consider using the PostScript
- version instead. However, all such notes will be indented
- and preceded by "NOTE:" or some similar introduction, even
- in the text version.
-
- The primary purpose of these non-essential notes is to
- convey information about the rationale of this document, or
- to place this document in the proper historical or
- evolutionary context. Such information may be skipped by
- those who are focused entirely on building a compliant
- implementation, but may be of use to those who wish to
- understand why this document is written as it is.
-
- For ease of recognition, all BNF definitions have been
- placed in a fixed-width font in the PostScript version of
- this document.
-
-
-
- Borenstein & Freed [Page 4]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 3 The MIME-Version Header Field
-
- Since RFC 822 was published in 1982, there has really been
- only one format standard for Internet messages, and there
- has been little perceived need to declare the format
- standard in use. This document is an independent document
- that complements RFC 822. Although the extensions in this
- document have been defined in such a way as to be compatible
- with RFC 822, there are still circumstances in which it
- might be desirable for a mail-processing agent to know
- whether a message was composed with the new standard in
- mind.
-
- Therefore, this document defines a new header field, "MIME-
- Version", which is to be used to declare the version of the
- Internet message body format standard in use.
-
- Messages composed in accordance with this document MUST
- include such a header field, with the following verbatim
- text:
-
- MIME-Version: 1.0
-
- The presence of this header field is an assertion that the
- message has been composed in compliance with this document.
-
- Since it is possible that a future document might extend the
- message format standard again, a formal BNF is given for the
- content of the MIME-Version field:
-
- MIME-Version := text
-
- Thus, future format specifiers, which might replace or
- extend "1.0", are (minimally) constrained by the definition
- of "text", which appears in RFC 822.
-
- Note that the MIME-Version header field is required at the
- top level of a message. It is not required for each body
- part of a multipart entity. It is required for the embedded
- headers of a body of type "message" if and only if the
- embedded message is itself claimed to be MIME-compliant.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 5]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 4 The Content-Type Header Field
-
- The purpose of the Content-Type field is to describe the
- data contained in the body fully enough that the receiving
- user agent can pick an appropriate agent or mechanism to
- present the data to the user, or otherwise deal with the
- data in an appropriate manner.
-
- HISTORICAL NOTE: The Content-Type header field was first
- defined in RFC 1049. RFC 1049 Content-types used a simpler
- and less powerful syntax, but one that is largely compatible
- with the mechanism given here.
-
- The Content-Type header field is used to specify the nature
- of the data in the body of an entity, by giving type and
- subtype identifiers, and by providing auxiliary information
- that may be required for certain types. After the type and
- subtype names, the remainder of the header field is simply a
- set of parameters, specified in an attribute/value notation.
- The set of meaningful parameters differs for the different
- types. The ordering of parameters is not significant.
- Among the defined parameters is a "charset" parameter by
- which the character set used in the body may be declared.
- Comments are allowed in accordance with RFC 822 rules for
- structured header fields.
-
- In general, the top-level Content-Type is used to declare
- the general type of data, while the subtype specifies a
- specific format for that type of data. Thus, a Content-Type
- of "image/xyz" is enough to tell a user agent that the data
- is an image, even if the user agent has no knowledge of the
- specific image format "xyz". Such information can be used,
- for example, to decide whether or not to show a user the raw
- data from an unrecognized subtype -- such an action might be
- reasonable for unrecognized subtypes of text, but not for
- unrecognized subtypes of image or audio. For this reason,
- registered subtypes of audio, image, text, and video, should
- not contain embedded information that is really of a
- different type. Such compound types should be represented
- using the "multipart" or "application" types.
-
- Parameters are modifiers of the content-subtype, and do not
- fundamentally affect the requirements of the host system.
- Although most parameters make sense only with certain
- content-types, others are "global" in the sense that they
- might apply to any subtype. For example, the "boundary"
- parameter makes sense only for the "multipart" content-type,
- but the "charset" parameter might make sense with several
- content-types.
-
- An initial set of seven Content-Types is defined by this
- document. This set of top-level names is intended to be
- substantially complete. It is expected that additions to
- the larger set of supported types can generally be
-
-
-
- Borenstein & Freed [Page 6]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- accomplished by the creation of new subtypes of these
- initial types. In the future, more top-level types may be
- defined only by an extension to this standard. If another
- primary type is to be used for any reason, it must be given
- a name starting with "X-" to indicate its non-standard
- status and to avoid a potential conflict with a future
- official name.
-
- In the Extended BNF notation of RFC 822, a Content-Type
- header field value is defined as follows:
-
- Content-Type := type "/" subtype *[";" parameter]
-
- type := "application" / "audio"
- / "image" / "message"
- / "multipart" / "text"
- / "video" / x-token
-
- x-token := <The two characters "X-" followed, with no
- intervening white space, by any token>
-
- subtype := token
-
- parameter := attribute "=" value
-
- attribute := token
-
- value := token / quoted-string
-
- token := 1*<any CHAR except SPACE, CTLs, or tspecials>
-
- tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in
- / "," / ";" / ":" / "\" / <"> ; quoted-string,
- / "/" / "[" / "]" / "?" / "." ; to use within
- / "=" ; parameter values
-
- Note that the definition of "tspecials" is the same as the
- RFC 822 definition of "specials" with the addition of the
- three characters "/", "?", and "=".
-
- Note also that a subtype specification is MANDATORY. There
- are no default subtypes.
-
- The type, subtype, and parameter names are not case
- sensitive. For example, TEXT, Text, and TeXt are all
- equivalent. Parameter values are normally case sensitive,
- but certain parameters are interpreted to be case-
- insensitive, depending on the intended use. (For example,
- multipart boundaries are case-sensitive, but the "access-
- type" for message/External-body is not case-sensitive.)
-
- Beyond this syntax, the only constraint on the definition of
- subtype names is the desire that their uses must not
- conflict. That is, it would be undesirable to have two
-
-
-
- Borenstein & Freed [Page 7]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- different communities using "Content-Type:
- application/foobar" to mean two different things. The
- process of defining new content-subtypes, then, is not
- intended to be a mechanism for imposing restrictions, but
- simply a mechanism for publicizing the usages. There are,
- therefore, two acceptable mechanisms for defining new
- Content-Type subtypes:
-
- 1. Private values (starting with "X-") may be
- defined bilaterally between two cooperating
- agents without outside registration or
- standardization.
-
- 2. New standard values must be documented,
- registered with, and approved by IANA, as
- described in Appendix F. Where intended for
- public use, the formats they refer to must
- also be defined by a published specification,
- and possibly offered for standardization.
-
- The seven standard initial predefined Content-Types are
- detailed in the bulk of this document. They are:
-
- text -- textual information. The primary subtype,
- "plain", indicates plain (unformatted) text. No
- special software is required to get the full
- meaning of the text, aside from support for the
- indicated character set. Subtypes are to be used
- for enriched text in forms where application
- software may enhance the appearance of the text,
- but such software must not be required in order to
- get the general idea of the content. Possible
- subtypes thus include any readable word processor
- format. A very simple and portable subtype,
- richtext, is defined in this document.
- multipart -- data consisting of multiple parts of
- independent data types. Four initial subtypes
- are defined, including the primary "mixed"
- subtype, "alternative" for representing the same
- data in multiple formats, "parallel" for parts
- intended to be viewed simultaneously, and "digest"
- for multipart entities in which each part is of
- type "message".
- message -- an encapsulated message. A body of
- Content-Type "message" is itself a fully formatted
- RFC 822 conformant message which may contain its
- own different Content-Type header field. The
- primary subtype is "rfc822". The "partial"
- subtype is defined for partial messages, to permit
- the fragmented transmission of bodies that are
- thought to be too large to be passed through mail
- transport facilities. Another subtype,
- "External-body", is defined for specifying large
- bodies by reference to an external data source.
-
-
-
- Borenstein & Freed [Page 8]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- image -- image data. Image requires a display device
- (such as a graphical display, a printer, or a FAX
- machine) to view the information. Initial
- subtypes are defined for two widely-used image
- formats, jpeg and gif.
- audio -- audio data, with initial subtype "basic".
- Audio requires an audio output device (such as a
- speaker or a telephone) to "display" the contents.
- video -- video data. Video requires the capability to
- display moving images, typically including
- specialized hardware and software. The initial
- subtype is "mpeg".
- application -- some other kind of data, typically
- either uninterpreted binary data or information to
- be processed by a mail-based application. The
- primary subtype, "octet-stream", is to be used in
- the case of uninterpreted binary data, in which
- case the simplest recommended action is to offer
- to write the information into a file for the user.
- Two additional subtypes, "ODA" and "PostScript",
- are defined for transporting ODA and PostScript
- documents in bodies. Other expected uses for
- "application" include spreadsheets, data for
- mail-based scheduling systems, and languages for
- "active" (computational) email. (Note that active
- email entails several securityconsiderations,
- which are discussed later in this memo,
- particularly in the context of
- application/PostScript.)
-
- Default RFC 822 messages are typed by this protocol as plain
- text in the US-ASCII character set, which can be explicitly
- specified as "Content-type: text/plain; charset=us-ascii".
- If no Content-Type is specified, either by error or by an
- older user agent, this default is assumed. In the presence
- of a MIME-Version header field, a receiving User Agent can
- also assume that plain US-ASCII text was the sender's
- intent. In the absence of a MIME-Version specification,
- plain US-ASCII text must still be assumed, but the sender's
- intent might have been otherwise.
-
- RATIONALE: In the absence of any Content-Type header field
- or MIME-Version header field, it is impossible to be certain
- that a message is actually text in the US-ASCII character
- set, since it might well be a message that, using the
- conventions that predate this document, includes text in
- another character set or non-textual data in a manner that
- cannot be automatically recognized (e.g., a uuencoded
- compressed UNIX tar file). Although there is no fully
- acceptable alternative to treating such untyped messages as
- "text/plain; charset=us-ascii", implementors should remain
- aware that if a message lacks both the MIME-Version and the
- Content-Type header fields, it may in practice contain
- almost anything.
-
-
-
- Borenstein & Freed [Page 9]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- It should be noted that the list of Content-Type values
- given here may be augmented in time, via the mechanisms
- described above, and that the set of subtypes is expected to
- grow substantially.
-
- When a mail reader encounters mail with an unknown Content-
- type value, it should generally treat it as equivalent to
- "application/octet-stream", as described later in this
- document.
-
- 5 The Content-Transfer-Encoding Header Field
-
- Many Content-Types which could usefully be transported via
- email are represented, in their "natural" format, as 8-bit
- character or binary data. Such data cannot be transmitted
- over some transport protocols. For example, RFC 821
- restricts mail messages to 7-bit US-ASCII data with 1000
- character lines.
-
- It is necessary, therefore, to define a standard mechanism
- for re-encoding such data into a 7-bit short-line format.
- This document specifies that such encodings will be
- indicated by a new "Content-Transfer-Encoding" header field.
- The Content-Transfer-Encoding field is used to indicate the
- type of transformation that has been used in order to
- represent the body in an acceptable manner for transport.
-
- Unlike Content-Types, a proliferation of Content-Transfer-
- Encoding values is undesirable and unnecessary. However,
- establishing only a single Content-Transfer-Encoding
- mechanism does not seem possible. There is a tradeoff
- between the desire for a compact and efficient encoding of
- largely-binary data and the desire for a readable encoding
- of data that is mostly, but not entirely, 7-bit data. For
- this reason, at least two encoding mechanisms are necessary:
- a "readable" encoding and a "dense" encoding.
-
- The Content-Transfer-Encoding field is designed to specify
- an invertible mapping between the "native" representation of
- a type of data and a representation that can be readily
- exchanged using 7 bit mail transport protocols, such as
- those defined by RFC 821 (SMTP). This field has not been
- defined by any previous standard. The field's value is a
- single token specifying the type of encoding, as enumerated
- below. Formally:
-
- Content-Transfer-Encoding := "BASE64" / "QUOTED-PRINTABLE" /
- "8BIT" / "7BIT" /
- "BINARY" / x-token
-
- These values are not case sensitive. That is, Base64 and
- BASE64 and bAsE64 are all equivalent. An encoding type of
- 7BIT requires that the body is already in a seven-bit mail-
- ready representation. This is the default value -- that is,
-
-
-
- Borenstein & Freed [Page 10]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- "Content-Transfer-Encoding: 7BIT" is assumed if the
- Content-Transfer-Encoding header field is not present.
-
- The values "8bit", "7bit", and "binary" all imply that NO
- encoding has been performed. However, they are potentially
- useful as indications of the kind of data contained in the
- object, and therefore of the kind of encoding that might
- need to be performed for transmission in a given transport
- system. "7bit" means that the data is all represented as
- short lines of US-ASCII data. "8bit" means that the lines
- are short, but there may be non-ASCII characters (octets
- with the high-order bit set). "Binary" means that not only
- may non-ASCII characters be present, but also that the lines
- are not necessarily short enough for SMTP transport.
-
- The difference between "8bit" (or any other conceivable
- bit-width token) and the "binary" token is that "binary"
- does not require adherence to any limits on line length or
- to the SMTP CRLF semantics, while the bit-width tokens do
- require such adherence. If the body contains data in any
- bit-width other than 7-bit, the appropriate bit-width
- Content-Transfer-Encoding token must be used (e.g., "8bit"
- for unencoded 8 bit wide data). If the body contains binary
- data, the "binary" Content-Transfer-Encoding token must be
- used.
-
- NOTE: The distinction between the Content-Transfer-Encoding
- values of "binary," "8bit," etc. may seem unimportant, in
- that all of them really mean "none" -- that is, there has
- been no encoding of the data for transport. However, clear
- labeling will be of enormous value to gateways between
- future mail transport systems with differing capabilities in
- transporting data that do not meet the restrictions of RFC
- 821 transport.
-
- As of the publication of this document, there are no
- standardized Internet transports for which it is legitimate
- to include unencoded 8-bit or binary data in mail bodies.
- Thus there are no circumstances in which the "8bit" or
- "binary" Content-Transfer-Encoding is actually legal on the
- Internet. However, in the event that 8-bit or binary mail
- transport becomes a reality in Internet mail, or when this
- document is used in conjunction with any other 8-bit or
- binary-capable transport mechanism, 8-bit or binary bodies
- should be labeled as such using this mechanism.
-
- NOTE: The five values defined for the Content-Transfer-
- Encoding field imply nothing about the Content-Type other
- than the algorithm by which it was encoded or the transport
- system requirements if unencoded.
-
- Implementors may, if necessary, define new Content-
- Transfer-Encoding values, but must use an x-token, which is
- a name prefixed by "X-" to indicate its non-standard status,
-
-
-
- Borenstein & Freed [Page 11]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- e.g., "Content-Transfer-Encoding: x-my-new-encoding".
- However, unlike Content-Types and subtypes, the creation of
- new Content-Transfer-Encoding values is explicitly and
- strongly discouraged, as it seems likely to hinder
- interoperability with little potential benefit. Their use
- is allowed only as the result of an agreement between
- cooperating user agents.
-
- If a Content-Transfer-Encoding header field appears as part
- of a message header, it applies to the entire body of that
- message. If a Content-Transfer-Encoding header field
- appears as part of a body part's headers, it applies only to
- the body of that body part. If an entity is of type
- "multipart" or "message", the Content-Transfer-Encoding is
- not permitted to have any value other than a bit width
- (e.g., "7bit", "8bit", etc.) or "binary".
-
- It should be noted that email is character-oriented, so that
- the mechanisms described here are mechanisms for encoding
- arbitrary byte streams, not bit streams. If a bit stream is
- to be encoded via one of these mechanisms, it must first be
- converted to an 8-bit byte stream using the network standard
- bit order ("big-endian"), in which the earlier bits in a
- stream become the higher-order bits in a byte. A bit stream
- not ending at an 8-bit boundary must be padded with zeroes.
- This document provides a mechanism for noting the addition
- of such padding in the case of the application Content-Type,
- which has a "padding" parameter.
-
- The encoding mechanisms defined here explicitly encode all
- data in ASCII. Thus, for example, suppose an entity has
- header fields such as:
-
- Content-Type: text/plain; charset=ISO-8859-1
- Content-transfer-encoding: base64
-
- This should be interpreted to mean that the body is a base64
- ASCII encoding of data that was originally in ISO-8859-1,
- and will be in that character set again after decoding.
-
- The following sections will define the two standard encoding
- mechanisms. The definition of new content-transfer-
- encodings is explicitly discouraged and should only occur
- when absolutely necessary. All content-transfer-encoding
- namespace except that beginning with "X-" is explicitly
- reserved to the IANA for future use. Private agreements
- about content-transfer-encodings are also explicitly
- discouraged.
-
- Certain Content-Transfer-Encoding values may only be used on
- certain Content-Types. In particular, it is expressly
- forbidden to use any encodings other than "7bit", "8bit", or
- "binary" with any Content-Type that recursively includes
- other Content-Type fields, notably the "multipart" and
-
-
-
- Borenstein & Freed [Page 12]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- "message" Content-Types. All encodings that are desired for
- bodies of type multipart or message must be done at the
- innermost level, by encoding the actual body that needs to
- be encoded.
-
- NOTE ON ENCODING RESTRICTIONS: Though the prohibition
- against using content-transfer-encodings on data of type
- multipart or message may seem overly restrictive, it is
- necessary to prevent nested encodings, in which data are
- passed through an encoding algorithm multiple times, and
- must be decoded multiple times in order to be properly
- viewed. Nested encodings add considerable complexity to
- user agents: aside from the obvious efficiency problems
- with such multiple encodings, they can obscure the basic
- structure of a message. In particular, they can imply that
- several decoding operations are necessary simply to find out
- what types of objects a message contains. Banning nested
- encodings may complicate the job of certain mail gateways,
- but this seems less of a problem than the effect of nested
- encodings on user agents.
-
- NOTE ON THE RELATIONSHIP BETWEEN CONTENT-TYPE AND CONTENT-
- TRANSFER-ENCODING: It may seem that the Content-Transfer-
- Encoding could be inferred from the characteristics of the
- Content-Type that is to be encoded, or, at the very least,
- that certain Content-Transfer-Encodings could be mandated
- for use with specific Content-Types. There are several
- reasons why this is not the case. First, given the varying
- types of transports used for mail, some encodings may be
- appropriate for some Content-Type/transport combinations and
- not for others. (For example, in an 8-bit transport, no
- encoding would be required for text in certain character
- sets, while such encodings are clearly required for 7-bit
- SMTP.) Second, certain Content-Types may require different
- types of transfer encoding under different circumstances.
- For example, many PostScript bodies might consist entirely
- of short lines of 7-bit data and hence require little or no
- encoding. Other PostScript bodies (especially those using
- Level 2 PostScript's binary encoding mechanism) may only be
- reasonably represented using a binary transport encoding.
- Finally, since Content-Type is intended to be an open-ended
- specification mechanism, strict specification of an
- association between Content-Types and encodings effectively
- couples the specification of an application protocol with a
- specific lower-level transport. This is not desirable since
- the developers of a Content-Type should not have to be aware
- of all the transports in use and what their limitations are.
-
- NOTE ON TRANSLATING ENCODINGS: The quoted-printable and
- base64 encodings are designed so that conversion between
- them is possible. The only issue that arises in such a
- conversion is the handling of line breaks. When converting
- from quoted-printable to base64 a line break must be
- converted into a CRLF sequence. Similarly, a CRLF sequence
-
-
-
- Borenstein & Freed [Page 13]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- in base64 data should be converted to a quoted-printable
- line break, but ONLY when converting text data.
-
- NOTE ON CANONICAL ENCODING MODEL: There was some
- confusion, in earlier drafts of this memo, regarding the
- model for when email data was to be converted to canonical
- form and encoded, and in particular how this process would
- affect the treatment of CRLFs, given that the representation
- of newlines varies greatly from system to system. For this
- reason, a canonical model for encoding is presented as
- Appendix H.
-
- 5.1 Quoted-Printable Content-Transfer-Encoding
-
- The Quoted-Printable encoding is intended to represent data
- that largely consists of octets that correspond to printable
- characters in the ASCII character set. It encodes the data
- in such a way that the resulting octets are unlikely to be
- modified by mail transport. If the data being encoded are
- mostly ASCII text, the encoded form of the data remains
- largely recognizable by humans. A body which is entirely
- ASCII may also be encoded in Quoted-Printable to ensure the
- integrity of the data should the message pass through a
- character-translating, and/or line-wrapping gateway.
-
- In this encoding, octets are to be represented as determined
- by the following rules:
-
- Rule #1: (General 8-bit representation) Any octet,
- except those indicating a line break according to the
- newline convention of the canonical form of the data
- being encoded, may be represented by an "=" followed by
- a two digit hexadecimal representation of the octet's
- value. The digits of the hexadecimal alphabet, for this
- purpose, are "0123456789ABCDEF". Uppercase letters must
- be
- used when sending hexadecimal data, though a robust
- implementation may choose to recognize lowercase
- letters on receipt. Thus, for example, the value 12
- (ASCII form feed) can be represented by "=0C", and the
- value 61 (ASCII EQUAL SIGN) can be represented by
- "=3D". Except when the following rules allow an
- alternative encoding, this rule is mandatory.
-
- Rule #2: (Literal representation) Octets with decimal
- values of 33 through 60 inclusive, and 62 through 126,
- inclusive, MAY be represented as the ASCII characters
- which correspond to those octets (EXCLAMATION POINT
- through LESS THAN, and GREATER THAN through TILDE,
- respectively).
-
- Rule #3: (White Space): Octets with values of 9 and 32
- MAY be represented as ASCII TAB (HT) and SPACE
- characters, respectively, but MUST NOT be so
-
-
-
- Borenstein & Freed [Page 14]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- represented at the end of an encoded line. Any TAB (HT)
- or SPACE characters on an encoded line MUST thus be
- followed on that line by a printable character. In
- particular, an "=" at the end of an encoded line,
- indicating a soft line break (see rule #5) may follow
- one or more TAB (HT) or SPACE characters. It follows
- that an octet with value 9 or 32 appearing at the end
- of an encoded line must be represented according to
- Rule #1. This rule is necessary because some MTAs
- (Message Transport Agents, programs which transport
- messages from one user to another, or perform a part of
- such transfers) are known to pad lines of text with
- SPACEs, and others are known to remove "white space"
- characters from the end of a line. Therefore, when
- decoding a Quoted-Printable body, any trailing white
- space on a line must be deleted, as it will necessarily
- have been added by intermediate transport agents.
-
- Rule #4 (Line Breaks): A line break in a text body
- part, independent of what its representation is
- following the canonical representation of the data
- being encoded, must be represented by a (RFC 822) line
- break, which is a CRLF sequence, in the Quoted-
- Printable encoding. If isolated CRs and LFs, or LF CR
- and CR LF sequences are allowed to appear in binary
- data according to the canonical form, they must be
- represented using the "=0D", "=0A", "=0A=0D" and
- "=0D=0A" notations respectively.
-
- Note that many implementation may elect to encode the
- local representation of various content types directly.
- In particular, this may apply to plain text material on
- systems that use newline conventions other than CRLF
- delimiters. Such an implementation is permissible, but
- the generation of line breaks must be generalized to
- account for the case where alternate representations of
- newline sequences are used.
-
- Rule #5 (Soft Line Breaks): The Quoted-Printable
- encoding REQUIRES that encoded lines be no more than 76
- characters long. If longer lines are to be encoded with
- the Quoted-Printable encoding, 'soft' line breaks must
- be used. An equal sign as the last character on a
- encoded line indicates such a non-significant ('soft')
- line break in the encoded text. Thus if the "raw" form
- of the line is a single unencoded line that says:
-
- Now's the time for all folk to come to the aid of
- their country.
-
- This can be represented, in the Quoted-Printable
- encoding, as
-
-
-
-
-
- Borenstein & Freed [Page 15]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Now's the time =
- for all folk to come=
- to the aid of their country.
-
- This provides a mechanism with which long lines are
- encoded in such a way as to be restored by the user
- agent. The 76 character limit does not count the
- trailing CRLF, but counts all other characters,
- including any equal signs.
-
- Since the hyphen character ("-") is represented as itself in
- the Quoted-Printable encoding, care must be taken, when
- encapsulating a quoted-printable encoded body in a multipart
- entity, to ensure that the encapsulation boundary does not
- appear anywhere in the encoded body. (A good strategy is to
- choose a boundary that includes a character sequence such as
- "=_" which can never appear in a quoted-printable body. See
- the definition of multipart messages later in this
- document.)
-
- NOTE: The quoted-printable encoding represents something of
- a compromise between readability and reliability in
- transport. Bodies encoded with the quoted-printable
- encoding will work reliably over most mail gateways, but may
- not work perfectly over a few gateways, notably those
- involving translation into EBCDIC. (In theory, an EBCDIC
- gateway could decode a quoted-printable body and re-encode
- it using base64, but such gateways do not yet exist.) A
- higher level of confidence is offered by the base64
- Content-Transfer-Encoding. A way to get reasonably reliable
- transport through EBCDIC gateways is to also quote the ASCII
- characters
-
- !"#$@[\]^`{|}~
-
- according to rule #1. See Appendix B for more information.
-
- Because quoted-printable data is generally assumed to be
- line-oriented, it is to be expected that the breaks between
- the lines of quoted printable data may be altered in
- transport, in the same manner that plain text mail has
- always been altered in Internet mail when passing between
- systems with differing newline conventions. If such
- alterations are likely to constitute a corruption of the
- data, it is probably more sensible to use the base64
- encoding rather than the quoted-printable encoding.
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 16]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 5.2 Base64 Content-Transfer-Encoding
-
- The Base64 Content-Transfer-Encoding is designed to
- represent arbitrary sequences of octets in a form that is
- not humanly readable. The encoding and decoding algorithms
- are simple, but the encoded data are consistently only about
- 33 percent larger than the unencoded data. This encoding is
- based on the one used in Privacy Enhanced Mail applications,
- as defined in RFC 1113. The base64 encoding is adapted
- from RFC 1113, with one change: base64 eliminates the "*"
- mechanism for embedded clear text.
-
- A 65-character subset of US-ASCII is used, enabling 6 bits
- to be represented per printable character. (The extra 65th
- character, "=", is used to signify a special processing
- function.)
-
- NOTE: This subset has the important property that it is
- represented identically in all versions of ISO 646,
- including US ASCII, and all characters in the subset are
- also represented identically in all versions of EBCDIC.
- Other popular encodings, such as the encoding used by the
- UUENCODE utility and the base85 encoding specified as part
- of Level 2 PostScript, do not share these properties, and
- thus do not fulfill the portability requirements a binary
- transport encoding for mail must meet.
-
- The encoding process represents 24-bit groups of input bits
- as output strings of 4 encoded characters. Proceeding from
- left to right, a 24-bit input group is formed by
- concatenating 3 8-bit input groups. These 24 bits are then
- treated as 4 concatenated 6-bit groups, each of which is
- translated into a single digit in the base64 alphabet. When
- encoding a bit stream via the base64 encoding, the bit
- stream must be presumed to be ordered with the most-
- significant-bit first. That is, the first bit in the stream
- will be the high-order bit in the first byte, and the eighth
- bit will be the low-order bit in the first byte, and so on.
-
- Each 6-bit group is used as an index into an array of 64
- printable characters. The character referenced by the index
- is placed in the output string. These characters, identified
- in Table 1, below, are selected so as to be universally
- representable, and the set excludes characters with
- particular significance to SMTP (e.g., ".", "CR", "LF") and
- to the encapsulation boundaries defined in this document
- (e.g., "-").
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 17]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Table 1: The Base64 Alphabet
-
- Value Encoding Value Encoding Value Encoding Value
- Encoding
- 0 A 17 R 34 i 51 z
- 1 B 18 S 35 j 52 0
- 2 C 19 T 36 k 53 1
- 3 D 20 U 37 l 54 2
- 4 E 21 V 38 m 55 3
- 5 F 22 W 39 n 56 4
- 6 G 23 X 40 o 57 5
- 7 H 24 Y 41 p 58 6
- 8 I 25 Z 42 q 59 7
- 9 J 26 a 43 r 60 8
- 10 K 27 b 44 s 61 9
- 11 L 28 c 45 t 62 +
- 12 M 29 d 46 u 63 /
- 13 N 30 e 47 v
- 14 O 31 f 48 w (pad) =
- 15 P 32 g 49 x
- 16 Q 33 h 50 y
-
- The output stream (encoded bytes) must be represented in
- lines of no more than 76 characters each. All line breaks
- or other characters not found in Table 1 must be ignored by
- decoding software. In base64 data, characters other than
- those in Table 1, line breaks, and other white space
- probably indicate a transmission error, about which a
- warning message or even a message rejection might be
- appropriate under some circumstances.
-
- Special processing is performed if fewer than 24 bits are
- available at the end of the data being encoded. A full
- encoding quantum is always completed at the end of a body.
- When fewer than 24 input bits are available in an input
- group, zero bits are added (on the right) to form an
- integral number of 6-bit groups. Output character positions
- which are not required to represent actual input data are
- set to the character "=". Since all base64 input is an
- integral number of octets, only the following cases can
- arise: (1) the final quantum of encoding input is an
- integral multiple of 24 bits; here, the final unit of
- encoded output will be an integral multiple of 4 characters
- with no "=" padding, (2) the final quantum of encoding input
- is exactly 8 bits; here, the final unit of encoded output
- will be two characters followed by two "=" padding
- characters, or (3) the final quantum of encoding input is
- exactly 16 bits; here, the final unit of encoded output will
- be three characters followed by one "=" padding character.
-
- Care must be taken to use the proper octets for line breaks
- if base64 encoding is applied directly to text material that
- has not been converted to canonical form. In particular,
- text line breaks should be converted into CRLF sequences
-
-
-
- Borenstein & Freed [Page 18]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- prior to base64 encoding. The important thing to note is
- that this may be done directly by the encoder rather than in
- a prior canonicalization step in some implementations.
-
- NOTE: There is no need to worry about quoting apparent
- encapsulation boundaries within base64-encoded parts of
- multipart entities because no hyphen characters are used in
- the base64 encoding.
-
- 6 Additional Optional Content- Header Fields
-
- 6.1 Optional Content-ID Header Field
-
- In constructing a high-level user agent, it may be desirable
- to allow one body to make reference to another.
- Accordingly, bodies may be labeled using the "Content-ID"
- header field, which is syntactically identical to the
- "Message-ID" header field:
-
- Content-ID := msg-id
-
- Like the Message-ID values, Content-ID values must be
- generated to be as unique as possible.
-
- 6.2 Optional Content-Description Header Field
-
- The ability to associate some descriptive information with a
- given body is often desirable. For example, it may be useful
- to mark an "image" body as "a picture of the Space Shuttle
- Endeavor." Such text may be placed in the Content-
- Description header field.
-
- Content-Description := *text
-
- The description is presumed to be given in the US-ASCII
- character set, although the mechanism specified in [RFC-
- 1342] may be used for non-US-ASCII Content-Description
- values.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 19]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7 The Predefined Content-Type Values
-
- This document defines seven initial Content-Type values and
- an extension mechanism for private or experimental types.
- Further standard types must be defined by new published
- specifications. It is expected that most innovation in new
- types of mail will take place as subtypes of the seven types
- defined here. The most essential characteristics of the
- seven content-types are summarized in Appendix G.
-
- 7.1 The Text Content-Type
-
- The text Content-Type is intended for sending material which
- is principally textual in form. It is the default Content-
- Type. A "charset" parameter may be used to indicate the
- character set of the body text. The primary subtype of text
- is "plain". This indicates plain (unformatted) text. The
- default Content-Type for Internet mail is "text/plain;
- charset=us-ascii".
-
- Beyond plain text, there are many formats for representing
- what might be known as "extended text" -- text with embedded
- formatting and presentation information. An interesting
- characteristic of many such representations is that they are
- to some extent readable even without the software that
- interprets them. It is useful, then, to distinguish them,
- at the highest level, from such unreadable data as images,
- audio, or text represented in an unreadable form. In the
- absence of appropriate interpretation software, it is
- reasonable to show subtypes of text to the user, while it is
- not reasonable to do so with most nontextual data.
-
- Such formatted textual data should be represented using
- subtypes of text. Plausible subtypes of text are typically
- given by the common name of the representation format, e.g.,
- "text/richtext".
-
- 7.1.1 The charset parameter
-
- A critical parameter that may be specified in the Content-
- Type field for text data is the character set. This is
- specified with a "charset" parameter, as in:
-
- Content-type: text/plain; charset=us-ascii
-
- Unlike some other parameter values, the values of the
- charset parameter are NOT case sensitive. The default
- character set, which must be assumed in the absence of a
- charset parameter, is US-ASCII.
-
- An initial list of predefined character set names can be
- found at the end of this section. Additional character sets
- may be registered with IANA as described in Appendix F,
- although the standardization of their use requires the usual
-
-
-
- Borenstein & Freed [Page 20]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- IAB review and approval. Note that if the specified
- character set includes 8-bit data, a Content-Transfer-
- Encoding header field and a corresponding encoding on the
- data are required in order to transmit the body via some
- mail transfer protocols, such as SMTP.
-
- The default character set, US-ASCII, has been the subject of
- some confusion and ambiguity in the past. Not only were
- there some ambiguities in the definition, there have been
- wide variations in practice. In order to eliminate such
- ambiguity and variations in the future, it is strongly
- recommended that new user agents explicitly specify a
- character set via the Content-Type header field. "US-ASCII"
- does not indicate an arbitrary seven-bit character code, but
- specifies that the body uses character coding that uses the
- exact correspondence of codes to characters specified in
- ASCII. National use variations of ISO 646 [ISO-646] are NOT
- ASCII and their use in Internet mail is explicitly
- discouraged. The omission of the ISO 646 character set is
- deliberate in this regard. The character set name of "US-
- ASCII" explicitly refers to ANSI X3.4-1986 [US-ASCII] only.
- The character set name "ASCII" is reserved and must not be
- used for any purpose.
-
- NOTE: RFC 821 explicitly specifies "ASCII", and references
- an earlier version of the American Standard. Insofar as one
- of the purposes of specifying a Content-Type and character
- set is to permit the receiver to unambiguously determine how
- the sender intended the coded message to be interpreted,
- assuming anything other than "strict ASCII" as the default
- would risk unintentional and incompatible changes to the
- semantics of messages now being transmitted. This also
- implies that messages containing characters coded according
- to national variations on ISO 646, or using code-switching
- procedures (e.g., those of ISO 2022), as well as 8-bit or
- multiple octet character encodings MUST use an appropriate
- character set specification to be consistent with this
- specification.
-
- The complete US-ASCII character set is listed in [US-ASCII].
- Note that the control characters including DEL (0-31, 127)
- have no defined meaning apart from the combination CRLF
- (ASCII values 13 and 10) indicating a new line. Two of the
- characters have de facto meanings in wide use: FF (12) often
- means "start subsequent text on the beginning of a new
- page"; and TAB or HT (9) often (though not always) means
- "move the cursor to the next available column after the
- current position where the column number is a multiple of 8
- (counting the first column as column 0)." Apart from this,
- any use of the control characters or DEL in a body must be
- part of a private agreement between the sender and
- recipient. Such private agreements are discouraged and
- should be replaced by the other capabilities of this
- document.
-
-
-
- Borenstein & Freed [Page 21]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- NOTE: Beyond US-ASCII, an enormous proliferation of
- character sets is possible. It is the opinion of the IETF
- working group that a large number of character sets is NOT a
- good thing. We would prefer to specify a single character
- set that can be used universally for representing all of the
- world's languages in electronic mail. Unfortunately,
- existing practice in several communities seems to point to
- the continued use of multiple character sets in the near
- future. For this reason, we define names for a small number
- of character sets for which a strong constituent base
- exists. It is our hope that ISO 10646 or some other
- effort will eventually define a single world character set
- which can then be specified for use in Internet mail, but in
- the advance of that definition we cannot specify the use of
- ISO 10646, Unicode, or any other character set whose
- definition is, as of this writing, incomplete.
-
- The defined charset values are:
-
- US-ASCII -- as defined in [US-ASCII].
-
- ISO-8859-X -- where "X" is to be replaced, as
- necessary, for the parts of ISO-8859 [ISO-
- 8859]. Note that the ISO 646 character sets
- have deliberately been omitted in favor of
- their 8859 replacements, which are the
- designated character sets for Internet mail.
- As of the publication of this document, the
- legitimate values for "X" are the digits 1
- through 9.
-
- Note that the character set used, if anything other than
- US-ASCII, must always be explicitly specified in the
- Content-Type field.
-
- No other character set name may be used in Internet mail
- without the publication of a formal specification and its
- registration with IANA as described in Appendix F, or by
- private agreement, in which case the character set name must
- begin with "X-".
-
- Implementors are discouraged from defining new character
- sets for mail use unless absolutely necessary.
-
- The "charset" parameter has been defined primarily for the
- purpose of textual data, and is described in this section
- for that reason. However, it is conceivable that non-
- textual data might also wish to specify a charset value for
- some purpose, in which case the same syntax and values
- should be used.
-
- In general, mail-sending software should always use the
- "lowest common denominator" character set possible. For
- example, if a body contains only US-ASCII characters, it
-
-
-
- Borenstein & Freed [Page 22]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- should be marked as being in the US-ASCII character set, not
- ISO-8859-1, which, like all the ISO-8859 family of character
- sets, is a superset of US-ASCII. More generally, if a
- widely-used character set is a subset of another character
- set, and a body contains only characters in the widely-used
- subset, it should be labeled as being in that subset. This
- will increase the chances that the recipient will be able to
- view the mail correctly.
-
- 7.1.2 The Text/plain subtype
-
- The primary subtype of text is "plain". This indicates
- plain (unformatted) text. The default Content-Type for
- Internet mail, "text/plain; charset=us-ascii", describes
- existing Internet practice, that is, it is the type of body
- defined by RFC 822.
-
- 7.1.3 The Text/richtext subtype
-
- In order to promote the wider interoperability of simple
- formatted text, this document defines an extremely simple
- subtype of "text", the "richtext" subtype. This subtype was
- designed to meet the following criteria:
-
- 1. The syntax must be extremely simple to parse,
- so that even teletype-oriented mail systems can
- easily strip away the formatting information and
- leave only the readable text.
-
- 2. The syntax must be extensible to allow for new
- formatting commands that are deemed essential.
-
- 3. The capabilities must be extremely limited, to
- ensure that it can represent no more than is
- likely to be representable by the user's primary
- word processor. While this limits what can be
- sent, it increases the likelihood that what is
- sent can be properly displayed.
-
- 4. The syntax must be compatible with SGML, so
- that, with an appropriate DTD (Document Type
- Definition, the standard mechanism for defining a
- document type using SGML), a general SGML parser
- could be made to parse richtext. However, despite
- this compatibility, the syntax should be far
- simpler than full SGML, so that no SGML knowledge
- is required in order to implement it.
-
- The syntax of "richtext" is very simple. It is assumed, at
- the top-level, to be in the US-ASCII character set, unless
- of course a different charset parameter was specified in the
- Content-type field. All characters represent themselves,
- with the exception of the "<" character (ASCII 60), which is
- used to mark the beginning of a formatting command.
-
-
-
- Borenstein & Freed [Page 23]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Formatting instructions consist of formatting commands
- surrounded by angle brackets ("<>", ASCII 60 and 62). Each
- formatting command may be no more than 40 characters in
- length, all in US-ASCII, restricted to the alphanumeric and
- hyphen ("-") characters. Formatting commands may be preceded
- by a forward slash or solidus ("/", ASCII 47), making them
- negations, and such negations must always exist to balance
- the initial opening commands, except as noted below. Thus,
- if the formatting command "<bold>" appears at some point,
- there must later be a "</bold>" to balance it. There are
- only three exceptions to this "balancing" rule: First, the
- command "<lt>" is used to represent a literal "<" character.
- Second, the command "<nl>" is used to represent a required
- line break. (Otherwise, CRLFs in the data are treated as
- equivalent to a single SPACE character.) Finally, the
- command "<np>" is used to represent a page break. (NOTE:
- The 40 character limit on formatting commands does not
- include the "<", ">", or "/" characters that might be
- attached to such commands.)
-
- Initially defined formatting commands, not all of which will
- be implemented by all richtext implementations, include:
-
- Bold -- causes the subsequent text to be in a bold
- font.
- Italic -- causes the subsequent text to be in an italic
- font.
- Fixed -- causes the subsequent text to be in a fixed
- width font.
- Smaller -- causes the subsequent text to be in a
- smaller font.
- Bigger -- causes the subsequent text to be in a bigger
- font.
- Underline -- causes the subsequent text to be
- underlined.
- Center -- causes the subsequent text to be centered.
- FlushLeft -- causes the subsequent text to be left
- justified.
- FlushRight -- causes the subsequent text to be right
- justified.
- Indent -- causes the subsequent text to be indented at
- the left margin.
- IndentRight -- causes the subsequent text to be
- indented at the right margin.
- Outdent -- causes the subsequent text to be outdented
- at the left margin.
- OutdentRight -- causes the subsequent text to be
- outdented at the right margin.
- SamePage -- causes the subsequent text to be grouped,
- if possible, on one page.
- Subscript -- causes the subsequent text to be
- interpreted as a subscript.
-
-
-
-
-
- Borenstein & Freed [Page 24]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Superscript -- causes the subsequent text to be
- interpreted as a superscript.
- Heading -- causes the subsequent text to be interpreted
- as a page heading.
- Footing -- causes the subsequent text to be interpreted
- as a page footing.
- ISO-8859-X (for any value of X that is legal as a
- "charset" parameter) -- causes the subsequent text
- to be interpreted as text in the appropriate
- character set.
- US-ASCII -- causes the subsequent text to be
- interpreted as text in the US-ASCII character set.
- Excerpt -- causes the subsequent text to be interpreted
- as a textual excerpt from another source.
- Typically this will be displayed using indentation
- and an alternate font, but such decisions are up
- to the viewer.
- Paragraph -- causes the subsequent text to be
- interpreted as a single paragraph, with
- appropriate paragraph breaks (typically blank
- space) before and after.
- Signature -- causes the subsequent text to be
- interpreted as a "signature". Some systems may
- wish to display signatures in a smaller font or
- otherwise set them apart from the main text of the
- message.
- Comment -- causes the subsequent text to be interpreted
- as a comment, and hence not shown to the reader.
- No-op -- has no effect on the subsequent text.
- lt -- <lt> is replaced by a literal "<" character. No
- balancing </lt> is allowed.
- nl -- <nl> causes a line break. No balancing </nl> is
- allowed.
- np -- <np> causes a page break. No balancing </np> is
- allowed.
-
- Each positive formatting command affects all subsequent text
- until the matching negative formatting command. Such pairs
- of formatting commands must be properly balanced and nested.
- Thus, a proper way to describe text in bold italics is:
-
- <bold><italic>the-text</italic></bold>
-
- or, alternately,
-
- <italic><bold>the-text</bold></italic>
-
- but, in particular, the following is illegal
- richtext:
-
- <bold><italic>the-text</bold></italic>
-
- NOTE: The nesting requirement for formatting commands
- imposes a slightly higher burden upon the composers of
-
-
-
- Borenstein & Freed [Page 25]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- richtext bodies, but potentially simplifies richtext
- displayers by allowing them to be stack-based. The main
- goal of richtext is to be simple enough to make multifont,
- formatted email widely readable, so that those with the
- capability of sending it will be able to do so with
- confidence. Thus slightly increased complexity in the
- composing software was deemed a reasonable tradeoff for
- simplified reading software. Nonetheless, implementors of
- richtext readers are encouraged to follow the general
- Internet guidelines of being conservative in what you send
- and liberal in what you accept. Those implementations that
- can do so are encouraged to deal reasonably with improperly
- nested richtext.
-
- Implementations must regard any unrecognized formatting
- command as equivalent to "No-op", thus facilitating future
- extensions to "richtext". Private extensions may be defined
- using formatting commands that begin with "X-", by analogy
- to Internet mail header field names.
-
- It is worth noting that no special behavior is required for
- the TAB (HT) character. It is recommended, however, that, at
- least when fixed-width fonts are in use, the common
- semantics of the TAB (HT) character should be observed,
- namely that it moves to the next column position that is a
- multiple of 8. (In other words, if a TAB (HT) occurs in
- column n, where the leftmost column is column 0, then that
- TAB (HT) should be replaced by 8-(n mod 8) SPACE
- characters.)
-
- Richtext also differentiates between "hard" and "soft" line
- breaks. A line break (CRLF) in the richtext data stream is
- interpreted as a "soft" line break, one that is included
- only for purposes of mail transport, and is to be treated as
- white space by richtext interpreters. To include a "hard"
- line break (one that must be displayed as such), the "<nl>"
- or "<paragraph> formatting constructs should be used. In
- general, a soft line break should be treated as white space,
- but when soft line breaks immediately follow a <nl> or a
- </paragraph> tag they should be ignored rather than treated
- as white space.
-
- Putting all this together, the following "text/richtext"
- body fragment:
-
- <bold>Now</bold> is the time for
- <italic>all</italic> good men
- <smaller>(and <lt>women>)</smaller> to
- <ignoreme></ignoreme> come
-
- to the aid of their
- <nl>
-
-
-
-
-
- Borenstein & Freed [Page 26]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- beloved <nl><nl>country. <comment> Stupid
- quote! </comment> -- the end
-
- represents the following formatted text (which will, no
- doubt, look cryptic in the text-only version of this
- document):
-
- Now is the time for all good men (and <women>) to
- come to the aid of their
- beloved
-
- country. -- the end
-
- Richtext conformance: A minimal richtext implementation is
- one that simply converts "<lt>" to "<", converts CRLFs to
- SPACE, converts <nl> to a newline according to local newline
- convention, removes everything between a <comment> command
- and the next balancing </comment> command, and removes all
- other formatting commands (all text enclosed in angle
- brackets).
-
- NOTE ON THE RELATIONSHIP OF RICHTEXT TO SGML: Richtext is
- decidedly not SGML, and must not be used to transport
- arbitrary SGML documents. Those who wish to use SGML
- document types as a mail transport format must define a new
- text or application subtype, e.g., "text/sgml-dtd-whatever"
- or "application/sgml-dtd-whatever", depending on the
- perceived readability of the DTD in use. Richtext is
- designed to be compatible with SGML, and specifically so
- that it will be possible to define a richtext DTD if one is
- needed. However, this does not imply that arbitrary SGML
- can be called richtext, nor that richtext implementors have
- any need to understand SGML; the description in this
- document is a complete definition of richtext, which is far
- simpler than complete SGML.
-
- NOTE ON THE INTENDED USE OF RICHTEXT: It is recognized that
- implementors of future mail systems will want rich text
- functionality far beyond that currently defined for
- richtext. The intent of richtext is to provide a common
- format for expressing that functionality in a form in which
- much of it, at least, will be understood by interoperating
- software. Thus, in particular, software with a richer
- notion of formatted text than richtext can still use
- richtext as its basic representation, but can extend it with
- new formatting commands and by hiding information specific
- to that software system in richtext comments. As such
- systems evolve, it is expected that the definition of
- richtext will be further refined by future published
- specifications, but richtext as defined here provides a
- platform on which evolutionary refinements can be based.
-
- IMPLEMENTATION NOTE: In some environments, it might be
- impossible to combine certain richtext formatting commands,
-
-
-
- Borenstein & Freed [Page 27]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- whereas in others they might be combined easily. For
- example, the combination of <bold> and <italic> might
- produce bold italics on systems that support such fonts, but
- there exist systems that can make text bold or italicized,
- but not both. In such cases, the most recently issued
- recognized formatting command should be preferred.
-
- One of the major goals in the design of richtext was to make
- it so simple that even text-only mailers will implement
- richtext-to-plain-text translators, thus increasing the
- likelihood that multifont text will become "safe" to use
- very widely. To demonstrate this simplicity, an extremely
- simple 35-line C program that converts richtext input into
- plain text output is included in Appendix D.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 28]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.2 The Multipart Content-Type
-
- In the case of multiple part messages, in which one or more
- different sets of data are combined in a single body, a
- "multipart" Content-Type field must appear in the entity's
- header. The body must then contain one or more "body parts,"
- each preceded by an encapsulation boundary, and the last one
- followed by a closing boundary. Each part starts with an
- encapsulation boundary, and then contains a body part
- consisting of header area, a blank line, and a body area.
- Thus a body part is similar to an RFC 822 message in syntax,
- but different in meaning.
-
- A body part is NOT to be interpreted as actually being an
- RFC 822 message. To begin with, NO header fields are
- actually required in body parts. A body part that starts
- with a blank line, therefore, is allowed and is a body part
- for which all default values are to be assumed. In such a
- case, the absence of a Content-Type header field implies
- that the encapsulation is plain US-ASCII text. The only
- header fields that have defined meaning for body parts are
- those the names of which begin with "Content-". All other
- header fields are generally to be ignored in body parts.
- Although they should generally be retained in mail
- processing, they may be discarded by gateways if necessary.
- Such other fields are permitted to appear in body parts but
- should not be depended on. "X-" fields may be created for
- experimental or private purposes, with the recognition that
- the information they contain may be lost at some gateways.
-
- The distinction between an RFC 822 message and a body part
- is subtle, but important. A gateway between Internet and
- X.400 mail, for example, must be able to tell the difference
- between a body part that contains an image and a body part
- that contains an encapsulated message, the body of which is
- an image. In order to represent the latter, the body part
- must have "Content-Type: message", and its body (after the
- blank line) must be the encapsulated message, with its own
- "Content-Type: image" header field. The use of similar
- syntax facilitates the conversion of messages to body parts,
- and vice versa, but the distinction between the two must be
- understood by implementors. (For the special case in which
- all parts actually are messages, a "digest" subtype is also
- defined.)
-
- As stated previously, each body part is preceded by an
- encapsulation boundary. The encapsulation boundary MUST NOT
- appear inside any of the encapsulated parts. Thus, it is
- crucial that the composing agent be able to choose and
- specify the unique boundary that will separate the parts.
-
- All present and future subtypes of the "multipart" type must
- use an identical syntax. Subtypes may differ in their
- semantics, and may impose additional restrictions on syntax,
-
-
-
- Borenstein & Freed [Page 29]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- but must conform to the required syntax for the multipart
- type. This requirement ensures that all conformant user
- agents will at least be able to recognize and separate the
- parts of any multipart entity, even of an unrecognized
- subtype.
-
- As stated in the definition of the Content-Transfer-Encoding
- field, no encoding other than "7bit", "8bit", or "binary" is
- permitted for entities of type "multipart". The multipart
- delimiters and header fields are always 7-bit ASCII in any
- case, and data within the body parts can be encoded on a
- part-by-part basis, with Content-Transfer-Encoding fields
- for each appropriate body part.
-
- Mail gateways, relays, and other mail handling agents are
- commonly known to alter the top-level header of an RFC 822
- message. In particular, they frequently add, remove, or
- reorder header fields. Such alterations are explicitly
- forbidden for the body part headers embedded in the bodies
- of messages of type "multipart."
-
- 7.2.1 Multipart: The common syntax
-
- All subtypes of "multipart" share a common syntax, defined
- in this section. A simple example of a multipart message
- also appears in this section. An example of a more complex
- multipart message is given in Appendix C.
-
- The Content-Type field for multipart entities requires one
- parameter, "boundary", which is used to specify the
- encapsulation boundary. The encapsulation boundary is
- defined as a line consisting entirely of two hyphen
- characters ("-", decimal code 45) followed by the boundary
- parameter value from the Content-Type header field.
-
- NOTE: The hyphens are for rough compatibility with the
- earlier RFC 934 method of message encapsulation, and for
- ease of searching for the boundaries in some
- implementations. However, it should be noted that multipart
- messages are NOT completely compatible with RFC 934
- encapsulations; in particular, they do not obey RFC 934
- quoting conventions for embedded lines that begin with
- hyphens. This mechanism was chosen over the RFC 934
- mechanism because the latter causes lines to grow with each
- level of quoting. The combination of this growth with the
- fact that SMTP implementations sometimes wrap long lines
- made the RFC 934 mechanism unsuitable for use in the event
- that deeply-nested multipart structuring is ever desired.
-
- Thus, a typical multipart Content-Type header field might
- look like this:
-
- Content-Type: multipart/mixed;
-
-
-
-
- Borenstein & Freed [Page 30]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- boundary=gc0p4Jq0M2Yt08jU534c0p
-
- This indicates that the entity consists of several parts,
- each itself with a structure that is syntactically identical
- to an RFC 822 message, except that the header area might be
- completely empty, and that the parts are each preceded by
- the line
-
- --gc0p4Jq0M2Yt08jU534c0p
-
- Note that the encapsulation boundary must occur at the
- beginning of a line, i.e., following a CRLF, and that that
- initial CRLF is considered to be part of the encapsulation
- boundary rather than part of the preceding part. The
- boundary must be followed immediately either by another CRLF
- and the header fields for the next part, or by two CRLFs, in
- which case there are no header fields for the next part (and
- it is therefore assumed to be of Content-Type text/plain).
-
- NOTE: The CRLF preceding the encapsulation line is
- considered part of the boundary so that it is possible to
- have a part that does not end with a CRLF (line break).
- Body parts that must be considered to end with line breaks,
- therefore, should have two CRLFs preceding the encapsulation
- line, the first of which is part of the preceding body part,
- and the second of which is part of the encapsulation
- boundary.
-
- The requirement that the encapsulation boundary begins with
- a CRLF implies that the body of a multipart entity must
- itself begin with a CRLF before the first encapsulation line
- -- that is, if the "preamble" area is not used, the entity
- headers must be followed by TWO CRLFs. This is indeed how
- such entities should be composed. A tolerant mail reading
- program, however, may interpret a body of type multipart
- that begins with an encapsulation line NOT initiated by a
- CRLF as also being an encapsulation boundary, but a
- compliant mail sending program must not generate such
- entities.
-
- Encapsulation boundaries must not appear within the
- encapsulations, and must be no longer than 70 characters,
- not counting the two leading hyphens.
-
- The encapsulation boundary following the last body part is a
- distinguished delimiter that indicates that no further body
- parts will follow. Such a delimiter is identical to the
- previous delimiters, with the addition of two more hyphens
- at the end of the line:
-
- --gc0p4Jq0M2Yt08jU534c0p--
-
- There appears to be room for additional information prior to
- the first encapsulation boundary and following the final
-
-
-
- Borenstein & Freed [Page 31]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- boundary. These areas should generally be left blank, and
- implementations should ignore anything that appears before
- the first boundary or after the last one.
-
- NOTE: These "preamble" and "epilogue" areas are not used
- because of the lack of proper typing of these parts and the
- lack of clear semantics for handling these areas at
- gateways, particularly X.400 gateways.
-
- NOTE: Because encapsulation boundaries must not appear in
- the body parts being encapsulated, a user agent must
- exercise care to choose a unique boundary. The boundary in
- the example above could have been the result of an algorithm
- designed to produce boundaries with a very low probability
- of already existing in the data to be encapsulated without
- having to prescan the data. Alternate algorithms might
- result in more 'readable' boundaries for a recipient with an
- old user agent, but would require more attention to the
- possibility that the boundary might appear in the
- encapsulated part. The simplest boundary possible is
- something like "---", with a closing boundary of "-----".
-
- As a very simple example, the following multipart message
- has two parts, both of them plain text, one of them
- explicitly typed and one of them implicitly typed:
-
- From: Nathaniel Borenstein <nsb@bellcore.com>
- To: Ned Freed <ned@innosoft.com>
- Subject: Sample message
- MIME-Version: 1.0
- Content-type: multipart/mixed; boundary="simple
- boundary"
-
- This is the preamble. It is to be ignored, though it
- is a handy place for mail composers to include an
- explanatory note to non-MIME compliant readers.
- --simple boundary
-
- This is implicitly typed plain ASCII text.
- It does NOT end with a linebreak.
- --simple boundary
- Content-type: text/plain; charset=us-ascii
-
- This is explicitly typed plain ASCII text.
- It DOES end with a linebreak.
-
- --simple boundary--
- This is the epilogue. It is also to be ignored.
-
- The use of a Content-Type of multipart in a body part within
- another multipart entity is explicitly allowed. In such
- cases, for obvious reasons, care must be taken to ensure
- that each nested multipart entity must use a different
- boundary delimiter. See Appendix C for an example of nested
-
-
-
- Borenstein & Freed [Page 32]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- multipart entities.
-
- The use of the multipart Content-Type with only a single
- body part may be useful in certain contexts, and is
- explicitly permitted.
-
- The only mandatory parameter for the multipart Content-Type
- is the boundary parameter, which consists of 1 to 70
- characters from a set of characters known to be very robust
- through email gateways, and NOT ending with white space.
- (If a boundary appears to end with white space, the white
- space must be presumed to have been added by a gateway, and
- should be deleted.) It is formally specified by the
- following BNF:
-
- boundary := 0*69<bchars> bcharsnospace
-
- bchars := bcharsnospace / " "
-
- bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /
- "_"
- / "," / "-" / "." / "/" / ":" / "=" / "?"
-
- Overall, the body of a multipart entity may be specified as
- follows:
-
- multipart-body := preamble 1*encapsulation
- close-delimiter epilogue
-
- encapsulation := delimiter CRLF body-part
-
- delimiter := CRLF "--" boundary ; taken from Content-Type
- field.
- ; when content-type is
- multipart
- ; There must be no space
- ; between "--" and boundary.
-
- close-delimiter := delimiter "--" ; Again, no space before
- "--"
-
- preamble := *text ; to be ignored upon
- receipt.
-
- epilogue := *text ; to be ignored upon
- receipt.
-
- body-part = <"message" as defined in RFC 822,
- with all header fields optional, and with the
- specified delimiter not occurring anywhere in
- the message body, either on a line by itself
- or as a substring anywhere. Note that the
-
-
-
-
-
- Borenstein & Freed [Page 33]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- semantics of a part differ from the semantics
- of a message, as described in the text.>
-
- NOTE: Conspicuously missing from the multipart type is a
- notion of structured, related body parts. In general, it
- seems premature to try to standardize interpart structure
- yet. It is recommended that those wishing to provide a more
- structured or integrated multipart messaging facility should
- define a subtype of multipart that is syntactically
- identical, but that always expects the inclusion of a
- distinguished part that can be used to specify the structure
- and integration of the other parts, probably referring to
- them by their Content-ID field. If this approach is used,
- other implementations will not recognize the new subtype,
- but will treat it as the primary subtype (multipart/mixed)
- and will thus be able to show the user the parts that are
- recognized.
-
- 7.2.2 The Multipart/mixed (primary) subtype
-
- The primary subtype for multipart, "mixed", is intended for
- use when the body parts are independent and intended to be
- displayed serially. Any multipart subtypes that an
- implementation does not recognize should be treated as being
- of subtype "mixed".
-
- 7.2.3 The Multipart/alternative subtype
-
- The multipart/alternative type is syntactically identical to
- multipart/mixed, but the semantics are different. In
- particular, each of the parts is an "alternative" version of
- the same information. User agents should recognize that the
- content of the various parts are interchangeable. The user
- agent should either choose the "best" type based on the
- user's environment and preferences, or offer the user the
- available alternatives. In general, choosing the best type
- means displaying only the LAST part that can be displayed.
- This may be used, for example, to send mail in a fancy text
- format in such a way that it can easily be displayed
- anywhere:
-
- From: Nathaniel Borenstein <nsb@bellcore.com>
- To: Ned Freed <ned@innosoft.com>
- Subject: Formatted text mail
- MIME-Version: 1.0
- Content-Type: multipart/alternative; boundary=boundary42
-
-
- --boundary42
- Content-Type: text/plain; charset=us-ascii
-
- ...plain text version of message goes here....
-
-
-
-
-
- Borenstein & Freed [Page 34]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- --boundary42
- Content-Type: text/richtext
-
- .... richtext version of same message goes here ...
- --boundary42
- Content-Type: text/x-whatever
-
- .... fanciest formatted version of same message goes here
- ...
- --boundary42--
-
- In this example, users whose mail system understood the
- "text/x-whatever" format would see only the fancy version,
- while other users would see only the richtext or plain text
- version, depending on the capabilities of their system.
-
- In general, user agents that compose multipart/alternative
- entities should place the body parts in increasing order of
- preference, that is, with the preferred format last. For
- fancy text, the sending user agent should put the plainest
- format first and the richest format last. Receiving user
- agents should pick and display the last format they are
- capable of displaying. In the case where one of the
- alternatives is itself of type "multipart" and contains
- unrecognized sub-parts, the user agent may choose either to
- show that alternative, an earlier alternative, or both.
-
- NOTE: From an implementor's perspective, it might seem more
- sensible to reverse this ordering, and have the plainest
- alternative last. However, placing the plainest alternative
- first is the friendliest possible option when
- mutlipart/alternative entities are viewed using a non-MIME-
- compliant mail reader. While this approach does impose some
- burden on compliant mail readers, interoperability with
- older mail readers was deemed to be more important in this
- case.
-
- It may be the case that some user agents, if they can
- recognize more than one of the formats, will prefer to offer
- the user the choice of which format to view. This makes
- sense, for example, if mail includes both a nicely-formatted
- image version and an easily-edited text version. What is
- most critical, however, is that the user not automatically
- be shown multiple versions of the same data. Either the
- user should be shown the last recognized version or should
- explicitly be given the choice.
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 35]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.2.4 The Multipart/digest subtype
-
- This document defines a "digest" subtype of the multipart
- Content-Type. This type is syntactically identical to
- multipart/mixed, but the semantics are different. In
- particular, in a digest, the default Content-Type value for
- a body part is changed from "text/plain" to
- "message/rfc822". This is done to allow a more readable
- digest format that is largely compatible (except for the
- quoting convention) with RFC 934.
-
- A digest in this format might, then, look something like
- this:
-
- From: Moderator-Address
- MIME-Version: 1.0
- Subject: Internet Digest, volume 42
- Content-Type: multipart/digest;
- boundary="---- next message ----"
-
-
- ------ next message ----
-
- From: someone-else
- Subject: my opinion
-
- ...body goes here ...
-
- ------ next message ----
-
- From: someone-else-again
- Subject: my different opinion
-
- ... another body goes here...
-
- ------ next message ------
-
- 7.2.5 The Multipart/parallel subtype
-
- This document defines a "parallel" subtype of the multipart
- Content-Type. This type is syntactically identical to
- multipart/mixed, but the semantics are different. In
- particular, in a parallel entity, all of the parts are
- intended to be presented in parallel, i.e., simultaneously,
- on hardware and software that are capable of doing so.
- Composing agents should be aware that many mail readers will
- lack this capability and will show the parts serially in any
- event.
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 36]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.3 The Message Content-Type
-
- It is frequently desirable, in sending mail, to encapsulate
- another mail message. For this common operation, a special
- Content-Type, "message", is defined. The primary subtype,
- message/rfc822, has no required parameters in the Content-
- Type field. Additional subtypes, "partial" and "External-
- body", do have required parameters. These subtypes are
- explained below.
-
- NOTE: It has been suggested that subtypes of message might
- be defined for forwarded or rejected messages. However,
- forwarded and rejected messages can be handled as multipart
- messages in which the first part contains any control or
- descriptive information, and a second part, of type
- message/rfc822, is the forwarded or rejected message.
- Composing rejection and forwarding messages in this manner
- will preserve the type information on the original message
- and allow it to be correctly presented to the recipient, and
- hence is strongly encouraged.
-
- As stated in the definition of the Content-Transfer-Encoding
- field, no encoding other than "7bit", "8bit", or "binary" is
- permitted for messages or parts of type "message". The
- message header fields are always US-ASCII in any case, and
- data within the body can still be encoded, in which case the
- Content-Transfer-Encoding header field in the encapsulated
- message will reflect this. Non-ASCII text in the headers of
- an encapsulated message can be specified using the
- mechanisms described in [RFC-1342].
-
- Mail gateways, relays, and other mail handling agents are
- commonly known to alter the top-level header of an RFC 822
- message. In particular, they frequently add, remove, or
- reorder header fields. Such alterations are explicitly
- forbidden for the encapsulated headers embedded in the
- bodies of messages of type "message."
-
- 7.3.1 The Message/rfc822 (primary) subtype
-
- A Content-Type of "message/rfc822" indicates that the body
- contains an encapsulated message, with the syntax of an RFC
- 822 message.
-
- 7.3.2 The Message/Partial subtype
-
- A subtype of message, "partial", is defined in order to
- allow large objects to be delivered as several separate
- pieces of mail and automatically reassembled by the
- receiving user agent. (The concept is similar to IP
- fragmentation/reassembly in the basic Internet Protocols.)
- This mechanism can be used when intermediate transport
- agents limit the size of individual messages that can be
- sent. Content-Type "message/partial" thus indicates that
-
-
-
- Borenstein & Freed [Page 37]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- the body contains a fragment of a larger message.
-
- Three parameters must be specified in the Content-Type field
- of type message/partial: The first, "id", is a unique
- identifier, as close to a world-unique identifier as
- possible, to be used to match the parts together. (In
- general, the identifier is essentially a message-id; if
- placed in double quotes, it can be any message-id, in
- accordance with the BNF for "parameter" given earlier in
- this specification.) The second, "number", an integer, is
- the part number, which indicates where this part fits into
- the sequence of fragments. The third, "total", another
- integer, is the total number of parts. This third subfield
- is required on the final part, and is optional on the
- earlier parts. Note also that these parameters may be given
- in any order.
-
- Thus, part 2 of a 3-part message may have either of the
- following header fields:
-
- Content-Type: Message/Partial;
- number=2; total=3;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
-
- Content-Type: Message/Partial;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
- number=2
-
- But part 3 MUST specify the total number of parts:
-
- Content-Type: Message/Partial;
- number=3; total=3;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
-
- Note that part numbering begins with 1, not 0.
-
- When the parts of a message broken up in this manner are put
- together, the result is a complete RFC 822 format message,
- which may have its own Content-Type header field, and thus
- may contain any other data type.
-
- Message fragmentation and reassembly: The semantics of a
- reassembled partial message must be those of the "inner"
- message, rather than of a message containing the inner
- message. This makes it possible, for example, to send a
- large audio message as several partial messages, and still
- have it appear to the recipient as a simple audio message
- rather than as an encapsulated message containing an audio
- message. That is, the encapsulation of the message is
- considered to be "transparent".
-
- When generating and reassembling the parts of a
- message/partial message, the headers of the encapsulated
- message must be merged with the headers of the enclosing
-
-
-
- Borenstein & Freed [Page 38]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- entities. In this process the following rules must be
- observed:
-
- (1) All of the headers from the initial enclosing
- entity (part one), except those that start with
- "Content-" and "Message-ID", must be copied, in
- order, to the new message.
-
- (2) Only those headers in the enclosed message
- which start with "Content-" and "Message-ID" must
- be appended, in order, to the headers of the new
- message. Any headers in the enclosed message
- which do not start with "Content-" (except for
- "Message-ID") will be ignored.
-
- (3) All of the headers from the second and any
- subsequent messages will be ignored.
-
- For example, if an audio message is broken into two parts,
- the first part might look something like this:
-
- X-Weird-Header-1: Foo
- From: Bill@host.com
- To: joe@otherhost.com
- Subject: Audio mail
- Message-ID: id1@host.com
- MIME-Version: 1.0
- Content-type: message/partial;
- id="ABC@host.com";
- number=1; total=2
-
- X-Weird-Header-1: Bar
- X-Weird-Header-2: Hello
- Message-ID: anotherid@foo.com
- Content-type: audio/basic
- Content-transfer-encoding: base64
-
- ... first half of encoded audio data goes here...
-
- and the second half might look something like this:
-
- From: Bill@host.com
- To: joe@otherhost.com
- Subject: Audio mail
- MIME-Version: 1.0
- Message-ID: id2@host.com
- Content-type: message/partial;
- id="ABC@host.com"; number=2; total=2
-
- ... second half of encoded audio data goes here...
-
- Then, when the fragmented message is reassembled, the
- resulting message to be displayed to the user should look
- something like this:
-
-
-
- Borenstein & Freed [Page 39]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- X-Weird-Header-1: Foo
- From: Bill@host.com
- To: joe@otherhost.com
- Subject: Audio mail
- Message-ID: anotherid@foo.com
- MIME-Version: 1.0
- Content-type: audio/basic
- Content-transfer-encoding: base64
-
- ... first half of encoded audio data goes here...
- ... second half of encoded audio data goes here...
-
- It should be noted that, because some message transfer
- agents may choose to automatically fragment large messages,
- and because such agents may use different fragmentation
- thresholds, it is possible that the pieces of a partial
- message, upon reassembly, may prove themselves to comprise a
- partial message. This is explicitly permitted.
-
- It should also be noted that the inclusion of a "References"
- field in the headers of the second and subsequent pieces of
- a fragmented message that references the Message-Id on the
- previous piece may be of benefit to mail readers that
- understand and track references. However, the generation of
- such "References" fields is entirely optional.
-
- 7.3.3 The Message/External-Body subtype
-
- The external-body subtype indicates that the actual body
- data are not included, but merely referenced. In this case,
- the parameters describe a mechanism for accessing the
- external data.
-
- When a message body or body part is of type
- "message/external-body", it consists of a header, two
- consecutive CRLFs, and the message header for the
- encapsulated message. If another pair of consecutive CRLFs
- appears, this of course ends the message header for the
- encapsulated message. However, since the encapsulated
- message's body is itself external, it does NOT appear in the
- area that follows. For example, consider the following
- message:
-
- Content-type: message/external-body; access-
- type=local-file;
- name=/u/nsb/Me.gif
-
- Content-type: image/gif
-
- THIS IS NOT REALLY THE BODY!
-
- The area at the end, which might be called the "phantom
- body", is ignored for most external-body messages. However,
- it may be used to contain auxilliary information for some
-
-
-
- Borenstein & Freed [Page 40]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- such messages, as indeed it is when the access-type is
- "mail-server". Of the access-types defined by this
- document, the phantom body is used only when the access-type
- is "mail-server". In all other cases, the phantom body is
- ignored.
-
- The only always-mandatory parameter for message/external-
- body is "access-type"; all of the other parameters may be
- mandatory or optional depending on the value of access-type.
-
- ACCESS-TYPE -- One or more case-insensitive words,
- comma-separated, indicating supported access
- mechanisms by which the file or data may be
- obtained. Values include, but are not limited to,
- "FTP", "ANON-FTP", "TFTP", "AFS", "LOCAL-FILE",
- and "MAIL-SERVER". Future values, except for
- experimental values beginning with "X-", must be
- registered with IANA, as described in Appendix F .
-
- In addition, the following two parameters are optional for
- ALL access-types:
-
- EXPIRATION -- The date (in the RFC 822 "date-time"
- syntax, as extended by RFC 1123 to permit 4 digits
- in the date field) after which the existence of
- the external data is not guaranteed.
-
- SIZE -- The size (in octets) of the data. The
- intent of this parameter is to help the recipient
- decide whether or not to expend the necessary
- resources to retrieve the external data.
-
- PERMISSION -- A field that indicates whether or
- not it is expected that clients might also attempt
- to overwrite the data. By default, or if
- permission is "read", the assumption is that they
- are not, and that if the data is retrieved once,
- it is never needed again. If PERMISSION is "read-
- write", this assumption is invalid, and any local
- copy must be considered no more than a cache.
- "Read" and "Read-write" are the only defined
- values of permission.
-
- The precise semantics of the access-types defined here are
- described in the sections that follow.
-
- 7.3.3.1 The "ftp" and "tftp" access-types
-
- An access-type of FTP or TFTP indicates that the message
- body is accessible as a file using the FTP [RFC-959] or TFTP
- [RFC-783] protocols, respectively. For these access-types,
- the following additional parameters are mandatory:
-
-
-
-
-
- Borenstein & Freed [Page 41]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- NAME -- The name of the file that contains the
- actual body data.
-
- SITE -- A machine from which the file may be
- obtained, using the given protocol
-
- Before the data is retrieved, using these protocols, the
- user will generally need to be asked to provide a login id
- and a password for the machine named by the site parameter.
-
- In addition, the following optional parameters may also
- appear when the access-type is FTP or ANON-FTP:
-
- DIRECTORY -- A directory from which the data named
- by NAME should be retrieved.
-
- MODE -- A transfer mode for retrieving the
- information, e.g. "image".
-
- 7.3.3.2 The "anon-ftp" access-type
-
- The "anon-ftp" access-type is identical to the "ftp" access
- type, except that the user need not be asked to provide a
- name and password for the specified site. Instead, the ftp
- protocol will be used with login "anonymous" and a password
- that corresponds to the user's email address.
-
- 7.3.3.3 The "local-file" and "afs" access-types
-
- An access-type of "local-file" indicates that the actual
- body is accessible as a file on the local machine. An
- access-type of "afs" indicates that the file is accessible
- via the global AFS file system. In both cases, only a
- single parameter is required:
-
- NAME -- The name of the file that contains the
- actual body data.
-
- The following optional parameter may be used to describe the
- locality of reference for the data, that is, the site or
- sites at which the file is expected to be visible:
-
- SITE -- A domain specifier for a machine or set of
- machines that are known to have access to the data
- file. Asterisks may be used for wildcard matching
- to a part of a domain name, such as
- "*.bellcore.com", to indicate a set of machines on
- which the data should be directly visible, while a
- single asterisk may be used to indicate a file
- that is expected to be universally available,
- e.g., via a global file system.
-
- 7.3.3.4 The "mail-server" access-type
-
-
-
-
- Borenstein & Freed [Page 42]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- The "mail-server" access-type indicates that the actual body
- is available from a mail server. The mandatory parameter
- for this access-type is:
-
- SERVER -- The email address of the mail server
- from which the actual body data can be obtained.
-
- Because mail servers accept a variety of syntax, some of
- which is multiline, the full command to be sent to a mail
- server is not included as a parameter on the content-type
- line. Instead, it may be provided as the "phantom body"
- when the content-type is message/external-body and the
- access-type is mail-server.
-
- Note that MIME does not define a mail server syntax.
- Rather, it allows the inclusion of arbitrary mail server
- commands in the phantom body. Implementations should
- include the phantom body in the body of the message it sends
- to the mail server address to retrieve the relevant data.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 43]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.3.3.5 Examples and Further Explanations
-
- With the emerging possibility of very wide-area file
- systems, it becomes very hard to know in advance the set of
- machines where a file will and will not be accessible
- directly from the file system. Therefore it may make sense
- to provide both a file name, to be tried directly, and the
- name of one or more sites from which the file is known to be
- accessible. An implementation can try to retrieve remote
- files using FTP or any other protocol, using anonymous file
- retrieval or prompting the user for the necessary name and
- password. If an external body is accessible via multiple
- mechanisms, the sender may include multiple parts of type
- message/external-body within an entity of type
- multipart/alternative.
-
- However, the external-body mechanism is not intended to be
- limited to file retrieval, as shown by the mail-server
- access-type. Beyond this, one can imagine, for example,
- using a video server for external references to video clips.
-
- If an entity is of type "message/external-body", then the
- body of the entity will contain the header fields of the
- encapsulated message. The body itself is to be found in the
- external location. This means that if the body of the
- "message/external-body" message contains two consecutive
- CRLFs, everything after those pairs is NOT part of the
- message itself. For most message/external-body messages,
- this trailing area must simply be ignored. However, it is a
- convenient place for additional data that cannot be included
- in the content-type header field. In particular, if the
- "access-type" value is "mail-server", then the trailing area
- must contain commands to be sent to the mail server at the
- address given by NAME@SITE, where NAME and SITE are the
- values of the NAME and SITE parameters, respectively.
-
- The embedded message header fields which appear in the body
- of the message/external-body data can be used to declare the
- Content-type of the external body. Thus a complete
- message/external-body message, referring to a document in
- PostScript format, might look like this:
-
- From: Whomever
- Subject: whatever
- MIME-Version: 1.0
- Message-ID: id1@host.com
- Content-Type: multipart/alternative; boundary=42
-
-
- --42
- Content-Type: message/external-body;
- name="BodyFormats.ps";
-
-
-
-
-
- Borenstein & Freed [Page 44]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- site="thumper.bellcore.com";
- access-type=ANON-FTP;
- directory="pub";
- mode="image";
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
-
- --42
- Content-Type: message/external-body;
- name="/u/nsb/writing/rfcs/RFC-XXXX.ps";
- site="thumper.bellcore.com";
- access-type=AFS
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
-
- --42
- Content-Type: message/external-body;
- access-type=mail-server
- server="listserv@bogus.bitnet";
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
-
- get rfc-xxxx doc
-
- --42--
-
- Like the message/partial type, the message/external-body
- type is intended to be transparent, that is, to convey the
- data type in the external body rather than to convey a
- message with a body of that type. Thus the headers on the
- outer and inner parts must be merged using the same rules as
- for message/partial. In particular, this means that the
- Content-type header is overridden, but the From and Subject
- headers are preserved.
-
- Note that since the external bodies are not transported as
- mail, they need not conform to the 7-bit and line length
- requirements, but might in fact be binary files. Thus a
- Content-Transfer-Encoding is not generally necessary, though
- it is permitted.
-
- Note that the body of a message of type "message/external-
- body" is governed by the basic syntax for an RFC 822
- message. In particular, anything before the first
- consecutive pair of CRLFs is header information, while
- anything after it is body information, which is ignored for
- most access-types.
-
-
-
-
-
-
-
- Borenstein & Freed [Page 45]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.4 The Application Content-Type
-
- The "application" Content-Type is to be used for data which
- do not fit in any of the other categories, and particularly
- for data to be processed by mail-based uses of application
- programs. This is information which must be processed by an
- application before it is viewable or usable to a user.
- Expected uses for Content-Type application include mail-
- based file transfer, spreadsheets, data for mail-based
- scheduling systems, and languages for "active"
- (computational) email. (The latter, in particular, can pose
- security problems which should be understood by
- implementors, and are considered in detail in the discussion
- of the application/PostScript content-type.)
-
- For example, a meeting scheduler might define a standard
- representation for information about proposed meeting dates.
- An intelligent user agent would use this information to
- conduct a dialog with the user, and might then send further
- mail based on that dialog. More generally, there have been
- several "active" messaging languages developed in which
- programs in a suitably specialized language are sent through
- the mail and automatically run in the recipient's
- environment.
-
- Such applications may be defined as subtypes of the
- "application" Content-Type. This document defines three
- subtypes: octet-stream, ODA, and PostScript.
-
- In general, the subtype of application will often be the
- name of the application for which the data are intended.
- This does not mean, however, that any application program
- name may be used freely as a subtype of application. Such
- usages must be registered with IANA, as described in
- Appendix F.
-
- 7.4.1 The Application/Octet-Stream (primary) subtype
-
- The primary subtype of application, "octet-stream", may be
- used to indicate that a body contains binary data. The set
- of possible parameters includes, but is not limited to:
-
- NAME -- a suggested name for the binary data if
- stored as a file.
-
- TYPE -- the general type or category of binary
- data. This is intended as information for the
- human recipient rather than for any automatic
- processing.
-
- CONVERSIONS -- the set of operations that have
- been performed on the data before putting it in
- the mail (and before any Content-Transfer-Encoding
- that might have been applied). If multiple
-
-
-
- Borenstein & Freed [Page 46]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- conversions have occurred, they must be separated
- by commas and specified in the order they were
- applied -- that is, the leftmost conversion must
- have occurred first, and conversions are undone
- from right to left. Note that NO conversion
- values are defined by this document. Any
- conversion values that that do not begin with "X-"
- must be preceded by a published specification and
- by registration with IANA, as described in
- Appendix F.
-
- PADDING -- the number of bits of padding that were
- appended to the bitstream comprising the actual
- contents to produce the enclosed byte-oriented
- data. This is useful for enclosing a bitstream in
- a body when the total number of bits is not a
- multiple of the byte size.
-
- The values for these attributes are left undefined at
- present, but may require specification in the future. An
- example of a common (though UNIX-specific) usage might be:
-
- Content-Type: application/octet-stream;
- name=foo.tar.Z; type=tar;
- conversions="x-encrypt,x-compress"
-
- However, it should be noted that the use of such conversions
- is explicitly discouraged due to a lack of portability and
- standardization. The use of uuencode is particularly
- discouraged, in favor of the Content-Transfer-Encoding
- mechanism, which is both more standardized and more portable
- across mail boundaries.
-
- The recommended action for an implementation that receives
- application/octet-stream mail is to simply offer to put the
- data in a file, with any Content-Transfer-Encoding undone,
- or perhaps to use it as input to a user-specified process.
-
- To reduce the danger of transmitting rogue programs through
- the mail, it is strongly recommended that implementations
- NOT implement a path-search mechanism whereby an arbitrary
- program named in the Content-Type parameter (e.g., an
- "interpreter=" parameter) is found and executed using the
- mail body as input.
-
- 7.4.2 The Application/PostScript subtype
-
- A Content-Type of "application/postscript" indicates a
- PostScript program. The language is defined in
- [POSTSCRIPT]. It is recommended that Postscript as sent
- through email should use Postscript document structuring
- conventions if at all possible, and correctly.
-
-
-
-
-
- Borenstein & Freed [Page 47]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- The execution of general-purpose PostScript interpreters
- entails serious security risks, and implementors are
- discouraged from simply sending PostScript email bodies to
- "off-the-shelf" interpreters. While it is usually safe to
- send PostScript to a printer, where the potential for harm
- is greatly constrained, implementors should consider all of
- the following before they add interactive display of
- PostScript bodies to their mail readers.
-
- The remainder of this section outlines some, though probably
- not all, of the possible problems with sending PostScript
- through the mail.
-
- Dangerous operations in the PostScript language include, but
- may not be limited to, the PostScript operators deletefile,
- renamefile, filenameforall, and file. File is only
- dangerous when applied to something other than standard
- input or output. Implementations may also define additional
- nonstandard file operators; these may also pose a threat to
- security. Filenameforall, the wildcard file search
- operator, may appear at first glance to be harmless. Note,
- however, that this operator has the potential to reveal
- information about what files the recipient has access to,
- and this information may itself be sensitive. Message
- senders should avoid the use of potentially dangerous file
- operators, since these operators are quite likely to be
- unavailable in secure PostScript implementations. Message-
- receiving and -displaying software should either completely
- disable all potentially dangerous file operators or take
- special care not to delegate any special authority to their
- operation. These operators should be viewed as being done by
- an outside agency when interpreting PostScript documents.
- Such disabling and/or checking should be done completely
- outside of the reach of the PostScript language itself; care
- should be taken to insure that no method exists for
- reenabling full-function versions of these operators.
-
- The PostScript language provides facilities for exiting the
- normal interpreter, or server, loop. Changes made in this
- "outer" environment are customarily retained across
- documents, and may in some cases be retained semipermanently
- in nonvolatile memory. The operators associated with exiting
- the interpreter loop have the potential to interfere with
- subsequent document processing. As such, their unrestrained
- use constitutes a threat of service denial. PostScript
- operators that exit the interpreter loop include, but may
- not be limited to, the exitserver and startjob operators.
- Message-sending software should not generate PostScript that
- depends on exiting the interpreter loop to operate. The
- ability to exit will probably be unavailable in secure
- PostScript implementations. Message-receiving and
- -displaying software should, if possible, disable the
- ability to make retained changes to the PostScript
- environment. Eliminate the startjob and exitserver commands.
-
-
-
- Borenstein & Freed [Page 48]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- If these commands cannot be eliminated, at least set the
- password associated with them to a hard-to-guess value.
-
- PostScript provides operators for setting system-wide and
- device-specific parameters. These parameter settings may be
- retained across jobs and may potentially pose a threat to
- the correct operation of the interpreter. The PostScript
- operators that set system and device parameters include, but
- may not be limited to, the setsystemparams and setdevparams
- operators. Message-sending software should not generate
- PostScript that depends on the setting of system or device
- parameters to operate correctly. The ability to set these
- parameters will probably be unavailable in secure PostScript
- implementations. Message-receiving and -displaying software
- should, if possible, disable the ability to change system
- and device parameters. If these operators cannot be
- disabled, at least set the password associated with them to
- a hard-to-guess value.
-
- Some PostScript implementations provide nonstandard
- facilities for the direct loading and execution of machine
- code. Such facilities are quite obviously open to
- substantial abuse. Message-sending software should not
- make use of such features. Besides being totally hardware-
- specific, they are also likely to be unavailable in secure
- implementations of PostScript. Message-receiving and
- -displaying software should not allow such operators to be
- used if they exist.
-
- PostScript is an extensible language, and many, if not most,
- implementations of it provide a number of their own
- extensions. This document does not deal with such extensions
- explicitly since they constitute an unknown factor.
- Message-sending software should not make use of nonstandard
- extensions; they are likely to be missing from some
- implementations. Message-receiving and -displaying software
- should make sure that any nonstandard PostScript operators
- are secure and don't present any kind of threat.
-
- It is possible to write PostScript that consumes huge
- amounts of various system resources. It is also possible to
- write PostScript programs that loop infinitely. Both types
- of programs have the potential to cause damage if sent to
- unsuspecting recipients. Message-sending software should
- avoid the construction and dissemination of such programs,
- which is antisocial. Message-receiving and -displaying
- software should provide appropriate mechanisms to abort
- processing of a document after a reasonable amount of time
- has elapsed. In addition, PostScript interpreters should be
- limited to the consumption of only a reasonable amount of
- any given system resource.
-
- Finally, bugs may exist in some PostScript interpreters
- which could possibly be exploited to gain unauthorized
-
-
-
- Borenstein & Freed [Page 49]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- access to a recipient's system. Apart from noting this
- possibility, there is no specific action to take to prevent
- this, apart from the timely correction of such bugs if any
- are found.
-
- 7.4.3 The Application/ODA subtype
-
- The "ODA" subtype of application is used to indicate that a
- body contains information encoded according to the Office
- Document Architecture [ODA] standards, using the ODIF
- representation format. For application/oda, the Content-
- Type line should also specify an attribute/value pair that
- indicates the document application profile (DAP), using the
- key word "profile". Thus an appropriate header field might
- look like this:
-
- Content-Type: application/oda; profile=Q112
-
- Consult the ODA standard [ODA] for further information.
-
-
-
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-
-
- Borenstein & Freed [Page 50]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 7.5 The Image Content-Type
-
- A Content-Type of "image" indicates that the bodycontains an
- image. The subtype names the specific image format. These
- names are case insensitive. Two initial subtypes are "jpeg"
- for the JPEG format, JFIF encoding, and "gif" for GIF format
- [GIF].
-
- The list of image subtypes given here is neither exclusive
- nor exhaustive, and is expected to grow as more types are
- registered with IANA, as described in Appendix F.
-
- 7.6 The Audio Content-Type
-
- A Content-Type of "audio" indicates that the body contains
- audio data. Although there is not yet a consensus on an
- "ideal" audio format for use with computers, there is a
- pressing need for a format capable of providing
- interoperable behavior.
-
- The initial subtype of "basic" is specified to meet this
- requirement by providing an absolutely minimal lowest common
- denominator audio format. It is expected that richer
- formats for higher quality and/or lower bandwidth audio will
- be defined by a later document.
-
- The content of the "audio/basic" subtype is audio encoded
- using 8-bit ISDN u-law [PCM]. When this subtype is present,
- a sample rate of 8000 Hz and a single channel is assumed.
-
- 7.7 The Video Content-Type
-
- A Content-Type of "video" indicates that the body contains a
- time-varying-picture image, possibly with color and
- coordinated sound. The term "video" is used extremely
- generically, rather than with reference to any particular
- technology or format, and is not meant to preclude subtypes
- such as animated drawings encoded compactly. The subtype
- "mpeg" refers to video coded according to the MPEG standard
- [MPEG].
-
- Note that although in general this document strongly
- discourages the mixing of multiple media in a single body,
- it is recognized that many so-called "video" formats include
- a representation for synchronized audio, and this is
- explicitly permitted for subtypes of "video".
-
- 7.8 Experimental Content-Type Values
-
- A Content-Type value beginning with the characters "X-" is a
- private value, to be used by consenting mail systems by
- mutual agreement. Any format without a rigorous and public
- definition must be named with an "X-" prefix, and publicly
- specified values shall never begin with "X-". (Older
-
-
-
- Borenstein & Freed [Page 51]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- versions of the widely-used Andrew system use the "X-BE2"
- name, so new systems should probably choose a different
- name.)
-
- In general, the use of "X-" top-level types is strongly
- discouraged. Implementors should invent subtypes of the
- existing types whenever possible. The invention of new
- types is intended to be restricted primarily to the
- development of new media types for email, such as digital
- odors or holography, and not for new data formats in
- general. In many cases, a subtype of application will be
- more appropriate than a new top-level type.
-
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-
-
- Borenstein & Freed [Page 52]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Summary
-
- Using the MIME-Version, Content-Type, and Content-Transfer-
- Encoding header fields, it is possible to include, in a
- standardized way, arbitrary types of data objects with RFC
- 822 conformant mail messages. No restrictions imposed by
- either RFC 821 or RFC 822 are violated, and care has been
- taken to avoid problems caused by additional restrictions
- imposed by the characteristics of some Internet mail
- transport mechanisms (see Appendix B). The "multipart" and
- "message" Content-Types allow mixing and hierarchical
- structuring of objects of different types in a single
- message. Further Content-Types provide a standardized
- mechanism for tagging messages or body parts as audio,
- image, or several other kinds of data. A distinguished
- parameter syntax allows further specification of data format
- details, particularly the specification of alternate
- character sets. Additional optional header fields provide
- mechanisms for certain extensions deemed desirable by many
- implementors. Finally, a number of useful Content-Types are
- defined for general use by consenting user agents, notably
- text/richtext, message/partial, and message/external-body.
-
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-
-
- Borenstein & Freed [Page 53]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Acknowledgements
-
- This document is the result of the collective effort of a
- large number of people, at several IETF meetings, on the
- IETF-SMTP and IETF-822 mailing lists, and elsewhere.
- Although any enumeration seems doomed to suffer from
- egregious omissions, the following are among the many
- contributors to this effort:
-
- Harald Tveit Alvestrand Timo Lehtinen
- Randall Atkinson John R. MacMillan
- Philippe Brandon Rick McGowan
- Kevin Carosso Leo Mclaughlin
- Uhhyung Choi Goli Montaser-Kohsari
- Cristian Constantinof Keith Moore
- Mark Crispin Tom Moore
- Dave Crocker Erik Naggum
- Terry Crowley Mark Needleman
- Walt Daniels John Noerenberg
- Frank Dawson Mats Ohrman
- Hitoshi Doi Julian Onions
- Kevin Donnelly Michael Patton
- Keith Edwards David J. Pepper
- Chris Eich Blake C. Ramsdell
- Johnny Eriksson Luc Rooijakkers
- Craig Everhart Marshall T. Rose
- Patrik Faeltstroem Jonathan Rosenberg
- Erik E. Fair Jan Rynning
- Roger Fajman Harri Salminen
- Alain Fontaine Michael Sanderson
- James M. Galvin Masahiro Sekiguchi
- Philip Gladstone Mark Sherman
- Thomas Gordon Keld Simonsen
- Phill Gross Bob Smart
- James Hamilton Peter Speck
- Steve Hardcastle-Kille Henry Spencer
- David Herron Einar Stefferud
- Bruce Howard Michael Stein
- Bill Janssen Klaus Steinberger
- Olle Jaernefors Peter Svanberg
- Risto Kankkunen James Thompson
- Phil Karn Steve Uhler
- Alan Katz Stuart Vance
- Tim Kehres Erik van der Poel
- Neil Katin Guido van Rossum
- Kyuho Kim Peter Vanderbilt
- Anders Klemets Greg Vaudreuil
- John Klensin Ed Vielmetti
- Valdis Kletniek Ryan Waldron
- Jim Knowles Wally Wedel
- Stev Knowles Sven-Ove Westberg
- Bob Kummerfeld Brian Wideen
-
-
-
-
-
- Borenstein & Freed [Page 54]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Pekka Kytolaakso John Wobus
- Stellan Lagerstr.m Glenn Wright
- Vincent Lau Rayan Zachariassen
- Donald Lindsay David Zimmerman
- The authors apologize for any omissions from this list,
- which are certainly unintentional.
-
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- Borenstein & Freed [Page 55]
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-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix A -- Minimal MIME-Conformance
-
- The mechanisms described in this document are open-ended.
- It is definitely not expected that all implementations will
- support all of the Content-Types described, nor that they
- will all share the same extensions. In order to promote
- interoperability, however, it is useful to define the
- concept of "MIME-conformance" to define a certain level of
- implementation that allows the useful interworking of
- messages with content that differs from US ASCII text. In
- this section, we specify the requirements for such
- conformance.
-
- A mail user agent that is MIME-conformant MUST:
-
- 1. Always generate a "MIME-Version: 1.0" header
- field.
-
- 2. Recognize the Content-Transfer-Encoding header
- field, and decode all received data encoded with
- either the quoted-printable or base64
- implementations. Encode any data sent that is
- not in seven-bit mail-ready representation using
- one of these transformations and include the
- appropriate Content-Transfer-Encoding header
- field, unless the underlying transport mechanism
- supports non-seven-bit data, as SMTP does not.
-
- 3. Recognize and interpret the Content-Type
- header field, and avoid showing users raw data
- with a Content-Type field other than text. Be
- able to send at least text/plain messages, with
- the character set specified as a parameter if it
- is not US-ASCII.
-
- 4. Explicitly handle the following Content-Type
- values, to at least the following extents:
-
- Text:
- -- Recognize and display "text" mail
- with the character set "US-ASCII."
- -- Recognize other character sets at
- least to the extent of being able
- to inform the user about what
- character set the message uses.
- -- Recognize the "ISO-8859-*" character
- sets to the extent of being able to
- display those characters that are
- common to ISO-8859-* and US-ASCII,
- namely all characters represented
- by octet values 0-127.
- -- For unrecognized subtypes, show or
- offer to show the user the "raw"
- version of the data. An ability at
-
-
-
- Borenstein & Freed [Page 56]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- least to convert "text/richtext" to
- plain text, as shown in Appendix D,
- is encouraged, but not required for
- conformance.
- Message:
- --Recognize and display at least the
- primary (822) encapsulation.
- Multipart:
- -- Recognize the primary (mixed)
- subtype. Display all relevant
- information on the message level
- and the body part header level and
- then display or offer to display
- each of the body parts
- individually.
- -- Recognize the "alternative" subtype,
- and avoid showing the user
- redundant parts of
- multipart/alternative mail.
- -- Treat any unrecognized subtypes as if
- they were "mixed".
- Application:
- -- Offer the ability to remove either of
- the two types of Content-Transfer-
- Encoding defined in this document
- and put the resulting information
- in a user file.
-
- 5. Upon encountering any unrecognized Content-
- Type, an implementation must treat it as if it had
- a Content-Type of "application/octet-stream" with
- no parameter sub-arguments. How such data are
- handled is up to an implementation, but likely
- options for handling such unrecognized data
- include offering the user to write it into a file
- (decoded from its mail transport format) or
- offering the user to name a program to which the
- decoded data should be passed as input.
- Unrecognized predefined types, which in a MIME-
- conformant mailer might still include audio,
- image, or video, should also be treated in this
- way.
-
- A user agent that meets the above conditions is said to be
- MIME-conformant. The meaning of this phrase is that it is
- assumed to be "safe" to send virtually any kind of
- properly-marked data to users of such mail systems, because
- such systems will at least be able to treat the data as
- undifferentiated binary, and will not simply splash it onto
- the screen of unsuspecting users. There is another sense
- in which it is always "safe" to send data in a format that
- is MIME-conformant, which is that such data will not break
- or be broken by any known systems that are conformant with
- RFC 821 and RFC 822. User agents that are MIME-conformant
-
-
-
- Borenstein & Freed [Page 57]
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-
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- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- have the additional guarantee that the user will not be
- shown data that were never intended to be viewed as text.
-
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- Borenstein & Freed [Page 58]
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- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix B -- General Guidelines For Sending Email Data
-
- Internet email is not a perfect, homogeneous system. Mail
- may become corrupted at several stages in its travel to a
- final destination. Specifically, email sent throughout the
- Internet may travel across many networking technologies.
- Many networking and mail technologies do not support the
- full functionality possible in the SMTP transport
- environment. Mail traversing these systems is likely to be
- modified in such a way that it can be transported.
-
- There exist many widely-deployed non-conformant MTAs in the
- Internet. These MTAs, speaking the SMTP protocol, alter
- messages on the fly to take advantage of the internal data
- structure of the hosts they are implemented on, or are just
- plain broken.
-
- The following guidelines may be useful to anyone devising a
- data format (Content-Type) that will survive the widest
- range of networking technologies and known broken MTAs
- unscathed. Note that anything encoded in the base64
- encoding will satisfy these rules, but that some well-known
- mechanisms, notably the UNIX uuencode facility, will not.
- Note also that anything encoded in the Quoted-Printable
- encoding will survive most gateways intact, but possibly not
- some gateways to systems that use the EBCDIC character set.
-
- (1) Under some circumstances the encoding used for
- data may change as part of normal gateway or user
- agent operation. In particular, conversion from
- base64 to quoted-printable and vice versa may be
- necessary. This may result in the confusion of
- CRLF sequences with line breaks in text body
- parts. As such, the persistence of CRLF as
- something other than a line break should not be
- relied on.
-
- (2) Many systems may elect to represent and store
- text data using local newline conventions. Local
- newline conventions may not match the RFC822 CRLF
- convention -- systems are known that use plain CR,
- plain LF, CRLF, or counted records. The result is
- that isolated CR and LF characters are not well
- tolerated in general; they may be lost or
- converted to delimiters on some systems, and hence
- should not be relied on.
-
- (3) TAB (HT) characters may be misinterpreted or
- may be automatically converted to variable numbers
- of spaces. This is unavoidable in some
- environments, notably those not based on the ASCII
- character set. Such conversion is STRONGLY
- DISCOURAGED, but it may occur, and mail formats
- should not rely on the persistence of TAB (HT)
-
-
-
- Borenstein & Freed [Page 59]
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- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- characters.
-
- (4) Lines longer than 76 characters may be wrapped
- or truncated in some environments. Line wrapping
- and line truncation are STRONGLY DISCOURAGED, but
- unavoidable in some cases. Applications which
- require long lines should somehow differentiate
- between soft and hard line breaks. (A simple way
- to do this is to use the quoted-printable
- encoding.)
-
- (5) Trailing "white space" characters (SPACE, TAB
- (HT)) on a line may be discarded by some transport
- agents, while other transport agents may pad lines
- with these characters so that all lines in a mail
- file are of equal length. The persistence of
- trailing white space, therefore, should not be
- relied on.
-
- (6) Many mail domains use variations on the ASCII
- character set, or use character sets such as
- EBCDIC which contain most but not all of the US-
- ASCII characters. The correct translation of
- characters not in the "invariant" set cannot be
- depended on across character converting gateways.
- For example, this situation is a problem when
- sending uuencoded information across BITNET, an
- EBCDIC system. Similar problems can occur without
- crossing a gateway, since many Internet hosts use
- character sets other than ASCII internally. The
- definition of Printable Strings in X.400 adds
- further restrictions in certain special cases. In
- particular, the only characters that are known to
- be consistent across all gateways are the 73
- characters that correspond to the upper and lower
- case letters A-Z and a-z, the 10 digits 0-9, and
- the following eleven special characters:
-
- "'" (ASCII code 39)
- "(" (ASCII code 40)
- ")" (ASCII code 41)
- "+" (ASCII code 43)
- "," (ASCII code 44)
- "-" (ASCII code 45)
- "." (ASCII code 46)
- "/" (ASCII code 47)
- ":" (ASCII code 58)
- "=" (ASCII code 61)
- "?" (ASCII code 63)
-
- A maximally portable mail representation, such as
- the base64 encoding, will confine itself to
- relatively short lines of text in which the only
- meaningful characters are taken from this set of
-
-
-
- Borenstein & Freed [Page 60]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- 73 characters.
-
- Please note that the above list is NOT a list of recommended
- practices for MTAs. RFC 821 MTAs are prohibited from
- altering the character of white space or wrapping long
- lines. These BAD and illegal practices are known to occur
- on established networks, and implementions should be robust
- in dealing with the bad effects they can cause.
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-
-
- Borenstein & Freed [Page 61]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix C -- A Complex Multipart Example
-
- What follows is the outline of a complex multipart message.
- This message has five parts to be displayed serially: two
- introductory plain text parts, an embedded multipart
- message, a richtext part, and a closing encapsulated text
- message in a non-ASCII character set. The embedded
- multipart message has two parts to be displayed in parallel,
- a picture and an audio fragment.
-
- MIME-Version: 1.0
- From: Nathaniel Borenstein <nsb@bellcore.com>
- Subject: A multipart example
- Content-Type: multipart/mixed;
- boundary=unique-boundary-1
-
- This is the preamble area of a multipart message.
- Mail readers that understand multipart format
- should ignore this preamble.
- If you are reading this text, you might want to
- consider changing to a mail reader that understands
- how to properly display multipart messages.
- --unique-boundary-1
-
- ...Some text appears here...
- [Note that the preceding blank line means
- no header fields were given and this is text,
- with charset US ASCII. It could have been
- done with explicit typing as in the next part.]
-
- --unique-boundary-1
- Content-type: text/plain; charset=US-ASCII
-
- This could have been part of the previous part,
- but illustrates explicit versus implicit
- typing of body parts.
-
- --unique-boundary-1
- Content-Type: multipart/parallel;
- boundary=unique-boundary-2
-
-
- --unique-boundary-2
- Content-Type: audio/basic
- Content-Transfer-Encoding: base64
-
- ... base64-encoded 8000 Hz single-channel
- u-law-format audio data goes here....
-
- --unique-boundary-2
- Content-Type: image/gif
- Content-Transfer-Encoding: Base64
-
-
-
-
-
- Borenstein & Freed [Page 62]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- ... base64-encoded image data goes here....
-
- --unique-boundary-2--
-
- --unique-boundary-1
- Content-type: text/richtext
-
- This is <bold><italic>richtext.</italic></bold>
- <nl><nl>Isn't it
- <bigger><bigger>cool?</bigger></bigger>
-
- --unique-boundary-1
- Content-Type: message/rfc822
-
- From: (name in US-ASCII)
- Subject: (subject in US-ASCII)
- Content-Type: Text/plain; charset=ISO-8859-1
- Content-Transfer-Encoding: Quoted-printable
-
- ... Additional text in ISO-8859-1 goes here ...
-
- --unique-boundary-1--
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 63]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix D -- A Simple Richtext-to-Text Translator in C
-
- One of the major goals in the design of the richtext subtype
- of the text Content-Type is to make formatted text so simple
- that even text-only mailers will implement richtext-to-
- plain-text translators, thus increasing the likelihood that
- multifont text will become "safe" to use very widely. To
- demonstrate this simplicity, what follows is an extremely
- simple 44-line C program that converts richtext input into
- plain text output:
-
- #include <stdio.h>
- #include <ctype.h>
- main() {
- int c, i;
- char token[50];
-
- while((c = getc(stdin)) != EOF) {
- if (c == '<') {
- for (i=0; (i<49 && (c = getc(stdin)) != '>'
- && c != EOF); ++i) {
- token[i] = isupper(c) ? tolower(c) : c;
- }
- if (c == EOF) break;
- if (c != '>') while ((c = getc(stdin)) !=
- '>'
- && c != EOF) {;}
- if (c == EOF) break;
- token[i] = '\0';
- if (!strcmp(token, "lt")) {
- putc('<', stdout);
- } else if (!strcmp(token, "nl")) {
- putc('\n', stdout);
- } else if (!strcmp(token, "/paragraph")) {
- fputs("\n\n", stdout);
- } else if (!strcmp(token, "comment")) {
- int commct=1;
- while (commct > 0) {
- while ((c = getc(stdin)) != '<'
- && c != EOF) ;
- if (c == EOF) break;
- for (i=0; (c = getc(stdin)) != '>'
- && c != EOF; ++i) {
- token[i] = isupper(c) ?
- tolower(c) : c;
- }
- if (c== EOF) break;
- token[i] = NULL;
- if (!strcmp(token, "/comment")) --
- commct;
- if (!strcmp(token, "comment"))
- ++commct;
-
-
-
-
-
- Borenstein & Freed [Page 64]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- }
- } /* Ignore all other tokens */
- } else if (c != '\n') putc(c, stdout);
- }
- putc('\n', stdout); /* for good measure */
- }
- It should be noted that one can do considerably better than
- this in displaying richtext data on a dumb terminal. In
- particular, one can replace font information such as "bold"
- with textual emphasis (like *this* or _T_H_I_S_). One can
- also properly handle the richtext formatting commands
- regarding indentation, justification, and others. However,
- the above program is all that is necessary in order to
- present richtext on a dumb terminal.
-
-
-
-
-
-
-
-
-
-
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-
-
-
-
-
-
-
- Borenstein & Freed [Page 65]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix E -- Collected Grammar
-
- This appendix contains the complete BNF grammar for all the
- syntax specified by this document.
-
- By itself, however, this grammar is incomplete. It refers
- to several entities that are defined by RFC 822. Rather
- than reproduce those definitions here, and risk
- unintentional differences between the two, this document
- simply refers the reader to RFC 822 for the remaining
- definitions. Wherever a term is undefined, it refers to the
- RFC 822 definition.
-
- attribute := token
-
- body-part = <"message" as defined in RFC 822,
- with all header fields optional, and with the
- specified delimiter not occurring anywhere in
- the message body, either on a line by itself
- or as a substring anywhere.>
-
- boundary := 0*69<bchars> bcharsnospace
-
- bchars := bcharsnospace / " "
-
- bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /
- "_"
- / "," / "-" / "." / "/" / ":" / "=" / "?"
-
- close-delimiter := delimiter "--"
-
- Content-Description := *text
-
- Content-ID := msg-id
-
- Content-Transfer-Encoding := "BASE64" / "QUOTED-
- PRINTABLE" /
- "8BIT" / "7BIT" /
- "BINARY" / x-token
-
- Content-Type := type "/" subtype *[";" parameter]
-
- delimiter := CRLF "--" boundary ; taken from Content-Type
- field.
- ; when content-type is
- multipart
- ; There should be no space
- ; between "--" and boundary.
-
- encapsulation := delimiter CRLF body-part
-
- epilogue := *text ; to be ignored upon
- receipt.
-
-
-
-
- Borenstein & Freed [Page 66]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- MIME-Version := 1*text
-
- multipart-body := preamble 1*encapsulation close-delimiter
- epilogue
-
- parameter := attribute "=" value
-
- preamble := *text ; to be ignored upon
- receipt.
-
- subtype := token
-
- token := 1*<any CHAR except SPACE, CTLs, or tspecials>
-
- tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in
- / "," / ";" / ":" / "\" / <"> ; quoted-string,
- / "/" / "[" / "]" / "?" / "." ; to use within
- / "=" ; parameter values
-
-
- type := "application" / "audio" ; case-
- insensitive
- / "image" / "message"
- / "multipart" / "text"
- / "video" / x-token
-
- value := token / quoted-string
-
- x-token := <The two characters "X-" followed, with no
- intervening white space, by any token>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 67]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix F -- IANA Registration Procedures
-
- MIME has been carefully designed to have extensible
- mechanisms, and it is expected that the set of content-
- type/subtype pairs and their associated parameters will grow
- significantly with time. Several other MIME fields, notably
- character set names, access-type parameters for the
- message/external-body type, conversions parameters for the
- application type, and possibly even Content-Transfer-
- Encoding values, are likely to have new values defined over
- time. In order to ensure that the set of such values is
- developed in an orderly, well-specified, and public manner,
- MIME defines a registration process which uses the Internet
- Assigned Numbers Authority (IANA) as a central registry for
- such values.
-
- In general, parameters in the content-type header field are
- used to convey supplemental information for various content
- types, and their use is defined when the content-type and
- subtype are defined. New parameters should not be defined
- as a way to introduce new functionality.
-
- In order to simplify and standardize the registration
- process, this appendix gives templates for the registration
- of new values with IANA. Each of these is given in the form
- of an email message template, to be filled in by the
- registering party.
-
- F.1 Registration of New Content-type/subtype Values
-
- Note that MIME is generally expected to be extended by
- subtypes. If a new fundamental top-level type is needed,
- its specification should be published as an RFC or
- submitted in a form suitable to become an RFC, and be
- subject to the Internet standards process.
-
- To: IANA@isi.edu
- Subject: Registration of new MIME content-type/subtype
-
- MIME type name:
-
- (If the above is not an existing top-level MIME type,
- please explain why an existing type cannot be used.)
-
- MIME subtype name:
-
- Required parameters:
-
- Optional parameters:
-
- Encoding considerations:
-
- Security considerations:
-
-
-
-
- Borenstein & Freed [Page 68]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Published specification:
-
- (The published specification must be an Internet RFC or
- RFC-to-be if a new top-level type is being defined, and
- must be a publicly available specification in any
- case.)
-
- Person & email address to contact for further
- information:
- F.2 Registration of New Character Set Values
-
- To: IANA@isi.edu
- Subject: Registration of new MIME character set value
-
- MIME character set name:
-
- Published specification:
-
- (The published specification must be an Internet RFC or
- RFC-to-be or an international standard.)
-
- Person & email address to contact for further
- information:
-
- F.3 Registration of New Access-type Values for
- Message/external-body
-
- To: IANA@isi.edu
- Subject: Registration of new MIME Access-type for
- Message/external-body content-type
-
- MIME access-type name:
-
- Required parameters:
-
- Optional parameters:
-
- Published specification:
-
- (The published specification must be an Internet RFC or
- RFC-to-be.)
-
- Person & email address to contact for further
- information:
-
-
- F.4 Registration of New Conversions Values for Application
-
- To: IANA@isi.edu
- Subject: Registration of new MIME Conversions value
- for Application content-type
-
- MIME Conversions name:
-
-
-
-
- Borenstein & Freed [Page 69]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Published specification:
-
- (The published specification must be an Internet RFC or
- RFC-to-be.)
-
- Person & email address to contact for further
- information:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
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-
-
-
-
- Borenstein & Freed [Page 70]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix G -- Summary of the Seven Content-types
-
- Content-type: text
-
- Subtypes defined by this document: plain, richtext
-
- Important Parameters: charset
-
- Encoding notes: quoted-printable generally preferred if an
- encoding is needed and the character set is mostly an
- ASCII superset.
-
- Security considerations: Rich text formats such as TeX and
- Troff often contain mechanisms for executing arbitrary
- commands or file system operations, and should not be
- used automatically unless these security problems have
- been addressed. Even plain text may contain control
- characters that can be used to exploit the capabilities
- of "intelligent" terminals and cause security
- violations. User interfaces designed to run on such
- terminals should be aware of and try to prevent such
- problems.
- ________________________________________________________________
-
- Content-type: multipart
-
- Subtypes defined by this document: mixed, alternative,
- digest, parallel.
-
- Important Parameters: boundary
-
- Encoding notes: No content-transfer-encoding is permitted.
-
- ________________________________________________________________
-
- Content-type: message
-
- Subtypes defined by this document: rfc822, partial,
- external-body
-
- Important Parameters: id, number, total
-
- Encoding notes: No content-transfer-encoding is permitted.
-
- ________________________________________________________________
-
- Content-type: application
-
- Subtypes defined by this document: octet-stream,
- postscript, oda
-
- Important Parameters: profile
-
-
-
-
-
- Borenstein & Freed [Page 71]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Encoding notes: base64 generally preferred for octet-stream
- or other unreadable subtypes.
-
- Security considerations: This type is intended for the
- transmission of data to be interpreted by locally-installed
- programs. If used, for example, to transmit executable
- binary programs or programs in general-purpose interpreted
- languages, such as LISP programs or shell scripts, severe
- security problems could result. In general, authors of
- mail-reading agents are cautioned against giving their
- systems the power to execute mail-based application data
- without carefully considering the security implications.
- While it is certainly possible to define safe application
- formats and even safe interpreters for unsafe formats, each
- interpreter should be evaluated separately for possible
- security problems.
- ________________________________________________________________
-
- Content-type: image
-
- Subtypes defined by this document: jpeg, gif
-
- Important Parameters: none
-
- Encoding notes: base64 generally preferred
-
- ________________________________________________________________
-
- Content-type: audio
-
- Subtypes defined by this document: basic
-
- Important Parameters: none
-
- Encoding notes: base64 generally preferred
-
- ________________________________________________________________
-
- Content-type: video
-
- Subtypes defined by this document: mpeg
-
- Important Parameters: none
-
- Encoding notes: base64 generally preferred
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 72]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Appendix H -- Canonical Encoding Model
-
-
-
- There was some confusion, in earlier drafts of this memo,
- regarding the model for when email data was to be converted
- to canonical form and encoded, and in particular how this
- process would affect the treatment of CRLFs, given that the
- representation of newlines varies greatly from system to
- system. For this reason, a canonical model for encoding is
- presented below.
-
- The process of composing a MIME message part can be modelled
- as being done in a number of steps. Note that these steps
- are roughly similar to those steps used in RFC1113:
-
- Step 1. Creation of local form.
-
- The body part to be transmitted is created in the system's
- native format. The native character set is used, and where
- appropriate local end of line conventions are used as well.
- The may be a UNIX-style text file, or a Sun raster image, or
- a VMS indexed file, or audio data in a system-dependent
- format stored only in memory, or anything else that
- corresponds to the local model for the representation of
- some form of information.
-
- Step 2. Conversion to canonical form.
-
- The entire body part, including "out-of-band" information
- such as record lengths and possibly file attribute
- information, is converted to a universal canonical form.
- The specific content type of the body part as well as its
- associated attributes dictate the nature of the canonical
- form that is used. Conversion to the proper canonical form
- may involve character set conversion, transformation of
- audio data, compression, or various other operations
- specific to the various content types.
-
- For example, in the case of text/plain data, the text must
- be converted to a supported character set and lines must be
- delimited with CRLF delimiters in accordance with RFC822.
- Note that the restriction on line lengths implied by RFC822
- is eliminated if the next step employs either quoted-
- printable or base64 encoding.
-
- Step 3. Apply transfer encoding.
-
- A Content-Transfer-Encoding appropriate for this body part
- is applied. Note that there is no fixed relationship
- between the content type and the transfer encoding. In
- particular, it may be appropriate to base the choice of
- base64 or quoted-printable on character frequency counts
- which are specific to a given instance of body part.
-
-
-
- Borenstein & Freed [Page 73]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Step 4. Insertion into message.
-
- The encoded object is inserted into a MIME message with
- appropriate body part headers and boundary markers.
-
- It is vital to note that these steps are only a model; they
- are specifically NOT a blueprint for how an actual system
- would be built. In particular, the model fails to account
- for two common designs:
-
- 1. In many cases the conversion to a canonical
- form prior to encoding will be subsumed into the
- encoder itself, which understands local formats
- directly. For example, the local newline
- convention for text bodyparts might be carried
- through to the encoder itself along with knowledge
- of what that format is.
-
- 2. The output of the encoders may have to pass
- through one or more additional steps prior to
- being transmitted as a message. As such, the
- output of the encoder may not be compliant with
- the formats specified by RFC822. In particular,
- once again it may be appropriate for the
- converter's output to be expressed using local
- newline conventions rather than using the standard
- RFC822 CRLF delimiters.
-
- Other implementation variations are conceivable as well.
- The only important aspect of this discussion is that the
- resulting messages are consistent with those produced by the
- model described here.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Borenstein & Freed [Page 74]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- References
-
- [US-ASCII] Coded Character Set--7-Bit American Standard Code
- for Information Interchange, ANSI X3.4-1986.
-
- [ATK] Borenstein, Nathaniel S., Multimedia Applications
- Development with the Andrew Toolkit, Prentice-Hall, 1990.
-
- [GIF] Graphics Interchange Format (Version 89a), Compuserve,
- Inc., Columbus, Ohio, 1990.
-
- [ISO-2022] International Standard--Information Processing--
- ISO 7-bit and 8-bit coded character sets--Code extension
- techniques, ISO 2022:1986.
-
- [ISO-8859] Information Processing -- 8-bit Single-Byte Coded
- Graphic Character Sets -- Part 1: Latin Alphabet No. 1, ISO
- 8859-1:1987. Part 2: Latin alphabet No. 2, ISO 8859-2,
- 1987. Part 3: Latin alphabet No. 3, ISO 8859-3, 1988. Part
- 4: Latin alphabet No. 4, ISO 8859-4, 1988. Part 5:
- Latin/Cyrillic alphabet, ISO 8859-5, 1988. Part 6:
- Latin/Arabic alphabet, ISO 8859-6, 1987. Part 7:
- Latin/Greek alphabet, ISO 8859-7, 1987. Part 8:
- Latin/Hebrew alphabet, ISO 8859-8, 1988. Part 9: Latin
- alphabet No. 5, ISO 8859-9, 1990.
-
- [ISO-646] International Standard--Information Processing--
- ISO 7-bit coded character set for information interchange,
- ISO 646:1983.
-
- [MPEG] Video Coding Draft Standard ISO 11172 CD, ISO
- IEC/TJC1/SC2/WG11 (Motion Picture Experts Group), May, 1991.
-
- [ODA] ISO 8613; Information Processing: Text and Office
- System; Office Document Architecture (ODA) and Interchange
- Format (ODIF), Part 1-8, 1989.
-
- [PCM] CCITT, Fascicle III.4 - Recommendation G.711, Geneva,
- 1972, "Pulse Code Modulation (PCM) of Voice Frequencies".
-
- [POSTSCRIPT] Adobe Systems, Inc., PostScript Language
- Reference Manual, Addison-Wesley, 1985.
-
- [X400] Schicker, Pietro, "Message Handling Systems, X.400",
- Message Handling Systems and Distributed Applications, E.
- Stefferud, O-j. Jacobsen, and P. Schicker, eds., North-
- Holland, 1989, pp. 3-41.
-
- [RFC-783] Sollins, K.R. TFTP Protocol (revision 2). June,
- 1981, MIT, RFC-783.
-
- [RFC-821] Postel, J.B. Simple Mail Transfer Protocol.
- August, 1982, USC/Information Sciences Institute, RFC-821.
-
-
-
-
- Borenstein & Freed [Page 75]
-
-
-
-
- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- [RFC-822] Crocker, D. Standard for the format of ARPA
- Internet text messages. August, 1982, UDEL, RFC-822.
-
- [RFC-934] Rose, M.T.; Stefferud, E.A. Proposed standard
- for message encapsulation. January, 1985, Delaware
- and NMA, RFC-934.
-
- [RFC-959] Postel, J.B.; Reynolds, J.K. File Transfer
- Protocol. October, 1985, USC/Information Sciences
- Institute, RFC-959.
-
- [RFC-1049] Sirbu, M.A. Content-Type header field for
- Internet messages. March, 1988, CMU, RFC-1049.
-
- [RFC-1113] Linn, J. Privacy enhancement for Internet
- electronic mail: Part I - message encipherment and
- authentication procedures. August, 1989, IAB Privacy Task
- Force, RFC-1113.
-
- [RFC-1154] Robinson, D.; Ullmann, R. Encoding header field
- for Internet messages. April, 1990, Prime Computer,
- Inc., RFC-1154.
-
- [RFC-1342] Moore, Keith, Representation of Non-Ascii Text in
- Internet Message Headers. June, 1992, University of
- Tennessee, RFC-1342.
-
- Security Considerations
-
- Security issues are discussed in Section 7.4.2 and in
- Appendix G. Implementors should pay special attention to
- the security implications of any mail content-types that can
- cause the remote execution of any actions in the recipient's
- environment. In such cases, the discussion of the
- applicaton/postscript content-type in Section 7.4.2 may
- serve as a model for considering other content-types with
- remote execution capabilities.
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- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
-
-
- Authors' Addresses
-
- For more information, the authors of this document may be
- contacted via Internet mail:
-
- Nathaniel S. Borenstein
- MRE 2D-296, Bellcore
- 445 South St.
- Morristown, NJ 07962-1910
-
- Phone: +1 201 829 4270
- Fax: +1 201 829 7019
- Email: nsb@bellcore.com
-
-
- Ned Freed
- Innosoft International, Inc.
- 250 West First Street
- Suite 240
- Claremont, CA 91711
-
- Phone: +1 714 624 7907
- Fax: +1 714 621 5319
- Email: ned@innosoft.com
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- RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
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- Table of Contents
-
-
- 1 Introduction....................................... 1
- 2 Notations, Conventions, and Generic BNF Grammar.... 3
- 3 The MIME-Version Header Field...................... 5
- 4 The Content-Type Header Field...................... 6
- 5 The Content-Transfer-Encoding Header Field......... 10
- 5.1 Quoted-Printable Content-Transfer-Encoding......... 14
- 5.2 Base64 Content-Transfer-Encoding................... 17
- 6 Additional Optional Content- Header Fields......... 19
- 6.1 Optional Content-ID Header Field................... 19
- 6.2 Optional Content-Description Header Field.......... 19
- 7 The Predefined Content-Type Values................. 20
- 7.1 The Text Content-Type.............................. 20
- 7.1.1 The charset parameter.............................. 20
- 7.1.2 The Text/plain subtype............................. 23
- 7.1.3 The Text/richtext subtype.......................... 23
- 7.2 The Multipart Content-Type......................... 29
- 7.2.1 Multipart: The common syntax...................... 30
- 7.2.2 The Multipart/mixed (primary) subtype.............. 34
- 7.2.3 The Multipart/alternative subtype.................. 34
- 7.2.4 The Multipart/digest subtype....................... 36
- 7.2.5 The Multipart/parallel subtype..................... 36
- 7.3 The Message Content-Type........................... 37
- 7.3.1 The Message/rfc822 (primary) subtype............... 37
- 7.3.2 The Message/Partial subtype........................ 37
- 7.3.3 The Message/External-Body subtype.................. 40
- 7.4 The Application Content-Type....................... 46
- 7.4.1 The Application/Octet-Stream (primary) subtype..... 46
- 7.4.2 The Application/PostScript subtype................. 47
- 7.4.3 The Application/ODA subtype........................ 50
- 7.5 The Image Content-Type............................. 51
- 7.6 The Audio Content-Type............................. 51
- 7.7 The Video Content-Type............................. 51
- 7.8 Experimental Content-Type Values................... 51
- Summary............................................ 53
- Acknowledgements................................... 54
- Appendix A -- Minimal MIME-Conformance............. 56
- Appendix B -- General Guidelines For Sending Email Data59
- Appendix C -- A Complex Multipart Example.......... 62
- Appendix D -- A Simple Richtext-to-Text Translator in C64
- Appendix E -- Collected Grammar.................... 66
- Appendix F -- IANA Registration Procedures......... 68
- F.1 Registration of New Content-type/subtype Values..68
- F.2 Registration of New Character Set Values...... 69
- F.3 Registration of New Access-type Values for Message/external-body69
- F.4 Registration of New Conversions Values for Application69
- Appendix G -- Summary of the Seven Content-types... 71
- Appendix H -- Canonical Encoding Model............. 73
- References......................................... 75
- Security Considerations............................ 76
- Authors' Addresses................................. 77
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diff --git a/proto/rfc2045.txt b/proto/rfc2045.txt
@@ -1,1739 +0,0 @@
-
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-
-
-Network Working Group N. Freed
-Request for Comments: 2045 Innosoft
-Obsoletes: 1521, 1522, 1590 N. Borenstein
-Category: Standards Track First Virtual
- November 1996
-
-
- Multipurpose Internet Mail Extensions
- (MIME) Part One:
- Format of Internet Message Bodies
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- STD 11, RFC 822, defines a message representation protocol specifying
- considerable detail about US-ASCII message headers, and leaves the
- message content, or message body, as flat US-ASCII text. This set of
- documents, collectively called the Multipurpose Internet Mail
- Extensions, or MIME, redefines the format of messages to allow for
-
- (1) textual message bodies in character sets other than
- US-ASCII,
-
- (2) an extensible set of different formats for non-textual
- message bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than
- US-ASCII.
-
- These documents are based on earlier work documented in RFC 934, STD
- 11, and RFC 1049, but extends and revises them. Because RFC 822 said
- so little about message bodies, these documents are largely
- orthogonal to (rather than a revision of) RFC 822.
-
- This initial document specifies the various headers used to describe
- the structure of MIME messages. The second document, RFC 2046,
- defines the general structure of the MIME media typing system and
- defines an initial set of media types. The third document, RFC 2047,
- describes extensions to RFC 822 to allow non-US-ASCII text data in
-
-
-
-Freed & Borenstein Standards Track [Page 1]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- Internet mail header fields. The fourth document, RFC 2048, specifies
- various IANA registration procedures for MIME-related facilities. The
- fifth and final document, RFC 2049, describes MIME conformance
- criteria as well as providing some illustrative examples of MIME
- message formats, acknowledgements, and the bibliography.
-
- These documents are revisions of RFCs 1521, 1522, and 1590, which
- themselves were revisions of RFCs 1341 and 1342. An appendix in RFC
- 2049 describes differences and changes from previous versions.
-
-Table of Contents
-
- 1. Introduction ......................................... 3
- 2. Definitions, Conventions, and Generic BNF Grammar .... 5
- 2.1 CRLF ................................................ 5
- 2.2 Character Set ....................................... 6
- 2.3 Message ............................................. 6
- 2.4 Entity .............................................. 6
- 2.5 Body Part ........................................... 7
- 2.6 Body ................................................ 7
- 2.7 7bit Data ........................................... 7
- 2.8 8bit Data ........................................... 7
- 2.9 Binary Data ......................................... 7
- 2.10 Lines .............................................. 7
- 3. MIME Header Fields ................................... 8
- 4. MIME-Version Header Field ............................ 8
- 5. Content-Type Header Field ............................ 10
- 5.1 Syntax of the Content-Type Header Field ............. 12
- 5.2 Content-Type Defaults ............................... 14
- 6. Content-Transfer-Encoding Header Field ............... 14
- 6.1 Content-Transfer-Encoding Syntax .................... 14
- 6.2 Content-Transfer-Encodings Semantics ................ 15
- 6.3 New Content-Transfer-Encodings ...................... 16
- 6.4 Interpretation and Use .............................. 16
- 6.5 Translating Encodings ............................... 18
- 6.6 Canonical Encoding Model ............................ 19
- 6.7 Quoted-Printable Content-Transfer-Encoding .......... 19
- 6.8 Base64 Content-Transfer-Encoding .................... 24
- 7. Content-ID Header Field .............................. 26
- 8. Content-Description Header Field ..................... 27
- 9. Additional MIME Header Fields ........................ 27
- 10. Summary ............................................. 27
- 11. Security Considerations ............................. 27
- 12. Authors' Addresses .................................. 28
- A. Collected Grammar .................................... 29
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 2]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-1. Introduction
-
- Since its publication in 1982, RFC 822 has defined the standard
- format of textual mail messages on the Internet. Its success has
- been such that the RFC 822 format has been adopted, wholly or
- partially, well beyond the confines of the Internet and the Internet
- SMTP transport defined by RFC 821. As the format has seen wider use,
- a number of limitations have proven increasingly restrictive for the
- user community.
-
- RFC 822 was intended to specify a format for text messages. As such,
- non-text messages, such as multimedia messages that might include
- audio or images, are simply not mentioned. Even in the case of text,
- however, RFC 822 is inadequate for the needs of mail users whose
- languages require the use of character sets richer than US-ASCII.
- Since RFC 822 does not specify mechanisms for mail containing audio,
- video, Asian language text, or even text in most European languages,
- additional specifications are needed.
-
- One of the notable limitations of RFC 821/822 based mail systems is
- the fact that they limit the contents of electronic mail messages to
- relatively short lines (e.g. 1000 characters or less [RFC-821]) of
- 7bit US-ASCII. This forces users to convert any non-textual data
- that they may wish to send into seven-bit bytes representable as
- printable US-ASCII characters before invoking a local mail UA (User
- Agent, a program with which human users send and receive mail).
- Examples of such encodings currently used in the Internet include
- pure hexadecimal, uuencode, the 3-in-4 base 64 scheme specified in
- RFC 1421, the Andrew Toolkit Representation [ATK], and many others.
-
- The limitations of RFC 822 mail become even more apparent as gateways
- are designed to allow for the exchange of mail messages between RFC
- 822 hosts and X.400 hosts. X.400 [X400] specifies mechanisms for the
- inclusion of non-textual material within electronic mail messages.
- The current standards for the mapping of X.400 messages to RFC 822
- messages specify either that X.400 non-textual material must be
- converted to (not encoded in) IA5Text format, or that they must be
- discarded, notifying the RFC 822 user that discarding has occurred.
- This is clearly undesirable, as information that a user may wish to
- receive is lost. Even though a user agent may not have the
- capability of dealing with the non-textual material, the user might
- have some mechanism external to the UA that can extract useful
- information from the material. Moreover, it does not allow for the
- fact that the message may eventually be gatewayed back into an X.400
- message handling system (i.e., the X.400 message is "tunneled"
- through Internet mail), where the non-textual information would
- definitely become useful again.
-
-
-
-
-Freed & Borenstein Standards Track [Page 3]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- This document describes several mechanisms that combine to solve most
- of these problems without introducing any serious incompatibilities
- with the existing world of RFC 822 mail. In particular, it
- describes:
-
- (1) A MIME-Version header field, which uses a version
- number to declare a message to be conformant with MIME
- and allows mail processing agents to distinguish
- between such messages and those generated by older or
- non-conformant software, which are presumed to lack
- such a field.
-
- (2) A Content-Type header field, generalized from RFC 1049,
- which can be used to specify the media type and subtype
- of data in the body of a message and to fully specify
- the native representation (canonical form) of such
- data.
-
- (3) A Content-Transfer-Encoding header field, which can be
- used to specify both the encoding transformation that
- was applied to the body and the domain of the result.
- Encoding transformations other than the identity
- transformation are usually applied to data in order to
- allow it to pass through mail transport mechanisms
- which may have data or character set limitations.
-
- (4) Two additional header fields that can be used to
- further describe the data in a body, the Content-ID and
- Content-Description header fields.
-
- All of the header fields defined in this document are subject to the
- general syntactic rules for header fields specified in RFC 822. In
- particular, all of these header fields except for Content-Disposition
- can include RFC 822 comments, which have no semantic content and
- should be ignored during MIME processing.
-
- Finally, to specify and promote interoperability, RFC 2049 provides a
- basic applicability statement for a subset of the above mechanisms
- that defines a minimal level of "conformance" with this document.
-
- HISTORICAL NOTE: Several of the mechanisms described in this set of
- documents may seem somewhat strange or even baroque at first reading.
- It is important to note that compatibility with existing standards
- AND robustness across existing practice were two of the highest
- priorities of the working group that developed this set of documents.
- In particular, compatibility was always favored over elegance.
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 4]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- Please refer to the current edition of the "Internet Official
- Protocol Standards" for the standardization state and status of this
- protocol. RFC 822 and STD 3, RFC 1123 also provide essential
- background for MIME since no conforming implementation of MIME can
- violate them. In addition, several other informational RFC documents
- will be of interest to the MIME implementor, in particular RFC 1344,
- RFC 1345, and RFC 1524.
-
-2. Definitions, Conventions, and Generic BNF Grammar
-
- Although the mechanisms specified in this set of documents are all
- described in prose, most are also described formally in the augmented
- BNF notation of RFC 822. Implementors will need to be familiar with
- this notation in order to understand this set of documents, and are
- referred to RFC 822 for a complete explanation of the augmented BNF
- notation.
-
- Some of the augmented BNF in this set of documents makes named
- references to syntax rules defined in RFC 822. A complete formal
- grammar, then, is obtained by combining the collected grammar
- appendices in each document in this set with the BNF of RFC 822 plus
- the modifications to RFC 822 defined in RFC 1123 (which specifically
- changes the syntax for `return', `date' and `mailbox').
-
- All numeric and octet values are given in decimal notation in this
- set of documents. All media type values, subtype values, and
- parameter names as defined are case-insensitive. However, parameter
- values are case-sensitive unless otherwise specified for the specific
- parameter.
-
- FORMATTING NOTE: Notes, such at this one, provide additional
- nonessential information which may be skipped by the reader without
- missing anything essential. The primary purpose of these non-
- essential notes is to convey information about the rationale of this
- set of documents, or to place these documents in the proper
- historical or evolutionary context. Such information may in
- particular be skipped by those who are focused entirely on building a
- conformant implementation, but may be of use to those who wish to
- understand why certain design choices were made.
-
-2.1. CRLF
-
- The term CRLF, in this set of documents, refers to the sequence of
- octets corresponding to the two US-ASCII characters CR (decimal value
- 13) and LF (decimal value 10) which, taken together, in this order,
- denote a line break in RFC 822 mail.
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 5]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-2.2. Character Set
-
- The term "character set" is used in MIME to refer to a method of
- converting a sequence of octets into a sequence of characters. Note
- that unconditional and unambiguous conversion in the other direction
- is not required, in that not all characters may be representable by a
- given character set and a character set may provide more than one
- sequence of octets to represent a particular sequence of characters.
-
- This definition is intended to allow various kinds of character
- encodings, from simple single-table mappings such as US-ASCII to
- complex table switching methods such as those that use ISO 2022's
- techniques, to be used as character sets. However, the definition
- associated with a MIME character set name must fully specify the
- mapping to be performed. In particular, use of external profiling
- information to determine the exact mapping is not permitted.
-
- NOTE: The term "character set" was originally to describe such
- straightforward schemes as US-ASCII and ISO-8859-1 which have a
- simple one-to-one mapping from single octets to single characters.
- Multi-octet coded character sets and switching techniques make the
- situation more complex. For example, some communities use the term
- "character encoding" for what MIME calls a "character set", while
- using the phrase "coded character set" to denote an abstract mapping
- from integers (not octets) to characters.
-
-2.3. Message
-
- The term "message", when not further qualified, means either a
- (complete or "top-level") RFC 822 message being transferred on a
- network, or a message encapsulated in a body of type "message/rfc822"
- or "message/partial".
-
-2.4. Entity
-
- The term "entity", refers specifically to the MIME-defined header
- fields and contents of either a message or one of the parts in the
- body of a multipart entity. The specification of such entities is
- the essence of MIME. Since the contents of an entity are often
- called the "body", it makes sense to speak about the body of an
- entity. Any sort of field may be present in the header of an entity,
- but only those fields whose names begin with "content-" actually have
- any MIME-related meaning. Note that this does NOT imply thay they
- have no meaning at all -- an entity that is also a message has non-
- MIME header fields whose meanings are defined by RFC 822.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 6]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-2.5. Body Part
-
- The term "body part" refers to an entity inside of a multipart
- entity.
-
-2.6. Body
-
- The term "body", when not further qualified, means the body of an
- entity, that is, the body of either a message or of a body part.
-
- NOTE: The previous four definitions are clearly circular. This is
- unavoidable, since the overall structure of a MIME message is indeed
- recursive.
-
-2.7. 7bit Data
-
- "7bit data" refers to data that is all represented as relatively
- short lines with 998 octets or less between CRLF line separation
- sequences [RFC-821]. No octets with decimal values greater than 127
- are allowed and neither are NULs (octets with decimal value 0). CR
- (decimal value 13) and LF (decimal value 10) octets only occur as
- part of CRLF line separation sequences.
-
-2.8. 8bit Data
-
- "8bit data" refers to data that is all represented as relatively
- short lines with 998 octets or less between CRLF line separation
- sequences [RFC-821]), but octets with decimal values greater than 127
- may be used. As with "7bit data" CR and LF octets only occur as part
- of CRLF line separation sequences and no NULs are allowed.
-
-2.9. Binary Data
-
- "Binary data" refers to data where any sequence of octets whatsoever
- is allowed.
-
-2.10. Lines
-
- "Lines" are defined as sequences of octets separated by a CRLF
- sequences. This is consistent with both RFC 821 and RFC 822.
- "Lines" only refers to a unit of data in a message, which may or may
- not correspond to something that is actually displayed by a user
- agent.
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 7]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-3. MIME Header Fields
-
- MIME defines a number of new RFC 822 header fields that are used to
- describe the content of a MIME entity. These header fields occur in
- at least two contexts:
-
- (1) As part of a regular RFC 822 message header.
-
- (2) In a MIME body part header within a multipart
- construct.
-
- The formal definition of these header fields is as follows:
-
- entity-headers := [ content CRLF ]
- [ encoding CRLF ]
- [ id CRLF ]
- [ description CRLF ]
- *( MIME-extension-field CRLF )
-
- MIME-message-headers := entity-headers
- fields
- version CRLF
- ; The ordering of the header
- ; fields implied by this BNF
- ; definition should be ignored.
-
- MIME-part-headers := entity-headers
- [ fields ]
- ; Any field not beginning with
- ; "content-" can have no defined
- ; meaning and may be ignored.
- ; The ordering of the header
- ; fields implied by this BNF
- ; definition should be ignored.
-
- The syntax of the various specific MIME header fields will be
- described in the following sections.
-
-4. MIME-Version Header Field
-
- Since RFC 822 was published in 1982, there has really been only one
- format standard for Internet messages, and there has been little
- perceived need to declare the format standard in use. This document
- is an independent specification that complements RFC 822. Although
- the extensions in this document have been defined in such a way as to
- be compatible with RFC 822, there are still circumstances in which it
- might be desirable for a mail-processing agent to know whether a
- message was composed with the new standard in mind.
-
-
-
-Freed & Borenstein Standards Track [Page 8]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- Therefore, this document defines a new header field, "MIME-Version",
- which is to be used to declare the version of the Internet message
- body format standard in use.
-
- Messages composed in accordance with this document MUST include such
- a header field, with the following verbatim text:
-
- MIME-Version: 1.0
-
- The presence of this header field is an assertion that the message
- has been composed in compliance with this document.
-
- Since it is possible that a future document might extend the message
- format standard again, a formal BNF is given for the content of the
- MIME-Version field:
-
- version := "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
-
- Thus, future format specifiers, which might replace or extend "1.0",
- are constrained to be two integer fields, separated by a period. If
- a message is received with a MIME-version value other than "1.0", it
- cannot be assumed to conform with this document.
-
- Note that the MIME-Version header field is required at the top level
- of a message. It is not required for each body part of a multipart
- entity. It is required for the embedded headers of a body of type
- "message/rfc822" or "message/partial" if and only if the embedded
- message is itself claimed to be MIME-conformant.
-
- It is not possible to fully specify how a mail reader that conforms
- with MIME as defined in this document should treat a message that
- might arrive in the future with some value of MIME-Version other than
- "1.0".
-
- It is also worth noting that version control for specific media types
- is not accomplished using the MIME-Version mechanism. In particular,
- some formats (such as application/postscript) have version numbering
- conventions that are internal to the media format. Where such
- conventions exist, MIME does nothing to supersede them. Where no
- such conventions exist, a MIME media type might use a "version"
- parameter in the content-type field if necessary.
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 9]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- NOTE TO IMPLEMENTORS: When checking MIME-Version values any RFC 822
- comment strings that are present must be ignored. In particular, the
- following four MIME-Version fields are equivalent:
-
- MIME-Version: 1.0
-
- MIME-Version: 1.0 (produced by MetaSend Vx.x)
-
- MIME-Version: (produced by MetaSend Vx.x) 1.0
-
- MIME-Version: 1.(produced by MetaSend Vx.x)0
-
- In the absence of a MIME-Version field, a receiving mail user agent
- (whether conforming to MIME requirements or not) may optionally
- choose to interpret the body of the message according to local
- conventions. Many such conventions are currently in use and it
- should be noted that in practice non-MIME messages can contain just
- about anything.
-
- It is impossible to be certain that a non-MIME mail message is
- actually plain text in the US-ASCII character set since it might well
- be a message that, using some set of nonstandard local conventions
- that predate MIME, includes text in another character set or non-
- textual data presented in a manner that cannot be automatically
- recognized (e.g., a uuencoded compressed UNIX tar file).
-
-5. Content-Type Header Field
-
- The purpose of the Content-Type field is to describe the data
- contained in the body fully enough that the receiving user agent can
- pick an appropriate agent or mechanism to present the data to the
- user, or otherwise deal with the data in an appropriate manner. The
- value in this field is called a media type.
-
- HISTORICAL NOTE: The Content-Type header field was first defined in
- RFC 1049. RFC 1049 used a simpler and less powerful syntax, but one
- that is largely compatible with the mechanism given here.
-
- The Content-Type header field specifies the nature of the data in the
- body of an entity by giving media type and subtype identifiers, and
- by providing auxiliary information that may be required for certain
- media types. After the media type and subtype names, the remainder
- of the header field is simply a set of parameters, specified in an
- attribute=value notation. The ordering of parameters is not
- significant.
-
-
-
-
-
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-
- In general, the top-level media type is used to declare the general
- type of data, while the subtype specifies a specific format for that
- type of data. Thus, a media type of "image/xyz" is enough to tell a
- user agent that the data is an image, even if the user agent has no
- knowledge of the specific image format "xyz". Such information can
- be used, for example, to decide whether or not to show a user the raw
- data from an unrecognized subtype -- such an action might be
- reasonable for unrecognized subtypes of text, but not for
- unrecognized subtypes of image or audio. For this reason, registered
- subtypes of text, image, audio, and video should not contain embedded
- information that is really of a different type. Such compound
- formats should be represented using the "multipart" or "application"
- types.
-
- Parameters are modifiers of the media subtype, and as such do not
- fundamentally affect the nature of the content. The set of
- meaningful parameters depends on the media type and subtype. Most
- parameters are associated with a single specific subtype. However, a
- given top-level media type may define parameters which are applicable
- to any subtype of that type. Parameters may be required by their
- defining content type or subtype or they may be optional. MIME
- implementations must ignore any parameters whose names they do not
- recognize.
-
- For example, the "charset" parameter is applicable to any subtype of
- "text", while the "boundary" parameter is required for any subtype of
- the "multipart" media type.
-
- There are NO globally-meaningful parameters that apply to all media
- types. Truly global mechanisms are best addressed, in the MIME
- model, by the definition of additional Content-* header fields.
-
- An initial set of seven top-level media types is defined in RFC 2046.
- Five of these are discrete types whose content is essentially opaque
- as far as MIME processing is concerned. The remaining two are
- composite types whose contents require additional handling by MIME
- processors.
-
- This set of top-level media types is intended to be substantially
- complete. It is expected that additions to the larger set of
- supported types can generally be accomplished by the creation of new
- subtypes of these initial types. In the future, more top-level types
- may be defined only by a standards-track extension to this standard.
- If another top-level type is to be used for any reason, it must be
- given a name starting with "X-" to indicate its non-standard status
- and to avoid a potential conflict with a future official name.
-
-
-
-
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-
-5.1. Syntax of the Content-Type Header Field
-
- In the Augmented BNF notation of RFC 822, a Content-Type header field
- value is defined as follows:
-
- content := "Content-Type" ":" type "/" subtype
- *(";" parameter)
- ; Matching of media type and subtype
- ; is ALWAYS case-insensitive.
-
- type := discrete-type / composite-type
-
- discrete-type := "text" / "image" / "audio" / "video" /
- "application" / extension-token
-
- composite-type := "message" / "multipart" / extension-token
-
- extension-token := ietf-token / x-token
-
- ietf-token := <An extension token defined by a
- standards-track RFC and registered
- with IANA.>
-
- x-token := <The two characters "X-" or "x-" followed, with
- no intervening white space, by any token>
-
- subtype := extension-token / iana-token
-
- iana-token := <A publicly-defined extension token. Tokens
- of this form must be registered with IANA
- as specified in RFC 2048.>
-
- parameter := attribute "=" value
-
- attribute := token
- ; Matching of attributes
- ; is ALWAYS case-insensitive.
-
- value := token / quoted-string
-
- token := 1*<any (US-ASCII) CHAR except SPACE, CTLs,
- or tspecials>
-
- tspecials := "(" / ")" / "<" / ">" / "@" /
- "," / ";" / ":" / "\" / <">
- "/" / "[" / "]" / "?" / "="
- ; Must be in quoted-string,
- ; to use within parameter values
-
-
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-
-
- Note that the definition of "tspecials" is the same as the RFC 822
- definition of "specials" with the addition of the three characters
- "/", "?", and "=", and the removal of ".".
-
- Note also that a subtype specification is MANDATORY -- it may not be
- omitted from a Content-Type header field. As such, there are no
- default subtypes.
-
- The type, subtype, and parameter names are not case sensitive. For
- example, TEXT, Text, and TeXt are all equivalent top-level media
- types. Parameter values are normally case sensitive, but sometimes
- are interpreted in a case-insensitive fashion, depending on the
- intended use. (For example, multipart boundaries are case-sensitive,
- but the "access-type" parameter for message/External-body is not
- case-sensitive.)
-
- Note that the value of a quoted string parameter does not include the
- quotes. That is, the quotation marks in a quoted-string are not a
- part of the value of the parameter, but are merely used to delimit
- that parameter value. In addition, comments are allowed in
- accordance with RFC 822 rules for structured header fields. Thus the
- following two forms
-
- Content-type: text/plain; charset=us-ascii (Plain text)
-
- Content-type: text/plain; charset="us-ascii"
-
- are completely equivalent.
-
- Beyond this syntax, the only syntactic constraint on the definition
- of subtype names is the desire that their uses must not conflict.
- That is, it would be undesirable to have two different communities
- using "Content-Type: application/foobar" to mean two different
- things. The process of defining new media subtypes, then, is not
- intended to be a mechanism for imposing restrictions, but simply a
- mechanism for publicizing their definition and usage. There are,
- therefore, two acceptable mechanisms for defining new media subtypes:
-
- (1) Private values (starting with "X-") may be defined
- bilaterally between two cooperating agents without
- outside registration or standardization. Such values
- cannot be registered or standardized.
-
- (2) New standard values should be registered with IANA as
- described in RFC 2048.
-
- The second document in this set, RFC 2046, defines the initial set of
- media types for MIME.
-
-
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-
-
-5.2. Content-Type Defaults
-
- Default RFC 822 messages without a MIME Content-Type header are taken
- by this protocol to be plain text in the US-ASCII character set,
- which can be explicitly specified as:
-
- Content-type: text/plain; charset=us-ascii
-
- This default is assumed if no Content-Type header field is specified.
- It is also recommend that this default be assumed when a
- syntactically invalid Content-Type header field is encountered. In
- the presence of a MIME-Version header field and the absence of any
- Content-Type header field, a receiving User Agent can also assume
- that plain US-ASCII text was the sender's intent. Plain US-ASCII
- text may still be assumed in the absence of a MIME-Version or the
- presence of an syntactically invalid Content-Type header field, but
- the sender's intent might have been otherwise.
-
-6. Content-Transfer-Encoding Header Field
-
- Many media types which could be usefully transported via email are
- represented, in their "natural" format, as 8bit character or binary
- data. Such data cannot be transmitted over some transfer protocols.
- For example, RFC 821 (SMTP) restricts mail messages to 7bit US-ASCII
- data with lines no longer than 1000 characters including any trailing
- CRLF line separator.
-
- It is necessary, therefore, to define a standard mechanism for
- encoding such data into a 7bit short line format. Proper labelling
- of unencoded material in less restrictive formats for direct use over
- less restrictive transports is also desireable. This document
- specifies that such encodings will be indicated by a new "Content-
- Transfer-Encoding" header field. This field has not been defined by
- any previous standard.
-
-6.1. Content-Transfer-Encoding Syntax
-
- The Content-Transfer-Encoding field's value is a single token
- specifying the type of encoding, as enumerated below. Formally:
-
- encoding := "Content-Transfer-Encoding" ":" mechanism
-
- mechanism := "7bit" / "8bit" / "binary" /
- "quoted-printable" / "base64" /
- ietf-token / x-token
-
- These values are not case sensitive -- Base64 and BASE64 and bAsE64
- are all equivalent. An encoding type of 7BIT requires that the body
-
-
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-
- is already in a 7bit mail-ready representation. This is the default
- value -- that is, "Content-Transfer-Encoding: 7BIT" is assumed if the
- Content-Transfer-Encoding header field is not present.
-
-6.2. Content-Transfer-Encodings Semantics
-
- This single Content-Transfer-Encoding token actually provides two
- pieces of information. It specifies what sort of encoding
- transformation the body was subjected to and hence what decoding
- operation must be used to restore it to its original form, and it
- specifies what the domain of the result is.
-
- The transformation part of any Content-Transfer-Encodings specifies,
- either explicitly or implicitly, a single, well-defined decoding
- algorithm, which for any sequence of encoded octets either transforms
- it to the original sequence of octets which was encoded, or shows
- that it is illegal as an encoded sequence. Content-Transfer-
- Encodings transformations never depend on any additional external
- profile information for proper operation. Note that while decoders
- must produce a single, well-defined output for a valid encoding no
- such restrictions exist for encoders: Encoding a given sequence of
- octets to different, equivalent encoded sequences is perfectly legal.
-
- Three transformations are currently defined: identity, the "quoted-
- printable" encoding, and the "base64" encoding. The domains are
- "binary", "8bit" and "7bit".
-
- The Content-Transfer-Encoding values "7bit", "8bit", and "binary" all
- mean that the identity (i.e. NO) encoding transformation has been
- performed. As such, they serve simply as indicators of the domain of
- the body data, and provide useful information about the sort of
- encoding that might be needed for transmission in a given transport
- system. The terms "7bit data", "8bit data", and "binary data" are
- all defined in Section 2.
-
- The quoted-printable and base64 encodings transform their input from
- an arbitrary domain into material in the "7bit" range, thus making it
- safe to carry over restricted transports. The specific definition of
- the transformations are given below.
-
- The proper Content-Transfer-Encoding label must always be used.
- Labelling unencoded data containing 8bit characters as "7bit" is not
- allowed, nor is labelling unencoded non-line-oriented data as
- anything other than "binary" allowed.
-
- Unlike media subtypes, a proliferation of Content-Transfer-Encoding
- values is both undesirable and unnecessary. However, establishing
- only a single transformation into the "7bit" domain does not seem
-
-
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-
-
- possible. There is a tradeoff between the desire for a compact and
- efficient encoding of largely- binary data and the desire for a
- somewhat readable encoding of data that is mostly, but not entirely,
- 7bit. For this reason, at least two encoding mechanisms are
- necessary: a more or less readable encoding (quoted-printable) and a
- "dense" or "uniform" encoding (base64).
-
- Mail transport for unencoded 8bit data is defined in RFC 1652. As of
- the initial publication of this document, there are no standardized
- Internet mail transports for which it is legitimate to include
- unencoded binary data in mail bodies. Thus there are no
- circumstances in which the "binary" Content-Transfer-Encoding is
- actually valid in Internet mail. However, in the event that binary
- mail transport becomes a reality in Internet mail, or when MIME is
- used in conjunction with any other binary-capable mail transport
- mechanism, binary bodies must be labelled as such using this
- mechanism.
-
- NOTE: The five values defined for the Content-Transfer-Encoding field
- imply nothing about the media type other than the algorithm by which
- it was encoded or the transport system requirements if unencoded.
-
-6.3. New Content-Transfer-Encodings
-
- Implementors may, if necessary, define private Content-Transfer-
- Encoding values, but must use an x-token, which is a name prefixed by
- "X-", to indicate its non-standard status, e.g., "Content-Transfer-
- Encoding: x-my-new-encoding". Additional standardized Content-
- Transfer-Encoding values must be specified by a standards-track RFC.
- The requirements such specifications must meet are given in RFC 2048.
- As such, all content-transfer-encoding namespace except that
- beginning with "X-" is explicitly reserved to the IETF for future
- use.
-
- Unlike media types and subtypes, the creation of new Content-
- Transfer-Encoding values is STRONGLY discouraged, as it seems likely
- to hinder interoperability with little potential benefit
-
-6.4. Interpretation and Use
-
- If a Content-Transfer-Encoding header field appears as part of a
- message header, it applies to the entire body of that message. If a
- Content-Transfer-Encoding header field appears as part of an entity's
- headers, it applies only to the body of that entity. If an entity is
- of type "multipart" the Content-Transfer-Encoding is not permitted to
- have any value other than "7bit", "8bit" or "binary". Even more
- severe restrictions apply to some subtypes of the "message" type.
-
-
-
-
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-
-
- It should be noted that most media types are defined in terms of
- octets rather than bits, so that the mechanisms described here are
- mechanisms for encoding arbitrary octet streams, not bit streams. If
- a bit stream is to be encoded via one of these mechanisms, it must
- first be converted to an 8bit byte stream using the network standard
- bit order ("big-endian"), in which the earlier bits in a stream
- become the higher-order bits in a 8bit byte. A bit stream not ending
- at an 8bit boundary must be padded with zeroes. RFC 2046 provides a
- mechanism for noting the addition of such padding in the case of the
- application/octet-stream media type, which has a "padding" parameter.
-
- The encoding mechanisms defined here explicitly encode all data in
- US-ASCII. Thus, for example, suppose an entity has header fields
- such as:
-
- Content-Type: text/plain; charset=ISO-8859-1
- Content-transfer-encoding: base64
-
- This must be interpreted to mean that the body is a base64 US-ASCII
- encoding of data that was originally in ISO-8859-1, and will be in
- that character set again after decoding.
-
- Certain Content-Transfer-Encoding values may only be used on certain
- media types. In particular, it is EXPRESSLY FORBIDDEN to use any
- encodings other than "7bit", "8bit", or "binary" with any composite
- media type, i.e. one that recursively includes other Content-Type
- fields. Currently the only composite media types are "multipart" and
- "message". All encodings that are desired for bodies of type
- multipart or message must be done at the innermost level, by encoding
- the actual body that needs to be encoded.
-
- It should also be noted that, by definition, if a composite entity
- has a transfer-encoding value such as "7bit", but one of the enclosed
- entities has a less restrictive value such as "8bit", then either the
- outer "7bit" labelling is in error, because 8bit data are included,
- or the inner "8bit" labelling placed an unnecessarily high demand on
- the transport system because the actual included data were actually
- 7bit-safe.
-
- NOTE ON ENCODING RESTRICTIONS: Though the prohibition against using
- content-transfer-encodings on composite body data may seem overly
- restrictive, it is necessary to prevent nested encodings, in which
- data are passed through an encoding algorithm multiple times, and
- must be decoded multiple times in order to be properly viewed.
- Nested encodings add considerable complexity to user agents: Aside
- from the obvious efficiency problems with such multiple encodings,
- they can obscure the basic structure of a message. In particular,
- they can imply that several decoding operations are necessary simply
-
-
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-
-
- to find out what types of bodies a message contains. Banning nested
- encodings may complicate the job of certain mail gateways, but this
- seems less of a problem than the effect of nested encodings on user
- agents.
-
- Any entity with an unrecognized Content-Transfer-Encoding must be
- treated as if it has a Content-Type of "application/octet-stream",
- regardless of what the Content-Type header field actually says.
-
- NOTE ON THE RELATIONSHIP BETWEEN CONTENT-TYPE AND CONTENT-TRANSFER-
- ENCODING: It may seem that the Content-Transfer-Encoding could be
- inferred from the characteristics of the media that is to be encoded,
- or, at the very least, that certain Content-Transfer-Encodings could
- be mandated for use with specific media types. There are several
- reasons why this is not the case. First, given the varying types of
- transports used for mail, some encodings may be appropriate for some
- combinations of media types and transports but not for others. (For
- example, in an 8bit transport, no encoding would be required for text
- in certain character sets, while such encodings are clearly required
- for 7bit SMTP.)
-
- Second, certain media types may require different types of transfer
- encoding under different circumstances. For example, many PostScript
- bodies might consist entirely of short lines of 7bit data and hence
- require no encoding at all. Other PostScript bodies (especially
- those using Level 2 PostScript's binary encoding mechanism) may only
- be reasonably represented using a binary transport encoding.
- Finally, since the Content-Type field is intended to be an open-ended
- specification mechanism, strict specification of an association
- between media types and encodings effectively couples the
- specification of an application protocol with a specific lower-level
- transport. This is not desirable since the developers of a media
- type should not have to be aware of all the transports in use and
- what their limitations are.
-
-6.5. Translating Encodings
-
- The quoted-printable and base64 encodings are designed so that
- conversion between them is possible. The only issue that arises in
- such a conversion is the handling of hard line breaks in quoted-
- printable encoding output. When converting from quoted-printable to
- base64 a hard line break in the quoted-printable form represents a
- CRLF sequence in the canonical form of the data. It must therefore be
- converted to a corresponding encoded CRLF in the base64 form of the
- data. Similarly, a CRLF sequence in the canonical form of the data
- obtained after base64 decoding must be converted to a quoted-
- printable hard line break, but ONLY when converting text data.
-
-
-
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-
-
-6.6. Canonical Encoding Model
-
- There was some confusion, in the previous versions of this RFC,
- regarding the model for when email data was to be converted to
- canonical form and encoded, and in particular how this process would
- affect the treatment of CRLFs, given that the representation of
- newlines varies greatly from system to system, and the relationship
- between content-transfer-encodings and character sets. A canonical
- model for encoding is presented in RFC 2049 for this reason.
-
-6.7. Quoted-Printable Content-Transfer-Encoding
-
- The Quoted-Printable encoding is intended to represent data that
- largely consists of octets that correspond to printable characters in
- the US-ASCII character set. It encodes the data in such a way that
- the resulting octets are unlikely to be modified by mail transport.
- If the data being encoded are mostly US-ASCII text, the encoded form
- of the data remains largely recognizable by humans. A body which is
- entirely US-ASCII may also be encoded in Quoted-Printable to ensure
- the integrity of the data should the message pass through a
- character-translating, and/or line-wrapping gateway.
-
- In this encoding, octets are to be represented as determined by the
- following rules:
-
- (1) (General 8bit representation) Any octet, except a CR or
- LF that is part of a CRLF line break of the canonical
- (standard) form of the data being encoded, may be
- represented by an "=" followed by a two digit
- hexadecimal representation of the octet's value. The
- digits of the hexadecimal alphabet, for this purpose,
- are "0123456789ABCDEF". Uppercase letters must be
- used; lowercase letters are not allowed. Thus, for
- example, the decimal value 12 (US-ASCII form feed) can
- be represented by "=0C", and the decimal value 61 (US-
- ASCII EQUAL SIGN) can be represented by "=3D". This
- rule must be followed except when the following rules
- allow an alternative encoding.
-
- (2) (Literal representation) Octets with decimal values of
- 33 through 60 inclusive, and 62 through 126, inclusive,
- MAY be represented as the US-ASCII characters which
- correspond to those octets (EXCLAMATION POINT through
- LESS THAN, and GREATER THAN through TILDE,
- respectively).
-
- (3) (White Space) Octets with values of 9 and 32 MAY be
- represented as US-ASCII TAB (HT) and SPACE characters,
-
-
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-
-
- respectively, but MUST NOT be so represented at the end
- of an encoded line. Any TAB (HT) or SPACE characters
- on an encoded line MUST thus be followed on that line
- by a printable character. In particular, an "=" at the
- end of an encoded line, indicating a soft line break
- (see rule #5) may follow one or more TAB (HT) or SPACE
- characters. It follows that an octet with decimal
- value 9 or 32 appearing at the end of an encoded line
- must be represented according to Rule #1. This rule is
- necessary because some MTAs (Message Transport Agents,
- programs which transport messages from one user to
- another, or perform a portion of such transfers) are
- known to pad lines of text with SPACEs, and others are
- known to remove "white space" characters from the end
- of a line. Therefore, when decoding a Quoted-Printable
- body, any trailing white space on a line must be
- deleted, as it will necessarily have been added by
- intermediate transport agents.
-
- (4) (Line Breaks) A line break in a text body, represented
- as a CRLF sequence in the text canonical form, must be
- represented by a (RFC 822) line break, which is also a
- CRLF sequence, in the Quoted-Printable encoding. Since
- the canonical representation of media types other than
- text do not generally include the representation of
- line breaks as CRLF sequences, no hard line breaks
- (i.e. line breaks that are intended to be meaningful
- and to be displayed to the user) can occur in the
- quoted-printable encoding of such types. Sequences
- like "=0D", "=0A", "=0A=0D" and "=0D=0A" will routinely
- appear in non-text data represented in quoted-
- printable, of course.
-
- Note that many implementations may elect to encode the
- local representation of various content types directly
- rather than converting to canonical form first,
- encoding, and then converting back to local
- representation. In particular, this may apply to plain
- text material on systems that use newline conventions
- other than a CRLF terminator sequence. Such an
- implementation optimization is permissible, but only
- when the combined canonicalization-encoding step is
- equivalent to performing the three steps separately.
-
- (5) (Soft Line Breaks) The Quoted-Printable encoding
- REQUIRES that encoded lines be no more than 76
- characters long. If longer lines are to be encoded
- with the Quoted-Printable encoding, "soft" line breaks
-
-
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-
-
- must be used. An equal sign as the last character on a
- encoded line indicates such a non-significant ("soft")
- line break in the encoded text.
-
- Thus if the "raw" form of the line is a single unencoded line that
- says:
-
- Now's the time for all folk to come to the aid of their country.
-
- This can be represented, in the Quoted-Printable encoding, as:
-
- Now's the time =
- for all folk to come=
- to the aid of their country.
-
- This provides a mechanism with which long lines are encoded in such a
- way as to be restored by the user agent. The 76 character limit does
- not count the trailing CRLF, but counts all other characters,
- including any equal signs.
-
- Since the hyphen character ("-") may be represented as itself in the
- Quoted-Printable encoding, care must be taken, when encapsulating a
- quoted-printable encoded body inside one or more multipart entities,
- to ensure that the boundary delimiter does not appear anywhere in the
- encoded body. (A good strategy is to choose a boundary that includes
- a character sequence such as "=_" which can never appear in a
- quoted-printable body. See the definition of multipart messages in
- RFC 2046.)
-
- NOTE: The quoted-printable encoding represents something of a
- compromise between readability and reliability in transport. Bodies
- encoded with the quoted-printable encoding will work reliably over
- most mail gateways, but may not work perfectly over a few gateways,
- notably those involving translation into EBCDIC. A higher level of
- confidence is offered by the base64 Content-Transfer-Encoding. A way
- to get reasonably reliable transport through EBCDIC gateways is to
- also quote the US-ASCII characters
-
- !"#$@[\]^`{|}~
-
- according to rule #1.
-
- Because quoted-printable data is generally assumed to be line-
- oriented, it is to be expected that the representation of the breaks
- between the lines of quoted-printable data may be altered in
- transport, in the same manner that plain text mail has always been
- altered in Internet mail when passing between systems with differing
- newline conventions. If such alterations are likely to constitute a
-
-
-
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-
-
- corruption of the data, it is probably more sensible to use the
- base64 encoding rather than the quoted-printable encoding.
-
- NOTE: Several kinds of substrings cannot be generated according to
- the encoding rules for the quoted-printable content-transfer-
- encoding, and hence are formally illegal if they appear in the output
- of a quoted-printable encoder. This note enumerates these cases and
- suggests ways to handle such illegal substrings if any are
- encountered in quoted-printable data that is to be decoded.
-
- (1) An "=" followed by two hexadecimal digits, one or both
- of which are lowercase letters in "abcdef", is formally
- illegal. A robust implementation might choose to
- recognize them as the corresponding uppercase letters.
-
- (2) An "=" followed by a character that is neither a
- hexadecimal digit (including "abcdef") nor the CR
- character of a CRLF pair is illegal. This case can be
- the result of US-ASCII text having been included in a
- quoted-printable part of a message without itself
- having been subjected to quoted-printable encoding. A
- reasonable approach by a robust implementation might be
- to include the "=" character and the following
- character in the decoded data without any
- transformation and, if possible, indicate to the user
- that proper decoding was not possible at this point in
- the data.
-
- (3) An "=" cannot be the ultimate or penultimate character
- in an encoded object. This could be handled as in case
- (2) above.
-
- (4) Control characters other than TAB, or CR and LF as
- parts of CRLF pairs, must not appear. The same is true
- for octets with decimal values greater than 126. If
- found in incoming quoted-printable data by a decoder, a
- robust implementation might exclude them from the
- decoded data and warn the user that illegal characters
- were discovered.
-
- (5) Encoded lines must not be longer than 76 characters,
- not counting the trailing CRLF. If longer lines are
- found in incoming, encoded data, a robust
- implementation might nevertheless decode the lines, and
- might report the erroneous encoding to the user.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 22]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- WARNING TO IMPLEMENTORS: If binary data is encoded in quoted-
- printable, care must be taken to encode CR and LF characters as "=0D"
- and "=0A", respectively. In particular, a CRLF sequence in binary
- data should be encoded as "=0D=0A". Otherwise, if CRLF were
- represented as a hard line break, it might be incorrectly decoded on
- platforms with different line break conventions.
-
- For formalists, the syntax of quoted-printable data is described by
- the following grammar:
-
- quoted-printable := qp-line *(CRLF qp-line)
-
- qp-line := *(qp-segment transport-padding CRLF)
- qp-part transport-padding
-
- qp-part := qp-section
- ; Maximum length of 76 characters
-
- qp-segment := qp-section *(SPACE / TAB) "="
- ; Maximum length of 76 characters
-
- qp-section := [*(ptext / SPACE / TAB) ptext]
-
- ptext := hex-octet / safe-char
-
- safe-char := <any octet with decimal value of 33 through
- 60 inclusive, and 62 through 126>
- ; Characters not listed as "mail-safe" in
- ; RFC 2049 are also not recommended.
-
- hex-octet := "=" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
- ; Octet must be used for characters > 127, =,
- ; SPACEs or TABs at the ends of lines, and is
- ; recommended for any character not listed in
- ; RFC 2049 as "mail-safe".
-
- transport-padding := *LWSP-char
- ; Composers MUST NOT generate
- ; non-zero length transport
- ; padding, but receivers MUST
- ; be able to handle padding
- ; added by message transports.
-
- IMPORTANT: The addition of LWSP between the elements shown in this
- BNF is NOT allowed since this BNF does not specify a structured
- header field.
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 23]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-6.8. Base64 Content-Transfer-Encoding
-
- The Base64 Content-Transfer-Encoding is designed to represent
- arbitrary sequences of octets in a form that need not be humanly
- readable. The encoding and decoding algorithms are simple, but the
- encoded data are consistently only about 33 percent larger than the
- unencoded data. This encoding is virtually identical to the one used
- in Privacy Enhanced Mail (PEM) applications, as defined in RFC 1421.
-
- A 65-character subset of US-ASCII is used, enabling 6 bits to be
- represented per printable character. (The extra 65th character, "=",
- is used to signify a special processing function.)
-
- NOTE: This subset has the important property that it is represented
- identically in all versions of ISO 646, including US-ASCII, and all
- characters in the subset are also represented identically in all
- versions of EBCDIC. Other popular encodings, such as the encoding
- used by the uuencode utility, Macintosh binhex 4.0 [RFC-1741], and
- the base85 encoding specified as part of Level 2 PostScript, do not
- share these properties, and thus do not fulfill the portability
- requirements a binary transport encoding for mail must meet.
-
- The encoding process represents 24-bit groups of input bits as output
- strings of 4 encoded characters. Proceeding from left to right, a
- 24-bit input group is formed by concatenating 3 8bit input groups.
- These 24 bits are then treated as 4 concatenated 6-bit groups, each
- of which is translated into a single digit in the base64 alphabet.
- When encoding a bit stream via the base64 encoding, the bit stream
- must be presumed to be ordered with the most-significant-bit first.
- That is, the first bit in the stream will be the high-order bit in
- the first 8bit byte, and the eighth bit will be the low-order bit in
- the first 8bit byte, and so on.
-
- Each 6-bit group is used as an index into an array of 64 printable
- characters. The character referenced by the index is placed in the
- output string. These characters, identified in Table 1, below, are
- selected so as to be universally representable, and the set excludes
- characters with particular significance to SMTP (e.g., ".", CR, LF)
- and to the multipart boundary delimiters defined in RFC 2046 (e.g.,
- "-").
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 24]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- Table 1: The Base64 Alphabet
-
- Value Encoding Value Encoding Value Encoding Value Encoding
- 0 A 17 R 34 i 51 z
- 1 B 18 S 35 j 52 0
- 2 C 19 T 36 k 53 1
- 3 D 20 U 37 l 54 2
- 4 E 21 V 38 m 55 3
- 5 F 22 W 39 n 56 4
- 6 G 23 X 40 o 57 5
- 7 H 24 Y 41 p 58 6
- 8 I 25 Z 42 q 59 7
- 9 J 26 a 43 r 60 8
- 10 K 27 b 44 s 61 9
- 11 L 28 c 45 t 62 +
- 12 M 29 d 46 u 63 /
- 13 N 30 e 47 v
- 14 O 31 f 48 w (pad) =
- 15 P 32 g 49 x
- 16 Q 33 h 50 y
-
- The encoded output stream must be represented in lines of no more
- than 76 characters each. All line breaks or other characters not
- found in Table 1 must be ignored by decoding software. In base64
- data, characters other than those in Table 1, line breaks, and other
- white space probably indicate a transmission error, about which a
- warning message or even a message rejection might be appropriate
- under some circumstances.
-
- Special processing is performed if fewer than 24 bits are available
- at the end of the data being encoded. A full encoding quantum is
- always completed at the end of a body. When fewer than 24 input bits
- are available in an input group, zero bits are added (on the right)
- to form an integral number of 6-bit groups. Padding at the end of
- the data is performed using the "=" character. Since all base64
- input is an integral number of octets, only the following cases can
- arise: (1) the final quantum of encoding input is an integral
- multiple of 24 bits; here, the final unit of encoded output will be
- an integral multiple of 4 characters with no "=" padding, (2) the
- final quantum of encoding input is exactly 8 bits; here, the final
- unit of encoded output will be two characters followed by two "="
- padding characters, or (3) the final quantum of encoding input is
- exactly 16 bits; here, the final unit of encoded output will be three
- characters followed by one "=" padding character.
-
- Because it is used only for padding at the end of the data, the
- occurrence of any "=" characters may be taken as evidence that the
- end of the data has been reached (without truncation in transit). No
-
-
-
-Freed & Borenstein Standards Track [Page 25]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- such assurance is possible, however, when the number of octets
- transmitted was a multiple of three and no "=" characters are
- present.
-
- Any characters outside of the base64 alphabet are to be ignored in
- base64-encoded data.
-
- Care must be taken to use the proper octets for line breaks if base64
- encoding is applied directly to text material that has not been
- converted to canonical form. In particular, text line breaks must be
- converted into CRLF sequences prior to base64 encoding. The
- important thing to note is that this may be done directly by the
- encoder rather than in a prior canonicalization step in some
- implementations.
-
- NOTE: There is no need to worry about quoting potential boundary
- delimiters within base64-encoded bodies within multipart entities
- because no hyphen characters are used in the base64 encoding.
-
-7. Content-ID Header Field
-
- In constructing a high-level user agent, it may be desirable to allow
- one body to make reference to another. Accordingly, bodies may be
- labelled using the "Content-ID" header field, which is syntactically
- identical to the "Message-ID" header field:
-
- id := "Content-ID" ":" msg-id
-
- Like the Message-ID values, Content-ID values must be generated to be
- world-unique.
-
- The Content-ID value may be used for uniquely identifying MIME
- entities in several contexts, particularly for caching data
- referenced by the message/external-body mechanism. Although the
- Content-ID header is generally optional, its use is MANDATORY in
- implementations which generate data of the optional MIME media type
- "message/external-body". That is, each message/external-body entity
- must have a Content-ID field to permit caching of such data.
-
- It is also worth noting that the Content-ID value has special
- semantics in the case of the multipart/alternative media type. This
- is explained in the section of RFC 2046 dealing with
- multipart/alternative.
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 26]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-8. Content-Description Header Field
-
- The ability to associate some descriptive information with a given
- body is often desirable. For example, it may be useful to mark an
- "image" body as "a picture of the Space Shuttle Endeavor." Such text
- may be placed in the Content-Description header field. This header
- field is always optional.
-
- description := "Content-Description" ":" *text
-
- The description is presumed to be given in the US-ASCII character
- set, although the mechanism specified in RFC 2047 may be used for
- non-US-ASCII Content-Description values.
-
-9. Additional MIME Header Fields
-
- Future documents may elect to define additional MIME header fields
- for various purposes. Any new header field that further describes
- the content of a message should begin with the string "Content-" to
- allow such fields which appear in a message header to be
- distinguished from ordinary RFC 822 message header fields.
-
- MIME-extension-field := <Any RFC 822 header field which
- begins with the string
- "Content-">
-
-10. Summary
-
- Using the MIME-Version, Content-Type, and Content-Transfer-Encoding
- header fields, it is possible to include, in a standardized way,
- arbitrary types of data with RFC 822 conformant mail messages. No
- restrictions imposed by either RFC 821 or RFC 822 are violated, and
- care has been taken to avoid problems caused by additional
- restrictions imposed by the characteristics of some Internet mail
- transport mechanisms (see RFC 2049).
-
- The next document in this set, RFC 2046, specifies the initial set of
- media types that can be labelled and transported using these headers.
-
-11. Security Considerations
-
- Security issues are discussed in the second document in this set, RFC
- 2046.
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 27]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-12. Authors' Addresses
-
- For more information, the authors of this document are best contacted
- via Internet mail:
-
- Ned Freed
- Innosoft International, Inc.
- 1050 East Garvey Avenue South
- West Covina, CA 91790
- USA
-
- Phone: +1 818 919 3600
- Fax: +1 818 919 3614
- EMail: ned@innosoft.com
-
-
- Nathaniel S. Borenstein
- First Virtual Holdings
- 25 Washington Avenue
- Morristown, NJ 07960
- USA
-
- Phone: +1 201 540 8967
- Fax: +1 201 993 3032
- EMail: nsb@nsb.fv.com
-
-
- MIME is a result of the work of the Internet Engineering Task Force
- Working Group on RFC 822 Extensions. The chairman of that group,
- Greg Vaudreuil, may be reached at:
-
- Gregory M. Vaudreuil
- Octel Network Services
- 17080 Dallas Parkway
- Dallas, TX 75248-1905
- USA
-
- EMail: Greg.Vaudreuil@Octel.Com
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 28]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
-Appendix A -- Collected Grammar
-
- This appendix contains the complete BNF grammar for all the syntax
- specified by this document.
-
- By itself, however, this grammar is incomplete. It refers by name to
- several syntax rules that are defined by RFC 822. Rather than
- reproduce those definitions here, and risk unintentional differences
- between the two, this document simply refers the reader to RFC 822
- for the remaining definitions. Wherever a term is undefined, it
- refers to the RFC 822 definition.
-
- attribute := token
- ; Matching of attributes
- ; is ALWAYS case-insensitive.
-
- composite-type := "message" / "multipart" / extension-token
-
- content := "Content-Type" ":" type "/" subtype
- *(";" parameter)
- ; Matching of media type and subtype
- ; is ALWAYS case-insensitive.
-
- description := "Content-Description" ":" *text
-
- discrete-type := "text" / "image" / "audio" / "video" /
- "application" / extension-token
-
- encoding := "Content-Transfer-Encoding" ":" mechanism
-
- entity-headers := [ content CRLF ]
- [ encoding CRLF ]
- [ id CRLF ]
- [ description CRLF ]
- *( MIME-extension-field CRLF )
-
- extension-token := ietf-token / x-token
-
- hex-octet := "=" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
- ; Octet must be used for characters > 127, =,
- ; SPACEs or TABs at the ends of lines, and is
- ; recommended for any character not listed in
- ; RFC 2049 as "mail-safe".
-
- iana-token := <A publicly-defined extension token. Tokens
- of this form must be registered with IANA
- as specified in RFC 2048.>
-
-
-
-
-Freed & Borenstein Standards Track [Page 29]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- ietf-token := <An extension token defined by a
- standards-track RFC and registered
- with IANA.>
-
- id := "Content-ID" ":" msg-id
-
- mechanism := "7bit" / "8bit" / "binary" /
- "quoted-printable" / "base64" /
- ietf-token / x-token
-
- MIME-extension-field := <Any RFC 822 header field which
- begins with the string
- "Content-">
-
- MIME-message-headers := entity-headers
- fields
- version CRLF
- ; The ordering of the header
- ; fields implied by this BNF
- ; definition should be ignored.
-
- MIME-part-headers := entity-headers
- [fields]
- ; Any field not beginning with
- ; "content-" can have no defined
- ; meaning and may be ignored.
- ; The ordering of the header
- ; fields implied by this BNF
- ; definition should be ignored.
-
- parameter := attribute "=" value
-
- ptext := hex-octet / safe-char
-
- qp-line := *(qp-segment transport-padding CRLF)
- qp-part transport-padding
-
- qp-part := qp-section
- ; Maximum length of 76 characters
-
- qp-section := [*(ptext / SPACE / TAB) ptext]
-
- qp-segment := qp-section *(SPACE / TAB) "="
- ; Maximum length of 76 characters
-
- quoted-printable := qp-line *(CRLF qp-line)
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 30]
-
-RFC 2045 Internet Message Bodies November 1996
-
-
- safe-char := <any octet with decimal value of 33 through
- 60 inclusive, and 62 through 126>
- ; Characters not listed as "mail-safe" in
- ; RFC 2049 are also not recommended.
-
- subtype := extension-token / iana-token
-
- token := 1*<any (US-ASCII) CHAR except SPACE, CTLs,
- or tspecials>
-
- transport-padding := *LWSP-char
- ; Composers MUST NOT generate
- ; non-zero length transport
- ; padding, but receivers MUST
- ; be able to handle padding
- ; added by message transports.
-
- tspecials := "(" / ")" / "<" / ">" / "@" /
- "," / ";" / ":" / "\" / <">
- "/" / "[" / "]" / "?" / "="
- ; Must be in quoted-string,
- ; to use within parameter values
-
- type := discrete-type / composite-type
-
- value := token / quoted-string
-
- version := "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
-
- x-token := <The two characters "X-" or "x-" followed, with
- no intervening white space, by any token>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 31]
-
diff --git a/proto/rfc2046.txt b/proto/rfc2046.txt
@@ -1,2467 +0,0 @@
-
-
-
-
-
-
-Network Working Group N. Freed
-Request for Comments: 2046 Innosoft
-Obsoletes: 1521, 1522, 1590 N. Borenstein
-Category: Standards Track First Virtual
- November 1996
-
-
- Multipurpose Internet Mail Extensions
- (MIME) Part Two:
- Media Types
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- STD 11, RFC 822 defines a message representation protocol specifying
- considerable detail about US-ASCII message headers, but which leaves
- the message content, or message body, as flat US-ASCII text. This
- set of documents, collectively called the Multipurpose Internet Mail
- Extensions, or MIME, redefines the format of messages to allow for
-
- (1) textual message bodies in character sets other than
- US-ASCII,
-
- (2) an extensible set of different formats for non-textual
- message bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than
- US-ASCII.
-
- These documents are based on earlier work documented in RFC 934, STD
- 11, and RFC 1049, but extends and revises them. Because RFC 822 said
- so little about message bodies, these documents are largely
- orthogonal to (rather than a revision of) RFC 822.
-
- The initial document in this set, RFC 2045, specifies the various
- headers used to describe the structure of MIME messages. This second
- document defines the general structure of the MIME media typing
- system and defines an initial set of media types. The third document,
- RFC 2047, describes extensions to RFC 822 to allow non-US-ASCII text
-
-
-
-Freed & Borenstein Standards Track [Page 1]
-
-RFC 2046 Media Types November 1996
-
-
- data in Internet mail header fields. The fourth document, RFC 2048,
- specifies various IANA registration procedures for MIME-related
- facilities. The fifth and final document, RFC 2049, describes MIME
- conformance criteria as well as providing some illustrative examples
- of MIME message formats, acknowledgements, and the bibliography.
-
- These documents are revisions of RFCs 1521 and 1522, which themselves
- were revisions of RFCs 1341 and 1342. An appendix in RFC 2049
- describes differences and changes from previous versions.
-
-Table of Contents
-
- 1. Introduction ......................................... 3
- 2. Definition of a Top-Level Media Type ................. 4
- 3. Overview Of The Initial Top-Level Media Types ........ 4
- 4. Discrete Media Type Values ........................... 6
- 4.1 Text Media Type ..................................... 6
- 4.1.1 Representation of Line Breaks ..................... 7
- 4.1.2 Charset Parameter ................................. 7
- 4.1.3 Plain Subtype ..................................... 11
- 4.1.4 Unrecognized Subtypes ............................. 11
- 4.2 Image Media Type .................................... 11
- 4.3 Audio Media Type .................................... 11
- 4.4 Video Media Type .................................... 12
- 4.5 Application Media Type .............................. 12
- 4.5.1 Octet-Stream Subtype .............................. 13
- 4.5.2 PostScript Subtype ................................ 14
- 4.5.3 Other Application Subtypes ........................ 17
- 5. Composite Media Type Values .......................... 17
- 5.1 Multipart Media Type ................................ 17
- 5.1.1 Common Syntax ..................................... 19
- 5.1.2 Handling Nested Messages and Multiparts ........... 24
- 5.1.3 Mixed Subtype ..................................... 24
- 5.1.4 Alternative Subtype ............................... 24
- 5.1.5 Digest Subtype .................................... 26
- 5.1.6 Parallel Subtype .................................. 27
- 5.1.7 Other Multipart Subtypes .......................... 28
- 5.2 Message Media Type .................................. 28
- 5.2.1 RFC822 Subtype .................................... 28
- 5.2.2 Partial Subtype ................................... 29
- 5.2.2.1 Message Fragmentation and Reassembly ............ 30
- 5.2.2.2 Fragmentation and Reassembly Example ............ 31
- 5.2.3 External-Body Subtype ............................. 33
- 5.2.4 Other Message Subtypes ............................ 40
- 6. Experimental Media Type Values ....................... 40
- 7. Summary .............................................. 41
- 8. Security Considerations .............................. 41
- 9. Authors' Addresses ................................... 42
-
-
-
-Freed & Borenstein Standards Track [Page 2]
-
-RFC 2046 Media Types November 1996
-
-
- A. Collected Grammar .................................... 43
-
-1. Introduction
-
- The first document in this set, RFC 2045, defines a number of header
- fields, including Content-Type. The Content-Type field is used to
- specify the nature of the data in the body of a MIME entity, by
- giving media type and subtype identifiers, and by providing auxiliary
- information that may be required for certain media types. After the
- type and subtype names, the remainder of the header field is simply a
- set of parameters, specified in an attribute/value notation. The
- ordering of parameters is not significant.
-
- In general, the top-level media type is used to declare the general
- type of data, while the subtype specifies a specific format for that
- type of data. Thus, a media type of "image/xyz" is enough to tell a
- user agent that the data is an image, even if the user agent has no
- knowledge of the specific image format "xyz". Such information can
- be used, for example, to decide whether or not to show a user the raw
- data from an unrecognized subtype -- such an action might be
- reasonable for unrecognized subtypes of "text", but not for
- unrecognized subtypes of "image" or "audio". For this reason,
- registered subtypes of "text", "image", "audio", and "video" should
- not contain embedded information that is really of a different type.
- Such compound formats should be represented using the "multipart" or
- "application" types.
-
- Parameters are modifiers of the media subtype, and as such do not
- fundamentally affect the nature of the content. The set of
- meaningful parameters depends on the media type and subtype. Most
- parameters are associated with a single specific subtype. However, a
- given top-level media type may define parameters which are applicable
- to any subtype of that type. Parameters may be required by their
- defining media type or subtype or they may be optional. MIME
- implementations must also ignore any parameters whose names they do
- not recognize.
-
- MIME's Content-Type header field and media type mechanism has been
- carefully designed to be extensible, and it is expected that the set
- of media type/subtype pairs and their associated parameters will grow
- significantly over time. Several other MIME facilities, such as
- transfer encodings and "message/external-body" access types, are
- likely to have new values defined over time. In order to ensure that
- the set of such values is developed in an orderly, well-specified,
- and public manner, MIME sets up a registration process which uses the
- Internet Assigned Numbers Authority (IANA) as a central registry for
- MIME's various areas of extensibility. The registration process for
- these areas is described in a companion document, RFC 2048.
-
-
-
-Freed & Borenstein Standards Track [Page 3]
-
-RFC 2046 Media Types November 1996
-
-
- The initial seven standard top-level media type are defined and
- described in the remainder of this document.
-
-2. Definition of a Top-Level Media Type
-
- The definition of a top-level media type consists of:
-
- (1) a name and a description of the type, including
- criteria for whether a particular type would qualify
- under that type,
-
- (2) the names and definitions of parameters, if any, which
- are defined for all subtypes of that type (including
- whether such parameters are required or optional),
-
- (3) how a user agent and/or gateway should handle unknown
- subtypes of this type,
-
- (4) general considerations on gatewaying entities of this
- top-level type, if any, and
-
- (5) any restrictions on content-transfer-encodings for
- entities of this top-level type.
-
-3. Overview Of The Initial Top-Level Media Types
-
- The five discrete top-level media types are:
-
- (1) text -- textual information. The subtype "plain" in
- particular indicates plain text containing no
- formatting commands or directives of any sort. Plain
- text is intended to be displayed "as-is". No special
- software is required to get the full meaning of the
- text, aside from support for the indicated character
- set. Other subtypes are to be used for enriched text in
- forms where application software may enhance the
- appearance of the text, but such software must not be
- required in order to get the general idea of the
- content. Possible subtypes of "text" thus include any
- word processor format that can be read without
- resorting to software that understands the format. In
- particular, formats that employ embeddded binary
- formatting information are not considered directly
- readable. A very simple and portable subtype,
- "richtext", was defined in RFC 1341, with a further
- revision in RFC 1896 under the name "enriched".
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 4]
-
-RFC 2046 Media Types November 1996
-
-
- (2) image -- image data. "Image" requires a display device
- (such as a graphical display, a graphics printer, or a
- FAX machine) to view the information. An initial
- subtype is defined for the widely-used image format
- JPEG. . subtypes are defined for two widely-used image
- formats, jpeg and gif.
-
- (3) audio -- audio data. "Audio" requires an audio output
- device (such as a speaker or a telephone) to "display"
- the contents. An initial subtype "basic" is defined in
- this document.
-
- (4) video -- video data. "Video" requires the capability
- to display moving images, typically including
- specialized hardware and software. An initial subtype
- "mpeg" is defined in this document.
-
- (5) application -- some other kind of data, typically
- either uninterpreted binary data or information to be
- processed by an application. The subtype "octet-
- stream" is to be used in the case of uninterpreted
- binary data, in which case the simplest recommended
- action is to offer to write the information into a file
- for the user. The "PostScript" subtype is also defined
- for the transport of PostScript material. Other
- expected uses for "application" include spreadsheets,
- data for mail-based scheduling systems, and languages
- for "active" (computational) messaging, and word
- processing formats that are not directly readable.
- Note that security considerations may exist for some
- types of application data, most notably
- "application/PostScript" and any form of active
- messaging. These issues are discussed later in this
- document.
-
- The two composite top-level media types are:
-
- (1) multipart -- data consisting of multiple entities of
- independent data types. Four subtypes are initially
- defined, including the basic "mixed" subtype specifying
- a generic mixed set of parts, "alternative" for
- representing the same data in multiple formats,
- "parallel" for parts intended to be viewed
- simultaneously, and "digest" for multipart entities in
- which each part has a default type of "message/rfc822".
-
-
-
-
-
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-
-
- (2) message -- an encapsulated message. A body of media
- type "message" is itself all or a portion of some kind
- of message object. Such objects may or may not in turn
- contain other entities. The "rfc822" subtype is used
- when the encapsulated content is itself an RFC 822
- message. The "partial" subtype is defined for partial
- RFC 822 messages, to permit the fragmented transmission
- of bodies that are thought to be too large to be passed
- through transport facilities in one piece. Another
- subtype, "external-body", is defined for specifying
- large bodies by reference to an external data source.
-
- It should be noted that the list of media type values given here may
- be augmented in time, via the mechanisms described above, and that
- the set of subtypes is expected to grow substantially.
-
-4. Discrete Media Type Values
-
- Five of the seven initial media type values refer to discrete bodies.
- The content of these types must be handled by non-MIME mechanisms;
- they are opaque to MIME processors.
-
-4.1. Text Media Type
-
- The "text" media type is intended for sending material which is
- principally textual in form. A "charset" parameter may be used to
- indicate the character set of the body text for "text" subtypes,
- notably including the subtype "text/plain", which is a generic
- subtype for plain text. Plain text does not provide for or allow
- formatting commands, font attribute specifications, processing
- instructions, interpretation directives, or content markup. Plain
- text is seen simply as a linear sequence of characters, possibly
- interrupted by line breaks or page breaks. Plain text may allow the
- stacking of several characters in the same position in the text.
- Plain text in scripts like Arabic and Hebrew may also include
- facilitites that allow the arbitrary mixing of text segments with
- opposite writing directions.
-
- Beyond plain text, there are many formats for representing what might
- be known as "rich text". An interesting characteristic of many such
- representations is that they are to some extent readable even without
- the software that interprets them. It is useful, then, to
- distinguish them, at the highest level, from such unreadable data as
- images, audio, or text represented in an unreadable form. In the
- absence of appropriate interpretation software, it is reasonable to
- show subtypes of "text" to the user, while it is not reasonable to do
- so with most nontextual data. Such formatted textual data should be
- represented using subtypes of "text".
-
-
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-
-
-4.1.1. Representation of Line Breaks
-
- The canonical form of any MIME "text" subtype MUST always represent a
- line break as a CRLF sequence. Similarly, any occurrence of CRLF in
- MIME "text" MUST represent a line break. Use of CR and LF outside of
- line break sequences is also forbidden.
-
- This rule applies regardless of format or character set or sets
- involved.
-
- NOTE: The proper interpretation of line breaks when a body is
- displayed depends on the media type. In particular, while it is
- appropriate to treat a line break as a transition to a new line when
- displaying a "text/plain" body, this treatment is actually incorrect
- for other subtypes of "text" like "text/enriched" [RFC-1896].
- Similarly, whether or not line breaks should be added during display
- operations is also a function of the media type. It should not be
- necessary to add any line breaks to display "text/plain" correctly,
- whereas proper display of "text/enriched" requires the appropriate
- addition of line breaks.
-
- NOTE: Some protocols defines a maximum line length. E.g. SMTP [RFC-
- 821] allows a maximum of 998 octets before the next CRLF sequence.
- To be transported by such protocols, data which includes too long
- segments without CRLF sequences must be encoded with a suitable
- content-transfer-encoding.
-
-4.1.2. Charset Parameter
-
- A critical parameter that may be specified in the Content-Type field
- for "text/plain" data is the character set. This is specified with a
- "charset" parameter, as in:
-
- Content-type: text/plain; charset=iso-8859-1
-
- Unlike some other parameter values, the values of the charset
- parameter are NOT case sensitive. The default character set, which
- must be assumed in the absence of a charset parameter, is US-ASCII.
-
- The specification for any future subtypes of "text" must specify
- whether or not they will also utilize a "charset" parameter, and may
- possibly restrict its values as well. For other subtypes of "text"
- than "text/plain", the semantics of the "charset" parameter should be
- defined to be identical to those specified here for "text/plain",
- i.e., the body consists entirely of characters in the given charset.
- In particular, definers of future "text" subtypes should pay close
- attention to the implications of multioctet character sets for their
- subtype definitions.
-
-
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-
- The charset parameter for subtypes of "text" gives a name of a
- character set, as "character set" is defined in RFC 2045. The rules
- regarding line breaks detailed in the previous section must also be
- observed -- a character set whose definition does not conform to
- these rules cannot be used in a MIME "text" subtype.
-
- An initial list of predefined character set names can be found at the
- end of this section. Additional character sets may be registered
- with IANA.
-
- Other media types than subtypes of "text" might choose to employ the
- charset parameter as defined here, but with the CRLF/line break
- restriction removed. Therefore, all character sets that conform to
- the general definition of "character set" in RFC 2045 can be
- registered for MIME use.
-
- Note that if the specified character set includes 8-bit characters
- and such characters are used in the body, a Content-Transfer-Encoding
- header field and a corresponding encoding on the data are required in
- order to transmit the body via some mail transfer protocols, such as
- SMTP [RFC-821].
-
- The default character set, US-ASCII, has been the subject of some
- confusion and ambiguity in the past. Not only were there some
- ambiguities in the definition, there have been wide variations in
- practice. In order to eliminate such ambiguity and variations in the
- future, it is strongly recommended that new user agents explicitly
- specify a character set as a media type parameter in the Content-Type
- header field. "US-ASCII" does not indicate an arbitrary 7-bit
- character set, but specifies that all octets in the body must be
- interpreted as characters according to the US-ASCII character set.
- National and application-oriented versions of ISO 646 [ISO-646] are
- usually NOT identical to US-ASCII, and in that case their use in
- Internet mail is explicitly discouraged. The omission of the ISO 646
- character set from this document is deliberate in this regard. The
- character set name of "US-ASCII" explicitly refers to the character
- set defined in ANSI X3.4-1986 [US- ASCII]. The new international
- reference version (IRV) of the 1991 edition of ISO 646 is identical
- to US-ASCII. The character set name "ASCII" is reserved and must not
- be used for any purpose.
-
- NOTE: RFC 821 explicitly specifies "ASCII", and references an earlier
- version of the American Standard. Insofar as one of the purposes of
- specifying a media type and character set is to permit the receiver
- to unambiguously determine how the sender intended the coded message
- to be interpreted, assuming anything other than "strict ASCII" as the
- default would risk unintentional and incompatible changes to the
- semantics of messages now being transmitted. This also implies that
-
-
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-
-
- messages containing characters coded according to other versions of
- ISO 646 than US-ASCII and the 1991 IRV, or using code-switching
- procedures (e.g., those of ISO 2022), as well as 8bit or multiple
- octet character encodings MUST use an appropriate character set
- specification to be consistent with MIME.
-
- The complete US-ASCII character set is listed in ANSI X3.4- 1986.
- Note that the control characters including DEL (0-31, 127) have no
- defined meaning in apart from the combination CRLF (US-ASCII values
- 13 and 10) indicating a new line. Two of the characters have de
- facto meanings in wide use: FF (12) often means "start subsequent
- text on the beginning of a new page"; and TAB or HT (9) often (though
- not always) means "move the cursor to the next available column after
- the current position where the column number is a multiple of 8
- (counting the first column as column 0)." Aside from these
- conventions, any use of the control characters or DEL in a body must
- either occur
-
- (1) because a subtype of text other than "plain"
- specifically assigns some additional meaning, or
-
- (2) within the context of a private agreement between the
- sender and recipient. Such private agreements are
- discouraged and should be replaced by the other
- capabilities of this document.
-
- NOTE: An enormous proliferation of character sets exist beyond US-
- ASCII. A large number of partially or totally overlapping character
- sets is NOT a good thing. A SINGLE character set that can be used
- universally for representing all of the world's languages in Internet
- mail would be preferrable. Unfortunately, existing practice in
- several communities seems to point to the continued use of multiple
- character sets in the near future. A small number of standard
- character sets are, therefore, defined for Internet use in this
- document.
-
- The defined charset values are:
-
- (1) US-ASCII -- as defined in ANSI X3.4-1986 [US-ASCII].
-
- (2) ISO-8859-X -- where "X" is to be replaced, as
- necessary, for the parts of ISO-8859 [ISO-8859]. Note
- that the ISO 646 character sets have deliberately been
- omitted in favor of their 8859 replacements, which are
- the designated character sets for Internet mail. As of
- the publication of this document, the legitimate values
- for "X" are the digits 1 through 10.
-
-
-
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-
-
- Characters in the range 128-159 has no assigned meaning in ISO-8859-
- X. Characters with values below 128 in ISO-8859-X have the same
- assigned meaning as they do in US-ASCII.
-
- Part 6 of ISO 8859 (Latin/Arabic alphabet) and part 8 (Latin/Hebrew
- alphabet) includes both characters for which the normal writing
- direction is right to left and characters for which it is left to
- right, but do not define a canonical ordering method for representing
- bi-directional text. The charset values "ISO-8859-6" and "ISO-8859-
- 8", however, specify that the visual method is used [RFC-1556].
-
- All of these character sets are used as pure 7bit or 8bit sets
- without any shift or escape functions. The meaning of shift and
- escape sequences in these character sets is not defined.
-
- The character sets specified above are the ones that were relatively
- uncontroversial during the drafting of MIME. This document does not
- endorse the use of any particular character set other than US-ASCII,
- and recognizes that the future evolution of world character sets
- remains unclear.
-
- Note that the character set used, if anything other than US- ASCII,
- must always be explicitly specified in the Content-Type field.
-
- No character set name other than those defined above may be used in
- Internet mail without the publication of a formal specification and
- its registration with IANA, or by private agreement, in which case
- the character set name must begin with "X-".
-
- Implementors are discouraged from defining new character sets unless
- absolutely necessary.
-
- The "charset" parameter has been defined primarily for the purpose of
- textual data, and is described in this section for that reason.
- However, it is conceivable that non-textual data might also wish to
- specify a charset value for some purpose, in which case the same
- syntax and values should be used.
-
- In general, composition software should always use the "lowest common
- denominator" character set possible. For example, if a body contains
- only US-ASCII characters, it SHOULD be marked as being in the US-
- ASCII character set, not ISO-8859-1, which, like all the ISO-8859
- family of character sets, is a superset of US-ASCII. More generally,
- if a widely-used character set is a subset of another character set,
- and a body contains only characters in the widely-used subset, it
- should be labelled as being in that subset. This will increase the
- chances that the recipient will be able to view the resulting entity
- correctly.
-
-
-
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-
-
-4.1.3. Plain Subtype
-
- The simplest and most important subtype of "text" is "plain". This
- indicates plain text that does not contain any formatting commands or
- directives. Plain text is intended to be displayed "as-is", that is,
- no interpretation of embedded formatting commands, font attribute
- specifications, processing instructions, interpretation directives,
- or content markup should be necessary for proper display. The
- default media type of "text/plain; charset=us-ascii" for Internet
- mail describes existing Internet practice. That is, it is the type
- of body defined by RFC 822.
-
- No other "text" subtype is defined by this document.
-
-4.1.4. Unrecognized Subtypes
-
- Unrecognized subtypes of "text" should be treated as subtype "plain"
- as long as the MIME implementation knows how to handle the charset.
- Unrecognized subtypes which also specify an unrecognized charset
- should be treated as "application/octet- stream".
-
-4.2. Image Media Type
-
- A media type of "image" indicates that the body contains an image.
- The subtype names the specific image format. These names are not
- case sensitive. An initial subtype is "jpeg" for the JPEG format
- using JFIF encoding [JPEG].
-
- The list of "image" subtypes given here is neither exclusive nor
- exhaustive, and is expected to grow as more types are registered with
- IANA, as described in RFC 2048.
-
- Unrecognized subtypes of "image" should at a miniumum be treated as
- "application/octet-stream". Implementations may optionally elect to
- pass subtypes of "image" that they do not specifically recognize to a
- secure and robust general-purpose image viewing application, if such
- an application is available.
-
- NOTE: Using of a generic-purpose image viewing application this way
- inherits the security problems of the most dangerous type supported
- by the application.
-
-4.3. Audio Media Type
-
- A media type of "audio" indicates that the body contains audio data.
- Although there is not yet a consensus on an "ideal" audio format for
- use with computers, there is a pressing need for a format capable of
- providing interoperable behavior.
-
-
-
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-
-
- The initial subtype of "basic" is specified to meet this requirement
- by providing an absolutely minimal lowest common denominator audio
- format. It is expected that richer formats for higher quality and/or
- lower bandwidth audio will be defined by a later document.
-
- The content of the "audio/basic" subtype is single channel audio
- encoded using 8bit ISDN mu-law [PCM] at a sample rate of 8000 Hz.
-
- Unrecognized subtypes of "audio" should at a miniumum be treated as
- "application/octet-stream". Implementations may optionally elect to
- pass subtypes of "audio" that they do not specifically recognize to a
- robust general-purpose audio playing application, if such an
- application is available.
-
-4.4. Video Media Type
-
- A media type of "video" indicates that the body contains a time-
- varying-picture image, possibly with color and coordinated sound.
- The term 'video' is used in its most generic sense, rather than with
- reference to any particular technology or format, and is not meant to
- preclude subtypes such as animated drawings encoded compactly. The
- subtype "mpeg" refers to video coded according to the MPEG standard
- [MPEG].
-
- Note that although in general this document strongly discourages the
- mixing of multiple media in a single body, it is recognized that many
- so-called video formats include a representation for synchronized
- audio, and this is explicitly permitted for subtypes of "video".
-
- Unrecognized subtypes of "video" should at a minumum be treated as
- "application/octet-stream". Implementations may optionally elect to
- pass subtypes of "video" that they do not specifically recognize to a
- robust general-purpose video display application, if such an
- application is available.
-
-4.5. Application Media Type
-
- The "application" media type is to be used for discrete data which do
- not fit in any of the other categories, and particularly for data to
- be processed by some type of application program. This is
- information which must be processed by an application before it is
- viewable or usable by a user. Expected uses for the "application"
- media type include file transfer, spreadsheets, data for mail-based
- scheduling systems, and languages for "active" (computational)
- material. (The latter, in particular, can pose security problems
- which must be understood by implementors, and are considered in
- detail in the discussion of the "application/PostScript" media type.)
-
-
-
-
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-
-
- For example, a meeting scheduler might define a standard
- representation for information about proposed meeting dates. An
- intelligent user agent would use this information to conduct a dialog
- with the user, and might then send additional material based on that
- dialog. More generally, there have been several "active" messaging
- languages developed in which programs in a suitably specialized
- language are transported to a remote location and automatically run
- in the recipient's environment.
-
- Such applications may be defined as subtypes of the "application"
- media type. This document defines two subtypes:
-
- octet-stream, and PostScript.
-
- The subtype of "application" will often be either the name or include
- part of the name of the application for which the data are intended.
- This does not mean, however, that any application program name may be
- used freely as a subtype of "application".
-
-4.5.1. Octet-Stream Subtype
-
- The "octet-stream" subtype is used to indicate that a body contains
- arbitrary binary data. The set of currently defined parameters is:
-
- (1) TYPE -- the general type or category of binary data.
- This is intended as information for the human recipient
- rather than for any automatic processing.
-
- (2) PADDING -- the number of bits of padding that were
- appended to the bit-stream comprising the actual
- contents to produce the enclosed 8bit byte-oriented
- data. This is useful for enclosing a bit-stream in a
- body when the total number of bits is not a multiple of
- 8.
-
- Both of these parameters are optional.
-
- An additional parameter, "CONVERSIONS", was defined in RFC 1341 but
- has since been removed. RFC 1341 also defined the use of a "NAME"
- parameter which gave a suggested file name to be used if the data
- were to be written to a file. This has been deprecated in
- anticipation of a separate Content-Disposition header field, to be
- defined in a subsequent RFC.
-
- The recommended action for an implementation that receives an
- "application/octet-stream" entity is to simply offer to put the data
- in a file, with any Content-Transfer-Encoding undone, or perhaps to
- use it as input to a user-specified process.
-
-
-
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-
-
- To reduce the danger of transmitting rogue programs, it is strongly
- recommended that implementations NOT implement a path-search
- mechanism whereby an arbitrary program named in the Content-Type
- parameter (e.g., an "interpreter=" parameter) is found and executed
- using the message body as input.
-
-4.5.2. PostScript Subtype
-
- A media type of "application/postscript" indicates a PostScript
- program. Currently two variants of the PostScript language are
- allowed; the original level 1 variant is described in [POSTSCRIPT]
- and the more recent level 2 variant is described in [POSTSCRIPT2].
-
- PostScript is a registered trademark of Adobe Systems, Inc. Use of
- the MIME media type "application/postscript" implies recognition of
- that trademark and all the rights it entails.
-
- The PostScript language definition provides facilities for internal
- labelling of the specific language features a given program uses.
- This labelling, called the PostScript document structuring
- conventions, or DSC, is very general and provides substantially more
- information than just the language level. The use of document
- structuring conventions, while not required, is strongly recommended
- as an aid to interoperability. Documents which lack proper
- structuring conventions cannot be tested to see whether or not they
- will work in a given environment. As such, some systems may assume
- the worst and refuse to process unstructured documents.
-
- The execution of general-purpose PostScript interpreters entails
- serious security risks, and implementors are discouraged from simply
- sending PostScript bodies to "off- the-shelf" interpreters. While it
- is usually safe to send PostScript to a printer, where the potential
- for harm is greatly constrained by typical printer environments,
- implementors should consider all of the following before they add
- interactive display of PostScript bodies to their MIME readers.
-
- The remainder of this section outlines some, though probably not all,
- of the possible problems with the transport of PostScript entities.
-
- (1) Dangerous operations in the PostScript language
- include, but may not be limited to, the PostScript
- operators "deletefile", "renamefile", "filenameforall",
- and "file". "File" is only dangerous when applied to
- something other than standard input or output.
- Implementations may also define additional nonstandard
- file operators; these may also pose a threat to
- security. "Filenameforall", the wildcard file search
- operator, may appear at first glance to be harmless.
-
-
-
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-
-
- Note, however, that this operator has the potential to
- reveal information about what files the recipient has
- access to, and this information may itself be
- sensitive. Message senders should avoid the use of
- potentially dangerous file operators, since these
- operators are quite likely to be unavailable in secure
- PostScript implementations. Message receiving and
- displaying software should either completely disable
- all potentially dangerous file operators or take
- special care not to delegate any special authority to
- their operation. These operators should be viewed as
- being done by an outside agency when interpreting
- PostScript documents. Such disabling and/or checking
- should be done completely outside of the reach of the
- PostScript language itself; care should be taken to
- insure that no method exists for re-enabling full-
- function versions of these operators.
-
- (2) The PostScript language provides facilities for exiting
- the normal interpreter, or server, loop. Changes made
- in this "outer" environment are customarily retained
- across documents, and may in some cases be retained
- semipermanently in nonvolatile memory. The operators
- associated with exiting the interpreter loop have the
- potential to interfere with subsequent document
- processing. As such, their unrestrained use
- constitutes a threat of service denial. PostScript
- operators that exit the interpreter loop include, but
- may not be limited to, the exitserver and startjob
- operators. Message sending software should not
- generate PostScript that depends on exiting the
- interpreter loop to operate, since the ability to exit
- will probably be unavailable in secure PostScript
- implementations. Message receiving and displaying
- software should completely disable the ability to make
- retained changes to the PostScript environment by
- eliminating or disabling the "startjob" and
- "exitserver" operations. If these operations cannot be
- eliminated or completely disabled the password
- associated with them should at least be set to a hard-
- to-guess value.
-
- (3) PostScript provides operators for setting system-wide
- and device-specific parameters. These parameter
- settings may be retained across jobs and may
- potentially pose a threat to the correct operation of
- the interpreter. The PostScript operators that set
- system and device parameters include, but may not be
-
-
-
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-RFC 2046 Media Types November 1996
-
-
- limited to, the "setsystemparams" and "setdevparams"
- operators. Message sending software should not
- generate PostScript that depends on the setting of
- system or device parameters to operate correctly. The
- ability to set these parameters will probably be
- unavailable in secure PostScript implementations.
- Message receiving and displaying software should
- disable the ability to change system and device
- parameters. If these operators cannot be completely
- disabled the password associated with them should at
- least be set to a hard-to-guess value.
-
- (4) Some PostScript implementations provide nonstandard
- facilities for the direct loading and execution of
- machine code. Such facilities are quite obviously open
- to substantial abuse. Message sending software should
- not make use of such features. Besides being totally
- hardware-specific, they are also likely to be
- unavailable in secure implementations of PostScript.
- Message receiving and displaying software should not
- allow such operators to be used if they exist.
-
- (5) PostScript is an extensible language, and many, if not
- most, implementations of it provide a number of their
- own extensions. This document does not deal with such
- extensions explicitly since they constitute an unknown
- factor. Message sending software should not make use
- of nonstandard extensions; they are likely to be
- missing from some implementations. Message receiving
- and displaying software should make sure that any
- nonstandard PostScript operators are secure and don't
- present any kind of threat.
-
- (6) It is possible to write PostScript that consumes huge
- amounts of various system resources. It is also
- possible to write PostScript programs that loop
- indefinitely. Both types of programs have the
- potential to cause damage if sent to unsuspecting
- recipients. Message-sending software should avoid the
- construction and dissemination of such programs, which
- is antisocial. Message receiving and displaying
- software should provide appropriate mechanisms to abort
- processing after a reasonable amount of time has
- elapsed. In addition, PostScript interpreters should be
- limited to the consumption of only a reasonable amount
- of any given system resource.
-
-
-
-
-
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-
-
- (7) It is possible to include raw binary information inside
- PostScript in various forms. This is not recommended
- for use in Internet mail, both because it is not
- supported by all PostScript interpreters and because it
- significantly complicates the use of a MIME Content-
- Transfer-Encoding. (Without such binary, PostScript
- may typically be viewed as line-oriented data. The
- treatment of CRLF sequences becomes extremely
- problematic if binary and line-oriented data are mixed
- in a single Postscript data stream.)
-
- (8) Finally, bugs may exist in some PostScript interpreters
- which could possibly be exploited to gain unauthorized
- access to a recipient's system. Apart from noting this
- possibility, there is no specific action to take to
- prevent this, apart from the timely correction of such
- bugs if any are found.
-
-4.5.3. Other Application Subtypes
-
- It is expected that many other subtypes of "application" will be
- defined in the future. MIME implementations must at a minimum treat
- any unrecognized subtypes as being equivalent to "application/octet-
- stream".
-
-5. Composite Media Type Values
-
- The remaining two of the seven initial Content-Type values refer to
- composite entities. Composite entities are handled using MIME
- mechanisms -- a MIME processor typically handles the body directly.
-
-5.1. Multipart Media Type
-
- In the case of multipart entities, in which one or more different
- sets of data are combined in a single body, a "multipart" media type
- field must appear in the entity's header. The body must then contain
- one or more body parts, each preceded by a boundary delimiter line,
- and the last one followed by a closing boundary delimiter line.
- After its boundary delimiter line, each body part then consists of a
- header area, a blank line, and a body area. Thus a body part is
- similar to an RFC 822 message in syntax, but different in meaning.
-
- A body part is an entity and hence is NOT to be interpreted as
- actually being an RFC 822 message. To begin with, NO header fields
- are actually required in body parts. A body part that starts with a
- blank line, therefore, is allowed and is a body part for which all
- default values are to be assumed. In such a case, the absence of a
- Content-Type header usually indicates that the corresponding body has
-
-
-
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-
-
- a content-type of "text/plain; charset=US-ASCII".
-
- The only header fields that have defined meaning for body parts are
- those the names of which begin with "Content-". All other header
- fields may be ignored in body parts. Although they should generally
- be retained if at all possible, they may be discarded by gateways if
- necessary. Such other fields are permitted to appear in body parts
- but must not be depended on. "X-" fields may be created for
- experimental or private purposes, with the recognition that the
- information they contain may be lost at some gateways.
-
- NOTE: The distinction between an RFC 822 message and a body part is
- subtle, but important. A gateway between Internet and X.400 mail,
- for example, must be able to tell the difference between a body part
- that contains an image and a body part that contains an encapsulated
- message, the body of which is a JPEG image. In order to represent
- the latter, the body part must have "Content-Type: message/rfc822",
- and its body (after the blank line) must be the encapsulated message,
- with its own "Content-Type: image/jpeg" header field. The use of
- similar syntax facilitates the conversion of messages to body parts,
- and vice versa, but the distinction between the two must be
- understood by implementors. (For the special case in which parts
- actually are messages, a "digest" subtype is also defined.)
-
- As stated previously, each body part is preceded by a boundary
- delimiter line that contains the boundary delimiter. The boundary
- delimiter MUST NOT appear inside any of the encapsulated parts, on a
- line by itself or as the prefix of any line. This implies that it is
- crucial that the composing agent be able to choose and specify a
- unique boundary parameter value that does not contain the boundary
- parameter value of an enclosing multipart as a prefix.
-
- All present and future subtypes of the "multipart" type must use an
- identical syntax. Subtypes may differ in their semantics, and may
- impose additional restrictions on syntax, but must conform to the
- required syntax for the "multipart" type. This requirement ensures
- that all conformant user agents will at least be able to recognize
- and separate the parts of any multipart entity, even those of an
- unrecognized subtype.
-
- As stated in the definition of the Content-Transfer-Encoding field
- [RFC 2045], no encoding other than "7bit", "8bit", or "binary" is
- permitted for entities of type "multipart". The "multipart" boundary
- delimiters and header fields are always represented as 7bit US-ASCII
- in any case (though the header fields may encode non-US-ASCII header
- text as per RFC 2047) and data within the body parts can be encoded
- on a part-by-part basis, with Content-Transfer-Encoding fields for
- each appropriate body part.
-
-
-
-Freed & Borenstein Standards Track [Page 18]
-
-RFC 2046 Media Types November 1996
-
-
-5.1.1. Common Syntax
-
- This section defines a common syntax for subtypes of "multipart".
- All subtypes of "multipart" must use this syntax. A simple example
- of a multipart message also appears in this section. An example of a
- more complex multipart message is given in RFC 2049.
-
- The Content-Type field for multipart entities requires one parameter,
- "boundary". The boundary delimiter line is then defined as a line
- consisting entirely of two hyphen characters ("-", decimal value 45)
- followed by the boundary parameter value from the Content-Type header
- field, optional linear whitespace, and a terminating CRLF.
-
- NOTE: The hyphens are for rough compatibility with the earlier RFC
- 934 method of message encapsulation, and for ease of searching for
- the boundaries in some implementations. However, it should be noted
- that multipart messages are NOT completely compatible with RFC 934
- encapsulations; in particular, they do not obey RFC 934 quoting
- conventions for embedded lines that begin with hyphens. This
- mechanism was chosen over the RFC 934 mechanism because the latter
- causes lines to grow with each level of quoting. The combination of
- this growth with the fact that SMTP implementations sometimes wrap
- long lines made the RFC 934 mechanism unsuitable for use in the event
- that deeply-nested multipart structuring is ever desired.
-
- WARNING TO IMPLEMENTORS: The grammar for parameters on the Content-
- type field is such that it is often necessary to enclose the boundary
- parameter values in quotes on the Content-type line. This is not
- always necessary, but never hurts. Implementors should be sure to
- study the grammar carefully in order to avoid producing invalid
- Content-type fields. Thus, a typical "multipart" Content-Type header
- field might look like this:
-
- Content-Type: multipart/mixed; boundary=gc0p4Jq0M2Yt08j34c0p
-
- But the following is not valid:
-
- Content-Type: multipart/mixed; boundary=gc0pJq0M:08jU534c0p
-
- (because of the colon) and must instead be represented as
-
- Content-Type: multipart/mixed; boundary="gc0pJq0M:08jU534c0p"
-
- This Content-Type value indicates that the content consists of one or
- more parts, each with a structure that is syntactically identical to
- an RFC 822 message, except that the header area is allowed to be
- completely empty, and that the parts are each preceded by the line
-
-
-
-
-Freed & Borenstein Standards Track [Page 19]
-
-RFC 2046 Media Types November 1996
-
-
- --gc0pJq0M:08jU534c0p
-
- The boundary delimiter MUST occur at the beginning of a line, i.e.,
- following a CRLF, and the initial CRLF is considered to be attached
- to the boundary delimiter line rather than part of the preceding
- part. The boundary may be followed by zero or more characters of
- linear whitespace. It is then terminated by either another CRLF and
- the header fields for the next part, or by two CRLFs, in which case
- there are no header fields for the next part. If no Content-Type
- field is present it is assumed to be "message/rfc822" in a
- "multipart/digest" and "text/plain" otherwise.
-
- NOTE: The CRLF preceding the boundary delimiter line is conceptually
- attached to the boundary so that it is possible to have a part that
- does not end with a CRLF (line break). Body parts that must be
- considered to end with line breaks, therefore, must have two CRLFs
- preceding the boundary delimiter line, the first of which is part of
- the preceding body part, and the second of which is part of the
- encapsulation boundary.
-
- Boundary delimiters must not appear within the encapsulated material,
- and must be no longer than 70 characters, not counting the two
- leading hyphens.
-
- The boundary delimiter line following the last body part is a
- distinguished delimiter that indicates that no further body parts
- will follow. Such a delimiter line is identical to the previous
- delimiter lines, with the addition of two more hyphens after the
- boundary parameter value.
-
- --gc0pJq0M:08jU534c0p--
-
- NOTE TO IMPLEMENTORS: Boundary string comparisons must compare the
- boundary value with the beginning of each candidate line. An exact
- match of the entire candidate line is not required; it is sufficient
- that the boundary appear in its entirety following the CRLF.
-
- There appears to be room for additional information prior to the
- first boundary delimiter line and following the final boundary
- delimiter line. These areas should generally be left blank, and
- implementations must ignore anything that appears before the first
- boundary delimiter line or after the last one.
-
- NOTE: These "preamble" and "epilogue" areas are generally not used
- because of the lack of proper typing of these parts and the lack of
- clear semantics for handling these areas at gateways, particularly
- X.400 gateways. However, rather than leaving the preamble area
- blank, many MIME implementations have found this to be a convenient
-
-
-
-Freed & Borenstein Standards Track [Page 20]
-
-RFC 2046 Media Types November 1996
-
-
- place to insert an explanatory note for recipients who read the
- message with pre-MIME software, since such notes will be ignored by
- MIME-compliant software.
-
- NOTE: Because boundary delimiters must not appear in the body parts
- being encapsulated, a user agent must exercise care to choose a
- unique boundary parameter value. The boundary parameter value in the
- example above could have been the result of an algorithm designed to
- produce boundary delimiters with a very low probability of already
- existing in the data to be encapsulated without having to prescan the
- data. Alternate algorithms might result in more "readable" boundary
- delimiters for a recipient with an old user agent, but would require
- more attention to the possibility that the boundary delimiter might
- appear at the beginning of some line in the encapsulated part. The
- simplest boundary delimiter line possible is something like "---",
- with a closing boundary delimiter line of "-----".
-
- As a very simple example, the following multipart message has two
- parts, both of them plain text, one of them explicitly typed and one
- of them implicitly typed:
-
- From: Nathaniel Borenstein <nsb@bellcore.com>
- To: Ned Freed <ned@innosoft.com>
- Date: Sun, 21 Mar 1993 23:56:48 -0800 (PST)
- Subject: Sample message
- MIME-Version: 1.0
- Content-type: multipart/mixed; boundary="simple boundary"
-
- This is the preamble. It is to be ignored, though it
- is a handy place for composition agents to include an
- explanatory note to non-MIME conformant readers.
-
- --simple boundary
-
- This is implicitly typed plain US-ASCII text.
- It does NOT end with a linebreak.
- --simple boundary
- Content-type: text/plain; charset=us-ascii
-
- This is explicitly typed plain US-ASCII text.
- It DOES end with a linebreak.
-
- --simple boundary--
-
- This is the epilogue. It is also to be ignored.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 21]
-
-RFC 2046 Media Types November 1996
-
-
- The use of a media type of "multipart" in a body part within another
- "multipart" entity is explicitly allowed. In such cases, for obvious
- reasons, care must be taken to ensure that each nested "multipart"
- entity uses a different boundary delimiter. See RFC 2049 for an
- example of nested "multipart" entities.
-
- The use of the "multipart" media type with only a single body part
- may be useful in certain contexts, and is explicitly permitted.
-
- NOTE: Experience has shown that a "multipart" media type with a
- single body part is useful for sending non-text media types. It has
- the advantage of providing the preamble as a place to include
- decoding instructions. In addition, a number of SMTP gateways move
- or remove the MIME headers, and a clever MIME decoder can take a good
- guess at multipart boundaries even in the absence of the Content-Type
- header and thereby successfully decode the message.
-
- The only mandatory global parameter for the "multipart" media type is
- the boundary parameter, which consists of 1 to 70 characters from a
- set of characters known to be very robust through mail gateways, and
- NOT ending with white space. (If a boundary delimiter line appears to
- end with white space, the white space must be presumed to have been
- added by a gateway, and must be deleted.) It is formally specified
- by the following BNF:
-
- boundary := 0*69<bchars> bcharsnospace
-
- bchars := bcharsnospace / " "
-
- bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" /
- "+" / "_" / "," / "-" / "." /
- "/" / ":" / "=" / "?"
-
- Overall, the body of a "multipart" entity may be specified as
- follows:
-
- dash-boundary := "--" boundary
- ; boundary taken from the value of
- ; boundary parameter of the
- ; Content-Type field.
-
- multipart-body := [preamble CRLF]
- dash-boundary transport-padding CRLF
- body-part *encapsulation
- close-delimiter transport-padding
- [CRLF epilogue]
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 22]
-
-RFC 2046 Media Types November 1996
-
-
- transport-padding := *LWSP-char
- ; Composers MUST NOT generate
- ; non-zero length transport
- ; padding, but receivers MUST
- ; be able to handle padding
- ; added by message transports.
-
- encapsulation := delimiter transport-padding
- CRLF body-part
-
- delimiter := CRLF dash-boundary
-
- close-delimiter := delimiter "--"
-
- preamble := discard-text
-
- epilogue := discard-text
-
- discard-text := *(*text CRLF) *text
- ; May be ignored or discarded.
-
- body-part := MIME-part-headers [CRLF *OCTET]
- ; Lines in a body-part must not start
- ; with the specified dash-boundary and
- ; the delimiter must not appear anywhere
- ; in the body part. Note that the
- ; semantics of a body-part differ from
- ; the semantics of a message, as
- ; described in the text.
-
- OCTET := <any 0-255 octet value>
-
- IMPORTANT: The free insertion of linear-white-space and RFC 822
- comments between the elements shown in this BNF is NOT allowed since
- this BNF does not specify a structured header field.
-
- NOTE: In certain transport enclaves, RFC 822 restrictions such as
- the one that limits bodies to printable US-ASCII characters may not
- be in force. (That is, the transport domains may exist that resemble
- standard Internet mail transport as specified in RFC 821 and assumed
- by RFC 822, but without certain restrictions.) The relaxation of
- these restrictions should be construed as locally extending the
- definition of bodies, for example to include octets outside of the
- US-ASCII range, as long as these extensions are supported by the
- transport and adequately documented in the Content- Transfer-Encoding
- header field. However, in no event are headers (either message
- headers or body part headers) allowed to contain anything other than
- US-ASCII characters.
-
-
-
-Freed & Borenstein Standards Track [Page 23]
-
-RFC 2046 Media Types November 1996
-
-
- NOTE: Conspicuously missing from the "multipart" type is a notion of
- structured, related body parts. It is recommended that those wishing
- to provide more structured or integrated multipart messaging
- facilities should define subtypes of multipart that are syntactically
- identical but define relationships between the various parts. For
- example, subtypes of multipart could be defined that include a
- distinguished part which in turn is used to specify the relationships
- between the other parts, probably referring to them by their
- Content-ID field. Old implementations will not recognize the new
- subtype if this approach is used, but will treat it as
- multipart/mixed and will thus be able to show the user the parts that
- are recognized.
-
-5.1.2. Handling Nested Messages and Multiparts
-
- The "message/rfc822" subtype defined in a subsequent section of this
- document has no terminating condition other than running out of data.
- Similarly, an improperly truncated "multipart" entity may not have
- any terminating boundary marker, and can turn up operationally due to
- mail system malfunctions.
-
- It is essential that such entities be handled correctly when they are
- themselves imbedded inside of another "multipart" structure. MIME
- implementations are therefore required to recognize outer level
- boundary markers at ANY level of inner nesting. It is not sufficient
- to only check for the next expected marker or other terminating
- condition.
-
-5.1.3. Mixed Subtype
-
- The "mixed" subtype of "multipart" is intended for use when the body
- parts are independent and need to be bundled in a particular order.
- Any "multipart" subtypes that an implementation does not recognize
- must be treated as being of subtype "mixed".
-
-5.1.4. Alternative Subtype
-
- The "multipart/alternative" type is syntactically identical to
- "multipart/mixed", but the semantics are different. In particular,
- each of the body parts is an "alternative" version of the same
- information.
-
- Systems should recognize that the content of the various parts are
- interchangeable. Systems should choose the "best" type based on the
- local environment and references, in some cases even through user
- interaction. As with "multipart/mixed", the order of body parts is
- significant. In this case, the alternatives appear in an order of
- increasing faithfulness to the original content. In general, the
-
-
-
-Freed & Borenstein Standards Track [Page 24]
-
-RFC 2046 Media Types November 1996
-
-
- best choice is the LAST part of a type supported by the recipient
- system's local environment.
-
- "Multipart/alternative" may be used, for example, to send a message
- in a fancy text format in such a way that it can easily be displayed
- anywhere:
-
- From: Nathaniel Borenstein <nsb@bellcore.com>
- To: Ned Freed <ned@innosoft.com>
- Date: Mon, 22 Mar 1993 09:41:09 -0800 (PST)
- Subject: Formatted text mail
- MIME-Version: 1.0
- Content-Type: multipart/alternative; boundary=boundary42
-
- --boundary42
- Content-Type: text/plain; charset=us-ascii
-
- ... plain text version of message goes here ...
-
- --boundary42
- Content-Type: text/enriched
-
- ... RFC 1896 text/enriched version of same message
- goes here ...
-
- --boundary42
- Content-Type: application/x-whatever
-
- ... fanciest version of same message goes here ...
-
- --boundary42--
-
- In this example, users whose mail systems understood the
- "application/x-whatever" format would see only the fancy version,
- while other users would see only the enriched or plain text version,
- depending on the capabilities of their system.
-
- In general, user agents that compose "multipart/alternative" entities
- must place the body parts in increasing order of preference, that is,
- with the preferred format last. For fancy text, the sending user
- agent should put the plainest format first and the richest format
- last. Receiving user agents should pick and display the last format
- they are capable of displaying. In the case where one of the
- alternatives is itself of type "multipart" and contains unrecognized
- sub-parts, the user agent may choose either to show that alternative,
- an earlier alternative, or both.
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 25]
-
-RFC 2046 Media Types November 1996
-
-
- NOTE: From an implementor's perspective, it might seem more sensible
- to reverse this ordering, and have the plainest alternative last.
- However, placing the plainest alternative first is the friendliest
- possible option when "multipart/alternative" entities are viewed
- using a non-MIME-conformant viewer. While this approach does impose
- some burden on conformant MIME viewers, interoperability with older
- mail readers was deemed to be more important in this case.
-
- It may be the case that some user agents, if they can recognize more
- than one of the formats, will prefer to offer the user the choice of
- which format to view. This makes sense, for example, if a message
- includes both a nicely- formatted image version and an easily-edited
- text version. What is most critical, however, is that the user not
- automatically be shown multiple versions of the same data. Either
- the user should be shown the last recognized version or should be
- given the choice.
-
- THE SEMANTICS OF CONTENT-ID IN MULTIPART/ALTERNATIVE: Each part of a
- "multipart/alternative" entity represents the same data, but the
- mappings between the two are not necessarily without information
- loss. For example, information is lost when translating ODA to
- PostScript or plain text. It is recommended that each part should
- have a different Content-ID value in the case where the information
- content of the two parts is not identical. And when the information
- content is identical -- for example, where several parts of type
- "message/external-body" specify alternate ways to access the
- identical data -- the same Content-ID field value should be used, to
- optimize any caching mechanisms that might be present on the
- recipient's end. However, the Content-ID values used by the parts
- should NOT be the same Content-ID value that describes the
- "multipart/alternative" as a whole, if there is any such Content-ID
- field. That is, one Content-ID value will refer to the
- "multipart/alternative" entity, while one or more other Content-ID
- values will refer to the parts inside it.
-
-5.1.5. Digest Subtype
-
- This document defines a "digest" subtype of the "multipart" Content-
- Type. This type is syntactically identical to "multipart/mixed", but
- the semantics are different. In particular, in a digest, the default
- Content-Type value for a body part is changed from "text/plain" to
- "message/rfc822". This is done to allow a more readable digest
- format that is largely compatible (except for the quoting convention)
- with RFC 934.
-
- Note: Though it is possible to specify a Content-Type value for a
- body part in a digest which is other than "message/rfc822", such as a
- "text/plain" part containing a description of the material in the
-
-
-
-Freed & Borenstein Standards Track [Page 26]
-
-RFC 2046 Media Types November 1996
-
-
- digest, actually doing so is undesireble. The "multipart/digest"
- Content-Type is intended to be used to send collections of messages.
- If a "text/plain" part is needed, it should be included as a seperate
- part of a "multipart/mixed" message.
-
- A digest in this format might, then, look something like this:
-
- From: Moderator-Address
- To: Recipient-List
- Date: Mon, 22 Mar 1994 13:34:51 +0000
- Subject: Internet Digest, volume 42
- MIME-Version: 1.0
- Content-Type: multipart/mixed;
- boundary="---- main boundary ----"
-
- ------ main boundary ----
-
- ...Introductory text or table of contents...
-
- ------ main boundary ----
- Content-Type: multipart/digest;
- boundary="---- next message ----"
-
- ------ next message ----
-
- From: someone-else
- Date: Fri, 26 Mar 1993 11:13:32 +0200
- Subject: my opinion
-
- ...body goes here ...
-
- ------ next message ----
-
- From: someone-else-again
- Date: Fri, 26 Mar 1993 10:07:13 -0500
- Subject: my different opinion
-
- ... another body goes here ...
-
- ------ next message ------
-
- ------ main boundary ------
-
-5.1.6. Parallel Subtype
-
- This document defines a "parallel" subtype of the "multipart"
- Content-Type. This type is syntactically identical to
- "multipart/mixed", but the semantics are different. In particular,
-
-
-
-Freed & Borenstein Standards Track [Page 27]
-
-RFC 2046 Media Types November 1996
-
-
- in a parallel entity, the order of body parts is not significant.
-
- A common presentation of this type is to display all of the parts
- simultaneously on hardware and software that are capable of doing so.
- However, composing agents should be aware that many mail readers will
- lack this capability and will show the parts serially in any event.
-
-5.1.7. Other Multipart Subtypes
-
- Other "multipart" subtypes are expected in the future. MIME
- implementations must in general treat unrecognized subtypes of
- "multipart" as being equivalent to "multipart/mixed".
-
-5.2. Message Media Type
-
- It is frequently desirable, in sending mail, to encapsulate another
- mail message. A special media type, "message", is defined to
- facilitate this. In particular, the "rfc822" subtype of "message" is
- used to encapsulate RFC 822 messages.
-
- NOTE: It has been suggested that subtypes of "message" might be
- defined for forwarded or rejected messages. However, forwarded and
- rejected messages can be handled as multipart messages in which the
- first part contains any control or descriptive information, and a
- second part, of type "message/rfc822", is the forwarded or rejected
- message. Composing rejection and forwarding messages in this manner
- will preserve the type information on the original message and allow
- it to be correctly presented to the recipient, and hence is strongly
- encouraged.
-
- Subtypes of "message" often impose restrictions on what encodings are
- allowed. These restrictions are described in conjunction with each
- specific subtype.
-
- Mail gateways, relays, and other mail handling agents are commonly
- known to alter the top-level header of an RFC 822 message. In
- particular, they frequently add, remove, or reorder header fields.
- These operations are explicitly forbidden for the encapsulated
- headers embedded in the bodies of messages of type "message."
-
-5.2.1. RFC822 Subtype
-
- A media type of "message/rfc822" indicates that the body contains an
- encapsulated message, with the syntax of an RFC 822 message.
- However, unlike top-level RFC 822 messages, the restriction that each
- "message/rfc822" body must include a "From", "Date", and at least one
- destination header is removed and replaced with the requirement that
- at least one of "From", "Subject", or "Date" must be present.
-
-
-
-Freed & Borenstein Standards Track [Page 28]
-
-RFC 2046 Media Types November 1996
-
-
- It should be noted that, despite the use of the numbers "822", a
- "message/rfc822" entity isn't restricted to material in strict
- conformance to RFC822, nor are the semantics of "message/rfc822"
- objects restricted to the semantics defined in RFC822. More
- specifically, a "message/rfc822" message could well be a News article
- or a MIME message.
-
- No encoding other than "7bit", "8bit", or "binary" is permitted for
- the body of a "message/rfc822" entity. The message header fields are
- always US-ASCII in any case, and data within the body can still be
- encoded, in which case the Content-Transfer-Encoding header field in
- the encapsulated message will reflect this. Non-US-ASCII text in the
- headers of an encapsulated message can be specified using the
- mechanisms described in RFC 2047.
-
-5.2.2. Partial Subtype
-
- The "partial" subtype is defined to allow large entities to be
- delivered as several separate pieces of mail and automatically
- reassembled by a receiving user agent. (The concept is similar to IP
- fragmentation and reassembly in the basic Internet Protocols.) This
- mechanism can be used when intermediate transport agents limit the
- size of individual messages that can be sent. The media type
- "message/partial" thus indicates that the body contains a fragment of
- a larger entity.
-
- Because data of type "message" may never be encoded in base64 or
- quoted-printable, a problem might arise if "message/partial" entities
- are constructed in an environment that supports binary or 8bit
- transport. The problem is that the binary data would be split into
- multiple "message/partial" messages, each of them requiring binary
- transport. If such messages were encountered at a gateway into a
- 7bit transport environment, there would be no way to properly encode
- them for the 7bit world, aside from waiting for all of the fragments,
- reassembling the inner message, and then encoding the reassembled
- data in base64 or quoted-printable. Since it is possible that
- different fragments might go through different gateways, even this is
- not an acceptable solution. For this reason, it is specified that
- entities of type "message/partial" must always have a content-
- transfer-encoding of 7bit (the default). In particular, even in
- environments that support binary or 8bit transport, the use of a
- content- transfer-encoding of "8bit" or "binary" is explicitly
- prohibited for MIME entities of type "message/partial". This in turn
- implies that the inner message must not use "8bit" or "binary"
- encoding.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 29]
-
-RFC 2046 Media Types November 1996
-
-
- Because some message transfer agents may choose to automatically
- fragment large messages, and because such agents may use very
- different fragmentation thresholds, it is possible that the pieces of
- a partial message, upon reassembly, may prove themselves to comprise
- a partial message. This is explicitly permitted.
-
- Three parameters must be specified in the Content-Type field of type
- "message/partial": The first, "id", is a unique identifier, as close
- to a world-unique identifier as possible, to be used to match the
- fragments together. (In general, the identifier is essentially a
- message-id; if placed in double quotes, it can be ANY message-id, in
- accordance with the BNF for "parameter" given in RFC 2045.) The
- second, "number", an integer, is the fragment number, which indicates
- where this fragment fits into the sequence of fragments. The third,
- "total", another integer, is the total number of fragments. This
- third subfield is required on the final fragment, and is optional
- (though encouraged) on the earlier fragments. Note also that these
- parameters may be given in any order.
-
- Thus, the second piece of a 3-piece message may have either of the
- following header fields:
-
- Content-Type: Message/Partial; number=2; total=3;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com"
-
- Content-Type: Message/Partial;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
- number=2
-
- But the third piece MUST specify the total number of fragments:
-
- Content-Type: Message/Partial; number=3; total=3;
- id="oc=jpbe0M2Yt4s@thumper.bellcore.com"
-
- Note that fragment numbering begins with 1, not 0.
-
- When the fragments of an entity broken up in this manner are put
- together, the result is always a complete MIME entity, which may have
- its own Content-Type header field, and thus may contain any other
- data type.
-
-5.2.2.1. Message Fragmentation and Reassembly
-
- The semantics of a reassembled partial message must be those of the
- "inner" message, rather than of a message containing the inner
- message. This makes it possible, for example, to send a large audio
- message as several partial messages, and still have it appear to the
- recipient as a simple audio message rather than as an encapsulated
-
-
-
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-
-RFC 2046 Media Types November 1996
-
-
- message containing an audio message. That is, the encapsulation of
- the message is considered to be "transparent".
-
- When generating and reassembling the pieces of a "message/partial"
- message, the headers of the encapsulated message must be merged with
- the headers of the enclosing entities. In this process the following
- rules must be observed:
-
- (1) Fragmentation agents must split messages at line
- boundaries only. This restriction is imposed because
- splits at points other than the ends of lines in turn
- depends on message transports being able to preserve
- the semantics of messages that don't end with a CRLF
- sequence. Many transports are incapable of preserving
- such semantics.
-
- (2) All of the header fields from the initial enclosing
- message, except those that start with "Content-" and
- the specific header fields "Subject", "Message-ID",
- "Encrypted", and "MIME-Version", must be copied, in
- order, to the new message.
-
- (3) The header fields in the enclosed message which start
- with "Content-", plus the "Subject", "Message-ID",
- "Encrypted", and "MIME-Version" fields, must be
- appended, in order, to the header fields of the new
- message. Any header fields in the enclosed message
- which do not start with "Content-" (except for the
- "Subject", "Message-ID", "Encrypted", and "MIME-
- Version" fields) will be ignored and dropped.
-
- (4) All of the header fields from the second and any
- subsequent enclosing messages are discarded by the
- reassembly process.
-
-5.2.2.2. Fragmentation and Reassembly Example
-
- If an audio message is broken into two pieces, the first piece might
- look something like this:
-
- X-Weird-Header-1: Foo
- From: Bill@host.com
- To: joe@otherhost.com
- Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
- Subject: Audio mail (part 1 of 2)
- Message-ID: <id1@host.com>
- MIME-Version: 1.0
- Content-type: message/partial; id="ABC@host.com";
-
-
-
-Freed & Borenstein Standards Track [Page 31]
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-RFC 2046 Media Types November 1996
-
-
- number=1; total=2
-
- X-Weird-Header-1: Bar
- X-Weird-Header-2: Hello
- Message-ID: <anotherid@foo.com>
- Subject: Audio mail
- MIME-Version: 1.0
- Content-type: audio/basic
- Content-transfer-encoding: base64
-
- ... first half of encoded audio data goes here ...
-
- and the second half might look something like this:
-
- From: Bill@host.com
- To: joe@otherhost.com
- Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
- Subject: Audio mail (part 2 of 2)
- MIME-Version: 1.0
- Message-ID: <id2@host.com>
- Content-type: message/partial;
- id="ABC@host.com"; number=2; total=2
-
- ... second half of encoded audio data goes here ...
-
- Then, when the fragmented message is reassembled, the resulting
- message to be displayed to the user should look something like this:
-
- X-Weird-Header-1: Foo
- From: Bill@host.com
- To: joe@otherhost.com
- Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
- Subject: Audio mail
- Message-ID: <anotherid@foo.com>
- MIME-Version: 1.0
- Content-type: audio/basic
- Content-transfer-encoding: base64
-
- ... first half of encoded audio data goes here ...
- ... second half of encoded audio data goes here ...
-
- The inclusion of a "References" field in the headers of the second
- and subsequent pieces of a fragmented message that references the
- Message-Id on the previous piece may be of benefit to mail readers
- that understand and track references. However, the generation of
- such "References" fields is entirely optional.
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 32]
-
-RFC 2046 Media Types November 1996
-
-
- Finally, it should be noted that the "Encrypted" header field has
- been made obsolete by Privacy Enhanced Messaging (PEM) [RFC-1421,
- RFC-1422, RFC-1423, RFC-1424], but the rules above are nevertheless
- believed to describe the correct way to treat it if it is encountered
- in the context of conversion to and from "message/partial" fragments.
-
-5.2.3. External-Body Subtype
-
- The external-body subtype indicates that the actual body data are not
- included, but merely referenced. In this case, the parameters
- describe a mechanism for accessing the external data.
-
- When a MIME entity is of type "message/external-body", it consists of
- a header, two consecutive CRLFs, and the message header for the
- encapsulated message. If another pair of consecutive CRLFs appears,
- this of course ends the message header for the encapsulated message.
- However, since the encapsulated message's body is itself external, it
- does NOT appear in the area that follows. For example, consider the
- following message:
-
- Content-type: message/external-body;
- access-type=local-file;
- name="/u/nsb/Me.jpeg"
-
- Content-type: image/jpeg
- Content-ID: <id42@guppylake.bellcore.com>
- Content-Transfer-Encoding: binary
-
- THIS IS NOT REALLY THE BODY!
-
- The area at the end, which might be called the "phantom body", is
- ignored for most external-body messages. However, it may be used to
- contain auxiliary information for some such messages, as indeed it is
- when the access-type is "mail- server". The only access-type defined
- in this document that uses the phantom body is "mail-server", but
- other access-types may be defined in the future in other
- specifications that use this area.
-
- The encapsulated headers in ALL "message/external-body" entities MUST
- include a Content-ID header field to give a unique identifier by
- which to reference the data. This identifier may be used for caching
- mechanisms, and for recognizing the receipt of the data when the
- access-type is "mail-server".
-
- Note that, as specified here, the tokens that describe external-body
- data, such as file names and mail server commands, are required to be
- in the US-ASCII character set.
-
-
-
-
-Freed & Borenstein Standards Track [Page 33]
-
-RFC 2046 Media Types November 1996
-
-
- If this proves problematic in practice, a new mechanism may be
- required as a future extension to MIME, either as newly defined
- access-types for "message/external-body" or by some other mechanism.
-
- As with "message/partial", MIME entities of type "message/external-
- body" MUST have a content-transfer-encoding of 7bit (the default).
- In particular, even in environments that support binary or 8bit
- transport, the use of a content- transfer-encoding of "8bit" or
- "binary" is explicitly prohibited for entities of type
- "message/external-body".
-
-5.2.3.1. General External-Body Parameters
-
- The parameters that may be used with any "message/external- body"
- are:
-
- (1) ACCESS-TYPE -- A word indicating the supported access
- mechanism by which the file or data may be obtained.
- This word is not case sensitive. Values include, but
- are not limited to, "FTP", "ANON-FTP", "TFTP", "LOCAL-
- FILE", and "MAIL-SERVER". Future values, except for
- experimental values beginning with "X-", must be
- registered with IANA, as described in RFC 2048.
- This parameter is unconditionally mandatory and MUST be
- present on EVERY "message/external-body".
-
- (2) EXPIRATION -- The date (in the RFC 822 "date-time"
- syntax, as extended by RFC 1123 to permit 4 digits in
- the year field) after which the existence of the
- external data is not guaranteed. This parameter may be
- used with ANY access-type and is ALWAYS optional.
-
- (3) SIZE -- The size (in octets) of the data. The intent
- of this parameter is to help the recipient decide
- whether or not to expend the necessary resources to
- retrieve the external data. Note that this describes
- the size of the data in its canonical form, that is,
- before any Content-Transfer-Encoding has been applied
- or after the data have been decoded. This parameter
- may be used with ANY access-type and is ALWAYS
- optional.
-
- (4) PERMISSION -- A case-insensitive field that indicates
- whether or not it is expected that clients might also
- attempt to overwrite the data. By default, or if
- permission is "read", the assumption is that they are
- not, and that if the data is retrieved once, it is
- never needed again. If PERMISSION is "read-write",
-
-
-
-Freed & Borenstein Standards Track [Page 34]
-
-RFC 2046 Media Types November 1996
-
-
- this assumption is invalid, and any local copy must be
- considered no more than a cache. "Read" and "Read-
- write" are the only defined values of permission. This
- parameter may be used with ANY access-type and is
- ALWAYS optional.
-
- The precise semantics of the access-types defined here are described
- in the sections that follow.
-
-5.2.3.2. The 'ftp' and 'tftp' Access-Types
-
- An access-type of FTP or TFTP indicates that the message body is
- accessible as a file using the FTP [RFC-959] or TFTP [RFC- 783]
- protocols, respectively. For these access-types, the following
- additional parameters are mandatory:
-
- (1) NAME -- The name of the file that contains the actual
- body data.
-
- (2) SITE -- A machine from which the file may be obtained,
- using the given protocol. This must be a fully
- qualified domain name, not a nickname.
-
- (3) Before any data are retrieved, using FTP, the user will
- generally need to be asked to provide a login id and a
- password for the machine named by the site parameter.
- For security reasons, such an id and password are not
- specified as content-type parameters, but must be
- obtained from the user.
-
- In addition, the following parameters are optional:
-
- (1) DIRECTORY -- A directory from which the data named by
- NAME should be retrieved.
-
- (2) MODE -- A case-insensitive string indicating the mode
- to be used when retrieving the information. The valid
- values for access-type "TFTP" are "NETASCII", "OCTET",
- and "MAIL", as specified by the TFTP protocol [RFC-
- 783]. The valid values for access-type "FTP" are
- "ASCII", "EBCDIC", "IMAGE", and "LOCALn" where "n" is a
- decimal integer, typically 8. These correspond to the
- representation types "A" "E" "I" and "L n" as specified
- by the FTP protocol [RFC-959]. Note that "BINARY" and
- "TENEX" are not valid values for MODE and that "OCTET"
- or "IMAGE" or "LOCAL8" should be used instead. IF MODE
- is not specified, the default value is "NETASCII" for
- TFTP and "ASCII" otherwise.
-
-
-
-Freed & Borenstein Standards Track [Page 35]
-
-RFC 2046 Media Types November 1996
-
-
-5.2.3.3. The 'anon-ftp' Access-Type
-
- The "anon-ftp" access-type is identical to the "ftp" access type,
- except that the user need not be asked to provide a name and password
- for the specified site. Instead, the ftp protocol will be used with
- login "anonymous" and a password that corresponds to the user's mail
- address.
-
-5.2.3.4. The 'local-file' Access-Type
-
- An access-type of "local-file" indicates that the actual body is
- accessible as a file on the local machine. Two additional parameters
- are defined for this access type:
-
- (1) NAME -- The name of the file that contains the actual
- body data. This parameter is mandatory for the
- "local-file" access-type.
-
- (2) SITE -- A domain specifier for a machine or set of
- machines that are known to have access to the data
- file. This optional parameter is used to describe the
- locality of reference for the data, that is, the site
- or sites at which the file is expected to be visible.
- Asterisks may be used for wildcard matching to a part
- of a domain name, such as "*.bellcore.com", to indicate
- a set of machines on which the data should be directly
- visible, while a single asterisk may be used to
- indicate a file that is expected to be universally
- available, e.g., via a global file system.
-
-5.2.3.5. The 'mail-server' Access-Type
-
- The "mail-server" access-type indicates that the actual body is
- available from a mail server. Two additional parameters are defined
- for this access-type:
-
- (1) SERVER -- The addr-spec of the mail server from which
- the actual body data can be obtained. This parameter
- is mandatory for the "mail-server" access-type.
-
- (2) SUBJECT -- The subject that is to be used in the mail
- that is sent to obtain the data. Note that keying mail
- servers on Subject lines is NOT recommended, but such
- mail servers are known to exist. This is an optional
- parameter.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 36]
-
-RFC 2046 Media Types November 1996
-
-
- Because mail servers accept a variety of syntaxes, some of which is
- multiline, the full command to be sent to a mail server is not
- included as a parameter in the content-type header field. Instead,
- it is provided as the "phantom body" when the media type is
- "message/external-body" and the access-type is mail-server.
-
- Note that MIME does not define a mail server syntax. Rather, it
- allows the inclusion of arbitrary mail server commands in the phantom
- body. Implementations must include the phantom body in the body of
- the message it sends to the mail server address to retrieve the
- relevant data.
-
- Unlike other access-types, mail-server access is asynchronous and
- will happen at an unpredictable time in the future. For this reason,
- it is important that there be a mechanism by which the returned data
- can be matched up with the original "message/external-body" entity.
- MIME mail servers must use the same Content-ID field on the returned
- message that was used in the original "message/external-body"
- entities, to facilitate such matching.
-
-5.2.3.6. External-Body Security Issues
-
- "Message/external-body" entities give rise to two important security
- issues:
-
- (1) Accessing data via a "message/external-body" reference
- effectively results in the message recipient performing
- an operation that was specified by the message
- originator. It is therefore possible for the message
- originator to trick a recipient into doing something
- they would not have done otherwise. For example, an
- originator could specify a action that attempts
- retrieval of material that the recipient is not
- authorized to obtain, causing the recipient to
- unwittingly violate some security policy. For this
- reason, user agents capable of resolving external
- references must always take steps to describe the
- action they are to take to the recipient and ask for
- explicit permisssion prior to performing it.
-
- The 'mail-server' access-type is particularly
- vulnerable, in that it causes the recipient to send a
- new message whose contents are specified by the
- original message's originator. Given the potential for
- abuse, any such request messages that are constructed
- should contain a clear indication that they were
- generated automatically (e.g. in a Comments: header
- field) in an attempt to resolve a MIME
-
-
-
-Freed & Borenstein Standards Track [Page 37]
-
-RFC 2046 Media Types November 1996
-
-
- "message/external-body" reference.
-
- (2) MIME will sometimes be used in environments that
- provide some guarantee of message integrity and
- authenticity. If present, such guarantees may apply
- only to the actual direct content of messages -- they
- may or may not apply to data accessed through MIME's
- "message/external-body" mechanism. In particular, it
- may be possible to subvert certain access mechanisms
- even when the messaging system itself is secure.
-
- It should be noted that this problem exists either with
- or without the availabilty of MIME mechanisms. A
- casual reference to an FTP site containing a document
- in the text of a secure message brings up similar
- issues -- the only difference is that MIME provides for
- automatic retrieval of such material, and users may
- place unwarranted trust is such automatic retrieval
- mechanisms.
-
-5.2.3.7. Examples and Further Explanations
-
- When the external-body mechanism is used in conjunction with the
- "multipart/alternative" media type it extends the functionality of
- "multipart/alternative" to include the case where the same entity is
- provided in the same format but via different accces mechanisms.
- When this is done the originator of the message must order the parts
- first in terms of preferred formats and then by preferred access
- mechanisms. The recipient's viewer should then evaluate the list
- both in terms of format and access mechanisms.
-
- With the emerging possibility of very wide-area file systems, it
- becomes very hard to know in advance the set of machines where a file
- will and will not be accessible directly from the file system.
- Therefore it may make sense to provide both a file name, to be tried
- directly, and the name of one or more sites from which the file is
- known to be accessible. An implementation can try to retrieve remote
- files using FTP or any other protocol, using anonymous file retrieval
- or prompting the user for the necessary name and password. If an
- external body is accessible via multiple mechanisms, the sender may
- include multiple entities of type "message/external-body" within the
- body parts of an enclosing "multipart/alternative" entity.
-
- However, the external-body mechanism is not intended to be limited to
- file retrieval, as shown by the mail-server access-type. Beyond
- this, one can imagine, for example, using a video server for external
- references to video clips.
-
-
-
-
-Freed & Borenstein Standards Track [Page 38]
-
-RFC 2046 Media Types November 1996
-
-
- The embedded message header fields which appear in the body of the
- "message/external-body" data must be used to declare the media type
- of the external body if it is anything other than plain US-ASCII
- text, since the external body does not have a header section to
- declare its type. Similarly, any Content-transfer-encoding other
- than "7bit" must also be declared here. Thus a complete
- "message/external-body" message, referring to an object in PostScript
- format, might look like this:
-
- From: Whomever
- To: Someone
- Date: Whenever
- Subject: whatever
- MIME-Version: 1.0
- Message-ID: <id1@host.com>
- Content-Type: multipart/alternative; boundary=42
- Content-ID: <id001@guppylake.bellcore.com>
-
- --42
- Content-Type: message/external-body; name="BodyFormats.ps";
- site="thumper.bellcore.com"; mode="image";
- access-type=ANON-FTP; directory="pub";
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
- Content-ID: <id42@guppylake.bellcore.com>
-
- --42
- Content-Type: message/external-body; access-type=local-file;
- name="/u/nsb/writing/rfcs/RFC-MIME.ps";
- site="thumper.bellcore.com";
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
- Content-ID: <id42@guppylake.bellcore.com>
-
- --42
- Content-Type: message/external-body;
- access-type=mail-server
- server="listserv@bogus.bitnet";
- expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
-
- Content-type: application/postscript
- Content-ID: <id42@guppylake.bellcore.com>
-
- get RFC-MIME.DOC
-
- --42--
-
-
-
-Freed & Borenstein Standards Track [Page 39]
-
-RFC 2046 Media Types November 1996
-
-
- Note that in the above examples, the default Content-transfer-
- encoding of "7bit" is assumed for the external postscript data.
-
- Like the "message/partial" type, the "message/external-body" media
- type is intended to be transparent, that is, to convey the data type
- in the external body rather than to convey a message with a body of
- that type. Thus the headers on the outer and inner parts must be
- merged using the same rules as for "message/partial". In particular,
- this means that the Content-type and Subject fields are overridden,
- but the From field is preserved.
-
- Note that since the external bodies are not transported along with
- the external body reference, they need not conform to transport
- limitations that apply to the reference itself. In particular,
- Internet mail transports may impose 7bit and line length limits, but
- these do not automatically apply to binary external body references.
- Thus a Content-Transfer-Encoding is not generally necessary, though
- it is permitted.
-
- Note that the body of a message of type "message/external-body" is
- governed by the basic syntax for an RFC 822 message. In particular,
- anything before the first consecutive pair of CRLFs is header
- information, while anything after it is body information, which is
- ignored for most access-types.
-
-5.2.4. Other Message Subtypes
-
- MIME implementations must in general treat unrecognized subtypes of
- "message" as being equivalent to "application/octet-stream".
-
- Future subtypes of "message" intended for use with email should be
- restricted to "7bit" encoding. A type other than "message" should be
- used if restriction to "7bit" is not possible.
-
-6. Experimental Media Type Values
-
- A media type value beginning with the characters "X-" is a private
- value, to be used by consenting systems by mutual agreement. Any
- format without a rigorous and public definition must be named with an
- "X-" prefix, and publicly specified values shall never begin with
- "X-". (Older versions of the widely used Andrew system use the "X-
- BE2" name, so new systems should probably choose a different name.)
-
- In general, the use of "X-" top-level types is strongly discouraged.
- Implementors should invent subtypes of the existing types whenever
- possible. In many cases, a subtype of "application" will be more
- appropriate than a new top-level type.
-
-
-
-
-Freed & Borenstein Standards Track [Page 40]
-
-RFC 2046 Media Types November 1996
-
-
-7. Summary
-
- The five discrete media types provide provide a standardized
- mechanism for tagging entities as "audio", "image", or several other
- kinds of data. The composite "multipart" and "message" media types
- allow mixing and hierarchical structuring of entities of different
- types in a single message. A distinguished parameter syntax allows
- further specification of data format details, particularly the
- specification of alternate character sets. Additional optional
- header fields provide mechanisms for certain extensions deemed
- desirable by many implementors. Finally, a number of useful media
- types are defined for general use by consenting user agents, notably
- "message/partial" and "message/external-body".
-
-9. Security Considerations
-
- Security issues are discussed in the context of the
- "application/postscript" type, the "message/external-body" type, and
- in RFC 2048. Implementors should pay special attention to the
- security implications of any media types that can cause the remote
- execution of any actions in the recipient's environment. In such
- cases, the discussion of the "application/postscript" type may serve
- as a model for considering other media types with remote execution
- capabilities.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 41]
-
-RFC 2046 Media Types November 1996
-
-
-9. Authors' Addresses
-
- For more information, the authors of this document are best contacted
- via Internet mail:
-
- Ned Freed
- Innosoft International, Inc.
- 1050 East Garvey Avenue South
- West Covina, CA 91790
- USA
-
- Phone: +1 818 919 3600
- Fax: +1 818 919 3614
- EMail: ned@innosoft.com
-
-
- Nathaniel S. Borenstein
- First Virtual Holdings
- 25 Washington Avenue
- Morristown, NJ 07960
- USA
-
- Phone: +1 201 540 8967
- Fax: +1 201 993 3032
- EMail: nsb@nsb.fv.com
-
-
- MIME is a result of the work of the Internet Engineering Task Force
- Working Group on RFC 822 Extensions. The chairman of that group,
- Greg Vaudreuil, may be reached at:
-
- Gregory M. Vaudreuil
- Octel Network Services
- 17080 Dallas Parkway
- Dallas, TX 75248-1905
- USA
-
- EMail: Greg.Vaudreuil@Octel.Com
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 42]
-
-RFC 2046 Media Types November 1996
-
-
-Appendix A -- Collected Grammar
-
- This appendix contains the complete BNF grammar for all the syntax
- specified by this document.
-
- By itself, however, this grammar is incomplete. It refers by name to
- several syntax rules that are defined by RFC 822. Rather than
- reproduce those definitions here, and risk unintentional differences
- between the two, this document simply refers the reader to RFC 822
- for the remaining definitions. Wherever a term is undefined, it
- refers to the RFC 822 definition.
-
- boundary := 0*69<bchars> bcharsnospace
-
- bchars := bcharsnospace / " "
-
- bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" /
- "+" / "_" / "," / "-" / "." /
- "/" / ":" / "=" / "?"
-
- body-part := <"message" as defined in RFC 822, with all
- header fields optional, not starting with the
- specified dash-boundary, and with the
- delimiter not occurring anywhere in the
- body part. Note that the semantics of a
- part differ from the semantics of a message,
- as described in the text.>
-
- close-delimiter := delimiter "--"
-
- dash-boundary := "--" boundary
- ; boundary taken from the value of
- ; boundary parameter of the
- ; Content-Type field.
-
- delimiter := CRLF dash-boundary
-
- discard-text := *(*text CRLF)
- ; May be ignored or discarded.
-
- encapsulation := delimiter transport-padding
- CRLF body-part
-
- epilogue := discard-text
-
- multipart-body := [preamble CRLF]
- dash-boundary transport-padding CRLF
- body-part *encapsulation
-
-
-
-Freed & Borenstein Standards Track [Page 43]
-
-RFC 2046 Media Types November 1996
-
-
- close-delimiter transport-padding
- [CRLF epilogue]
-
- preamble := discard-text
-
- transport-padding := *LWSP-char
- ; Composers MUST NOT generate
- ; non-zero length transport
- ; padding, but receivers MUST
- ; be able to handle padding
- ; added by message transports.
-
-
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-Freed & Borenstein Standards Track [Page 44]
-
diff --git a/proto/rfc2047.txt b/proto/rfc2047.txt
@@ -1,843 +0,0 @@
-
-
-
-
-
-
-Network Working Group K. Moore
-Request for Comments: 2047 University of Tennessee
-Obsoletes: 1521, 1522, 1590 November 1996
-Category: Standards Track
-
-
- MIME (Multipurpose Internet Mail Extensions) Part Three:
- Message Header Extensions for Non-ASCII Text
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- STD 11, RFC 822, defines a message representation protocol specifying
- considerable detail about US-ASCII message headers, and leaves the
- message content, or message body, as flat US-ASCII text. This set of
- documents, collectively called the Multipurpose Internet Mail
- Extensions, or MIME, redefines the format of messages to allow for
-
- (1) textual message bodies in character sets other than US-ASCII,
-
- (2) an extensible set of different formats for non-textual message
- bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than US-ASCII.
-
- These documents are based on earlier work documented in RFC 934, STD
- 11, and RFC 1049, but extends and revises them. Because RFC 822 said
- so little about message bodies, these documents are largely
- orthogonal to (rather than a revision of) RFC 822.
-
- This particular document is the third document in the series. It
- describes extensions to RFC 822 to allow non-US-ASCII text data in
- Internet mail header fields.
-
-
-
-
-
-
-
-
-
-Moore Standards Track [Page 1]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- Other documents in this series include:
-
- + RFC 2045, which specifies the various headers used to describe
- the structure of MIME messages.
-
- + RFC 2046, which defines the general structure of the MIME media
- typing system and defines an initial set of media types,
-
- + RFC 2048, which specifies various IANA registration procedures
- for MIME-related facilities, and
-
- + RFC 2049, which describes MIME conformance criteria and
- provides some illustrative examples of MIME message formats,
- acknowledgements, and the bibliography.
-
- These documents are revisions of RFCs 1521, 1522, and 1590, which
- themselves were revisions of RFCs 1341 and 1342. An appendix in RFC
- 2049 describes differences and changes from previous versions.
-
-1. Introduction
-
- RFC 2045 describes a mechanism for denoting textual body parts which
- are coded in various character sets, as well as methods for encoding
- such body parts as sequences of printable US-ASCII characters. This
- memo describes similar techniques to allow the encoding of non-ASCII
- text in various portions of a RFC 822 [2] message header, in a manner
- which is unlikely to confuse existing message handling software.
-
- Like the encoding techniques described in RFC 2045, the techniques
- outlined here were designed to allow the use of non-ASCII characters
- in message headers in a way which is unlikely to be disturbed by the
- quirks of existing Internet mail handling programs. In particular,
- some mail relaying programs are known to (a) delete some message
- header fields while retaining others, (b) rearrange the order of
- addresses in To or Cc fields, (c) rearrange the (vertical) order of
- header fields, and/or (d) "wrap" message headers at different places
- than those in the original message. In addition, some mail reading
- programs are known to have difficulty correctly parsing message
- headers which, while legal according to RFC 822, make use of
- backslash-quoting to "hide" special characters such as "<", ",", or
- ":", or which exploit other infrequently-used features of that
- specification.
-
- While it is unfortunate that these programs do not correctly
- interpret RFC 822 headers, to "break" these programs would cause
- severe operational problems for the Internet mail system. The
- extensions described in this memo therefore do not rely on little-
- used features of RFC 822.
-
-
-
-Moore Standards Track [Page 2]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- Instead, certain sequences of "ordinary" printable ASCII characters
- (known as "encoded-words") are reserved for use as encoded data. The
- syntax of encoded-words is such that they are unlikely to
- "accidentally" appear as normal text in message headers.
- Furthermore, the characters used in encoded-words are restricted to
- those which do not have special meanings in the context in which the
- encoded-word appears.
-
- Generally, an "encoded-word" is a sequence of printable ASCII
- characters that begins with "=?", ends with "?=", and has two "?"s in
- between. It specifies a character set and an encoding method, and
- also includes the original text encoded as graphic ASCII characters,
- according to the rules for that encoding method.
-
- A mail composer that implements this specification will provide a
- means of inputting non-ASCII text in header fields, but will
- translate these fields (or appropriate portions of these fields) into
- encoded-words before inserting them into the message header.
-
- A mail reader that implements this specification will recognize
- encoded-words when they appear in certain portions of the message
- header. Instead of displaying the encoded-word "as is", it will
- reverse the encoding and display the original text in the designated
- character set.
-
-NOTES
-
- This memo relies heavily on notation and terms defined RFC 822 and
- RFC 2045. In particular, the syntax for the ABNF used in this memo
- is defined in RFC 822, as well as many of the terminal or nonterminal
- symbols from RFC 822 are used in the grammar for the header
- extensions defined here. Among the symbols defined in RFC 822 and
- referenced in this memo are: 'addr-spec', 'atom', 'CHAR', 'comment',
- 'CTLs', 'ctext', 'linear-white-space', 'phrase', 'quoted-pair'.
- 'quoted-string', 'SPACE', and 'word'. Successful implementation of
- this protocol extension requires careful attention to the RFC 822
- definitions of these terms.
-
- When the term "ASCII" appears in this memo, it refers to the "7-Bit
- American Standard Code for Information Interchange", ANSI X3.4-1986.
- The MIME charset name for this character set is "US-ASCII". When not
- specifically referring to the MIME charset name, this document uses
- the term "ASCII", both for brevity and for consistency with RFC 822.
- However, implementors are warned that the character set name must be
- spelled "US-ASCII" in MIME message and body part headers.
-
-
-
-
-
-
-Moore Standards Track [Page 3]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- This memo specifies a protocol for the representation of non-ASCII
- text in message headers. It specifically DOES NOT define any
- translation between "8-bit headers" and pure ASCII headers, nor is
- any such translation assumed to be possible.
-
-2. Syntax of encoded-words
-
- An 'encoded-word' is defined by the following ABNF grammar. The
- notation of RFC 822 is used, with the exception that white space
- characters MUST NOT appear between components of an 'encoded-word'.
-
- encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
-
- charset = token ; see section 3
-
- encoding = token ; see section 4
-
- token = 1*<Any CHAR except SPACE, CTLs, and especials>
-
- especials = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "
- <"> / "/" / "[" / "]" / "?" / "." / "="
-
- encoded-text = 1*<Any printable ASCII character other than "?"
- or SPACE>
- ; (but see "Use of encoded-words in message
- ; headers", section 5)
-
- Both 'encoding' and 'charset' names are case-independent. Thus the
- charset name "ISO-8859-1" is equivalent to "iso-8859-1", and the
- encoding named "Q" may be spelled either "Q" or "q".
-
- An 'encoded-word' may not be more than 75 characters long, including
- 'charset', 'encoding', 'encoded-text', and delimiters. If it is
- desirable to encode more text than will fit in an 'encoded-word' of
- 75 characters, multiple 'encoded-word's (separated by CRLF SPACE) may
- be used.
-
- While there is no limit to the length of a multiple-line header
- field, each line of a header field that contains one or more
- 'encoded-word's is limited to 76 characters.
-
- The length restrictions are included both to ease interoperability
- through internetwork mail gateways, and to impose a limit on the
- amount of lookahead a header parser must employ (while looking for a
- final ?= delimiter) before it can decide whether a token is an
- "encoded-word" or something else.
-
-
-
-
-
-Moore Standards Track [Page 4]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- IMPORTANT: 'encoded-word's are designed to be recognized as 'atom's
- by an RFC 822 parser. As a consequence, unencoded white space
- characters (such as SPACE and HTAB) are FORBIDDEN within an
- 'encoded-word'. For example, the character sequence
-
- =?iso-8859-1?q?this is some text?=
-
- would be parsed as four 'atom's, rather than as a single 'atom' (by
- an RFC 822 parser) or 'encoded-word' (by a parser which understands
- 'encoded-words'). The correct way to encode the string "this is some
- text" is to encode the SPACE characters as well, e.g.
-
- =?iso-8859-1?q?this=20is=20some=20text?=
-
- The characters which may appear in 'encoded-text' are further
- restricted by the rules in section 5.
-
-3. Character sets
-
- The 'charset' portion of an 'encoded-word' specifies the character
- set associated with the unencoded text. A 'charset' can be any of
- the character set names allowed in an MIME "charset" parameter of a
- "text/plain" body part, or any character set name registered with
- IANA for use with the MIME text/plain content-type.
-
- Some character sets use code-switching techniques to switch between
- "ASCII mode" and other modes. If unencoded text in an 'encoded-word'
- contains a sequence which causes the charset interpreter to switch
- out of ASCII mode, it MUST contain additional control codes such that
- ASCII mode is again selected at the end of the 'encoded-word'. (This
- rule applies separately to each 'encoded-word', including adjacent
- 'encoded-word's within a single header field.)
-
- When there is a possibility of using more than one character set to
- represent the text in an 'encoded-word', and in the absence of
- private agreements between sender and recipients of a message, it is
- recommended that members of the ISO-8859-* series be used in
- preference to other character sets.
-
-4. Encodings
-
- Initially, the legal values for "encoding" are "Q" and "B". These
- encodings are described below. The "Q" encoding is recommended for
- use when most of the characters to be encoded are in the ASCII
- character set; otherwise, the "B" encoding should be used.
- Nevertheless, a mail reader which claims to recognize 'encoded-word's
- MUST be able to accept either encoding for any character set which it
- supports.
-
-
-
-Moore Standards Track [Page 5]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- Only a subset of the printable ASCII characters may be used in
- 'encoded-text'. Space and tab characters are not allowed, so that
- the beginning and end of an 'encoded-word' are obvious. The "?"
- character is used within an 'encoded-word' to separate the various
- portions of the 'encoded-word' from one another, and thus cannot
- appear in the 'encoded-text' portion. Other characters are also
- illegal in certain contexts. For example, an 'encoded-word' in a
- 'phrase' preceding an address in a From header field may not contain
- any of the "specials" defined in RFC 822. Finally, certain other
- characters are disallowed in some contexts, to ensure reliability for
- messages that pass through internetwork mail gateways.
-
- The "B" encoding automatically meets these requirements. The "Q"
- encoding allows a wide range of printable characters to be used in
- non-critical locations in the message header (e.g., Subject), with
- fewer characters available for use in other locations.
-
-4.1. The "B" encoding
-
- The "B" encoding is identical to the "BASE64" encoding defined by RFC
- 2045.
-
-4.2. The "Q" encoding
-
- The "Q" encoding is similar to the "Quoted-Printable" content-
- transfer-encoding defined in RFC 2045. It is designed to allow text
- containing mostly ASCII characters to be decipherable on an ASCII
- terminal without decoding.
-
- (1) Any 8-bit value may be represented by a "=" followed by two
- hexadecimal digits. For example, if the character set in use
- were ISO-8859-1, the "=" character would thus be encoded as
- "=3D", and a SPACE by "=20". (Upper case should be used for
- hexadecimal digits "A" through "F".)
-
- (2) The 8-bit hexadecimal value 20 (e.g., ISO-8859-1 SPACE) may be
- represented as "_" (underscore, ASCII 95.). (This character may
- not pass through some internetwork mail gateways, but its use
- will greatly enhance readability of "Q" encoded data with mail
- readers that do not support this encoding.) Note that the "_"
- always represents hexadecimal 20, even if the SPACE character
- occupies a different code position in the character set in use.
-
- (3) 8-bit values which correspond to printable ASCII characters other
- than "=", "?", and "_" (underscore), MAY be represented as those
- characters. (But see section 5 for restrictions.) In
- particular, SPACE and TAB MUST NOT be represented as themselves
- within encoded words.
-
-
-
-Moore Standards Track [Page 6]
-
-RFC 2047 Message Header Extensions November 1996
-
-
-5. Use of encoded-words in message headers
-
- An 'encoded-word' may appear in a message header or body part header
- according to the following rules:
-
-(1) An 'encoded-word' may replace a 'text' token (as defined by RFC 822)
- in any Subject or Comments header field, any extension message
- header field, or any MIME body part field for which the field body
- is defined as '*text'. An 'encoded-word' may also appear in any
- user-defined ("X-") message or body part header field.
-
- Ordinary ASCII text and 'encoded-word's may appear together in the
- same header field. However, an 'encoded-word' that appears in a
- header field defined as '*text' MUST be separated from any adjacent
- 'encoded-word' or 'text' by 'linear-white-space'.
-
-(2) An 'encoded-word' may appear within a 'comment' delimited by "(" and
- ")", i.e., wherever a 'ctext' is allowed. More precisely, the RFC
- 822 ABNF definition for 'comment' is amended as follows:
-
- comment = "(" *(ctext / quoted-pair / comment / encoded-word) ")"
-
- A "Q"-encoded 'encoded-word' which appears in a 'comment' MUST NOT
- contain the characters "(", ")" or "
- 'encoded-word' that appears in a 'comment' MUST be separated from
- any adjacent 'encoded-word' or 'ctext' by 'linear-white-space'.
-
- It is important to note that 'comment's are only recognized inside
- "structured" field bodies. In fields whose bodies are defined as
- '*text', "(" and ")" are treated as ordinary characters rather than
- comment delimiters, and rule (1) of this section applies. (See RFC
- 822, sections 3.1.2 and 3.1.3)
-
-(3) As a replacement for a 'word' entity within a 'phrase', for example,
- one that precedes an address in a From, To, or Cc header. The ABNF
- definition for 'phrase' from RFC 822 thus becomes:
-
- phrase = 1*( encoded-word / word )
-
- In this case the set of characters that may be used in a "Q"-encoded
- 'encoded-word' is restricted to: <upper and lower case ASCII
- letters, decimal digits, "!", "*", "+", "-", "/", "=", and "_"
- (underscore, ASCII 95.)>. An 'encoded-word' that appears within a
- 'phrase' MUST be separated from any adjacent 'word', 'text' or
- 'special' by 'linear-white-space'.
-
-
-
-
-
-
-Moore Standards Track [Page 7]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- These are the ONLY locations where an 'encoded-word' may appear. In
- particular:
-
- + An 'encoded-word' MUST NOT appear in any portion of an 'addr-spec'.
-
- + An 'encoded-word' MUST NOT appear within a 'quoted-string'.
-
- + An 'encoded-word' MUST NOT be used in a Received header field.
-
- + An 'encoded-word' MUST NOT be used in parameter of a MIME
- Content-Type or Content-Disposition field, or in any structured
- field body except within a 'comment' or 'phrase'.
-
- The 'encoded-text' in an 'encoded-word' must be self-contained;
- 'encoded-text' MUST NOT be continued from one 'encoded-word' to
- another. This implies that the 'encoded-text' portion of a "B"
- 'encoded-word' will be a multiple of 4 characters long; for a "Q"
- 'encoded-word', any "=" character that appears in the 'encoded-text'
- portion will be followed by two hexadecimal characters.
-
- Each 'encoded-word' MUST encode an integral number of octets. The
- 'encoded-text' in each 'encoded-word' must be well-formed according
- to the encoding specified; the 'encoded-text' may not be continued in
- the next 'encoded-word'. (For example, "=?charset?Q?=?=
- =?charset?Q?AB?=" would be illegal, because the two hex digits "AB"
- must follow the "=" in the same 'encoded-word'.)
-
- Each 'encoded-word' MUST represent an integral number of characters.
- A multi-octet character may not be split across adjacent 'encoded-
- word's.
-
- Only printable and white space character data should be encoded using
- this scheme. However, since these encoding schemes allow the
- encoding of arbitrary octet values, mail readers that implement this
- decoding should also ensure that display of the decoded data on the
- recipient's terminal will not cause unwanted side-effects.
-
- Use of these methods to encode non-textual data (e.g., pictures or
- sounds) is not defined by this memo. Use of 'encoded-word's to
- represent strings of purely ASCII characters is allowed, but
- discouraged. In rare cases it may be necessary to encode ordinary
- text that looks like an 'encoded-word'.
-
-
-
-
-
-
-
-
-
-Moore Standards Track [Page 8]
-
-RFC 2047 Message Header Extensions November 1996
-
-
-6. Support of 'encoded-word's by mail readers
-
-6.1. Recognition of 'encoded-word's in message headers
-
- A mail reader must parse the message and body part headers according
- to the rules in RFC 822 to correctly recognize 'encoded-word's.
-
- 'encoded-word's are to be recognized as follows:
-
- (1) Any message or body part header field defined as '*text', or any
- user-defined header field, should be parsed as follows: Beginning
- at the start of the field-body and immediately following each
- occurrence of 'linear-white-space', each sequence of up to 75
- printable characters (not containing any 'linear-white-space')
- should be examined to see if it is an 'encoded-word' according to
- the syntax rules in section 2. Any other sequence of printable
- characters should be treated as ordinary ASCII text.
-
- (2) Any header field not defined as '*text' should be parsed
- according to the syntax rules for that header field. However,
- any 'word' that appears within a 'phrase' should be treated as an
- 'encoded-word' if it meets the syntax rules in section 2.
- Otherwise it should be treated as an ordinary 'word'.
-
- (3) Within a 'comment', any sequence of up to 75 printable characters
- (not containing 'linear-white-space'), that meets the syntax
- rules in section 2, should be treated as an 'encoded-word'.
- Otherwise it should be treated as normal comment text.
-
- (4) A MIME-Version header field is NOT required to be present for
- 'encoded-word's to be interpreted according to this
- specification. One reason for this is that the mail reader is
- not expected to parse the entire message header before displaying
- lines that may contain 'encoded-word's.
-
-6.2. Display of 'encoded-word's
-
- Any 'encoded-word's so recognized are decoded, and if possible, the
- resulting unencoded text is displayed in the original character set.
-
- NOTE: Decoding and display of encoded-words occurs *after* a
- structured field body is parsed into tokens. It is therefore
- possible to hide 'special' characters in encoded-words which, when
- displayed, will be indistinguishable from 'special' characters in the
- surrounding text. For this and other reasons, it is NOT generally
- possible to translate a message header containing 'encoded-word's to
- an unencoded form which can be parsed by an RFC 822 mail reader.
-
-
-
-
-Moore Standards Track [Page 9]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- When displaying a particular header field that contains multiple
- 'encoded-word's, any 'linear-white-space' that separates a pair of
- adjacent 'encoded-word's is ignored. (This is to allow the use of
- multiple 'encoded-word's to represent long strings of unencoded text,
- without having to separate 'encoded-word's where spaces occur in the
- unencoded text.)
-
- In the event other encodings are defined in the future, and the mail
- reader does not support the encoding used, it may either (a) display
- the 'encoded-word' as ordinary text, or (b) substitute an appropriate
- message indicating that the text could not be decoded.
-
- If the mail reader does not support the character set used, it may
- (a) display the 'encoded-word' as ordinary text (i.e., as it appears
- in the header), (b) make a "best effort" to display using such
- characters as are available, or (c) substitute an appropriate message
- indicating that the decoded text could not be displayed.
-
- If the character set being used employs code-switching techniques,
- display of the encoded text implicitly begins in "ASCII mode". In
- addition, the mail reader must ensure that the output device is once
- again in "ASCII mode" after the 'encoded-word' is displayed.
-
-6.3. Mail reader handling of incorrectly formed 'encoded-word's
-
- It is possible that an 'encoded-word' that is legal according to the
- syntax defined in section 2, is incorrectly formed according to the
- rules for the encoding being used. For example:
-
- (1) An 'encoded-word' which contains characters which are not legal
- for a particular encoding (for example, a "-" in the "B"
- encoding, or a SPACE or HTAB in either the "B" or "Q" encoding),
- is incorrectly formed.
-
- (2) Any 'encoded-word' which encodes a non-integral number of
- characters or octets is incorrectly formed.
-
- A mail reader need not attempt to display the text associated with an
- 'encoded-word' that is incorrectly formed. However, a mail reader
- MUST NOT prevent the display or handling of a message because an
- 'encoded-word' is incorrectly formed.
-
-7. Conformance
-
- A mail composing program claiming compliance with this specification
- MUST ensure that any string of non-white-space printable ASCII
- characters within a '*text' or '*ctext' that begins with "=?" and
- ends with "?=" be a valid 'encoded-word'. ("begins" means: at the
-
-
-
-Moore Standards Track [Page 10]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- start of the field-body, immediately following 'linear-white-space',
- or immediately following a "(" for an 'encoded-word' within '*ctext';
- "ends" means: at the end of the field-body, immediately preceding
- 'linear-white-space', or immediately preceding a ")" for an
- 'encoded-word' within '*ctext'.) In addition, any 'word' within a
- 'phrase' that begins with "=?" and ends with "?=" must be a valid
- 'encoded-word'.
-
- A mail reading program claiming compliance with this specification
- must be able to distinguish 'encoded-word's from 'text', 'ctext', or
- 'word's, according to the rules in section 6, anytime they appear in
- appropriate places in message headers. It must support both the "B"
- and "Q" encodings for any character set which it supports. The
- program must be able to display the unencoded text if the character
- set is "US-ASCII". For the ISO-8859-* character sets, the mail
- reading program must at least be able to display the characters which
- are also in the ASCII set.
-
-8. Examples
-
- The following are examples of message headers containing 'encoded-
- word's:
-
- From: =?US-ASCII?Q?Keith_Moore?= <moore@cs.utk.edu>
- To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld@dkuug.dk>
- CC: =?ISO-8859-1?Q?Andr=E9?= Pirard <PIRARD@vm1.ulg.ac.be>
- Subject: =?ISO-8859-1?B?SWYgeW91IGNhbiByZWFkIHRoaXMgeW8=?=
- =?ISO-8859-2?B?dSB1bmRlcnN0YW5kIHRoZSBleGFtcGxlLg==?=
-
- Note: In the first 'encoded-word' of the Subject field above, the
- last "=" at the end of the 'encoded-text' is necessary because each
- 'encoded-word' must be self-contained (the "=" character completes a
- group of 4 base64 characters representing 2 octets). An additional
- octet could have been encoded in the first 'encoded-word' (so that
- the encoded-word would contain an exact multiple of 3 encoded
- octets), except that the second 'encoded-word' uses a different
- 'charset' than the first one.
-
- From: =?ISO-8859-1?Q?Olle_J=E4rnefors?= <ojarnef@admin.kth.se>
- To: ietf-822@dimacs.rutgers.edu, ojarnef@admin.kth.se
- Subject: Time for ISO 10646?
-
- To: Dave Crocker <dcrocker@mordor.stanford.edu>
- Cc: ietf-822@dimacs.rutgers.edu, paf@comsol.se
- From: =?ISO-8859-1?Q?Patrik_F=E4ltstr=F6m?= <paf@nada.kth.se>
- Subject: Re: RFC-HDR care and feeding
-
-
-
-
-
-Moore Standards Track [Page 11]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- From: Nathaniel Borenstein <nsb@thumper.bellcore.com>
- (=?iso-8859-8?b?7eXs+SDv4SDp7Oj08A==?=)
- To: Greg Vaudreuil <gvaudre@NRI.Reston.VA.US>, Ned Freed
- <ned@innosoft.com>, Keith Moore <moore@cs.utk.edu>
- Subject: Test of new header generator
- MIME-Version: 1.0
- Content-type: text/plain; charset=ISO-8859-1
-
- The following examples illustrate how text containing 'encoded-word's
- which appear in a structured field body. The rules are slightly
- different for fields defined as '*text' because "(" and ")" are not
- recognized as 'comment' delimiters. [Section 5, paragraph (1)].
-
- In each of the following examples, if the same sequence were to occur
- in a '*text' field, the "displayed as" form would NOT be treated as
- encoded words, but be identical to the "encoded form". This is
- because each of the encoded-words in the following examples is
- adjacent to a "(" or ")" character.
-
- encoded form displayed as
- ---------------------------------------------------------------------
- (=?ISO-8859-1?Q?a?=) (a)
-
- (=?ISO-8859-1?Q?a?= b) (a b)
-
- Within a 'comment', white space MUST appear between an
- 'encoded-word' and surrounding text. [Section 5,
- paragraph (2)]. However, white space is not needed between
- the initial "(" that begins the 'comment', and the
- 'encoded-word'.
-
-
- (=?ISO-8859-1?Q?a?= =?ISO-8859-1?Q?b?=) (ab)
-
- White space between adjacent 'encoded-word's is not
- displayed.
-
- (=?ISO-8859-1?Q?a?= =?ISO-8859-1?Q?b?=) (ab)
-
- Even multiple SPACEs between 'encoded-word's are ignored
- for the purpose of display.
-
- (=?ISO-8859-1?Q?a?= (ab)
- =?ISO-8859-1?Q?b?=)
-
- Any amount of linear-space-white between 'encoded-word's,
- even if it includes a CRLF followed by one or more SPACEs,
- is ignored for the purposes of display.
-
-
-
-Moore Standards Track [Page 12]
-
-RFC 2047 Message Header Extensions November 1996
-
-
- (=?ISO-8859-1?Q?a_b?=) (a b)
-
- In order to cause a SPACE to be displayed within a portion
- of encoded text, the SPACE MUST be encoded as part of the
- 'encoded-word'.
-
- (=?ISO-8859-1?Q?a?= =?ISO-8859-2?Q?_b?=) (a b)
-
- In order to cause a SPACE to be displayed between two strings
- of encoded text, the SPACE MAY be encoded as part of one of
- the 'encoded-word's.
-
-9. References
-
- [RFC 822] Crocker, D., "Standard for the Format of ARPA Internet Text
- Messages", STD 11, RFC 822, UDEL, August 1982.
-
- [RFC 2049] Borenstein, N., and N. Freed, "Multipurpose Internet Mail
- Extensions (MIME) Part Five: Conformance Criteria and Examples",
- RFC 2049, November 1996.
-
- [RFC 2045] Borenstein, N., and N. Freed, "Multipurpose Internet Mail
- Extensions (MIME) Part One: Format of Internet Message Bodies",
- RFC 2045, November 1996.
-
- [RFC 2046] Borenstein N., and N. Freed, "Multipurpose Internet Mail
- Extensions (MIME) Part Two: Media Types", RFC 2046,
- November 1996.
-
- [RFC 2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) Part Four: Registration
- Procedures", RFC 2048, November 1996.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Moore Standards Track [Page 13]
-
-RFC 2047 Message Header Extensions November 1996
-
-
-10. Security Considerations
-
- Security issues are not discussed in this memo.
-
-11. Acknowledgements
-
- The author wishes to thank Nathaniel Borenstein, Issac Chan, Lutz
- Donnerhacke, Paul Eggert, Ned Freed, Andreas M. Kirchwitz, Olle
- Jarnefors, Mike Rosin, Yutaka Sato, Bart Schaefer, and Kazuhiko
- Yamamoto, for their helpful advice, insightful comments, and
- illuminating questions in response to earlier versions of this
- specification.
-
-12. Author's Address
-
- Keith Moore
- University of Tennessee
- 107 Ayres Hall
- Knoxville TN 37996-1301
-
- EMail: moore@cs.utk.edu
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Moore Standards Track [Page 14]
-
-RFC 2047 Message Header Extensions November 1996
-
-
-Appendix - changes since RFC 1522 (in no particular order)
-
- + explicitly state that the MIME-Version is not requried to use
- 'encoded-word's.
-
- + add explicit note that SPACEs and TABs are not allowed within
- 'encoded-word's, explaining that an 'encoded-word' must look like an
- 'atom' to an RFC822 parser.values, to be precise).
-
- + add examples from Olle Jarnefors (thanks!) which illustrate how
- encoded-words with adjacent linear-white-space are displayed.
-
- + explicitly list terms defined in RFC822 and referenced in this memo
-
- + fix transcription typos that caused one or two lines and a couple of
- characters to disappear in the resulting text, due to nroff quirks.
-
- + clarify that encoded-words are allowed in '*text' fields in both
- RFC822 headers and MIME body part headers, but NOT as parameter
- values.
-
- + clarify the requirement to switch back to ASCII within the encoded
- portion of an 'encoded-word', for any charset that uses code switching
- sequences.
-
- + add a note about 'encoded-word's being delimited by "(" and ")"
- within a comment, but not in a *text (how bizarre!).
-
- + fix the Andre Pirard example to get rid of the trailing "_" after
- the =E9. (no longer needed post-1342).
-
- + clarification: an 'encoded-word' may appear immediately following
- the initial "(" or immediately before the final ")" that delimits a
- comment, not just adjacent to "(" and ")" *within* *ctext.
-
- + add a note to explain that a "B" 'encoded-word' will always have a
- multiple of 4 characters in the 'encoded-text' portion.
-
- + add note about the "=" in the examples
-
- + note that processing of 'encoded-word's occurs *after* parsing, and
- some of the implications thereof.
-
- + explicitly state that you can't expect to translate between
- 1522 and either vanilla 822 or so-called "8-bit headers".
-
- + explicitly state that 'encoded-word's are not valid within a
- 'quoted-string'.
-
-
-
-Moore Standards Track [Page 15]
-
diff --git a/proto/rfc2048.txt b/proto/rfc2048.txt
@@ -1,1180 +0,0 @@
-
-
-
-
-
-
-Network Working Group N. Freed
-Request for Comments: 2048 Innosoft
-BCP: 13 J. Klensin
-Obsoletes: 1521, 1522, 1590 MCI
-Category: Best Current Practice J. Postel
- ISI
- November 1996
-
-
- Multipurpose Internet Mail Extensions
- (MIME) Part Four:
- Registration Procedures
-
-Status of this Memo
-
- This document specifies an Internet Best Current Practices for the
- Internet Community, and requests discussion and suggestions for
- improvements. Distribution of this memo is unlimited.
-
-Abstract
-
- STD 11, RFC 822, defines a message representation protocol specifying
- considerable detail about US-ASCII message headers, and leaves the
- message content, or message body, as flat US-ASCII text. This set of
- documents, collectively called the Multipurpose Internet Mail
- Extensions, or MIME, redefines the format of messages to allow for
-
- (1) textual message bodies in character sets other than
- US-ASCII,
-
- (2) an extensible set of different formats for non-textual
- message bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than
- US-ASCII.
-
- These documents are based on earlier work documented in RFC 934, STD
- 11, and RFC 1049, but extends and revises them. Because RFC 822 said
- so little about message bodies, these documents are largely
- orthogonal to (rather than a revision of) RFC 822.
-
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 1]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- This fourth document, RFC 2048, specifies various IANA registration
- procedures for the following MIME facilities:
-
- (1) media types,
-
- (2) external body access types,
-
- (3) content-transfer-encodings.
-
- Registration of character sets for use in MIME is covered elsewhere
- and is no longer addressed by this document.
-
- These documents are revisions of RFCs 1521 and 1522, which themselves
- were revisions of RFCs 1341 and 1342. An appendix in RFC 2049
- describes differences and changes from previous versions.
-
-Table of Contents
-
- 1. Introduction ......................................... 3
- 2. Media Type Registration .............................. 4
- 2.1 Registration Trees and Subtype Names ................ 4
- 2.1.1 IETF Tree ......................................... 4
- 2.1.2 Vendor Tree ....................................... 4
- 2.1.3 Personal or Vanity Tree ........................... 5
- 2.1.4 Special `x.' Tree ................................. 5
- 2.1.5 Additional Registration Trees ..................... 6
- 2.2 Registration Requirements ........................... 6
- 2.2.1 Functionality Requirement ......................... 6
- 2.2.2 Naming Requirements ............................... 6
- 2.2.3 Parameter Requirements ............................ 7
- 2.2.4 Canonicalization and Format Requirements .......... 7
- 2.2.5 Interchange Recommendations ....................... 8
- 2.2.6 Security Requirements ............................. 8
- 2.2.7 Usage and Implementation Non-requirements ......... 9
- 2.2.8 Publication Requirements .......................... 10
- 2.2.9 Additional Information ............................ 10
- 2.3 Registration Procedure .............................. 11
- 2.3.1 Present the Media Type to the Community for Review 11
- 2.3.2 IESG Approval ..................................... 12
- 2.3.3 IANA Registration ................................. 12
- 2.4 Comments on Media Type Registrations ................ 12
- 2.5 Location of Registered Media Type List .............. 12
- 2.6 IANA Procedures for Registering Media Types ......... 12
- 2.7 Change Control ...................................... 13
- 2.8 Registration Template ............................... 14
- 3. External Body Access Types ........................... 14
- 3.1 Registration Requirements ........................... 15
- 3.1.1 Naming Requirements ............................... 15
-
-
-
-Freed, et. al. Best Current Practice [Page 2]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- 3.1.2 Mechanism Specification Requirements .............. 15
- 3.1.3 Publication Requirements .......................... 15
- 3.1.4 Security Requirements ............................. 15
- 3.2 Registration Procedure .............................. 15
- 3.2.1 Present the Access Type to the Community .......... 16
- 3.2.2 Access Type Reviewer .............................. 16
- 3.2.3 IANA Registration ................................. 16
- 3.3 Location of Registered Access Type List ............. 16
- 3.4 IANA Procedures for Registering Access Types ........ 16
- 4. Transfer Encodings ................................... 17
- 4.1 Transfer Encoding Requirements ...................... 17
- 4.1.1 Naming Requirements ............................... 17
- 4.1.2 Algorithm Specification Requirements .............. 18
- 4.1.3 Input Domain Requirements ......................... 18
- 4.1.4 Output Range Requirements ......................... 18
- 4.1.5 Data Integrity and Generality Requirements ........ 18
- 4.1.6 New Functionality Requirements .................... 18
- 4.2 Transfer Encoding Definition Procedure .............. 19
- 4.3 IANA Procedures for Transfer Encoding Registration... 19
- 4.4 Location of Registered Transfer Encodings List ...... 19
- 5. Authors' Addresses ................................... 20
- A. Grandfathered Media Types ............................ 21
-
-1. Introduction
-
- Recent Internet protocols have been carefully designed to be easily
- extensible in certain areas. In particular, MIME [RFC 2045] is an
- open-ended framework and can accommodate additional object types,
- character sets, and access methods without any changes to the basic
- protocol. A registration process is needed, however, to ensure that
- the set of such values is developed in an orderly, well-specified,
- and public manner.
-
- This document defines registration procedures which use the Internet
- Assigned Numbers Authority (IANA) as a central registry for such
- values.
-
- Historical Note: The registration process for media types was
- initially defined in the context of the asynchronous Internet mail
- environment. In this mail environment there is a need to limit the
- number of possible media types to increase the likelihood of
- interoperability when the capabilities of the remote mail system are
- not known. As media types are used in new environments, where the
- proliferation of media types is not a hindrance to interoperability,
- the original procedure was excessively restrictive and had to be
- generalized.
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 3]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-2. Media Type Registration
-
- Registration of a new media type or types starts with the
- construction of a registration proposal. Registration may occur in
- several different registration trees, which have different
- requirements as discussed below. In general, the new registration
- proposal is circulated and reviewed in a fashion appropriate to the
- tree involved. The media type is then registered if the proposal is
- acceptable. The following sections describe the requirements and
- procedures used for each of the different registration trees.
-
-2.1. Registration Trees and Subtype Names
-
- In order to increase the efficiency and flexibility of the
- registration process, different structures of subtype names may be
- registered to accomodate the different natural requirements for,
- e.g., a subtype that will be recommended for wide support and
- implementation by the Internet Community or a subtype that is used to
- move files associated with proprietary software. The following
- subsections define registration "trees", distinguished by the use of
- faceted names (e.g., names of the form "tree.subtree...type"). Note
- that some media types defined prior to this document do not conform
- to the naming conventions described below. See Appendix A for a
- discussion of them.
-
-2.1.1. IETF Tree
-
- The IETF tree is intended for types of general interest to the
- Internet Community. Registration in the IETF tree requires approval
- by the IESG and publication of the media type registration as some
- form of RFC.
-
- Media types in the IETF tree are normally denoted by names that are
- not explicitly faceted, i.e., do not contain period (".", full stop)
- characters.
-
- The "owner" of a media type registration in the IETF tree is assumed
- to be the IETF itself. Modification or alteration of the
- specification requires the same level of processing (e.g. standards
- track) required for the initial registration.
-
-2.1.2. Vendor Tree
-
- The vendor tree is used for media types associated with commercially
- available products. "Vendor" or "producer" are construed as
- equivalent and very broadly in this context.
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 4]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- A registration may be placed in the vendor tree by anyone who has
- need to interchange files associated with the particular product.
- However, the registration formally belongs to the vendor or
- organization producing the software or file format. Changes to the
- specification will be made at their request, as discussed in
- subsequent sections.
-
- Registrations in the vendor tree will be distinguished by the leading
- facet "vnd.". That may be followed, at the discretion of the
- registration, by either a media type name from a well-known producer
- (e.g., "vnd.mudpie") or by an IANA-approved designation of the
- producer's name which is then followed by a media type or product
- designation (e.g., vnd.bigcompany.funnypictures).
-
- While public exposure and review of media types to be registered in
- the vendor tree is not required, using the ietf-types list for review
- is strongly encouraged to improve the quality of those
- specifications. Registrations in the vendor tree may be submitted
- directly to the IANA.
-
-2.1.3. Personal or Vanity Tree
-
- Registrations for media types created experimentally or as part of
- products that are not distributed commercially may be registered in
- the personal or vanity tree. The registrations are distinguished by
- the leading facet "prs.".
-
- The owner of "personal" registrations and associated specifications
- is the person or entity making the registration, or one to whom
- responsibility has been transferred as described below.
-
- While public exposure and review of media types to be registered in
- the personal tree is not required, using the ietf-types list for
- review is strongly encouraged to improve the quality of those
- specifications. Registrations in the personl tree may be submitted
- directly to the IANA.
-
-2.1.4. Special `x.' Tree
-
- For convenience and symmetry with this registration scheme, media
- type names with "x." as the first facet may be used for the same
- purposes for which names starting in "x-" are normally used. These
- types are unregistered, experimental, and should be used only with
- the active agreement of the parties exchanging them.
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 5]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- However, with the simplified registration procedures described above
- for vendor and personal trees, it should rarely, if ever, be
- necessary to use unregistered experimental types, and as such use of
- both "x-" and "x." forms is discouraged.
-
-2.1.5. Additional Registration Trees
-
- From time to time and as required by the community, the IANA may,
- with the advice and consent of the IESG, create new top-level
- registration trees. It is explicitly assumed that these trees may be
- created for external registration and management by well-known
- permanent bodies, such as scientific societies for media types
- specific to the sciences they cover. In general, the quality of
- review of specifications for one of these additional registration
- trees is expected to be equivalent to that which IETF would give to
- registrations in its own tree. Establishment of these new trees will
- be announced through RFC publication approved by the IESG.
-
-2.2. Registration Requirements
-
- Media type registration proposals are all expected to conform to
- various requirements laid out in the following sections. Note that
- requirement specifics sometimes vary depending on the registration
- tree, again as detailed in the following sections.
-
-2.2.1. Functionality Requirement
-
- Media types must function as an actual media format: Registration of
- things that are better thought of as a transfer encoding, as a
- character set, or as a collection of separate entities of another
- type, is not allowed. For example, although applications exist to
- decode the base64 transfer encoding [RFC 2045], base64 cannot be
- registered as a media type.
-
- This requirement applies regardless of the registration tree
- involved.
-
-2.2.2. Naming Requirements
-
- All registered media types must be assigned MIME type and subtype
- names. The combination of these names then serves to uniquely
- identify the media type and the format of the subtype name identifies
- the registration tree.
-
- The choice of top-level type name must take the nature of media type
- involved into account. For example, media normally used for
- representing still images should be a subtype of the image content
- type, whereas media capable of representing audio information belongs
-
-
-
-Freed, et. al. Best Current Practice [Page 6]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- under the audio content type. See RFC 2046 for additional information
- on the basic set of top-level types and their characteristics.
-
- New subtypes of top-level types must conform to the restrictions of
- the top-level type, if any. For example, all subtypes of the
- multipart content type must use the same encapsulation syntax.
-
- In some cases a new media type may not "fit" under any currently
- defined top-level content type. Such cases are expected to be quite
- rare. However, if such a case arises a new top-level type can be
- defined to accommodate it. Such a definition must be done via
- standards-track RFC; no other mechanism can be used to define
- additional top-level content types.
-
- These requirements apply regardless of the registration tree
- involved.
-
-2.2.3. Parameter Requirements
-
- Media types may elect to use one or more MIME content type
- parameters, or some parameters may be automatically made available to
- the media type by virtue of being a subtype of a content type that
- defines a set of parameters applicable to any of its subtypes. In
- either case, the names, values, and meanings of any parameters must
- be fully specified when a media type is registered in the IETF tree,
- and should be specified as completely as possible when media types
- are registered in the vendor or personal trees.
-
- New parameters must not be defined as a way to introduce new
- functionality in types registered in the IETF tree, although new
- parameters may be added to convey additional information that does
- not otherwise change existing functionality. An example of this
- would be a "revision" parameter to indicate a revision level of an
- external specification such as JPEG. Similar behavior is encouraged
- for media types registered in the vendor or personal trees but is not
- required.
-
-2.2.4. Canonicalization and Format Requirements
-
- All registered media types must employ a single, canonical data
- format, regardless of registration tree.
-
- A precise and openly available specification of the format of each
- media type is required for all types registered in the IETF tree and
- must at a minimum be referenced by, if it isn't actually included in,
- the media type registration proposal itself.
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 7]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- The specifications of format and processing particulars may or may
- not be publically available for media types registered in the vendor
- tree, and such registration proposals are explicitly permitted to
- include only a specification of which software and version produce or
- process such media types. References to or inclusion of format
- specifications in registration proposals is encouraged but not
- required.
-
- Format specifications are still required for registration in the
- personal tree, but may be either published as RFCs or otherwise
- deposited with IANA. The deposited specifications will meet the same
- criteria as those required to register a well-known TCP port and, in
- particular, need not be made public.
-
- Some media types involve the use of patented technology. The
- registration of media types involving patented technology is
- specifically permitted. However, the restrictions set forth in RFC
- 1602 on the use of patented technology in standards-track protocols
- must be respected when the specification of a media type is part of a
- standards-track protocol.
-
-2.2.5. Interchange Recommendations
-
- Media types should, whenever possible, interoperate across as many
- systems and applications as possible. However, some media types will
- inevitably have problems interoperating across different platforms.
- Problems with different versions, byte ordering, and specifics of
- gateway handling can and will arise.
-
- Universal interoperability of media types is not required, but known
- interoperability issues should be identified whenever possible.
- Publication of a media type does not require an exhaustive review of
- interoperability, and the interoperability considerations section is
- subject to continuing evaluation.
-
- These recommendations apply regardless of the registration tree
- involved.
-
-2.2.6. Security Requirements
-
- An analysis of security issues is required for for all types
- registered in the IETF Tree. (This is in accordance with the basic
- requirements for all IETF protocols.) A similar analysis for media
- types registered in the vendor or personal trees is encouraged but
- not required. However, regardless of what security analysis has or
- has not been done, all descriptions of security issues must be as
- accurate as possible regardless of registration tree. In particular,
- a statement that there are "no security issues associated with this
-
-
-
-Freed, et. al. Best Current Practice [Page 8]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- type" must not be confused with "the security issues associates with
- this type have not been assessed".
-
- There is absolutely no requirement that media types registered in any
- tree be secure or completely free from risks. Nevertheless, all
- known security risks must be identified in the registration of a
- media type, again regardless of registration tree.
-
- The security considerations section of all registrations is subject
- to continuing evaluation and modification, and in particular may be
- extended by use of the "comments on media types" mechanism described
- in subsequent sections.
-
- Some of the issues that should be looked at in a security analysis of
- a media type are:
-
- (1) Complex media types may include provisions for
- directives that institute actions on a recipient's
- files or other resources. In many cases provision is
- made for originators to specify arbitrary actions in an
- unrestricted fashion which may then have devastating
- effects. See the registration of the
- application/postscript media type in RFC 2046 for
- an example of such directives and how to handle them.
-
- (2) Complex media types may include provisions for
- directives that institute actions which, while not
- directly harmful to the recipient, may result in
- disclosure of information that either facilitates a
- subsequent attack or else violates a recipient's
- privacy in some way. Again, the registration of the
- application/postscript media type illustrates how such
- directives can be handled.
-
- (3) A media type might be targeted for applications that
- require some sort of security assurance but not provide
- the necessary security mechanisms themselves. For
- example, a media type could be defined for storage of
- confidential medical information which in turn requires
- an external confidentiality service.
-
-2.2.7. Usage and Implementation Non-requirements
-
- In the asynchronous mail environment, where information on the
- capabilities of the remote mail agent is frequently not available to
- the sender, maximum interoperability is attained by restricting the
- number of media types used to those "common" formats expected to be
- widely implemented. This was asserted in the past as a reason to
-
-
-
-Freed, et. al. Best Current Practice [Page 9]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- limit the number of possible media types and resulted in a
- registration process with a significant hurdle and delay for those
- registering media types.
-
- However, the need for "common" media types does not require limiting
- the registration of new media types. If a limited set of media types
- is recommended for a particular application, that should be asserted
- by a separate applicability statement specific for the application
- and/or environment.
-
- As such, universal support and implementation of a media type is NOT
- a requirement for registration. If, however, a media type is
- explicitly intended for limited use, this should be noted in its
- registration.
-
-2.2.8. Publication Requirements
-
- Proposals for media types registered in the IETF tree must be
- published as RFCs. RFC publication of vendor and personal media type
- proposals is encouraged but not required. In all cases IANA will
- retain copies of all media type proposals and "publish" them as part
- of the media types registration tree itself.
-
- Other than in the IETF tree, the registration of a data type does not
- imply endorsement, approval, or recommendation by IANA or IETF or
- even certification that the specification is adequate. To become
- Internet Standards, protocol, data objects, or whatever must go
- through the IETF standards process. This is too difficult and too
- lengthy a process for the convenient registration of media types.
-
- The IETF tree exists for media types that do require require a
- substantive review and approval process with the vendor and personal
- trees exist for those that do not. It is expected that applicability
- statements for particular applications will be published from time to
- time that recommend implementation of, and support for, media types
- that have proven particularly useful in those contexts.
-
- As discussed above, registration of a top-level type requires
- standards-track processing and, hence, RFC publication.
-
-2.2.9. Additional Information
-
- Various sorts of optional information may be included in the
- specification of a media type if it is available:
-
- (1) Magic number(s) (length, octet values). Magic numbers
- are byte sequences that are always present and thus can
- be used to identify entities as being of a given media
-
-
-
-Freed, et. al. Best Current Practice [Page 10]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- type.
-
- (2) File extension(s) commonly used on one or more
- platforms to indicate that some file containing a given
- type of media.
-
- (3) Macintosh File Type code(s) (4 octets) used to label
- files containing a given type of media.
-
- Such information is often quite useful to implementors and if
- available should be provided.
-
-2.3. Registration Procedure
-
- The following procedure has been implemented by the IANA for review
- and approval of new media types. This is not a formal standards
- process, but rather an administrative procedure intended to allow
- community comment and sanity checking without excessive time delay.
- For registration in the IETF tree, the normal IETF processes should
- be followed, treating posting of an internet-draft and announcement
- on the ietf-types list (as described in the next subsection) as a
- first step. For registrations in the vendor or personal tree, the
- initial review step described below may be omitted and the type
- registered directly by submitting the template and an explanation
- directly to IANA (at iana@iana.org). However, authors of vendor or
- personal media type specifications are encouraged to seek community
- review and comment whenever that is feasible.
-
-2.3.1. Present the Media Type to the Community for Review
-
- Send a proposed media type registration to the "ietf-types@iana.org"
- mailing list for a two week review period. This mailing list has
- been established for the purpose of reviewing proposed media and
- access types. Proposed media types are not formally registered and
- must not be used; the "x-" prefix specified in RFC 2045 can be used
- until registration is complete.
-
- The intent of the public posting is to solicit comments and feedback
- on the choice of type/subtype name, the unambiguity of the references
- with respect to versions and external profiling information, and a
- review of any interoperability or security considerations. The
- submitter may submit a revised registration, or withdraw the
- registration completely, at any time.
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 11]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-2.3.2. IESG Approval
-
- Media types registered in the IETF tree must be submitted to the IESG
- for approval.
-
-2.3.3. IANA Registration
-
- Provided that the media type meets the requirements for media types
- and has obtained approval that is necessary, the author may submit
- the registration request to the IANA, which will register the media
- type and make the media type registration available to the community.
-
-2.4. Comments on Media Type Registrations
-
- Comments on registered media types may be submitted by members of the
- community to IANA. These comments will be passed on to the "owner"
- of the media type if possible. Submitters of comments may request
- that their comment be attached to the media type registration itself,
- and if IANA approves of this the comment will be made accessible in
- conjunction with the type registration itself.
-
-2.5. Location of Registered Media Type List
-
- Media type registrations will be posted in the anonymous FTP
- directory "ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/"
- and all registered media types will be listed in the periodically
- issued "Assigned Numbers" RFC [currently STD 2, RFC 1700]. The media
- type description and other supporting material may also be published
- as an Informational RFC by sending it to "rfc-editor@isi.edu" (please
- follow the instructions to RFC authors [RFC-1543]).
-
-2.6. IANA Procedures for Registering Media Types
-
- The IANA will only register media types in the IETF tree in response
- to a communication from the IESG stating that a given registration
- has been approved. Vendor and personal types will be registered by
- the IANA automatically and without any formal review as long as the
- following minimal conditions are met:
-
- (1) Media types must function as an actual media format.
- In particular, character sets and transfer encodings
- may not be registered as media types.
-
- (2) All media types must have properly formed type and
- subtype names. All type names must be defined by a
- standards-track RFC. All subtype names must be unique,
- must conform to the MIME grammar for such names, and
- must contain the proper tree prefix.
-
-
-
-Freed, et. al. Best Current Practice [Page 12]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- (3) Types registered in the personal tree must either
- provide a format specification or a pointer to one.
-
- (4) Any security considerations given must not be obviously
- bogus. (It is neither possible nor necessary for the
- IANA to conduct a comprehensive security review of
- media type registrations. Nevertheless, IANA has the
- authority to identify obviously incompetent material
- and exclude it.)
-
-2.7. Change Control
-
- Once a media type has been published by IANA, the author may request
- a change to its definition. The descriptions of the different
- registration trees above designate the "owners" of each type of
- registration. The change request follows the same procedure as the
- registration request:
-
- (1) Publish the revised template on the ietf-types list.
-
- (2) Leave at least two weeks for comments.
-
- (3) Publish using IANA after formal review if required.
-
- Changes should be requested only when there are serious omission or
- errors in the published specification. When review is required, a
- change request may be denied if it renders entities that were valid
- under the previous definition invalid under the new definition.
-
- The owner of a content type may pass responsibility for the content
- type to another person or agency by informing IANA and the ietf-types
- list; this can be done without discussion or review.
-
- The IESG may reassign responsibility for a media type. The most
- common case of this will be to enable changes to be made to types
- where the author of the registration has died, moved out of contact
- or is otherwise unable to make changes that are important to the
- community.
-
- Media type registrations may not be deleted; media types which are no
- longer believed appropriate for use can be declared OBSOLETE by a
- change to their "intended use" field; such media types will be
- clearly marked in the lists published by IANA.
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 13]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-2.8. Registration Template
-
- To: ietf-types@iana.org
- Subject: Registration of MIME media type XXX/YYY
-
- MIME media type name:
-
- MIME subtype name:
-
- Required parameters:
-
- Optional parameters:
-
- Encoding considerations:
-
- Security considerations:
-
- Interoperability considerations:
-
- Published specification:
-
- Applications which use this media type:
-
- Additional information:
-
- Magic number(s):
- File extension(s):
- Macintosh File Type Code(s):
-
- Person & email address to contact for further information:
-
- Intended usage:
-
- (One of COMMON, LIMITED USE or OBSOLETE)
-
- Author/Change controller:
-
- (Any other information that the author deems interesting may be
- added below this line.)
-
-3. External Body Access Types
-
- RFC 2046 defines the message/external-body media type, whereby a MIME
- entity can act as pointer to the actual body data in lieu of
- including the data directly in the entity body. Each
- message/external-body reference specifies an access type, which
- determines the mechanism used to retrieve the actual body data. RFC
- 2046 defines an initial set of access types, but allows for the
-
-
-
-Freed, et. al. Best Current Practice [Page 14]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
- registration of additional access types to accommodate new retrieval
- mechanisms.
-
-3.1. Registration Requirements
-
- New access type specifications must conform to a number of
- requirements as described below.
-
-3.1.1. Naming Requirements
-
- Each access type must have a unique name. This name appears in the
- access-type parameter in the message/external-body content-type
- header field, and must conform to MIME content type parameter syntax.
-
-3.1.2. Mechanism Specification Requirements
-
- All of the protocols, transports, and procedures used by a given
- access type must be described, either in the specification of the
- access type itself or in some other publicly available specification,
- in sufficient detail for the access type to be implemented by any
- competent implementor. Use of secret and/or proprietary methods in
- access types are expressly prohibited. The restrictions imposed by
- RFC 1602 on the standardization of patented algorithms must be
- respected as well.
-
-3.1.3. Publication Requirements
-
- All access types must be described by an RFC. The RFC may be
- informational rather than standards-track, although standard-track
- review and approval are encouraged for all access types.
-
-3.1.4. Security Requirements
-
- Any known security issues that arise from the use of the access type
- must be completely and fully described. It is not required that the
- access type be secure or that it be free from risks, but that the
- known risks be identified. Publication of a new access type does not
- require an exhaustive security review, and the security
- considerations section is subject to continuing evaluation.
- Additional security considerations should be addressed by publishing
- revised versions of the access type specification.
-
-3.2. Registration Procedure
-
- Registration of a new access type starts with the construction of a
- draft of an RFC.
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 15]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-3.2.1. Present the Access Type to the Community
-
- Send a proposed access type specification to the "ietf-
- types@iana.org" mailing list for a two week review period. This
- mailing list has been established for the purpose of reviewing
- proposed access and media types. Proposed access types are not
- formally registered and must not be used.
-
- The intent of the public posting is to solicit comments and feedback
- on the access type specification and a review of any security
- considerations.
-
-3.2.2. Access Type Reviewer
-
- When the two week period has passed, the access type reviewer, who is
- appointed by the IETF Applications Area Director, either forwards the
- request to iana@isi.edu, or rejects it because of significant
- objections raised on the list.
-
- Decisions made by the reviewer must be posted to the ietf-types
- mailing list within 14 days. Decisions made by the reviewer may be
- appealed to the IESG.
-
-3.2.3. IANA Registration
-
- Provided that the access type has either passed review or has been
- successfully appealed to the IESG, the IANA will register the access
- type and make the registration available to the community. The
- specification of the access type must also be published as an RFC.
- Informational RFCs are published by sending them to "rfc-
- editor@isi.edu" (please follow the instructions to RFC authors [RFC-
- 1543]).
-
-3.3. Location of Registered Access Type List
-
- Access type registrations will be posted in the anonymous FTP
- directory "ftp://ftp.isi.edu/in-notes/iana/assignments/access-types/"
- and all registered access types will be listed in the periodically
- issued "Assigned Numbers" RFC [currently RFC-1700].
-
-3.4. IANA Procedures for Registering Access Types
-
- The identity of the access type reviewer is communicated to the IANA
- by the IESG. The IANA then only acts in response to access type
- definitions that either are approved by the access type reviewer and
- forwarded by the reviewer to the IANA for registration, or in
- response to a communication from the IESG that an access type
- definition appeal has overturned the access type reviewer's ruling.
-
-
-
-Freed, et. al. Best Current Practice [Page 16]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-4. Transfer Encodings
-
- Transfer encodings are tranformations applied to MIME media types
- after conversion to the media type's canonical form. Transfer
- encodings are used for several purposes:
-
- (1) Many transports, especially message transports, can
- only handle data consisting of relatively short lines
- of text. There can also be severe restrictions on what
- characters can be used in these lines of text -- some
- transports are restricted to a small subset of US-ASCII
- and others cannot handle certain character sequences.
- Transfer encodings are used to transform binary data
- into textual form that can survive such transports.
- Examples of this sort of transfer encoding include the
- base64 and quoted-printable transfer encodings defined
- in RFC 2045.
-
- (2) Image, audio, video, and even application entities are
- sometimes quite large. Compression algorithms are often
- quite effective in reducing the size of large entities.
- Transfer encodings can be used to apply general-purpose
- non-lossy compression algorithms to MIME entities.
-
- (3) Transport encodings can be defined as a means of
- representing existing encoding formats in a MIME
- context.
-
- IMPORTANT: The standardization of a large numbers of different
- transfer encodings is seen as a significant barrier to widespread
- interoperability and is expressely discouraged. Nevertheless, the
- following procedure has been defined to provide a means of defining
- additional transfer encodings, should standardization actually be
- justified.
-
-4.1. Transfer Encoding Requirements
-
- Transfer encoding specifications must conform to a number of
- requirements as described below.
-
-4.1.1. Naming Requirements
-
- Each transfer encoding must have a unique name. This name appears in
- the Content-Transfer-Encoding header field and must conform to the
- syntax of that field.
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 17]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-4.1.2. Algorithm Specification Requirements
-
- All of the algorithms used in a transfer encoding (e.g. conversion
- to printable form, compression) must be described in their entirety
- in the transfer encoding specification. Use of secret and/or
- proprietary algorithms in standardized transfer encodings are
- expressly prohibited. The restrictions imposed by RFC 1602 on the
- standardization of patented algorithms must be respected as well.
-
-4.1.3. Input Domain Requirements
-
- All transfer encodings must be applicable to an arbitrary sequence of
- octets of any length. Dependence on particular input forms is not
- allowed.
-
- It should be noted that the 7bit and 8bit encodings do not conform to
- this requirement. Aside from the undesireability of having
- specialized encodings, the intent here is to forbid the addition of
- additional encodings along the lines of 7bit and 8bit.
-
-4.1.4. Output Range Requirements
-
- There is no requirement that a particular tranfer encoding produce a
- particular form of encoded output. However, the output format for
- each transfer encoding must be fully and completely documented. In
- particular, each specification must clearly state whether the output
- format always lies within the confines of 7bit data, 8bit data, or is
- simply pure binary data.
-
-4.1.5. Data Integrity and Generality Requirements
-
- All transfer encodings must be fully invertible on any platform; it
- must be possible for anyone to recover the original data by
- performing the corresponding decoding operation. Note that this
- requirement effectively excludes all forms of lossy compression as
- well as all forms of encryption from use as a transfer encoding.
-
-4.1.6. New Functionality Requirements
-
- All transfer encodings must provide some sort of new functionality.
- Some degree of functionality overlap with previously defined transfer
- encodings is acceptable, but any new transfer encoding must also
- offer something no other transfer encoding provides.
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 18]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-4.2. Transfer Encoding Definition Procedure
-
- Definition of a new transfer encoding starts with the construction of
- a draft of a standards-track RFC. The RFC must define the transfer
- encoding precisely and completely, and must also provide substantial
- justification for defining and standardizing a new transfer encoding.
- This specification must then be presented to the IESG for
- consideration. The IESG can
-
- (1) reject the specification outright as being
- inappropriate for standardization,
-
- (2) approve the formation of an IETF working group to work
- on the specification in accordance with IETF
- procedures, or,
-
- (3) accept the specification as-is and put it directly on
- the standards track.
-
- Transfer encoding specifications on the standards track follow normal
- IETF rules for standards track documents. A transfer encoding is
- considered to be defined and available for use once it is on the
- standards track.
-
-4.3. IANA Procedures for Transfer Encoding Registration
-
- There is no need for a special procedure for registering Transfer
- Encodings with the IANA. All legitimate transfer encoding
- registrations must appear as a standards-track RFC, so it is the
- IESG's responsibility to notify the IANA when a new transfer encoding
- has been approved.
-
-4.4. Location of Registered Transfer Encodings List
-
- Transfer encoding registrations will be posted in the anonymous FTP
- directory "ftp://ftp.isi.edu/in-notes/iana/assignments/transfer-
- encodings/" and all registered transfer encodings will be listed in
- the periodically issued "Assigned Numbers" RFC [currently RFC-1700].
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 19]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-5. Authors' Addresses
-
- For more information, the authors of this document are best
- contacted via Internet mail:
-
- Ned Freed
- Innosoft International, Inc.
- 1050 East Garvey Avenue South
- West Covina, CA 91790
- USA
-
- Phone: +1 818 919 3600
- Fax: +1 818 919 3614
- EMail: ned@innosoft.com
-
-
- John Klensin
- MCI
- 2100 Reston Parkway
- Reston, VA 22091
-
- Phone: +1 703 715-7361
- Fax: +1 703 715-7436
- EMail: klensin@mci.net
-
-
- Jon Postel
- USC/Information Sciences Institute
- 4676 Admiralty Way
- Marina del Rey, CA 90292
- USA
-
-
- Phone: +1 310 822 1511
- Fax: +1 310 823 6714
- EMail: Postel@ISI.EDU
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 20]
-
-RFC 2048 MIME Registration Procedures November 1996
-
-
-Appendix A -- Grandfathered Media Types
-
- A number of media types, registered prior to 1996, would, if
- registered under the guidelines in this document, be placed into
- either the vendor or personal trees. Reregistration of those types
- to reflect the appropriate trees is encouraged, but not required.
- Ownership and change control principles outlined in this document
- apply to those types as if they had been registered in the trees
- described above.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed, et. al. Best Current Practice [Page 21]
-
diff --git a/proto/rfc2049.txt b/proto/rfc2049.txt
@@ -1,1347 +0,0 @@
-
-
-
-
-
-
-Network Working Group N. Freed
-Request for Comments: 2049 Innosoft
-Obsoletes: 1521, 1522, 1590 N. Borenstein
-Category: Standards Track First Virtual
- November 1996
-
-
- Multipurpose Internet Mail Extensions
- (MIME) Part Five:
- Conformance Criteria and Examples
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- STD 11, RFC 822, defines a message representation protocol specifying
- considerable detail about US-ASCII message headers, and leaves the
- message content, or message body, as flat US-ASCII text. This set of
- documents, collectively called the Multipurpose Internet Mail
- Extensions, or MIME, redefines the format of messages to allow for
-
- (1) textual message bodies in character sets other than
- US-ASCII,
-
- (2) an extensible set of different formats for non-textual
- message bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than
- US-ASCII.
-
- These documents are based on earlier work documented in RFC 934, STD
- 11, and RFC 1049, but extends and revises them. Because RFC 822 said
- so little about message bodies, these documents are largely
- orthogonal to (rather than a revision of) RFC 822.
-
- The initial document in this set, RFC 2045, specifies the various
- headers used to describe the structure of MIME messages. The second
- document defines the general structure of the MIME media typing
- system and defines an initial set of media types. The third
- document, RFC 2047, describes extensions to RFC 822 to allow non-US-
-
-
-
-Freed & Borenstein Standards Track [Page 1]
-
-RFC 2049 MIME Conformance November 1996
-
-
- ASCII text data in Internet mail header fields. The fourth document,
- RFC 2048, specifies various IANA registration procedures for MIME-
- related facilities. This fifth and final document describes MIME
- conformance criteria as well as providing some illustrative examples
- of MIME message formats, acknowledgements, and the bibliography.
-
- These documents are revisions of RFCs 1521, 1522, and 1590, which
- themselves were revisions of RFCs 1341 and 1342. Appendix B of this
- document describes differences and changes from previous versions.
-
-Table of Contents
-
- 1. Introduction .......................................... 2
- 2. MIME Conformance ...................................... 2
- 3. Guidelines for Sending Email Data ..................... 6
- 4. Canonical Encoding Model .............................. 9
- 5. Summary ............................................... 12
- 6. Security Considerations ............................... 12
- 7. Authors' Addresses .................................... 12
- 8. Acknowledgements ...................................... 13
- A. A Complex Multipart Example ........................... 15
- B. Changes from RFC 1521, 1522, and 1590 ................. 16
- C. References ............................................ 20
-
-1. Introduction
-
- The first and second documents in this set define MIME header fields
- and the initial set of MIME media types. The third document
- describes extensions to RFC822 formats to allow for character sets
- other than US-ASCII. This document describes what portions of MIME
- must be supported by a conformant MIME implementation. It also
- describes various pitfalls of contemporary messaging systems as well
- as the canonical encoding model MIME is based on.
-
-2. MIME Conformance
-
- The mechanisms described in these documents are open-ended. It is
- definitely not expected that all implementations will support all
- available media types, nor that they will all share the same
- extensions. In order to promote interoperability, however, it is
- useful to define the concept of "MIME-conformance" to define a
- certain level of implementation that allows the useful interworking
- of messages with content that differs from US-ASCII text. In this
- section, we specify the requirements for such conformance.
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 2]
-
-RFC 2049 MIME Conformance November 1996
-
-
- A mail user agent that is MIME-conformant MUST:
-
- (1) Always generate a "MIME-Version: 1.0" header field in
- any message it creates.
-
- (2) Recognize the Content-Transfer-Encoding header field
- and decode all received data encoded by either quoted-
- printable or base64 implementations. The identity
- transformations 7bit, 8bit, and binary must also be
- recognized.
-
- Any non-7bit data that is sent without encoding must be
- properly labelled with a content-transfer-encoding of
- 8bit or binary, as appropriate. If the underlying
- transport does not support 8bit or binary (as SMTP
- [RFC-821] does not), the sender is required to both
- encode and label data using an appropriate Content-
- Transfer-Encoding such as quoted-printable or base64.
-
- (3) Must treat any unrecognized Content-Transfer-Encoding
- as if it had a Content-Type of "application/octet-
- stream", regardless of whether or not the actual
- Content-Type is recognized.
-
- (4) Recognize and interpret the Content-Type header field,
- and avoid showing users raw data with a Content-Type
- field other than text. Implementations must be able
- to send at least text/plain messages, with the
- character set specified with the charset parameter if
- it is not US-ASCII.
-
- (5) Ignore any content type parameters whose names they do
- not recognize.
-
- (6) Explicitly handle the following media type values, to
- at least the following extents:
-
- Text:
-
- -- Recognize and display "text" mail with the
- character set "US-ASCII."
-
- -- Recognize other character sets at least to the
- extent of being able to inform the user about what
- character set the message uses.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 3]
-
-RFC 2049 MIME Conformance November 1996
-
-
- -- Recognize the "ISO-8859-*" character sets to the
- extent of being able to display those characters that
- are common to ISO-8859-* and US-ASCII, namely all
- characters represented by octet values 1-127.
-
- -- For unrecognized subtypes in a known character
- set, show or offer to show the user the "raw" version
- of the data after conversion of the content from
- canonical form to local form.
-
- -- Treat material in an unknown character set as if
- it were "application/octet-stream".
-
- Image, audio, and video:
-
- -- At a minumum provide facilities to treat any
- unrecognized subtypes as if they were
- "application/octet-stream".
-
- Application:
-
- -- Offer the ability to remove either of the quoted-
- printable or base64 encodings defined in this
- document if they were used and put the resulting
- information in a user file.
-
- Multipart:
-
- -- Recognize the mixed subtype. Display all relevant
- information on the message level and the body part
- header level and then display or offer to display
- each of the body parts individually.
-
- -- Recognize the "alternative" subtype, and avoid
- showing the user redundant parts of
- multipart/alternative mail.
-
- -- Recognize the "multipart/digest" subtype,
- specifically using "message/rfc822" rather than
- "text/plain" as the default media type for body parts
- inside "multipart/digest" entities.
-
- -- Treat any unrecognized subtypes as if they were
- "mixed".
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 4]
-
-RFC 2049 MIME Conformance November 1996
-
-
- Message:
-
- -- Recognize and display at least the RFC822 message
- encapsulation (message/rfc822) in such a way as to
- preserve any recursive structure, that is, displaying
- or offering to display the encapsulated data in
- accordance with its media type.
-
- -- Treat any unrecognized subtypes as if they were
- "application/octet-stream".
-
- (7) Upon encountering any unrecognized Content-Type field,
- an implementation must treat it as if it had a media
- type of "application/octet-stream" with no parameter
- sub-arguments. How such data are handled is up to an
- implementation, but likely options for handling such
- unrecognized data include offering the user to write it
- into a file (decoded from its mail transport format) or
- offering the user to name a program to which the
- decoded data should be passed as input.
-
- (8) Conformant user agents are required, if they provide
- non-standard support for non-MIME messages employing
- character sets other than US-ASCII, to do so on
- received messages only. Conforming user agents must not
- send non-MIME messages containing anything other than
- US-ASCII text.
-
- In particular, the use of non-US-ASCII text in mail
- messages without a MIME-Version field is strongly
- discouraged as it impedes interoperability when sending
- messages between regions with different localization
- conventions. Conforming user agents MUST include proper
- MIME labelling when sending anything other than plain
- text in the US-ASCII character set.
-
- In addition, non-MIME user agents should be upgraded if
- at all possible to include appropriate MIME header
- information in the messages they send even if nothing
- else in MIME is supported. This upgrade will have
- little, if any, effect on non-MIME recipients and will
- aid MIME in correctly displaying such messages. It
- also provides a smooth transition path to eventual
- adoption of other MIME capabilities.
-
- (9) Conforming user agents must ensure that any string of
- non-white-space printable US-ASCII characters within a
- "*text" or "*ctext" that begins with "=?" and ends with
-
-
-
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-
-
- "?=" be a valid encoded-word. ("begins" means: At the
- start of the field-body or immediately following
- linear-white-space; "ends" means: At the end of the
- field-body or immediately preceding linear-white-
- space.) In addition, any "word" within a "phrase" that
- begins with "=?" and ends with "?=" must be a valid
- encoded-word.
-
- (10) Conforming user agents must be able to distinguish
- encoded-words from "text", "ctext", or "word"s,
- according to the rules in section 4, anytime they
- appear in appropriate places in message headers. It
- must support both the "B" and "Q" encodings for any
- character set which it supports. The program must be
- able to display the unencoded text if the character set
- is "US-ASCII". For the ISO-8859-* character sets, the
- mail reading program must at least be able to display
- the characters which are also in the US-ASCII set.
-
- A user agent that meets the above conditions is said to be MIME-
- conformant. The meaning of this phrase is that it is assumed to be
- "safe" to send virtually any kind of properly-marked data to users of
- such mail systems, because such systems will at least be able to
- treat the data as undifferentiated binary, and will not simply splash
- it onto the screen of unsuspecting users.
-
- There is another sense in which it is always "safe" to send data in a
- format that is MIME-conformant, which is that such data will not
- break or be broken by any known systems that are conformant with RFC
- 821 and RFC 822. User agents that are MIME-conformant have the
- additional guarantee that the user will not be shown data that were
- never intended to be viewed as text.
-
-3. Guidelines for Sending Email Data
-
- Internet email is not a perfect, homogeneous system. Mail may become
- corrupted at several stages in its travel to a final destination.
- Specifically, email sent throughout the Internet may travel across
- many networking technologies. Many networking and mail technologies
- do not support the full functionality possible in the SMTP transport
- environment. Mail traversing these systems is likely to be modified
- in order that it can be transported.
-
- There exist many widely-deployed non-conformant MTAs in the Internet.
- These MTAs, speaking the SMTP protocol, alter messages on the fly to
- take advantage of the internal data structure of the hosts they are
- implemented on, or are just plain broken.
-
-
-
-
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-
-
- The following guidelines may be useful to anyone devising a data
- format (media type) that is supposed to survive the widest range of
- networking technologies and known broken MTAs unscathed. Note that
- anything encoded in the base64 encoding will satisfy these rules, but
- that some well-known mechanisms, notably the UNIX uuencode facility,
- will not. Note also that anything encoded in the Quoted-Printable
- encoding will survive most gateways intact, but possibly not some
- gateways to systems that use the EBCDIC character set.
-
- (1) Under some circumstances the encoding used for data may
- change as part of normal gateway or user agent
- operation. In particular, conversion from base64 to
- quoted-printable and vice versa may be necessary. This
- may result in the confusion of CRLF sequences with line
- breaks in text bodies. As such, the persistence of
- CRLF as something other than a line break must not be
- relied on.
-
- (2) Many systems may elect to represent and store text data
- using local newline conventions. Local newline
- conventions may not match the RFC822 CRLF convention --
- systems are known that use plain CR, plain LF, CRLF, or
- counted records. The result is that isolated CR and LF
- characters are not well tolerated in general; they may
- be lost or converted to delimiters on some systems, and
- hence must not be relied on.
-
- (3) The transmission of NULs (US-ASCII value 0) is
- problematic in Internet mail. (This is largely the
- result of NULs being used as a termination character by
- many of the standard runtime library routines in the C
- programming language.) The practice of using NULs as
- termination characters is so entrenched now that
- messages should not rely on them being preserved.
-
- (4) TAB (HT) characters may be misinterpreted or may be
- automatically converted to variable numbers of spaces.
- This is unavoidable in some environments, notably those
- not based on the US-ASCII character set. Such
- conversion is STRONGLY DISCOURAGED, but it may occur,
- and mail formats must not rely on the persistence of
- TAB (HT) characters.
-
- (5) Lines longer than 76 characters may be wrapped or
- truncated in some environments. Line wrapping or line
- truncation imposed by mail transports is STRONGLY
- DISCOURAGED, but unavoidable in some cases.
- Applications which require long lines must somehow
-
-
-
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-
-
- differentiate between soft and hard line breaks. (A
- simple way to do this is to use the quoted-printable
- encoding.)
-
- (6) Trailing "white space" characters (SPACE, TAB (HT)) on
- a line may be discarded by some transport agents, while
- other transport agents may pad lines with these
- characters so that all lines in a mail file are of
- equal length. The persistence of trailing white space,
- therefore, must not be relied on.
-
- (7) Many mail domains use variations on the US-ASCII
- character set, or use character sets such as EBCDIC
- which contain most but not all of the US-ASCII
- characters. The correct translation of characters not
- in the "invariant" set cannot be depended on across
- character converting gateways. For example, this
- situation is a problem when sending uuencoded
- information across BITNET, an EBCDIC system. Similar
- problems can occur without crossing a gateway, since
- many Internet hosts use character sets other than US-
- ASCII internally. The definition of Printable Strings
- in X.400 adds further restrictions in certain special
- cases. In particular, the only characters that are
- known to be consistent across all gateways are the 73
- characters that correspond to the upper and lower case
- letters A-Z and a-z, the 10 digits 0-9, and the
- following eleven special characters:
-
- "'" (US-ASCII decimal value 39)
- "(" (US-ASCII decimal value 40)
- ")" (US-ASCII decimal value 41)
- "+" (US-ASCII decimal value 43)
- "," (US-ASCII decimal value 44)
- "-" (US-ASCII decimal value 45)
- "." (US-ASCII decimal value 46)
- "/" (US-ASCII decimal value 47)
- ":" (US-ASCII decimal value 58)
- "=" (US-ASCII decimal value 61)
- "?" (US-ASCII decimal value 63)
-
- A maximally portable mail representation will confine
- itself to relatively short lines of text in which the
- only meaningful characters are taken from this set of
- 73 characters. The base64 encoding follows this rule.
-
- (8) Some mail transport agents will corrupt data that
- includes certain literal strings. In particular, a
-
-
-
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-
-
- period (".") alone on a line is known to be corrupted
- by some (incorrect) SMTP implementations, and a line
- that starts with the five characters "From " (the fifth
- character is a SPACE) are commonly corrupted as well.
- A careful composition agent can prevent these
- corruptions by encoding the data (e.g., in the quoted-
- printable encoding using "=46rom " in place of "From "
- at the start of a line, and "=2E" in place of "." alone
- on a line).
-
- Please note that the above list is NOT a list of recommended
- practices for MTAs. RFC 821 MTAs are prohibited from altering the
- character of white space or wrapping long lines. These BAD and
- invalid practices are known to occur on established networks, and
- implementations should be robust in dealing with the bad effects they
- can cause.
-
-4. Canonical Encoding Model
-
- There was some confusion, in earlier versions of these documents,
- regarding the model for when email data was to be converted to
- canonical form and encoded, and in particular how this process would
- affect the treatment of CRLFs, given that the representation of
- newlines varies greatly from system to system. For this reason, a
- canonical model for encoding is presented below.
-
- The process of composing a MIME entity can be modeled as being done
- in a number of steps. Note that these steps are roughly similar to
- those steps used in PEM [RFC-1421] and are performed for each
- "innermost level" body:
-
- (1) Creation of local form.
-
- The body to be transmitted is created in the system's
- native format. The native character set is used and,
- where appropriate, local end of line conventions are
- used as well. The body may be a UNIX-style text file,
- or a Sun raster image, or a VMS indexed file, or audio
- data in a system-dependent format stored only in
- memory, or anything else that corresponds to the local
- model for the representation of some form of
- information. Fundamentally, the data is created in the
- "native" form that corresponds to the type specified by
- the media type.
-
-
-
-
-
-
-
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-
-
- (2) Conversion to canonical form.
-
- The entire body, including "out-of-band" information
- such as record lengths and possibly file attribute
- information, is converted to a universal canonical
- form. The specific media type of the body as well as
- its associated attributes dictate the nature of the
- canonical form that is used. Conversion to the proper
- canonical form may involve character set conversion,
- transformation of audio data, compression, or various
- other operations specific to the various media types.
- If character set conversion is involved, however, care
- must be taken to understand the semantics of the media
- type, which may have strong implications for any
- character set conversion, e.g. with regard to
- syntactically meaningful characters in a text subtype
- other than "plain".
-
- For example, in the case of text/plain data, the text
- must be converted to a supported character set and
- lines must be delimited with CRLF delimiters in
- accordance with RFC 822. Note that the restriction on
- line lengths implied by RFC 822 is eliminated if the
- next step employs either quoted-printable or base64
- encoding.
-
- (3) Apply transfer encoding.
-
- A Content-Transfer-Encoding appropriate for this body
- is applied. Note that there is no fixed relationship
- between the media type and the transfer encoding. In
- particular, it may be appropriate to base the choice of
- base64 or quoted-printable on character frequency
- counts which are specific to a given instance of a
- body.
-
- (4) Insertion into entity.
-
- The encoded body is inserted into a MIME entity with
- appropriate headers. The entity is then inserted into
- the body of a higher-level entity (message or
- multipart) as needed.
-
- Conversion from entity form to local form is accomplished by
- reversing these steps. Note that reversal of these steps may produce
- differing results since there is no guarantee that the original and
- final local forms are the same.
-
-
-
-
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-RFC 2049 MIME Conformance November 1996
-
-
- It is vital to note that these steps are only a model; they are
- specifically NOT a blueprint for how an actual system would be built.
- In particular, the model fails to account for two common designs:
-
- (1) In many cases the conversion to a canonical form prior
- to encoding will be subsumed into the encoder itself,
- which understands local formats directly. For example,
- the local newline convention for text bodies might be
- carried through to the encoder itself along with
- knowledge of what that format is.
-
- (2) The output of the encoders may have to pass through one
- or more additional steps prior to being transmitted as
- a message. As such, the output of the encoder may not
- be conformant with the formats specified by RFC 822.
- In particular, once again it may be appropriate for the
- converter's output to be expressed using local newline
- conventions rather than using the standard RFC 822 CRLF
- delimiters.
-
- Other implementation variations are conceivable as well. The vital
- aspect of this discussion is that, in spite of any optimizations,
- collapsings of required steps, or insertion of additional processing,
- the resulting messages must be consistent with those produced by the
- model described here. For example, a message with the following
- header fields:
-
- Content-type: text/foo; charset=bar
- Content-Transfer-Encoding: base64
-
- must be first represented in the text/foo form, then (if necessary)
- represented in the "bar" character set, and finally transformed via
- the base64 algorithm into a mail-safe form.
-
- NOTE: Some confusion has been caused by systems that represent
- messages in a format which uses local newline conventions which
- differ from the RFC822 CRLF convention. It is important to note that
- these formats are not canonical RFC822/MIME. These formats are
- instead *encodings* of RFC822, where CRLF sequences in the canonical
- representation of the message are encoded as the local newline
- convention. Note that formats which encode CRLF sequences as, for
- example, LF are not capable of representing MIME messages containing
- binary data which contains LF octets not part of CRLF line separation
- sequences.
-
-
-
-
-
-
-
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-
-RFC 2049 MIME Conformance November 1996
-
-
-5. Summary
-
- This document defines what is meant by MIME Conformance. It also
- details various problems known to exist in the Internet email system
- and how to use MIME to overcome them. Finally, it describes MIME's
- canonical encoding model.
-
-6. Security Considerations
-
- Security issues are discussed in the second document in this set, RFC
- 2046.
-
-7. Authors' Addresses
-
- For more information, the authors of this document are best contacted
- via Internet mail:
-
- Ned Freed
- Innosoft International, Inc.
- 1050 East Garvey Avenue South
- West Covina, CA 91790
- USA
-
- Phone: +1 818 919 3600
- Fax: +1 818 919 3614
- EMail: ned@innosoft.com
-
- Nathaniel S. Borenstein
- First Virtual Holdings
- 25 Washington Avenue
- Morristown, NJ 07960
- USA
-
- Phone: +1 201 540 8967
- Fax: +1 201 993 3032
- EMail: nsb@nsb.fv.com
-
- MIME is a result of the work of the Internet Engineering Task Force
- Working Group on RFC 822 Extensions. The chairman of that group,
- Greg Vaudreuil, may be reached at:
-
- Gregory M. Vaudreuil
- Octel Network Services
- 17080 Dallas Parkway
- Dallas, TX 75248-1905
- USA
-
- EMail: Greg.Vaudreuil@Octel.Com
-
-
-
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-
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-
-
-8. Acknowledgements
-
- This document is the result of the collective effort of a large
- number of people, at several IETF meetings, on the IETF-SMTP and
- IETF-822 mailing lists, and elsewhere. Although any enumeration
- seems doomed to suffer from egregious omissions, the following are
- among the many contributors to this effort:
-
- Harald Tveit Alvestrand Marc Andreessen
- Randall Atkinson Bob Braden
- Philippe Brandon Brian Capouch
- Kevin Carosso Uhhyung Choi
- Peter Clitherow Dave Collier-Brown
- Cristian Constantinof John Coonrod
- Mark Crispin Dave Crocker
- Stephen Crocker Terry Crowley
- Walt Daniels Jim Davis
- Frank Dawson Axel Deininger
- Hitoshi Doi Kevin Donnelly
- Steve Dorner Keith Edwards
- Chris Eich Dana S. Emery
- Johnny Eriksson Craig Everhart
- Patrik Faltstrom Erik E. Fair
- Roger Fajman Alain Fontaine
- Martin Forssen James M. Galvin
- Stephen Gildea Philip Gladstone
- Thomas Gordon Keld Simonsen
- Terry Gray Phill Gross
- James Hamilton David Herron
- Mark Horton Bruce Howard
- Bill Janssen Olle Jarnefors
- Risto Kankkunen Phil Karn
- Alan Katz Tim Kehres
- Neil Katin Steve Kille
- Kyuho Kim Anders Klemets
- John Klensin Valdis Kletniek
- Jim Knowles Stev Knowles
- Bob Kummerfeld Pekka Kytolaakso
- Stellan Lagerstrom Vincent Lau
- Timo Lehtinen Donald Lindsay
- Warner Losh Carlyn Lowery
- Laurence Lundblade Charles Lynn
- John R. MacMillan Larry Masinter
- Rick McGowan Michael J. McInerny
- Leo Mclaughlin Goli Montaser-Kohsari
- Tom Moore John Gardiner Myers
- Erik Naggum Mark Needleman
- Chris Newman John Noerenberg
-
-
-
-Freed & Borenstein Standards Track [Page 13]
-
-RFC 2049 MIME Conformance November 1996
-
-
- Mats Ohrman Julian Onions
- Michael Patton David J. Pepper
- Erik van der Poel Blake C. Ramsdell
- Christer Romson Luc Rooijakkers
- Marshall T. Rose Jonathan Rosenberg
- Guido van Rossum Jan Rynning
- Harri Salminen Michael Sanderson
- Yutaka Sato Markku Savela
- Richard Alan Schafer Masahiro Sekiguchi
- Mark Sherman Bob Smart
- Peter Speck Henry Spencer
- Einar Stefferud Michael Stein
- Klaus Steinberger Peter Svanberg
- James Thompson Steve Uhler
- Stuart Vance Peter Vanderbilt
- Greg Vaudreuil Ed Vielmetti
- Larry W. Virden Ryan Waldron
- Rhys Weatherly Jay Weber
- Dave Wecker Wally Wedel
- Sven-Ove Westberg Brian Wideen
- John Wobus Glenn Wright
- Rayan Zachariassen David Zimmerman
-
- The authors apologize for any omissions from this list, which are
- certainly unintentional.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 14]
-
-RFC 2049 MIME Conformance November 1996
-
-
-Appendix A -- A Complex Multipart Example
-
- What follows is the outline of a complex multipart message. This
- message contains five parts that are to be displayed serially: two
- introductory plain text objects, an embedded multipart message, a
- text/enriched object, and a closing encapsulated text message in a
- non-ASCII character set. The embedded multipart message itself
- contains two objects to be displayed in parallel, a picture and an
- audio fragment.
-
- MIME-Version: 1.0
- From: Nathaniel Borenstein <nsb@nsb.fv.com>
- To: Ned Freed <ned@innosoft.com>
- Date: Fri, 07 Oct 1994 16:15:05 -0700 (PDT)
- Subject: A multipart example
- Content-Type: multipart/mixed;
- boundary=unique-boundary-1
-
- This is the preamble area of a multipart message.
- Mail readers that understand multipart format
- should ignore this preamble.
-
- If you are reading this text, you might want to
- consider changing to a mail reader that understands
- how to properly display multipart messages.
-
- --unique-boundary-1
-
- ... Some text appears here ...
-
- [Note that the blank between the boundary and the start
- of the text in this part means no header fields were
- given and this is text in the US-ASCII character set.
- It could have been done with explicit typing as in the
- next part.]
-
- --unique-boundary-1
- Content-type: text/plain; charset=US-ASCII
-
- This could have been part of the previous part, but
- illustrates explicit versus implicit typing of body
- parts.
-
- --unique-boundary-1
- Content-Type: multipart/parallel; boundary=unique-boundary-2
-
- --unique-boundary-2
- Content-Type: audio/basic
-
-
-
-Freed & Borenstein Standards Track [Page 15]
-
-RFC 2049 MIME Conformance November 1996
-
-
- Content-Transfer-Encoding: base64
-
- ... base64-encoded 8000 Hz single-channel
- mu-law-format audio data goes here ...
-
- --unique-boundary-2
- Content-Type: image/jpeg
- Content-Transfer-Encoding: base64
-
- ... base64-encoded image data goes here ...
-
- --unique-boundary-2--
-
- --unique-boundary-1
- Content-type: text/enriched
-
- This is <bold><italic>enriched.</italic></bold>
- <smaller>as defined in RFC 1896</smaller>
-
- Isn't it
- <bigger><bigger>cool?</bigger></bigger>
-
- --unique-boundary-1
- Content-Type: message/rfc822
-
- From: (mailbox in US-ASCII)
- To: (address in US-ASCII)
- Subject: (subject in US-ASCII)
- Content-Type: Text/plain; charset=ISO-8859-1
- Content-Transfer-Encoding: Quoted-printable
-
- ... Additional text in ISO-8859-1 goes here ...
-
- --unique-boundary-1--
-
-Appendix B -- Changes from RFC 1521, 1522, and 1590
-
- These documents are a revision of RFC 1521, 1522, and 1590. For the
- convenience of those familiar with the earlier documents, the changes
- from those documents are summarized in this appendix. For further
- history, note that Appendix H in RFC 1521 specified how that document
- differed from its predecessor, RFC 1341.
-
- (1) This document has been completely reformatted and split
- into multiple documents. This was done to improve the
- quality of the plain text version of this document,
- which is required to be the reference copy.
-
-
-
-
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-
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-
-
- (2) BNF describing the overall structure of MIME object
- headers has been added. This is a documentation change
- only -- the underlying syntax has not changed in any
- way.
-
- (3) The specific BNF for the seven media types in MIME has
- been removed. This BNF was incorrect, incomplete, amd
- inconsistent with the type-indendependent BNF. And
- since the type-independent BNF already fully specifies
- the syntax of the various MIME headers, the type-
- specific BNF was, in the final analysis, completely
- unnecessary and caused more problems than it solved.
-
- (4) The more specific "US-ASCII" character set name has
- replaced the use of the informal term ASCII in many
- parts of these documents.
-
- (5) The informal concept of a primary subtype has been
- removed.
-
- (6) The term "object" was being used inconsistently. The
- definition of this term has been clarified, along with
- the related terms "body", "body part", and "entity",
- and usage has been corrected where appropriate.
-
- (7) The BNF for the multipart media type has been
- rearranged to make it clear that the CRLF preceeding
- the boundary marker is actually part of the marker
- itself rather than the preceeding body part.
-
- (8) The prose and BNF describing the multipart media type
- have been changed to make it clear that the body parts
- within a multipart object MUST NOT contain any lines
- beginning with the boundary parameter string.
-
- (9) In the rules on reassembling "message/partial" MIME
- entities, "Subject" is added to the list of headers to
- take from the inner message, and the example is
- modified to clarify this point.
-
- (10) "Message/partial" fragmenters are restricted to
- splitting MIME objects only at line boundaries.
-
- (11) In the discussion of the application/postscript type,
- an additional paragraph has been added warning about
- possible interoperability problems caused by embedding
- of binary data inside a PostScript MIME entity.
-
-
-
-
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-
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-
-
- (12) Added a clarifying note to the basic syntax rules for
- the Content-Type header field to make it clear that the
- following two forms:
-
- Content-type: text/plain; charset=us-ascii (comment)
-
- Content-type: text/plain; charset="us-ascii"
-
- are completely equivalent.
-
- (13) The following sentence has been removed from the
- discussion of the MIME-Version header: "However,
- conformant software is encouraged to check the version
- number and at least warn the user if an unrecognized
- MIME-version is encountered."
-
- (14) A typo was fixed that said "application/external-body"
- instead of "message/external-body".
-
- (15) The definition of a character set has been reorganized
- to make the requirements clearer.
-
- (16) The definition of the "image/gif" media type has been
- moved to a separate document. This change was made
- because of potential conflicts with IETF rules
- governing the standardization of patented technology.
-
- (17) The definitions of "7bit" and "8bit" have been
- tightened so that use of bare CR, LF can only be used
- as end-of-line sequences. The document also no longer
- requires that NUL characters be preserved, which brings
- MIME into alignment with real-world implementations.
-
- (18) The definition of canonical text in MIME has been
- tightened so that line breaks must be represented by a
- CRLF sequence. CR and LF characters are not allowed
- outside of this usage. The definition of quoted-
- printable encoding has been altered accordingly.
-
- (19) The definition of the quoted-printable encoding now
- includes a number of suggestions for how quoted-
- printable encoders might best handle improperly encoded
- material.
-
- (20) Prose was added to clarify the use of the "7bit",
- "8bit", and "binary" transfer-encodings on multipart or
- message entities encapsulating "8bit" or "binary" data.
-
-
-
-
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-
-RFC 2049 MIME Conformance November 1996
-
-
- (21) In the section on MIME Conformance, "multipart/digest"
- support was added to the list of requirements for
- minimal MIME conformance. Also, the requirement for
- "message/rfc822" support were strengthened to clarify
- the importance of recognizing recursive structure.
-
- (22) The various restrictions on subtypes of "message" are
- now specified entirely on a subtype by subtype basis.
-
- (23) The definition of "message/rfc822" was changed to
- indicate that at least one of the "From", "Subject", or
- "Date" headers must be present.
-
- (24) The required handling of unrecognized subtypes as
- "application/octet-stream" has been made more explicit
- in both the type definitions sections and the
- conformance guidelines.
-
- (25) Examples using text/richtext were changed to
- text/enriched.
-
- (26) The BNF definition of subtype has been changed to make
- it clear that either an IANA registered subtype or a
- nonstandard "X-" subtype must be used in a Content-Type
- header field.
-
- (27) MIME media types that are simply registered for use and
- those that are standardized by the IETF are now
- distinguished in the MIME BNF.
-
- (28) All of the various MIME registration procedures have
- been extensively revised. IANA registration procedures
- for character sets have been moved to a separate
- document that is no included in this set of documents.
-
- (29) The use of escape and shift mechanisms in the US-ASCII
- and ISO-8859-X character sets these documents define
- have been clarified: Such mechanisms should never be
- used in conjunction with these character sets and their
- effect if they are used is undefined.
-
- (30) The definition of the AFS access-type for
- message/external-body has been removed.
-
- (31) The handling of the combination of
- multipart/alternative and message/external-body is now
- specifically addressed.
-
-
-
-
-Freed & Borenstein Standards Track [Page 19]
-
-RFC 2049 MIME Conformance November 1996
-
-
- (32) Security issues specific to message/external-body are
- now discussed in some detail.
-
-Appendix C -- References
-
- [ATK]
- Borenstein, Nathaniel S., Multimedia Applications
- Development with the Andrew Toolkit, Prentice-Hall, 1990.
-
- [ISO-2022]
- International Standard -- Information Processing --
- Character Code Structure and Extension Techniques,
- ISO/IEC 2022:1994, 4th ed.
-
- [ISO-8859]
- International Standard -- Information Processing -- 8-bit
- Single-Byte Coded Graphic Character Sets
- - Part 1: Latin Alphabet No. 1, ISO 8859-1:1987, 1st ed.
- - Part 2: Latin Alphabet No. 2, ISO 8859-2:1987, 1st ed.
- - Part 3: Latin Alphabet No. 3, ISO 8859-3:1988, 1st ed.
- - Part 4: Latin Alphabet No. 4, ISO 8859-4:1988, 1st ed.
- - Part 5: Latin/Cyrillic Alphabet, ISO 8859-5:1988, 1st
- ed.
- - Part 6: Latin/Arabic Alphabet, ISO 8859-6:1987, 1st ed.
- - Part 7: Latin/Greek Alphabet, ISO 8859-7:1987, 1st ed.
- - Part 8: Latin/Hebrew Alphabet, ISO 8859-8:1988, 1st ed.
- - Part 9: Latin Alphabet No. 5, ISO/IEC 8859-9:1989, 1st
- ed.
- International Standard -- Information Technology -- 8-bit
- Single-Byte Coded Graphic Character Sets
- - Part 10: Latin Alphabet No. 6, ISO/IEC 8859-10:1992,
- 1st ed.
-
- [ISO-646]
- International Standard -- Information Technology -- ISO
- 7-bit Coded Character Set for Information Interchange,
- ISO 646:1991, 3rd ed..
-
- [JPEG]
- JPEG Draft Standard ISO 10918-1 CD.
-
- [MPEG]
- Video Coding Draft Standard ISO 11172 CD, ISO
- IEC/JTC1/SC2/WG11 (Motion Picture Experts Group), May,
- 1991.
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 20]
-
-RFC 2049 MIME Conformance November 1996
-
-
- [PCM]
- CCITT, Fascicle III.4 - Recommendation G.711, "Pulse Code
- Modulation (PCM) of Voice Frequencies", Geneva, 1972.
-
- [POSTSCRIPT]
- Adobe Systems, Inc., PostScript Language Reference
- Manual, Addison-Wesley, 1985.
-
- [POSTSCRIPT2]
- Adobe Systems, Inc., PostScript Language Reference
- Manual, Addison-Wesley, Second Ed., 1990.
-
- [RFC-783]
- Sollins, K.R., "TFTP Protocol (revision 2)", RFC-783,
- MIT, June 1981.
-
- [RFC-821]
- Postel, J.B., "Simple Mail Transfer Protocol", STD 10,
- RFC 821, USC/Information Sciences Institute, August 1982.
-
- [RFC-822]
- Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", STD 11, RFC 822, UDEL, August 1982.
-
- [RFC-934]
- Rose, M. and E. Stefferud, "Proposed Standard for Message
- Encapsulation", RFC 934, Delaware and NMA, January 1985.
-
- [RFC-959]
- Postel, J. and J. Reynolds, "File Transfer Protocol", STD
- 9, RFC 959, USC/Information Sciences Institute, October
- 1985.
-
- [RFC-1049]
- Sirbu, M., "Content-Type Header Field for Internet
- Messages", RFC 1049, CMU, March 1988.
-
- [RFC-1154]
- Robinson, D., and R. Ullmann, "Encoding Header Field for
- Internet Messages", RFC 1154, Prime Computer, Inc., April
- 1990.
-
- [RFC-1341]
- Borenstein, N., and N. Freed, "MIME (Multipurpose
- Internet Mail Extensions): Mechanisms for Specifying and
- Describing the Format of Internet Message Bodies", RFC
- 1341, Bellcore, Innosoft, June 1992.
-
-
-
-
-Freed & Borenstein Standards Track [Page 21]
-
-RFC 2049 MIME Conformance November 1996
-
-
- [RFC-1342]
- Moore, K., "Representation of Non-Ascii Text in Internet
- Message Headers", RFC 1342, University of Tennessee, June
- 1992.
-
- [RFC-1344]
- Borenstein, N., "Implications of MIME for Internet Mail
- Gateways", RFC 1344, Bellcore, June 1992.
-
- [RFC-1345]
- Simonsen, K., "Character Mnemonics & Character Sets", RFC
- 1345, Rationel Almen Planlaegning, June 1992.
-
- [RFC-1421]
- Linn, J., "Privacy Enhancement for Internet Electronic
- Mail: Part I -- Message Encryption and Authentication
- Procedures", RFC 1421, IAB IRTF PSRG, IETF PEM WG,
- February 1993.
-
- [RFC-1422]
- Kent, S., "Privacy Enhancement for Internet Electronic
- Mail: Part II -- Certificate-Based Key Management", RFC
- 1422, IAB IRTF PSRG, IETF PEM WG, February 1993.
-
- [RFC-1423]
- Balenson, D., "Privacy Enhancement for Internet
- Electronic Mail: Part III -- Algorithms, Modes, and
- Identifiers", IAB IRTF PSRG, IETF PEM WG, February 1993.
-
- [RFC-1424]
- Kaliski, B., "Privacy Enhancement for Internet Electronic
- Mail: Part IV -- Key Certification and Related
- Services", IAB IRTF PSRG, IETF PEM WG, February 1993.
-
- [RFC-1521]
- Borenstein, N., and Freed, N., "MIME (Multipurpose
- Internet Mail Extensions): Mechanisms for Specifying and
- Describing the Format of Internet Message Bodies", RFC
- 1521, Bellcore, Innosoft, September, 1993.
-
- [RFC-1522]
- Moore, K., "Representation of Non-ASCII Text in Internet
- Message Headers", RFC 1522, University of Tennessee,
- September 1993.
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 22]
-
-RFC 2049 MIME Conformance November 1996
-
-
- [RFC-1524]
- Borenstein, N., "A User Agent Configuration Mechanism for
- Multimedia Mail Format Information", RFC 1524, Bellcore,
- September 1993.
-
- [RFC-1543]
- Postel, J., "Instructions to RFC Authors", RFC 1543,
- USC/Information Sciences Institute, October 1993.
-
- [RFC-1556]
- Nussbacher, H., "Handling of Bi-directional Texts in
- MIME", RFC 1556, Israeli Inter-University Computer
- Center, December 1993.
-
- [RFC-1590]
- Postel, J., "Media Type Registration Procedure", RFC
- 1590, USC/Information Sciences Institute, March 1994.
-
- [RFC-1602]
- Internet Architecture Board, Internet Engineering
- Steering Group, Huitema, C., Gross, P., "The Internet
- Standards Process -- Revision 2", March 1994.
-
- [RFC-1652]
- Klensin, J., (WG Chair), Freed, N., (Editor), Rose, M.,
- Stefferud, E., and Crocker, D., "SMTP Service Extension
- for 8bit-MIME transport", RFC 1652, United Nations
- University, Innosoft, Dover Beach Consulting, Inc.,
- Network Management Associates, Inc., The Branch Office,
- March 1994.
-
- [RFC-1700]
- Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,
- RFC 1700, USC/Information Sciences Institute, October
- 1994.
-
- [RFC-1741]
- Faltstrom, P., Crocker, D., and Fair, E., "MIME Content
- Type for BinHex Encoded Files", December 1994.
-
- [RFC-1896]
- Resnick, P., and A. Walker, "The text/enriched MIME
- Content-type", RFC 1896, February, 1996.
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 23]
-
-RFC 2049 MIME Conformance November 1996
-
-
- [RFC-2045]
- Freed, N., and and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part One: Format of Internet Message
- Bodies", RFC 2045, Innosoft, First Virtual Holdings,
- November 1996.
-
- [RFC-2046]
- Freed, N., and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Two: Media Types", RFC 2046,
- Innosoft, First Virtual Holdings, November 1996.
-
- [RFC-2047]
- Moore, K., "Multipurpose Internet Mail Extensions (MIME)
- Part Three: Representation of Non-ASCII Text in Internet
- Message Headers", RFC 2047, University of
- Tennessee, November 1996.
-
- [RFC-2048]
- Freed, N., Klensin, J., and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) Part Four: MIME
- Registration Procedures", RFC 2048, Innosoft, MCI,
- ISI, November 1996.
-
- [RFC-2049]
- Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Five: Conformance Criteria and
- Examples", RFC 2049 (this document), Innosoft, First
- Virtual Holdings, November 1996.
-
- [US-ASCII]
- Coded Character Set -- 7-Bit American Standard Code for
- Information Interchange, ANSI X3.4-1986.
-
- [X400]
- Schicker, Pietro, "Message Handling Systems, X.400",
- Message Handling Systems and Distributed Applications, E.
- Stefferud, O-j. Jacobsen, and P. Schicker, eds., North-
- Holland, 1989, pp. 3-41.
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Borenstein Standards Track [Page 24]
-
diff --git a/proto/rfc2183.txt b/proto/rfc2183.txt
@@ -1,675 +0,0 @@
-
-
-
-
-
-
-Network Working Group R. Troost
-Request for Comments: 2183 New Century Systems
-Updates: 1806 S. Dorner
-Category: Standards Track QUALCOMM Incorporated
- K. Moore, Editor
- University of Tennessee
- August 1997
-
-
- Communicating Presentation Information in
- Internet Messages:
- The Content-Disposition Header Field
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- This memo provides a mechanism whereby messages conforming to the
- MIME specifications [RFC 2045, RFC 2046, RFC 2047, RFC 2048, RFC
- 2049] can convey presentational information. It specifies the
- "Content-Disposition" header field, which is optional and valid for
- any MIME entity ("message" or "body part"). Two values for this
- header field are described in this memo; one for the ordinary linear
- presentation of the body part, and another to facilitate the use of
- mail to transfer files. It is expected that more values will be
- defined in the future, and procedures are defined for extending this
- set of values.
-
- This document is intended as an extension to MIME. As such, the
- reader is assumed to be familiar with the MIME specifications, and
- [RFC 822]. The information presented herein supplements but does not
- replace that found in those documents.
-
- This document is a revision to the Experimental protocol defined in
- RFC 1806. As compared to RFC 1806, this document contains minor
- editorial updates, adds new parameters needed to support the File
- Transfer Body Part, and references a separate specification for the
- handling of non-ASCII and/or very long parameter values.
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 1]
-
-RFC 2183 Content-Disposition August 1997
-
-
-1. Introduction
-
- MIME specifies a standard format for encapsulating multiple pieces of
- data into a single Internet message. That document does not address
- the issue of presentation styles; it provides a framework for the
- interchange of message content, but leaves presentation issues solely
- in the hands of mail user agent (MUA) implementors.
-
- Two common ways of presenting multipart electronic messages are as a
- main document with a list of separate attachments, and as a single
- document with the various parts expanded (displayed) inline. The
- display of an attachment is generally construed to require positive
- action on the part of the recipient, while inline message components
- are displayed automatically when the message is viewed. A mechanism
- is needed to allow the sender to transmit this sort of presentational
- information to the recipient; the Content-Disposition header provides
- this mechanism, allowing each component of a message to be tagged
- with an indication of its desired presentation semantics.
-
- Tagging messages in this manner will often be sufficient for basic
- message formatting. However, in many cases a more powerful and
- flexible approach will be necessary. The definition of such
- approaches is beyond the scope of this memo; however, such approaches
- can benefit from additional Content-Disposition values and
- parameters, to be defined at a later date.
-
- In addition to allowing the sender to specify the presentational
- disposition of a message component, it is desirable to allow her to
- indicate a default archival disposition; a filename. The optional
- "filename" parameter provides for this. Further, the creation-date,
- modification-date, and read-date parameters allow preservation of
- those file attributes when the file is transmitted over MIME email.
-
- NB: The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
- SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
- document, are to be interpreted as described in [RFC 2119].
-
-2. The Content-Disposition Header Field
-
- Content-Disposition is an optional header field. In its absence, the
- MUA may use whatever presentation method it deems suitable.
-
- It is desirable to keep the set of possible disposition types small
- and well defined, to avoid needless complexity. Even so, evolving
- usage will likely require the definition of additional disposition
- types or parameters, so the set of disposition values is extensible;
- see below.
-
-
-
-
-Troost, et. al. Standards Track [Page 2]
-
-RFC 2183 Content-Disposition August 1997
-
-
- In the extended BNF notation of [RFC 822], the Content-Disposition
- header field is defined as follows:
-
- disposition := "Content-Disposition" ":"
- disposition-type
- *(";" disposition-parm)
-
- disposition-type := "inline"
- / "attachment"
- / extension-token
- ; values are not case-sensitive
-
- disposition-parm := filename-parm
- / creation-date-parm
- / modification-date-parm
- / read-date-parm
- / size-parm
- / parameter
-
- filename-parm := "filename" "=" value
-
- creation-date-parm := "creation-date" "=" quoted-date-time
-
- modification-date-parm := "modification-date" "=" quoted-date-time
-
- read-date-parm := "read-date" "=" quoted-date-time
-
- size-parm := "size" "=" 1*DIGIT
-
- quoted-date-time := quoted-string
- ; contents MUST be an RFC 822 `date-time'
- ; numeric timezones (+HHMM or -HHMM) MUST be used
-
-
-
- NOTE ON PARAMETER VALUE LENGHTS: A short (length <= 78 characters)
- parameter value containing only non-`tspecials' characters SHOULD be
- represented as a single `token'. A short parameter value containing
- only ASCII characters, but including `tspecials' characters, SHOULD
- be represented as `quoted-string'. Parameter values longer than 78
- characters, or which contain non-ASCII characters, MUST be encoded as
- specified in [RFC 2184].
-
- `Extension-token', `parameter', `tspecials' and `value' are defined
- according to [RFC 2045] (which references [RFC 822] in the definition
- of some of these tokens). `quoted-string' and `DIGIT' are defined in
- [RFC 822].
-
-
-
-
-Troost, et. al. Standards Track [Page 3]
-
-RFC 2183 Content-Disposition August 1997
-
-
-2.1 The Inline Disposition Type
-
- A bodypart should be marked `inline' if it is intended to be
- displayed automatically upon display of the message. Inline
- bodyparts should be presented in the order in which they occur,
- subject to the normal semantics of multipart messages.
-
-2.2 The Attachment Disposition Type
-
- Bodyparts can be designated `attachment' to indicate that they are
- separate from the main body of the mail message, and that their
- display should not be automatic, but contingent upon some further
- action of the user. The MUA might instead present the user of a
- bitmap terminal with an iconic representation of the attachments, or,
- on character terminals, with a list of attachments from which the
- user could select for viewing or storage.
-
-2.3 The Filename Parameter
-
- The sender may want to suggest a filename to be used if the entity is
- detached and stored in a separate file. If the receiving MUA writes
- the entity to a file, the suggested filename should be used as a
- basis for the actual filename, where possible.
-
- It is important that the receiving MUA not blindly use the suggested
- filename. The suggested filename SHOULD be checked (and possibly
- changed) to see that it conforms to local filesystem conventions,
- does not overwrite an existing file, and does not present a security
- problem (see Security Considerations below).
-
- The receiving MUA SHOULD NOT respect any directory path information
- that may seem to be present in the filename parameter. The filename
- should be treated as a terminal component only. Portable
- specification of directory paths might possibly be done in the future
- via a separate Content-Disposition parameter, but no provision is
- made for it in this draft.
-
- Current [RFC 2045] grammar restricts parameter values (and hence
- Content-Disposition filenames) to US-ASCII. We recognize the great
- desirability of allowing arbitrary character sets in filenames, but
- it is beyond the scope of this document to define the necessary
- mechanisms. We expect that the basic [RFC 1521] `value'
- specification will someday be amended to allow use of non-US-ASCII
- characters, at which time the same mechanism should be used in the
- Content-Disposition filename parameter.
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 4]
-
-RFC 2183 Content-Disposition August 1997
-
-
- Beyond the limitation to US-ASCII, the sending MUA may wish to bear
- in mind the limitations of common filesystems. Many have severe
- length and character set restrictions. Short alphanumeric filenames
- are least likely to require modification by the receiving system.
-
- The presence of the filename parameter does not force an
- implementation to write the entity to a separate file. It is
- perfectly acceptable for implementations to leave the entity as part
- of the normal mail stream unless the user requests otherwise. As a
- consequence, the parameter may be used on any MIME entity, even
- `inline' ones. These will not normally be written to files, but the
- parameter could be used to provide a filename if the receiving user
- should choose to write the part to a file.
-
-2.4 The Creation-Date parameter
-
- The creation-date parameter MAY be used to indicate the date at which
- the file was created. If this parameter is included, the paramter
- value MUST be a quoted-string which contains a representation of the
- creation date of the file in [RFC 822] `date-time' format.
-
- UNIX and POSIX implementors are cautioned that the `st_ctime' file
- attribute of the `stat' structure is not the creation time of the
- file; it is thus not appropriate as a source for the creation-date
- parameter value.
-
-2.5 The Modification-Date parameter
-
- The modification-date parameter MAY be used to indicate the date at
- which the file was last modified. If the modification-date parameter
- is included, the paramter value MUST be a quoted-string which
- contains a representation of the last modification date of the file
- in [RFC 822] `date-time' format.
-
-2.6 The Read-Date parameter
-
- The read-date parameter MAY be used to indicate the date at which the
- file was last read. If the read-date parameter is included, the
- parameter value MUST be a quoted-string which contains a
- representation of the last-read date of the file in [RFC 822] `date-
- time' format.
-
-2.7 The Size parameter
-
- The size parameter indicates an approximate size of the file in
- octets. It can be used, for example, to pre-allocate space before
- attempting to store the file, or to determine whether enough space
- exists.
-
-
-
-Troost, et. al. Standards Track [Page 5]
-
-RFC 2183 Content-Disposition August 1997
-
-
-2.8 Future Extensions and Unrecognized Disposition Types
-
- In the likely event that new parameters or disposition types are
- needed, they should be registered with the Internet Assigned Numbers
- Authority (IANA), in the manner specified in Section 9 of this memo.
-
- Once new disposition types and parameters are defined, there is of
- course the likelihood that implementations will see disposition types
- and parameters they do not understand. Furthermore, since x-tokens
- are allowed, implementations may also see entirely unregistered
- disposition types and parameters.
-
- Unrecognized parameters should be ignored. Unrecognized disposition
- types should be treated as `attachment'. The choice of `attachment'
- for unrecognized types is made because a sender who goes to the
- trouble of producing a Content-Disposition header with a new
- disposition type is more likely aiming for something more elaborate
- than inline presentation.
-
- Unless noted otherwise in the definition of a parameter, Content-
- Disposition parameters are valid for all dispositions. (In contrast
- to MIME content-type parameters, which are defined on a per-content-
- type basis.) Thus, for example, the `filename' parameter still means
- the name of the file to which the part should be written, even if the
- disposition itself is unrecognized.
-
-2.9 Content-Disposition and Multipart
-
- If a Content-Disposition header is used on a multipart body part, it
- applies to the multipart as a whole, not the individual subparts.
- The disposition types of the subparts do not need to be consulted
- until the multipart itself is presented. When the multipart is
- displayed, then the dispositions of the subparts should be respected.
-
- If the `inline' disposition is used, the multipart should be
- displayed as normal; however, an `attachment' subpart should require
- action from the user to display.
-
- If the `attachment' disposition is used, presentation of the
- multipart should not proceed without explicit user action. Once the
- user has chosen to display the multipart, the individual subpart
- dispositions should be consulted to determine how to present the
- subparts.
-
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 6]
-
-RFC 2183 Content-Disposition August 1997
-
-
-2.10 Content-Disposition and the Main Message
-
- It is permissible to use Content-Disposition on the main body of an
- [RFC 822] message.
-
-3. Examples
-
- Here is a an example of a body part containing a JPEG image that is
- intended to be viewed by the user immediately:
-
- Content-Type: image/jpeg
- Content-Disposition: inline
- Content-Description: just a small picture of me
-
- <jpeg data>
-
- The following body part contains a JPEG image that should be
- displayed to the user only if the user requests it. If the JPEG is
- written to a file, the file should be named "genome.jpg". The
- recipient's user might also choose to set the last-modified date of
- the stored file to date in the modification-date parameter:
-
- Content-Type: image/jpeg
- Content-Disposition: attachment; filename=genome.jpeg;
- modification-date="Wed, 12 Feb 1997 16:29:51 -0500";
- Content-Description: a complete map of the human genome
-
- <jpeg data>
-
- The following is an example of the use of the `attachment'
- disposition with a multipart body part. The user should see text-
- part-1 immediately, then take some action to view multipart-2. After
- taking action to view multipart-2, the user will see text-part-2
- right away, and be required to take action to view jpeg-1. Subparts
- are indented for clarity; they would not be so indented in a real
- message.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 7]
-
-RFC 2183 Content-Disposition August 1997
-
-
- Content-Type: multipart/mixed; boundary=outer
- Content-Description: multipart-1
-
- --outer
- Content-Type: text/plain
- Content-Disposition: inline
- Content-Description: text-part-1
-
- Some text goes here
-
- --outer
- Content-Type: multipart/mixed; boundary=inner
- Content-Disposition: attachment
- Content-Description: multipart-2
-
- --inner
- Content-Type: text/plain
- Content-Disposition: inline
- Content-Description: text-part-2
-
- Some more text here.
-
- --inner
- Content-Type: image/jpeg
- Content-Disposition: attachment
- Content-Description: jpeg-1
-
- <jpeg data>
- --inner--
- --outer--
-
-4. Summary
-
- Content-Disposition takes one of two values, `inline' and
- `attachment'. `Inline' indicates that the entity should be
- immediately displayed to the user, whereas `attachment' means that
- the user should take additional action to view the entity.
-
- The `filename' parameter can be used to suggest a filename for
- storing the bodypart, if the user wishes to store it in an external
- file.
-
-
-
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 8]
-
-RFC 2183 Content-Disposition August 1997
-
-
-5. Security Considerations
-
- There are security issues involved any time users exchange data.
- While these are not to be minimized, neither does this memo change
- the status quo in that regard, except in one instance.
-
- Since this memo provides a way for the sender to suggest a filename,
- a receiving MUA must take care that the sender's suggested filename
- does not represent a hazard. Using UNIX as an example, some hazards
- would be:
-
- + Creating startup files (e.g., ".login").
-
- + Creating or overwriting system files (e.g., "/etc/passwd").
-
- + Overwriting any existing file.
-
- + Placing executable files into any command search path
- (e.g., "~/bin/more").
-
- + Sending the file to a pipe (e.g., "| sh").
-
- In general, the receiving MUA should not name or place the file such
- that it will get interpreted or executed without the user explicitly
- initiating the action.
-
- It is very important to note that this is not an exhaustive list; it
- is intended as a small set of examples only. Implementors must be
- alert to the potential hazards on their target systems.
-
-6. References
-
- [RFC 2119]
- Bradner, S., "Key words for use in RFCs to Indicate Requirement
- Levels", RFC 2119, March 1997.
-
- [RFC 2184]
- Freed, N. and K. Moore, "MIME Parameter value and Encoded Words:
- Character Sets, Lanaguage, and Continuations", RFC 2184, August
- 1997.
-
- [RFC 2045]
- Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
- Extensions) Part One: Format of Internet Message Bodies", RFC
- 2045, December 1996.
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 9]
-
-RFC 2183 Content-Disposition August 1997
-
-
- [RFC 2046]
- Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
- Extensions) Part Two: Media Types", RFC 2046, December 1996.
-
- [RFC 2047]
- Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
- Three: Message Header Extensions for non-ASCII Text", RFC 2047,
- December 1996.
-
- [RFC 2048]
- Freed, N., Klensin, J. and J. Postel, "MIME (Multipurpose
- Internet Mail Extensions) Part Four: Registration Procedures",
- RFC 2048, December 1996.
-
- [RFC 2049]
- Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
- Extensions) Part Five: Conformance Criteria and Examples", RFC
- 2049, December 1996.
-
- [RFC 822]
- Crocker, D., "Standard for the Format of ARPA Internet Text
- Messages", STD 11, RFC 822, UDEL, August 1982.
-
-7. Acknowledgements
-
- We gratefully acknowledge the help these people provided during the
- preparation of this draft:
-
- Nathaniel Borenstein
- Ned Freed
- Keith Moore
- Dave Crocker
- Dan Pritchett
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 10]
-
-RFC 2183 Content-Disposition August 1997
-
-
-8. Authors' Addresses
-
- You should blame the editor of this version of the document for any
- changes since RFC 1806:
-
- Keith Moore
- Department of Computer Science
- University of Tennessee, Knoxville
- 107 Ayres Hall
- Knoxville TN 37996-1301
- USA
-
- Phone: +1 (423) 974-5067
- Fax: +1 (423) 974-8296
- Email: moore@cs.utk.edu
-
-
- The authors of RFC 1806 are:
-
- Rens Troost
- New Century Systems
- 324 East 41st Street #804
- New York, NY, 10017 USA
-
- Phone: +1 (212) 557-2050
- Fax: +1 (212) 557-2049
- EMail: rens@century.com
-
-
- Steve Dorner
- QUALCOMM Incorporated
- 6455 Lusk Boulevard
- San Diego, CA 92121
- USA
-
- EMail: sdorner@qualcomm.com
-
-
-9. Registration of New Content-Disposition Values and Parameters
-
- New Content-Disposition values (besides "inline" and "attachment")
- may be defined only by Internet standards-track documents, or in
- Experimental documents approved by the Internet Engineering Steering
- Group.
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 11]
-
-RFC 2183 Content-Disposition August 1997
-
-
- New content-disposition parameters may be registered by supplying the
- information in the following template and sending it via electronic
- mail to IANA@IANA.ORG:
-
- To: IANA@IANA.ORG
- Subject: Registration of new Content-Disposition parameter
-
- Content-Disposition parameter name:
-
- Allowable values for this parameter:
- (If the parameter can only assume a small number of values,
- list each of those values. Otherwise, describe the values
- that the parameter can assume.)
- Description:
- (What is the purpose of this parameter and how is it used?)
-
-10. Changes since RFC 1806
-
- The following changes have been made since the earlier version of
- this document, published in RFC 1806 as an Experimental protocol:
-
- + Updated references to MIME documents. In some cases this
- involved substituting a reference to one of the current MIME
- RFCs for a reference to RFC 1521; in other cases, a reference to
- RFC 1521 was simply replaced with the word "MIME".
-
- + Added a section on registration procedures, since none of the
- procedures in RFC 2048 seemed to be appropriate.
-
- + Added new parameter types: creation-date, modification-date,
- read-date, and size.
-
-
- + Incorporated a reference to draft-freed-pvcsc-* for encoding
- long or non-ASCII parameter values.
-
- + Added reference to RFC 2119 to define MUST, SHOULD, etc.
- keywords.
-
-
-
-
-
-
-
-
-
-
-
-
-
-Troost, et. al. Standards Track [Page 12]
-
diff --git a/proto/rfc2231.txt b/proto/rfc2231.txt
@@ -1,563 +0,0 @@
-
-
-
-
-
-
-Network Working Group N. Freed
-Request for Comments: 2231 Innosoft
-Updates: 2045, 2047, 2183 K. Moore
-Obsoletes: 2184 University of Tennessee
-Category: Standards Track November 1997
-
-
- MIME Parameter Value and Encoded Word Extensions:
- Character Sets, Languages, and Continuations
-
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1997). All Rights Reserved.
-
-1. Abstract
-
- This memo defines extensions to the RFC 2045 media type and RFC 2183
- disposition parameter value mechanisms to provide
-
- (1) a means to specify parameter values in character sets
- other than US-ASCII,
-
- (2) to specify the language to be used should the value be
- displayed, and
-
- (3) a continuation mechanism for long parameter values to
- avoid problems with header line wrapping.
-
- This memo also defines an extension to the encoded words defined in
- RFC 2047 to allow the specification of the language to be used for
- display as well as the character set.
-
-2. Introduction
-
- The Multipurpose Internet Mail Extensions, or MIME [RFC-2045, RFC-
- 2046, RFC-2047, RFC-2048, RFC-2049], define a message format that
- allows for:
-
-
-
-
-
-Freed & Moore Standards Track [Page 1]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- (1) textual message bodies in character sets other than
- US-ASCII,
-
- (2) non-textual message bodies,
-
- (3) multi-part message bodies, and
-
- (4) textual header information in character sets other than
- US-ASCII.
-
- MIME is now widely deployed and is used by a variety of Internet
- protocols, including, of course, Internet email. However, MIME's
- success has resulted in the need for additional mechanisms that were
- not provided in the original protocol specification.
-
- In particular, existing MIME mechanisms provide for named media type
- (content-type field) parameters as well as named disposition
- (content-disposition field). A MIME media type may specify any
- number of parameters associated with all of its subtypes, and any
- specific subtype may specify additional parameters for its own use. A
- MIME disposition value may specify any number of associated
- parameters, the most important of which is probably the attachment
- disposition's filename parameter.
-
- These parameter names and values end up appearing in the content-type
- and content-disposition header fields in Internet email. This
- inherently imposes three crucial limitations:
-
- (1) Lines in Internet email header fields are folded
- according to RFC 822 folding rules. This makes long
- parameter values problematic.
-
- (2) MIME headers, like the RFC 822 headers they often
- appear in, are limited to 7bit US-ASCII, and the
- encoded-word mechanisms of RFC 2047 are not available
- to parameter values. This makes it impossible to have
- parameter values in character sets other than US-ASCII
- without specifying some sort of private per-parameter
- encoding.
-
- (3) It has recently become clear that character set
- information is not sufficient to properly display some
- sorts of information -- language information is also
- needed [RFC-2130]. For example, support for
- handicapped users may require reading text string
-
-
-
-
-
-
-Freed & Moore Standards Track [Page 2]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- aloud. The language the text is written in is needed
- for this to be done correctly. Some parameter values
- may need to be displayed, hence there is a need to
- allow for the inclusion of language information.
-
- The last problem on this list is also an issue for the encoded words
- defined by RFC 2047, as encoded words are intended primarily for
- display purposes.
-
- This document defines extensions that address all of these
- limitations. All of these extensions are implemented in a fashion
- that is completely compatible at a syntactic level with existing MIME
- implementations. In addition, the extensions are designed to have as
- little impact as possible on existing uses of MIME.
-
- IMPORTANT NOTE: These mechanisms end up being somewhat gibbous when
- they actually are used. As such, these mechanisms should not be used
- lightly; they should be reserved for situations where a real need for
- them exists.
-
-2.1. Requirements notation
-
- This document occasionally uses terms that appear in capital letters.
- When the terms "MUST", "SHOULD", "MUST NOT", "SHOULD NOT", and "MAY"
- appear capitalized, they are being used to indicate particular
- requirements of this specification. A discussion of the meanings of
- these terms appears in [RFC- 2119].
-
-3. Parameter Value Continuations
-
- Long MIME media type or disposition parameter values do not interact
- well with header line wrapping conventions. In particular, proper
- header line wrapping depends on there being places where linear
- whitespace (LWSP) is allowed, which may or may not be present in a
- parameter value, and even if present may not be recognizable as such
- since specific knowledge of parameter value syntax may not be
- available to the agent doing the line wrapping. The result is that
- long parameter values may end up getting truncated or otherwise
- damaged by incorrect line wrapping implementations.
-
- A mechanism is therefore needed to break up parameter values into
- smaller units that are amenable to line wrapping. Any such mechanism
- MUST be compatible with existing MIME processors. This means that
-
- (1) the mechanism MUST NOT change the syntax of MIME media
- type and disposition lines, and
-
-
-
-
-
-Freed & Moore Standards Track [Page 3]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- (2) the mechanism MUST NOT depend on parameter ordering
- since MIME states that parameters are not order
- sensitive. Note that while MIME does prohibit
- modification of MIME headers during transport, it is
- still possible that parameters will be reordered when
- user agent level processing is done.
-
- The obvious solution, then, is to use multiple parameters to contain
- a single parameter value and to use some kind of distinguished name
- to indicate when this is being done. And this obvious solution is
- exactly what is specified here: The asterisk character ("*") followed
- by a decimal count is employed to indicate that multiple parameters
- are being used to encapsulate a single parameter value. The count
- starts at 0 and increments by 1 for each subsequent section of the
- parameter value. Decimal values are used and neither leading zeroes
- nor gaps in the sequence are allowed.
-
- The original parameter value is recovered by concatenating the
- various sections of the parameter, in order. For example, the
- content-type field
-
- Content-Type: message/external-body; access-type=URL;
- URL*0="ftp://";
- URL*1="cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"
-
- is semantically identical to
-
- Content-Type: message/external-body; access-type=URL;
- URL="ftp://cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"
-
- Note that quotes around parameter values are part of the value
- syntax; they are NOT part of the value itself. Furthermore, it is
- explicitly permitted to have a mixture of quoted and unquoted
- continuation fields.
-
-4. Parameter Value Character Set and Language Information
-
- Some parameter values may need to be qualified with character set or
- language information. It is clear that a distinguished parameter
- name is needed to identify when this information is present along
- with a specific syntax for the information in the value itself. In
- addition, a lightweight encoding mechanism is needed to accommodate 8
- bit information in parameter values.
-
-
-
-
-
-
-
-
-Freed & Moore Standards Track [Page 4]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- Asterisks ("*") are reused to provide the indicator that language and
- character set information is present and encoding is being used. A
- single quote ("'") is used to delimit the character set and language
- information at the beginning of the parameter value. Percent signs
- ("%") are used as the encoding flag, which agrees with RFC 2047.
-
- Specifically, an asterisk at the end of a parameter name acts as an
- indicator that character set and language information may appear at
- the beginning of the parameter value. A single quote is used to
- separate the character set, language, and actual value information in
- the parameter value string, and an percent sign is used to flag
- octets encoded in hexadecimal. For example:
-
- Content-Type: application/x-stuff;
- title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A
-
- Note that it is perfectly permissible to leave either the character
- set or language field blank. Note also that the single quote
- delimiters MUST be present even when one of the field values is
- omitted. This is done when either character set, language, or both
- are not relevant to the parameter value at hand. This MUST NOT be
- done in order to indicate a default character set or language --
- parameter field definitions MUST NOT assign a default character set
- or language.
-
-4.1. Combining Character Set, Language, and Parameter Continuations
-
- Character set and language information may be combined with the
- parameter continuation mechanism. For example:
-
- Content-Type: application/x-stuff
- title*0*=us-ascii'en'This%20is%20even%20more%20
- title*1*=%2A%2A%2Afun%2A%2A%2A%20
- title*2="isn't it!"
-
- Note that:
-
- (1) Language and character set information only appear at
- the beginning of a given parameter value.
-
- (2) Continuations do not provide a facility for using more
- than one character set or language in the same
- parameter value.
-
- (3) A value presented using multiple continuations may
- contain a mixture of encoded and unencoded segments.
-
-
-
-
-
-Freed & Moore Standards Track [Page 5]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- (4) The first segment of a continuation MUST be encoded if
- language and character set information are given.
-
- (5) If the first segment of a continued parameter value is
- encoded the language and character set field delimiters
- MUST be present even when the fields are left blank.
-
-5. Language specification in Encoded Words
-
- RFC 2047 provides support for non-US-ASCII character sets in RFC 822
- message header comments, phrases, and any unstructured text field.
- This is done by defining an encoded word construct which can appear
- in any of these places. Given that these are fields intended for
- display, it is sometimes necessary to associate language information
- with encoded words as well as just the character set. This
- specification extends the definition of an encoded word to allow the
- inclusion of such information. This is simply done by suffixing the
- character set specification with an asterisk followed by the language
- tag. For example:
-
- From: =?US-ASCII*EN?Q?Keith_Moore?= <moore@cs.utk.edu>
-
-6. IMAP4 Handling of Parameter Values
-
- IMAP4 [RFC-2060] servers SHOULD decode parameter value continuations
- when generating the BODY and BODYSTRUCTURE fetch attributes.
-
-7. Modifications to MIME ABNF
-
- The ABNF for MIME parameter values given in RFC 2045 is:
-
- parameter := attribute "=" value
-
- attribute := token
- ; Matching of attributes
- ; is ALWAYS case-insensitive.
-
- This specification changes this ABNF to:
-
- parameter := regular-parameter / extended-parameter
-
- regular-parameter := regular-parameter-name "=" value
-
- regular-parameter-name := attribute [section]
-
- attribute := 1*attribute-char
-
-
-
-
-
-Freed & Moore Standards Track [Page 6]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- attribute-char := <any (US-ASCII) CHAR except SPACE, CTLs,
- "*", "'", "%", or tspecials>
-
- section := initial-section / other-sections
-
- initial-section := "*0"
-
- other-sections := "*" ("1" / "2" / "3" / "4" / "5" /
- "6" / "7" / "8" / "9") *DIGIT)
-
- extended-parameter := (extended-initial-name "="
- extended-value) /
- (extended-other-names "="
- extended-other-values)
-
- extended-initial-name := attribute [initial-section] "*"
-
- extended-other-names := attribute other-sections "*"
-
- extended-initial-value := [charset] "'" [language] "'"
- extended-other-values
-
- extended-other-values := *(ext-octet / attribute-char)
-
- ext-octet := "%" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
-
- charset := <registered character set name>
-
- language := <registered language tag [RFC-1766]>
-
- The ABNF given in RFC 2047 for encoded-words is:
-
- encoded-word := "=?" charset "?" encoding "?" encoded-text "?="
-
- This specification changes this ABNF to:
-
- encoded-word := "=?" charset ["*" language] "?" encoded-text "?="
-
-8. Character sets which allow specification of language
-
- In the future it is likely that some character sets will provide
- facilities for inline language labeling. Such facilities are
- inherently more flexible than those defined here as they allow for
- language switching in the middle of a string.
-
-
-
-
-
-
-
-Freed & Moore Standards Track [Page 7]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- If and when such facilities are developed they SHOULD be used in
- preference to the language labeling facilities specified here. Note
- that all the mechanisms defined here allow for the omission of
- language labels so as to be able to accommodate this possible future
- usage.
-
-9. Security Considerations
-
- This RFC does not discuss security issues and is not believed to
- raise any security issues not already endemic in electronic mail and
- present in fully conforming implementations of MIME.
-
-10. References
-
- [RFC-822]
- Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", STD 11, RFC 822 August 1982.
-
- [RFC-1766]
- Alvestrand, H., "Tags for the Identification of
- Languages", RFC 1766, March 1995.
-
- [RFC-2045]
- Freed, N., and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part One: Format of Internet Message
- Bodies", RFC 2045, December 1996.
-
- [RFC-2046]
- Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Two: Media Types", RFC 2046,
- December 1996.
-
- [RFC-2047]
- Moore, K., "Multipurpose Internet Mail Extensions (MIME)
- Part Three: Representation of Non-ASCII Text in Internet
- Message Headers", RFC 2047, December 1996.
-
- [RFC-2048]
- Freed, N., Klensin, J. and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) Part Four: MIME
- Registration Procedures", RFC 2048, December 1996.
-
- [RFC-2049]
- Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Five: Conformance Criteria and
- Examples", RFC 2049, December 1996.
-
-
-
-
-
-Freed & Moore Standards Track [Page 8]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
- [RFC-2060]
- Crispin, M., "Internet Message Access Protocol - Version
- 4rev1", RFC 2060, December 1996.
-
- [RFC-2119]
- Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", RFC 2119, March 1997.
-
- [RFC-2130]
- Weider, C., Preston, C., Simonsen, K., Alvestrand, H.,
- Atkinson, R., Crispin, M., and P. Svanberg, "Report from the
- IAB Character Set Workshop", RFC 2130, April 1997.
-
- [RFC-2183]
- Troost, R., Dorner, S. and K. Moore, "Communicating
- Presentation Information in Internet Messages: The
- Content-Disposition Header", RFC 2183, August 1997.
-
-11. Authors' Addresses
-
- Ned Freed
- Innosoft International, Inc.
- 1050 Lakes Drive
- West Covina, CA 91790
- USA
-
- Phone: +1 626 919 3600
- Fax: +1 626 919 3614
- EMail: ned.freed@innosoft.com
-
-
- Keith Moore
- Computer Science Dept.
- University of Tennessee
- 107 Ayres Hall
- Knoxville, TN 37996-1301
- USA
-
- EMail: moore@cs.utk.edu
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Moore Standards Track [Page 9]
-
-RFC 2231 MIME Value and Encoded Word Extensions November 1997
-
-
-12. Full Copyright Statement
-
- Copyright (C) The Internet Society (1997). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Freed & Moore Standards Track [Page 10]
-
diff --git a/proto/rfc2387.txt b/proto/rfc2387.txt
@@ -1,563 +0,0 @@
-
-
-
-
-
-
-Network Working Group E. Levinson
-Request for Comments: 2387 August 1998
-Obsoletes: 2112
-Category: Standards Track
-
-
- The MIME Multipart/Related Content-type
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
-Abstract
-
- The Multipart/Related content-type provides a common mechanism for
- representing objects that are aggregates of related MIME body parts.
- This document defines the Multipart/Related content-type and provides
- examples of its use.
-
-1. Introduction
-
- Several applications of MIME, including MIME-PEM, and MIME-Macintosh
- and other proposals, require multiple body parts that make sense only
- in the aggregate. The present approach to these compound objects has
- been to define specific multipart subtypes for each new object. In
- keeping with the MIME philosophy of having one mechanism to achieve
- the same goal for different purposes, this document describes a
- single mechanism for such aggregate or compound objects.
-
- The Multipart/Related content-type addresses the MIME representation
- of compound objects. The object is categorized by a "type"
- parameter. Additional parameters are provided to indicate a specific
- starting body part or root and auxiliary information which may be
- required when unpacking or processing the object.
-
- Multipart/Related MIME entities may contain Content-Disposition
- headers that provide suggestions for the storage and display of a
- body part. Multipart/Related processing takes precedence over
- Content-Disposition; the interaction between them is discussed in
- section 4.
-
-
-
-Levinson Standards Track [Page 1]
-
-RFC 2387 Multipart/Related August 1998
-
-
- Responsibility for the display or processing of a Multipart/Related's
- constituent entities rests with the application that handles the
- compound object.
-
-2. Multipart/Related Registration Information
-
- The following form is copied from RFC 1590, Appendix A.
-
- To: IANA@isi.edu
- Subject: Registration of new Media Type content-type/subtype
-
- Media Type name: Multipart
-
- Media subtype name: Related
-
- Required parameters: Type, a media type/subtype.
-
- Optional parameters: Start
- Start-info
-
- Encoding considerations: Multipart content-types cannot have
- encodings.
-
- Security considerations: Depends solely on the referenced type.
-
- Published specification: RFC-REL (this document).
-
- Person & email address to contact for further information:
- Edward Levinson
- 47 Clive Street
- Metuchen, NJ 08840-1060
- +1 908 494 1606
- XIson@cnj.digex.net
-
-3. Intended usage
-
- The Multipart/Related media type is intended for compound objects
- consisting of several inter-related body parts. For a
- Multipart/Related object, proper display cannot be achieved by
- individually displaying the constituent body parts. The content-type
- of the Multipart/Related object is specified by the type parameter.
- The "start" parameter, if given, points, via a content-ID, to the
- body part that contains the object root. The default root is the
- first body part within the Multipart/Related body.
-
- The relationships among the body parts of a compound object
- distinguishes it from other object types. These relationships are
- often represented by links internal to the object's components that
-
-
-
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-
-RFC 2387 Multipart/Related August 1998
-
-
- reference the other components. Within a single operating
- environment the links are often file names, such links may be
- represented within a MIME message using content-IDs or the value of
- some other "Content-" headers.
-
-3.1. The Type Parameter
-
- The type parameter must be specified and its value is the MIME media
- type of the "root" body part. It permits a MIME user agent to
- determine the content-type without reference to the enclosed body
- part. If the value of the type parameter and the root body part's
- content-type differ then the User Agent's behavior is undefined.
-
-3.2. The Start Parameter
-
- The start parameter, if given, is the content-ID of the compound
- object's "root". If not present the "root" is the first body part in
- the Multipart/Related entity. The "root" is the element the
- applications processes first.
-
-3.3. The Start-Info Parameter
-
- Additional information can be provided to an application by the
- start-info parameter. It contains either a string or points, via a
- content-ID, to another MIME entity in the message. A typical use
- might be to provide additional command line parameters or a MIME
- entity giving auxiliary information for processing the compound
- object.
-
- Applications that use Multipart/Related must specify the
- interpretation of start-info. User Agents shall provide the
- parameter's value to the processing application. Processes can
- distinguish a start-info reference from a token or quoted-string by
- examining the first non-white-space character, "<" indicates a
- reference.
-
-3.4. Syntax
-
- related-param := [ ";" "start" "=" cid ]
- [ ";" "start-info" "="
- ( cid-list / value ) ]
- [ ";" "type" "=" type "/" subtype ]
- ; order independent
-
- cid-list := cid cid-list
-
- cid := msg-id ; c.f. [822]
-
-
-
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-RFC 2387 Multipart/Related August 1998
-
-
- value := token / quoted-string ; c.f. [MIME]
- ; value cannot begin with "<"
-
- Note that the parameter values will usually require quoting. Msg-id
- contains the special characters "<", ">", "@", and perhaps other
- special characters. If msg-id contains quoted-strings, those quote
- marks must be escaped. Similarly, the type parameter contains the
- special character "/".
-
-4. Handling Content-Disposition Headers
-
- Content-Disposition Headers [DISP] suggest presentation styles for
- MIME body parts. [DISP] describes two presentation styles, called
- the disposition type, INLINE and ATTACHMENT. These, used within a
- multipart entity, allow the sender to suggest presentation
- information. [DISP] also provides for an optional storage (file)
- name. Content-Disposition headers could appear in one or more body
- parts contained within a Multipart/Related entity.
-
- Using Content-Disposition headers in addition to Multipart/Related
- provides presentation information to User Agents that do not
- recognize Multipart/Related. They will treat the multipart as
- Multipart/Mixed and they may find the Content-Disposition information
- useful.
-
- With Multipart/Related however, the application processing the
- compound object determines the presentation style for all the
- contained parts. In that context the Content-Disposition header
- information is redundant or even misleading. Hence, User Agents that
- understand Multipart/Related shall ignore the disposition type within
- a Multipart/Related body part.
-
- It may be possible for a User Agent capable of handling both
- Multipart/Related and Content-Disposition headers to provide the
- invoked application the Content-Disposition header's optional
- filename parameter to the Multipart/Related. The use of that
- information will depend on the specific application and should be
- specified when describing the handling of the corresponding compound
- object. Such descriptions would be appropriate in an RFC registering
- that object's media type.
-
-5. Examples
-
-5.1 Application/X-FixedRecord
-
- The X-FixedRecord content-type consists of one or more octet-streams
- and a list of the lengths of each record. The root, which lists the
- record lengths of each record within the streams. The record length
-
-
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-
-
- list, type Application/X-FixedRecord, consists of a set of INTEGERs
- in ASCII format, one per line. Each INTEGER gives the number of
- octets from the octet-stream body part that constitute the next
- "record".
-
- The example below, uses a single data block.
-
- Content-Type: Multipart/Related; boundary=example-1
- start="<950120.aaCC@XIson.com>";
- type="Application/X-FixedRecord"
- start-info="-o ps"
-
- --example-1
- Content-Type: Application/X-FixedRecord
- Content-ID: <950120.aaCC@XIson.com>
-
- 25
- 10
- 34
- 10
- 25
- 21
- 26
- 10
- --example-1
- Content-Type: Application/octet-stream
- Content-Description: The fixed length records
- Content-Transfer-Encoding: base64
- Content-ID: <950120.aaCB@XIson.com>
-
- T2xkIE1hY0RvbmFsZCBoYWQgYSBmYXJtCkUgSS
- BFIEkgTwpBbmQgb24gaGlzIGZhcm0gaGUgaGFk
- IHNvbWUgZHVja3MKRSBJIEUgSSBPCldpdGggYS
- BxdWFjayBxdWFjayBoZXJlLAphIHF1YWNrIHF1
- YWNrIHRoZXJlLApldmVyeSB3aGVyZSBhIHF1YW
- NrIHF1YWNrCkUgSSBFIEkgTwo=
-
- --example-1--
-
-
-
-
-
-
-
-
-
-
-
-
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-
-5.2 Text/X-Okie
-
- The Text/X-Okie is an invented markup language permitting the
- inclusion of images with text. A feature of this example is the
- inclusion of two additional body parts, both picture. They are
- referred to internally by the encapsulated document via each
- picture's body part content-ID. Usage of "cid:", as in this example,
- may be useful for a variety of compound objects. It is not, however,
- a part of the Multipart/Related specification.
-
- Content-Type: Multipart/Related; boundary=example-2;
- start="<950118.AEBH@XIson.com>"
- type="Text/x-Okie"
-
- --example-2
- Content-Type: Text/x-Okie; charset=iso-8859-1;
- declaration="<950118.AEB0@XIson.com>"
- Content-ID: <950118.AEBH@XIson.com>
- Content-Description: Document
-
- {doc}
- This picture was taken by an automatic camera mounted ...
- {image file=cid:950118.AECB@XIson.com}
- {para}
- Now this is an enlargement of the area ...
- {image file=cid:950118:AFDH@XIson.com}
- {/doc}
- --example-2
- Content-Type: image/jpeg
- Content-ID: <950118.AFDH@XIson.com>
- Content-Transfer-Encoding: BASE64
- Content-Description: Picture A
-
- [encoded jpeg image]
- --example-2
- Content-Type: image/jpeg
- Content-ID: <950118.AECB@XIson.com>
- Content-Transfer-Encoding: BASE64
- Content-Description: Picture B
-
- [encoded jpeg image]
- --example-2--
-
-5.3 Content-Disposition
-
- In the above example each image body part could also have a Content-
- Disposition header. For example,
-
-
-
-
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-RFC 2387 Multipart/Related August 1998
-
-
- --example-2
- Content-Type: image/jpeg
- Content-ID: <950118.AECB@XIson.com>
- Content-Transfer-Encoding: BASE64
- Content-Description: Picture B
- Content-Disposition: INLINE
-
- [encoded jpeg image]
- --example-2--
-
- User Agents that recognize Multipart/Related will ignore the
- Content-Disposition header's disposition type. Other User Agents
- will process the Multipart/Related as Multipart/Mixed and may make
- use of that header's information.
-
-6. User Agent Requirements
-
- User agents that do not recognize Multipart/Related shall, in
- accordance with [MIME], treat the entire entity as Multipart/Mixed.
- MIME User Agents that do recognize Multipart/Related entities but are
- unable to process the given type should give the user the option of
- suppressing the entire Multipart/Related body part shall be.
-
- Existing MIME-capable mail user agents (MUAs) handle the existing
- media types in a straightforward manner. For discrete media types
- (e.g. text, image, etc.) the body of the entity can be directly
- passed to a display process. Similarly the existing composite
- subtypes can be reduced to handing one or more discrete types.
- Handling Multipart/Related differs in that processing cannot be
- reduced to handling the individual entities.
-
- The following sections discuss what information the processing
- application requires.
-
- It is possible that an application specific "receiving agent" will
- manipulate the entities for display prior to invoking actual
- application process. Okie, above, is an example of this; it may need
- a receiving agent to parse the document and substitute local file
- names for the originator's file names. Other applications may just
- require a table showing the correspondence between the local file
- names and the originator's. The receiving agent takes responsibility
- for such processing.
-
-6.1 Data Requirements
-
- MIME-capable mail user agents (MUAs) are required to provide the
- application:
-
-
-
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-
-
- (a) the bodies of the MIME entities and the entity Content-* headers,
-
- (b) the parameters of the Multipart/Related Content-type header, and
-
- (c) the correspondence between each body's local file name, that
- body's header data, and, if present, the body part's content-ID.
-
-6.2 Storing Multipart/Related Entities
-
- The Multipart/Related media type will be used for objects that have
- internal linkages between the body parts. When the objects are
- stored the linkages may require processing by the application or its
- receiving agent.
-
-6.3 Recursion
-
- MIME is a recursive structure. Hence one must expect a
- Multipart/Related entity to contain other Multipart/Related entities.
- When a Multipart/Related entity is being processed for display or
- storage, any enclosed Multipart/Related entities shall be processed
- as though they were being stored.
-
-6.4 Configuration Considerations
-
- It is suggested that MUAs that use configuration mechanisms, see
- [CFG] for an example, refer to Multipart/Related as Multi-
- part/Related/<type>, were <type> is the value of the "type"
- parameter.
-
-7. Security Considerations
-
- Security considerations relevant to Multipart/Related are identical
- to those of the underlying content-type.
-
-8. Acknowledgments
-
- This proposal is the result of conversations the author has had with
- many people. In particular, Harald A. Alvestrand, James Clark,
- Charles Goldfarb, Gary Houston, Ned Freed, Ray Moody, and Don
- Stinchfield, provided both encouragement and invaluable help. The
- author, however, take full responsibility for all errors contained in
- this document.
-
-
-
-
-
-
-
-
-
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-RFC 2387 Multipart/Related August 1998
-
-
-9. References
-
- [822] Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", STD 11, RFC 822, August 1982.
-
- [CID] Levinson, E., and J. Clark, "Message/External-Body
- Content-ID Access Type", RFC 1873, December 1995,
- Levinson, E., "Message/External-Body Content-ID Access
- Type", Work in Progress.
-
- [CFG] Borenstein, N., "A User Agent Configuration Mechanism For
- Multimedia Mail Format Information", RFC 1524, September
- 1993.
-
- [DISP] Troost, R., and S. Dorner, "Communicating Presentation
- Information in Internet Messages: The Content-
- Disposition Header", RFC 1806, June 1995.
-
- [MIME] Borenstein, N., and Freed, N., "Multipurpose Internet
- Mail Extensions (MIME) Part One: Format of Internet
- Message Bodies", RFC 2045, November 1996.
-
-9. Author's Address
-
- Edward Levinson
- 47 Clive Street
- Metuchen, NJ 08840-1060
- USA
-
- Phone: +1 908 494 1606
- EMail: XIson@cnj.digex.com
-
-10. Changes from previous draft (RFC 2112)
-
- Corrected cid urls to conform to RFC 2111; the angle brackets were
- removed.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
-11. Full Copyright Statement
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
diff --git a/proto/rfc2425.txt b/proto/rfc2425.txt
@@ -1,1851 +0,0 @@
-
-
-
-
-
-
-Network Working Group T. Howes
-Request for Comments: 2425 M. Smith
-Category: Standards Track Netscape Communications Corp.
- F. Dawson
- Lotus Development Corporation
- September 1998
-
-
- A MIME Content-Type for Directory Information
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
-1. Abstract
-
- This document defines a MIME Content-Type for holding directory
- information. The definition is independent of any particular
- directory service or protocol. The text/directory Content-Type is
- defined for holding a variety of directory information, for example,
- name, or email address, or logo. The text/directory Content-Type can
- also be used as the root body part in a multipart/related Content-
- Type for handling more complicated situations, especially those in
- which non-textual information that already has a natural MIME
- representation, for example, a photograph or sound, is to be
- represented.
-
- The text/directory Content-Type defines a general framework and
- format for holding directory information in a simple "type:value"
- form. We refer to "type" in this context meaning a property or
- attribute with which the value is associated. Mechanisms are defined
- to specify alternate languages, encodings and other meta-information.
- This document also defines the procedure by which particular formats,
- called profiles, for carrying application-specific information within
- a text/directory Content-Type can be defined and registered, and the
- conventions such formats must follow. It is expected that other
- documents will be produced that define such formats for various
- applications (e.g., white pages).
-
-
-
-
-
-Howes, et. al. Standards Track [Page 1]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
- document are to be interpreted as described in [RFC-2119].
-
-2. Table of Contents
-
- Status of the Memo................................................ 1
- Copyright Notice.................................................. 1
- 1. Abstract...................................................... 1
- 2. Table of Contents............................................. 2
- 3. Need for a MIME Directory Type................................ 3
- 4. Overview...................................................... 4
- 5. The text/directory Content-Type............................... 4
- 5.1. MIME media type name........................................ 4
- 5.2. MIME subtype name........................................... 5
- 5.3. Required parameters......................................... 5
- 5.4. Optional parameters......................................... 5
- 5.5. Encoding considerations..................................... 5
- 5.6. Security considerations..................................... 6
- 5.7. Interoperability considerations............................. 6
- 5.8. Published specification..................................... 6
- 5.8.1. Line delimiting and folding............................... 6
- 5.8.2. ABNF content-type definition.............................. 7
- 5.8.3. Pre-defined Parameters.................................... 9
- 5.8.4. Pre-defined Value Types...................................11
- 5.9. Applications which use this media type......................14
- 5.10. Additional information.....................................14
- 5.11. Person & email address to contact for further information..14
- 5.12. Intended usage.............................................14
- 5.13. Author/Change controller...................................15
- 6. Predefined Types..............................................15
- 6.1. SOURCE Type Definition......................................15
- 6.2. NAME Type Definition........................................16
- 6.3. PROFILE Type Definition.....................................16
- 6.4. BEGIN Type Definition.......................................17
- 6.5. END Type Definition.........................................17
- 7. Use of the multipart/related Content-Type.....................18
- 8. Examples.......................................................18
- 8.1. Example 1...................................................19
- 8.2. Example 2...................................................19
- 8.3. Example 3...................................................20
- 8.4. Example 4...................................................21
- 9. Registration of new profiles..................................22
- 9.1. Define the profile..........................................22
- 9.2. Post the profile definition.................................23
- 9.3. Allow a comment period......................................23
- 9.4. Submit the profile for approval.............................23
- 10. Profile Change Control.......................................23
-
-
-
-Howes, et. al. Standards Track [Page 2]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- 11. Registration of new types....................................24
- 11.1. Define the type............................................24
- 11.2. Post the type definition...................................25
- 11.3. Allow a comment period.....................................25
- 11.4. Submit the type for approval...............................25
- 12. Type Change Control..........................................25
- 13. Registration of new parameters...............................26
- 13.1. Define the parameter.......................................26
- 13.2. Post the parameter definition..............................27
- 13.3. Allow a comment period.....................................27
- 13.4. Submit the parameter for approval..........................27
- 14. Parameter Change Control.....................................28
- 15. Registration of new value types..............................28
- 15.1. Define the value type......................................28
- 15.2. Post the value type definition.............................29
- 15.3. Allow a comment period.....................................29
- 15.4. Submit the value type for approval.........................29
- 16. Security Considerations......................................30
- 17. Acknowledgements..............................................30
- 18. References....................................................30
- 19. Authors' Addresses...........................................32
- 20. Full Copyright Statement......................................33
-
-3. Need for a MIME Directory Type
-
- For purposes of this document, a directory is a special-purpose
- database that contains typed information. A directory usually
- supports both read and search of the information it contains, and can
- support creation and modification of the information as well.
- Directory information is usually accessed far more often than it is
- updated. Directories can be local or global in scope. They can be
- distributed or centralized. The information they contain can be
- replicated, with weak or strong consistency requirements.
-
- There are several situations in which users of Internet mail might
- wish to exchange directory information: the email analogy of a
- "business card" exchange; the conveyance of directory information to
- a user having only email access to the Internet; the provision of
- machine-parseable address information when purchasing goods or
- services over the Internet; etc. As MIME [RFC-2045, RFC-2046] is
- used increasingly by other protocols, most notably HTTP, it can also
- be useful for these protocols to carry directory information in MIME
- format. Such a format, for example, could be used to represent URC
- (uniform resource characteristics) information about resources on the
- World Wide Web, or to provide a rudimentary directory service over
- HTTP.
-
-
-
-
-
-Howes, et. al. Standards Track [Page 3]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-4. Overview
-
- The scheme defined here for representing directory information in a
- MIME Content-Type has two parts. First, the text/directory Content-
- Type is defined for use in holding directory information within a
- single body part, for example name, title, or email address. In its
- simplest form, the format uses a "type:value" approach, which should
- be easily parseable by existing MIME implementations and
- understandable by users. More complicated situations can be
- represented also. This document defines the general form the
- information in the Content-Type should have, and the procedure by
- which specific types and values (properties) for particular
- applications can be defined. The framework is general enough to
- handle information from any number of end directory services,
- including LDAP [RFC-1777, RFC-1778], WHOIS++ [RFC-1835], and X.500
- [X500].
-
- Directory entries can include far more than just textual information.
- Some such information (e.g., an image or sound) overlaps with
- predefined MIME Content-Types. In these cases it can be desirable to
- include the information in its well-known MIME format. This situation
- is handled by using a multipart/related Content-Type as defined in
- [RFC-2112]. The root component of this type is a text/directory body
- part specifying any in-line information, and for information
- contained in other Content-Types, the Content-IDs (in URI form) of
- those parts.
-
- In some applications, it can be useful to include a pointer (e.g, a
- URI) to some directory information rather than the information
- itself. This document defines a general mechanism for accomplishing
- this.
-
-5. The text/directory Content-Type
-
- The text/directory Content-Type is used to hold basic directory
- information and URIs referencing other information, including other
- MIME body parts holding supplementary or non-textual directory
- information, such as an image or sound. It is defined as follows,
- using the MIME media type registration template from [RFC-2048].
-
- To: ietf-types@uninett.no
- Subject: Registration of MIME media type text/directory
-
-5.1. MIME media type name
-
- MIME media type name: text
-
-
-
-
-
-Howes, et. al. Standards Track [Page 4]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-5.2. MIME subtype name
-
- MIME subtype name: directory
-
-5.3. Required parameters
-
- Required parameters: charset
-
- The "charset" parameter is as defined in [RFC-2046] for other body
- parts. It is used to identify the default character set used within
- the body part.
-
-5.4. Optional parameters
-
- Optional parameters: profile
-
- The "profile" parameter is used to convey the type(s) of entity(ies)
- to which the directory information pertains and the likely set of
- information associated with the entity(ies). It is intended only as a
- guide to applications interpreting the information contained within
- the body part. It SHOULD NOT be used to exclude or require particular
- pieces of information unless a profile definition specifically calls
- for this behavior. Unless specifically forbidden by a particular
- profile definition, a text/directory content type can contain
- arbitrary attribute/value pairs.
-
- The value of the "profile" parameter is defined as follows. Profile
- names are case insensitive (i.e., the profile name "vCard" is the
- same as "VCARD" and "vcard" and "vcArD").
-
- profile = x-name / iana-token
-
- x-name = "x-" 1*(ALPHA / DIGIT / "-")
- ; Names beginning with "x-" or "X-" are
- ; reserved for experimental use not intended for released
- ; products, or for use in bilateral agreements.
-
- iana-token = <a publicly-defined extension token, registered
- with IANA, as specified in Section 9 of this
- document>
-
-5.5. Encoding considerations
-
- The default encoding is 8bit. Otherwise, as specified by the
- Content-Transfer-Encoding header field.
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 5]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-5.6. Security considerations
-
- Directory information can be public or it can be protected from
- unauthorized access by the directory service in which it resides.
- Once the information leaves its native service, there can be no
- guarantee that the same care will be taken by all services handling
- the information. Furthermore, this specification defines no access
- control mechanism by which information can be protected, or by which
- access control information can be conveyed. Note that the integrity
- and privacy of a text/directory body part can be protected by
- enclosing it within an appropriate MIME-based security mechanism.
-
-5.7. Interoperability considerations
-
- In order to make sense of directory information, applications must
- share a common understanding of the types of information contained
- within the Content-Type (the directory schema). This schema
- information is not defined in this document, but rather in companion
- documents (e.g., [MIME-VCARD]) that follow the requirements specified
- in this document, or in bilateral agreements between communicating
- parties.
-
-5.8. Published specification
-
- The text/directory Content-Type contains directory information,
- typically pertaining to a single directory entity or group of
- entities. The content consists of one or more lines in the format
- given below.
-
-5.8.1. Line delimiting and folding
-
- Individual lines within the MIME text/directory Content Type body are
- delimited by the [RFC-822] line break, which is a CRLF sequence
- (ASCII decimal 13, followed by ASCII decimal 10). Long logical lines
- of text can be split into a multiple-physical-line representation
- using the following folding technique.
-
- A logical line MAY be continued on the next physical line anywhere
- between two characters by inserting a CRLF immediately followed by a
- single white space character (space, ASCII decimal 32, or horizontal
- tab, ASCII decimal 9). At least one character must be present on the
- folded line. Any sequence of CRLF followed immediately by a single
- white space character is ignored (removed) when processing the
- content type. For example the line:
-
- DESCRIPTION:This is a long description that exists on a long line.
-
- Can be represented as:
-
-
-
-Howes, et. al. Standards Track [Page 6]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- DESCRIPTION:This is a long description
- that exists on a long line.
-
- It could also be represented as:
-
- DESCRIPTION:This is a long descrip
- tion that exists o
- n a long line.
-
- The process of moving from this folded multiple-line representation
- of a type definition to its single line representation is called
- unfolding. Unfolding is accomplished by regarding CRLF immediately
- followed by a white space character (namely HTAB ASCII decimal 9 or
- SPACE ASCII decimal 32) as equivalent to no characters at all (i.e.,
- the CRLF and single white space character are removed).
-
-5.8.2. ABNF content-type definition
-
- The following ABNF uses the notation of RFC 2234, which also defines
- CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT. After the unfolding of
- any folded lines as described above, the syntax for a line of this
- content type is as follows:
-
- contentline = [group "."] name *(";" param) ":" value CRLF
- ; When parsing a content line, folded lines MUST first
- ; be unfolded according to the unfolding procedure
- ; described above.
- ; When generating a content line, lines longer than 75
- ; characters SHOULD be folded according to the folding
- ; procedure described above.
-
- group = 1*(ALPHA / DIGIT / "-")
-
- name = x-name / iana-token
-
- iana-token = 1*(ALPHA / DIGIT / "-")
- ; identifier registered with IANA
-
- x-name = "x-" 1*(ALPHA / DIGIT / "-")
- ; Names that begin with "x-" or "X-" are
- ; reserved for experimental use, not intended for released
- ; products, or for use in bilateral agreements.
-
- param = param-name "=" param-value *("," param-value)
-
- param-name = x-name / iana-token
-
- param-value = ptext / quoted-string
-
-
-
-Howes, et. al. Standards Track [Page 7]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- ptext = *SAFE-CHAR
-
- value = *VALUE-CHAR
- / valuespec ; valuespec defined in section 5.8.4
-
- quoted-string = DQUOTE *QSAFE-CHAR DQUOTE
-
- NON-ASCII = %x80-FF
- ; use restricted by charset parameter
- ; on outer MIME object (UTF-8 preferred)
-
- QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-ASCII
- ; Any character except CTLs, DQUOTE
-
- SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-ASCII
- ; Any character except CTLs, DQUOTE, ";", ":", ","
-
- VALUE-CHAR = WSP / VCHAR / NON-ASCII
- ; any textual character
-
- A line that begins with a white space character is a continuation of
- the previous line, as described above. The white space character and
- immediately preceeding CRLF should be discarded when reconstructing
- the original line. Note that this line-folding convention differs
- from that found in RFC 822, in that the sequence <CRLF><WSP> found
- anywhere in the content indicates a continued line and should be
- removed.
-
- Various type names and the format of the corresponding values are
- defined as specified in Section 11. Specifications MAY impose
- ordering on the type constructs within a body part, though none is
- required by default. The various x-name constructs are used for
- bilaterally-agreed upon type names, parameter names and parameter
- values, or for use in experimental settings.
-
- Type names and parameter names are case insensitive (e.g., the type
- name "fn" is the same as "FN" and "Fn"). Parameter values MAY be case
- sensitive or case insensitive, depending on their definition.
-
- The group construct is used to group related attributes together.
- The group name is a syntactic convention used to indicate that all
- type names prefaced with the same group name SHOULD be grouped
- together when displayed by an application. It has no other
- significance. Implementations that do not understand or support
- grouping MAY simply strip off any text before a "." to the left of
- the type name and present the types and values as normal.
-
-
-
-
-
-Howes, et. al. Standards Track [Page 8]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Each attribute defined in the text/directory body MAY have multiple
- values, if allowed in the definition of the profile in which the
- attribute is used. The general rule for encoding multi-valued items
- is to simply create a new content line for each value (including the
- type name). However, it should be noted that some value types
- support encoding multiple values in a single content line by
- separating the values with a comma ",". This approach has been taken
- for several of the content types defined below (date, time, integer,
- float), for space-saving reasons.
-
-5.8.3. Pre-defined Parameters
-
- The following parameters and value types are defined for general use.
-
- predefined-param = encodingparm
- / valuetypeparm
- / languageparm
- / contextparm
-
- encodingparm = "encoding" "=" encodingtype
-
- encodingtype = "b" ; from RFC 2047
- / iana-token ; registered as described in
- ; section 15 of this document
-
- valuetypeparm = "value" "=" valuetype
-
- valuetype = "uri" ; genericurl from secion 5 of RFC 1738
- / "text"
- / "date"
- / "time"
- / "date-time" ; date time
- / "integer"
- / "boolean"
- / "float"
- / x-name
- / iana-token ; registered as described in
- ; section 15 of this document
-
- languageparm = "language" "=" Language-Tag
- ; Language-Tag is defined in section 2 of RFC 1766
-
- contextparm = "context" "=" context
-
- context = x-name
- / iana-token
-
-
-
-
-
-Howes, et. al. Standards Track [Page 9]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- The "language" type parameter is used to identify data in multiple
- languages. There is no concept of "default" language, except as
- specified by any "Content-Language" MIME header parameter that is
- present. The value of the "language" type parameter is a language
- tag as defined in Section 2 of [RFC-1766].
-
- The "context" type parameter is used to identify a context (e.g., a
- protocol) used in interpreting the value. This is used, for example,
- in the "source" type, defined below.
-
- The "encoding" type parameter is used to specify an alternate
- encoding for a value. If the value contains a CRLF, it must be
- encoded, since CRLF is used to separate lines in the content-type
- itself. Currently, only the "b" encoding is supported.
-
- The "b" encoding can also be useful for binary values that are mixed
- with other text information in the body part (e.g., a certificate).
- Using a per-value "b" encoding in this case leaves the other
- information in a more readable form. The encoded base 64 value can be
- split across multiple physical lines in the content type by using the
- line folding technique described above.
-
- The Content-Transfer-Encoding header field is used to specify the
- encoding used for the body part as a whole. The "encoding" type
- parameter is used to specify an encoding for a particular value
- (e.g., a certificate). In this case, the Content-Transfer-Encoding
- header might specify "8bit", while the one certificate value might
- specify an encoding of "b" via an "encoding=b" type parameter.
-
- The Content-Transfer-Encoding and the encodings of individual types
- given by the "encoding" type parameter are independent of one
- another. When encoding a text/directory body part for transmission,
- individual type encodings are performed first, then the entire body
- part is encoded according to the Content-Transfer-Encoding. When
- decoding a text/directory body part, the Content-Transfer-Encoding is
- decoded first, and then any individual types with an "encoding" type
- parameter are decoded.
-
- The "value" parameter is optional, and is used to identify the value
- type (data type) and format of the value. The use of these
- predefined formats is encouraged even if the value parameter is not
- explicity used. By defining a standard set of value types and their
- formats, existing parsing and processing code can be leveraged.
-
- Including the value type explicitly as part of each property provides
- an extra hint to keep parsing simple and support more generalized
- applications. For example a search engine would not have to know the
- particular value types for all of the items for which it is
-
-
-
-Howes, et. al. Standards Track [Page 10]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- searching. Because the value type is explicit in the definition, the
- search engine could look for dates in any item type and provide
- results that can still be interpreted.
-
-5.8.4. Pre-defined Value Types
-
- The format for values corresponding to the predefined valuetype
- specifications given above are defined.
-
- valuespec = text-list
- / genericurl ; from section 5 of RFC 1738
- / date-list
- / time-list
- / date-time-list
- / boolean
- / integer-list
- / float-list
- / iana-valuespec
-
- text-list = *TEXT-LIST-CHAR *("," *TEXT-LIST-CHAR)
-
- TEXT-LIST-CHAR = "\\" / "\," / "\n"
- / <any VALUE-CHAR except , or \ or newline>
- ; Backslashes, newlines, and commas must be encoded.
- ; \n or \N can be used to encode a newline.
-
- date-list = date *("," date)
-
- time-list = time *("," time)
-
- date-time-list = date "T" time *("," date "T" time)
-
- boolean = "TRUE" / "FALSE"
-
- integer-list = integer *("," integer)
-
- integer = [sign] 1*DIGIT
-
- float-list = float *("," float)
-
- float = [sign] 1*DIGIT ["." 1*DIGIT]
-
- sign = "+" / "-"
-
- date = date-fullyear ["-"] date-month ["-"] date-mday
-
- date-fullyear = 4 DIGIT
-
-
-
-
-Howes, et. al. Standards Track [Page 11]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- date-month = 2 DIGIT ;01-12
-
- date-mday = 2 DIGIT ;01-28, 01-29, 01-30, 01-31
- ;based on month/year
-
- time = time-hour [":"] time-minute [":"] time-second [time-secfrac]
- [time-zone]
-
- time-hour = 2 DIGIT ;00-23
-
- time-minute = 2 DIGIT ;00-59
-
- time-second = 2 DIGIT ;00-60 (leap second)
-
- time-secfrac = "," 1*DIGIT
-
- time-zone = "Z" / time-numzone
-
- time-numzome = sign time-hour [":"] time-minute
-
- iana-valuespec = <a publicly-defined valuetype format, registered
- with IANA, as defined in section 15 of this
- document>
-
- Some specific notes on the value types and formats:
-
- "text": The "text" value type should be used to identify values that
- contain human-readable text. The character set and language in which
- the text is represented is controlled by the charset content-header
- and the language type parameter and content-header.
-
- Examples for "text":
- this is a text value
- this is one value,this is another
- this is a single value\, with a comma encoded
-
- A formatted text line break in a text value type MUST be represented
- as the character sequence backslash (ASCII decimal 92) followed by a
- Latin small letter n (ASCII decimal 110) or a Latin capital letter N
- (ASCII decimal 78), that is "\n" or "\N".
-
- For example a multiple line DESCRIPTION value of:
-
- Mythical Manager
- Hyjinx Software Division
- BabsCo, Inc.
-
- could be represented as:
-
-
-
-Howes, et. al. Standards Track [Page 12]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- DESCRIPTION:Mythical Manager\nHyjinx Software Division\n
- BabsCo\, Inc.\n
-
- demonstrating the \n literal formatted line break technique, the
- CRLF-followed-by-space line folding technique, and the backslash
- escape technique.
-
- "uri": The "uri" value type should be used to identify values that
- are referenced by a URI (including a Content-ID URI), instead of
- encoded in-line. These value references might be used if the value is
- too large, or otherwise undesirable to include directly. The format
- for the URI is as defined in RFC 1738.
-
- Examples for "uri":
- http://www.foobar.com/my/picture.jpg
- ldap://ldap.foobar.com/cn=babs%20jensen
-
- "date", "time", and "date-time": Each of these value types is based
- on a subset of the definitions in ISO 8601 standard. Profiles MAY
- place further restrictions on "date" and "time" values. Multiple
- "date" and "time" values can be specified using the comma-separated
- notation, unless restricted by a profile.
-
- Examples for "date":
- 1985-04-12
- 1996-08-05,1996-11-11
- 19850412
-
- Examples for "time":
- 10:22:00
- 102200
- 10:22:00.33
- 10:22:00.33Z
- 10:22:33,11:22:00
- 10:22:00-08:00
-
- Examples for "date-time":
- 1996-10-22T14:00:00Z
- 1996-08-11T12:34:56Z
- 19960811T123456Z
- 1996-10-22T14:00:00Z,1996-08-11T12:34:56Z
-
- "boolean": The "boolean" value type is used to express boolen values.
- These values are case insensitive.
-
- Examples: TRUE
- false
- True
-
-
-
-Howes, et. al. Standards Track [Page 13]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- "integer": The "integer" value type is used to express signed
- integers in decimal format. If sign is not specified, the value is
- assumed positive "+". Multiple "integer" values can be specified
- using the comma-separated notation, unless restricted by a profile.
-
- Examples: 1234567890
- -1234556790
- +1234556790,432109876
-
- "float": The "float" value type is used to express real numbers. If
- sign is not specified, the value is assumed positive "+". Multiple
- "float" values can be specified using the comma-separated notation,
- unless restricted by a profile.
-
- Examples: 20.30
- 1000000.0000001
- 1.333,3.14
-
-5.9. Applications which use this media type
-
- Applications which use this media type: Various
-
-5.10. Additional information
-
- Additional information: None
-
-5.11. Person & email address to contact for further information
-
- Tim Howes
- Netscape Communications Corp.
- 501 East Middlefield Rd.
- Mountain View, CA 94041
- USA
- howes@netscape.com
- +1 415 937 3419
-
-5.12. Intended usage
-
- Intended usage: COMMON
-
-
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 14]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-5.13. Author/Change controller
-
- Tim Howes
- Netscape Communications Corp.
- 501 East Middlefield Rd.
- Mountain View, CA 94041
- USA
- howes@netscape.com
- +1 415 937 3419
-
- Mark Smith
- Netscape Communications Corp.
- 501 East Middlefield Rd.
- Mountain View, CA 94041
- USA
- mcs@netscape.com
- +1 415 937 3477
-
- Frank Dawson
- Lotus Development Corporation
- 6544 Battleford Drive
- Raleigh, NC 27613-3502
- USA
- frank_dawson@lotus.com
- +1-919-676-9515
-
-6. Predefined Types
-
- The following types are generally useful regardless of the profile
- being carried and are defined below using the text/directory MIME
- type registration template defined in Section 11.1 of this document.
- These types MAY be included in any profile, unless explicitly
- forbidden in the profile definition.
-
-6.1. SOURCE Type Definition
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type SOURCE
-
- Type name: SOURCE
-
- Type purpose: To identify the source of directory information
- contained in the content type.
-
- Type encoding: 8bit
-
- Type valuetype: uri
-
-
-
-
-Howes, et. al. Standards Track [Page 15]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Type special notes: The SOURCE type is used to provide the means by
- which applications knowledgable in the given directory service
- protocol can obtain additional or more up-to-date information from
- the directory service. It contains a URI as defined in [RFC-1738]
- and/or other information referencing the directory entity or entities
- to which the information pertains. When directory information is
- available from more than one source, the sending entity can pick what
- it considers to be the best source, or multiple SOURCE types can be
- included. The interpretation of the value for a SOURCE type can
- depend on the setting of the CONTEXT type parameter. The value of the
- CONTEXT type parameter MUST be compatible with the value of the uri
- prefix.
-
- Type example:
- SOURCE;CONTEXT=LDAP:ldap://ldap.host/cn=Babs%20Jensen,
- %20o=Babsco,%20c=US
-
-6.2. NAME Type Definition
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type NAME
-
- Type name: NAME
-
- Type purpose: To identify the displayable name of the directory
- entity to which information in the content type pertains.
-
- Type encoding: 8bit
-
- Type valuetype: text
-
- Type special notes: The NAME type is used to convey the display name
- of the entity to which the directory information pertains.
-
- Type example:
- NAME:Babs Jensen's Contact Information
-
-6.3. PROFILE Type Definition
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type PROFILE
-
- Type name: PROFILE
-
- Type purpose: To identify the type of directory entity to which
- information in the content type pertains.
-
- Type encoding: 8bit
-
-
-
-Howes, et. al. Standards Track [Page 16]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Type valuetype: A profile name, registered as described in Section 9
- of this document or bilaterally agreed upon as described in Section
- 5.
-
- Type special notes: The PROFILE type is used to convey the type of
- the entity to which the directory information in the rest of the body
- part pertains. It should be the same as the "profile" header
- parameter, if present.
-
- Type example:
- PROFILE:vCard
-
-6.4. BEGIN Type Definition
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type BEGIN
-
- Type name: BEGIN
-
- Type purpose: To denote the beginning of a syntactic entity within a
- text/directory content-type.
-
- Type encoding: 8bit
-
- Type valuetype: text, containing a profile name, registered as
- described in Section 9 of this document or bilaterally-agreed upon as
- described in Section 5.
-
- Type special notes: The BEGIN type is used in conjunction with the
- END type to delimit a profile containing a related set of properties
- within an text/directory content-type. This construct can be used
- instead of or in addition to wrapping separate sets of information
- inside additional MIME headers. It is provided for applications that
- wish to define content that can contain multiple entities within the
- same text/directory content-type or to define content that can be
- identifiable outside of a MIME environment.
-
- Type example:
- BEGIN:VCARD
-
-6.5. END Type Definition
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type END
-
- Type name: END
-
-
-
-
-
-Howes, et. al. Standards Track [Page 17]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Type purpose: To denote the end of a syntactic entity within a
- text/directory content-type.
-
- Type encoding: 8bit
-
- Type valuetype: text, containing a profile name, registered as
- described in Section 9 of this document or bilaterally-agreed upon as
- described in Section 5.
-
- Type special notes: The END type is used in conjunction with the
- BEGIN type to delimit a profile containing a related set of
- properties within an text/directory content-type. This construct can
- be used instead of or in addition to wrapping separate sets of
- information inside additional MIME headers. It is provided for
- applications that wish to define content that can contain multiple
- entities within the same text/directory content-type or to define
- content that can be identifiable outside of a MIME environment.
-
- Type example:
- END: VCARD
-
-7. Use of the multipart/related Content-Type
-
- The multipart/related Content-Type can be used to hold directory
- information comprised of both text and non-text information or
- directory information that already has a natural MIME representation.
- The root body part within the multipart/related body part is
- specified as defined in [RFC-2112] by a "start" parameter, or it is
- the first body part in the absence of such a parameter. The root
- body part must have a Content-Type of "text/directory". This part
- holds inline information and makes reference to subsequent body parts
- holding additional text or non-text directory information via their
- Content-ID URIs as explained in Section 5.
-
- The body parts referred to do not have to be in any particular order,
- except as noted above for the root body part.
-
-8. Examples
-
- The following examples are for illustrative purposes only and are not
- part of the definition.
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 18]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-8.1. Example 1
-
- The first example illustrates simple use of the text/directory
- Content-Type. Note that no "profile" parameter is given, so an
- application may not know what kind of directory entity the
- information applies to. Note also the use of both hypothetical
- official and bilaterally agreed upon types.
-
- From: Whomever@wherever.com
- To: Someone@somewhere.com
- Subject: whatever
- MIME-Version: 1.0
- Message-ID: <id1@host.net>
- Content-Type: text/directory
- Content-ID: <id2@host.com>
-
- cn:Babs Jensen
- cn:Barbara J Jensen
- sn:Jensen
- email:babs@umich.edu
- phone:+1 313 747-4454
- x-id:1234567890
-
-8.2. Example 2
-
- The next example illustrates the use of the Quoted-Printable transfer
- encoding defined in [RFC 2045] to include non-ASCII character in some
- of the information returned, and the use of the optional "name" and
- "source" types. It also illustrates the use of an "encoding" type
- parameter to encode a certificate value in "b". A "vCard" profile
- [MIME- VCARD] is used for the example.
-
-Content-Type: text/directory;
- charset="iso-8859-1";
- profile="vCard"
-Content-ID: <id3@host.com>
-Content-Transfer-Encoding: Quoted-Printable
-
-begin:VCARD
-source:ldap://cn=bjorn%20Jensen, o=university%20of%20Michigan, c=US
-name:Bjorn Jensen
-fn:Bj=F8rn Jensen
-n:Jensen;Bj=F8rn
-email;type=internet:bjorn@umich.edu
-tel;type=work,voice,msg:+1 313 747-4454
-key;type=x509;encoding=B:dGhpcyBjb3VsZCBiZSAKbXkgY2VydGlmaWNhdGUK
-end:VCARD
-
-
-
-
-Howes, et. al. Standards Track [Page 19]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-8.3. Example 3
-
- The next example illustrates the use of multi-valued type parameters,
- the "language" type parameter, the "value" type parameter, folding of
- long lines, the \n encoding for formatted lines, attribute grouping,
- and the inline "b" encoding. A "vCard" profile [MIME-VCARD] is used
- for the example.
-
-Content-Type: text/directory; profile="vcard"; charset=iso-8859-1
-Content-ID: <id3@host.com>
-Content-Transfer-Encoding: Quoted-Printable
-
-begin:vcard
-source:ldap://cn=Meister%20Berger,o=Universitaet%20Goerlitz,c=DE
-name:Meister Berger
-fn:Meister Berger
-n:Berger;Meister
-bday;value=date:1963-09-21
-o:Universit=E6t G=F6rlitz
-title:Mayor
-title;language=de;value=text:Burgermeister
-note:The Mayor of the great city of
- Goerlitz in the great country of Germany.
-email;internet:mb@goerlitz.de
-home.tel;type=fax,voice,msg:+49 3581 123456
-home.label:Hufenshlagel 1234\n
- 02828 Goerlitz\n
- Deutschland
-key;type=X509;encoding=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQ
- AwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zI
- ENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0ZW1zMRwwGgYDVQQD
- ExNyb290Y2EubmV0c2NhcGUuY29tMB4XDTk3MDYwNjE5NDc1OVoXDTk3MTIwMzE5NDc
- 1OVowgYkxCzAJBgNVBAYTAlVTMSYwJAYDVQQKEx1OZXRzY2FwZSBDb21tdW5pY2F0aW
- 9ucyBDb3JwLjEYMBYGA1UEAxMPVGltb3RoeSBBIEhvd2VzMSEwHwYJKoZIhvcNAQkBF
- hJob3dlc0BuZXRzY2FwZS5jb20xFTATBgoJkiaJk/IsZAEBEwVob3dlczBcMA0GCSqG
- SIb3DQEBAQUAA0sAMEgCQQC0JZf6wkg8pLMXHHCUvMfL5H6zjSk4vTTXZpYyrdN2dXc
- oX49LKiOmgeJSzoiFKHtLOIboyludF90CgqcxtwKnAgMBAAGjNjA0MBEGCWCGSAGG+E
- IBAQQEAwIAoDAfBgNVHSMEGDAWgBT84FToB/GV3jr3mcau+hUMbsQukjANBgkqhkiG9
- w0BAQQFAAOBgQBexv7o7mi3PLXadkmNP9LcIPmx93HGp0Kgyx1jIVMyNgsemeAwBM+M
- SlhMfcpbTrONwNjZYW8vJDSoi//yrZlVt9bJbs7MNYZVsyF1unsqaln4/vy6Uawfg8V
- UMk1U7jt8LYpo4YULU7UZHPYVUaSgVttImOHZIKi4hlPXBOhcUQ==
-end:vcard
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 20]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-8.4. Example 4
-
- The final example illustrates the use of the multipart/related
- Content-Type to include non-textual directory data via the "uri"
- encoding to refer to other body parts within the same message, or to
- external values. Note that no "profile" parameter is given, so an
- application may not know what kind of directory entity the
- information applies to. Note also the use of both hypothetical
- official and bilaterally agreed upon types.
-
-Content-Type: multipart/related;
- boundary=woof;
- type="text/directory";
- start="<id5@host.com>"
-Content-ID: <id4@host.com>
-
---woof
-Content-Type: text/directory; charset="iso-8859-1"
-Content-ID: <id5@host.com>
-Content-Transfer-Encoding: Quoted-Printable
-
-source:ldap://cn=Bjorn%20Jensen,o=University%20of%20Michigan,c=US
-cn:Bj=F8rn Jensen
-sn:Jensen
-email:bjorn@umich.edu
-image;value=uri:cid:id6@host.com
-image;value=uri;format=jpeg:ftp://some.host/some/path.jpg
-sound;value=uri:cid:id7@host.com
-phone:+1 313 747-4454
-
---woof
-Content-Type: image/jpeg
-Content-ID: <id6@host.com>
-
-<...image data...>
-
---woof
-Content-Type: message/external-body;
- name="myvoice.au";
- site="myhost.com";
- access-type=ANON-FTP;
- directory="pub/myname";
- mode="image"
-
-Content-Type: audio/basic
-Content-ID: <id7@host.com>
-
---woof--
-
-
-
-Howes, et. al. Standards Track [Page 21]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-9. Registration of new profiles
-
- This section defines procedures by which new profiles are registered
- with the IANA and made available to the Internet community. Note that
- non-IANA profiles can be used by bilateral agreement, provided the
- associated profile names follow the "X-" convention defined above.
-
- The procedures defined here are designed to allow public comment and
- review of new profiles, while posing only a small impediment to the
- definition of new profiles.
-
- Registration of a new profile is accomplished by the following steps.
-
-9.1. Define the profile
-
- A profile is defined by completing the following template.
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME profile XXX
-
- Profile name:
-
- Profile purpose:
-
- Profile types:
-
- Profile special notes (optional):
-
- Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
-
- The explanation of what goes in each field in the template follows.
-
- Profile name: The name of the profile as it will appear in the
- text/directory MIME Content-Type "profile" header parameter, or the
- predefined "profile" type name.
-
- Profile purpose: The purpose of the profile (e.g., to represent
- information about people, printers, documents, etc.). Give a short
- but clear description.
-
- Profile types: The list of types associated with the profile. This
- list of types is to be expected but not required in the profile,
- unless otherwise noted in the profile definition. Other types not
- mentioned in the profile definition MAY also be present. Note that
- any new types referenced by the profile MUST be defined separately as
- described in Section 10.
-
-
-
-
-
-Howes, et. al. Standards Track [Page 22]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Profile special notes: Any special notes about the profile, how it is
- to be used, etc. This section of the template can also be used to
- define an ordering on the types that appear in the Content-Type, if
- such an ordering is required.
-
-9.2. Post the profile definition
-
- The profile description must be posted to the new profile discussion
- list, ietf-mime-direct@imc.org
-
-9.3. Allow a comment period
-
- Discussion on the new profile must be allowed to take place on the
- list for a minimum of two weeks. Consensus must be reached on the
- profile before proceeding to step 4.
-
-9.4. Submit the profile for approval
-
- Once the two-week comment period has elapsed, and the proposer is
- convinced consensus has been reached on the profile, the registration
- application should be submitted to the Profile Reviewer for approval.
- The Profile Reviewer is appointed by the Application Area Directors
- and can either accept or reject the profile registration. An accepted
- registration is passed on by the Profile Reviewer to the IANA for
- inclusion in the official IANA profile registry. The registration may
- be rejected for any of the following reasons. 1) Insufficient comment
- period; 2) Consensus not reached; 3) Technical deficiencies raised on
- the list or elsewhere have not been addressed. The Profile Reviewer's
- decision to reject a profile can be appealed by the proposer to the
- IESG, or the objections raised can be addressed by the proposer and
- the profile resubmitted.
-
-10. Profile Change Control
-
- Existing profiles can be changed using the same process by which they
- were registered.
-
- Define the change
-
- Post the change
-
- Allow a comment period
-
- Submit the changed profile for approval
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 23]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Note that the original author or any other interested party can
- propose a change to an existing profile, but that such changes should
- only be proposed when there are serious omissions or errors in the
- published specification. The Profile Reviewer can object to a change
- if it is not backwards compatible, but is not required to do so.
-
- Profile definitions can never be deleted from the IANA registry, but
- profiles which are no longer believed to be useful can be declared
- OBSOLETE by a change to their "intended use" field.
-
-11. Registration of new types
-
- This section defines procedures by which new types are registered
- with the IANA. Note that non-IANA types can be used by bilateral
- agreement, provided the associated types names follow the "X-"
- convention defined above.
-
- The procedures defined here are designed to allow public comment and
- review of new types, while posing only a small impediment to the
- definition of new types.
-
- Registration of a new type is accomplished by the following steps.
-
-11.1. Define the type
-
- A type is defined by completing the following template.
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type XXX
-
- Type name:
-
- Type purpose:
-
- Type encoding:
-
- Type valuetype:
-
- Type special notes (optional):
-
- Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
-
- The meaning of each field in the template is as follows.
-
- Type name: The name of the type, as it will appear in the body of an
- text/directory MIME Content-Type "type: value" line to the left of
- the colon ":".
-
-
-
-
-Howes, et. al. Standards Track [Page 24]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Type purpose: The purpose of the type (e.g., to represent a name,
- postal address, IP address, etc.). Give a short but clear
- description.
-
- Type encoding: The default encoding a value of the type must have in
- the body of a text/directory MIME Content-Type.
-
- Type valuetype: The format a value of the type must have in the body
- of a text/directory MIME Content-Type. This description must be
- precise and must not violate the general encoding rules defined in
- section 5 of this document.
-
- Type special notes: Any special notes about the type, how it is to be
- used, etc.
-
-11.2. Post the type definition
-
- The type description must be posted to the new type discussion list,
- ietf-mime-direct@imc.org
-
-11.3. Allow a comment period
-
- Discussion on the new type must be allowed to take place on the list
- for a minimum of two weeks. Consensus must be reached on the type
- before proceeding to step 4.
-
-11.4. Submit the type for approval
-
- Once the two-week comment period has elapsed, and the proposer is
- convinced consensus has been reached on the type, the registration
- application should be submitted to the Profile Reviewer for approval.
- The Profile Reviewer is appointed by the Application Area Directors
- and can either accept or reject the type registration. An accepted
- registration is passed on by the Profile Reviewer to the IANA for
- inclusion in the official IANA profile registry. The registration can
- be rejected for any of the following reasons. 1) Insufficient comment
- period; 2) Consensus not reached; 3) Technical deficiencies raised on
- the list or elsewhere have not been addressed. The Profile
- Reviewer's decision to reject a type can be appealed by the proposer
- to the IESG, or the objections raised can be addressed by the
- proposer and the type resubmitted.
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 25]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-12. Type Change Control
-
- Existing types can be changed using the same process by which they
- were registered.
-
- Define the change
-
- Post the change
-
- Allow a comment period
-
- Submit the type for approval
-
- Note that the original author or any other interested party can
- propose a change to an existing type, but that such changes should
- only be proposed when there are serious omissions or errors in the
- published specification. The Profile Reviewer can object to a change
- if it is not backwards compatible, but is not required to do so.
-
- Type definitions can never be deleted from the IANA registry, but
- types which are nolonger believed to be useful can be declared
- OBSOLETE by a change to their "intended use" field.
-
-13. Registration of new parameters
-
- This section defines procedures by which new parameters are
- registered with the IANA and made available to the Internet
- community. Note that non-IANA parameters can be used by bilateral
- agreement, provided the associated parameters names follow the "X-"
- convention defined above.
-
- The procedures defined here are designed to allow public comment and
- review of new parameters, while posing only a small impediment to the
- definition of new parameters.
-
- Registration of a new parameter is accomplished by the following
- steps.
-
-13.1. Define the parameter
-
- A parameter is defined by completing the following template.
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME type parameter XXX
-
- Parameter name:
-
- Parameter purpose:
-
-
-
-Howes, et. al. Standards Track [Page 26]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- Parameter values:
-
- Parameter special notes (optional):
-
- Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
-
- The explanation of what goes in each field in the template follows.
-
- Parameter name: The name of the parameter as it will appear in the
- text/directory MIME Content-Type.
-
- Parameter purpose: The purpose of the parameter (e.g., to represent
- the format of an image, type of a phone number, etc.). Give a short
- but clear description. If defining a general paramemter like "format"
- or "type" keep in mind that other applications might wish to extend
- its use.
-
- Parameter values: The list or description of values associated with
- the parameter.
-
- Parameter special notes: Any special notes about the parameter, how
- it is to be used, etc.
-
-13.2. Post the parameter definition
-
- The parameter description must be posted to the new parameter
- discussion list, ietf-mime-direct@imc.org
-
-13.3. Allow a comment period
-
- Discussion on the new parameter must be allowed to take place on the
- list for a minimum of two weeks. Consensus must be reached on the
- parameter before proceeding to step 4.
-
-13.4. Submit the parameter for approval
-
- Once the two-week comment period has elapsed, and the proposer is
- convinced consensus has been reached on the parameter, the
- registration application should be submitted to the Profile Reviewer
- for approval. The Profile Reviewer is appointed by the Application
- Area Directors and can either accept or reject the parameter
- registration. An accepted registration is passed on by the Profile
- Reviewer to the IANA for inclusion in the official IANA parameter
- registry. The registration can be rejected for any of the following
- reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
- Technical deficiencies raised on the list or elsewhere have not been
- addressed. The Profile Reviewer's decision to reject a profile can be
- appealed by the proposer to the IESG, or the objections raised can be
-
-
-
-Howes, et. al. Standards Track [Page 27]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- addressed by the proposer and the parameter registration resubmitted.
-
-14. Parameter Change Control
-
- Existing parameters can be changed using the same process by which
- they were registered.
-
- Define the change
-
- Post the change
-
- Allow a comment period
-
- Submit the parameter for approval
-
- Note that the original author or any other interested party can
- propose a change to an existing parameter, but that such changes
- should only be proposed when there are serious omissions or errors in
- the published specification. The Profile Reviewer can object to a
- change if it is not backwards compatible, but is not required to do
- so.
-
- Parameter definitions can never be deleted from the IANA registry,
- but parameters which are nolonger believed to be useful can be
- declared OBSOLETE by a change to their "intended use" field.
-
-15. Registration of new value types
-
- This section defines procedures by which new value types are
- registered with the IANA and made available to the Internet
- community. Note that non-IANA value types can be used by bilateral
- agreement, provided the associated value types names follow the "X-"
- convention defined above.
-
- The procedures defined here are designed to allow public comment and
- review of new value types, while posing only a small impediment to
- the definition of new value types.
-
- Registration of a new value types is accomplished by the following
- steps.
-
-15.1. Define the value type
-
- A value type is defined by completing the following template.
-
- To: ietf-mime-direct@imc.org
- Subject: Registration of text/directory MIME value type XXX
-
-
-
-
-Howes, et. al. Standards Track [Page 28]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- value type name:
-
- value type purpose:
-
- value type format:
-
- value type special notes (optional):
-
- Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
-
- The explanation of what goes in each field in the template follows.
-
- value type name: The name of the value type as it will appear in the
- text/directory MIME Content-Type.
-
- value type purpose: The purpose of the value type. Give a short but
- clear description.
-
- value type format: The definition of the format for the value,
- usually using ABNF grammar.
-
- value type special notes: Any special notes about the value type, how
- it is to be used, etc.
-
-15.2. Post the value type definition
-
- The value type description must be posted to the new value type
- discussion list, ietf-mime-direct@imc.org
-
-15.3. Allow a comment period
-
- Discussion on the new value type must be allowed to take place on the
- list for a minimum of two weeks. Consensus must be reached before
- proceeding to step 4.
-
-15.4. Submit the value type for approval
-
- Once the two-week comment period has elapsed, and the proposer is
- convinced consensus has been reached on the value type, the
- registration application should be submitted to the Profile Reviewer
- for approval. The Profile Reviewer is appointed by the Application
- Area Directors and can either accept or reject the value type
- registration. An accepted registration should be passed on by the
- Profile Reviewer to the IANA for inclusion in the official IANA value
- type registry. The registration can be rejected for any of the
- following reasons. 1) Insufficient comment period; 2) Consensus not
- reached; 3) Technical deficiencies raised on the list or elsewhere
- have not been addressed. The Profile Reviewer's decision to reject a
-
-
-
-Howes, et. al. Standards Track [Page 29]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- profile can be appealed by the proposer to the IESG, or the
- objections raised can be addressed by the proposer and the value type
- registration resubmitted.
-
-16. Security Considerations
-
- Internet mail is subject to many well known security attacks,
- including monitoring, replay, and forgery. Care should be taken by
- any directory service in allowing information to leave the scope of
- the service itself, where any access controls can no longer be
- guaranteed. Applications should also take care to display directory
- data in a "safe" environment (e.g., PostScript-valued types).
-
-17. Acknowledgements
-
- The registration procedures defined here were shamelessly lifted from
- the MIME registration RFC.
-
- The many valuable comments contributed by members of the IETF ASID
- working group are gratefully acknowledged, as are the contributions
- of the Versit Consortium. Chris Newman was especially helpful in
- navigating the intricacies of ABNF lore.
-
-18. References
-
- [RFC-1777] Yeong, W., Howes, T., and S. Kille, "Lightweight
- Directory Access Protocol", RFC 1777, March 1995.
-
- [RFC-1778] Howes, T., Kille, S., Yeong, W., and C. Robbins, "The
- String Representation of Standard Attribute Syntaxes",
- RFC 1778, March 1995.
-
- [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", STD 11, RFC 822, August 1982.
-
- [RFC-2045] Borenstein, N., and N. Freed, "Multipurpose Internet
- Mail Extensions (MIME) Part One: Format of Internet
- Message Bodies", RFC 2045, November 1996.
-
- [RFC-2046] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
- Part Two: Media Types", RFC 2046, November 1996.
-
- [RFC-2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) Part Four: Registration
- Procedures", RFC 2048, November 1996.
-
- [RFC-1766] Alvestrand, H., "Tags for the Identification of
- Languages", RFC 1766, March 1995.
-
-
-
-Howes, et. al. Standards Track [Page 30]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
- [RFC-2112] Levinson, E., "The MIME Multipart/Related Content-type",
- RFC 2112, March 1997.
-
- [X500] "Information Processing Systems - Open Systems
- Interconnection - The Directory: Overview of Concepts,
- Models and Services", ISO/IEC JTC 1/SC21, International
- Standard 9594-1, 1988.
-
- [RFC-1835] Deutsch, P., Schoultz, R., Faltstrom, P., and C. Weider,
- "Architecture of the WHOIS++ service", RFC 1835, August
- 1995.
-
- [RFC-1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
- Resource Locators (URL)", RFC 1738, December 1994.
-
- [MIME-VCARD] Dawson, F., and T. Howes, "VCard MIME Directory
- Profile", RFC 2426, September 1998.
-
- [VCARD] Internet Mail Consortium, "vCard - The Electronic
- Business Card", Version 2.1,
- http://www.imc.com/pdi/vcard-21.txt, September, 1996.
-
- [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC-2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 2234, November 1997.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 31]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-19. Authors' Addresses
-
- Tim Howes
- Netscape Communications Corp.
- 501 East Middlefield Rd.
- Mountain View, CA 94041
- USA
-
- Phone: +1.415.937.3419
- EMail: howes@netscape.com
-
-
- Mark Smith
- Netscape Communications Corp.
- 501 East Middlefield Rd.
- Mountain View, CA 94041
- USA
-
- Phone: +1.415.937.3477
- EMail: mcs@netscape.com
-
-
- Frank Dawson
- Lotus Development Corporation
- 6544 Battleford Drive
- Raleigh, NC 27613
- USA
-
- Phone: +1-919-676-9515
- EMail: frank_dawson@lotus.com
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 32]
-
-RFC 2425 MIME Content-Type for Directory Information September 1998
-
-
-20. Full Copyright Statement
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Howes, et. al. Standards Track [Page 33]
-
diff --git a/proto/rfc2426.txt b/proto/rfc2426.txt
@@ -1,2355 +0,0 @@
-
-
-
-
-
-
-Network Working Group F. Dawson
-Request for Comments: 2426 Lotus Development Corporation
-Category: Standards Track T. Howes
- Netscape Communications
- September 1998
-
-
- vCard MIME Directory Profile
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
-Abstract
-
- This memo defines the profile of the MIME Content-Type [MIME-DIR] for
- directory information for a white-pages person object, based on a
- vCard electronic business card. The profile definition is independent
- of any particular directory service or protocol. The profile is
- defined for representing and exchanging a variety of information
- about an individual (e.g., formatted and structured name and delivery
- addresses, email address, multiple telephone numbers, photograph,
- logo, audio clips, etc.). The directory information used by this
- profile is based on the attributes for the person object defined in
- the X.520 and X.521 directory services recommendations. The profile
- also provides the method for including a [VCARD] representation of a
- white-pages directory entry within the MIME Content-Type defined by
- the [MIME-DIR] document.
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
- document are to be interpreted as described in [RFC 2119].
-
-
-
-
-
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 1]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-Table of Contents
-
- Overview.........................................................3
- 1. THE VCARD MIME DIRECTORY PROFILE REGISTRATION.................4
- 2. MIME DIRECTORY FEATURES.......................................5
- 2.1 PREDEFINED TYPE USAGE ......................................5
- 2.1.1 BEGIN and END Type ......................................5
- 2.1.2 NAME Type ...............................................5
- 2.1.3 PROFILE Type ............................................5
- 2.1.4 SOURCE Type .............................................5
- 2.2 PREDEFINED TYPE PARAMETER USAGE ............................6
- 2.3 PREDEFINED VALUE TYPE USAGE ................................6
- 2.4 EXTENSIONS TO THE PREDEFINED VALUE TYPES ...................6
- 2.4.1 BINARY ..................................................6
- 2.4.2 VCARD ...................................................6
- 2.4.3 PHONE-NUMBER ............................................7
- 2.4.4 UTC-OFFSET ..............................................7
- 2.5 STRUCTURED TYPE VALUES .....................................7
- 2.6 LINE DELIMITING AND FOLDING ................................8
- 3. VCARD PROFILE FEATURES........................................8
- 3.1 IDENTIFICATION TYPES .......................................8
- 3.1.1 FN Type Definition ......................................8
- 3.1.2 N Type Definition .......................................9
- 3.1.3 NICKNAME Type Definition ................................9
- 3.1.4 PHOTO Type Definition ..................................10
- 3.1.5 BDAY Type Definition ...................................11
- 3.2 DELIVERY ADDRESSING TYPES .................................11
- 3.2.1 ADR Type Definition ....................................11
- 3.2.2 LABEL Type Definition ..................................13
- 3.3 TELECOMMUNICATIONS ADDRESSING TYPES .......................13
- 3.3.1 TEL Type Definition ....................................14
- 3.3.2 EMAIL Type Definition ..................................15
- 3.3.3 MAILER Type Definition .................................15
- 3.4 GEOGRAPHICAL TYPES ........................................16
- 3.4.1 TZ Type Definition .....................................16
- 3.4.2 GEO Type Definition ....................................16
- 3.5 ORGANIZATIONAL TYPES ......................................17
- 3.5.1 TITLE Type Definition ..................................17
- 3.5.2 ROLE Type Definition ...................................18
- 3.5.3 LOGO Type Definition ...................................18
- 3.5.4 AGENT Type Definition ..................................19
- 3.5.5 ORG Type Definition ....................................20
- 3.6 EXPLANATORY TYPES .........................................20
- 3.6.1 CATEGORIES Type Definition .............................20
- 3.6.2 NOTE Type Definition ...................................21
- 3.6.3 PRODID Type Definition .................................21
- 3.6.4 REV Type Definition ....................................22
- 3.6.5 SORT-STRING Type Definition ............................22
-
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-
- 3.6.6 SOUND Type Definition ..................................23
- 3.6.7 UID Type Definition ....................................24
- 3.6.8 URL Type Definition ....................................25
- 3.6.9 VERSION Type Definition ................................25
- 3.7 SECURITY TYPES ............................................25
- 3.7.1 CLASS Type Definition ..................................26
- 3.7.2 KEY Type Definition ....................................26
- 3.8 EXTENDED TYPES ............................................27
- 4. FORMAL GRAMMAR...............................................27
- 5. DIFFERENCES FROM VCARD V2.1..................................37
- 6. ACKNOWLEDGEMENTS.............................................39
- 7. AUTHORS' ADDRESSES...........................................39
- 8. SECURITY CONSIDERATIONS......................................39
- 9. REFERENCES...................................................40
- 10. FULL COPYRIGHT STATEMENT....................................42
-
-Overview
-
- The [MIME-DIR] document defines a MIME Content-Type for holding
- different kinds of directory information. The directory information
- can be based on any of a number of directory schemas. This document
- defines a [MIME-DIR] usage profile for conveying directory
- information based on one such schema; that of the white-pages type of
- person object.
-
- The schema is based on the attributes for the person object defined
- in the X.520 and X.521 directory services recommendations. The schema
- has augmented the basic attributes defined in the X.500 series
- recommendation in order to provide for an electronic representation
- of the information commonly found on a paper business card. This
- schema was first defined in the [VCARD] document. Hence, this [MIME-
- DIR] profile is referred to as the vCard MIME Directory Profile.
-
- A directory entry based on this usage profile can include traditional
- directory, white-pages information such as the distinguished name
- used to uniquely identify the entry, a formatted representation of
- the name used for user-interface or presentation purposes, both the
- structured and presentation form of the delivery address, various
- telephone numbers and organizational information associated with the
- entry. In addition, traditional paper business card information such
- as an image of an organizational logo or identify photograph can be
- included in this person object.
-
- The vCard MIME Directory Profile also provides support for
- representing other important information about the person associated
- with the directory entry. For instance, the date of birth of the
- person; an audio clip describing the pronunciation of the name
- associated with the directory entry, or some other application of the
-
-
-
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-
-
- digital sound; longitude and latitude geo-positioning information
- related to the person associated with the directory entry; date and
- time that the directory information was last updated; annotations
- often written on a business card; Uniform Resource Locators (URL) for
- a website; public key information. The profile also provides support
- for non-standard extensions to the schema. This provides the
- flexibility for implementations to augment the current capabilities
- of the profile in a standardized way. More information about this
- electronic business card format can be found in [VCARD].
-
-1. The vCard Mime Directory Profile Registration
-
- This profile is identified by the following [MIME-DIR] registration
- template information. Subsequent sections define the profile
- definition.
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME profile VCARD
-
- Profile name: VCARD
-
- Profile purpose: To hold person object or white-pages type of
- directory information. The person schema captured in the directory
- entries is that commonly found in an electronic business card.
-
- Predefined MIME Directory value specifications used: uri, date,
- date-time, float
-
- New value specifications: This profile places further constraints on
- the [MIME-DIR] text value specification. In addition, it adds a
- binary, phone-number, utc-offset and vcard value specifications.
-
- Predefined MIME Directory types used: SOURCE, NAME, PROFILE, BEGIN,
- END.
-
- Predefined MIME Directory parameters used: ENCODING, VALUE, CHARSET,
- LANGUAGE, CONTEXT.
-
- New types: FN, N, NICKNAME, PHOTO, BDAY, ADR, LABEL, TEL, EMAIL,
- MAILER, TZ, GEO, TITLE, ROLE, LOGO, AGENT, ORG, CATEGORIES, NOTE,
- PRODID, REV, SORT-STRING, SOUND, URL, UID, VERSION, CLASS, KEY
-
- New parameters: TYPE
-
- Profile special notes: The vCard object MUST contain the FN, N and
- VERSION types. The type-grouping feature of [MIME-DIR] is supported
- by this profile to group related vCard properties about a directory
-
-
-
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-
-
- entry. For example, vCard properties describing WORK or HOME related
- characteristics can be grouped with a unique group label.
-
- The profile permits the use of non-standard types (i.e., those
- identified with the prefix string "X-") as a flexible method for
- implementations to extend the functionality currently defined within
- this profile.
-
-2. MIME Directory Features
-
- The vCard MIME Directory Profile makes use of many of the features
- defined by [MIME-DIR]. The following sections either clarify or
- extend the content-type definition of [MIME-DIR].
-
-2.1 Predefined Type Usage
-
- The vCard MIME Directory Profile uses the following predefined types
- from [MIME-DIR].
-
-2.1.1 BEGIN and END Type
-
- The content entity MUST begin with the BEGIN type with a value of
- "VCARD". The content entity MUST end with the END type with a value
- of "VCARD".
-
-2.1.2 NAME Type
-
- If the NAME type is present, then its value is the displayable,
- presentation text associated with the source for the vCard, as
- specified in the SOURCE type.
-
-2.1.3 PROFILE Type
-
- If the PROFILE type is present, then its value MUST be "VCARD".
-
-2.1.4 SOURCE Type
-
- If the SOURCE type is present, then its value provides information
- how to find the source for the vCard.
-
-
-
-
-
-
-
-
-
-
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-
-
-2.2 Predefined Type Parameter Usage
-
- The vCard MIME Directory Profile uses the following predefined type
- parameters as defined by [MIME-DIR].
-
- - LANGUAGE
-
- - ENCODING
-
- - VALUE
-
-2.3 Predefined VALUE Type Usage
-
- The predefined data type values specified in [MIME-DIR] MUST NOT be
- repeated in COMMA separated value lists except within the N,
- NICKNAME, ADR and CATEGORIES value types.
-
- The text value type defined in [MIME-DIR] is further restricted such
- that any SEMI-COLON character (ASCII decimal 59) in the value MUST be
- escaped with the BACKSLASH character (ASCII decimal 92).
-
-2.4 Extensions To The Predefined VALUE Types
-
- The predefined data type values specified in [MIME-DIR] have been
- extended by the vCard profile to include a number of value types that
- are specific to this profile.
-
-2.4.1 BINARY
-
- The "binary" value type specifies that the type value is inline,
- encoded binary data. This value type can be specified in the PHOTO,
- LOGO, SOUND, and KEY types.
-
- If inline encoded binary data is specified, the ENCODING type
- parameter MUST be used to specify the encoding format. The binary
- data MUST be encoded using the "B" encoding format. Long lines of
- encoded binary data SHOULD BE folded to 75 characters using the
- folding method defined in [MIME-DIR].
-
- The value type is defined by the following notation:
-
- binary = <A "B" binary encoded string as defined by [RFC 2047].>
-
-2.4.2 VCARD
-
- The "vcard" value type specifies that the type value is another
- vCard. This value type can be specified in the AGENT type. The value
- type is defined by this specification. Since each of the type
-
-
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-
- declarations with in the vcard value type are being specified within
- a text value themselves, they MUST be terminated with the backslash
- escape sequence "\n" or "\N", instead of the normal newline character
- sequence CRLF. In addition, any COMMA character (ASCII decimal 44),
- SEMI-COLON character (ASCII decimal 59) and COLON character (ASCII
- decimal 58) MUST be escaped with the BACKSLASH character (ASCII
- decimal 92). For example, with the AGENT type a value would be
- specified as:
-
- AGENT:BEGIN:VCARD\nFN:Joe Friday\nTEL:+1-919-555-7878\n
- TITLE:Area Administrator\, Assistant\n EMAIL\;TYPE=INTERN\n
- ET:jfriday@host.com\nEND:VCARD\n
-
-2.4.3 PHONE-NUMBER
-
- The "phone-number" value type specifies that the type value is a
- telephone number. This value type can be specified in the TEL type.
- The value type is a text value that has the special semantics of a
- telephone number as defined in [CCITT E.163] and [CCITT X.121].
-
-2.4.4 UTC-OFFSET
-
- The "utc-offset" value type specifies that the type value is a signed
- offset from UTC. This value type can be specified in the TZ type.
-
- The value type is an offset from Coordinated Universal Time (UTC). It
- is specified as a positive or negative difference in units of hours
- and minutes (e.g., +hh:mm). The time is specified as a 24-hour clock.
- Hour values are from 00 to 23, and minute values are from 00 to 59.
- Hour and minutes are 2-digits with high order zeroes required to
- maintain digit count. The extended format for ISO 8601 UTC offsets
- MUST be used. The extended format makes use of a colon character as a
- separator of the hour and minute text fields.
-
- The value is defined by the following notation:
-
- time-hour = 2DIGIT ;00-23
- time-minute = 2DIGIT ;00-59
- utc-offset = ("+" / "-") time-hour ":" time-minute
-
-2.5 Structured Type Values
-
- Compound type values are delimited by a field delimiter, specified by
- the SEMI-COLON character (ASCII decimal 59). A SEMI-COLON in a
- component of a compound property value MUST be escaped with a
- BACKSLASH character (ASCII decimal 92).
-
-
-
-
-
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-
-
- Lists of values are delimited by a list delimiter, specified by the
- COMMA character (ASCII decimal 44). A COMMA character in a value MUST
- be escaped with a BACKSLASH character (ASCII decimal 92).
-
- This profile supports the type grouping mechanism defined in [MIME-
- DIR]. Grouping of related types is a useful technique to communicate
- common semantics concerning the properties of a vCard.
-
-2.6 Line Delimiting and Folding
-
- This profile supports the same line delimiting and folding methods
- defined in [MIME-DIR]. Specifically, when parsing a content line,
- folded lines must first be unfolded according to the unfolding
- procedure described in [MIME-DIR]. After generating a content line,
- lines longer than 75 characters SHOULD be folded according to the
- folding procedure described in [MIME DIR].
-
- Folding is done after any content encoding of a type value. Unfolding
- is done before any decoding of a type value in a content line.
-
-3. vCard Profile Features
-
- The vCard MIME Directory Profile Type contains directory information,
- typically pertaining to a single directory entry. The information is
- described using an attribute schema that is tailored for capturing
- personal contact information. The vCard can include attributes that
- describe identification, delivery addressing, telecommunications
- addressing, geographical, organizational, general explanatory and
- security and access information about the particular object
- associated with the vCard.
-
-3.1 Identification Types
-
- These types are used in the vCard profile to capture information
- associated with the identification and naming of the person or
- resource associated with the vCard.
-
-3.1.1 FN Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type FN
-
- Type name:FN
-
- Type purpose: To specify the formatted text corresponding to the name
- of the object the vCard represents.
-
-
-
-
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-
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: This type is based on the semantics of the X.520
- Common Name attribute. The property MUST be present in the vCard
- object.
-
- Type example:
-
- FN:Mr. John Q. Public\, Esq.
-
-3.1.2 N Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type N
-
- Type name: N
-
- Type purpose: To specify the components of the name of the object the
- vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single structured text value. Each component can have
- multiple values.
-
- Type special note: The structured type value corresponds, in
- sequence, to the Family Name, Given Name, Additional Names, Honorific
- Prefixes, and Honorific Suffixes. The text components are separated
- by the SEMI-COLON character (ASCII decimal 59). Individual text
- components can include multiple text values (e.g., multiple
- Additional Names) separated by the COMMA character (ASCII decimal
- 44). This type is based on the semantics of the X.520 individual name
- attributes. The property MUST be present in the vCard object.
-
- Type example:
-
- N:Public;John;Quinlan;Mr.;Esq.
-
- N:Stevenson;John;Philip,Paul;Dr.;Jr.,M.D.,A.C.P.
-
-3.1.3 NICKNAME Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type NICKNAME
-
-
-
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-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type name: NICKNAME
-
- Type purpose: To specify the text corresponding to the nickname of
- the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: One or more text values separated by a COMMA character
- (ASCII decimal 44).
-
- Type special note: The nickname is the descriptive name given instead
- of or in addition to the one belonging to a person, place, or thing.
- It can also be used to specify a familiar form of a proper name
- specified by the FN or N types.
-
- Type example:
-
- NICKNAME:Robbie
-
- NICKNAME:Jim,Jimmie
-
-3.1.4 PHOTO Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type PHOTO
-
- Type name: PHOTO
-
- Type purpose: To specify an image or photograph information that
- annotates some aspect of the object the vCard represents.
-
- Type encoding: The encoding MUST be reset to "b" using the ENCODING
- parameter in order to specify inline, encoded binary data. If the
- value is referenced by a URI value, then the default encoding of 8bit
- is used and no explicit ENCODING parameter is needed.
-
- Type value: A single value. The default is binary value. It can also
- be reset to uri value. The uri value can be used to specify a value
- outside of this MIME entity.
-
- Type special notes: The type can include the type parameter "TYPE" to
- specify the graphic image format type. The TYPE parameter values MUST
- be one of the IANA registered image formats or a non-standard image
- format.
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 10]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type example:
-
- PHOTO;VALUE=uri:http://www.abc.com/pub/photos
- /jqpublic.gif
-
-
- PHOTO;ENCODING=b;TYPE=JPEG:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
- AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
- ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
- <...remainder of "B" encoded binary data...>
-
-3.1.5 BDAY Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type BDAY
-
- Type name: BDAY
-
- Type purpose: To specify the birth date of the object the vCard
- represents.
-
- Type encoding: 8bit
-
- Type value: The default is a single date value. It can also be reset
- to a single date-time value.
-
- Type examples:
-
- BDAY:1996-04-15
-
- BDAY:1953-10-15T23:10:00Z
-
- BDAY:1987-09-27T08:30:00-06:00
-
-3.2 Delivery Addressing Types
-
- These types are concerned with information related to the delivery
- addressing or label for the vCard object.
-
-3.2.1 ADR Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type ADR
-
- Type name: ADR
-
-
-
-
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-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type purpose: To specify the components of the delivery address for
- the vCard object.
-
- Type encoding: 8bit
-
- Type value: A single structured text value, separated by the
- SEMI-COLON character (ASCII decimal 59).
-
- Type special notes: The structured type value consists of a sequence
- of address components. The component values MUST be specified in
- their corresponding position. The structured type value corresponds,
- in sequence, to the post office box; the extended address; the street
- address; the locality (e.g., city); the region (e.g., state or
- province); the postal code; the country name. When a component value
- is missing, the associated component separator MUST still be
- specified.
-
- The text components are separated by the SEMI-COLON character (ASCII
- decimal 59). Where it makes semantic sense, individual text
- components can include multiple text values (e.g., a "street"
- component with multiple lines) separated by the COMMA character
- (ASCII decimal 44).
-
- The type can include the type parameter "TYPE" to specify the
- delivery address type. The TYPE parameter values can include "dom" to
- indicate a domestic delivery address; "intl" to indicate an
- international delivery address; "postal" to indicate a postal
- delivery address; "parcel" to indicate a parcel delivery address;
- "home" to indicate a delivery address for a residence; "work" to
- indicate delivery address for a place of work; and "pref" to indicate
- the preferred delivery address when more than one address is
- specified. These type parameter values can be specified as a
- parameter list (i.e., "TYPE=dom;TYPE=postal") or as a value list
- (i.e., "TYPE=dom,postal"). This type is based on semantics of the
- X.520 geographical and postal addressing attributes. The default is
- "TYPE=intl,postal,parcel,work". The default can be overridden to some
- other set of values by specifying one or more alternate values. For
- example, the default can be reset to "TYPE=dom,postal,work,home" to
- specify a domestic delivery address for postal delivery to a
- residence that is also used for work.
-
- Type example: In this example the post office box and the extended
- address are absent.
-
- ADR;TYPE=dom,home,postal,parcel:;;123 Main
- Street;Any Town;CA;91921-1234
-
-
-
-
-
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-
-
-3.2.2 LABEL Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type LABEL
-
- Type name: LABEL
-
- Type purpose: To specify the formatted text corresponding to delivery
- address of the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: The type value is formatted text that can be used
- to present a delivery address label for the vCard object. The type
- can include the type parameter "TYPE" to specify delivery label type.
- The TYPE parameter values can include "dom" to indicate a domestic
- delivery label; "intl" to indicate an international delivery label;
- "postal" to indicate a postal delivery label; "parcel" to indicate a
- parcel delivery label; "home" to indicate a delivery label for a
- residence; "work" to indicate delivery label for a place of work; and
- "pref" to indicate the preferred delivery label when more than one
- label is specified. These type parameter values can be specified as a
- parameter list (i.e., "TYPE=dom;TYPE=postal") or as a value list
- (i.e., "TYPE=dom,postal"). This type is based on semantics of the
- X.520 geographical and postal addressing attributes. The default is
- "TYPE=intl,postal,parcel,work". The default can be overridden to some
- other set of values by specifying one or more alternate values. For
- example, the default can be reset to "TYPE=intl,post,parcel,home" to
- specify an international delivery label for both postal and parcel
- delivery to a residential location.
-
- Type example: A multi-line address label.
-
- LABEL;TYPE=dom,home,postal,parcel:Mr.John Q. Public\, Esq.\n
- Mail Drop: TNE QB\n123 Main Street\nAny Town\, CA 91921-1234
- \nU.S.A.
-
-3.3 Telecommunications Addressing Types
-
- These types are concerned with information associated with the
- telecommunications addressing of the object the vCard represents.
-
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 13]
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-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-3.3.1 TEL Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type TEL
-
- Type name: TEL
-
- Type purpose: To specify the telephone number for telephony
- communication with the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single phone-number value.
-
- Type special notes: The value of this type is specified in a
- canonical form in order to specify an unambiguous representation of
- the globally unique telephone endpoint. This type is based on the
- X.500 Telephone Number attribute.
-
- The type can include the type parameter "TYPE" to specify intended
- use for the telephone number. The TYPE parameter values can include:
- "home" to indicate a telephone number associated with a residence,
- "msg" to indicate the telephone number has voice messaging support,
- "work" to indicate a telephone number associated with a place of
- work, "pref" to indicate a preferred-use telephone number, "voice" to
- indicate a voice telephone number, "fax" to indicate a facsimile
- telephone number, "cell" to indicate a cellular telephone number,
- "video" to indicate a video conferencing telephone number, "pager" to
- indicate a paging device telephone number, "bbs" to indicate a
- bulletin board system telephone number, "modem" to indicate a MODEM
- connected telephone number, "car" to indicate a car-phone telephone
- number, "isdn" to indicate an ISDN service telephone number, "pcs" to
- indicate a personal communication services telephone number. The
- default type is "voice". These type parameter values can be specified
- as a parameter list (i.e., "TYPE=work;TYPE=voice") or as a value list
- (i.e., "TYPE=work,voice"). The default can be overridden to another
- set of values by specifying one or more alternate values. For
- example, the default TYPE of "voice" can be reset to a WORK and HOME,
- VOICE and FAX telephone number by the value list
- "TYPE=work,home,voice,fax".
-
- Type example:
-
- TEL;TYPE=work,voice,pref,msg:+1-213-555-1234
-
-
-
-
-
-
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-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-3.3.2 EMAIL Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type EMAIL
-
- Type name: EMAIL
-
- Type purpose: To specify the electronic mail address for
- communication with the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: The type can include the type parameter "TYPE" to
- specify the format or preference of the electronic mail address. The
- TYPE parameter values can include: "internet" to indicate an Internet
- addressing type, "x400" to indicate a X.400 addressing type or "pref"
- to indicate a preferred-use email address when more than one is
- specified. Another IANA registered address type can also be
- specified. The default email type is "internet". A non-standard value
- can also be specified.
-
- Type example:
-
- EMAIL;TYPE=internet:jqpublic@xyz.dom1.com
-
- EMAIL;TYPE=internet:jdoe@isp.net
-
- EMAIL;TYPE=internet,pref:jane_doe@abc.com
-
-3.3.3 MAILER Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type MAILER
-
- Type name: MAILER
-
- Type purpose: To specify the type of electronic mail software that is
- used by the individual associated with the vCard.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
-
-
-
-
-Dawson & Howes Standards Track [Page 15]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type special notes: This information can provide assistance to a
- correspondent regarding the type of data representation which can be
- used, and how they can be packaged. This property is based on the
- private MIME type X-Mailer that is generally implemented by MIME user
- agent products.
-
- Type example:
-
- MAILER:PigeonMail 2.1
-
-3.4 Geographical Types
-
- These types are concerned with information associated with
- geographical positions or regions associated with the object the
- vCard represents.
-
-3.4.1 TZ Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type TZ
-
- Type name: TZ
-
- Type purpose: To specify information related to the time zone of the
- object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: The default is a single utc-offset value. It can also be
- reset to a single text value.
-
- Type special notes: The type value consists of a single value.
-
- Type examples:
-
- TZ:-05:00
-
- TZ;VALUE=text:-05:00; EST; Raleigh/North America
- ;This example has a single value, not a structure text value.
-
-3.4.2 GEO Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type GEO
-
- Type name: GEO
-
-
-
-Dawson & Howes Standards Track [Page 16]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type purpose: To specify information related to the global
- positioning of the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single structured value consisting of two float values
- separated by the SEMI-COLON character (ASCII decimal 59).
-
- Type special notes: This type specifies information related to the
- global position of the object associated with the vCard. The value
- specifies latitude and longitude, in that order (i.e., "LAT LON"
- ordering). The longitude represents the location east and west of the
- prime meridian as a positive or negative real number, respectively.
- The latitude represents the location north and south of the equator
- as a positive or negative real number, respectively. The longitude
- and latitude values MUST be specified as decimal degrees and should
- be specified to six decimal places. This will allow for granularity
- within a meter of the geographical position. The text components are
- separated by the SEMI-COLON character (ASCII decimal 59). The simple
- formula for converting degrees-minutes-seconds into decimal degrees
- is:
-
- decimal = degrees + minutes/60 + seconds/3600.
-
- Type example:
-
- GEO:37.386013;-122.082932
-
-3.5 Organizational Types
-
- These types are concerned with information associated with
- characteristics of the organization or organizational units of the
- object the vCard represents.
-
-3.5.1 TITLE Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type TITLE
-
- Type name: TITLE
-
- Type purpose: To specify the job title, functional position or
- function of the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
-
-
-Dawson & Howes Standards Track [Page 17]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type special notes: This type is based on the X.520 Title attribute.
-
- Type example:
-
- TITLE:Director\, Research and Development
-
-3.5.2 ROLE Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type ROLE
-
- Type name: ROLE
-
- Type purpose: To specify information concerning the role, occupation,
- or business category of the object the vCard represents.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: This type is based on the X.520 Business Category
- explanatory attribute. This property is included as an organizational
- type to avoid confusion with the semantics of the TITLE type and
- incorrect usage of that type when the semantics of this type is
- intended.
-
- Type example:
-
- ROLE:Programmer
-
-3.5.3 LOGO Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type LOGO
-
- Type name: LOGO
-
- Type purpose: To specify a graphic image of a logo associated with
- the object the vCard represents.
-
- Type encoding: The encoding MUST be reset to "b" using the ENCODING
- parameter in order to specify inline, encoded binary data. If the
- value is referenced by a URI value, then the default encoding of 8bit
- is used and no explicit ENCODING parameter is needed.
-
-
-
-
-
-Dawson & Howes Standards Track [Page 18]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type value: A single value. The default is binary value. It can also
- be reset to uri value. The uri value can be used to specify a value
- outside of this MIME entity.
-
- Type special notes: The type can include the type parameter "TYPE" to
- specify the graphic image format type. The TYPE parameter values MUST
- be one of the IANA registered image formats or a non-standard image
- format.
-
- Type example:
-
- LOGO;VALUE=uri:http://www.abc.com/pub/logos/abccorp.jpg
-
- LOGO;ENCODING=b;TYPE=JPEG:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
- AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
- ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
- <...the remainder of "B" encoded binary data...>
-
-3.5.4 AGENT Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type AGENT
-
- Type name: AGENT
-
- Type purpose: To specify information about another person who will
- act on behalf of the individual or resource associated with the
- vCard.
-
- Type encoding: 8-bit
-
- Type value: The default is a single vcard value. It can also be reset
- to either a single text or uri value. The text value can be used to
- specify textual information. The uri value can be used to specify
- information outside of this MIME entity.
-
- Type special notes: This type typically is used to specify an area
- administrator, assistant, or secretary for the individual associated
- with the vCard. A key characteristic of the Agent type is that it
- represents somebody or something that is separately addressable.
-
- Type example:
-
- AGENT;VALUE=uri:
- CID:JQPUBLIC.part3.960129T083020.xyzMail@host3.com
-
-
-
-
-
-Dawson & Howes Standards Track [Page 19]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- AGENT:BEGIN:VCARD\nFN:Susan Thomas\nTEL:+1-919-555-
- 1234\nEMAIL\;INTERNET:sthomas@host.com\nEND:VCARD\n
-
-3.5.5 ORG Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type ORG
-
- Type name: ORG
-
- Type purpose: To specify the organizational name and units associated
- with the vCard.
-
- Type encoding: 8bit
-
- Type value: A single structured text value consisting of components
- separated the SEMI-COLON character (ASCII decimal 59).
-
- Type special notes: The type is based on the X.520 Organization Name
- and Organization Unit attributes. The type value is a structured type
- consisting of the organization name, followed by one or more levels
- of organizational unit names.
-
- Type example: A type value consisting of an organizational name,
- organizational unit #1 name and organizational unit #2 name.
-
- ORG:ABC\, Inc.;North American Division;Marketing
-
-3.6 Explanatory Types
-
- These types are concerned with additional explanations, such as that
- related to informational notes or revisions specific to the vCard.
-
-3.6.1 CATEGORIES Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type CATEGORIES
-
- Type name: CATEGORIES
-
- Type purpose: To specify application category information about the
- vCard.
-
- Type encoding: 8bit
-
-
-
-
-
-Dawson & Howes Standards Track [Page 20]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type value: One or more text values separated by a COMMA character
- (ASCII decimal 44).
-
- Type example:
-
- CATEGORIES:TRAVEL AGENT
-
- CATEGORIES:INTERNET,IETF,INDUSTRY,INFORMATION TECHNOLOGY
-
-3.6.2 NOTE Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type NOTE
-
- Type name: NOTE
-
- Type purpose: To specify supplemental information or a comment that
- is associated with the vCard.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: The type is based on the X.520 Description
- attribute.
-
- Type example:
-
- NOTE:This fax number is operational 0800 to 1715
- EST\, Mon-Fri.
-
-3.6.3 PRODID Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type PRODID
-
- Type name: PRODID
-
- Type purpose: To specify the identifier for the product that created
- the vCard object.
-
- Type encoding: 8-bit
-
- Type value: A single text value.
-
-
-
-
-
-Dawson & Howes Standards Track [Page 21]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type special notes: Implementations SHOULD use a method such as that
- specified for Formal Public Identifiers in ISO 9070 to assure that
- the text value is unique.
-
- Type example:
-
- PRODID:-//ONLINE DIRECTORY//NONSGML Version 1//EN
-
-3.6.4 REV Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type REV
-
- Type name: REV
-
- Type purpose: To specify revision information about the current
- vCard.
-
- Type encoding: 8-bit
-
- Type value: The default is a single date-time value. Can also be
- reset to a single date value.
-
- Type special notes: The value distinguishes the current revision of
- the information in this vCard for other renditions of the
- information.
-
- Type example:
-
- REV:1995-10-31T22:27:10Z
-
- REV:1997-11-15
-
-3.6.5 SORT-STRING Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type SORT-STRING
-
- Type Name: SORT-STRING
-
- Type purpose: To specify the family name or given name text to be
- used for national-language-specific sorting of the FN and N types.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
-
-
-Dawson & Howes Standards Track [Page 22]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type special notes: The sort string is used to provide family name or
- given name text that is to be used in locale- or national-language-
- specific sorting of the formatted name and structured name types.
- Without this information, sorting algorithms could incorrectly sort
- this vCard within a sequence of sorted vCards. When this type is
- present in a vCard, then this family name or given name value is used
- for sorting the vCard.
-
- Type examples: For the case of family name sorting, the following
- examples define common sort string usage with the FN and N types.
-
- FN:Rene van der Harten
- N:van der Harten;Rene;J.;Sir;R.D.O.N.
- SORT-STRING:Harten
-
- FN:Robert Pau Shou Chang
- N:Pau;Shou Chang;Robert
- SORT-STRING:Pau
-
- FN:Osamu Koura
- N:Koura;Osamu
- SORT-STRING:Koura
-
- FN:Oscar del Pozo
- N:del Pozo Triscon;Oscar
- SORT-STRING:Pozo
-
- FN:Chistine d'Aboville
- N:d'Aboville;Christine
- SORT-STRING:Aboville
-
-3.6.6 SOUND Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type SOUND
-
- Type name: SOUND
-
- Type purpose: To specify a digital sound content information that
- annotates some aspect of the vCard. By default this type is used to
- specify the proper pronunciation of the name type value of the vCard.
-
- Type encoding: The encoding MUST be reset to "b" using the ENCODING
- parameter in order to specify inline, encoded binary data. If the
- value is referenced by a URI value, then the default encoding of 8bit
- is used and no explicit ENCODING parameter is needed.
-
-
-
-
-Dawson & Howes Standards Track [Page 23]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type value: A single value. The default is binary value. It can also
- be reset to uri value. The uri value can be used to specify a value
- outside of this MIME entity.
-
- Type special notes: The type can include the type parameter "TYPE" to
- specify the audio format type. The TYPE parameter values MUST be one
- of the IANA registered audio formats or a non-standard audio format.
-
- Type example:
-
- SOUND;TYPE=BASIC;VALUE=uri:CID:JOHNQPUBLIC.part8.
- 19960229T080000.xyzMail@host1.com
-
- SOUND;TYPE=BASIC;ENCODING=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
- AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
- ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
- <...the remainder of "B" encoded binary data...>
-
-3.6.7 UID Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type UID
-
- Type name: UID
-
- Type purpose: To specify a value that represents a globally unique
- identifier corresponding to the individual or resource associated
- with the vCard.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: The type is used to uniquely identify the object
- that the vCard represents.
-
- The type can include the type parameter "TYPE" to specify the format
- of the identifier. The TYPE parameter value should be an IANA
- registered identifier format. The value can also be a non-standard
- format.
-
- Type example:
-
- UID:19950401-080045-40000F192713-0052
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 24]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-3.6.8 URL Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type URL
-
- Type name: URL
-
- Type purpose: To specify a uniform resource locator associated with
- the object that the vCard refers to.
-
- Type encoding: 8bit
-
- Type value: A single uri value.
-
- Type example:
-
- URL:http://www.swbyps.restaurant.french/~chezchic.html
-
-3.6.9 VERSION Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type VERSION
-
- Type name: VERSION
-
- Type purpose: To specify the version of the vCard specification used
- to format this vCard.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: The property MUST be present in the vCard object.
- The value MUST be "3.0" if the vCard corresponds to this
- specification.
-
- Type example:
-
- VERSION:3.0
-
-3.7 Security Types
-
- These types are concerned with the security of communication pathways
- or access to the vCard.
-
-
-
-
-
-Dawson & Howes Standards Track [Page 25]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-3.7.1 CLASS Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type CLASS
-
- Type name: CLASS
-
- Type purpose: To specify the access classification for a vCard
- object.
-
- Type encoding: 8bit
-
- Type value: A single text value.
-
- Type special notes: An access classification is only one component of
- the general security model for a directory service. The
- classification attribute provides a method of capturing the intent of
- the owner for general access to information described by the vCard
- object.
-
- Type examples:
-
- CLASS:PUBLIC
-
- CLASS:PRIVATE
-
- CLASS:CONFIDENTIAL
-
-3.7.2 KEY Type Definition
-
- To: ietf-mime-directory@imc.org
-
- Subject: Registration of text/directory MIME type KEY
-
- Type name: KEY
-
- Type purpose: To specify a public key or authentication certificate
- associated with the object that the vCard represents.
-
- Type encoding: The encoding MUST be reset to "b" using the ENCODING
- parameter in order to specify inline, encoded binary data. If the
- value is a text value, then the default encoding of 8bit is used and
- no explicit ENCODING parameter is needed.
-
- Type value: A single value. The default is binary. It can also be
- reset to text value. The text value can be used to specify a text
- key.
-
-
-
-Dawson & Howes Standards Track [Page 26]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- Type special notes: The type can also include the type parameter TYPE
- to specify the public key or authentication certificate format. The
- parameter type should specify an IANA registered public key or
- authentication certificate format. The parameter type can also
- specify a non-standard format.
-
- Type example:
-
- KEY;ENCODING=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQA
- wdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENbW11bmljYX
- Rpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
- ZW1zMRwwGgYDVQQDExNyb290Y2EubmV0c2NhcGUuY29tMB4XDTk3MDYwNj
- E5NDc1OVoXDTk3MTIwMzE5NDc1OVowgYkxCzAJBgNVBAYTAlVTMSYwJAYD
- VQQKEx1OZXRzY2FwZSBDb21tdW5pY2F0aW9ucyBDb3JwLjEYMBYGA1UEAx
- MPVGltb3RoeSBBIEhvd2VzMSEwHwYJKoZIhvcNAQkBFhJob3dlc0BuZXRz
- Y2FwZS5jb20xFTATBgoJkiaJk/IsZAEBEwVob3dlczBcMA0GCSqGSIb3DQ
- EBAQUAA0sAMEgCQQC0JZf6wkg8pLMXHHCUvMfL5H6zjSk4vTTXZpYyrdN2
- dXcoX49LKiOmgeJSzoiFKHtLOIboyludF90CgqcxtwKnAgMBAAGjNjA0MB
- EGCWCGSAGG+EIBAQQEAwIAoDAfBgNVHSMEGDAWgBT84FToB/GV3jr3mcau
- +hUMbsQukjANBgkqhkiG9w0BAQQFAAOBgQBexv7o7mi3PLXadkmNP9LcIP
- mx93HGp0Kgyx1jIVMyNgsemeAwBM+MSlhMfcpbTrONwNjZYW8vJDSoi//y
- rZlVt9bJbs7MNYZVsyF1unsqaln4/vy6Uawfg8VUMk1U7jt8LYpo4YULU7
- UZHPYVUaSgVttImOHZIKi4hlPXBOhcUQ==
-
-3.8 Extended Types
-
- The types defined by this document can be extended with private types
- using the non-standard, private values mechanism defined in [RFC
- 2045]. Non-standard, private types with a name starting with "X-" may
- be defined bilaterally between two cooperating agents without outside
- registration or standardization.
-
-4. Formal Grammar
-
- The following formal grammar is provided to assist developers in
- building parsers for the vCard.
-
- This syntax is written according to the form described in RFC 2234,
- but it references just this small subset of RFC 2234 literals:
-
- ;*******************************************
- ; Commonly Used Literal Definition
- ;*******************************************
-
- ALPHA = %x41-5A / %x61-7A
- ; Latin Capital Letter A-Latin Capital Letter Z /
- ; Latin Small Letter a-Latin Small Letter z
-
-
-
-
-Dawson & Howes Standards Track [Page 27]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- CHAR = %x01-7F
- ; Any C0 Controls and Basic Latin, excluding NULL from
- ; Code Charts, pages 7-6 through 7-9 in [UNICODE]
-
- CR = %x0D
- ; Carriage Return
-
- LF = %0A
- ; Line Feed
-
- CRLF = CR LF
- ; Internet standard newline
-
- ;CTL = %x00-1F / %x7F
- ; Controls. Not used, but referenced in comments.
-
- DIGIT = %x30-39
- ; Digit Zero-Digit Nine
-
- DQUOTE = %x22
- ; Quotation Mark
-
- HTAB = %x09
- ; Horizontal Tabulation
-
- SP = %x20
- ; space
-
- VCHAR = %x21-7E
- ; Visible (printing) characters
-
- WSP = SP / HTAB
- ; White Space
-
- ;*******************************************
- ; Basic vCard Definition
- ;*******************************************
-
- vcard_entity = 1*(vcard)
-
- vcard = [group "."] "BEGIN" ":" "VCARD" 1*CRLF
- 1*(contentline)
- ;A vCard object MUST include the VERSION, FN and N types.
- [group "."] "END" ":" "VCARD" 1*CRLF
-
- contentline = [group "."] name *(";" param ) ":" value CRLF
- ; When parsing a content line, folded lines must first
- ; be unfolded according to the unfolding procedure
-
-
-
-Dawson & Howes Standards Track [Page 28]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- ; described above. When generating a content line, lines
- ; longer than 75 characters SHOULD be folded according to
- ; the folding procedure described in [MIME DIR].
-
- group = 1*(ALPHA / DIGIT / "-")
-
- name = iana-token / x-name
- ; Parsing of the param and value is
- ; based on the "name" or type identifier
- ; as defined in ABNF sections below
-
- iana-token = 1*(ALPHA / DIGIT / "-")
- ; vCard type or parameter identifier registered with IANA
-
- x-name = "X-" 1*(ALPHA / DIGIT / "-")
- ; Reserved for non-standard use
-
- param = param-name "=" param-value *("," param-value)
-
- param-name = iana-token / x-name
-
- param-value = ptext / quoted-string
-
- ptext = *SAFE-CHAR
-
- value = *VALUE-CHAR
-
- quoted-string = DQUOTE QSAFE-CHAR DQUOTE
-
- NON-ASCII = %x80-FF
- ; Use is restricted by CHARSET parameter
- ; on outer MIME object (UTF-8 preferred)
-
- QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-ASCII
- ; Any character except CTLs, DQUOTE
-
- SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-ASCII
- ; Any character except CTLs, DQUOTE, ";", ":", ","
-
- VALUE-CHAR = WSP / VCHAR / NON-ASCII
- ; Any textual character
-
- ;*******************************************
- ; vCard Type Definition
- ;
- ; Provides type-specific definitions for how the
- ; "value" and "param" are defined.
- ;*******************************************
-
-
-
-Dawson & Howes Standards Track [Page 29]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- ;For name="NAME"
- param = ""
- ; No parameters allowed
-
- value = text-value
-
- ;For name="PROFILE"
- param = ""
- ; No parameters allowed
-
- value = text-value
- ; Value MUST be the case insensitive value "VCARD
-
- ;For name="SOURCE"
- param = source-param
- ; No parameters allowed
-
- value = uri
-
- source-param = ("VALUE" "=" "uri")
- / ("CONTEXT" "=" "word")
- ; Parameter value specifies the protocol context
- ; for the uri value.
- / (x-name "=" *SAFE-CHAR)
-
- ;For name="FN"
- ;This type MUST be included in a vCard object.
- param = text-param
- ; Text parameters allowed
-
- value = text-value
-
- ;For name="N"
- ;This type MUST be included in a vCard object.
-
- param = text-param
- ; Text parameters allowed
-
- value = n-value
-
- n-value = 0*4(text-value *("," text-value) ";")
- text-value *("," text-value)
- ; Family; Given; Middle; Prefix; Suffix.
- ; Example: Public;John;Quincy,Adams;Reverend Dr. III
-
- ;For name="NICKNAME"
- param = text-param
- ; Text parameters allowed
-
-
-
-Dawson & Howes Standards Track [Page 30]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- value = text-list
-
- ;For name="PHOTO"
- param = img-inline-param
- ; Only image parameters allowed
-
- param =/ img-refer-param
- ; Only image parameters allowed
-
- value = img-inline-value
- ; Value and parameter MUST match
-
- value =/ img-refer-value
- ; Value and parameter MUST match
-
- ;For name="BDAY"
- param = ("VALUE" "=" "date")
- ; Only value parameter allowed
-
- param =/ ("VALUE" "=" "date-time")
- ; Only value parameter allowed
-
- value = date-value
- ; Value MUST match value type
-
- value =/ date-time-value
- ; Value MUST match value type
-
- ;For name="ADR"
- param = adr-param / text-param
- ; Only adr and text parameters allowed
-
- value = adr-value
-
- ;For name="LABEL"
- param = adr-param / text-param
- ; Only adr and text parameters allowed
-
- value = text-value
-
- ;For name="TEL"
- param = tel-param
- ; Only tel parameters allowed
-
- value = phone-number-value
-
- tel-param = "TYPE" "=" tel-type *("," tel-type)
-
-
-
-
-Dawson & Howes Standards Track [Page 31]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- tel-type = "HOME" / "WORK" / "PREF" / "VOICE" / "FAX" / "MSG"
- / "CELL" / "PAGER" / "BBS" / "MODEM" / "CAR" / "ISDN"
- / "VIDEO" / "PCS" / iana-token / x-name
- ; Values are case insensitive
-
- ;For name="EMAIL"
- param = email-param
- ; Only email parameters allowed
-
- value = text-value
-
- email-param = "TYPE" "=" email-type ["," "PREF"]
- ; Value is case insensitive
-
- email-type = "INTERNET" / "X400" / iana-token / "X-" word
- ; Values are case insensitive
-
- ;For name="MAILER"
- param = text-param
- ; Only text parameters allowed
-
- value = text-value
-
- ;For name="TZ"
- param = ""
- ; No parameters allowed
-
- value = utc-offset-value
-
- ;For name="GEO"
- param = ""
- ; No parameters allowed
-
- value = float-value ";" float-value
-
- ;For name="TITLE"
- param = text-param
- ; Only text parameters allowed
-
- value = text-value
-
- ;For name="ROLE"
- param = text-param
- ; Only text parameters allowed
-
- value = text-value
-
- ;For name="LOGO"
-
-
-
-Dawson & Howes Standards Track [Page 32]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- param = img-inline-param / img-refer-param
- ; Only image parameters allowed
-
- value = img-inline-value / img-refer-value
- ; Value and parameter MUST match
-
- ;For name="AGENT"
- param = agent-inline-param
-
- param =/ agent-refer-param
-
- value = agent-inline-value
- ; Value and parameter MUST match
-
- value =/ agent-refer-value
- ; Value and parameter MUST match
-
- agent-inline-param = ""
- ; No parameters allowed
-
- agent-refer-param = "VALUE" "=" "uri"
- ; Only value parameter allowed
-
- agent-inline-value = text-value
- ; Value MUST be a valid vCard object
-
- agent-refer-value = uri
- ; URI MUST refer to image content of given type
-
- ;For name="ORG"
-
- param = text-param
- ; Only text parameters allowed
-
- value = org-value
-
- org-value = *(text-value ";") text-value
- ; First is Organization Name, remainder are Organization Units.
-
- ;For name="CATEGORIES"
- param = text-param
- ; Only text parameters allowed
-
- value = text-list
-
- ;For name="NOTE"
- param = text-param
- ; Only text parameters allowed
-
-
-
-Dawson & Howes Standards Track [Page 33]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- value = text-value
-
- ;For name="PRODID"
- param = ""
- ; No parameters allowed
-
- value = text-value
-
- ;For name="REV"
- param = ["VALUE" =" "date-time"]
- ; Only value parameters allowed. Values are case insensitive.
-
- param =/ "VALUE" =" "date"
- ; Only value parameters allowed. Values are case insensitive.
-
- value = date-time-value
-
- value =/ date-value
-
- ;For name="SORT-STRING"
- param = text-param
- ; Only text parameters allowed
-
- value = text-value
-
- ;For name="SOUND"
- param = snd-inline-param
- ; Only sound parameters allowed
-
- param =/ snd-refer-param
- ; Only sound parameters allowed
-
- value = snd-line-value
- ; Value MUST match value type
-
- value =/ snd-refer-value
- ; Value MUST match value type
-
- snd-inline-value = binary-value CRLF
- ; Value MUST be "b" encoded audio content
-
- snd-inline-param = ("VALUE" "=" "binary"])
- / ("ENCODING" "=" "b")
- / ("TYPE" "=" *SAFE-CHAR)
- ; Value MUST be an IANA registered audio type
-
- snd-refer-value = uri
- ; URI MUST refer to audio content of given type
-
-
-
-Dawson & Howes Standards Track [Page 34]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- snd-refer-param = ("VALUE" "=" "uri")
- / ("TYPE" "=" word)
- ; Value MUST be an IANA registered audio type
-
- ;For name="UID"
- param = ""
- ; No parameters allowed
-
- value = text-value
-
- ;For name="URL"
- param = ""
- ; No parameters allowed
-
- value = uri
-
- ;For name="VERSION"
- ;This type MUST be included in a vCard object.
- param = ""
- ; No parameters allowed
-
- value = text-value
- ; Value MUST be "3.0"
-
- ;For name="CLASS"
- param = ""
- ; No parameters allowed
-
- value = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL"
- / iana-token / x-name
- ; Value are case insensitive
-
- ;For name="KEY"
- param = key-txt-param
- ; Only value and type parameters allowed
-
- param =/ key-bin-param
- ; Only value and type parameters allowed
-
- value = text-value
-
- value =/ binary-value
-
- key-txt-param = "TYPE" "=" keytype
-
- key-bin-param = ("TYPE" "=" keytype)
- / ("ENCODING" "=" "b")
- ; Value MUST be a "b" encoded key or certificate
-
-
-
-Dawson & Howes Standards Track [Page 35]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- keytype = "X509" / "PGP" / iana-token / x-name
- ; Values are case insensitive
-
- ;For name="X-" non-standard type
- param = text-param / (x-name "=" param-value)
- ; Only text or non-standard parameters allowed
-
- value = text-value
-
- ;*******************************************
- ; vCard Commonly Used Parameter Definition
- ;*******************************************
-
- text-param = ("VALUE" "=" "ptext")
- / ("LANGUAGE" "=" langval)
- / (x-name "=" param-value)
-
- langval = <a language string as defined in RFC 1766>
-
- img-inline-value = binary-value
- ;Value MUST be "b" encoded image content
-
- img-inline-param
-
- img-inline-param = ("VALUE" "=" "binary")
- / ("ENCODING" "=" "b")
- / ("TYPE" "=" param-value
- ;TYPE value MUST be an IANA registered image type
-
- img-refer-value = uri
- ;URI MUST refer to image content of given type
-
- img-refer-param = ("VALUE" "=" "uri")
- / ("TYPE" "=" param-value)
- ;TYPE value MUST be an IANA registered image type
-
- adr-param = ("TYPE" "=" adr-type *("," adr-type))
- / (text-param)
-
- adr-type = "dom" / "intl" / "postal" / "parcel" / "home"
- / "work" / "pref" / iana-type / x-name
-
- adr-value = 0*6(text-value ";") text-value
- ; PO Box, Extended Address, Street, Locality, Region, Postal
- ; Code, Country Name
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 36]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- ;*******************************************
- ; vCard Type Value Definition
- ;*******************************************
-
- text-value-list = 1*text-value *("," 1*text-value)
-
- text-value = *(SAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
-
- ESCAPED-CHAR = "\\" / "\;" / "\," / "\n" / "\N")
- ; \\ encodes \, \n or \N encodes newline
- ; \; encodes ;, \, encodes ,
-
- binary-value = <A "b" encoded text value as defined in [RFC 2047]>
-
- date-value = <A single date value as defined in [MIME-DIR]>
-
- time-value = <A single time value as defined in [MIME-DIR]>
-
- date-time-value = <A single date-time value as defined in [MIME-DIR]
-
- float-value = <A single float value as defined in [MIME-DIR]>
-
- phone-number-value = <A single text value as defined in [CCITT
- E.163] and [CCITT X.121]>
-
- uri-value = <A uri value as defined in [MIME-DIR]>
-
- utc-offset-value = ("+" / "-") time-hour ":" time-minute
- time-hour = 2DIGIT ;00-23
- time-minute = 2DIGIT ;00-59
-
-5. Differences From vCard v2.1
-
- This specification has been reviewed by the IETF community. The
- review process introduced a number of differences from the [VCARD]
- version 2.1. These differences require that vCard objects conforming
- to this specification have a different version number than a vCard
- conforming to [VCARD]. The differences include the following:
-
- . The QUOTED-PRINTABLE inline encoding has been eliminated.
- Only the "B" encoding of [RFC 2047] is an allowed value for
- the ENCODING parameter.
-
- . The method for specifying CRLF character sequences in text
- type values has been changed. The CRLF character sequence in
- a text type value is specified with the backslash character
- sequence "\n" or "\N".
-
-
-
-
-Dawson & Howes Standards Track [Page 37]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- . Any COMMA or SEMICOLON in a text type value must be backslash
- escaped.
-
- . VERSION value corresponding to this specification MUST be
- "3.0".
-
- . The [MIME-DIR] predefined types of SOURCE, NAME and PROFILE
- are allowed.
-
- . The [MIME-DIR] VALUE type parameter for value data typing is
- allowed. In addition, there are extensions made to these type
- values for additional value types used in this specification.
-
- . The [VCARD] CHARSET type parameter has been eliminated.
- Character set can only be specified on the CHARSET parameter
- on the Content-Type MIME header field.
-
- . The [VCARD] support for non-significant WSP character has
- been eliminated.
-
- . The "TYPE=" prefix to parameter values is required. In
- [VCARD] this was optional.
-
- . LOGO, PHOTO and SOUND multimedia formats MUST be either IANA
- registered types or non-standard types.
-
- . Inline binary content must be "B" encoded and folded. A blank
- line after the encoded binary content is no longer required.
-
- . TEL values can be identified as personal communication
- services telephone numbers with the PCS type parameter value.
-
- . The CATEGORIES, CLASS, NICKNAME, PRODID and SORT-STRING types
- have been added.
-
- . The VERSION, N and FN types MUST be specified in a vCard.
- This identifies the version of the specification that the
- object was formatted to. It also assures that every vCard
- will include both a structured and formatted name that can be
- used to identify the object.
-
-
-
-
-
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 38]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-6. Acknowledgements
-
- The many valuable comments contributed by members of the IETF ASID
- working group are gratefully acknowledged, as are the contributions
- by Roland Alden, Stephen Bartlett, Alec Dun, Patrik Faltstrom, Daniel
- Gurney, Bruce Johnston, Daniel Klaussen, Pete Miller, Keith Moore,
- Vinod Seraphin, Michelle Watkins. Chris Newman was especially helpful
- in navigating the intricacies of ABNF lore.
-
-7. Authors' Addresses
-
- BEGIN:vCard
- VERSION:3.0
- FN:Frank Dawson
- ORG:Lotus Development Corporation
- ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive
- ;Raleigh;NC;27613-3502;U.S.A.
- TEL;TYPE=VOICE,MSG,WORK:+1-919-676-9515
- TEL;TYPE=FAX,WORK:+1-919-676-9564
- EMAIL;TYPE=INTERNET,PREF:Frank_Dawson@Lotus.com
- EMAIL;TYPE=INTERNET:fdawson@earthlink.net
- URL:http://home.earthlink.net/~fdawson
- END:vCard
-
-
- BEGIN:vCard
- VERSION:3.0
- FN:Tim Howes
- ORG:Netscape Communications Corp.
- ADR;TYPE=WORK:;;501 E. Middlefield Rd.;Mountain View;
- CA; 94043;U.S.A.
- TEL;TYPE=VOICE,MSG,WORK:+1-415-937-3419
- TEL;TYPE=FAX,WORK:+1-415-528-4164
- EMAIL;TYPE=INTERNET:howes@netscape.com
- END:vCard
-
-8. Security Considerations
-
- vCards can carry cryptographic keys or certificates, as described in
- Section 3.7.2.
-
- Section 3.7.1 specifies a desired security classification policy for
- a particular vCard. That policy is not enforced in any way.
-
- The vCard objects have no inherent authentication or privacy, but can
- easily be carried by any security mechanism that transfers MIME
- objects with authentication or privacy. In cases where threats of
- "spoofed" vCard information is a concern, the vCard SHOULD BE
-
-
-
-Dawson & Howes Standards Track [Page 39]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- transported using one of these secure mechanisms.
-
- The information in a vCard may become out of date. In cases where the
- vitality of data is important to an originator of a vCard, the "URL"
- type described in section 3.6.8 SHOULD BE specified. In addition, the
- "REV" type described in section 3.6.4 can be specified to indicate
- the last time that the vCard data was updated.
-
-9. References
-
- [ISO 8601] ISO 8601:1988 - Data elements and interchange formats -
- Information interchange - Representation of dates and
- times - The International Organization for
- Standardization, June, 1988.
-
- [ISO 8601 TC] ISO 8601, Technical Corrigendum 1 - Data elements and
- interchange formats - Information interchange -
- Representation of dates and times - The International
- Organization for Standardization, May, 1991.
-
- [ISO 9070] ISO 9070, Information Processing - SGML support
- facilities - Registration Procedures for Public Text
- Owner Identifiers, April, 1991.
-
- [CCITT E.163] Recommendation E.163 - Numbering Plan for The
- International Telephone Service, CCITT Blue Book,
- Fascicle II.2, pp. 128-134, November, 1988.
-
- [CCITT X.121] Recommendation X.121 - International Numbering Plan for
- Public Data Networks, CCITT Blue Book, Fascicle VIII.3,
- pp. 317-332, November, 1988.
-
- [CCITT X.520] Recommendation X.520 - The Directory - Selected
- Attribute Types, November 1988.
-
- [CCITT X.521] Recommendation X.521 - The Directory - Selected Object
- Classes, November 1988.
-
- [MIME-DIR] Howes, T., Smith, M., and F. Dawson, "A MIME Content-
- Type for Directory Information", RFC 2425, September
- 1998.
-
- [RFC 1738] Berners-Lee, T., Masinter, L., and M. McCahill,
- "Uniform Resource Locators (URL)", RFC 1738, December
- 1994.
-
- [RFC 1766] Alvestrand, H., "Tags for the Identification of
- Languages", RFC 1766, March 1995.
-
-
-
-Dawson & Howes Standards Track [Page 40]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
- [RFC 1872] Levinson, E., "The MIME Multipart/Related Content-
- type", RFC 1872, December 1995.
-
- [RFC 2045] Freed, N., and N. Borenstein, "Multipurpose Internet
- Mail Extensions (MIME) - Part One: Format of Internet
- Message Bodies", RFC 2045, November 1996.
-
- [RFC 2046] Freed, N., and N. Borenstein, "Multipurpose Internet
- Mail Extensions (MIME) - Part Two: Media Types", RFC
- 2046, November 1996.
-
- [RFC 2047] Moore, K., "Multipurpose Internet Mail Extensions
- (MIME) - Part Three: Message Header Extensions for
- Non-ASCII Text", RFC 2047, November 1996.
-
- [RFC 2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) - Part Four:
- Registration Procedures", RFC 2048, January 1997.
-
- [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC 2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 2234, November 1997.
-
- [UNICODE] "The Unicode Standard - Version 2.0", The Unicode
- Consortium, July 1996.
-
- [VCARD] Internet Mail Consortium, "vCard - The Electronic
- Business Card Version 2.1",
- http://www.imc.org/pdi/vcard-21.txt, September 18,
- 1996.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 41]
-
-RFC 2426 vCard MIME Directory Profile September 1998
-
-
-10. Full Copyright Statement
-
- Copyright (C) The Internet Society (1998). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Dawson & Howes Standards Track [Page 42]
-
diff --git a/proto/rfc2595.txt b/proto/rfc2595.txt
@@ -1,843 +0,0 @@
-
-
-
-
-
-
-Network Working Group C. Newman
-Request for Comments: 2595 Innosoft
-Category: Standards Track June 1999
-
-
- Using TLS with IMAP, POP3 and ACAP
-
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1999). All Rights Reserved.
-
-1. Motivation
-
- The TLS protocol (formerly known as SSL) provides a way to secure an
- application protocol from tampering and eavesdropping. The option of
- using such security is desirable for IMAP, POP and ACAP due to common
- connection eavesdropping and hijacking attacks [AUTH]. Although
- advanced SASL authentication mechanisms can provide a lightweight
- version of this service, TLS is complimentary to simple
- authentication-only SASL mechanisms or deployed clear-text password
- login commands.
-
- Many sites have a high investment in authentication infrastructure
- (e.g., a large database of a one-way-function applied to user
- passwords), so a privacy layer which is not tightly bound to user
- authentication can protect against network eavesdropping attacks
- without requiring a new authentication infrastructure and/or forcing
- all users to change their password. Recognizing that such sites will
- desire simple password authentication in combination with TLS
- encryption, this specification defines the PLAIN SASL mechanism for
- use with protocols which lack a simple password authentication
- command such as ACAP and SMTP. (Note there is a separate RFC for the
- STARTTLS command in SMTP [SMTPTLS].)
-
- There is a strong desire in the IETF to eliminate the transmission of
- clear-text passwords over unencrypted channels. While SASL can be
- used for this purpose, TLS provides an additional tool with different
- deployability characteristics. A server supporting both TLS with
-
-
-
-
-Newman Standards Track [Page 1]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- simple passwords and a challenge/response SASL mechanism is likely to
- interoperate with a wide variety of clients without resorting to
- unencrypted clear-text passwords.
-
- The STARTTLS command rectifies a number of the problems with using a
- separate port for a "secure" protocol variant. Some of these are
- mentioned in section 7.
-
-1.1. Conventions Used in this Document
-
- The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
- "MAY", and "OPTIONAL" in this document are to be interpreted as
- described in "Key words for use in RFCs to Indicate Requirement
- Levels" [KEYWORDS].
-
- Terms related to authentication are defined in "On Internet
- Authentication" [AUTH].
-
- Formal syntax is defined using ABNF [ABNF].
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server respectively.
-
-2. Basic Interoperability and Security Requirements
-
- The following requirements apply to all implementations of the
- STARTTLS extension for IMAP, POP3 and ACAP.
-
-2.1. Cipher Suite Requirements
-
- Implementation of the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher
- suite is REQUIRED. This is important as it assures that any two
- compliant implementations can be configured to interoperate.
-
- All other cipher suites are OPTIONAL.
-
-2.2. Privacy Operational Mode Security Requirements
-
- Both clients and servers SHOULD have a privacy operational mode which
- refuses authentication unless successful activation of an encryption
- layer (such as that provided by TLS) occurs prior to or at the time
- of authentication and which will terminate the connection if that
- encryption layer is deactivated. Implementations are encouraged to
- have flexability with respect to the minimal encryption strength or
- cipher suites permitted. A minimalist approach to this
- recommendation would be an operational mode where the
- TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite is mandatory prior to
- permitting authentication.
-
-
-
-Newman Standards Track [Page 2]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- Clients MAY have an operational mode which uses encryption only when
- it is advertised by the server, but authentication continues
- regardless. For backwards compatibility, servers SHOULD have an
- operational mode where only the authentication mechanisms required by
- the relevant base protocol specification are needed to successfully
- authenticate.
-
-2.3. Clear-Text Password Requirements
-
- Clients and servers which implement STARTTLS MUST be configurable to
- refuse all clear-text login commands or mechanisms (including both
- standards-track and nonstandard mechanisms) unless an encryption
- layer of adequate strength is active. Servers which allow
- unencrypted clear-text logins SHOULD be configurable to refuse
- clear-text logins both for the entire server, and on a per-user
- basis.
-
-2.4. Server Identity Check
-
- During the TLS negotiation, the client MUST check its understanding
- of the server hostname against the server's identity as presented in
- the server Certificate message, in order to prevent man-in-the-middle
- attacks. Matching is performed according to these rules:
-
- - The client MUST use the server hostname it used to open the
- connection as the value to compare against the server name as
- expressed in the server certificate. The client MUST NOT use any
- form of the server hostname derived from an insecure remote source
- (e.g., insecure DNS lookup). CNAME canonicalization is not done.
-
- - If a subjectAltName extension of type dNSName is present in the
- certificate, it SHOULD be used as the source of the server's
- identity.
-
- - Matching is case-insensitive.
-
- - A "*" wildcard character MAY be used as the left-most name
- component in the certificate. For example, *.example.com would
- match a.example.com, foo.example.com, etc. but would not match
- example.com.
-
- - If the certificate contains multiple names (e.g. more than one
- dNSName field), then a match with any one of the fields is
- considered acceptable.
-
- If the match fails, the client SHOULD either ask for explicit user
- confirmation, or terminate the connection and indicate the server's
- identity is suspect.
-
-
-
-Newman Standards Track [Page 3]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
-2.5. TLS Security Policy Check
-
- Both the client and server MUST check the result of the STARTTLS
- command and subsequent TLS negotiation to see whether acceptable
- authentication or privacy was achieved. Ignoring this step
- completely invalidates using TLS for security. The decision about
- whether acceptable authentication or privacy was achieved is made
- locally, is implementation-dependent, and is beyond the scope of this
- document.
-
-3. IMAP STARTTLS extension
-
- When the TLS extension is present in IMAP, "STARTTLS" is listed as a
- capability in response to the CAPABILITY command. This extension
- adds a single command, "STARTTLS" to the IMAP protocol which is used
- to begin a TLS negotiation.
-
-3.1. STARTTLS Command
-
- Arguments: none
-
- Responses: no specific responses for this command
-
- Result: OK - begin TLS negotiation
- BAD - command unknown or arguments invalid
-
- A TLS negotiation begins immediately after the CRLF at the end of
- the tagged OK response from the server. Once a client issues a
- STARTTLS command, it MUST NOT issue further commands until a
- server response is seen and the TLS negotiation is complete.
-
- The STARTTLS command is only valid in non-authenticated state.
- The server remains in non-authenticated state, even if client
- credentials are supplied during the TLS negotiation. The SASL
- [SASL] EXTERNAL mechanism MAY be used to authenticate once TLS
- client credentials are successfully exchanged, but servers
- supporting the STARTTLS command are not required to support the
- EXTERNAL mechanism.
-
- Once TLS has been started, the client MUST discard cached
- information about server capabilities and SHOULD re-issue the
- CAPABILITY command. This is necessary to protect against
- man-in-the-middle attacks which alter the capabilities list prior
- to STARTTLS. The server MAY advertise different capabilities
- after STARTTLS.
-
- The formal syntax for IMAP is amended as follows:
-
-
-
-
-Newman Standards Track [Page 4]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- command_any =/ "STARTTLS"
-
- Example: C: a001 CAPABILITY
- S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
- S: a001 OK CAPABILITY completed
- C: a002 STARTTLS
- S: a002 OK Begin TLS negotiation now
- <TLS negotiation, further commands are under TLS layer>
- C: a003 CAPABILITY
- S: * CAPABILITY IMAP4rev1 AUTH=EXTERNAL
- S: a003 OK CAPABILITY completed
- C: a004 LOGIN joe password
- S: a004 OK LOGIN completed
-
-3.2. IMAP LOGINDISABLED capability
-
- The current IMAP protocol specification (RFC 2060) requires the
- implementation of the LOGIN command which uses clear-text passwords.
- Many sites may choose to disable this command unless encryption is
- active for security reasons. An IMAP server MAY advertise that the
- LOGIN command is disabled by including the LOGINDISABLED capability
- in the capability response. Such a server will respond with a tagged
- "NO" response to any attempt to use the LOGIN command.
-
- An IMAP server which implements STARTTLS MUST implement support for
- the LOGINDISABLED capability on unencrypted connections.
-
- An IMAP client which complies with this specification MUST NOT issue
- the LOGIN command if this capability is present.
-
- This capability is useful to prevent clients compliant with this
- specification from sending an unencrypted password in an environment
- subject to passive attacks. It has no impact on an environment
- subject to active attacks as a man-in-the-middle attacker can remove
- this capability. Therefore this does not relieve clients of the need
- to follow the privacy mode recommendation in section 2.2.
-
- Servers advertising this capability will fail to interoperate with
- many existing compliant IMAP clients and will be unable to prevent
- those clients from disclosing the user's password.
-
-4. POP3 STARTTLS extension
-
- The POP3 STARTTLS extension adds the STLS command to POP3 servers.
- If this is implemented, the POP3 extension mechanism [POP3EXT] MUST
- also be implemented to avoid the need for client probing of multiple
- commands. The capability name "STLS" indicates this command is
- present and permitted in the current state.
-
-
-
-Newman Standards Track [Page 5]
-
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-
-
- STLS
-
- Arguments: none
-
- Restrictions:
- Only permitted in AUTHORIZATION state.
-
- Discussion:
- A TLS negotiation begins immediately after the CRLF at the
- end of the +OK response from the server. A -ERR response
- MAY result if a security layer is already active. Once a
- client issues a STLS command, it MUST NOT issue further
- commands until a server response is seen and the TLS
- negotiation is complete.
-
- The STLS command is only permitted in AUTHORIZATION state
- and the server remains in AUTHORIZATION state, even if
- client credentials are supplied during the TLS negotiation.
- The AUTH command [POP-AUTH] with the EXTERNAL mechanism
- [SASL] MAY be used to authenticate once TLS client
- credentials are successfully exchanged, but servers
- supporting the STLS command are not required to support the
- EXTERNAL mechanism.
-
- Once TLS has been started, the client MUST discard cached
- information about server capabilities and SHOULD re-issue
- the CAPA command. This is necessary to protect against
- man-in-the-middle attacks which alter the capabilities list
- prior to STLS. The server MAY advertise different
- capabilities after STLS.
-
- Possible Responses:
- +OK -ERR
-
- Examples:
- C: STLS
- S: +OK Begin TLS negotiation
- <TLS negotiation, further commands are under TLS layer>
- ...
- C: STLS
- S: -ERR Command not permitted when TLS active
-
-
-
-
-
-
-
-
-
-
-Newman Standards Track [Page 6]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
-5. ACAP STARTTLS extension
-
- When the TLS extension is present in ACAP, "STARTTLS" is listed as a
- capability in the ACAP greeting. No arguments to this capability are
- defined at this time. This extension adds a single command,
- "STARTTLS" to the ACAP protocol which is used to begin a TLS
- negotiation.
-
-5.1. STARTTLS Command
-
- Arguments: none
-
- Responses: no specific responses for this command
-
- Result: OK - begin TLS negotiation
- BAD - command unknown or arguments invalid
-
- A TLS negotiation begins immediately after the CRLF at the end of
- the tagged OK response from the server. Once a client issues a
- STARTTLS command, it MUST NOT issue further commands until a
- server response is seen and the TLS negotiation is complete.
-
- The STARTTLS command is only valid in non-authenticated state.
- The server remains in non-authenticated state, even if client
- credentials are supplied during the TLS negotiation. The SASL
- [SASL] EXTERNAL mechanism MAY be used to authenticate once TLS
- client credentials are successfully exchanged, but servers
- supporting the STARTTLS command are not required to support the
- EXTERNAL mechanism.
-
- After the TLS layer is established, the server MUST re-issue an
- untagged ACAP greeting. This is necessary to protect against
- man-in-the-middle attacks which alter the capabilities list prior
- to STARTTLS. The client MUST discard cached capability
- information and replace it with the information from the new ACAP
- greeting. The server MAY advertise different capabilities after
- STARTTLS.
-
- The formal syntax for ACAP is amended as follows:
-
- command_any =/ "STARTTLS"
-
- Example: S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
- C: a002 STARTTLS
- S: a002 OK "Begin TLS negotiation now"
- <TLS negotiation, further commands are under TLS layer>
- S: * ACAP (SASL "CRAM-MD5" "PLAIN" "EXTERNAL")
-
-
-
-
-Newman Standards Track [Page 7]
-
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-
-
-6. PLAIN SASL mechanism
-
- Clear-text passwords are simple, interoperate with almost all
- existing operating system authentication databases, and are useful
- for a smooth transition to a more secure password-based
- authentication mechanism. The drawback is that they are unacceptable
- for use over an unencrypted network connection.
-
- This defines the "PLAIN" SASL mechanism for use with ACAP and other
- protocols with no clear-text login command. The PLAIN SASL mechanism
- MUST NOT be advertised or used unless a strong encryption layer (such
- as the provided by TLS) is active or backwards compatibility dictates
- otherwise.
-
- The mechanism consists of a single message from the client to the
- server. The client sends the authorization identity (identity to
- login as), followed by a US-ASCII NUL character, followed by the
- authentication identity (identity whose password will be used),
- followed by a US-ASCII NUL character, followed by the clear-text
- password. The client may leave the authorization identity empty to
- indicate that it is the same as the authentication identity.
-
- The server will verify the authentication identity and password with
- the system authentication database and verify that the authentication
- credentials permit the client to login as the authorization identity.
- If both steps succeed, the user is logged in.
-
- The server MAY also use the password to initialize any new
- authentication database, such as one suitable for CRAM-MD5
- [CRAM-MD5].
-
- Non-US-ASCII characters are permitted as long as they are represented
- in UTF-8 [UTF-8]. Use of non-visible characters or characters which
- a user may be unable to enter on some keyboards is discouraged.
-
- The formal grammar for the client message using Augmented BNF [ABNF]
- follows.
-
- message = [authorize-id] NUL authenticate-id NUL password
- authenticate-id = 1*UTF8-SAFE ; MUST accept up to 255 octets
- authorize-id = 1*UTF8-SAFE ; MUST accept up to 255 octets
- password = 1*UTF8-SAFE ; MUST accept up to 255 octets
- NUL = %x00
- UTF8-SAFE = %x01-09 / %x0B-0C / %x0E-7F / UTF8-2 /
- UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
- UTF8-1 = %x80-BF
- UTF8-2 = %xC0-DF UTF8-1
- UTF8-3 = %xE0-EF 2UTF8-1
-
-
-
-Newman Standards Track [Page 8]
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-
-
- UTF8-4 = %xF0-F7 3UTF8-1
- UTF8-5 = %xF8-FB 4UTF8-1
- UTF8-6 = %xFC-FD 5UTF8-1
-
- Here is an example of how this might be used to initialize a CRAM-MD5
- authentication database for ACAP:
-
- Example: S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
- C: a001 AUTHENTICATE "CRAM-MD5"
- S: + "<1896.697170952@postoffice.reston.mci.net>"
- C: "tim b913a602c7eda7a495b4e6e7334d3890"
- S: a001 NO (TRANSITION-NEEDED)
- "Please change your password, or use TLS to login"
- C: a002 STARTTLS
- S: a002 OK "Begin TLS negotiation now"
- <TLS negotiation, further commands are under TLS layer>
- S: * ACAP (SASL "CRAM-MD5" "PLAIN" "EXTERNAL")
- C: a003 AUTHENTICATE "PLAIN" {21+}
- C: <NUL>tim<NUL>tanstaaftanstaaf
- S: a003 OK CRAM-MD5 password initialized
-
- Note: In this example, <NUL> represents a single ASCII NUL octet.
-
-7. imaps and pop3s ports
-
- Separate "imaps" and "pop3s" ports were registered for use with SSL.
- Use of these ports is discouraged in favor of the STARTTLS or STLS
- commands.
-
- A number of problems have been observed with separate ports for
- "secure" variants of protocols. This is an attempt to enumerate some
- of those problems.
-
- - Separate ports lead to a separate URL scheme which intrudes into
- the user interface in inappropriate ways. For example, many web
- pages use language like "click here if your browser supports SSL."
- This is a decision the browser is often more capable of making than
- the user.
-
- - Separate ports imply a model of either "secure" or "not secure."
- This can be misleading in a number of ways. First, the "secure"
- port may not in fact be acceptably secure as an export-crippled
- cipher suite might be in use. This can mislead users into a false
- sense of security. Second, the normal port might in fact be
- secured by using a SASL mechanism which includes a security layer.
- Thus the separate port distinction makes the complex topic of
- security policy even more confusing. One common result of this
- confusion is that firewall administrators are often misled into
-
-
-
-Newman Standards Track [Page 9]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- permitting the "secure" port and blocking the standard port. This
- could be a poor choice given the common use of SSL with a 40-bit
- key encryption layer and plain-text password authentication is less
- secure than strong SASL mechanisms such as GSSAPI with Kerberos 5.
-
- - Use of separate ports for SSL has caused clients to implement only
- two security policies: use SSL or don't use SSL. The desirable
- security policy "use TLS when available" would be cumbersome with
- the separate port model, but is simple with STARTTLS.
-
- - Port numbers are a limited resource. While they are not yet in
- short supply, it is unwise to set a precedent that could double (or
- worse) the speed of their consumption.
-
-
-8. IANA Considerations
-
- This constitutes registration of the "STARTTLS" and "LOGINDISABLED"
- IMAP capabilities as required by section 7.2.1 of RFC 2060 [IMAP].
-
- The registration for the POP3 "STLS" capability follows:
-
- CAPA tag: STLS
- Arguments: none
- Added commands: STLS
- Standard commands affected: May enable USER/PASS as a side-effect.
- CAPA command SHOULD be re-issued after successful completion.
- Announced states/Valid states: AUTHORIZATION state only.
- Specification reference: this memo
-
- The registration for the ACAP "STARTTLS" capability follows:
-
- Capability name: STARTTLS
- Capability keyword: STARTTLS
- Capability arguments: none
- Published Specification(s): this memo
- Person and email address for further information:
- see author's address section below
-
- The registration for the PLAIN SASL mechanism follows:
-
- SASL mechanism name: PLAIN
- Security Considerations: See section 9 of this memo
- Published specification: this memo
- Person & email address to contact for further information:
- see author's address section below
- Intended usage: COMMON
- Author/Change controller: see author's address section below
-
-
-
-Newman Standards Track [Page 10]
-
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-
-
-9. Security Considerations
-
- TLS only provides protection for data sent over a network connection.
- Messages transferred over IMAP or POP3 are still available to server
- administrators and usually subject to eavesdropping, tampering and
- forgery when transmitted through SMTP or NNTP. TLS is no substitute
- for an end-to-end message security mechanism using MIME security
- multiparts [MIME-SEC].
-
- A man-in-the-middle attacker can remove STARTTLS from the capability
- list or generate a failure response to the STARTTLS command. In
- order to detect such an attack, clients SHOULD warn the user when
- session privacy is not active and/or be configurable to refuse to
- proceed without an acceptable level of security.
-
- A man-in-the-middle attacker can always cause a down-negotiation to
- the weakest authentication mechanism or cipher suite available. For
- this reason, implementations SHOULD be configurable to refuse weak
- mechanisms or cipher suites.
-
- Any protocol interactions prior to the TLS handshake are performed in
- the clear and can be modified by a man-in-the-middle attacker. For
- this reason, clients MUST discard cached information about server
- capabilities advertised prior to the start of the TLS handshake.
-
- Clients are encouraged to clearly indicate when the level of
- encryption active is known to be vulnerable to attack using modern
- hardware (such as encryption keys with 56 bits of entropy or less).
-
- The LOGINDISABLED IMAP capability (discussed in section 3.2) only
- reduces the potential for passive attacks, it provides no protection
- against active attacks. The responsibility remains with the client
- to avoid sending a password over a vulnerable channel.
-
- The PLAIN mechanism relies on the TLS encryption layer for security.
- When used without TLS, it is vulnerable to a common network
- eavesdropping attack. Therefore PLAIN MUST NOT be advertised or used
- unless a suitable TLS encryption layer is active or backwards
- compatibility dictates otherwise.
-
- When the PLAIN mechanism is used, the server gains the ability to
- impersonate the user to all services with the same password
- regardless of any encryption provided by TLS or other network privacy
- mechanisms. While many other authentication mechanisms have similar
- weaknesses, stronger SASL mechanisms such as Kerberos address this
- issue. Clients are encouraged to have an operational mode where all
- mechanisms which are likely to reveal the user's password to the
- server are disabled.
-
-
-
-Newman Standards Track [Page 11]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- The security considerations for TLS apply to STARTTLS and the
- security considerations for SASL apply to the PLAIN mechanism.
- Additional security requirements are discussed in section 2.
-
-10. References
-
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 2234, November 1997.
-
- [ACAP] Newman, C. and J. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November 1997.
-
- [AUTH] Haller, N. and R. Atkinson, "On Internet Authentication",
- RFC 1704, October 1994.
-
- [CRAM-MD5] Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP
- AUTHorize Extension for Simple Challenge/Response", RFC
- 2195, September 1997.
-
- [IMAP] Crispin, M., "Internet Message Access Protocol - Version
- 4rev1", RFC 2060, December 1996.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [MIME-SEC] Galvin, J., Murphy, S., Crocker, S. and N. Freed,
- "Security Multiparts for MIME: Multipart/Signed and
- Multipart/Encrypted", RFC 1847, October 1995.
-
- [POP3] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
- STD 53, RFC 1939, May 1996.
-
- [POP3EXT] Gellens, R., Newman, C. and L. Lundblade, "POP3 Extension
- Mechanism", RFC 2449, November 1998.
-
- [POP-AUTH] Myers, J., "POP3 AUTHentication command", RFC 1734,
- December 1994.
-
- [SASL] Myers, J., "Simple Authentication and Security Layer
- (SASL)", RFC 2222, October 1997.
-
- [SMTPTLS] Hoffman, P., "SMTP Service Extension for Secure SMTP over
- TLS", RFC 2487, January 1999.
-
- [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
- RFC 2246, January 1999.
-
-
-
-
-
-Newman Standards Track [Page 12]
-
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-
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", RFC 2279, January 1998.
-
-
-11. Author's Address
-
- Chris Newman
- Innosoft International, Inc.
- 1050 Lakes Drive
- West Covina, CA 91790 USA
-
- EMail: chris.newman@innosoft.com
-
-
-A. Appendix -- Compliance Checklist
-
- An implementation is not compliant if it fails to satisfy one or more
- of the MUST requirements for the protocols it implements. An
- implementation that satisfies all the MUST and all the SHOULD
- requirements for its protocols is said to be "unconditionally
- compliant"; one that satisfies all the MUST requirements but not all
- the SHOULD requirements for its protocols is said to be
- "conditionally compliant".
-
- Rules Section
- ----- -------
- Mandatory-to-implement Cipher Suite 2.1
- SHOULD have mode where encryption required 2.2
- server SHOULD have mode where TLS not required 2.2
- MUST be configurable to refuse all clear-text login
- commands or mechanisms 2.3
- server SHOULD be configurable to refuse clear-text
- login commands on entire server and on per-user basis 2.3
- client MUST check server identity 2.4
- client MUST use hostname used to open connection 2.4
- client MUST NOT use hostname from insecure remote lookup 2.4
- client SHOULD support subjectAltName of dNSName type 2.4
- client SHOULD ask for confirmation or terminate on fail 2.4
- MUST check result of STARTTLS for acceptable privacy 2.5
- client MUST NOT issue commands after STARTTLS
- until server response and negotiation done 3.1,4,5.1
- client MUST discard cached information 3.1,4,5.1,9
- client SHOULD re-issue CAPABILITY/CAPA command 3.1,4
- IMAP server with STARTTLS MUST implement LOGINDISABLED 3.2
- IMAP client MUST NOT issue LOGIN if LOGINDISABLED 3.2
- POP server MUST implement POP3 extensions 4
- ACAP server MUST re-issue ACAP greeting 5.1
-
-
-
-
-Newman Standards Track [Page 13]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
- client SHOULD warn when session privacy not active and/or
- refuse to proceed without acceptable security level 9
- SHOULD be configurable to refuse weak mechanisms or
- cipher suites 9
-
- The PLAIN mechanism is an optional part of this specification.
- However if it is implemented the following rules apply:
-
- Rules Section
- ----- -------
- MUST NOT use PLAIN unless strong encryption active
- or backwards compatibility dictates otherwise 6,9
- MUST use UTF-8 encoding for characters in PLAIN 6
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Newman Standards Track [Page 14]
-
-RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
-
-
-Full Copyright Statement
-
- Copyright (C) The Internet Society (1999). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Newman Standards Track [Page 15]
-
diff --git a/proto/rfc2646.txt b/proto/rfc2646.txt
@@ -1,787 +0,0 @@
-
-
-
-
-
-
-Network Working Group R. Gellens, Editor
-Request for Comments: 2646 Qualcomm
-Updates: 2046 August 1999
-Category: Standards Track
-
-
- The Text/Plain Format Parameter
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (1999). All Rights Reserved.
-
-Table of Contents
-
- 1. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . 2
- 2. Conventions Used in this Document . . . . . . . . . . . . . 2
- 3. The Problem . . . . . . . . . . . . . . . . . . . . . . . . 2
- 3.1. Paragraph Text . . . . . . . . . . . . . . . . . . . . 3
- 3.2. Embarrassing Line Wrap . . . . . . . . . . . . . . . . . 3
- 3.3. New Media Types . . . . . . . . . . . . . . . . . . . . 4
- 4. The Format Parameter to the Text/Plain Media Type . . . . . 4
- 4.1. Generating Format=Flowed . . . . . . . . . . . . . . . 5
- 4.2. Interpreting Format=Flowed . . . . . . . . . . . . . . . 6
- 4.3. Usenet Signature Convention . . . . . . . . . . . . . . 7
- 4.4. Space-Stuffing . . . . . . . . . . . . . . . . . . . . . 7
- 4.5. Quoting . . . . . . . . . . . . . . . . . . . . . . . . 8
- 4.6. Digital Signatures and Encryption . . . . . . . . . . . 9
- 4.7. Line Analysis Table . . . . . . . . . . . . . . . . . . 10
- 4.8. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
- 5. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
- 6. Failure Modes . . . . . . . . . . . . . . . . . . . . . . . 11
- 6.1. Trailing White Space Corruption . . . . . . . . . . . . 11
- 7. Security Considerations . . . . . . . . . . . . . . . . . . 12
- 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 12
- 9. Internationalization Considerations . . . . . . . . . . . . 12
- 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12
- 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
- 12. Editor's Address . . . . . . . . . . . . . . . . . . . . . 13
- 13. Full Copyright Statement . . . . . . . . . . . . . . . . . . 14
-
-
-
-
-Gellens Standards Track [Page 1]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
-1. Abstract
-
- Interoperability problems have been observed with erroneous labelling
- of paragraph text as Text/Plain, and with various forms of
- "embarrassing line wrap." (See section 3.)
-
- Attempts to deploy new media types, such as Text/Enriched [RICH] and
- Text/HTML [HTML] have suffered from a lack of backwards compatibility
- and an often hostile user reaction at the receiving end.
-
- What is required is a format which is in all significant ways
- Text/Plain, and therefore is quite suitable for display as
- Text/Plain, and yet allows the sender to express to the receiver
- which lines can be considered a logical paragraph, and thus flowed
- (wrapped and joined) as appropriate.
-
- This memo proposes a new parameter to be used with Text/Plain, and,
- in the presence of this parameter, the use of trailing whitespace to
- indicate flowed lines. This results in an encoding which appears as
- normal Text/Plain in older implementations, since it is in fact
- normal Text/Plain.
-
-2. Conventions Used in this Document
-
- The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
- and "MAY" in this document are to be interpreted as described in "Key
- words for use in RFCs to Indicate Requirement Levels" [KEYWORDS].
-
-3. The Problem
-
- The Text/Plain media type is the lowest common denominator of
- Internet email, with lines of no more than 997 characters (by
- convention usually no more than 80), and where the CRLF sequence
- represents a line break [MIME-IMT].
-
- Text/Plain is usually displayed as preformatted text, often in a
- fixed font. That is, the characters start at the left margin of the
- display window, and advance to the right until a CRLF sequence is
- seen, at which point a new line is started, again at the left margin.
- When a line length exceeds the display window, some clients will wrap
- the line, while others invoke a horizontal scroll bar.
-
- Text which meets this description is defined by this memo as "fixed".
-
- Some interoperability problems have been observed with this media
- type:
-
-
-
-
-
-Gellens Standards Track [Page 2]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
-3.1. Paragraph Text
-
- Many modern programs use a proportional-spaced font and CRLF to
- represent paragraph breaks. Line breaks are "soft", occurring as
- needed on display. That is, characters are grouped into a paragraph
- until a CRLF sequence is seen, at which point a new paragraph is
- started. Each paragraph is displayed, starting at the left margin
- (or paragraph indent), and continuing to the right until a word is
- encountered which does not fit in the remaining display width. This
- word is displayed at the left margin of the next line. This
- continues until the paragraph ends (a CRLF is seen). Extra vertical
- space is left between paragraphs.
-
- Text which meets this description is defined by this memo as
- "flowed".
-
- Numerous software products erroneously label this media type as
- Text/Plain, resulting in much user discomfort.
-
-3.2. Embarrassing Line Wrap
-
- As Text/Plain messages get quoted in replies or forwarded messages,
- the length of each line gradually increases, resulting in
- "embarrassing line wrap." This results in text which is at best hard
- to read, and often confuses attributions.
-
- Example:
-
- >>>>>>This is a comment from the first message to show a
- >quoting example.
- >>>>>This is a comment from the second message to show a
- >quoting example.
- >>>>This is a comment from the third message.
- >>>This is a comment from the fourth message.
-
- It can be confusing to assign attribution to lines 2 and 4 above.
-
- In addition, as devices with display widths smaller than 80
- characters become more popular, embarrassing line wrap has become
- even more prevalent, even with unquoted text.
-
-
-
-
-
-
-
-
-
-
-
-Gellens Standards Track [Page 3]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- Example:
-
- This is paragraph text that is
- meant to be flowed across
- several lines.
- However, the sending mailer is
- converting it to fixed text at
- a width of 72
- characters, which causes it to
- look like this when shown on a
- PDA with only
- 30 character lines.
-
-3.3. New Media Types
-
- Attempts to deploy new media types, such as Text/Enriched [RICH] and
- Text/HTML [HTML] have suffered from a lack of backwards compatibility
- and an often hostile user reaction at the receiving end.
-
- In particular, Text/Enriched requires that open angle brackets ("<")
- and hard line breaks be doubled, with resulting user unhappiness when
- viewed as Text/Plain. Text/HTML requires even more alteration of
- text, with a corresponding increase in user complaints.
-
- A proposal to define a new media type to explicitly represent the
- paragraph form suffered from a lack of interoperability with
- currently deployed software. Some programs treat unknown subtypes of
- Text as an attachment.
-
- What is desired is a format which is in all significant ways
- Text/Plain, and therefore is quite suitable for display as
- Text/Plain, and yet allows the sender to express to the receiver
- which lines can be considered a logical paragraph, and thus flowed
- (wrapped and joined) as appropriate.
-
-4. The Format Parameter to the Text/Plain Media Type
-
- This document defines a new MIME parameter for use with Text/Plain:
-
- Name: Format
- Value: Fixed, Flowed
-
- (Neither the parameter name nor its value are case sensitive.)
-
- If not specified, a value of Fixed is assumed. The semantics of the
- Fixed value are the usual associated with Text/Plain [MIME-IMT].
-
-
-
-
-
-Gellens Standards Track [Page 4]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- A value of Flowed indicates that the definition of flowed text (as
- specified in this memo) was used on generation, and MAY be used on
- reception.
-
- This section discusses flowed text; section 5 provides a formal
- definition.
-
- Because flowed lines are all-but-indistinguishable from fixed lines,
- currently deployed software treats flowed lines as normal Text/Plain
- (which is what they are). Thus, no interoperability problems are
- expected.
-
- Note that this memo describes an on-the-wire format. It does not
- address formats for local file storage.
-
-4.1. Generating Format=Flowed
-
- When generating Format=Flowed text, lines SHOULD be shorter than 80
- characters. As suggested values, any paragraph longer than 79
- characters in total length could be wrapped using lines of 72 or
- fewer characters. While the specific line length used is a matter of
- aesthetics and preference, longer lines are more likely to require
- rewrapping and to encounter difficulties with older mailers. It has
- been suggested that 66 character lines are the most readable.
-
- (The reason for the restriction to 79 or fewer characters between
- CRLFs on the wire is to ensure that all lines, even when displayed by
- a non-flowed-aware program, will fit in a standard 80-column screen
- without having to be wrapped. The limit is 79, not 80, because while
- 80 fit on a line, the last column is often reserved for a line-wrap
- indicator.)
-
- When creating flowed text, the generating agent wraps, that is,
- inserts 'soft' line breaks as needed. Soft line breaks are added
- between words. Because a soft line break is a SP CRLF sequence, the
- generating agent creates one by inserting a CRLF after the occurance
- of a space.
-
- A generating agent SHOULD NOT insert white space into a word (a
- sequence of printable characters not containing spaces). If faced
- with a word which exceeds 79 characters (but less than 998
- characters, the [SMTP] limit on line length), the agent SHOULD send
- the word as is and exceed the 79-character limit on line length.
-
-
-
-
-
-
-
-
-Gellens Standards Track [Page 5]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- A generating agent SHOULD:
-
- 1. Ensure all lines (fixed and flowed) are 79 characters or
- fewer in length, counting the trailing space but not
- counting the CRLF, unless a word by itself exceeds 79
- characters.
- 2. Trim spaces before user-inserted hard line breaks.
- 3. Space-stuff lines which start with a space, "From ", or
- ">".
-
- In order to create messages which do not require space-stuffing, and
- are thus more aesthetically pleasing when viewed as Format=Fixed, a
- generating agent MAY avoid wrapping immediately before ">", "From ",
- or space.
-
- (See sections 4.4 and 4.5 for more information on space-stuffing and
- quoting, respectively.)
-
- A Format=Flowed message consists of zero or more paragraphs, each
- containing one or more flowed lines followed by one fixed line. The
- usual case is a series of flowed text lines with blank (empty) fixed
- lines between them.
-
- Any number of fixed lines can appear between paragraphs.
-
- [Quoted-Printable] encoding SHOULD NOT be used with Format=Flowed
- unless absolutely necessary (for example, non-US-ASCII (8-bit)
- characters over a strictly 7-bit transport such as unextended SMTP).
- In particular, a message SHOULD NOT be encoded in Quoted-Printable
- for the sole purpose of protecting the trailing space on flowed lines
- unless the body part is cryptographically signed or encrypted (see
- Section 4.6).
-
- The intent of Format=Flowed is to allow user agents to generate
- flowed text which is non-obnoxious when viewed as pure, raw
- Text/Plain (without any decoding); use of Quoted-Printable hinders
- this and may cause Format=Flowed to be rejected by end users.
-
-4.2. Interpreting Format=Flowed
-
- If the first character of a line is a quote mark (">"), the line is
- considered to be quoted (see section 4.5). Logically, all quote
- marks are counted and deleted, resulting in a line with a non-zero
- quote depth, and content. (The agent is of course free to display the
- content with quote marks or excerpt bars or anything else.)
- Logically, this test for quoted lines is done before any other tests
- (that is, before checking for space-stuffed and flowed).
-
-
-
-
-Gellens Standards Track [Page 6]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- If the first character of a line is a space, the line has been
- space-stuffed (see section 4.4). Logically, this leading space is
- deleted before examining the line further (that is, before checking
- for flowed).
-
- If the line ends in one or more spaces, the line is flowed.
- Otherwise it is fixed. Trailing spaces are part of the line's
- content, but the CRLF of a soft line break is not.
-
- A series of one or more flowed lines followed by one fixed line is
- considered a paragraph, and MAY be flowed (wrapped and unwrapped) as
- appropriate on display and in the construction of new messages (see
- section 4.5).
-
- A line consisting of one or more spaces (after deleting a stuffed
- space) is considered a flowed line.
-
-4.3. Usenet Signature Convention
-
- There is a convention in Usenet news of using "-- " as the separator
- line between the body and the signature of a message. When
- generating a Format=Flowed message containing a Usenet-style
- separator before the signature, the separator line is sent as-is.
- This is a special case; an (optionally quoted) line consisting of
- DASH DASH SP is not considered flowed.
-
-4.4. Space-Stuffing
-
- In order to allow for unquoted lines which start with ">", and to
- protect against systems which "From-munge" in-transit messages
- (modifying any line which starts with "From " to ">From "),
- Format=Flowed provides for space-stuffing.
-
- Space-stuffing adds a single space to the start of any line which
- needs protection when the message is generated. On reception, if the
- first character of a line is a space, it is logically deleted. This
- occurs after the test for a quoted line, and before the test for a
- flowed line.
-
- On generation, any unquoted lines which start with ">", and any lines
- which start with a space or "From " SHOULD be space-stuffed. Other
- lines MAY be space-stuffed as desired.
-
- (Note that space-stuffing is similar to dot-stuffing as specified in
- [SMTP].)
-
-
-
-
-
-
-Gellens Standards Track [Page 7]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- If a space-stuffed message is received by an agent which handles
- Format=Flowed, the space-stuffing is reversed and thus the message
- appears unchanged. An agent which is not aware of Format=Flowed will
- of course not undo any space-stuffing, thus Format=Flowed messages
- may appear with a leading space on some lines (those which start with
- a space, ">" which is not a quote indicator, or "From "). Since
- lines which require space-stuffing rarely occur, and the aesthetic
- consequences of unreversed space-stuffing are minimal, this is not
- expected to be a significant problem.
-
-4.5. Quoting
-
- In Format=Flowed, the canonical quote indicator (or quote mark) is
- one or more close angle bracket (">") characters. Lines which start
- with the quote indicator are considered quoted. The number of ">"
- characters at the start of the line specifies the quote depth.
- Flowed lines which are also quoted may require special handling on
- display and when copied to new messages.
-
- When creating quoted flowed lines, each such line starts with the
- quote indicator.
-
- Note that because of space-stuffing, the lines
- >> Exit, Stage Left
- and
- >>Exit, Stage Left
- are semantically identical; both have a quote-depth of two, and a
- content of "Exit, Stage Left".
-
- However, the line
- > > Exit, Stage Left
- is different. It has a quote-depth of one, and a content of
- "> Exit, Stage Left".
-
- When generating quoted flowed lines, an agent needs to pay attention
- to changes in quote depth. A sequence of quoted lines of the same
- quote depth SHOULD be encoded as a paragraph, with the last line
- generated as fixed and prior lines generated as flowed.
-
- If a receiving agent wishes to reformat flowed quoted lines (joining
- and/or wrapping them) on display or when generating new messages, the
- lines SHOULD be de-quoted, reformatted, and then re-quoted. To
- de-quote, the number of close angle brackets in the quote indicator
- at the start of each line is counted. Consecutive lines with the
- same quoting depth are considered one paragraph and are reformatted
- together. To re-quote after reformatting, a quote indicator
- containing the same number of close angle brackets originally present
- is prefixed to each line.
-
-
-
-Gellens Standards Track [Page 8]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- On reception, if a change in quoting depth occurs on a flowed line,
- this is an improperly formatted message. The receiver SHOULD handle
- this error by using the 'quote-depth-wins' rule, which is to ignore
- the flowed indicator and treat the line as fixed. That is, the
- change in quote depth ends the paragraph.
-
- For example, consider the following sequence of lines (using '*' to
- indicate a soft line break, i.e., SP CRLF, and '#' to indicate a hard
- line break, i.e., CRLF):
-
- > Thou villainous ill-breeding spongy dizzy-eyed*
- > reeky elf-skinned pigeon-egg!* <--- problem ---<
- >> Thou artless swag-bellied milk-livered*
- >> dismal-dreaming idle-headed scut!#
- >>> Thou errant folly-fallen spleeny reeling-ripe*
- >>> unmuzzled ratsbane!#
- >>>> Henceforth, the coding style is to be strictly*
- >>>> enforced, including the use of only upper case.#
- >>>>> I've noticed a lack of adherence to the coding*
- >>>>> styles, of late.#
- >>>>>> Any complaints?#
-
- The second line ends in a soft line break, even though it is the last
- line of the one-deep quote block. The question then arises as to how
- this line should be interpreted, considering that the next line is
- the first line of the two-deep quote block.
-
- The example text above, when processed according to quote-depth wins,
- results in the first two lines being considered as one quoted, flowed
- section, with a quote depth of 1; the third and fourth lines become a
- quoted, flowed section, with a quote depth of 2.
-
- A generating agent SHOULD NOT create this situation; a receiving
- agent SHOULD handle it using quote-depth wins.
-
-4.6. Digital Signatures and Encryption
-
- If a message is digitally signed or encrypted it is important that
- cryptographic processing use the on-the-wire Format=Flowed format.
- That is, during generation the message SHOULD be prepared for
- transmission, including addition of soft line breaks, space-stuffing,
- and [Quoted-Printable] encoding (to protect soft line breaks) before
- being digitally signed or encrypted; similarly, on receipt the
- message SHOULD have the signature verified or be decrypted before
- [Quoted-Printable] decoding and removal of stuffed spaces, soft line
- breaks and quote marks, and reflowing.
-
-
-
-
-
-Gellens Standards Track [Page 9]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
-4.7. Line Analysis Table
-
- Lines contained in a Text/Plain body part with Format=Flowed can be
- analyzed by examining the start and end of the line. If the line
- starts with the quote indicator, it is quoted. If the line ends with
- one or more space characters, it is flowed. This is summarized by
- the following table:
-
- Starts Ends in
- with One or Line
- Quote More Spaces Type
- ------ ----------- ---------------
- no no unquoted, fixed
- yes no quoted, fixed
- no yes unquoted, flowed
- yes yes quoted, flowed
-
-4.8. Examples
-
- The following example contains three paragraphs:
-
- `Take some more tea,' the March Hare said to Alice, very
- earnestly.
-
- `I've had nothing yet,' Alice replied in an offended tone, `so I
- can't take more.'
-
- `You mean you can't take LESS,' said the Hatter: `it's very easy
- to take MORE than nothing.'
-
- This could be encoded as follows (using '*' to indicate a soft line
- break, that is, SP CRLF sequence, and '#' to indicate a hard line
- break, that is, CRLF):
-
- `Take some more tea,' the March Hare said to Alice, very*
- earnestly.*
- #
- `I've had nothing yet,' Alice replied in an offended tone, `so*
- I can't take more.'*
- #
- `You mean you can't take LESS,' said the Hatter: `it's very*
- easy to take MORE than nothing.'#
-
-
-
-
-
-
-
-
-
-Gellens Standards Track [Page 10]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- To show an example of quoting, here we have the same exchange,
- presented as a series of direct quotes:
-
- >>>Take some more tea.#
- >>I've had nothing yet, so I can't take more.#
- >You mean you can't take LESS, it's very easy to take*
- >MORE than nothing.#
-
-5. ABNF
-
- The constructs used in Text/Plain; Format=Flowed body parts are
- described using [ABNF], including the Core Rules:
-
- paragraph = 1*flowed-line fixed-line
- fixed-line = fixed / sig-sep
- fixed = [quote] [stuffing] *text-char non-sp CRLF
- flowed-line = flow-qt / flow-unqt
- flow-qt = quote [stuffing] *text-char 1*SP CRLF
- flow-unqt = [stuffing] *text-char 1*SP CRLF
- non-sp = %x01-09 / %x0B / %x0C / %x0E-1F / %x21-7F
- ; any 7-bit US-ASCII character, excluding
- ; NUL, CR, LF, and SP
- quote = 1*">"
- sig-sep = [quote] "--" SP CRLF
- stuffing = [SP] ; space-stuffed, added on generation if
- ; needed, deleted on reception
- text-char = non-sp / SP
-
-6. Failure Modes
-
-6.1. Trailing White Space Corruption
-
- There are systems in existence which alter trailing whitespace on
- messages which pass through them. Such systems may strip, or in
- rarer cases, add trailing whitespace, in violation of RFC 821 [SMTP]
- section 4.5.2.
-
- Stripping trailing whitespace has the effect of converting flowed
- lines to fixed lines, which results in a message no worse than if
- Format=Flowed had not been used.
-
- Adding trailing whitespace to a Format=Flowed message may result in a
- malformed display or reply.
-
- Since most systems which add trailing white space do so to create a
- line which fills an internal record format, the result is almost
- always a line which contains an even number of characters (counting
- the added trailing white space).
-
-
-
-Gellens Standards Track [Page 11]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- One possible avoidance, therefore, would be to define Format=Flowed
- lines to use either one or two trailing space characters to indicate
- a flowed line, such that the total line length is odd. However,
- considering the scarcity of such systems today, it is not worth the
- added complexity.
-
-7. Security Considerations
-
- This parameter introduces no security considerations beyond those
- which apply to Text/Plain.
-
- Section 4.6 discusses the interaction between Format=Flowed and
- digital signatures or encryption.
-
-8. IANA Considerations
-
- IANA is requested to add a reference to this specification in the
- Text/Plain Media Type registration.
-
-9. Internationalization Considerations
-
- The line wrap and quoting specifications of Format=Flowed may not be
- suitable for certain charsets, such as for Arabic and Hebrew
- characters that read from right to left. Care should be taken in
- applying format=flowed in these cases, as format=fixed combined with
- quoted-printable encoding may be more suitable.
-
-10. Acknowledgments
-
- This proposal evolved from a discussion of Chris Newman's
- Text/Paragraph draft which took place on the IETF 822 mailing list.
- Special thanks to Ian Bell, Steve Dorner, Brian Kelley, Dan Kohn,
- Laurence Lundblade, and Dan Wing for their reviews, comments,
- suggestions, and discussions.
-
-11. References
-
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", RFC 2234, November
- 1997.
-
- [KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RICH] Resnick, P. and A. Walker, "The text/enriched MIME
- Content-type", RFC 1896, February 1996.
-
-
-
-
-
-Gellens Standards Track [Page 12]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
- [MIME-IMT] Freed, N. and N. Borenstein, "Multipurpose
- Internet Mail Extensions (MIME) Part Two: Media
- Types", RFC 2046, November 1996.
-
- [Quoted-Printable] Freed, N. and N. Borenstein, "Multipurpose
- Internet Mail Extensions (MIME) Part One: Format
- of Internet Message Bodies", RFC 2045, November
- 1996.
-
- [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD
- 10, RFC 821, August 1982.
-
- [HTML] Berners-Lee, T. and D. Connolly, "Hypertext Markup
- Language -- 2.0", RFC 1866, November 1995.
-
-
-12. Editor's Address
-
- Randall Gellens
- QUALCOMM Incorporated
- 5775 Morehouse Dr.
- San Diego, CA 92121-2779
- USA
-
- Phone: +1 619 651 5115
- EMail: randy@qualcomm.com
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Gellens Standards Track [Page 13]
-
-RFC 2646 The Text/Plain Format Parameter August 1999
-
-
-13. Full Copyright Statement
-
- Copyright (C) The Internet Society (1999). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Gellens Standards Track [Page 14]
-
diff --git a/proto/rfc2822.txt b/proto/rfc2822.txt
@@ -1,2859 +0,0 @@
-
-
-
-
-
-
-Network Working Group P. Resnick, Editor
-Request for Comments: 2822 QUALCOMM Incorporated
-Obsoletes: 822 April 2001
-Category: Standards Track
-
-
- Internet Message Format
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2001). All Rights Reserved.
-
-Abstract
-
- This standard specifies a syntax for text messages that are sent
- between computer users, within the framework of "electronic mail"
- messages. This standard supersedes the one specified in Request For
- Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
- Messages", updating it to reflect current practice and incorporating
- incremental changes that were specified in other RFCs.
-
-Table of Contents
-
- 1. Introduction ............................................... 3
- 1.1. Scope .................................................... 3
- 1.2. Notational conventions ................................... 4
- 1.2.1. Requirements notation .................................. 4
- 1.2.2. Syntactic notation ..................................... 4
- 1.3. Structure of this document ............................... 4
- 2. Lexical Analysis of Messages ............................... 5
- 2.1. General Description ...................................... 5
- 2.1.1. Line Length Limits ..................................... 6
- 2.2. Header Fields ............................................ 7
- 2.2.1. Unstructured Header Field Bodies ....................... 7
- 2.2.2. Structured Header Field Bodies ......................... 7
- 2.2.3. Long Header Fields ..................................... 7
- 2.3. Body ..................................................... 8
- 3. Syntax ..................................................... 9
- 3.1. Introduction ............................................. 9
- 3.2. Lexical Tokens ........................................... 9
-
-
-
-Resnick Standards Track [Page 1]
-
-RFC 2822 Internet Message Format April 2001
-
-
- 3.2.1. Primitive Tokens ....................................... 9
- 3.2.2. Quoted characters ......................................10
- 3.2.3. Folding white space and comments .......................11
- 3.2.4. Atom ...................................................12
- 3.2.5. Quoted strings .........................................13
- 3.2.6. Miscellaneous tokens ...................................13
- 3.3. Date and Time Specification ..............................14
- 3.4. Address Specification ....................................15
- 3.4.1. Addr-spec specification ................................16
- 3.5 Overall message syntax ....................................17
- 3.6. Field definitions ........................................18
- 3.6.1. The origination date field .............................20
- 3.6.2. Originator fields ......................................21
- 3.6.3. Destination address fields .............................22
- 3.6.4. Identification fields ..................................23
- 3.6.5. Informational fields ...................................26
- 3.6.6. Resent fields ..........................................26
- 3.6.7. Trace fields ...........................................28
- 3.6.8. Optional fields ........................................29
- 4. Obsolete Syntax ............................................29
- 4.1. Miscellaneous obsolete tokens ............................30
- 4.2. Obsolete folding white space .............................31
- 4.3. Obsolete Date and Time ...................................31
- 4.4. Obsolete Addressing ......................................33
- 4.5. Obsolete header fields ...................................33
- 4.5.1. Obsolete origination date field ........................34
- 4.5.2. Obsolete originator fields .............................34
- 4.5.3. Obsolete destination address fields ....................34
- 4.5.4. Obsolete identification fields .........................35
- 4.5.5. Obsolete informational fields ..........................35
- 4.5.6. Obsolete resent fields .................................35
- 4.5.7. Obsolete trace fields ..................................36
- 4.5.8. Obsolete optional fields ...............................36
- 5. Security Considerations ....................................36
- 6. Bibliography ...............................................37
- 7. Editor's Address ...........................................38
- 8. Acknowledgements ...........................................39
- Appendix A. Example messages ..................................41
- A.1. Addressing examples ......................................41
- A.1.1. A message from one person to another with simple
- addressing .............................................41
- A.1.2. Different types of mailboxes ...........................42
- A.1.3. Group addresses ........................................43
- A.2. Reply messages ...........................................43
- A.3. Resent messages ..........................................44
- A.4. Messages with trace fields ...............................46
- A.5. White space, comments, and other oddities ................47
- A.6. Obsoleted forms ..........................................47
-
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- A.6.1. Obsolete addressing ....................................48
- A.6.2. Obsolete dates .........................................48
- A.6.3. Obsolete white space and comments ......................48
- Appendix B. Differences from earlier standards ................49
- Appendix C. Notices ...........................................50
- Full Copyright Statement ......................................51
-
-1. Introduction
-
-1.1. Scope
-
- This standard specifies a syntax for text messages that are sent
- between computer users, within the framework of "electronic mail"
- messages. This standard supersedes the one specified in Request For
- Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
- Messages" [RFC822], updating it to reflect current practice and
- incorporating incremental changes that were specified in other RFCs
- [STD3].
-
- This standard specifies a syntax only for text messages. In
- particular, it makes no provision for the transmission of images,
- audio, or other sorts of structured data in electronic mail messages.
- There are several extensions published, such as the MIME document
- series [RFC2045, RFC2046, RFC2049], which describe mechanisms for the
- transmission of such data through electronic mail, either by
- extending the syntax provided here or by structuring such messages to
- conform to this syntax. Those mechanisms are outside of the scope of
- this standard.
-
- In the context of electronic mail, messages are viewed as having an
- envelope and contents. The envelope contains whatever information is
- needed to accomplish transmission and delivery. (See [RFC2821] for a
- discussion of the envelope.) The contents comprise the object to be
- delivered to the recipient. This standard applies only to the format
- and some of the semantics of message contents. It contains no
- specification of the information in the envelope.
-
- However, some message systems may use information from the contents
- to create the envelope. It is intended that this standard facilitate
- the acquisition of such information by programs.
-
- This specification is intended as a definition of what message
- content format is to be passed between systems. Though some message
- systems locally store messages in this format (which eliminates the
- need for translation between formats) and others use formats that
- differ from the one specified in this standard, local storage is
- outside of the scope of this standard.
-
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-
- Note: This standard is not intended to dictate the internal formats
- used by sites, the specific message system features that they are
- expected to support, or any of the characteristics of user interface
- programs that create or read messages. In addition, this standard
- does not specify an encoding of the characters for either transport
- or storage; that is, it does not specify the number of bits used or
- how those bits are specifically transferred over the wire or stored
- on disk.
-
-1.2. Notational conventions
-
-1.2.1. Requirements notation
-
- This document occasionally uses terms that appear in capital letters.
- When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
- NOT", and "MAY" appear capitalized, they are being used to indicate
- particular requirements of this specification. A discussion of the
- meanings of these terms appears in [RFC2119].
-
-1.2.2. Syntactic notation
-
- This standard uses the Augmented Backus-Naur Form (ABNF) notation
- specified in [RFC2234] for the formal definitions of the syntax of
- messages. Characters will be specified either by a decimal value
- (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
- a case-insensitive literal value enclosed in quotation marks (e.g.,
- "A" for either uppercase or lowercase A). See [RFC2234] for the full
- description of the notation.
-
-1.3. Structure of this document
-
- This document is divided into several sections.
-
- This section, section 1, is a short introduction to the document.
-
- Section 2 lays out the general description of a message and its
- constituent parts. This is an overview to help the reader understand
- some of the general principles used in the later portions of this
- document. Any examples in this section MUST NOT be taken as
- specification of the formal syntax of any part of a message.
-
- Section 3 specifies formal ABNF rules for the structure of each part
- of a message (the syntax) and describes the relationship between
- those parts and their meaning in the context of a message (the
- semantics). That is, it describes the actual rules for the structure
- of each part of a message (the syntax) as well as a description of
- the parts and instructions on how they ought to be interpreted (the
- semantics). This includes analysis of the syntax and semantics of
-
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- subparts of messages that have specific structure. The syntax
- included in section 3 represents messages as they MUST be created.
- There are also notes in section 3 to indicate if any of the options
- specified in the syntax SHOULD be used over any of the others.
-
- Both sections 2 and 3 describe messages that are legal to generate
- for purposes of this standard.
-
- Section 4 of this document specifies an "obsolete" syntax. There are
- references in section 3 to these obsolete syntactic elements. The
- rules of the obsolete syntax are elements that have appeared in
- earlier revisions of this standard or have previously been widely
- used in Internet messages. As such, these elements MUST be
- interpreted by parsers of messages in order to be conformant to this
- standard. However, since items in this syntax have been determined
- to be non-interoperable or to cause significant problems for
- recipients of messages, they MUST NOT be generated by creators of
- conformant messages.
-
- Section 5 details security considerations to take into account when
- implementing this standard.
-
- Section 6 is a bibliography of references in this document.
-
- Section 7 contains the editor's address.
-
- Section 8 contains acknowledgements.
-
- Appendix A lists examples of different sorts of messages. These
- examples are not exhaustive of the types of messages that appear on
- the Internet, but give a broad overview of certain syntactic forms.
-
- Appendix B lists the differences between this standard and earlier
- standards for Internet messages.
-
- Appendix C has copyright and intellectual property notices.
-
-2. Lexical Analysis of Messages
-
-2.1. General Description
-
- At the most basic level, a message is a series of characters. A
- message that is conformant with this standard is comprised of
- characters with values in the range 1 through 127 and interpreted as
- US-ASCII characters [ASCII]. For brevity, this document sometimes
- refers to this range of characters as simply "US-ASCII characters".
-
-
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-
- Note: This standard specifies that messages are made up of characters
- in the US-ASCII range of 1 through 127. There are other documents,
- specifically the MIME document series [RFC2045, RFC2046, RFC2047,
- RFC2048, RFC2049], that extend this standard to allow for values
- outside of that range. Discussion of those mechanisms is not within
- the scope of this standard.
-
- Messages are divided into lines of characters. A line is a series of
- characters that is delimited with the two characters carriage-return
- and line-feed; that is, the carriage return (CR) character (ASCII
- value 13) followed immediately by the line feed (LF) character (ASCII
- value 10). (The carriage-return/line-feed pair is usually written in
- this document as "CRLF".)
-
- A message consists of header fields (collectively called "the header
- of the message") followed, optionally, by a body. The header is a
- sequence of lines of characters with special syntax as defined in
- this standard. The body is simply a sequence of characters that
- follows the header and is separated from the header by an empty line
- (i.e., a line with nothing preceding the CRLF).
-
-2.1.1. Line Length Limits
-
- There are two limits that this standard places on the number of
- characters in a line. Each line of characters MUST be no more than
- 998 characters, and SHOULD be no more than 78 characters, excluding
- the CRLF.
-
- The 998 character limit is due to limitations in many implementations
- which send, receive, or store Internet Message Format messages that
- simply cannot handle more than 998 characters on a line. Receiving
- implementations would do well to handle an arbitrarily large number
- of characters in a line for robustness sake. However, there are so
- many implementations which (in compliance with the transport
- requirements of [RFC2821]) do not accept messages containing more
- than 1000 character including the CR and LF per line, it is important
- for implementations not to create such messages.
-
- The more conservative 78 character recommendation is to accommodate
- the many implementations of user interfaces that display these
- messages which may truncate, or disastrously wrap, the display of
- more than 78 characters per line, in spite of the fact that such
- implementations are non-conformant to the intent of this
- specification (and that of [RFC2821] if they actually cause
- information to be lost). Again, even though this limitation is put on
- messages, it is encumbant upon implementations which display messages
-
-
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-
- to handle an arbitrarily large number of characters in a line
- (certainly at least up to the 998 character limit) for the sake of
- robustness.
-
-2.2. Header Fields
-
- Header fields are lines composed of a field name, followed by a colon
- (":"), followed by a field body, and terminated by CRLF. A field
- name MUST be composed of printable US-ASCII characters (i.e.,
- characters that have values between 33 and 126, inclusive), except
- colon. A field body may be composed of any US-ASCII characters,
- except for CR and LF. However, a field body may contain CRLF when
- used in header "folding" and "unfolding" as described in section
- 2.2.3. All field bodies MUST conform to the syntax described in
- sections 3 and 4 of this standard.
-
-2.2.1. Unstructured Header Field Bodies
-
- Some field bodies in this standard are defined simply as
- "unstructured" (which is specified below as any US-ASCII characters,
- except for CR and LF) with no further restrictions. These are
- referred to as unstructured field bodies. Semantically, unstructured
- field bodies are simply to be treated as a single line of characters
- with no further processing (except for header "folding" and
- "unfolding" as described in section 2.2.3).
-
-2.2.2. Structured Header Field Bodies
-
- Some field bodies in this standard have specific syntactical
- structure more restrictive than the unstructured field bodies
- described above. These are referred to as "structured" field bodies.
- Structured field bodies are sequences of specific lexical tokens as
- described in sections 3 and 4 of this standard. Many of these tokens
- are allowed (according to their syntax) to be introduced or end with
- comments (as described in section 3.2.3) as well as the space (SP,
- ASCII value 32) and horizontal tab (HTAB, ASCII value 9) characters
- (together known as the white space characters, WSP), and those WSP
- characters are subject to header "folding" and "unfolding" as
- described in section 2.2.3. Semantic analysis of structured field
- bodies is given along with their syntax.
-
-2.2.3. Long Header Fields
-
- Each header field is logically a single line of characters comprising
- the field name, the colon, and the field body. For convenience
- however, and to deal with the 998/78 character limitations per line,
- the field body portion of a header field can be split into a multiple
- line representation; this is called "folding". The general rule is
-
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-
- that wherever this standard allows for folding white space (not
- simply WSP characters), a CRLF may be inserted before any WSP. For
- example, the header field:
-
- Subject: This is a test
-
- can be represented as:
-
- Subject: This
- is a test
-
- Note: Though structured field bodies are defined in such a way that
- folding can take place between many of the lexical tokens (and even
- within some of the lexical tokens), folding SHOULD be limited to
- placing the CRLF at higher-level syntactic breaks. For instance, if
- a field body is defined as comma-separated values, it is recommended
- that folding occur after the comma separating the structured items in
- preference to other places where the field could be folded, even if
- it is allowed elsewhere.
-
- The process of moving from this folded multiple-line representation
- of a header field to its single line representation is called
- "unfolding". Unfolding is accomplished by simply removing any CRLF
- that is immediately followed by WSP. Each header field should be
- treated in its unfolded form for further syntactic and semantic
- evaluation.
-
-2.3. Body
-
- The body of a message is simply lines of US-ASCII characters. The
- only two limitations on the body are as follows:
-
- - CR and LF MUST only occur together as CRLF; they MUST NOT appear
- independently in the body.
-
- - Lines of characters in the body MUST be limited to 998 characters,
- and SHOULD be limited to 78 characters, excluding the CRLF.
-
- Note: As was stated earlier, there are other standards documents,
- specifically the MIME documents [RFC2045, RFC2046, RFC2048, RFC2049]
- that extend this standard to allow for different sorts of message
- bodies. Again, these mechanisms are beyond the scope of this
- document.
-
-
-
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-
-3. Syntax
-
-3.1. Introduction
-
- The syntax as given in this section defines the legal syntax of
- Internet messages. Messages that are conformant to this standard
- MUST conform to the syntax in this section. If there are options in
- this section where one option SHOULD be generated, that is indicated
- either in the prose or in a comment next to the syntax.
-
- For the defined expressions, a short description of the syntax and
- use is given, followed by the syntax in ABNF, followed by a semantic
- analysis. Primitive tokens that are used but otherwise unspecified
- come from [RFC2234].
-
- In some of the definitions, there will be nonterminals whose names
- start with "obs-". These "obs-" elements refer to tokens defined in
- the obsolete syntax in section 4. In all cases, these productions
- are to be ignored for the purposes of generating legal Internet
- messages and MUST NOT be used as part of such a message. However,
- when interpreting messages, these tokens MUST be honored as part of
- the legal syntax. In this sense, section 3 defines a grammar for
- generation of messages, with "obs-" elements that are to be ignored,
- while section 4 adds grammar for interpretation of messages.
-
-3.2. Lexical Tokens
-
- The following rules are used to define an underlying lexical
- analyzer, which feeds tokens to the higher-level parsers. This
- section defines the tokens used in structured header field bodies.
-
- Note: Readers of this standard need to pay special attention to how
- these lexical tokens are used in both the lower-level and
- higher-level syntax later in the document. Particularly, the white
- space tokens and the comment tokens defined in section 3.2.3 get used
- in the lower-level tokens defined here, and those lower-level tokens
- are in turn used as parts of the higher-level tokens defined later.
- Therefore, the white space and comments may be allowed in the
- higher-level tokens even though they may not explicitly appear in a
- particular definition.
-
-3.2.1. Primitive Tokens
-
- The following are primitive tokens referred to elsewhere in this
- standard, but not otherwise defined in [RFC2234]. Some of them will
- not appear anywhere else in the syntax, but they are convenient to
- refer to in other parts of this document.
-
-
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-
- Note: The "specials" below are just such an example. Though the
- specials token does not appear anywhere else in this standard, it is
- useful for implementers who use tools that lexically analyze
- messages. Each of the characters in specials can be used to indicate
- a tokenization point in lexical analysis.
-
-NO-WS-CTL = %d1-8 / ; US-ASCII control characters
- %d11 / ; that do not include the
- %d12 / ; carriage return, line feed,
- %d14-31 / ; and white space characters
- %d127
-
-text = %d1-9 / ; Characters excluding CR and LF
- %d11 /
- %d12 /
- %d14-127 /
- obs-text
-
-specials = "(" / ")" / ; Special characters used in
- "<" / ">" / ; other parts of the syntax
- "[" / "]" /
- ":" / ";" /
- "@" / "\" /
- "," / "." /
- DQUOTE
-
- No special semantics are attached to these tokens. They are simply
- single characters.
-
-3.2.2. Quoted characters
-
- Some characters are reserved for special interpretation, such as
- delimiting lexical tokens. To permit use of these characters as
- uninterpreted data, a quoting mechanism is provided.
-
-quoted-pair = ("\" text) / obs-qp
-
- Where any quoted-pair appears, it is to be interpreted as the text
- character alone. That is to say, the "\" character that appears as
- part of a quoted-pair is semantically "invisible".
-
- Note: The "\" character may appear in a message where it is not part
- of a quoted-pair. A "\" character that does not appear in a
- quoted-pair is not semantically invisible. The only places in this
- standard where quoted-pair currently appears are ccontent, qcontent,
- dcontent, no-fold-quote, and no-fold-literal.
-
-
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-
-3.2.3. Folding white space and comments
-
- White space characters, including white space used in folding
- (described in section 2.2.3), may appear between many elements in
- header field bodies. Also, strings of characters that are treated as
- comments may be included in structured field bodies as characters
- enclosed in parentheses. The following defines the folding white
- space (FWS) and comment constructs.
-
- Strings of characters enclosed in parentheses are considered comments
- so long as they do not appear within a "quoted-string", as defined in
- section 3.2.5. Comments may nest.
-
- There are several places in this standard where comments and FWS may
- be freely inserted. To accommodate that syntax, an additional token
- for "CFWS" is defined for places where comments and/or FWS can occur.
- However, where CFWS occurs in this standard, it MUST NOT be inserted
- in such a way that any line of a folded header field is made up
- entirely of WSP characters and nothing else.
-
-FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
- obs-FWS
-
-ctext = NO-WS-CTL / ; Non white space controls
-
- %d33-39 / ; The rest of the US-ASCII
- %d42-91 / ; characters not including "(",
- %d93-126 ; ")", or "\"
-
-ccontent = ctext / quoted-pair / comment
-
-comment = "(" *([FWS] ccontent) [FWS] ")"
-
-CFWS = *([FWS] comment) (([FWS] comment) / FWS)
-
- Throughout this standard, where FWS (the folding white space token)
- appears, it indicates a place where header folding, as discussed in
- section 2.2.3, may take place. Wherever header folding appears in a
- message (that is, a header field body containing a CRLF followed by
- any WSP), header unfolding (removal of the CRLF) is performed before
- any further lexical analysis is performed on that header field
- according to this standard. That is to say, any CRLF that appears in
- FWS is semantically "invisible."
-
- A comment is normally used in a structured field body to provide some
- human readable informational text. Since a comment is allowed to
- contain FWS, folding is permitted within the comment. Also note that
- since quoted-pair is allowed in a comment, the parentheses and
-
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-
- backslash characters may appear in a comment so long as they appear
- as a quoted-pair. Semantically, the enclosing parentheses are not
- part of the comment; the comment is what is contained between the two
- parentheses. As stated earlier, the "\" in any quoted-pair and the
- CRLF in any FWS that appears within the comment are semantically
- "invisible" and therefore not part of the comment either.
-
- Runs of FWS, comment or CFWS that occur between lexical tokens in a
- structured field header are semantically interpreted as a single
- space character.
-
-3.2.4. Atom
-
- Several productions in structured header field bodies are simply
- strings of certain basic characters. Such productions are called
- atoms.
-
- Some of the structured header field bodies also allow the period
- character (".", ASCII value 46) within runs of atext. An additional
- "dot-atom" token is defined for those purposes.
-
-atext = ALPHA / DIGIT / ; Any character except controls,
- "!" / "#" / ; SP, and specials.
- "$" / "%" / ; Used for atoms
- "&" / "'" /
- "*" / "+" /
- "-" / "/" /
- "=" / "?" /
- "^" / "_" /
- "`" / "{" /
- "|" / "}" /
- "~"
-
-atom = [CFWS] 1*atext [CFWS]
-
-dot-atom = [CFWS] dot-atom-text [CFWS]
-
-dot-atom-text = 1*atext *("." 1*atext)
-
- Both atom and dot-atom are interpreted as a single unit, comprised of
- the string of characters that make it up. Semantically, the optional
- comments and FWS surrounding the rest of the characters are not part
- of the atom; the atom is only the run of atext characters in an atom,
- or the atext and "." characters in a dot-atom.
-
-
-
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-
-3.2.5. Quoted strings
-
- Strings of characters that include characters other than those
- allowed in atoms may be represented in a quoted string format, where
- the characters are surrounded by quote (DQUOTE, ASCII value 34)
- characters.
-
-qtext = NO-WS-CTL / ; Non white space controls
-
- %d33 / ; The rest of the US-ASCII
- %d35-91 / ; characters not including "\"
- %d93-126 ; or the quote character
-
-qcontent = qtext / quoted-pair
-
-quoted-string = [CFWS]
- DQUOTE *([FWS] qcontent) [FWS] DQUOTE
- [CFWS]
-
- A quoted-string is treated as a unit. That is, quoted-string is
- identical to atom, semantically. Since a quoted-string is allowed to
- contain FWS, folding is permitted. Also note that since quoted-pair
- is allowed in a quoted-string, the quote and backslash characters may
- appear in a quoted-string so long as they appear as a quoted-pair.
-
- Semantically, neither the optional CFWS outside of the quote
- characters nor the quote characters themselves are part of the
- quoted-string; the quoted-string is what is contained between the two
- quote characters. As stated earlier, the "\" in any quoted-pair and
- the CRLF in any FWS/CFWS that appears within the quoted-string are
- semantically "invisible" and therefore not part of the quoted-string
- either.
-
-3.2.6. Miscellaneous tokens
-
- Three additional tokens are defined, word and phrase for combinations
- of atoms and/or quoted-strings, and unstructured for use in
- unstructured header fields and in some places within structured
- header fields.
-
-word = atom / quoted-string
-
-phrase = 1*word / obs-phrase
-
-
-
-
-
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-
-utext = NO-WS-CTL / ; Non white space controls
- %d33-126 / ; The rest of US-ASCII
- obs-utext
-
-unstructured = *([FWS] utext) [FWS]
-
-3.3. Date and Time Specification
-
- Date and time occur in several header fields. This section specifies
- the syntax for a full date and time specification. Though folding
- white space is permitted throughout the date-time specification, it
- is RECOMMENDED that a single space be used in each place that FWS
- appears (whether it is required or optional); some older
- implementations may not interpret other occurrences of folding white
- space correctly.
-
-date-time = [ day-of-week "," ] date FWS time [CFWS]
-
-day-of-week = ([FWS] day-name) / obs-day-of-week
-
-day-name = "Mon" / "Tue" / "Wed" / "Thu" /
- "Fri" / "Sat" / "Sun"
-
-date = day month year
-
-year = 4*DIGIT / obs-year
-
-month = (FWS month-name FWS) / obs-month
-
-month-name = "Jan" / "Feb" / "Mar" / "Apr" /
- "May" / "Jun" / "Jul" / "Aug" /
- "Sep" / "Oct" / "Nov" / "Dec"
-
-day = ([FWS] 1*2DIGIT) / obs-day
-
-time = time-of-day FWS zone
-
-time-of-day = hour ":" minute [ ":" second ]
-
-hour = 2DIGIT / obs-hour
-
-minute = 2DIGIT / obs-minute
-
-second = 2DIGIT / obs-second
-
-zone = (( "+" / "-" ) 4DIGIT) / obs-zone
-
-
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-
- The day is the numeric day of the month. The year is any numeric
- year 1900 or later.
-
- The time-of-day specifies the number of hours, minutes, and
- optionally seconds since midnight of the date indicated.
-
- The date and time-of-day SHOULD express local time.
-
- The zone specifies the offset from Coordinated Universal Time (UTC,
- formerly referred to as "Greenwich Mean Time") that the date and
- time-of-day represent. The "+" or "-" indicates whether the
- time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
- Universal Time. The first two digits indicate the number of hours
- difference from Universal Time, and the last two digits indicate the
- number of minutes difference from Universal Time. (Hence, +hhmm
- means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
- minutes). The form "+0000" SHOULD be used to indicate a time zone at
- Universal Time. Though "-0000" also indicates Universal Time, it is
- used to indicate that the time was generated on a system that may be
- in a local time zone other than Universal Time and therefore
- indicates that the date-time contains no information about the local
- time zone.
-
- A date-time specification MUST be semantically valid. That is, the
- day-of-the-week (if included) MUST be the day implied by the date,
- the numeric day-of-month MUST be between 1 and the number of days
- allowed for the specified month (in the specified year), the
- time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
- number of seconds allowing for a leap second; see [STD12]), and the
- zone MUST be within the range -9959 through +9959.
-
-3.4. Address Specification
-
- Addresses occur in several message header fields to indicate senders
- and recipients of messages. An address may either be an individual
- mailbox, or a group of mailboxes.
-
-address = mailbox / group
-
-mailbox = name-addr / addr-spec
-
-name-addr = [display-name] angle-addr
-
-angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
-
-group = display-name ":" [mailbox-list / CFWS] ";"
- [CFWS]
-
-
-
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-
-
-display-name = phrase
-
-mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
-
-address-list = (address *("," address)) / obs-addr-list
-
- A mailbox receives mail. It is a conceptual entity which does not
- necessarily pertain to file storage. For example, some sites may
- choose to print mail on a printer and deliver the output to the
- addressee's desk. Normally, a mailbox is comprised of two parts: (1)
- an optional display name that indicates the name of the recipient
- (which could be a person or a system) that could be displayed to the
- user of a mail application, and (2) an addr-spec address enclosed in
- angle brackets ("<" and ">"). There is also an alternate simple form
- of a mailbox where the addr-spec address appears alone, without the
- recipient's name or the angle brackets. The Internet addr-spec
- address is described in section 3.4.1.
-
- Note: Some legacy implementations used the simple form where the
- addr-spec appears without the angle brackets, but included the name
- of the recipient in parentheses as a comment following the addr-spec.
- Since the meaning of the information in a comment is unspecified,
- implementations SHOULD use the full name-addr form of the mailbox,
- instead of the legacy form, to specify the display name associated
- with a mailbox. Also, because some legacy implementations interpret
- the comment, comments generally SHOULD NOT be used in address fields
- to avoid confusing such implementations.
-
- When it is desirable to treat several mailboxes as a single unit
- (i.e., in a distribution list), the group construct can be used. The
- group construct allows the sender to indicate a named group of
- recipients. This is done by giving a display name for the group,
- followed by a colon, followed by a comma separated list of any number
- of mailboxes (including zero and one), and ending with a semicolon.
- Because the list of mailboxes can be empty, using the group construct
- is also a simple way to communicate to recipients that the message
- was sent to one or more named sets of recipients, without actually
- providing the individual mailbox address for each of those
- recipients.
-
-3.4.1. Addr-spec specification
-
- An addr-spec is a specific Internet identifier that contains a
- locally interpreted string followed by the at-sign character ("@",
- ASCII value 64) followed by an Internet domain. The locally
- interpreted string is either a quoted-string or a dot-atom. If the
- string can be represented as a dot-atom (that is, it contains no
- characters other than atext characters or "." surrounded by atext
-
-
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-
-
- characters), then the dot-atom form SHOULD be used and the
- quoted-string form SHOULD NOT be used. Comments and folding white
- space SHOULD NOT be used around the "@" in the addr-spec.
-
-addr-spec = local-part "@" domain
-
-local-part = dot-atom / quoted-string / obs-local-part
-
-domain = dot-atom / domain-literal / obs-domain
-
-domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
-
-dcontent = dtext / quoted-pair
-
-dtext = NO-WS-CTL / ; Non white space controls
-
- %d33-90 / ; The rest of the US-ASCII
- %d94-126 ; characters not including "[",
- ; "]", or "\"
-
- The domain portion identifies the point to which the mail is
- delivered. In the dot-atom form, this is interpreted as an Internet
- domain name (either a host name or a mail exchanger name) as
- described in [STD3, STD13, STD14]. In the domain-literal form, the
- domain is interpreted as the literal Internet address of the
- particular host. In both cases, how addressing is used and how
- messages are transported to a particular host is covered in the mail
- transport document [RFC2821]. These mechanisms are outside of the
- scope of this document.
-
- The local-part portion is a domain dependent string. In addresses,
- it is simply interpreted on the particular host as a name of a
- particular mailbox.
-
-3.5 Overall message syntax
-
- A message consists of header fields, optionally followed by a message
- body. Lines in a message MUST be a maximum of 998 characters
- excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
- characters excluding the CRLF. (See section 2.1.1 for explanation.)
- In a message body, though all of the characters listed in the text
- rule MAY be used, the use of US-ASCII control characters (values 1
- through 8, 11, 12, and 14 through 31) is discouraged since their
- interpretation by receivers for display is not guaranteed.
-
-
-
-
-
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-
-
-message = (fields / obs-fields)
- [CRLF body]
-
-body = *(*998text CRLF) *998text
-
- The header fields carry most of the semantic information and are
- defined in section 3.6. The body is simply a series of lines of text
- which are uninterpreted for the purposes of this standard.
-
-3.6. Field definitions
-
- The header fields of a message are defined here. All header fields
- have the same general syntactic structure: A field name, followed by
- a colon, followed by the field body. The specific syntax for each
- header field is defined in the subsequent sections.
-
- Note: In the ABNF syntax for each field in subsequent sections, each
- field name is followed by the required colon. However, for brevity
- sometimes the colon is not referred to in the textual description of
- the syntax. It is, nonetheless, required.
-
- It is important to note that the header fields are not guaranteed to
- be in a particular order. They may appear in any order, and they
- have been known to be reordered occasionally when transported over
- the Internet. However, for the purposes of this standard, header
- fields SHOULD NOT be reordered when a message is transported or
- transformed. More importantly, the trace header fields and resent
- header fields MUST NOT be reordered, and SHOULD be kept in blocks
- prepended to the message. See sections 3.6.6 and 3.6.7 for more
- information.
-
- The only required header fields are the origination date field and
- the originator address field(s). All other header fields are
- syntactically optional. More information is contained in the table
- following this definition.
-
-fields = *(trace
- *(resent-date /
- resent-from /
- resent-sender /
- resent-to /
- resent-cc /
- resent-bcc /
- resent-msg-id))
- *(orig-date /
- from /
- sender /
- reply-to /
-
-
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-
-
- to /
- cc /
- bcc /
- message-id /
- in-reply-to /
- references /
- subject /
- comments /
- keywords /
- optional-field)
-
- The following table indicates limits on the number of times each
- field may occur in a message header as well as any special
- limitations on the use of those fields. An asterisk next to a value
- in the minimum or maximum column indicates that a special restriction
- appears in the Notes column.
-
-Field Min number Max number Notes
-
-trace 0 unlimited Block prepended - see
- 3.6.7
-
-resent-date 0* unlimited* One per block, required
- if other resent fields
- present - see 3.6.6
-
-resent-from 0 unlimited* One per block - see
- 3.6.6
-
-resent-sender 0* unlimited* One per block, MUST
- occur with multi-address
- resent-from - see 3.6.6
-
-resent-to 0 unlimited* One per block - see
- 3.6.6
-
-resent-cc 0 unlimited* One per block - see
- 3.6.6
-
-resent-bcc 0 unlimited* One per block - see
- 3.6.6
-
-resent-msg-id 0 unlimited* One per block - see
- 3.6.6
-
-orig-date 1 1
-
-from 1 1 See sender and 3.6.2
-
-
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-
-
-sender 0* 1 MUST occur with multi-
- address from - see 3.6.2
-
-reply-to 0 1
-
-to 0 1
-
-cc 0 1
-
-bcc 0 1
-
-message-id 0* 1 SHOULD be present - see
- 3.6.4
-
-in-reply-to 0* 1 SHOULD occur in some
- replies - see 3.6.4
-
-references 0* 1 SHOULD occur in some
- replies - see 3.6.4
-
-subject 0 1
-
-comments 0 unlimited
-
-keywords 0 unlimited
-
-optional-field 0 unlimited
-
- The exact interpretation of each field is described in subsequent
- sections.
-
-3.6.1. The origination date field
-
- The origination date field consists of the field name "Date" followed
- by a date-time specification.
-
-orig-date = "Date:" date-time CRLF
-
- The origination date specifies the date and time at which the creator
- of the message indicated that the message was complete and ready to
- enter the mail delivery system. For instance, this might be the time
- that a user pushes the "send" or "submit" button in an application
- program. In any case, it is specifically not intended to convey the
- time that the message is actually transported, but rather the time at
- which the human or other creator of the message has put the message
- into its final form, ready for transport. (For example, a portable
- computer user who is not connected to a network might queue a message
-
-
-
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-
-
- for delivery. The origination date is intended to contain the date
- and time that the user queued the message, not the time when the user
- connected to the network to send the message.)
-
-3.6.2. Originator fields
-
- The originator fields of a message consist of the from field, the
- sender field (when applicable), and optionally the reply-to field.
- The from field consists of the field name "From" and a
- comma-separated list of one or more mailbox specifications. If the
- from field contains more than one mailbox specification in the
- mailbox-list, then the sender field, containing the field name
- "Sender" and a single mailbox specification, MUST appear in the
- message. In either case, an optional reply-to field MAY also be
- included, which contains the field name "Reply-To" and a
- comma-separated list of one or more addresses.
-
-from = "From:" mailbox-list CRLF
-
-sender = "Sender:" mailbox CRLF
-
-reply-to = "Reply-To:" address-list CRLF
-
- The originator fields indicate the mailbox(es) of the source of the
- message. The "From:" field specifies the author(s) of the message,
- that is, the mailbox(es) of the person(s) or system(s) responsible
- for the writing of the message. The "Sender:" field specifies the
- mailbox of the agent responsible for the actual transmission of the
- message. For example, if a secretary were to send a message for
- another person, the mailbox of the secretary would appear in the
- "Sender:" field and the mailbox of the actual author would appear in
- the "From:" field. If the originator of the message can be indicated
- by a single mailbox and the author and transmitter are identical, the
- "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
- appear.
-
- The originator fields also provide the information required when
- replying to a message. When the "Reply-To:" field is present, it
- indicates the mailbox(es) to which the author of the message suggests
- that replies be sent. In the absence of the "Reply-To:" field,
- replies SHOULD by default be sent to the mailbox(es) specified in the
- "From:" field unless otherwise specified by the person composing the
- reply.
-
- In all cases, the "From:" field SHOULD NOT contain any mailbox that
- does not belong to the author(s) of the message. See also section
- 3.6.3 for more information on forming the destination addresses for a
- reply.
-
-
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-
-
-3.6.3. Destination address fields
-
- The destination fields of a message consist of three possible fields,
- each of the same form: The field name, which is either "To", "Cc", or
- "Bcc", followed by a comma-separated list of one or more addresses
- (either mailbox or group syntax).
-
-to = "To:" address-list CRLF
-
-cc = "Cc:" address-list CRLF
-
-bcc = "Bcc:" (address-list / [CFWS]) CRLF
-
- The destination fields specify the recipients of the message. Each
- destination field may have one or more addresses, and each of the
- addresses indicate the intended recipients of the message. The only
- difference between the three fields is how each is used.
-
- The "To:" field contains the address(es) of the primary recipient(s)
- of the message.
-
- The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
- making a copy on a typewriter using carbon paper) contains the
- addresses of others who are to receive the message, though the
- content of the message may not be directed at them.
-
- The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
- addresses of recipients of the message whose addresses are not to be
- revealed to other recipients of the message. There are three ways in
- which the "Bcc:" field is used. In the first case, when a message
- containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
- removed even though all of the recipients (including those specified
- in the "Bcc:" field) are sent a copy of the message. In the second
- case, recipients specified in the "To:" and "Cc:" lines each are sent
- a copy of the message with the "Bcc:" line removed as above, but the
- recipients on the "Bcc:" line get a separate copy of the message
- containing a "Bcc:" line. (When there are multiple recipient
- addresses in the "Bcc:" field, some implementations actually send a
- separate copy of the message to each recipient with a "Bcc:"
- containing only the address of that particular recipient.) Finally,
- since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
- sent without any addresses indicating to the recipients that blind
- copies were sent to someone. Which method to use with "Bcc:" fields
- is implementation dependent, but refer to the "Security
- Considerations" section of this document for a discussion of each.
-
-
-
-
-
-
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-
-
- When a message is a reply to another message, the mailboxes of the
- authors of the original message (the mailboxes in the "From:" field)
- or mailboxes specified in the "Reply-To:" field (if it exists) MAY
- appear in the "To:" field of the reply since these would normally be
- the primary recipients of the reply. If a reply is sent to a message
- that has destination fields, it is often desirable to send a copy of
- the reply to all of the recipients of the message, in addition to the
- author. When such a reply is formed, addresses in the "To:" and
- "Cc:" fields of the original message MAY appear in the "Cc:" field of
- the reply, since these are normally secondary recipients of the
- reply. If a "Bcc:" field is present in the original message,
- addresses in that field MAY appear in the "Bcc:" field of the reply,
- but SHOULD NOT appear in the "To:" or "Cc:" fields.
-
- Note: Some mail applications have automatic reply commands that
- include the destination addresses of the original message in the
- destination addresses of the reply. How those reply commands behave
- is implementation dependent and is beyond the scope of this document.
- In particular, whether or not to include the original destination
- addresses when the original message had a "Reply-To:" field is not
- addressed here.
-
-3.6.4. Identification fields
-
- Though optional, every message SHOULD have a "Message-ID:" field.
- Furthermore, reply messages SHOULD have "In-Reply-To:" and
- "References:" fields as appropriate, as described below.
-
- The "Message-ID:" field contains a single unique message identifier.
- The "References:" and "In-Reply-To:" field each contain one or more
- unique message identifiers, optionally separated by CFWS.
-
- The message identifier (msg-id) is similar in syntax to an angle-addr
- construct without the internal CFWS.
-
-message-id = "Message-ID:" msg-id CRLF
-
-in-reply-to = "In-Reply-To:" 1*msg-id CRLF
-
-references = "References:" 1*msg-id CRLF
-
-msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
-
-id-left = dot-atom-text / no-fold-quote / obs-id-left
-
-id-right = dot-atom-text / no-fold-literal / obs-id-right
-
-no-fold-quote = DQUOTE *(qtext / quoted-pair) DQUOTE
-
-
-
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-
-
-no-fold-literal = "[" *(dtext / quoted-pair) "]"
-
- The "Message-ID:" field provides a unique message identifier that
- refers to a particular version of a particular message. The
- uniqueness of the message identifier is guaranteed by the host that
- generates it (see below). This message identifier is intended to be
- machine readable and not necessarily meaningful to humans. A message
- identifier pertains to exactly one instantiation of a particular
- message; subsequent revisions to the message each receive new message
- identifiers.
-
- Note: There are many instances when messages are "changed", but those
- changes do not constitute a new instantiation of that message, and
- therefore the message would not get a new message identifier. For
- example, when messages are introduced into the transport system, they
- are often prepended with additional header fields such as trace
- fields (described in section 3.6.7) and resent fields (described in
- section 3.6.6). The addition of such header fields does not change
- the identity of the message and therefore the original "Message-ID:"
- field is retained. In all cases, it is the meaning that the sender
- of the message wishes to convey (i.e., whether this is the same
- message or a different message) that determines whether or not the
- "Message-ID:" field changes, not any particular syntactic difference
- that appears (or does not appear) in the message.
-
- The "In-Reply-To:" and "References:" fields are used when creating a
- reply to a message. They hold the message identifier of the original
- message and the message identifiers of other messages (for example,
- in the case of a reply to a message which was itself a reply). The
- "In-Reply-To:" field may be used to identify the message (or
- messages) to which the new message is a reply, while the
- "References:" field may be used to identify a "thread" of
- conversation.
-
- When creating a reply to a message, the "In-Reply-To:" and
- "References:" fields of the resultant message are constructed as
- follows:
-
- The "In-Reply-To:" field will contain the contents of the "Message-
- ID:" field of the message to which this one is a reply (the "parent
- message"). If there is more than one parent message, then the "In-
- Reply-To:" field will contain the contents of all of the parents'
- "Message-ID:" fields. If there is no "Message-ID:" field in any of
- the parent messages, then the new message will have no "In-Reply-To:"
- field.
-
-
-
-
-
-
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-
-
- The "References:" field will contain the contents of the parent's
- "References:" field (if any) followed by the contents of the parent's
- "Message-ID:" field (if any). If the parent message does not contain
- a "References:" field but does have an "In-Reply-To:" field
- containing a single message identifier, then the "References:" field
- will contain the contents of the parent's "In-Reply-To:" field
- followed by the contents of the parent's "Message-ID:" field (if
- any). If the parent has none of the "References:", "In-Reply-To:",
- or "Message-ID:" fields, then the new message will have no
- "References:" field.
-
- Note: Some implementations parse the "References:" field to display
- the "thread of the discussion". These implementations assume that
- each new message is a reply to a single parent and hence that they
- can walk backwards through the "References:" field to find the parent
- of each message listed there. Therefore, trying to form a
- "References:" field for a reply that has multiple parents is
- discouraged and how to do so is not defined in this document.
-
- The message identifier (msg-id) itself MUST be a globally unique
- identifier for a message. The generator of the message identifier
- MUST guarantee that the msg-id is unique. There are several
- algorithms that can be used to accomplish this. Since the msg-id has
- a similar syntax to angle-addr (identical except that comments and
- folding white space are not allowed), a good method is to put the
- domain name (or a domain literal IP address) of the host on which the
- message identifier was created on the right hand side of the "@", and
- put a combination of the current absolute date and time along with
- some other currently unique (perhaps sequential) identifier available
- on the system (for example, a process id number) on the left hand
- side. Using a date on the left hand side and a domain name or domain
- literal on the right hand side makes it possible to guarantee
- uniqueness since no two hosts use the same domain name or IP address
- at the same time. Though other algorithms will work, it is
- RECOMMENDED that the right hand side contain some domain identifier
- (either of the host itself or otherwise) such that the generator of
- the message identifier can guarantee the uniqueness of the left hand
- side within the scope of that domain.
-
- Semantically, the angle bracket characters are not part of the
- msg-id; the msg-id is what is contained between the two angle bracket
- characters.
-
-
-
-
-
-
-
-
-
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-
-
-3.6.5. Informational fields
-
- The informational fields are all optional. The "Keywords:" field
- contains a comma-separated list of one or more words or
- quoted-strings. The "Subject:" and "Comments:" fields are
- unstructured fields as defined in section 2.2.1, and therefore may
- contain text or folding white space.
-
-subject = "Subject:" unstructured CRLF
-
-comments = "Comments:" unstructured CRLF
-
-keywords = "Keywords:" phrase *("," phrase) CRLF
-
- These three fields are intended to have only human-readable content
- with information about the message. The "Subject:" field is the most
- common and contains a short string identifying the topic of the
- message. When used in a reply, the field body MAY start with the
- string "Re: " (from the Latin "res", in the matter of) followed by
- the contents of the "Subject:" field body of the original message.
- If this is done, only one instance of the literal string "Re: " ought
- to be used since use of other strings or more than one instance can
- lead to undesirable consequences. The "Comments:" field contains any
- additional comments on the text of the body of the message. The
- "Keywords:" field contains a comma-separated list of important words
- and phrases that might be useful for the recipient.
-
-3.6.6. Resent fields
-
- Resent fields SHOULD be added to any message that is reintroduced by
- a user into the transport system. A separate set of resent fields
- SHOULD be added each time this is done. All of the resent fields
- corresponding to a particular resending of the message SHOULD be
- together. Each new set of resent fields is prepended to the message;
- that is, the most recent set of resent fields appear earlier in the
- message. No other fields in the message are changed when resent
- fields are added.
-
- Each of the resent fields corresponds to a particular field elsewhere
- in the syntax. For instance, the "Resent-Date:" field corresponds to
- the "Date:" field and the "Resent-To:" field corresponds to the "To:"
- field. In each case, the syntax for the field body is identical to
- the syntax given previously for the corresponding field.
-
- When resent fields are used, the "Resent-From:" and "Resent-Date:"
- fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
- "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
- identical to "Resent-From:".
-
-
-
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-
-RFC 2822 Internet Message Format April 2001
-
-
-resent-date = "Resent-Date:" date-time CRLF
-
-resent-from = "Resent-From:" mailbox-list CRLF
-
-resent-sender = "Resent-Sender:" mailbox CRLF
-
-resent-to = "Resent-To:" address-list CRLF
-
-resent-cc = "Resent-Cc:" address-list CRLF
-
-resent-bcc = "Resent-Bcc:" (address-list / [CFWS]) CRLF
-
-resent-msg-id = "Resent-Message-ID:" msg-id CRLF
-
- Resent fields are used to identify a message as having been
- reintroduced into the transport system by a user. The purpose of
- using resent fields is to have the message appear to the final
- recipient as if it were sent directly by the original sender, with
- all of the original fields remaining the same. Each set of resent
- fields correspond to a particular resending event. That is, if a
- message is resent multiple times, each set of resent fields gives
- identifying information for each individual time. Resent fields are
- strictly informational. They MUST NOT be used in the normal
- processing of replies or other such automatic actions on messages.
-
- Note: Reintroducing a message into the transport system and using
- resent fields is a different operation from "forwarding".
- "Forwarding" has two meanings: One sense of forwarding is that a mail
- reading program can be told by a user to forward a copy of a message
- to another person, making the forwarded message the body of the new
- message. A forwarded message in this sense does not appear to have
- come from the original sender, but is an entirely new message from
- the forwarder of the message. On the other hand, forwarding is also
- used to mean when a mail transport program gets a message and
- forwards it on to a different destination for final delivery. Resent
- header fields are not intended for use with either type of
- forwarding.
-
- The resent originator fields indicate the mailbox of the person(s) or
- system(s) that resent the message. As with the regular originator
- fields, there are two forms: a simple "Resent-From:" form which
- contains the mailbox of the individual doing the resending, and the
- more complex form, when one individual (identified in the
- "Resent-Sender:" field) resends a message on behalf of one or more
- others (identified in the "Resent-From:" field).
-
- Note: When replying to a resent message, replies behave just as they
- would with any other message, using the original "From:",
-
-
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-
-
- "Reply-To:", "Message-ID:", and other fields. The resent fields are
- only informational and MUST NOT be used in the normal processing of
- replies.
-
- The "Resent-Date:" indicates the date and time at which the resent
- message is dispatched by the resender of the message. Like the
- "Date:" field, it is not the date and time that the message was
- actually transported.
-
- The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
- identically to the "To:", "Cc:", and "Bcc:" fields respectively,
- except that they indicate the recipients of the resent message, not
- the recipients of the original message.
-
- The "Resent-Message-ID:" field provides a unique identifier for the
- resent message.
-
-3.6.7. Trace fields
-
- The trace fields are a group of header fields consisting of an
- optional "Return-Path:" field, and one or more "Received:" fields.
- The "Return-Path:" header field contains a pair of angle brackets
- that enclose an optional addr-spec. The "Received:" field contains a
- (possibly empty) list of name/value pairs followed by a semicolon and
- a date-time specification. The first item of the name/value pair is
- defined by item-name, and the second item is either an addr-spec, an
- atom, a domain, or a msg-id. Further restrictions may be applied to
- the syntax of the trace fields by standards that provide for their
- use, such as [RFC2821].
-
-trace = [return]
- 1*received
-
-return = "Return-Path:" path CRLF
-
-path = ([CFWS] "<" ([CFWS] / addr-spec) ">" [CFWS]) /
- obs-path
-
-received = "Received:" name-val-list ";" date-time CRLF
-
-name-val-list = [CFWS] [name-val-pair *(CFWS name-val-pair)]
-
-name-val-pair = item-name CFWS item-value
-
-item-name = ALPHA *(["-"] (ALPHA / DIGIT))
-
-item-value = 1*angle-addr / addr-spec /
- atom / domain / msg-id
-
-
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-
-
- A full discussion of the Internet mail use of trace fields is
- contained in [RFC2821]. For the purposes of this standard, the trace
- fields are strictly informational, and any formal interpretation of
- them is outside of the scope of this document.
-
-3.6.8. Optional fields
-
- Fields may appear in messages that are otherwise unspecified in this
- standard. They MUST conform to the syntax of an optional-field.
- This is a field name, made up of the printable US-ASCII characters
- except SP and colon, followed by a colon, followed by any text which
- conforms to unstructured.
-
- The field names of any optional-field MUST NOT be identical to any
- field name specified elsewhere in this standard.
-
-optional-field = field-name ":" unstructured CRLF
-
-field-name = 1*ftext
-
-ftext = %d33-57 / ; Any character except
- %d59-126 ; controls, SP, and
- ; ":".
-
- For the purposes of this standard, any optional field is
- uninterpreted.
-
-4. Obsolete Syntax
-
- Earlier versions of this standard allowed for different (usually more
- liberal) syntax than is allowed in this version. Also, there have
- been syntactic elements used in messages on the Internet whose
- interpretation have never been documented. Though some of these
- syntactic forms MUST NOT be generated according to the grammar in
- section 3, they MUST be accepted and parsed by a conformant receiver.
- This section documents many of these syntactic elements. Taking the
- grammar in section 3 and adding the definitions presented in this
- section will result in the grammar to use for interpretation of
- messages.
-
- Note: This section identifies syntactic forms that any implementation
- MUST reasonably interpret. However, there are certainly Internet
- messages which do not conform to even the additional syntax given in
- this section. The fact that a particular form does not appear in any
- section of this document is not justification for computer programs
- to crash or for malformed data to be irretrievably lost by any
- implementation. To repeat an example, though this document requires
- lines in messages to be no longer than 998 characters, silently
-
-
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-
-
- discarding the 999th and subsequent characters in a line without
- warning would still be bad behavior for an implementation. It is up
- to the implementation to deal with messages robustly.
-
- One important difference between the obsolete (interpreting) and the
- current (generating) syntax is that in structured header field bodies
- (i.e., between the colon and the CRLF of any structured header
- field), white space characters, including folding white space, and
- comments can be freely inserted between any syntactic tokens. This
- allows many complex forms that have proven difficult for some
- implementations to parse.
-
- Another key difference between the obsolete and the current syntax is
- that the rule in section 3.2.3 regarding lines composed entirely of
- white space in comments and folding white space does not apply. See
- the discussion of folding white space in section 4.2 below.
-
- Finally, certain characters that were formerly allowed in messages
- appear in this section. The NUL character (ASCII value 0) was once
- allowed, but is no longer for compatibility reasons. CR and LF were
- allowed to appear in messages other than as CRLF; this use is also
- shown here.
-
- Other differences in syntax and semantics are noted in the following
- sections.
-
-4.1. Miscellaneous obsolete tokens
-
- These syntactic elements are used elsewhere in the obsolete syntax or
- in the main syntax. The obs-char and obs-qp elements each add ASCII
- value 0. Bare CR and bare LF are added to obs-text and obs-utext.
- The period character is added to obs-phrase. The obs-phrase-list
- provides for "empty" elements in a comma-separated list of phrases.
-
- Note: The "period" (or "full stop") character (".") in obs-phrase is
- not a form that was allowed in earlier versions of this or any other
- standard. Period (nor any other character from specials) was not
- allowed in phrase because it introduced a parsing difficulty
- distinguishing between phrases and portions of an addr-spec (see
- section 4.4). It appears here because the period character is
- currently used in many messages in the display-name portion of
- addresses, especially for initials in names, and therefore must be
- interpreted properly. In the future, period may appear in the
- regular syntax of phrase.
-
-obs-qp = "\" (%d0-127)
-
-obs-text = *LF *CR *(obs-char *LF *CR)
-
-
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-
-
-obs-char = %d0-9 / %d11 / ; %d0-127 except CR and
- %d12 / %d14-127 ; LF
-
-obs-utext = obs-text
-
-obs-phrase = word *(word / "." / CFWS)
-
-obs-phrase-list = phrase / 1*([phrase] [CFWS] "," [CFWS]) [phrase]
-
- Bare CR and bare LF appear in messages with two different meanings.
- In many cases, bare CR or bare LF are used improperly instead of CRLF
- to indicate line separators. In other cases, bare CR and bare LF are
- used simply as ASCII control characters with their traditional ASCII
- meanings.
-
-4.2. Obsolete folding white space
-
- In the obsolete syntax, any amount of folding white space MAY be
- inserted where the obs-FWS rule is allowed. This creates the
- possibility of having two consecutive "folds" in a line, and
- therefore the possibility that a line which makes up a folded header
- field could be composed entirely of white space.
-
- obs-FWS = 1*WSP *(CRLF 1*WSP)
-
-4.3. Obsolete Date and Time
-
- The syntax for the obsolete date format allows a 2 digit year in the
- date field and allows for a list of alphabetic time zone
- specifications that were used in earlier versions of this standard.
- It also permits comments and folding white space between many of the
- tokens.
-
-obs-day-of-week = [CFWS] day-name [CFWS]
-
-obs-year = [CFWS] 2*DIGIT [CFWS]
-
-obs-month = CFWS month-name CFWS
-
-obs-day = [CFWS] 1*2DIGIT [CFWS]
-
-obs-hour = [CFWS] 2DIGIT [CFWS]
-
-obs-minute = [CFWS] 2DIGIT [CFWS]
-
-obs-second = [CFWS] 2DIGIT [CFWS]
-
-obs-zone = "UT" / "GMT" / ; Universal Time
-
-
-
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-
-
- ; North American UT
- ; offsets
- "EST" / "EDT" / ; Eastern: - 5/ - 4
- "CST" / "CDT" / ; Central: - 6/ - 5
- "MST" / "MDT" / ; Mountain: - 7/ - 6
- "PST" / "PDT" / ; Pacific: - 8/ - 7
-
- %d65-73 / ; Military zones - "A"
- %d75-90 / ; through "I" and "K"
- %d97-105 / ; through "Z", both
- %d107-122 ; upper and lower case
-
- Where a two or three digit year occurs in a date, the year is to be
- interpreted as follows: If a two digit year is encountered whose
- value is between 00 and 49, the year is interpreted by adding 2000,
- ending up with a value between 2000 and 2049. If a two digit year is
- encountered with a value between 50 and 99, or any three digit year
- is encountered, the year is interpreted by adding 1900.
-
- In the obsolete time zone, "UT" and "GMT" are indications of
- "Universal Time" and "Greenwich Mean Time" respectively and are both
- semantically identical to "+0000".
-
- The remaining three character zones are the US time zones. The first
- letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
- "Mountain" and "Pacific". The second letter is either "S" for
- "Standard" time, or "D" for "Daylight" (or summer) time. Their
- interpretations are as follows:
-
- EDT is semantically equivalent to -0400
- EST is semantically equivalent to -0500
- CDT is semantically equivalent to -0500
- CST is semantically equivalent to -0600
- MDT is semantically equivalent to -0600
- MST is semantically equivalent to -0700
- PDT is semantically equivalent to -0700
- PST is semantically equivalent to -0800
-
- The 1 character military time zones were defined in a non-standard
- way in [RFC822] and are therefore unpredictable in their meaning.
- The original definitions of the military zones "A" through "I" are
- equivalent to "+0100" through "+0900" respectively; "K", "L", and "M"
- are equivalent to "+1000", "+1100", and "+1200" respectively; "N"
- through "Y" are equivalent to "-0100" through "-1200" respectively;
- and "Z" is equivalent to "+0000". However, because of the error in
- [RFC822], they SHOULD all be considered equivalent to "-0000" unless
- there is out-of-band information confirming their meaning.
-
-
-
-
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-RFC 2822 Internet Message Format April 2001
-
-
- Other multi-character (usually between 3 and 5) alphabetic time zones
- have been used in Internet messages. Any such time zone whose
- meaning is not known SHOULD be considered equivalent to "-0000"
- unless there is out-of-band information confirming their meaning.
-
-4.4. Obsolete Addressing
-
- There are three primary differences in addressing. First, mailbox
- addresses were allowed to have a route portion before the addr-spec
- when enclosed in "<" and ">". The route is simply a comma-separated
- list of domain names, each preceded by "@", and the list terminated
- by a colon. Second, CFWS were allowed between the period-separated
- elements of local-part and domain (i.e., dot-atom was not used). In
- addition, local-part is allowed to contain quoted-string in addition
- to just atom. Finally, mailbox-list and address-list were allowed to
- have "null" members. That is, there could be two or more commas in
- such a list with nothing in between them.
-
-obs-angle-addr = [CFWS] "<" [obs-route] addr-spec ">" [CFWS]
-
-obs-route = [CFWS] obs-domain-list ":" [CFWS]
-
-obs-domain-list = "@" domain *(*(CFWS / "," ) [CFWS] "@" domain)
-
-obs-local-part = word *("." word)
-
-obs-domain = atom *("." atom)
-
-obs-mbox-list = 1*([mailbox] [CFWS] "," [CFWS]) [mailbox]
-
-obs-addr-list = 1*([address] [CFWS] "," [CFWS]) [address]
-
- When interpreting addresses, the route portion SHOULD be ignored.
-
-4.5. Obsolete header fields
-
- Syntactically, the primary difference in the obsolete field syntax is
- that it allows multiple occurrences of any of the fields and they may
- occur in any order. Also, any amount of white space is allowed
- before the ":" at the end of the field name.
-
-obs-fields = *(obs-return /
- obs-received /
- obs-orig-date /
- obs-from /
- obs-sender /
- obs-reply-to /
- obs-to /
-
-
-
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-RFC 2822 Internet Message Format April 2001
-
-
- obs-cc /
- obs-bcc /
- obs-message-id /
- obs-in-reply-to /
- obs-references /
- obs-subject /
- obs-comments /
- obs-keywords /
- obs-resent-date /
- obs-resent-from /
- obs-resent-send /
- obs-resent-rply /
- obs-resent-to /
- obs-resent-cc /
- obs-resent-bcc /
- obs-resent-mid /
- obs-optional)
-
- Except for destination address fields (described in section 4.5.3),
- the interpretation of multiple occurrences of fields is unspecified.
- Also, the interpretation of trace fields and resent fields which do
- not occur in blocks prepended to the message is unspecified as well.
- Unless otherwise noted in the following sections, interpretation of
- other fields is identical to the interpretation of their non-obsolete
- counterparts in section 3.
-
-4.5.1. Obsolete origination date field
-
-obs-orig-date = "Date" *WSP ":" date-time CRLF
-
-4.5.2. Obsolete originator fields
-
-obs-from = "From" *WSP ":" mailbox-list CRLF
-
-obs-sender = "Sender" *WSP ":" mailbox CRLF
-
-obs-reply-to = "Reply-To" *WSP ":" mailbox-list CRLF
-
-4.5.3. Obsolete destination address fields
-
-obs-to = "To" *WSP ":" address-list CRLF
-
-obs-cc = "Cc" *WSP ":" address-list CRLF
-
-obs-bcc = "Bcc" *WSP ":" (address-list / [CFWS]) CRLF
-
-
-
-
-
-
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-RFC 2822 Internet Message Format April 2001
-
-
- When multiple occurrences of destination address fields occur in a
- message, they SHOULD be treated as if the address-list in the first
- occurrence of the field is combined with the address lists of the
- subsequent occurrences by adding a comma and concatenating.
-
-4.5.4. Obsolete identification fields
-
- The obsolete "In-Reply-To:" and "References:" fields differ from the
- current syntax in that they allow phrase (words or quoted strings) to
- appear. The obsolete forms of the left and right sides of msg-id
- allow interspersed CFWS, making them syntactically identical to
- local-part and domain respectively.
-
-obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
-
-obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
-
-obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
-
-obs-id-left = local-part
-
-obs-id-right = domain
-
- For purposes of interpretation, the phrases in the "In-Reply-To:" and
- "References:" fields are ignored.
-
- Semantically, none of the optional CFWS surrounding the local-part
- and the domain are part of the obs-id-left and obs-id-right
- respectively.
-
-4.5.5. Obsolete informational fields
-
-obs-subject = "Subject" *WSP ":" unstructured CRLF
-
-obs-comments = "Comments" *WSP ":" unstructured CRLF
-
-obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
-
-4.5.6. Obsolete resent fields
-
- The obsolete syntax adds a "Resent-Reply-To:" field, which consists
- of the field name, the optional comments and folding white space, the
- colon, and a comma separated list of addresses.
-
-obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
-
-obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
-
-
-
-
-Resnick Standards Track [Page 35]
-
-RFC 2822 Internet Message Format April 2001
-
-
-obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
-
-obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
-
-obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
-
-obs-resent-bcc = "Resent-Bcc" *WSP ":"
- (address-list / [CFWS]) CRLF
-
-obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
-
-obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
-
- As with other resent fields, the "Resent-Reply-To:" field is to be
- treated as trace information only.
-
-4.5.7. Obsolete trace fields
-
- The obs-return and obs-received are again given here as template
- definitions, just as return and received are in section 3. Their
- full syntax is given in [RFC2821].
-
-obs-return = "Return-Path" *WSP ":" path CRLF
-
-obs-received = "Received" *WSP ":" name-val-list CRLF
-
-obs-path = obs-angle-addr
-
-4.5.8. Obsolete optional fields
-
-obs-optional = field-name *WSP ":" unstructured CRLF
-
-5. Security Considerations
-
- Care needs to be taken when displaying messages on a terminal or
- terminal emulator. Powerful terminals may act on escape sequences
- and other combinations of ASCII control characters with a variety of
- consequences. They can remap the keyboard or permit other
- modifications to the terminal which could lead to denial of service
- or even damaged data. They can trigger (sometimes programmable)
- answerback messages which can allow a message to cause commands to be
- issued on the recipient's behalf. They can also effect the operation
- of terminal attached devices such as printers. Message viewers may
- wish to strip potentially dangerous terminal escape sequences from
- the message prior to display. However, other escape sequences appear
- in messages for useful purposes (cf. [RFC2045, RFC2046, RFC2047,
- RFC2048, RFC2049, ISO2022]) and therefore should not be stripped
- indiscriminately.
-
-
-
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-RFC 2822 Internet Message Format April 2001
-
-
- Transmission of non-text objects in messages raises additional
- security issues. These issues are discussed in [RFC2045, RFC2046,
- RFC2047, RFC2048, RFC2049].
-
- Many implementations use the "Bcc:" (blind carbon copy) field
- described in section 3.6.3 to facilitate sending messages to
- recipients without revealing the addresses of one or more of the
- addressees to the other recipients. Mishandling this use of "Bcc:"
- has implications for confidential information that might be revealed,
- which could eventually lead to security problems through knowledge of
- even the existence of a particular mail address. For example, if
- using the first method described in section 3.6.3, where the "Bcc:"
- line is removed from the message, blind recipients have no explicit
- indication that they have been sent a blind copy, except insofar as
- their address does not appear in the message header. Because of
- this, one of the blind addressees could potentially send a reply to
- all of the shown recipients and accidentally reveal that the message
- went to the blind recipient. When the second method from section
- 3.6.3 is used, the blind recipient's address appears in the "Bcc:"
- field of a separate copy of the message. If the "Bcc:" field sent
- contains all of the blind addressees, all of the "Bcc:" recipients
- will be seen by each "Bcc:" recipient. Even if a separate message is
- sent to each "Bcc:" recipient with only the individual's address,
- implementations still need to be careful to process replies to the
- message as per section 3.6.3 so as not to accidentally reveal the
- blind recipient to other recipients.
-
-6. Bibliography
-
- [ASCII] American National Standards Institute (ANSI), Coded
- Character Set - 7-Bit American National Standard Code for
- Information Interchange, ANSI X3.4, 1986.
-
- [ISO2022] International Organization for Standardization (ISO),
- Information processing - ISO 7-bit and 8-bit coded
- character sets - Code extension techniques, Third edition
- - 1986-05-01, ISO 2022, 1986.
-
- [RFC822] Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", RFC 822, August 1982.
-
- [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part One: Format of Internet Message
- Bodies", RFC 2045, November 1996.
-
- [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Two: Media Types", RFC 2046,
- November 1996.
-
-
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-Resnick Standards Track [Page 37]
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-RFC 2822 Internet Message Format April 2001
-
-
- [RFC2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
- Part Three: Message Header Extensions for Non-ASCII Text",
- RFC 2047, November 1996.
-
- [RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
- Internet Mail Extensions (MIME) Part Four: Format of
- Internet Message Bodies", RFC 2048, November 1996.
-
- [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Five: Conformance Criteria and
- Examples", RFC 2049, November 1996.
-
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC2234] Crocker, D., Editor, and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", RFC 2234, November 1997.
-
- [RFC2821] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
- 2821, March 2001.
-
- [STD3] Braden, R., "Host Requirements", STD 3, RFC 1122 and RFC
- 1123, October 1989.
-
- [STD12] Mills, D., "Network Time Protocol", STD 12, RFC 1119,
- September 1989.
-
- [STD13] Mockapetris, P., "Domain Name System", STD 13, RFC 1034
- and RFC 1035, November 1987.
-
- [STD14] Partridge, C., "Mail Routing and the Domain System", STD
- 14, RFC 974, January 1986.
-
-7. Editor's Address
-
- Peter W. Resnick
- QUALCOMM Incorporated
- 5775 Morehouse Drive
- San Diego, CA 92121-1714
- USA
-
- Phone: +1 858 651 4478
- Fax: +1 858 651 1102
- EMail: presnick@qualcomm.com
-
-
-
-
-
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-
-
-8. Acknowledgements
-
- Many people contributed to this document. They included folks who
- participated in the Detailed Revision and Update of Messaging
- Standards (DRUMS) Working Group of the Internet Engineering Task
- Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
- people who simply sent their comments in via e-mail. The editor is
- deeply indebted to them all and thanks them sincerely. The below
- list includes everyone who sent e-mail concerning this document.
- Hopefully, everyone who contributed is named here:
-
- Matti Aarnio Barry Finkel Larry Masinter
- Tanaka Akira Erik Forsberg Denis McKeon
- Russ Allbery Chuck Foster William P McQuillan
- Eric Allman Paul Fox Alexey Melnikov
- Harald Tveit Alvestrand Klaus M. Frank Perry E. Metzger
- Ran Atkinson Ned Freed Steven Miller
- Jos Backus Jochen Friedrich Keith Moore
- Bruce Balden Randall C. Gellens John Gardiner Myers
- Dave Barr Sukvinder Singh Gill Chris Newman
- Alan Barrett Tim Goodwin John W. Noerenberg
- John Beck Philip Guenther Eric Norman
- J. Robert von Behren Tony Hansen Mike O'Dell
- Jos den Bekker John Hawkinson Larry Osterman
- D. J. Bernstein Philip Hazel Paul Overell
- James Berriman Kai Henningsen Jacob Palme
- Norbert Bollow Robert Herriot Michael A. Patton
- Raj Bose Paul Hethmon Uzi Paz
- Antony Bowesman Jim Hill Michael A. Quinlan
- Scott Bradner Paul E. Hoffman Eric S. Raymond
- Randy Bush Steve Hole Sam Roberts
- Tom Byrer Kari Hurtta Hugh Sasse
- Bruce Campbell Marco S. Hyman Bart Schaefer
- Larry Campbell Ofer Inbar Tom Scola
- W. J. Carpenter Olle Jarnefors Wolfgang Segmuller
- Michael Chapman Kevin Johnson Nick Shelness
- Richard Clayton Sudish Joseph John Stanley
- Maurizio Codogno Maynard Kang Einar Stefferud
- Jim Conklin Prabhat Keni Jeff Stephenson
- R. Kelley Cook John C. Klensin Bernard Stern
- Steve Coya Graham Klyne Peter Sylvester
- Mark Crispin Brad Knowles Mark Symons
- Dave Crocker Shuhei Kobayashi Eric Thomas
- Matt Curtin Peter Koch Lee Thompson
- Michael D'Errico Dan Kohn Karel De Vriendt
- Cyrus Daboo Christian Kuhtz Matthew Wall
- Jutta Degener Anand Kumria Rolf Weber
- Mark Delany Steen Larsen Brent B. Welch
-
-
-
-Resnick Standards Track [Page 39]
-
-RFC 2822 Internet Message Format April 2001
-
-
- Steve Dorner Eliot Lear Dan Wing
- Harold A. Driscoll Barry Leiba Jack De Winter
- Michael Elkins Jay Levitt Gregory J. Woodhouse
- Robert Elz Lars-Johan Liman Greg A. Woods
- Johnny Eriksson Charles Lindsey Kazu Yamamoto
- Erik E. Fair Pete Loshin Alain Zahm
- Roger Fajman Simon Lyall Jamie Zawinski
- Patrik Faltstrom Bill Manning Timothy S. Zurcher
- Claus Andre Farber John Martin
-
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-RFC 2822 Internet Message Format April 2001
-
-
-Appendix A. Example messages
-
- This section presents a selection of messages. These are intended to
- assist in the implementation of this standard, but should not be
- taken as normative; that is to say, although the examples in this
- section were carefully reviewed, if there happens to be a conflict
- between these examples and the syntax described in sections 3 and 4
- of this document, the syntax in those sections is to be taken as
- correct.
-
- Messages are delimited in this section between lines of "----". The
- "----" lines are not part of the message itself.
-
-A.1. Addressing examples
-
- The following are examples of messages that might be sent between two
- individuals.
-
-A.1.1. A message from one person to another with simple addressing
-
- This could be called a canonical message. It has a single author,
- John Doe, a single recipient, Mary Smith, a subject, the date, a
- message identifier, and a textual message in the body.
-
-----
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 41]
-
-RFC 2822 Internet Message Format April 2001
-
-
- If John's secretary Michael actually sent the message, though John
- was the author and replies to this message should go back to him, the
- sender field would be used:
-
-----
-From: John Doe <jdoe@machine.example>
-Sender: Michael Jones <mjones@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-A.1.2. Different types of mailboxes
-
- This message includes multiple addresses in the destination fields
- and also uses several different forms of addresses.
-
-----
-From: "Joe Q. Public" <john.q.public@example.com>
-To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
-Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
-Date: Tue, 1 Jul 2003 10:52:37 +0200
-Message-ID: <5678.21-Nov-1997@example.com>
-
-Hi everyone.
-----
-
- Note that the display names for Joe Q. Public and Giant; "Big" Box
- needed to be enclosed in double-quotes because the former contains
- the period and the latter contains both semicolon and double-quote
- characters (the double-quote characters appearing as quoted-pair
- construct). Conversely, the display name for Who? could appear
- without them because the question mark is legal in an atom. Notice
- also that jdoe@example.org and boss@nil.test have no display names
- associated with them at all, and jdoe@example.org uses the simpler
- address form without the angle brackets.
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 42]
-
-RFC 2822 Internet Message Format April 2001
-
-
-A.1.3. Group addresses
-
-----
-From: Pete <pete@silly.example>
-To: A Group:Chris Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
-Cc: Undisclosed recipients:;
-Date: Thu, 13 Feb 1969 23:32:54 -0330
-Message-ID: <testabcd.1234@silly.example>
-
-Testing.
-----
-
- In this message, the "To:" field has a single group recipient named A
- Group which contains 3 addresses, and a "Cc:" field with an empty
- group recipient named Undisclosed recipients.
-
-A.2. Reply messages
-
- The following is a series of three messages that make up a
- conversation thread between John and Mary. John firsts sends a
- message to Mary, Mary then replies to John's message, and then John
- replies to Mary's reply message.
-
- Note especially the "Message-ID:", "References:", and "In-Reply-To:"
- fields in each message.
-
-----
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 43]
-
-RFC 2822 Internet Message Format April 2001
-
-
- When sending replies, the Subject field is often retained, though
- prepended with "Re: " as described in section 3.6.5.
-
-----
-From: Mary Smith <mary@example.net>
-To: John Doe <jdoe@machine.example>
-Reply-To: "Mary Smith: Personal Account" <smith@home.example>
-Subject: Re: Saying Hello
-Date: Fri, 21 Nov 1997 10:01:10 -0600
-Message-ID: <3456@example.net>
-In-Reply-To: <1234@local.machine.example>
-References: <1234@local.machine.example>
-
-This is a reply to your hello.
-----
-
- Note the "Reply-To:" field in the above message. When John replies
- to Mary's message above, the reply should go to the address in the
- "Reply-To:" field instead of the address in the "From:" field.
-
-----
-To: "Mary Smith: Personal Account" <smith@home.example>
-From: John Doe <jdoe@machine.example>
-Subject: Re: Saying Hello
-Date: Fri, 21 Nov 1997 11:00:00 -0600
-Message-ID: <abcd.1234@local.machine.tld>
-In-Reply-To: <3456@example.net>
-References: <1234@local.machine.example> <3456@example.net>
-
-This is a reply to your reply.
-----
-
-A.3. Resent messages
-
- Start with the message that has been used as an example several
- times:
-
-----
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-
-
-
-Resnick Standards Track [Page 44]
-
-RFC 2822 Internet Message Format April 2001
-
-
- Say that Mary, upon receiving this message, wishes to send a copy of
- the message to Jane such that (a) the message would appear to have
- come straight from John; (b) if Jane replies to the message, the
- reply should go back to John; and (c) all of the original
- information, like the date the message was originally sent to Mary,
- the message identifier, and the original addressee, is preserved. In
- this case, resent fields are prepended to the message:
-
-----
-Resent-From: Mary Smith <mary@example.net>
-Resent-To: Jane Brown <j-brown@other.example>
-Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
-Resent-Message-ID: <78910@example.net>
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
- If Jane, in turn, wished to resend this message to another person,
- she would prepend her own set of resent header fields to the above
- and send that.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 45]
-
-RFC 2822 Internet Message Format April 2001
-
-
-A.4. Messages with trace fields
-
- As messages are sent through the transport system as described in
- [RFC2821], trace fields are prepended to the message. The following
- is an example of what those trace fields might look like. Note that
- there is some folding white space in the first one since these lines
- can be long.
-
-----
-Received: from x.y.test
- by example.net
- via TCP
- with ESMTP
- id ABC12345
- for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
-Received: from machine.example by x.y.test; 21 Nov 1997 10:01:22 -0600
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: Fri, 21 Nov 1997 09:55:06 -0600
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 46]
-
-RFC 2822 Internet Message Format April 2001
-
-
-A.5. White space, comments, and other oddities
-
- White space, including folding white space, and comments can be
- inserted between many of the tokens of fields. Taking the example
- from A.1.3, white space and comments can be inserted into all of the
- fields.
-
-----
-From: Pete(A wonderful \) chap) <pete(his account)@silly.test(his host)>
-To:A Group(Some people)
- :Chris Jones <c@(Chris's host.)public.example>,
- joe@example.org,
- John <jdoe@one.test> (my dear friend); (the end of the group)
-Cc:(Empty list)(start)Undisclosed recipients :(nobody(that I know)) ;
-Date: Thu,
- 13
- Feb
- 1969
- 23:32
- -0330 (Newfoundland Time)
-Message-ID: <testabcd.1234@silly.test>
-
-Testing.
-----
-
- The above example is aesthetically displeasing, but perfectly legal.
- Note particularly (1) the comments in the "From:" field (including
- one that has a ")" character appearing as part of a quoted-pair); (2)
- the white space absent after the ":" in the "To:" field as well as
- the comment and folding white space after the group name, the special
- character (".") in the comment in Chris Jones's address, and the
- folding white space before and after "joe@example.org,"; (3) the
- multiple and nested comments in the "Cc:" field as well as the
- comment immediately following the ":" after "Cc"; (4) the folding
- white space (but no comments except at the end) and the missing
- seconds in the time of the date field; and (5) the white space before
- (but not within) the identifier in the "Message-ID:" field.
-
-A.6. Obsoleted forms
-
- The following are examples of obsolete (that is, the "MUST NOT
- generate") syntactic elements described in section 4 of this
- document.
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 47]
-
-RFC 2822 Internet Message Format April 2001
-
-
-A.6.1. Obsolete addressing
-
- Note in the below example the lack of quotes around Joe Q. Public,
- the route that appears in the address for Mary Smith, the two commas
- that appear in the "To:" field, and the spaces that appear around the
- "." in the jdoe address.
-
-----
-From: Joe Q. Public <john.q.public@example.com>
-To: Mary Smith <@machine.tld:mary@example.net>, , jdoe@test . example
-Date: Tue, 1 Jul 2003 10:52:37 +0200
-Message-ID: <5678.21-Nov-1997@example.com>
-
-Hi everyone.
-----
-
-A.6.2. Obsolete dates
-
- The following message uses an obsolete date format, including a non-
- numeric time zone and a two digit year. Note that although the
- day-of-week is missing, that is not specific to the obsolete syntax;
- it is optional in the current syntax as well.
-
-----
-From: John Doe <jdoe@machine.example>
-To: Mary Smith <mary@example.net>
-Subject: Saying Hello
-Date: 21 Nov 97 09:55:06 GMT
-Message-ID: <1234@local.machine.example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
-A.6.3. Obsolete white space and comments
-
- White space and comments can appear between many more elements than
- in the current syntax. Also, folding lines that are made up entirely
- of white space are legal.
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 48]
-
-RFC 2822 Internet Message Format April 2001
-
-
-----
-From : John Doe <jdoe@machine(comment). example>
-To : Mary Smith
-__
- <mary@example.net>
-Subject : Saying Hello
-Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
-Message-ID : <1234 @ local(blah) .machine .example>
-
-This is a message just to say hello.
-So, "Hello".
-----
-
- Note especially the second line of the "To:" field. It starts with
- two space characters. (Note that "__" represent blank spaces.)
- Therefore, it is considered part of the folding as described in
- section 4.2. Also, the comments and white space throughout
- addresses, dates, and message identifiers are all part of the
- obsolete syntax.
-
-Appendix B. Differences from earlier standards
-
- This appendix contains a list of changes that have been made in the
- Internet Message Format from earlier standards, specifically [RFC822]
- and [STD3]. Items marked with an asterisk (*) below are items which
- appear in section 4 of this document and therefore can no longer be
- generated.
-
- 1. Period allowed in obsolete form of phrase.
- 2. ABNF moved out of document to [RFC2234].
- 3. Four or more digits allowed for year.
- 4. Header field ordering (and lack thereof) made explicit.
- 5. Encrypted header field removed.
- 6. Received syntax loosened to allow any token/value pair.
- 7. Specifically allow and give meaning to "-0000" time zone.
- 8. Folding white space is not allowed between every token.
- 9. Requirement for destinations removed.
- 10. Forwarding and resending redefined.
- 11. Extension header fields no longer specifically called out.
- 12. ASCII 0 (null) removed.*
- 13. Folding continuation lines cannot contain only white space.*
- 14. Free insertion of comments not allowed in date.*
- 15. Non-numeric time zones not allowed.*
- 16. Two digit years not allowed.*
- 17. Three digit years interpreted, but not allowed for generation.
- 18. Routes in addresses not allowed.*
- 19. CFWS within local-parts and domains not allowed.*
- 20. Empty members of address lists not allowed.*
-
-
-
-Resnick Standards Track [Page 49]
-
-RFC 2822 Internet Message Format April 2001
-
-
- 21. Folding white space between field name and colon not allowed.*
- 22. Comments between field name and colon not allowed.
- 23. Tightened syntax of in-reply-to and references.*
- 24. CFWS within msg-id not allowed.*
- 25. Tightened semantics of resent fields as informational only.
- 26. Resent-Reply-To not allowed.*
- 27. No multiple occurrences of fields (except resent and received).*
- 28. Free CR and LF not allowed.*
- 29. Routes in return path not allowed.*
- 30. Line length limits specified.
- 31. Bcc more clearly specified.
-
-Appendix C. Notices
-
- Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- intellectual property or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; neither does it represent that it
- has made any effort to identify any such rights. Information on the
- IETF's procedures with respect to rights in standards-track and
- standards-related documentation can be found in BCP-11. Copies of
- claims of rights made available for publication and any assurances of
- licenses to be made available, or the result of an attempt made to
- obtain a general license or permission for the use of such
- proprietary rights by implementors or users of this specification can
- be obtained from the IETF Secretariat.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 50]
-
-RFC 2822 Internet Message Format April 2001
-
-
-Full Copyright Statement
-
- Copyright (C) The Internet Society (2001). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 51]
-
diff --git a/proto/rfc3501.txt b/proto/rfc3501.txt
@@ -1,6051 +0,0 @@
-
-
-
-
-
-
-Network Working Group M. Crispin
-Request for Comments: 3501 University of Washington
-Obsoletes: 2060 March 2003
-Category: Standards Track
-
-
- INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2003). All Rights Reserved.
-
-Abstract
-
- The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1)
- allows a client to access and manipulate electronic mail messages on
- a server. IMAP4rev1 permits manipulation of mailboxes (remote
- message folders) in a way that is functionally equivalent to local
- folders. IMAP4rev1 also provides the capability for an offline
- client to resynchronize with the server.
-
- IMAP4rev1 includes operations for creating, deleting, and renaming
- mailboxes, checking for new messages, permanently removing messages,
- setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching,
- and selective fetching of message attributes, texts, and portions
- thereof. Messages in IMAP4rev1 are accessed by the use of numbers.
- These numbers are either message sequence numbers or unique
- identifiers.
-
- IMAP4rev1 supports a single server. A mechanism for accessing
- configuration information to support multiple IMAP4rev1 servers is
- discussed in RFC 2244.
-
- IMAP4rev1 does not specify a means of posting mail; this function is
- handled by a mail transfer protocol such as RFC 2821.
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 1]
-
-RFC 3501 IMAPv4 March 2003
-
-
-Table of Contents
-
- IMAP4rev1 Protocol Specification ................................ 4
- 1. How to Read This Document ............................... 4
- 1.1. Organization of This Document ........................... 4
- 1.2. Conventions Used in This Document ....................... 4
- 1.3. Special Notes to Implementors ........................... 5
- 2. Protocol Overview ....................................... 6
- 2.1. Link Level .............................................. 6
- 2.2. Commands and Responses .................................. 6
- 2.2.1. Client Protocol Sender and Server Protocol Receiver ..... 6
- 2.2.2. Server Protocol Sender and Client Protocol Receiver ..... 7
- 2.3. Message Attributes ...................................... 8
- 2.3.1. Message Numbers ......................................... 8
- 2.3.1.1. Unique Identifier (UID) Message Attribute ....... 8
- 2.3.1.2. Message Sequence Number Message Attribute ....... 10
- 2.3.2. Flags Message Attribute ................................. 11
- 2.3.3. Internal Date Message Attribute ......................... 12
- 2.3.4. [RFC-2822] Size Message Attribute ....................... 12
- 2.3.5. Envelope Structure Message Attribute .................... 12
- 2.3.6. Body Structure Message Attribute ........................ 12
- 2.4. Message Texts ........................................... 13
- 3. State and Flow Diagram .................................. 13
- 3.1. Not Authenticated State ................................. 13
- 3.2. Authenticated State ..................................... 13
- 3.3. Selected State .......................................... 13
- 3.4. Logout State ............................................ 14
- 4. Data Formats ............................................ 16
- 4.1. Atom .................................................... 16
- 4.2. Number .................................................. 16
- 4.3. String .................................................. 16
- 4.3.1. 8-bit and Binary Strings ................................ 17
- 4.4. Parenthesized List ...................................... 17
- 4.5. NIL ..................................................... 17
- 5. Operational Considerations .............................. 18
- 5.1. Mailbox Naming .......................................... 18
- 5.1.1. Mailbox Hierarchy Naming ................................ 19
- 5.1.2. Mailbox Namespace Naming Convention ..................... 19
- 5.1.3. Mailbox International Naming Convention ................. 19
- 5.2. Mailbox Size and Message Status Updates ................. 21
- 5.3. Response when no Command in Progress .................... 21
- 5.4. Autologout Timer ........................................ 22
- 5.5. Multiple Commands in Progress ........................... 22
- 6. Client Commands ........................................ 23
- 6.1. Client Commands - Any State ............................ 24
- 6.1.1. CAPABILITY Command ..................................... 24
- 6.1.2. NOOP Command ........................................... 25
- 6.1.3. LOGOUT Command ......................................... 26
-
-
-
-Crispin Standards Track [Page 2]
-
-RFC 3501 IMAPv4 March 2003
-
-
- 6.2. Client Commands - Not Authenticated State .............. 26
- 6.2.1. STARTTLS Command ....................................... 27
- 6.2.2. AUTHENTICATE Command ................................... 28
- 6.2.3. LOGIN Command .......................................... 30
- 6.3. Client Commands - Authenticated State .................. 31
- 6.3.1. SELECT Command ......................................... 32
- 6.3.2. EXAMINE Command ........................................ 34
- 6.3.3. CREATE Command ......................................... 34
- 6.3.4. DELETE Command ......................................... 35
- 6.3.5. RENAME Command ......................................... 37
- 6.3.6. SUBSCRIBE Command ...................................... 39
- 6.3.7. UNSUBSCRIBE Command .................................... 39
- 6.3.8. LIST Command ........................................... 40
- 6.3.9. LSUB Command ........................................... 43
- 6.3.10. STATUS Command ......................................... 44
- 6.3.11. APPEND Command ......................................... 46
- 6.4. Client Commands - Selected State ....................... 47
- 6.4.1. CHECK Command .......................................... 47
- 6.4.2. CLOSE Command .......................................... 48
- 6.4.3. EXPUNGE Command ........................................ 49
- 6.4.4. SEARCH Command ......................................... 49
- 6.4.5. FETCH Command .......................................... 54
- 6.4.6. STORE Command .......................................... 58
- 6.4.7. COPY Command ........................................... 59
- 6.4.8. UID Command ............................................ 60
- 6.5. Client Commands - Experimental/Expansion ............... 62
- 6.5.1. X<atom> Command ........................................ 62
- 7. Server Responses ....................................... 62
- 7.1. Server Responses - Status Responses .................... 63
- 7.1.1. OK Response ............................................ 65
- 7.1.2. NO Response ............................................ 66
- 7.1.3. BAD Response ........................................... 66
- 7.1.4. PREAUTH Response ....................................... 67
- 7.1.5. BYE Response ........................................... 67
- 7.2. Server Responses - Server and Mailbox Status ........... 68
- 7.2.1. CAPABILITY Response .................................... 68
- 7.2.2. LIST Response .......................................... 69
- 7.2.3. LSUB Response .......................................... 70
- 7.2.4 STATUS Response ........................................ 70
- 7.2.5. SEARCH Response ........................................ 71
- 7.2.6. FLAGS Response ......................................... 71
- 7.3. Server Responses - Mailbox Size ........................ 71
- 7.3.1. EXISTS Response ........................................ 71
- 7.3.2. RECENT Response ........................................ 72
- 7.4. Server Responses - Message Status ...................... 72
- 7.4.1. EXPUNGE Response ....................................... 72
- 7.4.2. FETCH Response ......................................... 73
- 7.5. Server Responses - Command Continuation Request ........ 79
-
-
-
-Crispin Standards Track [Page 3]
-
-RFC 3501 IMAPv4 March 2003
-
-
- 8. Sample IMAP4rev1 connection ............................ 80
- 9. Formal Syntax .......................................... 81
- 10. Author's Note .......................................... 92
- 11. Security Considerations ................................ 92
- 11.1. STARTTLS Security Considerations ....................... 92
- 11.2. Other Security Considerations .......................... 93
- 12. IANA Considerations .................................... 94
- Appendices ..................................................... 95
- A. References ............................................. 95
- B. Changes from RFC 2060 .................................. 97
- C. Key Word Index ......................................... 103
- Author's Address ............................................... 107
- Full Copyright Statement ....................................... 108
-
-IMAP4rev1 Protocol Specification
-
-1. How to Read This Document
-
-1.1. Organization of This Document
-
- This document is written from the point of view of the implementor of
- an IMAP4rev1 client or server. Beyond the protocol overview in
- section 2, it is not optimized for someone trying to understand the
- operation of the protocol. The material in sections 3 through 5
- provides the general context and definitions with which IMAP4rev1
- operates.
-
- Sections 6, 7, and 9 describe the IMAP commands, responses, and
- syntax, respectively. The relationships among these are such that it
- is almost impossible to understand any of them separately. In
- particular, do not attempt to deduce command syntax from the command
- section alone; instead refer to the Formal Syntax section.
-
-1.2. Conventions Used in This Document
-
- "Conventions" are basic principles or procedures. Document
- conventions are noted in this section.
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server respectively.
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
- be interpreted as described in [KEYWORDS].
-
- The word "can" (not "may") is used to refer to a possible
- circumstance or situation, as opposed to an optional facility of the
- protocol.
-
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-
- "User" is used to refer to a human user, whereas "client" refers to
- the software being run by the user.
-
- "Connection" refers to the entire sequence of client/server
- interaction from the initial establishment of the network connection
- until its termination.
-
- "Session" refers to the sequence of client/server interaction from
- the time that a mailbox is selected (SELECT or EXAMINE command) until
- the time that selection ends (SELECT or EXAMINE of another mailbox,
- CLOSE command, or connection termination).
-
- Characters are 7-bit US-ASCII unless otherwise specified. Other
- character sets are indicated using a "CHARSET", as described in
- [MIME-IMT] and defined in [CHARSET]. CHARSETs have important
- additional semantics in addition to defining character set; refer to
- these documents for more detail.
-
- There are several protocol conventions in IMAP. These refer to
- aspects of the specification which are not strictly part of the IMAP
- protocol, but reflect generally-accepted practice. Implementations
- need to be aware of these conventions, and avoid conflicts whether or
- not they implement the convention. For example, "&" may not be used
- as a hierarchy delimiter since it conflicts with the Mailbox
- International Naming Convention, and other uses of "&" in mailbox
- names are impacted as well.
-
-1.3. Special Notes to Implementors
-
- Implementors of the IMAP protocol are strongly encouraged to read the
- IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
- conjunction with this document, to help understand the intricacies of
- this protocol and how best to build an interoperable product.
-
- IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
- unpublished IMAP2bis protocols. IMAP4rev1 is largely compatible with
- the IMAP4 protocol described in RFC 1730; the exception being in
- certain facilities added in RFC 1730 that proved problematic and were
- subsequently removed. In the course of the evolution of IMAP4rev1,
- some aspects in the earlier protocols have become obsolete. Obsolete
- commands, responses, and data formats which an IMAP4rev1
- implementation can encounter when used with an earlier implementation
- are described in [IMAP-OBSOLETE].
-
- Other compatibility issues with IMAP2bis, the most common variant of
- the earlier protocol, are discussed in [IMAP-COMPAT]. A full
- discussion of compatibility issues with rare (and presumed extinct)
-
-
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-
- variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
- primarily of historical interest.
-
- IMAP was originally developed for the older [RFC-822] standard, and
- as a consequence several fetch items in IMAP incorporate "RFC822" in
- their name. With the exception of RFC822.SIZE, there are more modern
- replacements; for example, the modern version of RFC822.HEADER is
- BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a
- reference to the updated [RFC-2822] standard.
-
-2. Protocol Overview
-
-2.1. Link Level
-
- The IMAP4rev1 protocol assumes a reliable data stream such as that
- provided by TCP. When TCP is used, an IMAP4rev1 server listens on
- port 143.
-
-2.2. Commands and Responses
-
- An IMAP4rev1 connection consists of the establishment of a
- client/server network connection, an initial greeting from the
- server, and client/server interactions. These client/server
- interactions consist of a client command, server data, and a server
- completion result response.
-
- All interactions transmitted by client and server are in the form of
- lines, that is, strings that end with a CRLF. The protocol receiver
- of an IMAP4rev1 client or server is either reading a line, or is
- reading a sequence of octets with a known count followed by a line.
-
-2.2.1. Client Protocol Sender and Server Protocol Receiver
-
- The client command begins an operation. Each client command is
- prefixed with an identifier (typically a short alphanumeric string,
- e.g., A0001, A0002, etc.) called a "tag". A different tag is
- generated by the client for each command.
-
- Clients MUST follow the syntax outlined in this specification
- strictly. It is a syntax error to send a command with missing or
- extraneous spaces or arguments.
-
- There are two cases in which a line from the client does not
- represent a complete command. In one case, a command argument is
- quoted with an octet count (see the description of literal in String
- under Data Formats); in the other case, the command arguments require
- server feedback (see the AUTHENTICATE command). In either case, the
-
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- server sends a command continuation request response if it is ready
- for the octets (if appropriate) and the remainder of the command.
- This response is prefixed with the token "+".
-
- Note: If instead, the server detected an error in the
- command, it sends a BAD completion response with a tag
- matching the command (as described below) to reject the
- command and prevent the client from sending any more of the
- command.
-
- It is also possible for the server to send a completion
- response for some other command (if multiple commands are
- in progress), or untagged data. In either case, the
- command continuation request is still pending; the client
- takes the appropriate action for the response, and reads
- another response from the server. In all cases, the client
- MUST send a complete command (including receiving all
- command continuation request responses and command
- continuations for the command) before initiating a new
- command.
-
- The protocol receiver of an IMAP4rev1 server reads a command line
- from the client, parses the command and its arguments, and transmits
- server data and a server command completion result response.
-
-2.2.2. Server Protocol Sender and Client Protocol Receiver
-
- Data transmitted by the server to the client and status responses
- that do not indicate command completion are prefixed with the token
- "*", and are called untagged responses.
-
- Server data MAY be sent as a result of a client command, or MAY be
- sent unilaterally by the server. There is no syntactic difference
- between server data that resulted from a specific command and server
- data that were sent unilaterally.
-
- The server completion result response indicates the success or
- failure of the operation. It is tagged with the same tag as the
- client command which began the operation. Thus, if more than one
- command is in progress, the tag in a server completion response
- identifies the command to which the response applies. There are
- three possible server completion responses: OK (indicating success),
- NO (indicating failure), or BAD (indicating a protocol error such as
- unrecognized command or command syntax error).
-
- Servers SHOULD enforce the syntax outlined in this specification
- strictly. Any client command with a protocol syntax error, including
- (but not limited to) missing or extraneous spaces or arguments,
-
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-
- SHOULD be rejected, and the client given a BAD server completion
- response.
-
- The protocol receiver of an IMAP4rev1 client reads a response line
- from the server. It then takes action on the response based upon the
- first token of the response, which can be a tag, a "*", or a "+".
-
- A client MUST be prepared to accept any server response at all times.
- This includes server data that was not requested. Server data SHOULD
- be recorded, so that the client can reference its recorded copy
- rather than sending a command to the server to request the data. In
- the case of certain server data, the data MUST be recorded.
-
- This topic is discussed in greater detail in the Server Responses
- section.
-
-2.3. Message Attributes
-
- In addition to message text, each message has several attributes
- associated with it. These attributes can be retrieved individually
- or in conjunction with other attributes or message texts.
-
-2.3.1. Message Numbers
-
- Messages in IMAP4rev1 are accessed by one of two numbers; the unique
- identifier or the message sequence number.
-
-
-2.3.1.1. Unique Identifier (UID) Message Attribute
-
- A 32-bit value assigned to each message, which when used with the
- unique identifier validity value (see below) forms a 64-bit value
- that MUST NOT refer to any other message in the mailbox or any
- subsequent mailbox with the same name forever. Unique identifiers
- are assigned in a strictly ascending fashion in the mailbox; as each
- message is added to the mailbox it is assigned a higher UID than the
- message(s) which were added previously. Unlike message sequence
- numbers, unique identifiers are not necessarily contiguous.
-
- The unique identifier of a message MUST NOT change during the
- session, and SHOULD NOT change between sessions. Any change of
- unique identifiers between sessions MUST be detectable using the
- UIDVALIDITY mechanism discussed below. Persistent unique identifiers
- are required for a client to resynchronize its state from a previous
- session with the server (e.g., disconnected or offline access
- clients); this is discussed further in [IMAP-DISC].
-
-
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-
- Associated with every mailbox are two values which aid in unique
- identifier handling: the next unique identifier value and the unique
- identifier validity value.
-
- The next unique identifier value is the predicted value that will be
- assigned to a new message in the mailbox. Unless the unique
- identifier validity also changes (see below), the next unique
- identifier value MUST have the following two characteristics. First,
- the next unique identifier value MUST NOT change unless new messages
- are added to the mailbox; and second, the next unique identifier
- value MUST change whenever new messages are added to the mailbox,
- even if those new messages are subsequently expunged.
-
- Note: The next unique identifier value is intended to
- provide a means for a client to determine whether any
- messages have been delivered to the mailbox since the
- previous time it checked this value. It is not intended to
- provide any guarantee that any message will have this
- unique identifier. A client can only assume, at the time
- that it obtains the next unique identifier value, that
- messages arriving after that time will have a UID greater
- than or equal to that value.
-
- The unique identifier validity value is sent in a UIDVALIDITY
- response code in an OK untagged response at mailbox selection time.
- If unique identifiers from an earlier session fail to persist in this
- session, the unique identifier validity value MUST be greater than
- the one used in the earlier session.
-
- Note: Ideally, unique identifiers SHOULD persist at all
- times. Although this specification recognizes that failure
- to persist can be unavoidable in certain server
- environments, it STRONGLY ENCOURAGES message store
- implementation techniques that avoid this problem. For
- example:
-
- 1) Unique identifiers MUST be strictly ascending in the
- mailbox at all times. If the physical message store is
- re-ordered by a non-IMAP agent, this requires that the
- unique identifiers in the mailbox be regenerated, since
- the former unique identifiers are no longer strictly
- ascending as a result of the re-ordering.
-
- 2) If the message store has no mechanism to store unique
- identifiers, it must regenerate unique identifiers at
- each session, and each session must have a unique
- UIDVALIDITY value.
-
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-
- 3) If the mailbox is deleted and a new mailbox with the
- same name is created at a later date, the server must
- either keep track of unique identifiers from the
- previous instance of the mailbox, or it must assign a
- new UIDVALIDITY value to the new instance of the
- mailbox. A good UIDVALIDITY value to use in this case
- is a 32-bit representation of the creation date/time of
- the mailbox. It is alright to use a constant such as
- 1, but only if it guaranteed that unique identifiers
- will never be reused, even in the case of a mailbox
- being deleted (or renamed) and a new mailbox by the
- same name created at some future time.
-
- 4) The combination of mailbox name, UIDVALIDITY, and UID
- must refer to a single immutable message on that server
- forever. In particular, the internal date, [RFC-2822]
- size, envelope, body structure, and message texts
- (RFC822, RFC822.HEADER, RFC822.TEXT, and all BODY[...]
- fetch data items) must never change. This does not
- include message numbers, nor does it include attributes
- that can be set by a STORE command (e.g., FLAGS).
-
-
-2.3.1.2. Message Sequence Number Message Attribute
-
- A relative position from 1 to the number of messages in the mailbox.
- This position MUST be ordered by ascending unique identifier. As
- each new message is added, it is assigned a message sequence number
- that is 1 higher than the number of messages in the mailbox before
- that new message was added.
-
- Message sequence numbers can be reassigned during the session. For
- example, when a message is permanently removed (expunged) from the
- mailbox, the message sequence number for all subsequent messages is
- decremented. The number of messages in the mailbox is also
- decremented. Similarly, a new message can be assigned a message
- sequence number that was once held by some other message prior to an
- expunge.
-
- In addition to accessing messages by relative position in the
- mailbox, message sequence numbers can be used in mathematical
- calculations. For example, if an untagged "11 EXISTS" is received,
- and previously an untagged "8 EXISTS" was received, three new
- messages have arrived with message sequence numbers of 9, 10, and 11.
- Another example, if message 287 in a 523 message mailbox has UID
- 12345, there are exactly 286 messages which have lesser UIDs and 236
- messages which have greater UIDs.
-
-
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-
-2.3.2. Flags Message Attribute
-
- A list of zero or more named tokens associated with the message. A
- flag is set by its addition to this list, and is cleared by its
- removal. There are two types of flags in IMAP4rev1. A flag of
- either type can be permanent or session-only.
-
- A system flag is a flag name that is pre-defined in this
- specification. All system flags begin with "\". Certain system
- flags (\Deleted and \Seen) have special semantics described
- elsewhere. The currently-defined system flags are:
-
- \Seen
- Message has been read
-
- \Answered
- Message has been answered
-
- \Flagged
- Message is "flagged" for urgent/special attention
-
- \Deleted
- Message is "deleted" for removal by later EXPUNGE
-
- \Draft
- Message has not completed composition (marked as a draft).
-
- \Recent
- Message is "recently" arrived in this mailbox. This session
- is the first session to have been notified about this
- message; if the session is read-write, subsequent sessions
- will not see \Recent set for this message. This flag can not
- be altered by the client.
-
- If it is not possible to determine whether or not this
- session is the first session to be notified about a message,
- then that message SHOULD be considered recent.
-
- If multiple connections have the same mailbox selected
- simultaneously, it is undefined which of these connections
- will see newly-arrived messages with \Recent set and which
- will see it without \Recent set.
-
- A keyword is defined by the server implementation. Keywords do not
- begin with "\". Servers MAY permit the client to define new keywords
- in the mailbox (see the description of the PERMANENTFLAGS response
- code for more information).
-
-
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-
- A flag can be permanent or session-only on a per-flag basis.
- Permanent flags are those which the client can add or remove from the
- message flags permanently; that is, concurrent and subsequent
- sessions will see any change in permanent flags. Changes to session
- flags are valid only in that session.
-
- Note: The \Recent system flag is a special case of a
- session flag. \Recent can not be used as an argument in a
- STORE or APPEND command, and thus can not be changed at
- all.
-
-2.3.3. Internal Date Message Attribute
-
- The internal date and time of the message on the server. This
- is not the date and time in the [RFC-2822] header, but rather a
- date and time which reflects when the message was received. In
- the case of messages delivered via [SMTP], this SHOULD be the
- date and time of final delivery of the message as defined by
- [SMTP]. In the case of messages delivered by the IMAP4rev1 COPY
- command, this SHOULD be the internal date and time of the source
- message. In the case of messages delivered by the IMAP4rev1
- APPEND command, this SHOULD be the date and time as specified in
- the APPEND command description. All other cases are
- implementation defined.
-
-2.3.4. [RFC-2822] Size Message Attribute
-
- The number of octets in the message, as expressed in [RFC-2822]
- format.
-
-2.3.5. Envelope Structure Message Attribute
-
- A parsed representation of the [RFC-2822] header of the message.
- Note that the IMAP Envelope structure is not the same as an
- [SMTP] envelope.
-
-2.3.6. Body Structure Message Attribute
-
- A parsed representation of the [MIME-IMB] body structure
- information of the message.
-
-
-
-
-
-
-
-
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-
-2.4. Message Texts
-
- In addition to being able to fetch the full [RFC-2822] text of a
- message, IMAP4rev1 permits the fetching of portions of the full
- message text. Specifically, it is possible to fetch the
- [RFC-2822] message header, [RFC-2822] message body, a [MIME-IMB]
- body part, or a [MIME-IMB] header.
-
-3. State and Flow Diagram
-
- Once the connection between client and server is established, an
- IMAP4rev1 connection is in one of four states. The initial
- state is identified in the server greeting. Most commands are
- only valid in certain states. It is a protocol error for the
- client to attempt a command while the connection is in an
- inappropriate state, and the server will respond with a BAD or
- NO (depending upon server implementation) command completion
- result.
-
-3.1. Not Authenticated State
-
- In the not authenticated state, the client MUST supply
- authentication credentials before most commands will be
- permitted. This state is entered when a connection starts
- unless the connection has been pre-authenticated.
-
-3.2. Authenticated State
-
- In the authenticated state, the client is authenticated and MUST
- select a mailbox to access before commands that affect messages
- will be permitted. This state is entered when a
- pre-authenticated connection starts, when acceptable
- authentication credentials have been provided, after an error in
- selecting a mailbox, or after a successful CLOSE command.
-
-3.3. Selected State
-
- In a selected state, a mailbox has been selected to access.
- This state is entered when a mailbox has been successfully
- selected.
-
-
-
-
-
-
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-
-3.4. Logout State
-
- In the logout state, the connection is being terminated. This
- state can be entered as a result of a client request (via the
- LOGOUT command) or by unilateral action on the part of either
- the client or server.
-
- If the client requests the logout state, the server MUST send an
- untagged BYE response and a tagged OK response to the LOGOUT
- command before the server closes the connection; and the client
- MUST read the tagged OK response to the LOGOUT command before
- the client closes the connection.
-
- A server MUST NOT unilaterally close the connection without
- sending an untagged BYE response that contains the reason for
- having done so. A client SHOULD NOT unilaterally close the
- connection, and instead SHOULD issue a LOGOUT command. If the
- server detects that the client has unilaterally closed the
- connection, the server MAY omit the untagged BYE response and
- simply close its connection.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- +----------------------+
- |connection established|
- +----------------------+
- ||
- \/
- +--------------------------------------+
- | server greeting |
- +--------------------------------------+
- || (1) || (2) || (3)
- \/ || ||
- +-----------------+ || ||
- |Not Authenticated| || ||
- +-----------------+ || ||
- || (7) || (4) || ||
- || \/ \/ ||
- || +----------------+ ||
- || | Authenticated |<=++ ||
- || +----------------+ || ||
- || || (7) || (5) || (6) ||
- || || \/ || ||
- || || +--------+ || ||
- || || |Selected|==++ ||
- || || +--------+ ||
- || || || (7) ||
- \/ \/ \/ \/
- +--------------------------------------+
- | Logout |
- +--------------------------------------+
- ||
- \/
- +-------------------------------+
- |both sides close the connection|
- +-------------------------------+
-
- (1) connection without pre-authentication (OK greeting)
- (2) pre-authenticated connection (PREAUTH greeting)
- (3) rejected connection (BYE greeting)
- (4) successful LOGIN or AUTHENTICATE command
- (5) successful SELECT or EXAMINE command
- (6) CLOSE command, or failed SELECT or EXAMINE command
- (7) LOGOUT command, server shutdown, or connection closed
-
-
-
-
-
-
-
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-
-
-4. Data Formats
-
- IMAP4rev1 uses textual commands and responses. Data in
- IMAP4rev1 can be in one of several forms: atom, number, string,
- parenthesized list, or NIL. Note that a particular data item
- may take more than one form; for example, a data item defined as
- using "astring" syntax may be either an atom or a string.
-
-4.1. Atom
-
- An atom consists of one or more non-special characters.
-
-4.2. Number
-
- A number consists of one or more digit characters, and
- represents a numeric value.
-
-4.3. String
-
- A string is in one of two forms: either literal or quoted
- string. The literal form is the general form of string. The
- quoted string form is an alternative that avoids the overhead of
- processing a literal at the cost of limitations of characters
- which may be used.
-
- A literal is a sequence of zero or more octets (including CR and
- LF), prefix-quoted with an octet count in the form of an open
- brace ("{"), the number of octets, close brace ("}"), and CRLF.
- In the case of literals transmitted from server to client, the
- CRLF is immediately followed by the octet data. In the case of
- literals transmitted from client to server, the client MUST wait
- to receive a command continuation request (described later in
- this document) before sending the octet data (and the remainder
- of the command).
-
- A quoted string is a sequence of zero or more 7-bit characters,
- excluding CR and LF, with double quote (<">) characters at each
- end.
-
- The empty string is represented as either "" (a quoted string
- with zero characters between double quotes) or as {0} followed
- by CRLF (a literal with an octet count of 0).
-
- Note: Even if the octet count is 0, a client transmitting a
- literal MUST wait to receive a command continuation request.
-
-
-
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-
-
-4.3.1. 8-bit and Binary Strings
-
- 8-bit textual and binary mail is supported through the use of a
- [MIME-IMB] content transfer encoding. IMAP4rev1 implementations MAY
- transmit 8-bit or multi-octet characters in literals, but SHOULD do
- so only when the [CHARSET] is identified.
-
- Although a BINARY body encoding is defined, unencoded binary strings
- are not permitted. A "binary string" is any string with NUL
- characters. Implementations MUST encode binary data into a textual
- form, such as BASE64, before transmitting the data. A string with an
- excessive amount of CTL characters MAY also be considered to be
- binary.
-
-4.4. Parenthesized List
-
- Data structures are represented as a "parenthesized list"; a sequence
- of data items, delimited by space, and bounded at each end by
- parentheses. A parenthesized list can contain other parenthesized
- lists, using multiple levels of parentheses to indicate nesting.
-
- The empty list is represented as () -- a parenthesized list with no
- members.
-
-4.5. NIL
-
- The special form "NIL" represents the non-existence of a particular
- data item that is represented as a string or parenthesized list, as
- distinct from the empty string "" or the empty parenthesized list ().
-
- Note: NIL is never used for any data item which takes the
- form of an atom. For example, a mailbox name of "NIL" is a
- mailbox named NIL as opposed to a non-existent mailbox
- name. This is because mailbox uses "astring" syntax which
- is an atom or a string. Conversely, an addr-name of NIL is
- a non-existent personal name, because addr-name uses
- "nstring" syntax which is NIL or a string, but never an
- atom.
-
-
-
-
-
-
-
-
-
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-
-5. Operational Considerations
-
- The following rules are listed here to ensure that all IMAP4rev1
- implementations interoperate properly.
-
-5.1. Mailbox Naming
-
- Mailbox names are 7-bit. Client implementations MUST NOT attempt to
- create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
- names returned by LIST or LSUB as UTF-8. Server implementations
- SHOULD prohibit the creation of 8-bit mailbox names, and SHOULD NOT
- return 8-bit mailbox names in LIST or LSUB. See section 5.1.3 for
- more information on how to represent non-ASCII mailbox names.
-
- Note: 8-bit mailbox names were undefined in earlier
- versions of this protocol. Some sites used a local 8-bit
- character set to represent non-ASCII mailbox names. Such
- usage is not interoperable, and is now formally deprecated.
-
- The case-insensitive mailbox name INBOX is a special name reserved to
- mean "the primary mailbox for this user on this server". The
- interpretation of all other names is implementation-dependent.
-
- In particular, this specification takes no position on case
- sensitivity in non-INBOX mailbox names. Some server implementations
- are fully case-sensitive; others preserve case of a newly-created
- name but otherwise are case-insensitive; and yet others coerce names
- to a particular case. Client implementations MUST interact with any
- of these. If a server implementation interprets non-INBOX mailbox
- names as case-insensitive, it MUST treat names using the
- international naming convention specially as described in section
- 5.1.3.
-
- There are certain client considerations when creating a new mailbox
- name:
-
- 1) Any character which is one of the atom-specials (see the Formal
- Syntax) will require that the mailbox name be represented as a
- quoted string or literal.
-
- 2) CTL and other non-graphic characters are difficult to represent
- in a user interface and are best avoided.
-
- 3) Although the list-wildcard characters ("%" and "*") are valid
- in a mailbox name, it is difficult to use such mailbox names
- with the LIST and LSUB commands due to the conflict with
- wildcard interpretation.
-
-
-
-
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-
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-
-
- 4) Usually, a character (determined by the server implementation)
- is reserved to delimit levels of hierarchy.
-
- 5) Two characters, "#" and "&", have meanings by convention, and
- should be avoided except when used in that convention.
-
-5.1.1. Mailbox Hierarchy Naming
-
- If it is desired to export hierarchical mailbox names, mailbox names
- MUST be left-to-right hierarchical using a single character to
- separate levels of hierarchy. The same hierarchy separator character
- is used for all levels of hierarchy within a single name.
-
-5.1.2. Mailbox Namespace Naming Convention
-
- By convention, the first hierarchical element of any mailbox name
- which begins with "#" identifies the "namespace" of the remainder of
- the name. This makes it possible to disambiguate between different
- types of mailbox stores, each of which have their own namespaces.
-
- For example, implementations which offer access to USENET
- newsgroups MAY use the "#news" namespace to partition the
- USENET newsgroup namespace from that of other mailboxes.
- Thus, the comp.mail.misc newsgroup would have a mailbox
- name of "#news.comp.mail.misc", and the name
- "comp.mail.misc" can refer to a different object (e.g., a
- user's private mailbox).
-
-5.1.3. Mailbox International Naming Convention
-
- By convention, international mailbox names in IMAP4rev1 are specified
- using a modified version of the UTF-7 encoding described in [UTF-7].
- Modified UTF-7 may also be usable in servers that implement an
- earlier version of this protocol.
-
- In modified UTF-7, printable US-ASCII characters, except for "&",
- represent themselves; that is, characters with octet values 0x20-0x25
- and 0x27-0x7e. The character "&" (0x26) is represented by the
- two-octet sequence "&-".
-
- All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
- represented in modified BASE64, with a further modification from
- [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be
- used to represent any printing US-ASCII character which can represent
- itself.
-
-
-
-
-
-
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-
-
- "&" is used to shift to modified BASE64 and "-" to shift back to
- US-ASCII. There is no implicit shift from BASE64 to US-ASCII, and
- null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
- means "&") are not permitted. However, all names start in US-ASCII,
- and MUST end in US-ASCII; that is, a name that ends with a non-ASCII
- ISO-10646 character MUST end with a "-").
-
- The purpose of these modifications is to correct the following
- problems with UTF-7:
-
- 1) UTF-7 uses the "+" character for shifting; this conflicts with
- the common use of "+" in mailbox names, in particular USENET
- newsgroup names.
-
- 2) UTF-7's encoding is BASE64 which uses the "/" character; this
- conflicts with the use of "/" as a popular hierarchy delimiter.
-
- 3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
- the use of "\" as a popular hierarchy delimiter.
-
- 4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
- the use of "~" in some servers as a home directory indicator.
-
- 5) UTF-7 permits multiple alternate forms to represent the same
- string; in particular, printable US-ASCII characters can be
- represented in encoded form.
-
- Although modified UTF-7 is a convention, it establishes certain
- requirements on server handling of any mailbox name with an
- embedded "&" character. In particular, server implementations
- MUST preserve the exact form of the modified BASE64 portion of a
- modified UTF-7 name and treat that text as case-sensitive, even if
- names are otherwise case-insensitive or case-folded.
-
- Server implementations SHOULD verify that any mailbox name with an
- embedded "&" character, used as an argument to CREATE, is: in the
- correctly modified UTF-7 syntax, has no superfluous shifts, and
- has no encoding in modified BASE64 of any printing US-ASCII
- character which can represent itself. However, client
- implementations MUST NOT depend upon the server doing this, and
- SHOULD NOT attempt to create a mailbox name with an embedded "&"
- character unless it complies with the modified UTF-7 syntax.
-
- Server implementations which export a mail store that does not
- follow the modified UTF-7 convention MUST convert to modified
- UTF-7 any mailbox name that contains either non-ASCII characters
- or the "&" character.
-
-
-
-
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-
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-
-
- For example, here is a mailbox name which mixes English,
- Chinese, and Japanese text:
- ~peter/mail/&U,BTFw-/&ZeVnLIqe-
-
- For example, the string "&Jjo!" is not a valid mailbox
- name because it does not contain a shift to US-ASCII
- before the "!". The correct form is "&Jjo-!". The
- string "&U,BTFw-&ZeVnLIqe-" is not permitted because it
- contains a superfluous shift. The correct form is
- "&U,BTF2XlZyyKng-".
-
-5.2. Mailbox Size and Message Status Updates
-
- At any time, a server can send data that the client did not request.
- Sometimes, such behavior is REQUIRED. For example, agents other than
- the server MAY add messages to the mailbox (e.g., new message
- delivery), change the flags of the messages in the mailbox (e.g.,
- simultaneous access to the same mailbox by multiple agents), or even
- remove messages from the mailbox. A server MUST send mailbox size
- updates automatically if a mailbox size change is observed during the
- processing of a command. A server SHOULD send message flag updates
- automatically, without requiring the client to request such updates
- explicitly.
-
- Special rules exist for server notification of a client about the
- removal of messages to prevent synchronization errors; see the
- description of the EXPUNGE response for more detail. In particular,
- it is NOT permitted to send an EXISTS response that would reduce the
- number of messages in the mailbox; only the EXPUNGE response can do
- this.
-
- Regardless of what implementation decisions a client makes on
- remembering data from the server, a client implementation MUST record
- mailbox size updates. It MUST NOT assume that any command after the
- initial mailbox selection will return the size of the mailbox.
-
-5.3. Response when no Command in Progress
-
- Server implementations are permitted to send an untagged response
- (except for EXPUNGE) while there is no command in progress. Server
- implementations that send such responses MUST deal with flow control
- considerations. Specifically, they MUST either (1) verify that the
- size of the data does not exceed the underlying transport's available
- window size, or (2) use non-blocking writes.
-
-
-
-
-
-
-
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-
-
-5.4. Autologout Timer
-
- If a server has an inactivity autologout timer, the duration of that
- timer MUST be at least 30 minutes. The receipt of ANY command from
- the client during that interval SHOULD suffice to reset the
- autologout timer.
-
-5.5. Multiple Commands in Progress
-
- The client MAY send another command without waiting for the
- completion result response of a command, subject to ambiguity rules
- (see below) and flow control constraints on the underlying data
- stream. Similarly, a server MAY begin processing another command
- before processing the current command to completion, subject to
- ambiguity rules. However, any command continuation request responses
- and command continuations MUST be negotiated before any subsequent
- command is initiated.
-
- The exception is if an ambiguity would result because of a command
- that would affect the results of other commands. Clients MUST NOT
- send multiple commands without waiting if an ambiguity would result.
- If the server detects a possible ambiguity, it MUST execute commands
- to completion in the order given by the client.
-
- The most obvious example of ambiguity is when a command would affect
- the results of another command, e.g., a FETCH of a message's flags
- and a STORE of that same message's flags.
-
- A non-obvious ambiguity occurs with commands that permit an untagged
- EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
- since an untagged EXPUNGE response can invalidate sequence numbers in
- a subsequent command. This is not a problem for FETCH, STORE, or
- SEARCH commands because servers are prohibited from sending EXPUNGE
- responses while any of those commands are in progress. Therefore, if
- the client sends any command other than FETCH, STORE, or SEARCH, it
- MUST wait for the completion result response before sending a command
- with message sequence numbers.
-
- Note: UID FETCH, UID STORE, and UID SEARCH are different
- commands from FETCH, STORE, and SEARCH. If the client
- sends a UID command, it must wait for a completion result
- response before sending a command with message sequence
- numbers.
-
-
-
-
-
-
-
-
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-
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-
-
- For example, the following non-waiting command sequences are invalid:
-
- FETCH + NOOP + STORE
- STORE + COPY + FETCH
- COPY + COPY
- CHECK + FETCH
-
- The following are examples of valid non-waiting command sequences:
-
- FETCH + STORE + SEARCH + CHECK
- STORE + COPY + EXPUNGE
-
- UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting
- command sequence, depending upon whether or not the second UID
- SEARCH contains message sequence numbers.
-
-6. Client Commands
-
- IMAP4rev1 commands are described in this section. Commands are
- organized by the state in which the command is permitted. Commands
- which are permitted in multiple states are listed in the minimum
- permitted state (for example, commands valid in authenticated and
- selected state are listed in the authenticated state commands).
-
- Command arguments, identified by "Arguments:" in the command
- descriptions below, are described by function, not by syntax. The
- precise syntax of command arguments is described in the Formal Syntax
- section.
-
- Some commands cause specific server responses to be returned; these
- are identified by "Responses:" in the command descriptions below.
- See the response descriptions in the Responses section for
- information on these responses, and the Formal Syntax section for the
- precise syntax of these responses. It is possible for server data to
- be transmitted as a result of any command. Thus, commands that do
- not specifically require server data specify "no specific responses
- for this command" instead of "none".
-
- The "Result:" in the command description refers to the possible
- tagged status responses to a command, and any special interpretation
- of these status responses.
-
- The state of a connection is only changed by successful commands
- which are documented as changing state. A rejected command (BAD
- response) never changes the state of the connection or of the
- selected mailbox. A failed command (NO response) generally does not
- change the state of the connection or of the selected mailbox; the
- exception being the SELECT and EXAMINE commands.
-
-
-
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-
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-
-
-6.1. Client Commands - Any State
-
- The following commands are valid in any state: CAPABILITY, NOOP, and
- LOGOUT.
-
-6.1.1. CAPABILITY Command
-
- Arguments: none
-
- Responses: REQUIRED untagged response: CAPABILITY
-
- Result: OK - capability completed
- BAD - command unknown or arguments invalid
-
- The CAPABILITY command requests a listing of capabilities that the
- server supports. The server MUST send a single untagged
- CAPABILITY response with "IMAP4rev1" as one of the listed
- capabilities before the (tagged) OK response.
-
- A capability name which begins with "AUTH=" indicates that the
- server supports that particular authentication mechanism. All
- such names are, by definition, part of this specification. For
- example, the authorization capability for an experimental
- "blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
- "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
-
- Other capability names refer to extensions, revisions, or
- amendments to this specification. See the documentation of the
- CAPABILITY response for additional information. No capabilities,
- beyond the base IMAP4rev1 set defined in this specification, are
- enabled without explicit client action to invoke the capability.
-
- Client and server implementations MUST implement the STARTTLS,
- LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
- capabilities. See the Security Considerations section for
- important information.
-
- See the section entitled "Client Commands -
- Experimental/Expansion" for information about the form of site or
- implementation-specific capabilities.
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
- Example: C: abcd CAPABILITY
- S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
- LOGINDISABLED
- S: abcd OK CAPABILITY completed
- C: efgh STARTTLS
- S: efgh OK STARTLS completed
- <TLS negotiation, further commands are under [TLS] layer>
- C: ijkl CAPABILITY
- S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
- S: ijkl OK CAPABILITY completed
-
-
-6.1.2. NOOP Command
-
- Arguments: none
-
- Responses: no specific responses for this command (but see below)
-
- Result: OK - noop completed
- BAD - command unknown or arguments invalid
-
- The NOOP command always succeeds. It does nothing.
-
- Since any command can return a status update as untagged data, the
- NOOP command can be used as a periodic poll for new messages or
- message status updates during a period of inactivity (this is the
- preferred method to do this). The NOOP command can also be used
- to reset any inactivity autologout timer on the server.
-
- Example: C: a002 NOOP
- S: a002 OK NOOP completed
- . . .
- C: a047 NOOP
- S: * 22 EXPUNGE
- S: * 23 EXISTS
- S: * 3 RECENT
- S: * 14 FETCH (FLAGS (\Seen \Deleted))
- S: a047 OK NOOP completed
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-6.1.3. LOGOUT Command
-
- Arguments: none
-
- Responses: REQUIRED untagged response: BYE
-
- Result: OK - logout completed
- BAD - command unknown or arguments invalid
-
- The LOGOUT command informs the server that the client is done with
- the connection. The server MUST send a BYE untagged response
- before the (tagged) OK response, and then close the network
- connection.
-
- Example: C: A023 LOGOUT
- S: * BYE IMAP4rev1 Server logging out
- S: A023 OK LOGOUT completed
- (Server and client then close the connection)
-
-6.2. Client Commands - Not Authenticated State
-
- In the not authenticated state, the AUTHENTICATE or LOGIN command
- establishes authentication and enters the authenticated state. The
- AUTHENTICATE command provides a general mechanism for a variety of
- authentication techniques, privacy protection, and integrity
- checking; whereas the LOGIN command uses a traditional user name and
- plaintext password pair and has no means of establishing privacy
- protection or integrity checking.
-
- The STARTTLS command is an alternate form of establishing session
- privacy protection and integrity checking, but does not establish
- authentication or enter the authenticated state.
-
- Server implementations MAY allow access to certain mailboxes without
- establishing authentication. This can be done by means of the
- ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older
- convention is a LOGIN command using the userid "anonymous"; in this
- case, a password is required although the server may choose to accept
- any password. The restrictions placed on anonymous users are
- implementation-dependent.
-
- Once authenticated (including as anonymous), it is not possible to
- re-enter not authenticated state.
-
-
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
- the following commands are valid in the not authenticated state:
- STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations
- section for important information about these commands.
-
-6.2.1. STARTTLS Command
-
- Arguments: none
-
- Responses: no specific response for this command
-
- Result: OK - starttls completed, begin TLS negotiation
- BAD - command unknown or arguments invalid
-
- A [TLS] negotiation begins immediately after the CRLF at the end
- of the tagged OK response from the server. Once a client issues a
- STARTTLS command, it MUST NOT issue further commands until a
- server response is seen and the [TLS] negotiation is complete.
-
- The server remains in the non-authenticated state, even if client
- credentials are supplied during the [TLS] negotiation. This does
- not preclude an authentication mechanism such as EXTERNAL (defined
- in [SASL]) from using client identity determined by the [TLS]
- negotiation.
-
- Once [TLS] has been started, the client MUST discard cached
- information about server capabilities and SHOULD re-issue the
- CAPABILITY command. This is necessary to protect against man-in-
- the-middle attacks which alter the capabilities list prior to
- STARTTLS. The server MAY advertise different capabilities after
- STARTTLS.
-
- Example: C: a001 CAPABILITY
- S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
- S: a001 OK CAPABILITY completed
- C: a002 STARTTLS
- S: a002 OK Begin TLS negotiation now
- <TLS negotiation, further commands are under [TLS] layer>
- C: a003 CAPABILITY
- S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
- S: a003 OK CAPABILITY completed
- C: a004 LOGIN joe password
- S: a004 OK LOGIN completed
-
-
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
-6.2.2. AUTHENTICATE Command
-
- Arguments: authentication mechanism name
-
- Responses: continuation data can be requested
-
- Result: OK - authenticate completed, now in authenticated state
- NO - authenticate failure: unsupported authentication
- mechanism, credentials rejected
- BAD - command unknown or arguments invalid,
- authentication exchange cancelled
-
- The AUTHENTICATE command indicates a [SASL] authentication
- mechanism to the server. If the server supports the requested
- authentication mechanism, it performs an authentication protocol
- exchange to authenticate and identify the client. It MAY also
- negotiate an OPTIONAL security layer for subsequent protocol
- interactions. If the requested authentication mechanism is not
- supported, the server SHOULD reject the AUTHENTICATE command by
- sending a tagged NO response.
-
- The AUTHENTICATE command does not support the optional "initial
- response" feature of [SASL]. Section 5.1 of [SASL] specifies how
- to handle an authentication mechanism which uses an initial
- response.
-
- The service name specified by this protocol's profile of [SASL] is
- "imap".
-
- The authentication protocol exchange consists of a series of
- server challenges and client responses that are specific to the
- authentication mechanism. A server challenge consists of a
- command continuation request response with the "+" token followed
- by a BASE64 encoded string. The client response consists of a
- single line consisting of a BASE64 encoded string. If the client
- wishes to cancel an authentication exchange, it issues a line
- consisting of a single "*". If the server receives such a
- response, it MUST reject the AUTHENTICATE command by sending a
- tagged BAD response.
-
- If a security layer is negotiated through the [SASL]
- authentication exchange, it takes effect immediately following the
- CRLF that concludes the authentication exchange for the client,
- and the CRLF of the tagged OK response for the server.
-
- While client and server implementations MUST implement the
- AUTHENTICATE command itself, it is not required to implement any
- authentication mechanisms other than the PLAIN mechanism described
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- in [IMAP-TLS]. Also, an authentication mechanism is not required
- to support any security layers.
-
- Note: a server implementation MUST implement a
- configuration in which it does NOT permit any plaintext
- password mechanisms, unless either the STARTTLS command
- has been negotiated or some other mechanism that
- protects the session from password snooping has been
- provided. Server sites SHOULD NOT use any configuration
- which permits a plaintext password mechanism without
- such a protection mechanism against password snooping.
- Client and server implementations SHOULD implement
- additional [SASL] mechanisms that do not use plaintext
- passwords, such the GSSAPI mechanism described in [SASL]
- and/or the [DIGEST-MD5] mechanism.
-
- Servers and clients can support multiple authentication
- mechanisms. The server SHOULD list its supported authentication
- mechanisms in the response to the CAPABILITY command so that the
- client knows which authentication mechanisms to use.
-
- A server MAY include a CAPABILITY response code in the tagged OK
- response of a successful AUTHENTICATE command in order to send
- capabilities automatically. It is unnecessary for a client to
- send a separate CAPABILITY command if it recognizes these
- automatic capabilities. This should only be done if a security
- layer was not negotiated by the AUTHENTICATE command, because the
- tagged OK response as part of an AUTHENTICATE command is not
- protected by encryption/integrity checking. [SASL] requires the
- client to re-issue a CAPABILITY command in this case.
-
- If an AUTHENTICATE command fails with a NO response, the client
- MAY try another authentication mechanism by issuing another
- AUTHENTICATE command. It MAY also attempt to authenticate by
- using the LOGIN command (see section 6.2.3 for more detail). In
- other words, the client MAY request authentication types in
- decreasing order of preference, with the LOGIN command as a last
- resort.
-
- The authorization identity passed from the client to the server
- during the authentication exchange is interpreted by the server as
- the user name whose privileges the client is requesting.
-
-
-
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- Example: S: * OK IMAP4rev1 Server
- C: A001 AUTHENTICATE GSSAPI
- S: +
- C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
- MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
- b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
- Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
- cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
- AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
- C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
- I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
- vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
- pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
- FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
- NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
- O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
- vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
- S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
- AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
- uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
- C:
- S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
- ceP2CWY0SR0fAQAgAAQEBAQ=
- C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
- wkhbfa2QteAQAgAG1yYwE=
- S: A001 OK GSSAPI authentication successful
-
- Note: The line breaks within server challenges and client
- responses are for editorial clarity and are not in real
- authenticators.
-
-
-6.2.3. LOGIN Command
-
- Arguments: user name
- password
-
- Responses: no specific responses for this command
-
- Result: OK - login completed, now in authenticated state
- NO - login failure: user name or password rejected
- BAD - command unknown or arguments invalid
-
- The LOGIN command identifies the client to the server and carries
- the plaintext password authenticating this user.
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- A server MAY include a CAPABILITY response code in the tagged OK
- response to a successful LOGIN command in order to send
- capabilities automatically. It is unnecessary for a client to
- send a separate CAPABILITY command if it recognizes these
- automatic capabilities.
-
- Example: C: a001 LOGIN SMITH SESAME
- S: a001 OK LOGIN completed
-
- Note: Use of the LOGIN command over an insecure network
- (such as the Internet) is a security risk, because anyone
- monitoring network traffic can obtain plaintext passwords.
- The LOGIN command SHOULD NOT be used except as a last
- resort, and it is recommended that client implementations
- have a means to disable any automatic use of the LOGIN
- command.
-
- Unless either the STARTTLS command has been negotiated or
- some other mechanism that protects the session from
- password snooping has been provided, a server
- implementation MUST implement a configuration in which it
- advertises the LOGINDISABLED capability and does NOT permit
- the LOGIN command. Server sites SHOULD NOT use any
- configuration which permits the LOGIN command without such
- a protection mechanism against password snooping. A client
- implementation MUST NOT send a LOGIN command if the
- LOGINDISABLED capability is advertised.
-
-6.3. Client Commands - Authenticated State
-
- In the authenticated state, commands that manipulate mailboxes as
- atomic entities are permitted. Of these commands, the SELECT and
- EXAMINE commands will select a mailbox for access and enter the
- selected state.
-
- In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
- the following commands are valid in the authenticated state: SELECT,
- EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
- STATUS, and APPEND.
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-6.3.1. SELECT Command
-
- Arguments: mailbox name
-
- Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
- REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
- UIDNEXT, UIDVALIDITY
-
- Result: OK - select completed, now in selected state
- NO - select failure, now in authenticated state: no
- such mailbox, can't access mailbox
- BAD - command unknown or arguments invalid
-
- The SELECT command selects a mailbox so that messages in the
- mailbox can be accessed. Before returning an OK to the client,
- the server MUST send the following untagged data to the client.
- Note that earlier versions of this protocol only required the
- FLAGS, EXISTS, and RECENT untagged data; consequently, client
- implementations SHOULD implement default behavior for missing data
- as discussed with the individual item.
-
- FLAGS Defined flags in the mailbox. See the description
- of the FLAGS response for more detail.
-
- <n> EXISTS The number of messages in the mailbox. See the
- description of the EXISTS response for more detail.
-
- <n> RECENT The number of messages with the \Recent flag set.
- See the description of the RECENT response for more
- detail.
-
- OK [UNSEEN <n>]
- The message sequence number of the first unseen
- message in the mailbox. If this is missing, the
- client can not make any assumptions about the first
- unseen message in the mailbox, and needs to issue a
- SEARCH command if it wants to find it.
-
- OK [PERMANENTFLAGS (<list of flags>)]
- A list of message flags that the client can change
- permanently. If this is missing, the client should
- assume that all flags can be changed permanently.
-
- OK [UIDNEXT <n>]
- The next unique identifier value. Refer to section
- 2.3.1.1 for more information. If this is missing,
- the client can not make any assumptions about the
- next unique identifier value.
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- OK [UIDVALIDITY <n>]
- The unique identifier validity value. Refer to
- section 2.3.1.1 for more information. If this is
- missing, the server does not support unique
- identifiers.
-
- Only one mailbox can be selected at a time in a connection;
- simultaneous access to multiple mailboxes requires multiple
- connections. The SELECT command automatically deselects any
- currently selected mailbox before attempting the new selection.
- Consequently, if a mailbox is selected and a SELECT command that
- fails is attempted, no mailbox is selected.
-
- If the client is permitted to modify the mailbox, the server
- SHOULD prefix the text of the tagged OK response with the
- "[READ-WRITE]" response code.
-
- If the client is not permitted to modify the mailbox but is
- permitted read access, the mailbox is selected as read-only, and
- the server MUST prefix the text of the tagged OK response to
- SELECT with the "[READ-ONLY]" response code. Read-only access
- through SELECT differs from the EXAMINE command in that certain
- read-only mailboxes MAY permit the change of permanent state on a
- per-user (as opposed to global) basis. Netnews messages marked in
- a server-based .newsrc file are an example of such per-user
- permanent state that can be modified with read-only mailboxes.
-
- Example: C: A142 SELECT INBOX
- S: * 172 EXISTS
- S: * 1 RECENT
- S: * OK [UNSEEN 12] Message 12 is first unseen
- S: * OK [UIDVALIDITY 3857529045] UIDs valid
- S: * OK [UIDNEXT 4392] Predicted next UID
- S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
- S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
- S: A142 OK [READ-WRITE] SELECT completed
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-6.3.2. EXAMINE Command
-
- Arguments: mailbox name
-
- Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
- REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
- UIDNEXT, UIDVALIDITY
-
- Result: OK - examine completed, now in selected state
- NO - examine failure, now in authenticated state: no
- such mailbox, can't access mailbox
- BAD - command unknown or arguments invalid
-
- The EXAMINE command is identical to SELECT and returns the same
- output; however, the selected mailbox is identified as read-only.
- No changes to the permanent state of the mailbox, including
- per-user state, are permitted; in particular, EXAMINE MUST NOT
- cause messages to lose the \Recent flag.
-
- The text of the tagged OK response to the EXAMINE command MUST
- begin with the "[READ-ONLY]" response code.
-
- Example: C: A932 EXAMINE blurdybloop
- S: * 17 EXISTS
- S: * 2 RECENT
- S: * OK [UNSEEN 8] Message 8 is first unseen
- S: * OK [UIDVALIDITY 3857529045] UIDs valid
- S: * OK [UIDNEXT 4392] Predicted next UID
- S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
- S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
- S: A932 OK [READ-ONLY] EXAMINE completed
-
-
-6.3.3. CREATE Command
-
- Arguments: mailbox name
-
- Responses: no specific responses for this command
-
- Result: OK - create completed
- NO - create failure: can't create mailbox with that name
- BAD - command unknown or arguments invalid
-
- The CREATE command creates a mailbox with the given name. An OK
- response is returned only if a new mailbox with that name has been
- created. It is an error to attempt to create INBOX or a mailbox
- with a name that refers to an extant mailbox. Any error in
- creation will return a tagged NO response.
-
-
-
-Crispin Standards Track [Page 34]
-
-RFC 3501 IMAPv4 March 2003
-
-
- If the mailbox name is suffixed with the server's hierarchy
- separator character (as returned from the server by a LIST
- command), this is a declaration that the client intends to create
- mailbox names under this name in the hierarchy. Server
- implementations that do not require this declaration MUST ignore
- the declaration. In any case, the name created is without the
- trailing hierarchy delimiter.
-
- If the server's hierarchy separator character appears elsewhere in
- the name, the server SHOULD create any superior hierarchical names
- that are needed for the CREATE command to be successfully
- completed. In other words, an attempt to create "foo/bar/zap" on
- a server in which "/" is the hierarchy separator character SHOULD
- create foo/ and foo/bar/ if they do not already exist.
-
- If a new mailbox is created with the same name as a mailbox which
- was deleted, its unique identifiers MUST be greater than any
- unique identifiers used in the previous incarnation of the mailbox
- UNLESS the new incarnation has a different unique identifier
- validity value. See the description of the UID command for more
- detail.
-
- Example: C: A003 CREATE owatagusiam/
- S: A003 OK CREATE completed
- C: A004 CREATE owatagusiam/blurdybloop
- S: A004 OK CREATE completed
-
- Note: The interpretation of this example depends on whether
- "/" was returned as the hierarchy separator from LIST. If
- "/" is the hierarchy separator, a new level of hierarchy
- named "owatagusiam" with a member called "blurdybloop" is
- created. Otherwise, two mailboxes at the same hierarchy
- level are created.
-
-
-6.3.4. DELETE Command
-
- Arguments: mailbox name
-
- Responses: no specific responses for this command
-
- Result: OK - delete completed
- NO - delete failure: can't delete mailbox with that name
- BAD - command unknown or arguments invalid
-
-
-
-
-
-
-
-Crispin Standards Track [Page 35]
-
-RFC 3501 IMAPv4 March 2003
-
-
- The DELETE command permanently removes the mailbox with the given
- name. A tagged OK response is returned only if the mailbox has
- been deleted. It is an error to attempt to delete INBOX or a
- mailbox name that does not exist.
-
- The DELETE command MUST NOT remove inferior hierarchical names.
- For example, if a mailbox "foo" has an inferior "foo.bar"
- (assuming "." is the hierarchy delimiter character), removing
- "foo" MUST NOT remove "foo.bar". It is an error to attempt to
- delete a name that has inferior hierarchical names and also has
- the \Noselect mailbox name attribute (see the description of the
- LIST response for more details).
-
- It is permitted to delete a name that has inferior hierarchical
- names and does not have the \Noselect mailbox name attribute. In
- this case, all messages in that mailbox are removed, and the name
- will acquire the \Noselect mailbox name attribute.
-
- The value of the highest-used unique identifier of the deleted
- mailbox MUST be preserved so that a new mailbox created with the
- same name will not reuse the identifiers of the former
- incarnation, UNLESS the new incarnation has a different unique
- identifier validity value. See the description of the UID command
- for more detail.
-
- Examples: C: A682 LIST "" *
- S: * LIST () "/" blurdybloop
- S: * LIST (\Noselect) "/" foo
- S: * LIST () "/" foo/bar
- S: A682 OK LIST completed
- C: A683 DELETE blurdybloop
- S: A683 OK DELETE completed
- C: A684 DELETE foo
- S: A684 NO Name "foo" has inferior hierarchical names
- C: A685 DELETE foo/bar
- S: A685 OK DELETE Completed
- C: A686 LIST "" *
- S: * LIST (\Noselect) "/" foo
- S: A686 OK LIST completed
- C: A687 DELETE foo
- S: A687 OK DELETE Completed
-
-
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 36]
-
-RFC 3501 IMAPv4 March 2003
-
-
- C: A82 LIST "" *
- S: * LIST () "." blurdybloop
- S: * LIST () "." foo
- S: * LIST () "." foo.bar
- S: A82 OK LIST completed
- C: A83 DELETE blurdybloop
- S: A83 OK DELETE completed
- C: A84 DELETE foo
- S: A84 OK DELETE Completed
- C: A85 LIST "" *
- S: * LIST () "." foo.bar
- S: A85 OK LIST completed
- C: A86 LIST "" %
- S: * LIST (\Noselect) "." foo
- S: A86 OK LIST completed
-
-
-6.3.5. RENAME Command
-
- Arguments: existing mailbox name
- new mailbox name
-
- Responses: no specific responses for this command
-
- Result: OK - rename completed
- NO - rename failure: can't rename mailbox with that name,
- can't rename to mailbox with that name
- BAD - command unknown or arguments invalid
-
- The RENAME command changes the name of a mailbox. A tagged OK
- response is returned only if the mailbox has been renamed. It is
- an error to attempt to rename from a mailbox name that does not
- exist or to a mailbox name that already exists. Any error in
- renaming will return a tagged NO response.
-
- If the name has inferior hierarchical names, then the inferior
- hierarchical names MUST also be renamed. For example, a rename of
- "foo" to "zap" will rename "foo/bar" (assuming "/" is the
- hierarchy delimiter character) to "zap/bar".
-
- If the server's hierarchy separator character appears in the name,
- the server SHOULD create any superior hierarchical names that are
- needed for the RENAME command to complete successfully. In other
- words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
- server in which "/" is the hierarchy separator character SHOULD
- create baz/ and baz/rag/ if they do not already exist.
-
-
-
-
-
-Crispin Standards Track [Page 37]
-
-RFC 3501 IMAPv4 March 2003
-
-
- The value of the highest-used unique identifier of the old mailbox
- name MUST be preserved so that a new mailbox created with the same
- name will not reuse the identifiers of the former incarnation,
- UNLESS the new incarnation has a different unique identifier
- validity value. See the description of the UID command for more
- detail.
-
- Renaming INBOX is permitted, and has special behavior. It moves
- all messages in INBOX to a new mailbox with the given name,
- leaving INBOX empty. If the server implementation supports
- inferior hierarchical names of INBOX, these are unaffected by a
- rename of INBOX.
-
- Examples: C: A682 LIST "" *
- S: * LIST () "/" blurdybloop
- S: * LIST (\Noselect) "/" foo
- S: * LIST () "/" foo/bar
- S: A682 OK LIST completed
- C: A683 RENAME blurdybloop sarasoop
- S: A683 OK RENAME completed
- C: A684 RENAME foo zowie
- S: A684 OK RENAME Completed
- C: A685 LIST "" *
- S: * LIST () "/" sarasoop
- S: * LIST (\Noselect) "/" zowie
- S: * LIST () "/" zowie/bar
- S: A685 OK LIST completed
-
- C: Z432 LIST "" *
- S: * LIST () "." INBOX
- S: * LIST () "." INBOX.bar
- S: Z432 OK LIST completed
- C: Z433 RENAME INBOX old-mail
- S: Z433 OK RENAME completed
- C: Z434 LIST "" *
- S: * LIST () "." INBOX
- S: * LIST () "." INBOX.bar
- S: * LIST () "." old-mail
- S: Z434 OK LIST completed
-
-
-
-
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 38]
-
-RFC 3501 IMAPv4 March 2003
-
-
-6.3.6. SUBSCRIBE Command
-
- Arguments: mailbox
-
- Responses: no specific responses for this command
-
- Result: OK - subscribe completed
- NO - subscribe failure: can't subscribe to that name
- BAD - command unknown or arguments invalid
-
- The SUBSCRIBE command adds the specified mailbox name to the
- server's set of "active" or "subscribed" mailboxes as returned by
- the LSUB command. This command returns a tagged OK response only
- if the subscription is successful.
-
- A server MAY validate the mailbox argument to SUBSCRIBE to verify
- that it exists. However, it MUST NOT unilaterally remove an
- existing mailbox name from the subscription list even if a mailbox
- by that name no longer exists.
-
- Note: This requirement is because a server site can
- choose to routinely remove a mailbox with a well-known
- name (e.g., "system-alerts") after its contents expire,
- with the intention of recreating it when new contents
- are appropriate.
-
-
- Example: C: A002 SUBSCRIBE #news.comp.mail.mime
- S: A002 OK SUBSCRIBE completed
-
-
-6.3.7. UNSUBSCRIBE Command
-
- Arguments: mailbox name
-
- Responses: no specific responses for this command
-
- Result: OK - unsubscribe completed
- NO - unsubscribe failure: can't unsubscribe that name
- BAD - command unknown or arguments invalid
-
- The UNSUBSCRIBE command removes the specified mailbox name from
- the server's set of "active" or "subscribed" mailboxes as returned
- by the LSUB command. This command returns a tagged OK response
- only if the unsubscription is successful.
-
- Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime
- S: A002 OK UNSUBSCRIBE completed
-
-
-
-Crispin Standards Track [Page 39]
-
-RFC 3501 IMAPv4 March 2003
-
-
-6.3.8. LIST Command
-
- Arguments: reference name
- mailbox name with possible wildcards
-
- Responses: untagged responses: LIST
-
- Result: OK - list completed
- NO - list failure: can't list that reference or name
- BAD - command unknown or arguments invalid
-
- The LIST command returns a subset of names from the complete set
- of all names available to the client. Zero or more untagged LIST
- replies are returned, containing the name attributes, hierarchy
- delimiter, and name; see the description of the LIST reply for
- more detail.
-
- The LIST command SHOULD return its data quickly, without undue
- delay. For example, it SHOULD NOT go to excess trouble to
- calculate the \Marked or \Unmarked status or perform other
- processing; if each name requires 1 second of processing, then a
- list of 1200 names would take 20 minutes!
-
- An empty ("" string) reference name argument indicates that the
- mailbox name is interpreted as by SELECT. The returned mailbox
- names MUST match the supplied mailbox name pattern. A non-empty
- reference name argument is the name of a mailbox or a level of
- mailbox hierarchy, and indicates the context in which the mailbox
- name is interpreted.
-
- An empty ("" string) mailbox name argument is a special request to
- return the hierarchy delimiter and the root name of the name given
- in the reference. The value returned as the root MAY be the empty
- string if the reference is non-rooted or is an empty string. In
- all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
- is returned. This permits a client to get the hierarchy delimiter
- (or find out that the mailbox names are flat) even when no
- mailboxes by that name currently exist.
-
- The reference and mailbox name arguments are interpreted into a
- canonical form that represents an unambiguous left-to-right
- hierarchy. The returned mailbox names will be in the interpreted
- form.
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 40]
-
-RFC 3501 IMAPv4 March 2003
-
-
- Note: The interpretation of the reference argument is
- implementation-defined. It depends upon whether the
- server implementation has a concept of the "current
- working directory" and leading "break out characters",
- which override the current working directory.
-
- For example, on a server which exports a UNIX or NT
- filesystem, the reference argument contains the current
- working directory, and the mailbox name argument would
- contain the name as interpreted in the current working
- directory.
-
- If a server implementation has no concept of break out
- characters, the canonical form is normally the reference
- name appended with the mailbox name. Note that if the
- server implements the namespace convention (section
- 5.1.2), "#" is a break out character and must be treated
- as such.
-
- If the reference argument is not a level of mailbox
- hierarchy (that is, it is a \NoInferiors name), and/or
- the reference argument does not end with the hierarchy
- delimiter, it is implementation-dependent how this is
- interpreted. For example, a reference of "foo/bar" and
- mailbox name of "rag/baz" could be interpreted as
- "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
- A client SHOULD NOT use such a reference argument except
- at the explicit request of the user. A hierarchical
- browser MUST NOT make any assumptions about server
- interpretation of the reference unless the reference is
- a level of mailbox hierarchy AND ends with the hierarchy
- delimiter.
-
- Any part of the reference argument that is included in the
- interpreted form SHOULD prefix the interpreted form. It SHOULD
- also be in the same form as the reference name argument. This
- rule permits the client to determine if the returned mailbox name
- is in the context of the reference argument, or if something about
- the mailbox argument overrode the reference argument. Without
- this rule, the client would have to have knowledge of the server's
- naming semantics including what characters are "breakouts" that
- override a naming context.
-
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 41]
-
-RFC 3501 IMAPv4 March 2003
-
-
- For example, here are some examples of how references
- and mailbox names might be interpreted on a UNIX-based
- server:
-
- Reference Mailbox Name Interpretation
- ------------ ------------ --------------
- ~smith/Mail/ foo.* ~smith/Mail/foo.*
- archive/ % archive/%
- #news. comp.mail.* #news.comp.mail.*
- ~smith/Mail/ /usr/doc/foo /usr/doc/foo
- archive/ ~fred/Mail/* ~fred/Mail/*
-
- The first three examples demonstrate interpretations in
- the context of the reference argument. Note that
- "~smith/Mail" SHOULD NOT be transformed into something
- like "/u2/users/smith/Mail", or it would be impossible
- for the client to determine that the interpretation was
- in the context of the reference.
-
- The character "*" is a wildcard, and matches zero or more
- characters at this position. The character "%" is similar to "*",
- but it does not match a hierarchy delimiter. If the "%" wildcard
- is the last character of a mailbox name argument, matching levels
- of hierarchy are also returned. If these levels of hierarchy are
- not also selectable mailboxes, they are returned with the
- \Noselect mailbox name attribute (see the description of the LIST
- response for more details).
-
- Server implementations are permitted to "hide" otherwise
- accessible mailboxes from the wildcard characters, by preventing
- certain characters or names from matching a wildcard in certain
- situations. For example, a UNIX-based server might restrict the
- interpretation of "*" so that an initial "/" character does not
- match.
-
- The special name INBOX is included in the output from LIST, if
- INBOX is supported by this server for this user and if the
- uppercase string "INBOX" matches the interpreted reference and
- mailbox name arguments with wildcards as described above. The
- criteria for omitting INBOX is whether SELECT INBOX will return
- failure; it is not relevant whether the user's real INBOX resides
- on this or some other server.
-
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 42]
-
-RFC 3501 IMAPv4 March 2003
-
-
- Example: C: A101 LIST "" ""
- S: * LIST (\Noselect) "/" ""
- S: A101 OK LIST Completed
- C: A102 LIST #news.comp.mail.misc ""
- S: * LIST (\Noselect) "." #news.
- S: A102 OK LIST Completed
- C: A103 LIST /usr/staff/jones ""
- S: * LIST (\Noselect) "/" /
- S: A103 OK LIST Completed
- C: A202 LIST ~/Mail/ %
- S: * LIST (\Noselect) "/" ~/Mail/foo
- S: * LIST () "/" ~/Mail/meetings
- S: A202 OK LIST completed
-
-
-6.3.9. LSUB Command
-
- Arguments: reference name
- mailbox name with possible wildcards
-
- Responses: untagged responses: LSUB
-
- Result: OK - lsub completed
- NO - lsub failure: can't list that reference or name
- BAD - command unknown or arguments invalid
-
- The LSUB command returns a subset of names from the set of names
- that the user has declared as being "active" or "subscribed".
- Zero or more untagged LSUB replies are returned. The arguments to
- LSUB are in the same form as those for LIST.
-
- The returned untagged LSUB response MAY contain different mailbox
- flags from a LIST untagged response. If this should happen, the
- flags in the untagged LIST are considered more authoritative.
-
- A special situation occurs when using LSUB with the % wildcard.
- Consider what happens if "foo/bar" (with a hierarchy delimiter of
- "/") is subscribed but "foo" is not. A "%" wildcard to LSUB must
- return foo, not foo/bar, in the LSUB response, and it MUST be
- flagged with the \Noselect attribute.
-
- The server MUST NOT unilaterally remove an existing mailbox name
- from the subscription list even if a mailbox by that name no
- longer exists.
-
-
-
-
-
-
-
-Crispin Standards Track [Page 43]
-
-RFC 3501 IMAPv4 March 2003
-
-
- Example: C: A002 LSUB "#news." "comp.mail.*"
- S: * LSUB () "." #news.comp.mail.mime
- S: * LSUB () "." #news.comp.mail.misc
- S: A002 OK LSUB completed
- C: A003 LSUB "#news." "comp.%"
- S: * LSUB (\NoSelect) "." #news.comp.mail
- S: A003 OK LSUB completed
-
-
-6.3.10. STATUS Command
-
- Arguments: mailbox name
- status data item names
-
- Responses: untagged responses: STATUS
-
- Result: OK - status completed
- NO - status failure: no status for that name
- BAD - command unknown or arguments invalid
-
- The STATUS command requests the status of the indicated mailbox.
- It does not change the currently selected mailbox, nor does it
- affect the state of any messages in the queried mailbox (in
- particular, STATUS MUST NOT cause messages to lose the \Recent
- flag).
-
- The STATUS command provides an alternative to opening a second
- IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
- query that mailbox's status without deselecting the current
- mailbox in the first IMAP4rev1 connection.
-
- Unlike the LIST command, the STATUS command is not guaranteed to
- be fast in its response. Under certain circumstances, it can be
- quite slow. In some implementations, the server is obliged to
- open the mailbox read-only internally to obtain certain status
- information. Also unlike the LIST command, the STATUS command
- does not accept wildcards.
-
- Note: The STATUS command is intended to access the
- status of mailboxes other than the currently selected
- mailbox. Because the STATUS command can cause the
- mailbox to be opened internally, and because this
- information is available by other means on the selected
- mailbox, the STATUS command SHOULD NOT be used on the
- currently selected mailbox.
-
-
-
-
-
-
-Crispin Standards Track [Page 44]
-
-RFC 3501 IMAPv4 March 2003
-
-
- The STATUS command MUST NOT be used as a "check for new
- messages in the selected mailbox" operation (refer to
- sections 7, 7.3.1, and 7.3.2 for more information about
- the proper method for new message checking).
-
- Because the STATUS command is not guaranteed to be fast
- in its results, clients SHOULD NOT expect to be able to
- issue many consecutive STATUS commands and obtain
- reasonable performance.
-
- The currently defined status data items that can be requested are:
-
- MESSAGES
- The number of messages in the mailbox.
-
- RECENT
- The number of messages with the \Recent flag set.
-
- UIDNEXT
- The next unique identifier value of the mailbox. Refer to
- section 2.3.1.1 for more information.
-
- UIDVALIDITY
- The unique identifier validity value of the mailbox. Refer to
- section 2.3.1.1 for more information.
-
- UNSEEN
- The number of messages which do not have the \Seen flag set.
-
-
- Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
- S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
- S: A042 OK STATUS completed
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-6.3.11. APPEND Command
-
- Arguments: mailbox name
- OPTIONAL flag parenthesized list
- OPTIONAL date/time string
- message literal
-
- Responses: no specific responses for this command
-
- Result: OK - append completed
- NO - append error: can't append to that mailbox, error
- in flags or date/time or message text
- BAD - command unknown or arguments invalid
-
- The APPEND command appends the literal argument as a new message
- to the end of the specified destination mailbox. This argument
- SHOULD be in the format of an [RFC-2822] message. 8-bit
- characters are permitted in the message. A server implementation
- that is unable to preserve 8-bit data properly MUST be able to
- reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
- content transfer encoding.
-
- Note: There MAY be exceptions, e.g., draft messages, in
- which required [RFC-2822] header lines are omitted in
- the message literal argument to APPEND. The full
- implications of doing so MUST be understood and
- carefully weighed.
-
- If a flag parenthesized list is specified, the flags SHOULD be set
- in the resulting message; otherwise, the flag list of the
- resulting message is set to empty by default. In either case, the
- Recent flag is also set.
-
- If a date-time is specified, the internal date SHOULD be set in
- the resulting message; otherwise, the internal date of the
- resulting message is set to the current date and time by default.
-
- If the append is unsuccessful for any reason, the mailbox MUST be
- restored to its state before the APPEND attempt; no partial
- appending is permitted.
-
- If the destination mailbox does not exist, a server MUST return an
- error, and MUST NOT automatically create the mailbox. Unless it
- is certain that the destination mailbox can not be created, the
- server MUST send the response code "[TRYCREATE]" as the prefix of
- the text of the tagged NO response. This gives a hint to the
- client that it can attempt a CREATE command and retry the APPEND
- if the CREATE is successful.
-
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-
- If the mailbox is currently selected, the normal new message
- actions SHOULD occur. Specifically, the server SHOULD notify the
- client immediately via an untagged EXISTS response. If the server
- does not do so, the client MAY issue a NOOP command (or failing
- that, a CHECK command) after one or more APPEND commands.
-
- Example: C: A003 APPEND saved-messages (\Seen) {310}
- S: + Ready for literal data
- C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
- C: From: Fred Foobar <foobar@Blurdybloop.COM>
- C: Subject: afternoon meeting
- C: To: mooch@owatagu.siam.edu
- C: Message-Id: <B27397-0100000@Blurdybloop.COM>
- C: MIME-Version: 1.0
- C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
- C:
- C: Hello Joe, do you think we can meet at 3:30 tomorrow?
- C:
- S: A003 OK APPEND completed
-
- Note: The APPEND command is not used for message delivery,
- because it does not provide a mechanism to transfer [SMTP]
- envelope information.
-
-6.4. Client Commands - Selected State
-
- In the selected state, commands that manipulate messages in a mailbox
- are permitted.
-
- In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
- and the authenticated state commands (SELECT, EXAMINE, CREATE,
- DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
- APPEND), the following commands are valid in the selected state:
- CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
-
-6.4.1. CHECK Command
-
- Arguments: none
-
- Responses: no specific responses for this command
-
- Result: OK - check completed
- BAD - command unknown or arguments invalid
-
- The CHECK command requests a checkpoint of the currently selected
- mailbox. A checkpoint refers to any implementation-dependent
- housekeeping associated with the mailbox (e.g., resolving the
- server's in-memory state of the mailbox with the state on its
-
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- disk) that is not normally executed as part of each command. A
- checkpoint MAY take a non-instantaneous amount of real time to
- complete. If a server implementation has no such housekeeping
- considerations, CHECK is equivalent to NOOP.
-
- There is no guarantee that an EXISTS untagged response will happen
- as a result of CHECK. NOOP, not CHECK, SHOULD be used for new
- message polling.
-
- Example: C: FXXZ CHECK
- S: FXXZ OK CHECK Completed
-
-
-6.4.2. CLOSE Command
-
- Arguments: none
-
- Responses: no specific responses for this command
-
- Result: OK - close completed, now in authenticated state
- BAD - command unknown or arguments invalid
-
- The CLOSE command permanently removes all messages that have the
- \Deleted flag set from the currently selected mailbox, and returns
- to the authenticated state from the selected state. No untagged
- EXPUNGE responses are sent.
-
- No messages are removed, and no error is given, if the mailbox is
- selected by an EXAMINE command or is otherwise selected read-only.
-
- Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT
- command MAY be issued without previously issuing a CLOSE command.
- The SELECT, EXAMINE, and LOGOUT commands implicitly close the
- currently selected mailbox without doing an expunge. However,
- when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
- sequence is considerably faster than an EXPUNGE-LOGOUT or
- EXPUNGE-SELECT because no untagged EXPUNGE responses (which the
- client would probably ignore) are sent.
-
- Example: C: A341 CLOSE
- S: A341 OK CLOSE completed
-
-
-
-
-
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-
-6.4.3. EXPUNGE Command
-
- Arguments: none
-
- Responses: untagged responses: EXPUNGE
-
- Result: OK - expunge completed
- NO - expunge failure: can't expunge (e.g., permission
- denied)
- BAD - command unknown or arguments invalid
-
- The EXPUNGE command permanently removes all messages that have the
- \Deleted flag set from the currently selected mailbox. Before
- returning an OK to the client, an untagged EXPUNGE response is
- sent for each message that is removed.
-
- Example: C: A202 EXPUNGE
- S: * 3 EXPUNGE
- S: * 3 EXPUNGE
- S: * 5 EXPUNGE
- S: * 8 EXPUNGE
- S: A202 OK EXPUNGE completed
-
- Note: In this example, messages 3, 4, 7, and 11 had the
- \Deleted flag set. See the description of the EXPUNGE
- response for further explanation.
-
-
-6.4.4. SEARCH Command
-
- Arguments: OPTIONAL [CHARSET] specification
- searching criteria (one or more)
-
- Responses: REQUIRED untagged response: SEARCH
-
- Result: OK - search completed
- NO - search error: can't search that [CHARSET] or
- criteria
- BAD - command unknown or arguments invalid
-
- The SEARCH command searches the mailbox for messages that match
- the given searching criteria. Searching criteria consist of one
- or more search keys. The untagged SEARCH response from the server
- contains a listing of message sequence numbers corresponding to
- those messages that match the searching criteria.
-
-
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-
- When multiple keys are specified, the result is the intersection
- (AND function) of all the messages that match those keys. For
- example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
- to all deleted messages from Smith that were placed in the mailbox
- since February 1, 1994. A search key can also be a parenthesized
- list of one or more search keys (e.g., for use with the OR and NOT
- keys).
-
- Server implementations MAY exclude [MIME-IMB] body parts with
- terminal content media types other than TEXT and MESSAGE from
- consideration in SEARCH matching.
-
- The OPTIONAL [CHARSET] specification consists of the word
- "CHARSET" followed by a registered [CHARSET]. It indicates the
- [CHARSET] of the strings that appear in the search criteria.
- [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
- [RFC-2822]/[MIME-IMB] headers, MUST be decoded before comparing
- text in a [CHARSET] other than US-ASCII. US-ASCII MUST be
- supported; other [CHARSET]s MAY be supported.
-
- If the server does not support the specified [CHARSET], it MUST
- return a tagged NO response (not a BAD). This response SHOULD
- contain the BADCHARSET response code, which MAY list the
- [CHARSET]s supported by the server.
-
- In all search keys that use strings, a message matches the key if
- the string is a substring of the field. The matching is
- case-insensitive.
-
- The defined search keys are as follows. Refer to the Formal
- Syntax section for the precise syntactic definitions of the
- arguments.
-
- <sequence set>
- Messages with message sequence numbers corresponding to the
- specified message sequence number set.
-
- ALL
- All messages in the mailbox; the default initial key for
- ANDing.
-
- ANSWERED
- Messages with the \Answered flag set.
-
-
-
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-
- BCC <string>
- Messages that contain the specified string in the envelope
- structure's BCC field.
-
- BEFORE <date>
- Messages whose internal date (disregarding time and timezone)
- is earlier than the specified date.
-
- BODY <string>
- Messages that contain the specified string in the body of the
- message.
-
- CC <string>
- Messages that contain the specified string in the envelope
- structure's CC field.
-
- DELETED
- Messages with the \Deleted flag set.
-
- DRAFT
- Messages with the \Draft flag set.
-
- FLAGGED
- Messages with the \Flagged flag set.
-
- FROM <string>
- Messages that contain the specified string in the envelope
- structure's FROM field.
-
- HEADER <field-name> <string>
- Messages that have a header with the specified field-name (as
- defined in [RFC-2822]) and that contains the specified string
- in the text of the header (what comes after the colon). If the
- string to search is zero-length, this matches all messages that
- have a header line with the specified field-name regardless of
- the contents.
-
- KEYWORD <flag>
- Messages with the specified keyword flag set.
-
- LARGER <n>
- Messages with an [RFC-2822] size larger than the specified
- number of octets.
-
- NEW
- Messages that have the \Recent flag set but not the \Seen flag.
- This is functionally equivalent to "(RECENT UNSEEN)".
-
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-
- NOT <search-key>
- Messages that do not match the specified search key.
-
- OLD
- Messages that do not have the \Recent flag set. This is
- functionally equivalent to "NOT RECENT" (as opposed to "NOT
- NEW").
-
- ON <date>
- Messages whose internal date (disregarding time and timezone)
- is within the specified date.
-
- OR <search-key1> <search-key2>
- Messages that match either search key.
-
- RECENT
- Messages that have the \Recent flag set.
-
- SEEN
- Messages that have the \Seen flag set.
-
- SENTBEFORE <date>
- Messages whose [RFC-2822] Date: header (disregarding time and
- timezone) is earlier than the specified date.
-
- SENTON <date>
- Messages whose [RFC-2822] Date: header (disregarding time and
- timezone) is within the specified date.
-
- SENTSINCE <date>
- Messages whose [RFC-2822] Date: header (disregarding time and
- timezone) is within or later than the specified date.
-
- SINCE <date>
- Messages whose internal date (disregarding time and timezone)
- is within or later than the specified date.
-
- SMALLER <n>
- Messages with an [RFC-2822] size smaller than the specified
- number of octets.
-
-
-
-
-
-
-
-
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-
- SUBJECT <string>
- Messages that contain the specified string in the envelope
- structure's SUBJECT field.
-
- TEXT <string>
- Messages that contain the specified string in the header or
- body of the message.
-
- TO <string>
- Messages that contain the specified string in the envelope
- structure's TO field.
-
- UID <sequence set>
- Messages with unique identifiers corresponding to the specified
- unique identifier set. Sequence set ranges are permitted.
-
- UNANSWERED
- Messages that do not have the \Answered flag set.
-
- UNDELETED
- Messages that do not have the \Deleted flag set.
-
- UNDRAFT
- Messages that do not have the \Draft flag set.
-
- UNFLAGGED
- Messages that do not have the \Flagged flag set.
-
- UNKEYWORD <flag>
- Messages that do not have the specified keyword flag set.
-
- UNSEEN
- Messages that do not have the \Seen flag set.
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
- Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
- S: * SEARCH 2 84 882
- S: A282 OK SEARCH completed
- C: A283 SEARCH TEXT "string not in mailbox"
- S: * SEARCH
- S: A283 OK SEARCH completed
- C: A284 SEARCH CHARSET UTF-8 TEXT {6}
- C: XXXXXX
- S: * SEARCH 43
- S: A284 OK SEARCH completed
-
- Note: Since this document is restricted to 7-bit ASCII
- text, it is not possible to show actual UTF-8 data. The
- "XXXXXX" is a placeholder for what would be 6 octets of
- 8-bit data in an actual transaction.
-
-
-6.4.5. FETCH Command
-
- Arguments: sequence set
- message data item names or macro
-
- Responses: untagged responses: FETCH
-
- Result: OK - fetch completed
- NO - fetch error: can't fetch that data
- BAD - command unknown or arguments invalid
-
- The FETCH command retrieves data associated with a message in the
- mailbox. The data items to be fetched can be either a single atom
- or a parenthesized list.
-
- Most data items, identified in the formal syntax under the
- msg-att-static rule, are static and MUST NOT change for any
- particular message. Other data items, identified in the formal
- syntax under the msg-att-dynamic rule, MAY change, either as a
- result of a STORE command or due to external events.
-
- For example, if a client receives an ENVELOPE for a
- message when it already knows the envelope, it can
- safely ignore the newly transmitted envelope.
-
- There are three macros which specify commonly-used sets of data
- items, and can be used instead of data items. A macro must be
- used by itself, and not in conjunction with other macros or data
- items.
-
-
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-
- ALL
- Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)
-
- FAST
- Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)
-
- FULL
- Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
- BODY)
-
- The currently defined data items that can be fetched are:
-
- BODY
- Non-extensible form of BODYSTRUCTURE.
-
- BODY[<section>]<<partial>>
- The text of a particular body section. The section
- specification is a set of zero or more part specifiers
- delimited by periods. A part specifier is either a part number
- or one of the following: HEADER, HEADER.FIELDS,
- HEADER.FIELDS.NOT, MIME, and TEXT. An empty section
- specification refers to the entire message, including the
- header.
-
- Every message has at least one part number. Non-[MIME-IMB]
- messages, and non-multipart [MIME-IMB] messages with no
- encapsulated message, only have a part 1.
-
- Multipart messages are assigned consecutive part numbers, as
- they occur in the message. If a particular part is of type
- message or multipart, its parts MUST be indicated by a period
- followed by the part number within that nested multipart part.
-
- A part of type MESSAGE/RFC822 also has nested part numbers,
- referring to parts of the MESSAGE part's body.
-
- The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part
- specifiers can be the sole part specifier or can be prefixed by
- one or more numeric part specifiers, provided that the numeric
- part specifier refers to a part of type MESSAGE/RFC822. The
- MIME part specifier MUST be prefixed by one or more numeric
- part specifiers.
-
- The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
- specifiers refer to the [RFC-2822] header of the message or of
- an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
- HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
- field-name (as defined in [RFC-2822]) names, and return a
-
-
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-
- subset of the header. The subset returned by HEADER.FIELDS
- contains only those header fields with a field-name that
- matches one of the names in the list; similarly, the subset
- returned by HEADER.FIELDS.NOT contains only the header fields
- with a non-matching field-name. The field-matching is
- case-insensitive but otherwise exact. Subsetting does not
- exclude the [RFC-2822] delimiting blank line between the header
- and the body; the blank line is included in all header fetches,
- except in the case of a message which has no body and no blank
- line.
-
- The MIME part specifier refers to the [MIME-IMB] header for
- this part.
-
- The TEXT part specifier refers to the text body of the message,
- omitting the [RFC-2822] header.
-
- Here is an example of a complex message with some of its
- part specifiers:
-
- HEADER ([RFC-2822] header of the message)
- TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
- 1 TEXT/PLAIN
- 2 APPLICATION/OCTET-STREAM
- 3 MESSAGE/RFC822
- 3.HEADER ([RFC-2822] header of the message)
- 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
- 3.1 TEXT/PLAIN
- 3.2 APPLICATION/OCTET-STREAM
- 4 MULTIPART/MIXED
- 4.1 IMAGE/GIF
- 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
- 4.2 MESSAGE/RFC822
- 4.2.HEADER ([RFC-2822] header of the message)
- 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
- 4.2.1 TEXT/PLAIN
- 4.2.2 MULTIPART/ALTERNATIVE
- 4.2.2.1 TEXT/PLAIN
- 4.2.2.2 TEXT/RICHTEXT
-
-
- It is possible to fetch a substring of the designated text.
- This is done by appending an open angle bracket ("<"), the
- octet position of the first desired octet, a period, the
- maximum number of octets desired, and a close angle bracket
- (">") to the part specifier. If the starting octet is beyond
- the end of the text, an empty string is returned.
-
-
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-
- Any partial fetch that attempts to read beyond the end of the
- text is truncated as appropriate. A partial fetch that starts
- at octet 0 is returned as a partial fetch, even if this
- truncation happened.
-
- Note: This means that BODY[]<0.2048> of a 1500-octet message
- will return BODY[]<0> with a literal of size 1500, not
- BODY[].
-
- Note: A substring fetch of a HEADER.FIELDS or
- HEADER.FIELDS.NOT part specifier is calculated after
- subsetting the header.
-
- The \Seen flag is implicitly set; if this causes the flags to
- change, they SHOULD be included as part of the FETCH responses.
-
- BODY.PEEK[<section>]<<partial>>
- An alternate form of BODY[<section>] that does not implicitly
- set the \Seen flag.
-
- BODYSTRUCTURE
- The [MIME-IMB] body structure of the message. This is computed
- by the server by parsing the [MIME-IMB] header fields in the
- [RFC-2822] header and [MIME-IMB] headers.
-
- ENVELOPE
- The envelope structure of the message. This is computed by the
- server by parsing the [RFC-2822] header into the component
- parts, defaulting various fields as necessary.
-
- FLAGS
- The flags that are set for this message.
-
- INTERNALDATE
- The internal date of the message.
-
- RFC822
- Functionally equivalent to BODY[], differing in the syntax of
- the resulting untagged FETCH data (RFC822 is returned).
-
- RFC822.HEADER
- Functionally equivalent to BODY.PEEK[HEADER], differing in the
- syntax of the resulting untagged FETCH data (RFC822.HEADER is
- returned).
-
- RFC822.SIZE
- The [RFC-2822] size of the message.
-
-
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-
- RFC822.TEXT
- Functionally equivalent to BODY[TEXT], differing in the syntax
- of the resulting untagged FETCH data (RFC822.TEXT is returned).
-
- UID
- The unique identifier for the message.
-
-
- Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
- S: * 2 FETCH ....
- S: * 3 FETCH ....
- S: * 4 FETCH ....
- S: A654 OK FETCH completed
-
-
-6.4.6. STORE Command
-
- Arguments: sequence set
- message data item name
- value for message data item
-
- Responses: untagged responses: FETCH
-
- Result: OK - store completed
- NO - store error: can't store that data
- BAD - command unknown or arguments invalid
-
- The STORE command alters data associated with a message in the
- mailbox. Normally, STORE will return the updated value of the
- data with an untagged FETCH response. A suffix of ".SILENT" in
- the data item name prevents the untagged FETCH, and the server
- SHOULD assume that the client has determined the updated value
- itself or does not care about the updated value.
-
- Note: Regardless of whether or not the ".SILENT" suffix
- was used, the server SHOULD send an untagged FETCH
- response if a change to a message's flags from an
- external source is observed. The intent is that the
- status of the flags is determinate without a race
- condition.
-
-
-
-
-
-
-
-
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-
- The currently defined data items that can be stored are:
-
- FLAGS <flag list>
- Replace the flags for the message (other than \Recent) with the
- argument. The new value of the flags is returned as if a FETCH
- of those flags was done.
-
- FLAGS.SILENT <flag list>
- Equivalent to FLAGS, but without returning a new value.
-
- +FLAGS <flag list>
- Add the argument to the flags for the message. The new value
- of the flags is returned as if a FETCH of those flags was done.
-
- +FLAGS.SILENT <flag list>
- Equivalent to +FLAGS, but without returning a new value.
-
- -FLAGS <flag list>
- Remove the argument from the flags for the message. The new
- value of the flags is returned as if a FETCH of those flags was
- done.
-
- -FLAGS.SILENT <flag list>
- Equivalent to -FLAGS, but without returning a new value.
-
-
- Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
- S: * 2 FETCH (FLAGS (\Deleted \Seen))
- S: * 3 FETCH (FLAGS (\Deleted))
- S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
- S: A003 OK STORE completed
-
-
-6.4.7. COPY Command
-
- Arguments: sequence set
- mailbox name
-
- Responses: no specific responses for this command
-
- Result: OK - copy completed
- NO - copy error: can't copy those messages or to that
- name
- BAD - command unknown or arguments invalid
-
-
-
-
-
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-
- The COPY command copies the specified message(s) to the end of the
- specified destination mailbox. The flags and internal date of the
- message(s) SHOULD be preserved, and the Recent flag SHOULD be set,
- in the copy.
-
- If the destination mailbox does not exist, a server SHOULD return
- an error. It SHOULD NOT automatically create the mailbox. Unless
- it is certain that the destination mailbox can not be created, the
- server MUST send the response code "[TRYCREATE]" as the prefix of
- the text of the tagged NO response. This gives a hint to the
- client that it can attempt a CREATE command and retry the COPY if
- the CREATE is successful.
-
- If the COPY command is unsuccessful for any reason, server
- implementations MUST restore the destination mailbox to its state
- before the COPY attempt.
-
- Example: C: A003 COPY 2:4 MEETING
- S: A003 OK COPY completed
-
-
-6.4.8. UID Command
-
- Arguments: command name
- command arguments
-
- Responses: untagged responses: FETCH, SEARCH
-
- Result: OK - UID command completed
- NO - UID command error
- BAD - command unknown or arguments invalid
-
- The UID command has two forms. In the first form, it takes as its
- arguments a COPY, FETCH, or STORE command with arguments
- appropriate for the associated command. However, the numbers in
- the sequence set argument are unique identifiers instead of
- message sequence numbers. Sequence set ranges are permitted, but
- there is no guarantee that unique identifiers will be contiguous.
-
- A non-existent unique identifier is ignored without any error
- message generated. Thus, it is possible for a UID FETCH command
- to return an OK without any data or a UID COPY or UID STORE to
- return an OK without performing any operations.
-
- In the second form, the UID command takes a SEARCH command with
- SEARCH command arguments. The interpretation of the arguments is
- the same as with SEARCH; however, the numbers returned in a SEARCH
- response for a UID SEARCH command are unique identifiers instead
-
-
-
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-
-
- of message sequence numbers. For example, the command UID SEARCH
- 1:100 UID 443:557 returns the unique identifiers corresponding to
- the intersection of two sequence sets, the message sequence number
- range 1:100 and the UID range 443:557.
-
- Note: in the above example, the UID range 443:557
- appears. The same comment about a non-existent unique
- identifier being ignored without any error message also
- applies here. Hence, even if neither UID 443 or 557
- exist, this range is valid and would include an existing
- UID 495.
-
- Also note that a UID range of 559:* always includes the
- UID of the last message in the mailbox, even if 559 is
- higher than any assigned UID value. This is because the
- contents of a range are independent of the order of the
- range endpoints. Thus, any UID range with * as one of
- the endpoints indicates at least one message (the
- message with the highest numbered UID), unless the
- mailbox is empty.
-
- The number after the "*" in an untagged FETCH response is always a
- message sequence number, not a unique identifier, even for a UID
- command response. However, server implementations MUST implicitly
- include the UID message data item as part of any FETCH response
- caused by a UID command, regardless of whether a UID was specified
- as a message data item to the FETCH.
-
-
- Note: The rule about including the UID message data item as part
- of a FETCH response primarily applies to the UID FETCH and UID
- STORE commands, including a UID FETCH command that does not
- include UID as a message data item. Although it is unlikely that
- the other UID commands will cause an untagged FETCH, this rule
- applies to these commands as well.
-
- Example: C: A999 UID FETCH 4827313:4828442 FLAGS
- S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
- S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
- S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
- S: A999 OK UID FETCH completed
-
-
-
-
-
-
-
-
-
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-
-
-6.5. Client Commands - Experimental/Expansion
-
-
-6.5.1. X<atom> Command
-
- Arguments: implementation defined
-
- Responses: implementation defined
-
- Result: OK - command completed
- NO - failure
- BAD - command unknown or arguments invalid
-
- Any command prefixed with an X is an experimental command.
- Commands which are not part of this specification, a standard or
- standards-track revision of this specification, or an
- IESG-approved experimental protocol, MUST use the X prefix.
-
- Any added untagged responses issued by an experimental command
- MUST also be prefixed with an X. Server implementations MUST NOT
- send any such untagged responses, unless the client requested it
- by issuing the associated experimental command.
-
- Example: C: a441 CAPABILITY
- S: * CAPABILITY IMAP4rev1 XPIG-LATIN
- S: a441 OK CAPABILITY completed
- C: A442 XPIG-LATIN
- S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
- S: A442 OK XPIG-LATIN ompleted-cay
-
-7. Server Responses
-
- Server responses are in three forms: status responses, server data,
- and command continuation request. The information contained in a
- server response, identified by "Contents:" in the response
- descriptions below, is described by function, not by syntax. The
- precise syntax of server responses is described in the Formal Syntax
- section.
-
- The client MUST be prepared to accept any response at all times.
-
- Status responses can be tagged or untagged. Tagged status responses
- indicate the completion result (OK, NO, or BAD status) of a client
- command, and have a tag matching the command.
-
- Some status responses, and all server data, are untagged. An
- untagged response is indicated by the token "*" instead of a tag.
- Untagged status responses indicate server greeting, or server status
-
-
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-
-
- that does not indicate the completion of a command (for example, an
- impending system shutdown alert). For historical reasons, untagged
- server data responses are also called "unsolicited data", although
- strictly speaking, only unilateral server data is truly
- "unsolicited".
-
- Certain server data MUST be recorded by the client when it is
- received; this is noted in the description of that data. Such data
- conveys critical information which affects the interpretation of all
- subsequent commands and responses (e.g., updates reflecting the
- creation or destruction of messages).
-
- Other server data SHOULD be recorded for later reference; if the
- client does not need to record the data, or if recording the data has
- no obvious purpose (e.g., a SEARCH response when no SEARCH command is
- in progress), the data SHOULD be ignored.
-
- An example of unilateral untagged server data occurs when the IMAP
- connection is in the selected state. In the selected state, the
- server checks the mailbox for new messages as part of command
- execution. Normally, this is part of the execution of every command;
- hence, a NOOP command suffices to check for new messages. If new
- messages are found, the server sends untagged EXISTS and RECENT
- responses reflecting the new size of the mailbox. Server
- implementations that offer multiple simultaneous access to the same
- mailbox SHOULD also send appropriate unilateral untagged FETCH and
- EXPUNGE responses if another agent changes the state of any message
- flags or expunges any messages.
-
- Command continuation request responses use the token "+" instead of a
- tag. These responses are sent by the server to indicate acceptance
- of an incomplete client command and readiness for the remainder of
- the command.
-
-7.1. Server Responses - Status Responses
-
- Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD
- can be tagged or untagged. PREAUTH and BYE are always untagged.
-
- Status responses MAY include an OPTIONAL "response code". A response
- code consists of data inside square brackets in the form of an atom,
- possibly followed by a space and arguments. The response code
- contains additional information or status codes for client software
- beyond the OK/NO/BAD condition, and are defined when there is a
- specific action that a client can take based upon the additional
- information.
-
-
-
-
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-
-
- The currently defined response codes are:
-
- ALERT
-
- The human-readable text contains a special alert that MUST be
- presented to the user in a fashion that calls the user's
- attention to the message.
-
- BADCHARSET
-
- Optionally followed by a parenthesized list of charsets. A
- SEARCH failed because the given charset is not supported by
- this implementation. If the optional list of charsets is
- given, this lists the charsets that are supported by this
- implementation.
-
- CAPABILITY
-
- Followed by a list of capabilities. This can appear in the
- initial OK or PREAUTH response to transmit an initial
- capabilities list. This makes it unnecessary for a client to
- send a separate CAPABILITY command if it recognizes this
- response.
-
- PARSE
-
- The human-readable text represents an error in parsing the
- [RFC-2822] header or [MIME-IMB] headers of a message in the
- mailbox.
-
- PERMANENTFLAGS
-
- Followed by a parenthesized list of flags, indicates which of
- the known flags the client can change permanently. Any flags
- that are in the FLAGS untagged response, but not the
- PERMANENTFLAGS list, can not be set permanently. If the client
- attempts to STORE a flag that is not in the PERMANENTFLAGS
- list, the server will either ignore the change or store the
- state change for the remainder of the current session only.
- The PERMANENTFLAGS list can also include the special flag \*,
- which indicates that it is possible to create new keywords by
- attempting to store those flags in the mailbox.
-
-
-
-
-
-
-
-
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-
-
- READ-ONLY
-
- The mailbox is selected read-only, or its access while selected
- has changed from read-write to read-only.
-
- READ-WRITE
-
- The mailbox is selected read-write, or its access while
- selected has changed from read-only to read-write.
-
- TRYCREATE
-
- An APPEND or COPY attempt is failing because the target mailbox
- does not exist (as opposed to some other reason). This is a
- hint to the client that the operation can succeed if the
- mailbox is first created by the CREATE command.
-
- UIDNEXT
-
- Followed by a decimal number, indicates the next unique
- identifier value. Refer to section 2.3.1.1 for more
- information.
-
- UIDVALIDITY
-
- Followed by a decimal number, indicates the unique identifier
- validity value. Refer to section 2.3.1.1 for more information.
-
- UNSEEN
-
- Followed by a decimal number, indicates the number of the first
- message without the \Seen flag set.
-
- Additional response codes defined by particular client or server
- implementations SHOULD be prefixed with an "X" until they are
- added to a revision of this protocol. Client implementations
- SHOULD ignore response codes that they do not recognize.
-
-7.1.1. OK Response
-
- Contents: OPTIONAL response code
- human-readable text
-
- The OK response indicates an information message from the server.
- When tagged, it indicates successful completion of the associated
- command. The human-readable text MAY be presented to the user as
- an information message. The untagged form indicates an
-
-
-
-
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-
-
- information-only message; the nature of the information MAY be
- indicated by a response code.
-
- The untagged form is also used as one of three possible greetings
- at connection startup. It indicates that the connection is not
- yet authenticated and that a LOGIN command is needed.
-
- Example: S: * OK IMAP4rev1 server ready
- C: A001 LOGIN fred blurdybloop
- S: * OK [ALERT] System shutdown in 10 minutes
- S: A001 OK LOGIN Completed
-
-
-7.1.2. NO Response
-
- Contents: OPTIONAL response code
- human-readable text
-
- The NO response indicates an operational error message from the
- server. When tagged, it indicates unsuccessful completion of the
- associated command. The untagged form indicates a warning; the
- command can still complete successfully. The human-readable text
- describes the condition.
-
- Example: C: A222 COPY 1:2 owatagusiam
- S: * NO Disk is 98% full, please delete unnecessary data
- S: A222 OK COPY completed
- C: A223 COPY 3:200 blurdybloop
- S: * NO Disk is 98% full, please delete unnecessary data
- S: * NO Disk is 99% full, please delete unnecessary data
- S: A223 NO COPY failed: disk is full
-
-
-7.1.3. BAD Response
-
- Contents: OPTIONAL response code
- human-readable text
-
- The BAD response indicates an error message from the server. When
- tagged, it reports a protocol-level error in the client's command;
- the tag indicates the command that caused the error. The untagged
- form indicates a protocol-level error for which the associated
- command can not be determined; it can also indicate an internal
- server failure. The human-readable text describes the condition.
-
-
-
-
-
-
-
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-
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-
-
- Example: C: ...very long command line...
- S: * BAD Command line too long
- C: ...empty line...
- S: * BAD Empty command line
- C: A443 EXPUNGE
- S: * BAD Disk crash, attempting salvage to a new disk!
- S: * OK Salvage successful, no data lost
- S: A443 OK Expunge completed
-
-
-7.1.4. PREAUTH Response
-
- Contents: OPTIONAL response code
- human-readable text
-
- The PREAUTH response is always untagged, and is one of three
- possible greetings at connection startup. It indicates that the
- connection has already been authenticated by external means; thus
- no LOGIN command is needed.
-
- Example: S: * PREAUTH IMAP4rev1 server logged in as Smith
-
-
-7.1.5. BYE Response
-
- Contents: OPTIONAL response code
- human-readable text
-
- The BYE response is always untagged, and indicates that the server
- is about to close the connection. The human-readable text MAY be
- displayed to the user in a status report by the client. The BYE
- response is sent under one of four conditions:
-
- 1) as part of a normal logout sequence. The server will close
- the connection after sending the tagged OK response to the
- LOGOUT command.
-
- 2) as a panic shutdown announcement. The server closes the
- connection immediately.
-
- 3) as an announcement of an inactivity autologout. The server
- closes the connection immediately.
-
- 4) as one of three possible greetings at connection startup,
- indicating that the server is not willing to accept a
- connection from this client. The server closes the
- connection immediately.
-
-
-
-
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-
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-
-
- The difference between a BYE that occurs as part of a normal
- LOGOUT sequence (the first case) and a BYE that occurs because of
- a failure (the other three cases) is that the connection closes
- immediately in the failure case. In all cases the client SHOULD
- continue to read response data from the server until the
- connection is closed; this will ensure that any pending untagged
- or completion responses are read and processed.
-
- Example: S: * BYE Autologout; idle for too long
-
-7.2. Server Responses - Server and Mailbox Status
-
- These responses are always untagged. This is how server and mailbox
- status data are transmitted from the server to the client. Many of
- these responses typically result from a command with the same name.
-
-7.2.1. CAPABILITY Response
-
- Contents: capability listing
-
- The CAPABILITY response occurs as a result of a CAPABILITY
- command. The capability listing contains a space-separated
- listing of capability names that the server supports. The
- capability listing MUST include the atom "IMAP4rev1".
-
- In addition, client and server implementations MUST implement the
- STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
- capabilities. See the Security Considerations section for
- important information.
-
- A capability name which begins with "AUTH=" indicates that the
- server supports that particular authentication mechanism.
-
- The LOGINDISABLED capability indicates that the LOGIN command is
- disabled, and that the server will respond with a tagged NO
- response to any attempt to use the LOGIN command even if the user
- name and password are valid. An IMAP client MUST NOT issue the
- LOGIN command if the server advertises the LOGINDISABLED
- capability.
-
- Other capability names indicate that the server supports an
- extension, revision, or amendment to the IMAP4rev1 protocol.
- Server responses MUST conform to this document until the client
- issues a command that uses the associated capability.
-
- Capability names MUST either begin with "X" or be standard or
- standards-track IMAP4rev1 extensions, revisions, or amendments
- registered with IANA. A server MUST NOT offer unregistered or
-
-
-
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-
-
- non-standard capability names, unless such names are prefixed with
- an "X".
-
- Client implementations SHOULD NOT require any capability name
- other than "IMAP4rev1", and MUST ignore any unknown capability
- names.
-
- A server MAY send capabilities automatically, by using the
- CAPABILITY response code in the initial PREAUTH or OK responses,
- and by sending an updated CAPABILITY response code in the tagged
- OK response as part of a successful authentication. It is
- unnecessary for a client to send a separate CAPABILITY command if
- it recognizes these automatic capabilities.
-
- Example: S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI XPIG-LATIN
-
-
-7.2.2. LIST Response
-
- Contents: name attributes
- hierarchy delimiter
- name
-
- The LIST response occurs as a result of a LIST command. It
- returns a single name that matches the LIST specification. There
- can be multiple LIST responses for a single LIST command.
-
- Four name attributes are defined:
-
- \Noinferiors
- It is not possible for any child levels of hierarchy to exist
- under this name; no child levels exist now and none can be
- created in the future.
-
- \Noselect
- It is not possible to use this name as a selectable mailbox.
-
- \Marked
- The mailbox has been marked "interesting" by the server; the
- mailbox probably contains messages that have been added since
- the last time the mailbox was selected.
-
- \Unmarked
- The mailbox does not contain any additional messages since the
- last time the mailbox was selected.
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- If it is not feasible for the server to determine whether or not
- the mailbox is "interesting", or if the name is a \Noselect name,
- the server SHOULD NOT send either \Marked or \Unmarked.
-
- The hierarchy delimiter is a character used to delimit levels of
- hierarchy in a mailbox name. A client can use it to create child
- mailboxes, and to search higher or lower levels of naming
- hierarchy. All children of a top-level hierarchy node MUST use
- the same separator character. A NIL hierarchy delimiter means
- that no hierarchy exists; the name is a "flat" name.
-
- The name represents an unambiguous left-to-right hierarchy, and
- MUST be valid for use as a reference in LIST and LSUB commands.
- Unless \Noselect is indicated, the name MUST also be valid as an
- argument for commands, such as SELECT, that accept mailbox names.
-
- Example: S: * LIST (\Noselect) "/" ~/Mail/foo
-
-
-7.2.3. LSUB Response
-
- Contents: name attributes
- hierarchy delimiter
- name
-
- The LSUB response occurs as a result of an LSUB command. It
- returns a single name that matches the LSUB specification. There
- can be multiple LSUB responses for a single LSUB command. The
- data is identical in format to the LIST response.
-
- Example: S: * LSUB () "." #news.comp.mail.misc
-
-
-7.2.4 STATUS Response
-
- Contents: name
- status parenthesized list
-
- The STATUS response occurs as a result of an STATUS command. It
- returns the mailbox name that matches the STATUS specification and
- the requested mailbox status information.
-
- Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
-
-
-
-
-
-
-
-
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-
-
-7.2.5. SEARCH Response
-
- Contents: zero or more numbers
-
- The SEARCH response occurs as a result of a SEARCH or UID SEARCH
- command. The number(s) refer to those messages that match the
- search criteria. For SEARCH, these are message sequence numbers;
- for UID SEARCH, these are unique identifiers. Each number is
- delimited by a space.
-
- Example: S: * SEARCH 2 3 6
-
-
-7.2.6. FLAGS Response
-
- Contents: flag parenthesized list
-
- The FLAGS response occurs as a result of a SELECT or EXAMINE
- command. The flag parenthesized list identifies the flags (at a
- minimum, the system-defined flags) that are applicable for this
- mailbox. Flags other than the system flags can also exist,
- depending on server implementation.
-
- The update from the FLAGS response MUST be recorded by the client.
-
- Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
-
-
-7.3. Server Responses - Mailbox Size
-
- These responses are always untagged. This is how changes in the size
- of the mailbox are transmitted from the server to the client.
- Immediately following the "*" token is a number that represents a
- message count.
-
-7.3.1. EXISTS Response
-
- Contents: none
-
- The EXISTS response reports the number of messages in the mailbox.
- This response occurs as a result of a SELECT or EXAMINE command,
- and if the size of the mailbox changes (e.g., new messages).
-
- The update from the EXISTS response MUST be recorded by the
- client.
-
- Example: S: * 23 EXISTS
-
-
-
-
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-
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-
-
-7.3.2. RECENT Response
-
- Contents: none
-
- The RECENT response reports the number of messages with the
- \Recent flag set. This response occurs as a result of a SELECT or
- EXAMINE command, and if the size of the mailbox changes (e.g., new
- messages).
-
- Note: It is not guaranteed that the message sequence
- numbers of recent messages will be a contiguous range of
- the highest n messages in the mailbox (where n is the
- value reported by the RECENT response). Examples of
- situations in which this is not the case are: multiple
- clients having the same mailbox open (the first session
- to be notified will see it as recent, others will
- probably see it as non-recent), and when the mailbox is
- re-ordered by a non-IMAP agent.
-
- The only reliable way to identify recent messages is to
- look at message flags to see which have the \Recent flag
- set, or to do a SEARCH RECENT.
-
- The update from the RECENT response MUST be recorded by the
- client.
-
- Example: S: * 5 RECENT
-
-
-7.4. Server Responses - Message Status
-
- These responses are always untagged. This is how message data are
- transmitted from the server to the client, often as a result of a
- command with the same name. Immediately following the "*" token is a
- number that represents a message sequence number.
-
-7.4.1. EXPUNGE Response
-
- Contents: none
-
- The EXPUNGE response reports that the specified message sequence
- number has been permanently removed from the mailbox. The message
- sequence number for each successive message in the mailbox is
- immediately decremented by 1, and this decrement is reflected in
- message sequence numbers in subsequent responses (including other
- untagged EXPUNGE responses).
-
-
-
-
-
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-
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-
-
- The EXPUNGE response also decrements the number of messages in the
- mailbox; it is not necessary to send an EXISTS response with the
- new value.
-
- As a result of the immediate decrement rule, message sequence
- numbers that appear in a set of successive EXPUNGE responses
- depend upon whether the messages are removed starting from lower
- numbers to higher numbers, or from higher numbers to lower
- numbers. For example, if the last 5 messages in a 9-message
- mailbox are expunged, a "lower to higher" server will send five
- untagged EXPUNGE responses for message sequence number 5, whereas
- a "higher to lower server" will send successive untagged EXPUNGE
- responses for message sequence numbers 9, 8, 7, 6, and 5.
-
- An EXPUNGE response MUST NOT be sent when no command is in
- progress, nor while responding to a FETCH, STORE, or SEARCH
- command. This rule is necessary to prevent a loss of
- synchronization of message sequence numbers between client and
- server. A command is not "in progress" until the complete command
- has been received; in particular, a command is not "in progress"
- during the negotiation of command continuation.
-
- Note: UID FETCH, UID STORE, and UID SEARCH are different
- commands from FETCH, STORE, and SEARCH. An EXPUNGE
- response MAY be sent during a UID command.
-
- The update from the EXPUNGE response MUST be recorded by the
- client.
-
- Example: S: * 44 EXPUNGE
-
-
-7.4.2. FETCH Response
-
- Contents: message data
-
- The FETCH response returns data about a message to the client.
- The data are pairs of data item names and their values in
- parentheses. This response occurs as the result of a FETCH or
- STORE command, as well as by unilateral server decision (e.g.,
- flag updates).
-
- The current data items are:
-
- BODY
- A form of BODYSTRUCTURE without extension data.
-
-
-
-
-
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-
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-
-
- BODY[<section>]<<origin octet>>
- A string expressing the body contents of the specified section.
- The string SHOULD be interpreted by the client according to the
- content transfer encoding, body type, and subtype.
-
- If the origin octet is specified, this string is a substring of
- the entire body contents, starting at that origin octet. This
- means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
- truncated.
-
- Note: The origin octet facility MUST NOT be used by a server
- in a FETCH response unless the client specifically requested
- it by means of a FETCH of a BODY[<section>]<<partial>> data
- item.
-
- 8-bit textual data is permitted if a [CHARSET] identifier is
- part of the body parameter parenthesized list for this section.
- Note that headers (part specifiers HEADER or MIME, or the
- header portion of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
- characters are not permitted in headers. Note also that the
- [RFC-2822] delimiting blank line between the header and the
- body is not affected by header line subsetting; the blank line
- is always included as part of header data, except in the case
- of a message which has no body and no blank line.
-
- Non-textual data such as binary data MUST be transfer encoded
- into a textual form, such as BASE64, prior to being sent to the
- client. To derive the original binary data, the client MUST
- decode the transfer encoded string.
-
- BODYSTRUCTURE
- A parenthesized list that describes the [MIME-IMB] body
- structure of a message. This is computed by the server by
- parsing the [MIME-IMB] header fields, defaulting various fields
- as necessary.
-
- For example, a simple text message of 48 lines and 2279 octets
- can have a body structure of: ("TEXT" "PLAIN" ("CHARSET"
- "US-ASCII") NIL NIL "7BIT" 2279 48)
-
- Multiple parts are indicated by parenthesis nesting. Instead
- of a body type as the first element of the parenthesized list,
- there is a sequence of one or more nested body structures. The
- second element of the parenthesized list is the multipart
- subtype (mixed, digest, parallel, alternative, etc.).
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- For example, a two part message consisting of a text and a
- BASE64-encoded text attachment can have a body structure of:
- (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
- 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
- "<960723163407.20117h@cac.washington.edu>" "Compiler diff"
- "BASE64" 4554 73) "MIXED")
-
- Extension data follows the multipart subtype. Extension data
- is never returned with the BODY fetch, but can be returned with
- a BODYSTRUCTURE fetch. Extension data, if present, MUST be in
- the defined order. The extension data of a multipart body part
- are in the following order:
-
- body parameter parenthesized list
- A parenthesized list of attribute/value pairs [e.g., ("foo"
- "bar" "baz" "rag") where "bar" is the value of "foo", and
- "rag" is the value of "baz"] as defined in [MIME-IMB].
-
- body disposition
- A parenthesized list, consisting of a disposition type
- string, followed by a parenthesized list of disposition
- attribute/value pairs as defined in [DISPOSITION].
-
- body language
- A string or parenthesized list giving the body language
- value as defined in [LANGUAGE-TAGS].
-
- body location
- A string list giving the body content URI as defined in
- [LOCATION].
-
- Any following extension data are not yet defined in this
- version of the protocol. Such extension data can consist of
- zero or more NILs, strings, numbers, or potentially nested
- parenthesized lists of such data. Client implementations that
- do a BODYSTRUCTURE fetch MUST be prepared to accept such
- extension data. Server implementations MUST NOT send such
- extension data until it has been defined by a revision of this
- protocol.
-
- The basic fields of a non-multipart body part are in the
- following order:
-
- body type
- A string giving the content media type name as defined in
- [MIME-IMB].
-
-
-
-
-
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-
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-
-
- body subtype
- A string giving the content subtype name as defined in
- [MIME-IMB].
-
- body parameter parenthesized list
- A parenthesized list of attribute/value pairs [e.g., ("foo"
- "bar" "baz" "rag") where "bar" is the value of "foo" and
- "rag" is the value of "baz"] as defined in [MIME-IMB].
-
- body id
- A string giving the content id as defined in [MIME-IMB].
-
- body description
- A string giving the content description as defined in
- [MIME-IMB].
-
- body encoding
- A string giving the content transfer encoding as defined in
- [MIME-IMB].
-
- body size
- A number giving the size of the body in octets. Note that
- this size is the size in its transfer encoding and not the
- resulting size after any decoding.
-
- A body type of type MESSAGE and subtype RFC822 contains,
- immediately after the basic fields, the envelope structure,
- body structure, and size in text lines of the encapsulated
- message.
-
- A body type of type TEXT contains, immediately after the basic
- fields, the size of the body in text lines. Note that this
- size is the size in its content transfer encoding and not the
- resulting size after any decoding.
-
- Extension data follows the basic fields and the type-specific
- fields listed above. Extension data is never returned with the
- BODY fetch, but can be returned with a BODYSTRUCTURE fetch.
- Extension data, if present, MUST be in the defined order.
-
- The extension data of a non-multipart body part are in the
- following order:
-
- body MD5
- A string giving the body MD5 value as defined in [MD5].
-
-
-
-
-
-
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-
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-
-
- body disposition
- A parenthesized list with the same content and function as
- the body disposition for a multipart body part.
-
- body language
- A string or parenthesized list giving the body language
- value as defined in [LANGUAGE-TAGS].
-
- body location
- A string list giving the body content URI as defined in
- [LOCATION].
-
- Any following extension data are not yet defined in this
- version of the protocol, and would be as described above under
- multipart extension data.
-
- ENVELOPE
- A parenthesized list that describes the envelope structure of a
- message. This is computed by the server by parsing the
- [RFC-2822] header into the component parts, defaulting various
- fields as necessary.
-
- The fields of the envelope structure are in the following
- order: date, subject, from, sender, reply-to, to, cc, bcc,
- in-reply-to, and message-id. The date, subject, in-reply-to,
- and message-id fields are strings. The from, sender, reply-to,
- to, cc, and bcc fields are parenthesized lists of address
- structures.
-
- An address structure is a parenthesized list that describes an
- electronic mail address. The fields of an address structure
- are in the following order: personal name, [SMTP]
- at-domain-list (source route), mailbox name, and host name.
-
- [RFC-2822] group syntax is indicated by a special form of
- address structure in which the host name field is NIL. If the
- mailbox name field is also NIL, this is an end of group marker
- (semi-colon in RFC 822 syntax). If the mailbox name field is
- non-NIL, this is a start of group marker, and the mailbox name
- field holds the group name phrase.
-
- If the Date, Subject, In-Reply-To, and Message-ID header lines
- are absent in the [RFC-2822] header, the corresponding member
- of the envelope is NIL; if these header lines are present but
- empty the corresponding member of the envelope is the empty
- string.
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- Note: some servers may return a NIL envelope member in the
- "present but empty" case. Clients SHOULD treat NIL and
- empty string as identical.
-
- Note: [RFC-2822] requires that all messages have a valid
- Date header. Therefore, the date member in the envelope can
- not be NIL or the empty string.
-
- Note: [RFC-2822] requires that the In-Reply-To and
- Message-ID headers, if present, have non-empty content.
- Therefore, the in-reply-to and message-id members in the
- envelope can not be the empty string.
-
- If the From, To, cc, and bcc header lines are absent in the
- [RFC-2822] header, or are present but empty, the corresponding
- member of the envelope is NIL.
-
- If the Sender or Reply-To lines are absent in the [RFC-2822]
- header, or are present but empty, the server sets the
- corresponding member of the envelope to be the same value as
- the from member (the client is not expected to know to do
- this).
-
- Note: [RFC-2822] requires that all messages have a valid
- From header. Therefore, the from, sender, and reply-to
- members in the envelope can not be NIL.
-
- FLAGS
- A parenthesized list of flags that are set for this message.
-
- INTERNALDATE
- A string representing the internal date of the message.
-
- RFC822
- Equivalent to BODY[].
-
- RFC822.HEADER
- Equivalent to BODY[HEADER]. Note that this did not result in
- \Seen being set, because RFC822.HEADER response data occurs as
- a result of a FETCH of RFC822.HEADER. BODY[HEADER] response
- data occurs as a result of a FETCH of BODY[HEADER] (which sets
- \Seen) or BODY.PEEK[HEADER] (which does not set \Seen).
-
- RFC822.SIZE
- A number expressing the [RFC-2822] size of the message.
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- RFC822.TEXT
- Equivalent to BODY[TEXT].
-
- UID
- A number expressing the unique identifier of the message.
-
-
- Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
-
-
-7.5. Server Responses - Command Continuation Request
-
- The command continuation request response is indicated by a "+" token
- instead of a tag. This form of response indicates that the server is
- ready to accept the continuation of a command from the client. The
- remainder of this response is a line of text.
-
- This response is used in the AUTHENTICATE command to transmit server
- data to the client, and request additional client data. This
- response is also used if an argument to any command is a literal.
-
- The client is not permitted to send the octets of the literal unless
- the server indicates that it is expected. This permits the server to
- process commands and reject errors on a line-by-line basis. The
- remainder of the command, including the CRLF that terminates a
- command, follows the octets of the literal. If there are any
- additional command arguments, the literal octets are followed by a
- space and those arguments.
-
- Example: C: A001 LOGIN {11}
- S: + Ready for additional command text
- C: FRED FOOBAR {7}
- S: + Ready for additional command text
- C: fat man
- S: A001 OK LOGIN completed
- C: A044 BLURDYBLOOP {102856}
- S: A044 BAD No such command as "BLURDYBLOOP"
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-8. Sample IMAP4rev1 connection
-
- The following is a transcript of an IMAP4rev1 connection. A long
- line in this sample is broken for editorial clarity.
-
-S: * OK IMAP4rev1 Service Ready
-C: a001 login mrc secret
-S: a001 OK LOGIN completed
-C: a002 select inbox
-S: * 18 EXISTS
-S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
-S: * 2 RECENT
-S: * OK [UNSEEN 17] Message 17 is the first unseen message
-S: * OK [UIDVALIDITY 3857529045] UIDs valid
-S: a002 OK [READ-WRITE] SELECT completed
-C: a003 fetch 12 full
-S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
- RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
- "IMAP4rev1 WG mtg summary and minutes"
- (("Terry Gray" NIL "gray" "cac.washington.edu"))
- (("Terry Gray" NIL "gray" "cac.washington.edu"))
- (("Terry Gray" NIL "gray" "cac.washington.edu"))
- ((NIL NIL "imap" "cac.washington.edu"))
- ((NIL NIL "minutes" "CNRI.Reston.VA.US")
- ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL
- "<B27397-0100000@cac.washington.edu>")
- BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028
- 92))
-S: a003 OK FETCH completed
-C: a004 fetch 12 body[header]
-S: * 12 FETCH (BODY[HEADER] {342}
-S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
-S: From: Terry Gray <gray@cac.washington.edu>
-S: Subject: IMAP4rev1 WG mtg summary and minutes
-S: To: imap@cac.washington.edu
-S: cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@MIT.EDU>
-S: Message-Id: <B27397-0100000@cac.washington.edu>
-S: MIME-Version: 1.0
-S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
-S:
-S: )
-S: a004 OK FETCH completed
-C: a005 store 12 +flags \deleted
-S: * 12 FETCH (FLAGS (\Seen \Deleted))
-S: a005 OK +FLAGS completed
-C: a006 logout
-S: * BYE IMAP4rev1 server terminating connection
-S: a006 OK LOGOUT completed
-
-
-
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-
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-
-
-9. Formal Syntax
-
- The following syntax specification uses the Augmented Backus-Naur
- Form (ABNF) notation as specified in [ABNF].
-
- In the case of alternative or optional rules in which a later rule
- overlaps an earlier rule, the rule which is listed earlier MUST take
- priority. For example, "\Seen" when parsed as a flag is the \Seen
- flag name and not a flag-extension, even though "\Seen" can be parsed
- as a flag-extension. Some, but not all, instances of this rule are
- noted below.
-
- Note: [ABNF] rules MUST be followed strictly; in
- particular:
-
- (1) Except as noted otherwise, all alphabetic characters
- are case-insensitive. The use of upper or lower case
- characters to define token strings is for editorial clarity
- only. Implementations MUST accept these strings in a
- case-insensitive fashion.
-
- (2) In all cases, SP refers to exactly one space. It is
- NOT permitted to substitute TAB, insert additional spaces,
- or otherwise treat SP as being equivalent to LWSP.
-
- (3) The ASCII NUL character, %x00, MUST NOT be used at any
- time.
-
-address = "(" addr-name SP addr-adl SP addr-mailbox SP
- addr-host ")"
-
-addr-adl = nstring
- ; Holds route from [RFC-2822] route-addr if
- ; non-NIL
-
-addr-host = nstring
- ; NIL indicates [RFC-2822] group syntax.
- ; Otherwise, holds [RFC-2822] domain name
-
-addr-mailbox = nstring
- ; NIL indicates end of [RFC-2822] group; if
- ; non-NIL and addr-host is NIL, holds
- ; [RFC-2822] group name.
- ; Otherwise, holds [RFC-2822] local-part
- ; after removing [RFC-2822] quoting
-
-
-
-
-
-
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-
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-
-
-addr-name = nstring
- ; If non-NIL, holds phrase from [RFC-2822]
- ; mailbox after removing [RFC-2822] quoting
-
-append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
- literal
-
-astring = 1*ASTRING-CHAR / string
-
-ASTRING-CHAR = ATOM-CHAR / resp-specials
-
-atom = 1*ATOM-CHAR
-
-ATOM-CHAR = <any CHAR except atom-specials>
-
-atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards /
- quoted-specials / resp-specials
-
-authenticate = "AUTHENTICATE" SP auth-type *(CRLF base64)
-
-auth-type = atom
- ; Defined by [SASL]
-
-base64 = *(4base64-char) [base64-terminal]
-
-base64-char = ALPHA / DIGIT / "+" / "/"
- ; Case-sensitive
-
-base64-terminal = (2base64-char "==") / (3base64-char "=")
-
-body = "(" (body-type-1part / body-type-mpart) ")"
-
-body-extension = nstring / number /
- "(" body-extension *(SP body-extension) ")"
- ; Future expansion. Client implementations
- ; MUST accept body-extension fields. Server
- ; implementations MUST NOT generate
- ; body-extension fields except as defined by
- ; future standard or standards-track
- ; revisions of this specification.
-
-body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
- [SP body-fld-loc *(SP body-extension)]]]
- ; MUST NOT be returned on non-extensible
- ; "BODY" fetch
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
-body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang
- [SP body-fld-loc *(SP body-extension)]]]
- ; MUST NOT be returned on non-extensible
- ; "BODY" fetch
-
-body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP
- body-fld-enc SP body-fld-octets
-
-body-fld-desc = nstring
-
-body-fld-dsp = "(" string SP body-fld-param ")" / nil
-
-body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
- "QUOTED-PRINTABLE") DQUOTE) / string
-
-body-fld-id = nstring
-
-body-fld-lang = nstring / "(" string *(SP string) ")"
-
-body-fld-loc = nstring
-
-body-fld-lines = number
-
-body-fld-md5 = nstring
-
-body-fld-octets = number
-
-body-fld-param = "(" string SP string *(SP string SP string) ")" / nil
-
-body-type-1part = (body-type-basic / body-type-msg / body-type-text)
- [SP body-ext-1part]
-
-body-type-basic = media-basic SP body-fields
- ; MESSAGE subtype MUST NOT be "RFC822"
-
-body-type-mpart = 1*body SP media-subtype
- [SP body-ext-mpart]
-
-body-type-msg = media-message SP body-fields SP envelope
- SP body SP body-fld-lines
-
-body-type-text = media-text SP body-fields SP body-fld-lines
-
-capability = ("AUTH=" auth-type) / atom
- ; New capabilities MUST begin with "X" or be
- ; registered with IANA as standard or
- ; standards-track
-
-
-
-
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-
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-
-
-capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev1"
- *(SP capability)
- ; Servers MUST implement the STARTTLS, AUTH=PLAIN,
- ; and LOGINDISABLED capabilities
- ; Servers which offer RFC 1730 compatibility MUST
- ; list "IMAP4" as the first capability.
-
-CHAR8 = %x01-ff
- ; any OCTET except NUL, %x00
-
-command = tag SP (command-any / command-auth / command-nonauth /
- command-select) CRLF
- ; Modal based on state
-
-command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command
- ; Valid in all states
-
-command-auth = append / create / delete / examine / list / lsub /
- rename / select / status / subscribe / unsubscribe
- ; Valid only in Authenticated or Selected state
-
-command-nonauth = login / authenticate / "STARTTLS"
- ; Valid only when in Not Authenticated state
-
-command-select = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
- uid / search
- ; Valid only when in Selected state
-
-continue-req = "+" SP (resp-text / base64) CRLF
-
-copy = "COPY" SP sequence-set SP mailbox
-
-create = "CREATE" SP mailbox
- ; Use of INBOX gives a NO error
-
-date = date-text / DQUOTE date-text DQUOTE
-
-date-day = 1*2DIGIT
- ; Day of month
-
-date-day-fixed = (SP DIGIT) / 2DIGIT
- ; Fixed-format version of date-day
-
-date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
- "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
-
-date-text = date-day "-" date-month "-" date-year
-
-
-
-
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-
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-
-
-date-year = 4DIGIT
-
-date-time = DQUOTE date-day-fixed "-" date-month "-" date-year
- SP time SP zone DQUOTE
-
-delete = "DELETE" SP mailbox
- ; Use of INBOX gives a NO error
-
-digit-nz = %x31-39
- ; 1-9
-
-envelope = "(" env-date SP env-subject SP env-from SP
- env-sender SP env-reply-to SP env-to SP env-cc SP
- env-bcc SP env-in-reply-to SP env-message-id ")"
-
-env-bcc = "(" 1*address ")" / nil
-
-env-cc = "(" 1*address ")" / nil
-
-env-date = nstring
-
-env-from = "(" 1*address ")" / nil
-
-env-in-reply-to = nstring
-
-env-message-id = nstring
-
-env-reply-to = "(" 1*address ")" / nil
-
-env-sender = "(" 1*address ")" / nil
-
-env-subject = nstring
-
-env-to = "(" 1*address ")" / nil
-
-examine = "EXAMINE" SP mailbox
-
-fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
- fetch-att / "(" fetch-att *(SP fetch-att) ")")
-
-fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
- "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
- "BODY" ["STRUCTURE"] / "UID" /
- "BODY" section ["<" number "." nz-number ">"] /
- "BODY.PEEK" section ["<" number "." nz-number ">"]
-
-
-
-
-
-
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-
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-
-
-flag = "\Answered" / "\Flagged" / "\Deleted" /
- "\Seen" / "\Draft" / flag-keyword / flag-extension
- ; Does not include "\Recent"
-
-flag-extension = "\" atom
- ; Future expansion. Client implementations
- ; MUST accept flag-extension flags. Server
- ; implementations MUST NOT generate
- ; flag-extension flags except as defined by
- ; future standard or standards-track
- ; revisions of this specification.
-
-flag-fetch = flag / "\Recent"
-
-flag-keyword = atom
-
-flag-list = "(" [flag *(SP flag)] ")"
-
-flag-perm = flag / "\*"
-
-greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF
-
-header-fld-name = astring
-
-header-list = "(" header-fld-name *(SP header-fld-name) ")"
-
-list = "LIST" SP mailbox SP list-mailbox
-
-list-mailbox = 1*list-char / string
-
-list-char = ATOM-CHAR / list-wildcards / resp-specials
-
-list-wildcards = "%" / "*"
-
-literal = "{" number "}" CRLF *CHAR8
- ; Number represents the number of CHAR8s
-
-login = "LOGIN" SP userid SP password
-
-lsub = "LSUB" SP mailbox SP list-mailbox
-
-
-
-
-
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
-mailbox = "INBOX" / astring
- ; INBOX is case-insensitive. All case variants of
- ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX
- ; not as an astring. An astring which consists of
- ; the case-insensitive sequence "I" "N" "B" "O" "X"
- ; is considered to be INBOX and not an astring.
- ; Refer to section 5.1 for further
- ; semantic details of mailbox names.
-
-mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list /
- "LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
- "STATUS" SP mailbox SP "(" [status-att-list] ")" /
- number SP "EXISTS" / number SP "RECENT"
-
-mailbox-list = "(" [mbx-list-flags] ")" SP
- (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
-
-mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag
- *(SP mbx-list-oflag) /
- mbx-list-oflag *(SP mbx-list-oflag)
-
-mbx-list-oflag = "\Noinferiors" / flag-extension
- ; Other flags; multiple possible per LIST response
-
-mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked"
- ; Selectability flags; only one per LIST response
-
-media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" /
- "MESSAGE" / "VIDEO") DQUOTE) / string) SP
- media-subtype
- ; Defined in [MIME-IMT]
-
-media-message = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
- ; Defined in [MIME-IMT]
-
-media-subtype = string
- ; Defined in [MIME-IMT]
-
-media-text = DQUOTE "TEXT" DQUOTE SP media-subtype
- ; Defined in [MIME-IMT]
-
-message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))
-
-msg-att = "(" (msg-att-dynamic / msg-att-static)
- *(SP (msg-att-dynamic / msg-att-static)) ")"
-
-msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
- ; MAY change for a message
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
-msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
- "RFC822" [".HEADER" / ".TEXT"] SP nstring /
- "RFC822.SIZE" SP number /
- "BODY" ["STRUCTURE"] SP body /
- "BODY" section ["<" number ">"] SP nstring /
- "UID" SP uniqueid
- ; MUST NOT change for a message
-
-nil = "NIL"
-
-nstring = string / nil
-
-number = 1*DIGIT
- ; Unsigned 32-bit integer
- ; (0 <= n < 4,294,967,296)
-
-nz-number = digit-nz *DIGIT
- ; Non-zero unsigned 32-bit integer
- ; (0 < n < 4,294,967,296)
-
-password = astring
-
-quoted = DQUOTE *QUOTED-CHAR DQUOTE
-
-QUOTED-CHAR = <any TEXT-CHAR except quoted-specials> /
- "\" quoted-specials
-
-quoted-specials = DQUOTE / "\"
-
-rename = "RENAME" SP mailbox SP mailbox
- ; Use of INBOX as a destination gives a NO error
-
-response = *(continue-req / response-data) response-done
-
-response-data = "*" SP (resp-cond-state / resp-cond-bye /
- mailbox-data / message-data / capability-data) CRLF
-
-response-done = response-tagged / response-fatal
-
-response-fatal = "*" SP resp-cond-bye CRLF
- ; Server closes connection immediately
-
-response-tagged = tag SP resp-cond-state CRLF
-
-resp-cond-auth = ("OK" / "PREAUTH") SP resp-text
- ; Authentication condition
-
-
-
-
-
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-
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-
-
-resp-cond-bye = "BYE" SP resp-text
-
-resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
- ; Status condition
-
-resp-specials = "]"
-
-resp-text = ["[" resp-text-code "]" SP] text
-
-resp-text-code = "ALERT" /
- "BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
- capability-data / "PARSE" /
- "PERMANENTFLAGS" SP "("
- [flag-perm *(SP flag-perm)] ")" /
- "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
- "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
- "UNSEEN" SP nz-number /
- atom [SP 1*<any TEXT-CHAR except "]">]
-
-search = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
- ; CHARSET argument to MUST be registered with IANA
-
-search-key = "ALL" / "ANSWERED" / "BCC" SP astring /
- "BEFORE" SP date / "BODY" SP astring /
- "CC" SP astring / "DELETED" / "FLAGGED" /
- "FROM" SP astring / "KEYWORD" SP flag-keyword /
- "NEW" / "OLD" / "ON" SP date / "RECENT" / "SEEN" /
- "SINCE" SP date / "SUBJECT" SP astring /
- "TEXT" SP astring / "TO" SP astring /
- "UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
- "UNKEYWORD" SP flag-keyword / "UNSEEN" /
- ; Above this line were in [IMAP2]
- "DRAFT" / "HEADER" SP header-fld-name SP astring /
- "LARGER" SP number / "NOT" SP search-key /
- "OR" SP search-key SP search-key /
- "SENTBEFORE" SP date / "SENTON" SP date /
- "SENTSINCE" SP date / "SMALLER" SP number /
- "UID" SP sequence-set / "UNDRAFT" / sequence-set /
- "(" search-key *(SP search-key) ")"
-
-section = "[" [section-spec] "]"
-
-section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
- "TEXT"
- ; top-level or MESSAGE/RFC822 part
-
-section-part = nz-number *("." nz-number)
- ; body part nesting
-
-
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-
-
-section-spec = section-msgtext / (section-part ["." section-text])
-
-section-text = section-msgtext / "MIME"
- ; text other than actual body part (headers, etc.)
-
-select = "SELECT" SP mailbox
-
-seq-number = nz-number / "*"
- ; message sequence number (COPY, FETCH, STORE
- ; commands) or unique identifier (UID COPY,
- ; UID FETCH, UID STORE commands).
- ; * represents the largest number in use. In
- ; the case of message sequence numbers, it is
- ; the number of messages in a non-empty mailbox.
- ; In the case of unique identifiers, it is the
- ; unique identifier of the last message in the
- ; mailbox or, if the mailbox is empty, the
- ; mailbox's current UIDNEXT value.
- ; The server should respond with a tagged BAD
- ; response to a command that uses a message
- ; sequence number greater than the number of
- ; messages in the selected mailbox. This
- ; includes "*" if the selected mailbox is empty.
-
-seq-range = seq-number ":" seq-number
- ; two seq-number values and all values between
- ; these two regardless of order.
- ; Example: 2:4 and 4:2 are equivalent and indicate
- ; values 2, 3, and 4.
- ; Example: a unique identifier sequence range of
- ; 3291:* includes the UID of the last message in
- ; the mailbox, even if that value is less than 3291.
-
-sequence-set = (seq-number / seq-range) *("," sequence-set)
- ; set of seq-number values, regardless of order.
- ; Servers MAY coalesce overlaps and/or execute the
- ; sequence in any order.
- ; Example: a message sequence number set of
- ; 2,4:7,9,12:* for a mailbox with 15 messages is
- ; equivalent to 2,4,5,6,7,9,12,13,14,15
- ; Example: a message sequence number set of *:4,5:7
- ; for a mailbox with 10 messages is equivalent to
- ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
- ; overlap coalesced to be 4,5,6,7,8,9,10.
-
-status = "STATUS" SP mailbox SP
- "(" status-att *(SP status-att) ")"
-
-
-
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-
-
-status-att = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
- "UNSEEN"
-
-status-att-list = status-att SP number *(SP status-att SP number)
-
-store = "STORE" SP sequence-set SP store-att-flags
-
-store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
- (flag-list / (flag *(SP flag)))
-
-string = quoted / literal
-
-subscribe = "SUBSCRIBE" SP mailbox
-
-tag = 1*<any ASTRING-CHAR except "+">
-
-text = 1*TEXT-CHAR
-
-TEXT-CHAR = <any CHAR except CR and LF>
-
-time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
- ; Hours minutes seconds
-
-uid = "UID" SP (copy / fetch / search / store)
- ; Unique identifiers used instead of message
- ; sequence numbers
-
-uniqueid = nz-number
- ; Strictly ascending
-
-unsubscribe = "UNSUBSCRIBE" SP mailbox
-
-userid = astring
-
-x-command = "X" atom <experimental command arguments>
-
-zone = ("+" / "-") 4DIGIT
- ; Signed four-digit value of hhmm representing
- ; hours and minutes east of Greenwich (that is,
- ; the amount that the given time differs from
- ; Universal Time). Subtracting the timezone
- ; from the given time will give the UT form.
- ; The Universal Time zone is "+0000".
-
-
-
-
-
-
-
-
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-
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-
-
-10. Author's Note
-
- This document is a revision or rewrite of earlier documents, and
- supercedes the protocol specification in those documents: RFC 2060,
- RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.
-
-11. Security Considerations
-
- IMAP4rev1 protocol transactions, including electronic mail data, are
- sent in the clear over the network unless protection from snooping is
- negotiated. This can be accomplished either by the use of STARTTLS,
- negotiated privacy protection in the AUTHENTICATE command, or some
- other protection mechanism.
-
-11.1. STARTTLS Security Considerations
-
- The specification of the STARTTLS command and LOGINDISABLED
- capability in this document replaces that in [IMAP-TLS]. [IMAP-TLS]
- remains normative for the PLAIN [SASL] authenticator.
-
- IMAP client and server implementations MUST implement the
- TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite, and SHOULD implement the
- TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
- important as it assures that any two compliant implementations can be
- configured to interoperate. All other cipher suites are OPTIONAL.
- Note that this is a change from section 2.1 of [IMAP-TLS].
-
- During the [TLS] negotiation, the client MUST check its understanding
- of the server hostname against the server's identity as presented in
- the server Certificate message, in order to prevent man-in-the-middle
- attacks. If the match fails, the client SHOULD either ask for
- explicit user confirmation, or terminate the connection and indicate
- that the server's identity is suspect. Matching is performed
- according to these rules:
-
- The client MUST use the server hostname it used to open the
- connection as the value to compare against the server name
- as expressed in the server certificate. The client MUST
- NOT use any form of the server hostname derived from an
- insecure remote source (e.g., insecure DNS lookup). CNAME
- canonicalization is not done.
-
- If a subjectAltName extension of type dNSName is present in
- the certificate, it SHOULD be used as the source of the
- server's identity.
-
- Matching is case-insensitive.
-
-
-
-
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-
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-
-
- A "*" wildcard character MAY be used as the left-most name
- component in the certificate. For example, *.example.com
- would match a.example.com, foo.example.com, etc. but would
- not match example.com.
-
- If the certificate contains multiple names (e.g., more than
- one dNSName field), then a match with any one of the fields
- is considered acceptable.
-
- Both the client and server MUST check the result of the STARTTLS
- command and subsequent [TLS] negotiation to see whether acceptable
- authentication or privacy was achieved.
-
-11.2. Other Security Considerations
-
- A server error message for an AUTHENTICATE command which fails due to
- invalid credentials SHOULD NOT detail why the credentials are
- invalid.
-
- Use of the LOGIN command sends passwords in the clear. This can be
- avoided by using the AUTHENTICATE command with a [SASL] mechanism
- that does not use plaintext passwords, by first negotiating
- encryption via STARTTLS or some other protection mechanism.
-
- A server implementation MUST implement a configuration that, at the
- time of authentication, requires:
- (1) The STARTTLS command has been negotiated.
- OR
- (2) Some other mechanism that protects the session from password
- snooping has been provided.
- OR
- (3) The following measures are in place:
- (a) The LOGINDISABLED capability is advertised, and [SASL]
- mechanisms (such as PLAIN) using plaintext passwords are NOT
- advertised in the CAPABILITY list.
- AND
- (b) The LOGIN command returns an error even if the password is
- correct.
- AND
- (c) The AUTHENTICATE command returns an error with all [SASL]
- mechanisms that use plaintext passwords, even if the password
- is correct.
-
- A server error message for a failing LOGIN command SHOULD NOT specify
- that the user name, as opposed to the password, is invalid.
-
- A server SHOULD have mechanisms in place to limit or delay failed
- AUTHENTICATE/LOGIN attempts.
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- Additional security considerations are discussed in the section
- discussing the AUTHENTICATE and LOGIN commands.
-
-12. IANA Considerations
-
- IMAP4 capabilities are registered by publishing a standards track or
- IESG approved experimental RFC. The registry is currently located
- at:
-
- http://www.iana.org/assignments/imap4-capabilities
-
- As this specification revises the STARTTLS and LOGINDISABLED
- extensions previously defined in [IMAP-TLS], the registry will be
- updated accordingly.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
-Appendices
-
-A. Normative References
-
- The following documents contain definitions or specifications that
- are necessary to understand this document properly:
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", RFC 2234,
- November 1997.
-
- [ANONYMOUS] Newman, C., "Anonymous SASL Mechanism", RFC
- 2245, November 1997.
-
- [CHARSET] Freed, N. and J. Postel, "IANA Character Set
- Registration Procedures", RFC 2978, October
- 2000.
-
- [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest
- Authentication as a SASL Mechanism", RFC 2831,
- May 2000.
-
- [DISPOSITION] Troost, R., Dorner, S. and K. Moore,
- "Communicating Presentation Information in
- Internet Messages: The Content-Disposition
- Header", RFC 2183, August 1997.
-
- [IMAP-TLS] Newman, C., "Using TLS with IMAP, POP3 and
- ACAP", RFC 2595, June 1999.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to
- Indicate Requirement Levels", BCP 14, RFC 2119,
- March 1997.
-
- [LANGUAGE-TAGS] Alvestrand, H., "Tags for the Identification of
- Languages", BCP 47, RFC 3066, January 2001.
-
- [LOCATION] Palme, J., Hopmann, A. and N. Shelness, "MIME
- Encapsulation of Aggregate Documents, such as
- HTML (MHTML)", RFC 2557, March 1999.
-
- [MD5] Myers, J. and M. Rose, "The Content-MD5 Header
- Field", RFC 1864, October 1995.
-
-
-
-
-
-
-
-
-
-Crispin Standards Track [Page 95]
-
-RFC 3501 IMAPv4 March 2003
-
-
- [MIME-HDRS] Moore, K., "MIME (Multipurpose Internet Mail
- Extensions) Part Three: Message Header
- Extensions for Non-ASCII Text", RFC 2047,
- November 1996.
-
- [MIME-IMB] Freed, N. and N. Borenstein, "MIME
- (Multipurpose Internet Mail Extensions) Part
- One: Format of Internet Message Bodies", RFC
- 2045, November 1996.
-
- [MIME-IMT] Freed, N. and N. Borenstein, "MIME
- (Multipurpose Internet Mail Extensions) Part
- Two: Media Types", RFC 2046, November 1996.
-
- [RFC-2822] Resnick, P., "Internet Message Format", RFC
- 2822, April 2001.
-
- [SASL] Myers, J., "Simple Authentication and Security
- Layer (SASL)", RFC 2222, October 1997.
-
- [TLS] Dierks, T. and C. Allen, "The TLS Protocol
- Version 1.0", RFC 2246, January 1999.
-
- [UTF-7] Goldsmith, D. and M. Davis, "UTF-7: A Mail-Safe
- Transformation Format of Unicode", RFC 2152,
- May 1997.
-
- The following documents describe quality-of-implementation issues
- that should be carefully considered when implementing this protocol:
-
- [IMAP-IMPLEMENTATION] Leiba, B., "IMAP Implementation
- Recommendations", RFC 2683, September 1999.
-
- [IMAP-MULTIACCESS] Gahrns, M., "IMAP4 Multi-Accessed Mailbox
- Practice", RFC 2180, July 1997.
-
-A.1 Informative References
-
- The following documents describe related protocols:
-
- [IMAP-DISC] Austein, R., "Synchronization Operations for
- Disconnected IMAP4 Clients", Work in Progress.
-
- [IMAP-MODEL] Crispin, M., "Distributed Electronic Mail
- Models in IMAP4", RFC 1733, December 1994.
-
-
-
-
-
-
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-
-RFC 3501 IMAPv4 March 2003
-
-
- [ACAP] Newman, C. and J. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244,
- November 1997.
-
- [SMTP] Klensin, J., "Simple Mail Transfer Protocol",
- STD 10, RFC 2821, April 2001.
-
- The following documents are historical or describe historical aspects
- of this protocol:
-
- [IMAP-COMPAT] Crispin, M., "IMAP4 Compatibility with
- IMAP2bis", RFC 2061, December 1996.
-
- [IMAP-HISTORICAL] Crispin, M., "IMAP4 Compatibility with IMAP2
- and IMAP2bis", RFC 1732, December 1994.
-
- [IMAP-OBSOLETE] Crispin, M., "Internet Message Access Protocol
- - Obsolete Syntax", RFC 2062, December 1996.
-
- [IMAP2] Crispin, M., "Interactive Mail Access Protocol
- - Version 2", RFC 1176, August 1990.
-
- [RFC-822] Crocker, D., "Standard for the Format of ARPA
- Internet Text Messages", STD 11, RFC 822,
- August 1982.
-
- [RFC-821] Postel, J., "Simple Mail Transfer Protocol",
- STD 10, RFC 821, August 1982.
-
-B. Changes from RFC 2060
-
- 1) Clarify description of unique identifiers and their semantics.
-
- 2) Fix the SELECT description to clarify that UIDVALIDITY is required
- in the SELECT and EXAMINE responses.
-
- 3) Added an example of a failing search.
-
- 4) Correct store-att-flags: "#flag" should be "1#flag".
-
- 5) Made search and section rules clearer.
-
- 6) Correct the STORE example.
-
- 7) Correct "BASE645" misspelling.
-
- 8) Remove extraneous close parenthesis in example of two-part message
- with text and BASE64 attachment.
-
-
-
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-
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-
-
- 9) Remove obsolete "MAILBOX" response from mailbox-data.
-
- 10) A spurious "<" in the rule for mailbox-data was removed.
-
- 11) Add CRLF to continue-req.
-
- 12) Specifically exclude "]" from the atom in resp-text-code.
-
- 13) Clarify that clients and servers should adhere strictly to the
- protocol syntax.
-
- 14) Emphasize in 5.2 that EXISTS can not be used to shrink a mailbox.
-
- 15) Add NEWNAME to resp-text-code.
-
- 16) Clarify that the empty string, not NIL, is used as arguments to
- LIST.
-
- 17) Clarify that NIL can be returned as a hierarchy delimiter for the
- empty string mailbox name argument if the mailbox namespace is flat.
-
- 18) Clarify that addr-mailbox and addr-name have RFC-2822 quoting
- removed.
-
- 19) Update UTF-7 reference.
-
- 20) Fix example in 6.3.11.
-
- 21) Clarify that non-existent UIDs are ignored.
-
- 22) Update DISPOSITION reference.
-
- 23) Expand state diagram.
-
- 24) Clarify that partial fetch responses are only returned in
- response to a partial fetch command.
-
- 25) Add UIDNEXT response code. Correct UIDVALIDITY definition
- reference.
-
- 26) Further clarification of "can" vs. "MAY".
-
- 27) Reference RFC-2119.
-
- 28) Clarify that superfluous shifts are not permitted in modified
- UTF-7.
-
- 29) Clarify that there are no implicit shifts in modified UTF-7.
-
-
-
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-
-
- 30) Clarify that "INBOX" in a mailbox name is always INBOX, even if
- it is given as a string.
-
- 31) Add missing open parenthesis in media-basic grammar rule.
-
- 32) Correct attribute syntax in mailbox-data.
-
- 33) Add UIDNEXT to EXAMINE responses.
-
- 34) Clarify UNSEEN, PERMANENTFLAGS, UIDVALIDITY, and UIDNEXT
- responses in SELECT and EXAMINE. They are required now, but weren't
- in older versions.
-
- 35) Update references with RFC numbers.
-
- 36) Flush text-mime2.
-
- 37) Clarify that modified UTF-7 names must be case-sensitive and that
- violating the convention should be avoided.
-
- 38) Correct UID FETCH example.
-
- 39) Clarify UID FETCH, UID STORE, and UID SEARCH vs. untagged EXPUNGE
- responses.
-
- 40) Clarify the use of the word "convention".
-
- 41) Clarify that a command is not "in progress" until it has been
- fully received (specifically, that a command is not "in progress"
- during command continuation negotiation).
-
- 42) Clarify envelope defaulting.
-
- 43) Clarify that SP means one and only one space character.
-
- 44) Forbid silly states in LIST response.
-
- 45) Clarify that the ENVELOPE, INTERNALDATE, RFC822*, BODY*, and UID
- for a message is static.
-
- 46) Add BADCHARSET response code.
-
- 47) Update formal syntax to [ABNF] conventions.
-
- 48) Clarify trailing hierarchy delimiter in CREATE semantics.
-
- 49) Clarify that the "blank line" is the [RFC-2822] delimiting blank
- line.
-
-
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-
-
- 50) Clarify that RENAME should also create hierarchy as needed for
- the command to complete.
-
- 51) Fix body-ext-mpart to not require language if disposition
- present.
-
- 52) Clarify the RFC822.HEADER response.
-
- 53) Correct missing space after charset astring in search.
-
- 54) Correct missing quote for BADCHARSET in resp-text-code.
-
- 55) Clarify that ALL, FAST, and FULL preclude any other data items
- appearing.
-
- 56) Clarify semantics of reference argument in LIST.
-
- 57) Clarify that a null string for SEARCH HEADER X-FOO means any
- message with a header line with a field-name of X-FOO regardless of
- the text of the header.
-
- 58) Specifically reserve 8-bit mailbox names for future use as UTF-8.
-
- 59) It is not an error for the client to store a flag that is not in
- the PERMANENTFLAGS list; however, the server will either ignore the
- change or make the change in the session only.
-
- 60) Correct/clarify the text regarding superfluous shifts.
-
- 61) Correct typographic errors in the "Changes" section.
-
- 62) Clarify that STATUS must not be used to check for new messages in
- the selected mailbox
-
- 63) Clarify LSUB behavior with "%" wildcard.
-
- 64) Change AUTHORIZATION to AUTHENTICATE in section 7.5.
-
- 65) Clarify description of multipart body type.
-
- 66) Clarify that STORE FLAGS does not affect \Recent.
-
- 67) Change "west" to "east" in description of timezone.
-
- 68) Clarify that commands which break command pipelining must wait
- for a completion result response.
-
- 69) Clarify that EXAMINE does not affect \Recent.
-
-
-
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-
-
- 70) Make description of MIME structure consistent.
-
- 71) Clarify that date searches disregard the time and timezone of the
- INTERNALDATE or Date: header. In other words, "ON 13-APR-2000" means
- messages with an INTERNALDATE text which starts with "13-APR-2000",
- even if timezone differential from the local timezone is sufficient
- to move that INTERNALDATE into the previous or next day.
-
- 72) Clarify that the header fetches don't add a blank line if one
- isn't in the [RFC-2822] message.
-
- 73) Clarify (in discussion of UIDs) that messages are immutable.
-
- 74) Add an example of CHARSET searching.
-
- 75) Clarify in SEARCH that keywords are a type of flag.
-
- 76) Clarify the mandatory nature of the SELECT data responses.
-
- 77) Add optional CAPABILITY response code in the initial OK or
- PREAUTH.
-
- 78) Add note that server can send an untagged CAPABILITY command as
- part of the responses to AUTHENTICATE and LOGIN.
-
- 79) Remove statement about it being unnecessary to issue a CAPABILITY
- command more than once in a connection. That statement is no longer
- true.
-
- 80) Clarify that untagged EXPUNGE decrements the number of messages
- in the mailbox.
-
- 81) Fix definition of "body" (concatenation has tighter binding than
- alternation).
-
- 82) Add a new "Special Notes to Implementors" section with reference
- to [IMAP-IMPLEMENTATION].
-
- 83) Clarify that an untagged CAPABILITY response to an AUTHENTICATE
- command should only be done if a security layer was not negotiated.
-
- 84) Change the definition of atom to exclude "]". Update astring to
- include "]" for compatibility with the past. Remove resp-text-atom.
-
- 85) Remove NEWNAME. It can't work because mailbox names can be
- literals and can include "]". Functionality can be addressed via
- referrals.
-
-
-
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-
-
- 86) Move modified UTF-7 rationale in order to have more logical
- paragraph flow.
-
- 87) Clarify UID uniqueness guarantees with the use of MUST.
-
- 88) Note that clients should read response data until the connection
- is closed instead of immediately closing on a BYE.
-
- 89) Change RFC-822 references to RFC-2822.
-
- 90) Clarify that RFC-2822 should be followed instead of RFC-822.
-
- 91) Change recommendation of optional automatic capabilities in LOGIN
- and AUTHENTICATE to use the CAPABILITY response code in the tagged
- OK. This is more interoperable than an unsolicited untagged
- CAPABILITY response.
-
- 92) STARTTLS and AUTH=PLAIN are mandatory to implement; add
- recommendations for other [SASL] mechanisms.
-
- 93) Clarify that a "connection" (as opposed to "server" or "command")
- is in one of the four states.
-
- 94) Clarify that a failed or rejected command does not change state.
-
- 95) Split references between normative and informative.
-
- 96) Discuss authentication failure issues in security section.
-
- 97) Clarify that a data item is not necessarily of only one data
- type.
-
- 98) Clarify that sequence ranges are independent of order.
-
- 99) Change an example to clarify that superfluous shifts in
- Modified-UTF7 can not be fixed just by omitting the shift. The
- entire string must be recalculated.
-
- 100) Change Envelope Structure definition since [RFC-2822] uses
- "envelope" to refer to the [SMTP] envelope and not the envelope data
- that appears in the [RFC-2822] header.
-
- 101) Expand on RFC822.HEADER response data vs. BODY[HEADER].
-
- 102) Clarify Logout state semantics, change ASCII art.
-
- 103) Security changes to comply with IESG requirements.
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- 104) Add definition for body URI.
-
- 105) Break sequence range definition into three rules, with rewritten
- descriptions for each.
-
- 106) Move STARTTLS and LOGINDISABLED here from [IMAP-TLS].
-
- 107) Add IANA Considerations section.
-
- 108) Clarify valid client assumptions for new message UIDs vs.
- UIDNEXT.
-
- 109) Clarify that changes to permanentflags affect concurrent
- sessions as well as subsequent sessions.
-
- 110) Clarify that authenticated state can be entered by the CLOSE
- command.
-
- 111) Emphasize that SELECT and EXAMINE are the exceptions to the rule
- that a failing command does not change state.
-
- 112) Clarify that newly-appended messages have the Recent flag set.
-
- 113) Clarify that newly-copied messages SHOULD have the Recent flag
- set.
-
- 114) Clarify that UID commands always return the UID in FETCH
- responses.
-
-C. Key Word Index
-
- +FLAGS <flag list> (store command data item) ............... 59
- +FLAGS.SILENT <flag list> (store command data item) ........ 59
- -FLAGS <flag list> (store command data item) ............... 59
- -FLAGS.SILENT <flag list> (store command data item) ........ 59
- ALERT (response code) ...................................... 64
- ALL (fetch item) ........................................... 55
- ALL (search key) ........................................... 50
- ANSWERED (search key) ...................................... 50
- APPEND (command) ........................................... 45
- AUTHENTICATE (command) ..................................... 27
- BAD (response) ............................................. 66
- BADCHARSET (response code) ................................. 64
- BCC <string> (search key) .................................. 51
- BEFORE <date> (search key) ................................. 51
- BODY (fetch item) .......................................... 55
- BODY (fetch result) ........................................ 73
- BODY <string> (search key) ................................. 51
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- BODY.PEEK[<section>]<<partial>> (fetch item) ............... 57
- BODYSTRUCTURE (fetch item) ................................. 57
- BODYSTRUCTURE (fetch result) ............................... 74
- BODY[<section>]<<origin octet>> (fetch result) ............. 74
- BODY[<section>]<<partial>> (fetch item) .................... 55
- BYE (response) ............................................. 67
- Body Structure (message attribute) ......................... 12
- CAPABILITY (command) ....................................... 24
- CAPABILITY (response code) ................................. 64
- CAPABILITY (response) ...................................... 68
- CC <string> (search key) ................................... 51
- CHECK (command) ............................................ 47
- CLOSE (command) ............................................ 48
- COPY (command) ............................................. 59
- CREATE (command) ........................................... 34
- DELETE (command) ........................................... 35
- DELETED (search key) ....................................... 51
- DRAFT (search key) ......................................... 51
- ENVELOPE (fetch item) ...................................... 57
- ENVELOPE (fetch result) .................................... 77
- EXAMINE (command) .......................................... 33
- EXISTS (response) .......................................... 71
- EXPUNGE (command) .......................................... 48
- EXPUNGE (response) ......................................... 72
- Envelope Structure (message attribute) ..................... 12
- FAST (fetch item) .......................................... 55
- FETCH (command) ............................................ 54
- FETCH (response) ........................................... 73
- FLAGGED (search key) ....................................... 51
- FLAGS (fetch item) ......................................... 57
- FLAGS (fetch result) ....................................... 78
- FLAGS (response) ........................................... 71
- FLAGS <flag list> (store command data item) ................ 59
- FLAGS.SILENT <flag list> (store command data item) ......... 59
- FROM <string> (search key) ................................. 51
- FULL (fetch item) .......................................... 55
- Flags (message attribute) .................................. 11
- HEADER (part specifier) .................................... 55
- HEADER <field-name> <string> (search key) .................. 51
- HEADER.FIELDS <header-list> (part specifier) ............... 55
- HEADER.FIELDS.NOT <header-list> (part specifier) ........... 55
- INTERNALDATE (fetch item) .................................. 57
- INTERNALDATE (fetch result) ................................ 78
- Internal Date (message attribute) .......................... 12
- KEYWORD <flag> (search key) ................................ 51
- Keyword (type of flag) ..................................... 11
- LARGER <n> (search key) .................................... 51
- LIST (command) ............................................. 40
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- LIST (response) ............................................ 69
- LOGIN (command) ............................................ 30
- LOGOUT (command) ........................................... 25
- LSUB (command) ............................................. 43
- LSUB (response) ............................................ 70
- MAY (specification requirement term) ....................... 4
- MESSAGES (status item) ..................................... 45
- MIME (part specifier) ...................................... 56
- MUST (specification requirement term) ...................... 4
- MUST NOT (specification requirement term) .................. 4
- Message Sequence Number (message attribute) ................ 10
- NEW (search key) ........................................... 51
- NO (response) .............................................. 66
- NOOP (command) ............................................. 25
- NOT <search-key> (search key) .............................. 52
- OK (response) .............................................. 65
- OLD (search key) ........................................... 52
- ON <date> (search key) ..................................... 52
- OPTIONAL (specification requirement term) .................. 4
- OR <search-key1> <search-key2> (search key) ................ 52
- PARSE (response code) ...................................... 64
- PERMANENTFLAGS (response code) ............................. 64
- PREAUTH (response) ......................................... 67
- Permanent Flag (class of flag) ............................. 12
- READ-ONLY (response code) .................................. 65
- READ-WRITE (response code) ................................. 65
- RECENT (response) .......................................... 72
- RECENT (search key) ........................................ 52
- RECENT (status item) ....................................... 45
- RENAME (command) ........................................... 37
- REQUIRED (specification requirement term) .................. 4
- RFC822 (fetch item) ........................................ 57
- RFC822 (fetch result) ...................................... 78
- RFC822.HEADER (fetch item) ................................. 57
- RFC822.HEADER (fetch result) ............................... 78
- RFC822.SIZE (fetch item) ................................... 57
- RFC822.SIZE (fetch result) ................................. 78
- RFC822.TEXT (fetch item) ................................... 58
- RFC822.TEXT (fetch result) ................................. 79
- SEARCH (command) ........................................... 49
- SEARCH (response) .......................................... 71
- SEEN (search key) .......................................... 52
- SELECT (command) ........................................... 31
- SENTBEFORE <date> (search key) ............................. 52
- SENTON <date> (search key) ................................. 52
- SENTSINCE <date> (search key) .............................. 52
- SHOULD (specification requirement term) .................... 4
- SHOULD NOT (specification requirement term) ................ 4
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- SINCE <date> (search key) .................................. 52
- SMALLER <n> (search key) ................................... 52
- STARTTLS (command) ......................................... 27
- STATUS (command) ........................................... 44
- STATUS (response) .......................................... 70
- STORE (command) ............................................ 58
- SUBJECT <string> (search key) .............................. 53
- SUBSCRIBE (command) ........................................ 38
- Session Flag (class of flag) ............................... 12
- System Flag (type of flag) ................................. 11
- TEXT (part specifier) ...................................... 56
- TEXT <string> (search key) ................................. 53
- TO <string> (search key) ................................... 53
- TRYCREATE (response code) .................................. 65
- UID (command) .............................................. 60
- UID (fetch item) ........................................... 58
- UID (fetch result) ......................................... 79
- UID <sequence set> (search key) ............................ 53
- UIDNEXT (response code) .................................... 65
- UIDNEXT (status item) ...................................... 45
- UIDVALIDITY (response code) ................................ 65
- UIDVALIDITY (status item) .................................. 45
- UNANSWERED (search key) .................................... 53
- UNDELETED (search key) ..................................... 53
- UNDRAFT (search key) ....................................... 53
- UNFLAGGED (search key) ..................................... 53
- UNKEYWORD <flag> (search key) .............................. 53
- UNSEEN (response code) ..................................... 65
- UNSEEN (search key) ........................................ 53
- UNSEEN (status item) ....................................... 45
- UNSUBSCRIBE (command) ...................................... 39
- Unique Identifier (UID) (message attribute) ................ 8
- X<atom> (command) .......................................... 62
- [RFC-2822] Size (message attribute) ........................ 12
- \Answered (system flag) .................................... 11
- \Deleted (system flag) ..................................... 11
- \Draft (system flag) ....................................... 11
- \Flagged (system flag) ..................................... 11
- \Marked (mailbox name attribute) ........................... 69
- \Noinferiors (mailbox name attribute) ...................... 69
- \Noselect (mailbox name attribute) ......................... 69
- \Recent (system flag) ...................................... 11
- \Seen (system flag) ........................................ 11
- \Unmarked (mailbox name attribute) ......................... 69
-
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-
-Author's Address
-
- Mark R. Crispin
- Networks and Distributed Computing
- University of Washington
- 4545 15th Avenue NE
- Seattle, WA 98105-4527
-
- Phone: (206) 543-5762
-
- EMail: MRC@CAC.Washington.EDU
-
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-RFC 3501 IMAPv4 March 2003
-
-
-Full Copyright Statement
-
- Copyright (C) The Internet Society (2003). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns. v This
- document and the information contained herein is provided on an "AS
- IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
- FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
- LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
- NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
- OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
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diff --git a/proto/rfc4616.txt b/proto/rfc4616.txt
@@ -1,619 +0,0 @@
-
-
-
-
-
-
-Network Working Group K. Zeilenga, Ed.
-Request for Comments: 4616 OpenLDAP Foundation
-Updates: 2595 August 2006
-Category: Standards Track
-
-
- The PLAIN Simple Authentication and Security Layer (SASL) Mechanism
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2006).
-
-Abstract
-
- This document defines a simple clear-text user/password Simple
- Authentication and Security Layer (SASL) mechanism called the PLAIN
- mechanism. The PLAIN mechanism is intended to be used, in
- combination with data confidentiality services provided by a lower
- layer, in protocols that lack a simple password authentication
- command.
-
-
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-Zeilenga Standards Track [Page 1]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
-1. Introduction
-
- Clear-text, multiple-use passwords are simple, interoperate with
- almost all existing operating system authentication databases, and
- are useful for a smooth transition to a more secure password-based
- authentication mechanism. The drawback is that they are unacceptable
- for use over network connections where data confidentiality is not
- ensured.
-
- This document defines the PLAIN Simple Authentication and Security
- Layer ([SASL]) mechanism for use in protocols with no clear-text
- login command (e.g., [ACAP] or [SMTP-AUTH]). This document updates
- RFC 2595, replacing Section 6. Changes since RFC 2595 are detailed
- in Appendix A.
-
- The name associated with this mechanism is "PLAIN".
-
- The PLAIN SASL mechanism does not provide a security layer.
-
- The PLAIN mechanism should not be used without adequate data security
- protection as this mechanism affords no integrity or confidentiality
- protections itself. The mechanism is intended to be used with data
- security protections provided by application-layer protocol,
- generally through its use of Transport Layer Security ([TLS])
- services.
-
- By default, implementations SHOULD advertise and make use of the
- PLAIN mechanism only when adequate data security services are in
- place. Specifications for IETF protocols that indicate that this
- mechanism is an applicable authentication mechanism MUST mandate that
- implementations support an strong data security service, such as TLS.
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in [Keywords].
-
-2. PLAIN SASL Mechanism
-
- The mechanism consists of a single message, a string of [UTF-8]
- encoded [Unicode] characters, from the client to the server. The
- client presents the authorization identity (identity to act as),
- followed by a NUL (U+0000) character, followed by the authentication
- identity (identity whose password will be used), followed by a NUL
- (U+0000) character, followed by the clear-text password. As with
- other SASL mechanisms, the client does not provide an authorization
- identity when it wishes the server to derive an identity from the
- credentials and use that as the authorization identity.
-
-
-
-
-Zeilenga Standards Track [Page 2]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
- The formal grammar for the client message using Augmented BNF [ABNF]
- follows.
-
- message = [authzid] UTF8NUL authcid UTF8NUL passwd
- authcid = 1*SAFE ; MUST accept up to 255 octets
- authzid = 1*SAFE ; MUST accept up to 255 octets
- passwd = 1*SAFE ; MUST accept up to 255 octets
- UTF8NUL = %x00 ; UTF-8 encoded NUL character
-
- SAFE = UTF1 / UTF2 / UTF3 / UTF4
- ;; any UTF-8 encoded Unicode character except NUL
-
- UTF1 = %x01-7F ;; except NUL
- UTF2 = %xC2-DF UTF0
- UTF3 = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
- %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
- UTF4 = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
- %xF4 %x80-8F 2(UTF0)
- UTF0 = %x80-BF
-
- The authorization identity (authzid), authentication identity
- (authcid), password (passwd), and NUL character deliminators SHALL be
- transferred as [UTF-8] encoded strings of [Unicode] characters. As
- the NUL (U+0000) character is used as a deliminator, the NUL (U+0000)
- character MUST NOT appear in authzid, authcid, or passwd productions.
-
- The form of the authzid production is specific to the application-
- level protocol's SASL profile [SASL]. The authcid and passwd
- productions are form-free. Use of non-visible characters or
- characters that a user may be unable to enter on some keyboards is
- discouraged.
-
- Servers MUST be capable of accepting authzid, authcid, and passwd
- productions up to and including 255 octets. It is noted that the
- UTF-8 encoding of a Unicode character may be as long as 4 octets.
-
- Upon receipt of the message, the server will verify the presented (in
- the message) authentication identity (authcid) and password (passwd)
- with the system authentication database, and it will verify that the
- authentication credentials permit the client to act as the (presented
- or derived) authorization identity (authzid). If both steps succeed,
- the user is authenticated.
-
- The presented authentication identity and password strings, as well
- as the database authentication identity and password strings, are to
- be prepared before being used in the verification process. The
- [SASLPrep] profile of the [StringPrep] algorithm is the RECOMMENDED
- preparation algorithm. The SASLprep preparation algorithm is
-
-
-
-Zeilenga Standards Track [Page 3]
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-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
- recommended to improve the likelihood that comparisons behave in an
- expected manner. The SASLprep preparation algorithm is not mandatory
- so as to allow the server to employ other preparation algorithms
- (including none) when appropriate. For instance, use of a different
- preparation algorithm may be necessary for the server to interoperate
- with an external system.
-
- When preparing the presented strings using [SASLPrep], the presented
- strings are to be treated as "query" strings (Section 7 of
- [StringPrep]) and hence unassigned code points are allowed to appear
- in their prepared output. When preparing the database strings using
- [SASLPrep], the database strings are to be treated as "stored"
- strings (Section 7 of [StringPrep]) and hence unassigned code points
- are prohibited from appearing in their prepared output.
-
- Regardless of the preparation algorithm used, if the output of a
- non-invertible function (e.g., hash) of the expected string is
- stored, the string MUST be prepared before input to that function.
-
- Regardless of the preparation algorithm used, if preparation fails or
- results in an empty string, verification SHALL fail.
-
- When no authorization identity is provided, the server derives an
- authorization identity from the prepared representation of the
- provided authentication identity string. This ensures that the
- derivation of different representations of the authentication
- identity produces the same authorization identity.
-
- The server MAY use the credentials to initialize any new
- authentication database, such as one suitable for [CRAM-MD5] or
- [DIGEST-MD5].
-
-3. Pseudo-Code
-
- This section provides pseudo-code illustrating the verification
- process (using hashed passwords and the SASLprep preparation
- function) discussed above. This section is not definitive.
-
- boolean Verify(string authzid, string authcid, string passwd) {
- string pAuthcid = SASLprep(authcid, true); # prepare authcid
- string pPasswd = SASLprep(passwd, true); # prepare passwd
- if (pAuthcid == NULL || pPasswd == NULL) {
- return false; # preparation failed
- }
- if (pAuthcid == "" || pPasswd == "") {
- return false; # empty prepared string
- }
-
-
-
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-Zeilenga Standards Track [Page 4]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
- storedHash = FetchPasswordHash(pAuthcid);
- if (storedHash == NULL || storedHash == "") {
- return false; # error or unknown authcid
- }
-
- if (!Compare(storedHash, Hash(pPasswd))) {
- return false; # incorrect password
- }
-
- if (authzid == NULL ) {
- authzid = DeriveAuthzid(pAuthcid);
- if (authzid == NULL || authzid == "") {
- return false; # could not derive authzid
- }
- }
-
- if (!Authorize(pAuthcid, authzid)) {
- return false; # not authorized
- }
-
- return true;
- }
-
- The second parameter of the SASLprep function, when true, indicates
- that unassigned code points are allowed in the input. When the
- SASLprep function is called to prepare the password prior to
- computing the stored hash, the second parameter would be false.
-
- The second parameter provided to the Authorize function is not
- prepared by this code. The application-level SASL profile should be
- consulted to determine what, if any, preparation is necessary.
-
- Note that the DeriveAuthzid and Authorize functions (whether
- implemented as one function or two, whether designed in a manner in
- which these functions or whether the mechanism implementation can be
- reused elsewhere) require knowledge and understanding of mechanism
- and the application-level protocol specification and/or
- implementation details to implement.
-
- Note that the Authorize function outcome is clearly dependent on
- details of the local authorization model and policy. Both functions
- may be dependent on other factors as well.
-
-
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-Zeilenga Standards Track [Page 5]
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-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
-4. Examples
-
- This section provides examples of PLAIN authentication exchanges.
- The examples are intended to help the readers understand the above
- text. The examples are not definitive.
-
- "C:" and "S:" indicate lines sent by the client and server,
- respectively. "<NUL>" represents a single NUL (U+0000) character.
- The Application Configuration Access Protocol ([ACAP]) is used in the
- examples.
-
- The first example shows how the PLAIN mechanism might be used for
- user authentication.
-
- S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
- C: a001 STARTTLS
- S: a001 OK "Begin TLS negotiation now"
- <TLS negotiation, further commands are under TLS layer>
- S: * ACAP (SASL "CRAM-MD5" "PLAIN")
- C: a002 AUTHENTICATE "PLAIN"
- S: + ""
- C: {21}
- C: <NUL>tim<NUL>tanstaaftanstaaf
- S: a002 OK "Authenticated"
-
- The second example shows how the PLAIN mechanism might be used to
- attempt to assume the identity of another user. In this example, the
- server rejects the request. Also, this example makes use of the
- protocol optional initial response capability to eliminate a round-
- trip.
-
- S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
- C: a001 STARTTLS
- S: a001 OK "Begin TLS negotiation now"
- <TLS negotiation, further commands are under TLS layer>
- S: * ACAP (SASL "CRAM-MD5" "PLAIN")
- C: a002 AUTHENTICATE "PLAIN" {20+}
- C: Ursel<NUL>Kurt<NUL>xipj3plmq
- S: a002 NO "Not authorized to requested authorization identity"
-
-5. Security Considerations
-
- As the PLAIN mechanism itself provided no integrity or
- confidentiality protections, it should not be used without adequate
- external data security protection, such as TLS services provided by
- many application-layer protocols. By default, implementations SHOULD
- NOT advertise and SHOULD NOT make use of the PLAIN mechanism unless
- adequate data security services are in place.
-
-
-
-Zeilenga Standards Track [Page 6]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
- When the PLAIN mechanism is used, the server gains the ability to
- impersonate the user to all services with the same password
- regardless of any encryption provided by TLS or other confidentiality
- protection mechanisms. Whereas many other authentication mechanisms
- have similar weaknesses, stronger SASL mechanisms address this issue.
- Clients are encouraged to have an operational mode where all
- mechanisms that are likely to reveal the user's password to the
- server are disabled.
-
- General [SASL] security considerations apply to this mechanism.
-
- Unicode, [UTF-8], and [StringPrep] security considerations also
- apply.
-
-6. IANA Considerations
-
- The SASL Mechanism registry [IANA-SASL] entry for the PLAIN mechanism
- has been updated by the IANA to reflect that this document now
- provides its technical specification.
-
- To: iana@iana.org
- Subject: Updated Registration of SASL mechanism PLAIN
-
- SASL mechanism name: PLAIN
- Security considerations: See RFC 4616.
- Published specification (optional, recommended): RFC 4616
- Person & email address to contact for further information:
- Kurt Zeilenga <kurt@openldap.org>
- IETF SASL WG <ietf-sasl@imc.org>
- Intended usage: COMMON
- Author/Change controller: IESG <iesg@ietf.org>
- Note: Updates existing entry for PLAIN
-
-7. Acknowledgements
-
- This document is a revision of RFC 2595 by Chris Newman. Portions of
- the grammar defined in Section 2 were borrowed from [UTF-8] by
- Francois Yergeau.
-
- This document is a product of the IETF Simple Authentication and
- Security Layer (SASL) Working Group.
-
-
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-Zeilenga Standards Track [Page 7]
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-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
-8. Normative References
-
- [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", RFC 4234, October 2005.
-
- [Keywords] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [SASL] Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
- Authentication and Security Layer (SASL)", RFC 4422,
- June 2006.
-
- [SASLPrep] Zeilenga, K., "SASLprep: Stringprep Profile for User
- Names and Passwords", RFC 4013, February 2005.
-
- [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
- Internationalized Strings ("stringprep")", RFC 3454,
- December 2002.
-
- [Unicode] The Unicode Consortium, "The Unicode Standard, Version
- 3.2.0" is defined by "The Unicode Standard, Version
- 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
- 61633-5), as amended by the "Unicode Standard Annex
- #27: Unicode 3.1"
- (http://www.unicode.org/reports/tr27/) and by the
- "Unicode Standard Annex #28: Unicode 3.2"
- (http://www.unicode.org/reports/tr28/).
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", STD 63, RFC 3629, November 2003.
-
- [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
- Security (TLS) Protocol Version 1.1", RFC 4346, April
- 2006.
-
-9. Informative References
-
- [ACAP] Newman, C. and J. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November
- 1997.
-
- [CRAM-MD5] Nerenberg, L., Ed., "The CRAM-MD5 SASL Mechanism", Work
- in Progress, June 2006.
-
- [DIGEST-MD5] Melnikov, A., Ed., "Using Digest Authentication as a
- SASL Mechanism", Work in Progress, June 2006.
-
-
-
-
-
-Zeilenga Standards Track [Page 8]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
- [IANA-SASL] IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
- MECHANISMS",
- <http://www.iana.org/assignments/sasl-mechanisms>.
-
- [SMTP-AUTH] Myers, J., "SMTP Service Extension for Authentication",
- RFC 2554, March 1999.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
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-Zeilenga Standards Track [Page 9]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
-Appendix A. Changes since RFC 2595
-
- This appendix is non-normative.
-
- This document replaces Section 6 of RFC 2595.
-
- The specification details how the server is to compare client-
- provided character strings with stored character strings.
-
- The ABNF grammar was updated. In particular, the grammar now allows
- LINE FEED (U+000A) and CARRIAGE RETURN (U+000D) characters in the
- authzid, authcid, passwd productions. However, whether these control
- characters may be used depends on the string preparation rules
- applicable to the production. For passwd and authcid productions,
- control characters are prohibited. For authzid, one must consult the
- application-level SASL profile. This change allows PLAIN to carry
- all possible authorization identity strings allowed in SASL.
-
- Pseudo-code was added.
-
- The example section was expanded to illustrate more features of the
- PLAIN mechanism.
-
-Editor's Address
-
- Kurt D. Zeilenga
- OpenLDAP Foundation
-
- EMail: Kurt@OpenLDAP.org
-
-
-
-
-
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-
-
-
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-Zeilenga Standards Track [Page 10]
-
-RFC 4616 The PLAIN SASL Mechanism August 2006
-
-
-Full Copyright Statement
-
- Copyright (C) The Internet Society (2006).
-
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-Acknowledgement
-
- Funding for the RFC Editor function is provided by the IETF
- Administrative Support Activity (IASA).
-
-
-
-
-
-
-
-Zeilenga Standards Track [Page 11]
-
diff --git a/proto/rfc5256.txt b/proto/rfc5256.txt
@@ -1,1067 +0,0 @@
-
-
-
-
-
-
-Network Working Group M. Crispin
-Request for Comments: 5256 Panda Programming
-Category: Standards Track K. Murchison
- Carnegie Mellon University
- June 2008
-
-
- Internet Message Access Protocol - SORT and THREAD Extensions
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- This document describes the base-level server-based sorting and
- threading extensions to the IMAP protocol. These extensions provide
- substantial performance improvements for IMAP clients that offer
- sorted and threaded views.
-
-1. Introduction
-
- The SORT and THREAD extensions to the [IMAP] protocol provide a means
- of server-based sorting and threading of messages, without requiring
- that the client download the necessary data to do so itself. This is
- particularly useful for online clients as described in [IMAP-MODELS].
-
- A server that supports the base-level SORT extension indicates this
- with a capability name which starts with "SORT". Future, upwards-
- compatible extensions to the SORT extension will all start with
- "SORT", indicating support for this base level.
-
- A server that supports the THREAD extension indicates this with one
- or more capability names consisting of "THREAD=" followed by a
- supported threading algorithm name as described in this document.
- This provides for future upwards-compatible extensions.
-
- A server that implements the SORT and/or THREAD extensions MUST
- collate strings in accordance with the requirements of I18NLEVEL=1,
- as described in [IMAP-I18N], and SHOULD implement and advertise the
- I18NLEVEL=1 extension. Alternatively, a server MAY implement
- I18NLEVEL=2 (or higher) and comply with the rules of that level.
-
-
-
-
-
-Crispin & Murchison Standards Track [Page 1]
-
-RFC 5256 IMAP Sort June 2008
-
-
- Discussion: The SORT and THREAD extensions predate [IMAP-I18N] by
- several years. At the time of this writing, all known server
- implementations of SORT and THREAD comply with the rules of
- I18NLEVEL=1, but do not necessarily advertise it. As discussed in
- [IMAP-I18N] section 4.5, all server implementations should
- eventually be updated to comply with the I18NLEVEL=2 extension.
-
- Historical note: The REFERENCES threading algorithm is based on the
- [THREADING] algorithm written and used in "Netscape Mail and News"
- versions 2.0 through 3.0.
-
-2. Terminology
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in [KEYWORDS].
-
- The word "can" (not "may") is used to refer to a possible
- circumstance or situation, as opposed to an optional facility of the
- protocol.
-
- "User" is used to refer to a human user, whereas "client" refers to
- the software being run by the user.
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server, respectively.
-
-2.1. Base Subject
-
- Subject sorting and threading use the "base subject", which has
- specific subject artifacts removed. Due to the complexity of these
- artifacts, the formal syntax for the subject extraction rules is
- ambiguous. The following procedure is followed to determine the
- "base subject", using the [ABNF] formal syntax rules described in
- section 5:
-
- (1) Convert any RFC 2047 encoded-words in the subject to [UTF-8]
- as described in "Internationalization Considerations".
- Convert all tabs and continuations to space. Convert all
- multiple spaces to a single space.
-
- (2) Remove all trailing text of the subject that matches the
- subj-trailer ABNF; repeat until no more matches are possible.
-
- (3) Remove all prefix text of the subject that matches the subj-
- leader ABNF.
-
-
-
-
-
-Crispin & Murchison Standards Track [Page 2]
-
-RFC 5256 IMAP Sort June 2008
-
-
- (4) If there is prefix text of the subject that matches the subj-
- blob ABNF, and removing that prefix leaves a non-empty subj-
- base, then remove the prefix text.
-
- (5) Repeat (3) and (4) until no matches remain.
-
- Note: It is possible to defer step (2) until step (6), but this
- requires checking for subj-trailer in step (4).
-
- (6) If the resulting text begins with the subj-fwd-hdr ABNF and
- ends with the subj-fwd-trl ABNF, remove the subj-fwd-hdr and
- subj-fwd-trl and repeat from step (2).
-
- (7) The resulting text is the "base subject" used in the SORT.
-
- All servers and disconnected (as described in [IMAP-MODELS]) clients
- MUST use exactly this algorithm to determine the "base subject".
- Otherwise, there is potential for a user to get inconsistent results
- based on whether they are running in connected or disconnected mode.
-
-2.2. Sent Date
-
- As used in this document, the term "sent date" refers to the date and
- time from the Date: header, adjusted by time zone to normalize to
- UTC. For example, "31 Dec 2000 16:01:33 -0800" is equivalent to the
- UTC date and time of "1 Jan 2001 00:01:33 +0000".
-
- If the time zone is invalid, the date and time SHOULD be treated as
- UTC. If the time is also invalid, the time SHOULD be treated as
- 00:00:00. If there is no valid date or time, the date and time
- SHOULD be treated as 00:00:00 on the earliest possible date.
-
- This differs from the date-related criteria in the SEARCH command
- (described in [IMAP] section 6.4.4), which use just the date and not
- the time, and are not adjusted by time zone.
-
- If the sent date cannot be determined (a Date: header is missing or
- cannot be parsed), the INTERNALDATE for that message is used as the
- sent date.
-
- When comparing two sent dates that match exactly, the order in which
- the two messages appear in the mailbox (that is, by sequence number)
- is used as a tie-breaker to determine the order.
-
-
-
-
-
-
-
-
-Crispin & Murchison Standards Track [Page 3]
-
-RFC 5256 IMAP Sort June 2008
-
-
-3. Additional Commands
-
- These commands are extensions to the [IMAP] base protocol.
-
- The section headings are intended to correspond with where they would
- be located in the main document if they were part of the base
- specification.
-
-BASE.6.4.SORT. SORT Command
-
- Arguments: sort program
- charset specification
- searching criteria (one or more)
-
- Data: untagged responses: SORT
-
- Result: OK - sort completed
- NO - sort error: can't sort that charset or
- criteria
- BAD - command unknown or arguments invalid
-
- The SORT command is a variant of SEARCH with sorting semantics for
- the results. There are two arguments before the searching
- criteria argument: a parenthesized list of sort criteria, and the
- searching charset.
-
- The charset argument is mandatory (unlike SEARCH) and indicates
- the [CHARSET] of the strings that appear in the searching
- criteria. The US-ASCII and [UTF-8] charsets MUST be implemented.
- All other charsets are optional.
-
- There is also a UID SORT command that returns unique identifiers
- instead of message sequence numbers. Note that there are separate
- searching criteria for message sequence numbers and UIDs; thus,
- the arguments to UID SORT are interpreted the same as in SORT.
- This is analogous to the behavior of UID SEARCH, as opposed to UID
- COPY, UID FETCH, or UID STORE.
-
- The SORT command first searches the mailbox for messages that
- match the given searching criteria using the charset argument for
- the interpretation of strings in the searching criteria. It then
- returns the matching messages in an untagged SORT response, sorted
- according to one or more sort criteria.
-
- Sorting is in ascending order. Earlier dates sort before later
- dates; smaller sizes sort before larger sizes; and strings are
- sorted according to ascending values established by their
- collation algorithm (see "Internationalization Considerations").
-
-
-
-Crispin & Murchison Standards Track [Page 4]
-
-RFC 5256 IMAP Sort June 2008
-
-
- If two or more messages exactly match according to the sorting
- criteria, these messages are sorted according to the order in
- which they appear in the mailbox. In other words, there is an
- implicit sort criterion of "sequence number".
-
- When multiple sort criteria are specified, the result is sorted in
- the priority order that the criteria appear. For example,
- (SUBJECT DATE) will sort messages in order by their base subject
- text; and for messages with the same base subject text, it will
- sort by their sent date.
-
- Untagged EXPUNGE responses are not permitted while the server is
- responding to a SORT command, but are permitted during a UID SORT
- command.
-
- The defined sort criteria are as follows. Refer to the Formal
- Syntax section for the precise syntactic definitions of the
- arguments. If the associated RFC-822 header for a particular
- criterion is absent, it is treated as the empty string. The empty
- string always collates before non-empty strings.
-
- ARRIVAL
- Internal date and time of the message. This differs from the
- ON criteria in SEARCH, which uses just the internal date.
-
- CC
- [IMAP] addr-mailbox of the first "cc" address.
-
- DATE
- Sent date and time, as described in section 2.2.
-
- FROM
- [IMAP] addr-mailbox of the first "From" address.
-
- REVERSE
- Followed by another sort criterion, has the effect of that
- criterion but in reverse (descending) order.
- Note: REVERSE only reverses a single criterion, and does not
- affect the implicit "sequence number" sort criterion if all
- other criteria are identical. Consequently, a sort of
- REVERSE SUBJECT is not the same as a reverse ordering of a
- SUBJECT sort. This can be avoided by use of additional
- criteria, e.g., SUBJECT DATE vs. REVERSE SUBJECT REVERSE
- DATE. In general, however, it's better (and faster, if the
- client has a "reverse current ordering" command) to reverse
- the results in the client instead of issuing a new SORT.
-
-
-
-
-
-Crispin & Murchison Standards Track [Page 5]
-
-RFC 5256 IMAP Sort June 2008
-
-
- SIZE
- Size of the message in octets.
-
- SUBJECT
- Base subject text.
-
- TO
- [IMAP] addr-mailbox of the first "To" address.
-
- Example: C: A282 SORT (SUBJECT) UTF-8 SINCE 1-Feb-1994
- S: * SORT 2 84 882
- S: A282 OK SORT completed
- C: A283 SORT (SUBJECT REVERSE DATE) UTF-8 ALL
- S: * SORT 5 3 4 1 2
- S: A283 OK SORT completed
- C: A284 SORT (SUBJECT) US-ASCII TEXT "not in mailbox"
- S: * SORT
- S: A284 OK SORT completed
-
-BASE.6.4.THREAD. THREAD Command
-
-Arguments: threading algorithm
- charset specification
- searching criteria (one or more)
-
-Data: untagged responses: THREAD
-
-Result: OK - thread completed
- NO - thread error: can't thread that charset or
- criteria
- BAD - command unknown or arguments invalid
-
- The THREAD command is a variant of SEARCH with threading semantics
- for the results. Thread has two arguments before the searching
- criteria argument: a threading algorithm and the searching
- charset.
-
- The charset argument is mandatory (unlike SEARCH) and indicates
- the [CHARSET] of the strings that appear in the searching
- criteria. The US-ASCII and [UTF-8] charsets MUST be implemented.
- All other charsets are optional.
-
- There is also a UID THREAD command that returns unique identifiers
- instead of message sequence numbers. Note that there are separate
- searching criteria for message sequence numbers and UIDs; thus the
- arguments to UID THREAD are interpreted the same as in THREAD.
- This is analogous to the behavior of UID SEARCH, as opposed to UID
- COPY, UID FETCH, or UID STORE.
-
-
-
-Crispin & Murchison Standards Track [Page 6]
-
-RFC 5256 IMAP Sort June 2008
-
-
- The THREAD command first searches the mailbox for messages that
- match the given searching criteria using the charset argument for
- the interpretation of strings in the searching criteria. It then
- returns the matching messages in an untagged THREAD response,
- threaded according to the specified threading algorithm.
-
- All collation is in ascending order. Earlier dates collate before
- later dates and strings are collated according to ascending values
- established by their collation algorithm (see
- "Internationalization Considerations").
-
- Untagged EXPUNGE responses are not permitted while the server is
- responding to a THREAD command, but are permitted during a UID
- THREAD command.
-
- The defined threading algorithms are as follows:
-
- ORDEREDSUBJECT
-
- The ORDEREDSUBJECT threading algorithm is also referred to as
- "poor man's threading". The searched messages are sorted by
- base subject and then by the sent date. The messages are then
- split into separate threads, with each thread containing
- messages with the same base subject text. Finally, the threads
- are sorted by the sent date of the first message in the thread.
-
- The top level or "root" in ORDEREDSUBJECT threading contains
- the first message of every thread. All messages in the root
- are siblings of each other. The second message of a thread is
- the child of the first message, and subsequent messages of the
- thread are siblings of the second message and hence children of
- the message at the root. Hence, there are no grandchildren in
- ORDEREDSUBJECT threading.
-
- Children in ORDEREDSUBJECT threading do not have descendents.
- Client implementations SHOULD treat descendents of a child in a
- server response as being siblings of that child.
-
- REFERENCES
-
- The REFERENCES threading algorithm threads the searched
- messages by grouping them together in parent/child
- relationships based on which messages are replies to others.
- The parent/child relationships are built using two methods:
- reconstructing a message's ancestry using the references
- contained within it; and checking the original (not base)
- subject of a message to see if it is a reply to (or forward of)
- another message.
-
-
-
-Crispin & Murchison Standards Track [Page 7]
-
-RFC 5256 IMAP Sort June 2008
-
-
- Note: "Message ID" in the following description refers to a
- normalized form of the msg-id in [RFC2822]. The actual text
- in RFC 2822 may use quoting, resulting in multiple ways of
- expressing the same Message ID. Implementations of the
- REFERENCES threading algorithm MUST normalize any msg-id in
- order to avoid false non-matches due to differences in
- quoting.
-
- For example, the msg-id
- <"01KF8JCEOCBS0045PS"@xxx.yyy.com>
- and the msg-id
- <01KF8JCEOCBS0045PS@xxx.yyy.com>
- MUST be interpreted as being the same Message ID.
-
- The references used for reconstructing a message's ancestry are
- found using the following rules:
-
- If a message contains a References header line, then use the
- Message IDs in the References header line as the references.
-
- If a message does not contain a References header line, or
- the References header line does not contain any valid
- Message IDs, then use the first (if any) valid Message ID
- found in the In-Reply-To header line as the only reference
- (parent) for this message.
-
- Note: Although [RFC2822] permits multiple Message IDs in
- the In-Reply-To header, in actual practice this
- discipline has not been followed. For example,
- In-Reply-To headers have been observed with message
- addresses after the Message ID, and there are no good
- heuristics for software to determine the difference.
- This is not a problem with the References header,
- however.
-
- If a message does not contain an In-Reply-To header line, or
- the In-Reply-To header line does not contain a valid Message
- ID, then the message does not have any references (NIL).
-
- A message is considered to be a reply or forward if the base
- subject extraction rules, applied to the original subject,
- remove any of the following: a subj-refwd, a "(fwd)" subj-
- trailer, or a subj-fwd-hdr and subj-fwd-trl.
-
- The REFERENCES algorithm is significantly more complex than
- ORDEREDSUBJECT and consists of six main steps. These steps are
- outlined in detail below.
-
-
-
-
-Crispin & Murchison Standards Track [Page 8]
-
-RFC 5256 IMAP Sort June 2008
-
-
- (1) For each searched message:
-
- (A) Using the Message IDs in the message's references, link
- the corresponding messages (those whose Message-ID
- header line contains the given reference Message ID)
- together as parent/child. Make the first reference the
- parent of the second (and the second a child of the
- first), the second the parent of the third (and the
- third a child of the second), etc. The following rules
- govern the creation of these links:
-
- If a message does not contain a Message-ID header
- line, or the Message-ID header line does not
- contain a valid Message ID, then assign a unique
- Message ID to this message.
-
- If two or more messages have the same Message ID,
- then only use that Message ID in the first (lowest
- sequence number) message, and assign a unique
- Message ID to each of the subsequent messages with
- a duplicate of that Message ID.
-
- If no message can be found with a given Message ID,
- create a dummy message with this ID. Use this
- dummy message for all subsequent references to this
- ID.
-
- If a message already has a parent, don't change the
- existing link. This is done because the References
- header line may have been truncated by a Mail User
- Agent (MUA). As a result, there is no guarantee
- that the messages corresponding to adjacent Message
- IDs in the References header line are parent and
- child.
-
- Do not create a parent/child link if creating that
- link would introduce a loop. For example, before
- making message A the parent of B, make sure that A
- is not a descendent of B.
-
- Note: Message ID comparisons are case-sensitive.
-
- (B) Create a parent/child link between the last reference
- (or NIL if there are no references) and the current
- message. If the current message already has a parent,
- it is probably the result of a truncated References
- header line, so break the current parent/child link
- before creating the new correct one. As in step 1.A,
-
-
-
-Crispin & Murchison Standards Track [Page 9]
-
-RFC 5256 IMAP Sort June 2008
-
-
- do not create the parent/child link if creating that
- link would introduce a loop. Note that if this message
- has no references, it will now have no parent.
-
- Note: The parent/child links created in steps 1.A
- and 1.B MUST be kept consistent with one another at
- ALL times.
-
- (2) Gather together all of the messages that have no parents
- and make them all children (siblings of one another) of a
- dummy parent (the "root"). These messages constitute the
- first (head) message of the threads created thus far.
-
- (3) Prune dummy messages from the thread tree. Traverse each
- thread under the root, and for each message:
-
- If it is a dummy message with NO children, delete it.
-
- If it is a dummy message with children, delete it, but
- promote its children to the current level. In other
- words, splice them in with the dummy's siblings.
-
- Do not promote the children if doing so would make them
- children of the root, unless there is only one child.
-
- (4) Sort the messages under the root (top-level siblings only)
- by sent date as described in section 2.2. In the case of a
- dummy message, sort its children by sent date and then use
- the first child for the top-level sort.
-
- (5) Gather together messages under the root that have the same
- base subject text.
-
- (A) Create a table for associating base subjects with
- messages, called the subject table.
-
- (B) Populate the subject table with one message per each
- base subject. For each child of the root:
-
- (i) Find the subject of this thread, by using the
- base subject from either the current message or
- its first child if the current message is a
- dummy. This is the thread subject.
-
- (ii) If the thread subject is empty, skip this
- message.
-
-
-
-
-
-Crispin & Murchison Standards Track [Page 10]
-
-RFC 5256 IMAP Sort June 2008
-
-
- (iii) Look up the message associated with the thread
- subject in the subject table.
-
- (iv) If there is no message in the subject table with
- the thread subject, add the current message and
- the thread subject to the subject table.
-
- Otherwise, if the message in the subject table is
- not a dummy, AND either of the following criteria
- are true:
-
- The current message is a dummy, OR
-
- The message in the subject table is a reply
- or forward and the current message is not.
-
- then replace the message in the subject table
- with the current message.
-
- (C) Merge threads with the same thread subject. For each
- child of the root:
-
- (i) Find the message's thread subject as in step
- 5.B.i above.
-
- (ii) If the thread subject is empty, skip this
- message.
-
- (iii) Lookup the message associated with this thread
- subject in the subject table.
-
- (iv) If the message in the subject table is the
- current message, skip this message.
-
- Otherwise, merge the current message with the one in
- the subject table using the following rules:
-
- If both messages are dummies, append the current
- message's children to the children of the message
- in the subject table (the children of both messages
- become siblings), and then delete the current
- message.
-
- If the message in the subject table is a dummy and
- the current message is not, make the current
- message a child of the message in the subject table
- (a sibling of its children).
-
-
-
-
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-
- If the current message is a reply or forward and
- the message in the subject table is not, make the
- current message a child of the message in the
- subject table (a sibling of its children).
-
- Otherwise, create a new dummy message and make both
- the current message and the message in the subject
- table children of the dummy. Then replace the
- message in the subject table with the dummy
- message.
-
- Note: Subject comparisons are case-insensitive,
- as described under "Internationalization
- Considerations".
-
- (6) Traverse the messages under the root and sort each set of
- siblings by sent date as described in section 2.2.
- Traverse the messages in such a way that the "youngest" set
- of siblings are sorted first, and the "oldest" set of
- siblings are sorted last (grandchildren are sorted before
- children, etc). In the case of a dummy message (which can
- only occur with top-level siblings), use its first child
- for sorting.
-
- Example: C: A283 THREAD ORDEREDSUBJECT UTF-8 SINCE 5-MAR-2000
- S: * THREAD (166)(167)(168)(169)(172)(170)(171)
- (173)(174 (175)(176)(178)(181)(180))(179)(177
- (183)(182)(188)(184)(185)(186)(187)(189))(190)
- (191)(192)(193)(194 195)(196 (197)(198))(199)
- (200 202)(201)(203)(204)(205)(206 207)(208)
- S: A283 OK THREAD completed
- C: A284 THREAD ORDEREDSUBJECT US-ASCII TEXT "gewp"
- S: * THREAD
- S: A284 OK THREAD completed
- C: A285 THREAD REFERENCES UTF-8 SINCE 5-MAR-2000
- S: * THREAD (166)(167)(168)(169)(172)((170)(179))
- (171)(173)((174)(175)(176)(178)(181)(180))
- ((177)(183)(182)(188 (184)(189))(185 186)(187))
- (190)(191)(192)(193)((194)(195 196))(197 198)
- (199)(200 202)(201)(203)(204)(205 206 207)(208)
- S: A285 OK THREAD completed
-
- Note: The line breaks in the first and third server
- responses are for editorial clarity and do not appear in
- real THREAD responses.
-
-
-
-
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-
-4. Additional Responses
-
- These responses are extensions to the [IMAP] base protocol.
-
- The section headings of these responses are intended to correspond
- with where they would be located in the main document.
-
-BASE.7.2.SORT. SORT Response
-
- Data: zero or more numbers
-
- The SORT response occurs as a result of a SORT or UID SORT
- command. The number(s) refer to those messages that match the
- search criteria. For SORT, these are message sequence numbers;
- for UID SORT, these are unique identifiers. Each number is
- delimited by a space.
-
- Example: S: * SORT 2 3 6
-
-BASE.7.2.THREAD. THREAD Response
-
- Data: zero or more threads
-
- The THREAD response occurs as a result of a THREAD or UID THREAD
- command. It contains zero or more threads. A thread consists of
- a parenthesized list of thread members.
-
- Thread members consist of zero or more message numbers, delimited
- by spaces, indicating successive parent and child. This continues
- until the thread splits into multiple sub-threads, at which point,
- the thread nests into multiple sub-threads with the first member
- of each sub-thread being siblings at this level. There is no
- limit to the nesting of threads.
-
- The messages numbers refer to those messages that match the search
- criteria. For THREAD, these are message sequence numbers; for UID
- THREAD, these are unique identifiers.
-
- Example: S: * THREAD (2)(3 6 (4 23)(44 7 96))
-
- The first thread consists only of message 2. The second thread
- consists of the messages 3 (parent) and 6 (child), after which it
- splits into two sub-threads; the first of which contains messages
- 4 (child of 6, sibling of 44) and 23 (child of 4), and the second
- of which contains messages 44 (child of 6, sibling of 4), 7 (child
- of 44), and 96 (child of 7). Since some later messages are
- parents of earlier messages, the messages were probably moved from
- some other mailbox at different times.
-
-
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-
- -- 2
-
- -- 3
- \-- 6
- |-- 4
- | \-- 23
- |
- \-- 44
- \-- 7
- \-- 96
-
- Example: S: * THREAD ((3)(5))
-
- In this example, 3 and 5 are siblings of a parent that does not
- match the search criteria (and/or does not exist in the mailbox);
- however they are members of the same thread.
-
-5. Formal Syntax of SORT and THREAD Commands and Responses
-
- The following syntax specification uses the Augmented Backus-Naur
- Form (ABNF) notation as specified in [ABNF]. It also uses [ABNF]
- rules defined in [IMAP].
-
-sort = ["UID" SP] "SORT" SP sort-criteria SP search-criteria
-
-sort-criteria = "(" sort-criterion *(SP sort-criterion) ")"
-
-sort-criterion = ["REVERSE" SP] sort-key
-
-sort-key = "ARRIVAL" / "CC" / "DATE" / "FROM" / "SIZE" /
- "SUBJECT" / "TO"
-
-thread = ["UID" SP] "THREAD" SP thread-alg SP search-criteria
-
-thread-alg = "ORDEREDSUBJECT" / "REFERENCES" / thread-alg-ext
-
-thread-alg-ext = atom
- ; New algorithms MUST be registered with IANA
-
-search-criteria = charset 1*(SP search-key)
-
-charset = atom / quoted
- ; CHARSET values MUST be registered with IANA
-
-sort-data = "SORT" *(SP nz-number)
-
-thread-data = "THREAD" [SP 1*thread-list]
-
-
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-
-thread-list = "(" (thread-members / thread-nested) ")"
-
-thread-members = nz-number *(SP nz-number) [SP thread-nested]
-
-thread-nested = 2*thread-list
-
- The following syntax describes base subject extraction rules (2)-(6):
-
-subject = *subj-leader [subj-middle] *subj-trailer
-
-subj-refwd = ("re" / ("fw" ["d"])) *WSP [subj-blob] ":"
-
-subj-blob = "[" *BLOBCHAR "]" *WSP
-
-subj-fwd = subj-fwd-hdr subject subj-fwd-trl
-
-subj-fwd-hdr = "[fwd:"
-
-subj-fwd-trl = "]"
-
-subj-leader = (*subj-blob subj-refwd) / WSP
-
-subj-middle = *subj-blob (subj-base / subj-fwd)
- ; last subj-blob is subj-base if subj-base would
- ; otherwise be empty
-
-subj-trailer = "(fwd)" / WSP
-
-subj-base = NONWSP *(*WSP NONWSP)
- ; can be a subj-blob
-
-BLOBCHAR = %x01-5a / %x5c / %x5e-ff
- ; any CHAR8 except '[' and ']'.
- ; SHOULD comply with [UTF-8]
-
-NONWSP = %x01-08 / %x0a-1f / %x21-ff
- ; any CHAR8 other than WSP.
- ; SHOULD comply with [UTF-8]
-
-6. Security Considerations
-
- The SORT and THREAD extensions do not raise any security
- considerations that are not present in the base [IMAP] protocol, and
- these issues are discussed in [IMAP]. Nevertheless, it is important
- to remember that [IMAP] protocol transactions, including message
- data, are sent in the clear over the network unless protection from
- snooping is negotiated, either by the use of STARTTLS, privacy
- protection in AUTHENTICATE, or some other protection mechanism.
-
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-
- Although not a security consideration, it is important to recognize
- that sorting by REFERENCES can lead to misleading threading trees.
- For example, a message with false References: header data will cause
- a thread to be incorporated into another thread.
-
- The process of extracting the base subject may lead to incorrect
- collation if the extracted data was significant text as opposed to a
- subject artifact.
-
-7. Internationalization Considerations
-
- As stated in the introduction, the rules of I18NLEVEL=1 as described
- in [IMAP-I18N] MUST be followed; that is, the SORT and THREAD
- extensions MUST collate strings according to the i;unicode-casemap
- collation described in [UNICASEMAP]. Servers SHOULD also advertise
- the I18NLEVEL=1 extension. Alternatively, a server MAY implement
- I18NLEVEL=2 (or higher) and comply with the rules of that level.
-
- As discussed in [IMAP-I18N] section 4.5, all server implementations
- should eventually be updated to support the [IMAP-I18N] I18NLEVEL=2
- extension.
-
- Translations of the "re" or "fw"/"fwd" tokens are not specified for
- removal in the base subject extraction process. An attempt to add
- such translated tokens would result in a geometrically complex, and
- ultimately unimplementable, task.
-
- Instead, note that [RFC2822] section 3.6.5 recommends that "re:"
- (from the Latin "res", meaning "in the matter of") be used to
- identify a reply. Although it is evident that, from the multiple
- forms of token to identify a forwarded message, there is considerable
- variation found in the wild, the variations are (still) manageable.
- Consequently, it is suggested that "re:" and one of the variations of
- the tokens for a forward supported by the base subject extraction
- rules be adopted for Internet mail messages, since doing so makes it
- a simple display-time task to localize the token language for the
- user.
-
-8. IANA Considerations
-
- [IMAP] capabilities are registered by publishing a standards track or
- IESG-approved experimental RFC. This document constitutes
- registration of the SORT and THREAD capabilities in the [IMAP]
- capabilities registry.
-
-
-
-
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-
- This document creates a new [IMAP] threading algorithms registry,
- which registers threading algorithms by publishing a standards track
- or IESG-approved experimental RFC. This document constitutes
- registration of the ORDEREDSUBJECT and REFERENCES algorithms in that
- registry.
-
-9. Normative References
-
- [ABNF] Crocker, D., Ed., and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", STD 68, RFC 5234, January
- 2008.
-
- [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration
- Procedures", BCP 19, RFC 2978, October 2000.
-
- [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
- VERSION 4rev1", RFC 3501, March 2003.
-
- [IMAP-I18N] Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet
- Message Access Protocol Internationalization", RFC
- 5255, June 2008.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC2822] Resnick, P., Ed., "Internet Message Format", RFC 2822,
- April 2001.
-
- [UNICASEMAP] Crispin, M., "i;unicode-casemap - Simple Unicode
- Collation Algorithm", RFC 5051, October 2007.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", STD 63, RFC 3629, November 2003.
-
-10. Informative References
-
- [IMAP-MODELS] Crispin, M., "Distributed Electronic Mail Models in
- IMAP4", RFC 1733, December 1994.
-
- [THREADING] Zawinski, J. "Message Threading",
- http://www.jwz.org/doc/threading.html, 1997-2002.
-
-
-
-
-
-
-
-
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-
-
-Authors' Addresses
-
- Mark R. Crispin
- Panda Programming
- 6158 NE Lariat Loop
- Bainbridge Island, WA 98110-2098
-
- Phone: +1 (206) 842-2385
- EMail: IMAP+SORT+THREAD@Lingling.Panda.COM
-
-
- Kenneth Murchison
- Carnegie Mellon University
- 5000 Forbes Avenue
- Cyert Hall 285
- Pittsburgh, PA 15213
-
- Phone: +1 (412) 268-2638
- EMail: murch@andrew.cmu.edu
-
-
-
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-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008).
-
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
- THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
- OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
- THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-
-
-
-
-
-
-
-
-
-
-
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diff --git a/proto/rfc5322.txt b/proto/rfc5322.txt
@@ -1,3195 +0,0 @@
-
-
-
-
-
-
-Network Working Group P. Resnick, Ed.
-Request for Comments: 5322 Qualcomm Incorporated
-Obsoletes: 2822 October 2008
-Updates: 4021
-Category: Standards Track
-
-
- Internet Message Format
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- This document specifies the Internet Message Format (IMF), a syntax
- for text messages that are sent between computer users, within the
- framework of "electronic mail" messages. This specification is a
- revision of Request For Comments (RFC) 2822, which itself superseded
- Request For Comments (RFC) 822, "Standard for the Format of ARPA
- Internet Text Messages", updating it to reflect current practice and
- incorporating incremental changes that were specified in other RFCs.
-
-
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-Resnick Standards Track [Page 1]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
- 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
- 1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 5
- 1.2.1. Requirements Notation . . . . . . . . . . . . . . . . 5
- 1.2.2. Syntactic Notation . . . . . . . . . . . . . . . . . . 5
- 1.2.3. Structure of This Document . . . . . . . . . . . . . . 5
- 2. Lexical Analysis of Messages . . . . . . . . . . . . . . . . . 6
- 2.1. General Description . . . . . . . . . . . . . . . . . . . 6
- 2.1.1. Line Length Limits . . . . . . . . . . . . . . . . . . 7
- 2.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 8
- 2.2.1. Unstructured Header Field Bodies . . . . . . . . . . . 8
- 2.2.2. Structured Header Field Bodies . . . . . . . . . . . . 8
- 2.2.3. Long Header Fields . . . . . . . . . . . . . . . . . . 8
- 2.3. Body . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
- 3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
- 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
- 3.2. Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
- 3.2.1. Quoted characters . . . . . . . . . . . . . . . . . . 10
- 3.2.2. Folding White Space and Comments . . . . . . . . . . . 11
- 3.2.3. Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
- 3.2.4. Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
- 3.2.5. Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
- 3.3. Date and Time Specification . . . . . . . . . . . . . . . 14
- 3.4. Address Specification . . . . . . . . . . . . . . . . . . 16
- 3.4.1. Addr-Spec Specification . . . . . . . . . . . . . . . 17
- 3.5. Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
- 3.6. Field Definitions . . . . . . . . . . . . . . . . . . . . 19
- 3.6.1. The Origination Date Field . . . . . . . . . . . . . . 22
- 3.6.2. Originator Fields . . . . . . . . . . . . . . . . . . 22
- 3.6.3. Destination Address Fields . . . . . . . . . . . . . . 23
- 3.6.4. Identification Fields . . . . . . . . . . . . . . . . 25
- 3.6.5. Informational Fields . . . . . . . . . . . . . . . . . 27
- 3.6.6. Resent Fields . . . . . . . . . . . . . . . . . . . . 28
- 3.6.7. Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
- 3.6.8. Optional Fields . . . . . . . . . . . . . . . . . . . 30
- 4. Obsolete Syntax . . . . . . . . . . . . . . . . . . . . . . . 31
- 4.1. Miscellaneous Obsolete Tokens . . . . . . . . . . . . . . 32
- 4.2. Obsolete Folding White Space . . . . . . . . . . . . . . . 33
- 4.3. Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
- 4.4. Obsolete Addressing . . . . . . . . . . . . . . . . . . . 35
- 4.5. Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
- 4.5.1. Obsolete Origination Date Field . . . . . . . . . . . 36
- 4.5.2. Obsolete Originator Fields . . . . . . . . . . . . . . 36
- 4.5.3. Obsolete Destination Address Fields . . . . . . . . . 37
- 4.5.4. Obsolete Identification Fields . . . . . . . . . . . . 37
- 4.5.5. Obsolete Informational Fields . . . . . . . . . . . . 37
-
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-Resnick Standards Track [Page 2]
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-RFC 5322 Internet Message Format October 2008
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-
- 4.5.6. Obsolete Resent Fields . . . . . . . . . . . . . . . . 38
- 4.5.7. Obsolete Trace Fields . . . . . . . . . . . . . . . . 38
- 4.5.8. Obsolete optional fields . . . . . . . . . . . . . . . 38
- 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
- 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
- Appendix A. Example Messages . . . . . . . . . . . . . . . . . 43
- Appendix A.1. Addressing Examples . . . . . . . . . . . . . . . 44
- Appendix A.1.1. A Message from One Person to Another with
- Simple Addressing . . . . . . . . . . . . . . . . 44
- Appendix A.1.2. Different Types of Mailboxes . . . . . . . . . . . 45
- Appendix A.1.3. Group Addresses . . . . . . . . . . . . . . . . . 45
- Appendix A.2. Reply Messages . . . . . . . . . . . . . . . . . . 46
- Appendix A.3. Resent Messages . . . . . . . . . . . . . . . . . 47
- Appendix A.4. Messages with Trace Fields . . . . . . . . . . . . 48
- Appendix A.5. White Space, Comments, and Other Oddities . . . . 49
- Appendix A.6. Obsoleted Forms . . . . . . . . . . . . . . . . . 50
- Appendix A.6.1. Obsolete Addressing . . . . . . . . . . . . . . . 50
- Appendix A.6.2. Obsolete Dates . . . . . . . . . . . . . . . . . . 50
- Appendix A.6.3. Obsolete White Space and Comments . . . . . . . . 51
- Appendix B. Differences from Earlier Specifications . . . . . 52
- Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . 53
- 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
- 7.1. Normative References . . . . . . . . . . . . . . . . . . . 55
- 7.2. Informative References . . . . . . . . . . . . . . . . . . 55
-
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-Resnick Standards Track [Page 3]
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-RFC 5322 Internet Message Format October 2008
-
-
-1. Introduction
-
-1.1. Scope
-
- This document specifies the Internet Message Format (IMF), a syntax
- for text messages that are sent between computer users, within the
- framework of "electronic mail" messages. This specification is an
- update to [RFC2822], which itself superseded [RFC0822], updating it
- to reflect current practice and incorporating incremental changes
- that were specified in other RFCs such as [RFC1123].
-
- This document specifies a syntax only for text messages. In
- particular, it makes no provision for the transmission of images,
- audio, or other sorts of structured data in electronic mail messages.
- There are several extensions published, such as the MIME document
- series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
- for the transmission of such data through electronic mail, either by
- extending the syntax provided here or by structuring such messages to
- conform to this syntax. Those mechanisms are outside of the scope of
- this specification.
-
- In the context of electronic mail, messages are viewed as having an
- envelope and contents. The envelope contains whatever information is
- needed to accomplish transmission and delivery. (See [RFC5321] for a
- discussion of the envelope.) The contents comprise the object to be
- delivered to the recipient. This specification applies only to the
- format and some of the semantics of message contents. It contains no
- specification of the information in the envelope.
-
- However, some message systems may use information from the contents
- to create the envelope. It is intended that this specification
- facilitate the acquisition of such information by programs.
-
- This specification is intended as a definition of what message
- content format is to be passed between systems. Though some message
- systems locally store messages in this format (which eliminates the
- need for translation between formats) and others use formats that
- differ from the one specified in this specification, local storage is
- outside of the scope of this specification.
-
- Note: This specification is not intended to dictate the internal
- formats used by sites, the specific message system features that
- they are expected to support, or any of the characteristics of
- user interface programs that create or read messages. In
- addition, this document does not specify an encoding of the
- characters for either transport or storage; that is, it does not
- specify the number of bits used or how those bits are specifically
- transferred over the wire or stored on disk.
-
-
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-Resnick Standards Track [Page 4]
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-RFC 5322 Internet Message Format October 2008
-
-
-1.2. Notational Conventions
-
-1.2.1. Requirements Notation
-
- This document occasionally uses terms that appear in capital letters.
- When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
- NOT", and "MAY" appear capitalized, they are being used to indicate
- particular requirements of this specification. A discussion of the
- meanings of these terms appears in [RFC2119].
-
-1.2.2. Syntactic Notation
-
- This specification uses the Augmented Backus-Naur Form (ABNF)
- [RFC5234] notation for the formal definitions of the syntax of
- messages. Characters will be specified either by a decimal value
- (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
- a case-insensitive literal value enclosed in quotation marks (e.g.,
- "A" for either uppercase or lowercase A).
-
-1.2.3. Structure of This Document
-
- This document is divided into several sections.
-
- This section, section 1, is a short introduction to the document.
-
- Section 2 lays out the general description of a message and its
- constituent parts. This is an overview to help the reader understand
- some of the general principles used in the later portions of this
- document. Any examples in this section MUST NOT be taken as
- specification of the formal syntax of any part of a message.
-
- Section 3 specifies formal ABNF rules for the structure of each part
- of a message (the syntax) and describes the relationship between
- those parts and their meaning in the context of a message (the
- semantics). That is, it lays out the actual rules for the structure
- of each part of a message (the syntax) as well as a description of
- the parts and instructions for their interpretation (the semantics).
- This includes analysis of the syntax and semantics of subparts of
- messages that have specific structure. The syntax included in
- section 3 represents messages as they MUST be created. There are
- also notes in section 3 to indicate if any of the options specified
- in the syntax SHOULD be used over any of the others.
-
- Both sections 2 and 3 describe messages that are legal to generate
- for purposes of this specification.
-
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-
- Section 4 of this document specifies an "obsolete" syntax. There are
- references in section 3 to these obsolete syntactic elements. The
- rules of the obsolete syntax are elements that have appeared in
- earlier versions of this specification or have previously been widely
- used in Internet messages. As such, these elements MUST be
- interpreted by parsers of messages in order to be conformant to this
- specification. However, since items in this syntax have been
- determined to be non-interoperable or to cause significant problems
- for recipients of messages, they MUST NOT be generated by creators of
- conformant messages.
-
- Section 5 details security considerations to take into account when
- implementing this specification.
-
- Appendix A lists examples of different sorts of messages. These
- examples are not exhaustive of the types of messages that appear on
- the Internet, but give a broad overview of certain syntactic forms.
-
- Appendix B lists the differences between this specification and
- earlier specifications for Internet messages.
-
- Appendix C contains acknowledgements.
-
-2. Lexical Analysis of Messages
-
-2.1. General Description
-
- At the most basic level, a message is a series of characters. A
- message that is conformant with this specification is composed of
- characters with values in the range of 1 through 127 and interpreted
- as US-ASCII [ANSI.X3-4.1986] characters. For brevity, this document
- sometimes refers to this range of characters as simply "US-ASCII
- characters".
-
- Note: This document specifies that messages are made up of
- characters in the US-ASCII range of 1 through 127. There are
- other documents, specifically the MIME document series ([RFC2045],
- [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]), that
- extend this specification to allow for values outside of that
- range. Discussion of those mechanisms is not within the scope of
- this specification.
-
- Messages are divided into lines of characters. A line is a series of
- characters that is delimited with the two characters carriage-return
- and line-feed; that is, the carriage return (CR) character (ASCII
- value 13) followed immediately by the line feed (LF) character (ASCII
- value 10). (The carriage return/line feed pair is usually written in
- this document as "CRLF".)
-
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-
- A message consists of header fields (collectively called "the header
- section of the message") followed, optionally, by a body. The header
- section is a sequence of lines of characters with special syntax as
- defined in this specification. The body is simply a sequence of
- characters that follows the header section and is separated from the
- header section by an empty line (i.e., a line with nothing preceding
- the CRLF).
-
- Note: Common parlance and earlier versions of this specification
- use the term "header" to either refer to the entire header section
- or to refer to an individual header field. To avoid ambiguity,
- this document does not use the terms "header" or "headers" in
- isolation, but instead always uses "header field" to refer to the
- individual field and "header section" to refer to the entire
- collection.
-
-2.1.1. Line Length Limits
-
- There are two limits that this specification places on the number of
- characters in a line. Each line of characters MUST be no more than
- 998 characters, and SHOULD be no more than 78 characters, excluding
- the CRLF.
-
- The 998 character limit is due to limitations in many implementations
- that send, receive, or store IMF messages which simply cannot handle
- more than 998 characters on a line. Receiving implementations would
- do well to handle an arbitrarily large number of characters in a line
- for robustness sake. However, there are so many implementations that
- (in compliance with the transport requirements of [RFC5321]) do not
- accept messages containing more than 1000 characters including the CR
- and LF per line, it is important for implementations not to create
- such messages.
-
- The more conservative 78 character recommendation is to accommodate
- the many implementations of user interfaces that display these
- messages which may truncate, or disastrously wrap, the display of
- more than 78 characters per line, in spite of the fact that such
- implementations are non-conformant to the intent of this
- specification (and that of [RFC5321] if they actually cause
- information to be lost). Again, even though this limitation is put
- on messages, it is incumbent upon implementations that display
- messages to handle an arbitrarily large number of characters in a
- line (certainly at least up to the 998 character limit) for the sake
- of robustness.
-
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-
-2.2. Header Fields
-
- Header fields are lines beginning with a field name, followed by a
- colon (":"), followed by a field body, and terminated by CRLF. A
- field name MUST be composed of printable US-ASCII characters (i.e.,
- characters that have values between 33 and 126, inclusive), except
- colon. A field body may be composed of printable US-ASCII characters
- as well as the space (SP, ASCII value 32) and horizontal tab (HTAB,
- ASCII value 9) characters (together known as the white space
- characters, WSP). A field body MUST NOT include CR and LF except
- when used in "folding" and "unfolding", as described in section
- 2.2.3. All field bodies MUST conform to the syntax described in
- sections 3 and 4 of this specification.
-
-2.2.1. Unstructured Header Field Bodies
-
- Some field bodies in this specification are defined simply as
- "unstructured" (which is specified in section 3.2.5 as any printable
- US-ASCII characters plus white space characters) with no further
- restrictions. These are referred to as unstructured field bodies.
- Semantically, unstructured field bodies are simply to be treated as a
- single line of characters with no further processing (except for
- "folding" and "unfolding" as described in section 2.2.3).
-
-2.2.2. Structured Header Field Bodies
-
- Some field bodies in this specification have a syntax that is more
- restrictive than the unstructured field bodies described above.
- These are referred to as "structured" field bodies. Structured field
- bodies are sequences of specific lexical tokens as described in
- sections 3 and 4 of this specification. Many of these tokens are
- allowed (according to their syntax) to be introduced or end with
- comments (as described in section 3.2.2) as well as the white space
- characters, and those white space characters are subject to "folding"
- and "unfolding" as described in section 2.2.3. Semantic analysis of
- structured field bodies is given along with their syntax.
-
-2.2.3. Long Header Fields
-
- Each header field is logically a single line of characters comprising
- the field name, the colon, and the field body. For convenience
- however, and to deal with the 998/78 character limitations per line,
- the field body portion of a header field can be split into a
- multiple-line representation; this is called "folding". The general
- rule is that wherever this specification allows for folding white
- space (not simply WSP characters), a CRLF may be inserted before any
- WSP.
-
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-
- For example, the header field:
-
- Subject: This is a test
-
- can be represented as:
-
- Subject: This
- is a test
-
- Note: Though structured field bodies are defined in such a way
- that folding can take place between many of the lexical tokens
- (and even within some of the lexical tokens), folding SHOULD be
- limited to placing the CRLF at higher-level syntactic breaks. For
- instance, if a field body is defined as comma-separated values, it
- is recommended that folding occur after the comma separating the
- structured items in preference to other places where the field
- could be folded, even if it is allowed elsewhere.
-
- The process of moving from this folded multiple-line representation
- of a header field to its single line representation is called
- "unfolding". Unfolding is accomplished by simply removing any CRLF
- that is immediately followed by WSP. Each header field should be
- treated in its unfolded form for further syntactic and semantic
- evaluation. An unfolded header field has no length restriction and
- therefore may be indeterminately long.
-
-2.3. Body
-
- The body of a message is simply lines of US-ASCII characters. The
- only two limitations on the body are as follows:
-
- o CR and LF MUST only occur together as CRLF; they MUST NOT appear
- independently in the body.
- o Lines of characters in the body MUST be limited to 998 characters,
- and SHOULD be limited to 78 characters, excluding the CRLF.
-
- Note: As was stated earlier, there are other documents,
- specifically the MIME documents ([RFC2045], [RFC2046], [RFC2049],
- [RFC4288], [RFC4289]), that extend (and limit) this specification
- to allow for different sorts of message bodies. Again, these
- mechanisms are beyond the scope of this document.
-
-
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-
-3. Syntax
-
-3.1. Introduction
-
- The syntax as given in this section defines the legal syntax of
- Internet messages. Messages that are conformant to this
- specification MUST conform to the syntax in this section. If there
- are options in this section where one option SHOULD be generated,
- that is indicated either in the prose or in a comment next to the
- syntax.
-
- For the defined expressions, a short description of the syntax and
- use is given, followed by the syntax in ABNF, followed by a semantic
- analysis. The following primitive tokens that are used but otherwise
- unspecified are taken from the "Core Rules" of [RFC5234], Appendix
- B.1: CR, LF, CRLF, HTAB, SP, WSP, DQUOTE, DIGIT, ALPHA, and VCHAR.
-
- In some of the definitions, there will be non-terminals whose names
- start with "obs-". These "obs-" elements refer to tokens defined in
- the obsolete syntax in section 4. In all cases, these productions
- are to be ignored for the purposes of generating legal Internet
- messages and MUST NOT be used as part of such a message. However,
- when interpreting messages, these tokens MUST be honored as part of
- the legal syntax. In this sense, section 3 defines a grammar for the
- generation of messages, with "obs-" elements that are to be ignored,
- while section 4 adds grammar for the interpretation of messages.
-
-3.2. Lexical Tokens
-
- The following rules are used to define an underlying lexical
- analyzer, which feeds tokens to the higher-level parsers. This
- section defines the tokens used in structured header field bodies.
-
- Note: Readers of this specification need to pay special attention
- to how these lexical tokens are used in both the lower-level and
- higher-level syntax later in the document. Particularly, the
- white space tokens and the comment tokens defined in section 3.2.2
- get used in the lower-level tokens defined here, and those lower-
- level tokens are in turn used as parts of the higher-level tokens
- defined later. Therefore, white space and comments may be allowed
- in the higher-level tokens even though they may not explicitly
- appear in a particular definition.
-
-3.2.1. Quoted characters
-
- Some characters are reserved for special interpretation, such as
- delimiting lexical tokens. To permit use of these characters as
- uninterpreted data, a quoting mechanism is provided.
-
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-
- quoted-pair = ("\" (VCHAR / WSP)) / obs-qp
-
- Where any quoted-pair appears, it is to be interpreted as the
- character alone. That is to say, the "\" character that appears as
- part of a quoted-pair is semantically "invisible".
-
- Note: The "\" character may appear in a message where it is not
- part of a quoted-pair. A "\" character that does not appear in a
- quoted-pair is not semantically invisible. The only places in
- this specification where quoted-pair currently appears are
- ccontent, qcontent, and in obs-dtext in section 4.
-
-3.2.2. Folding White Space and Comments
-
- White space characters, including white space used in folding
- (described in section 2.2.3), may appear between many elements in
- header field bodies. Also, strings of characters that are treated as
- comments may be included in structured field bodies as characters
- enclosed in parentheses. The following defines the folding white
- space (FWS) and comment constructs.
-
- Strings of characters enclosed in parentheses are considered comments
- so long as they do not appear within a "quoted-string", as defined in
- section 3.2.4. Comments may nest.
-
- There are several places in this specification where comments and FWS
- may be freely inserted. To accommodate that syntax, an additional
- token for "CFWS" is defined for places where comments and/or FWS can
- occur. However, where CFWS occurs in this specification, it MUST NOT
- be inserted in such a way that any line of a folded header field is
- made up entirely of WSP characters and nothing else.
-
- FWS = ([*WSP CRLF] 1*WSP) / obs-FWS
- ; Folding white space
-
- ctext = %d33-39 / ; Printable US-ASCII
- %d42-91 / ; characters not including
- %d93-126 / ; "(", ")", or "\"
- obs-ctext
-
- ccontent = ctext / quoted-pair / comment
-
- comment = "(" *([FWS] ccontent) [FWS] ")"
-
- CFWS = (1*([FWS] comment) [FWS]) / FWS
-
-
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-
-
- Throughout this specification, where FWS (the folding white space
- token) appears, it indicates a place where folding, as discussed in
- section 2.2.3, may take place. Wherever folding appears in a message
- (that is, a header field body containing a CRLF followed by any WSP),
- unfolding (removal of the CRLF) is performed before any further
- semantic analysis is performed on that header field according to this
- specification. That is to say, any CRLF that appears in FWS is
- semantically "invisible".
-
- A comment is normally used in a structured field body to provide some
- human-readable informational text. Since a comment is allowed to
- contain FWS, folding is permitted within the comment. Also note that
- since quoted-pair is allowed in a comment, the parentheses and
- backslash characters may appear in a comment, so long as they appear
- as a quoted-pair. Semantically, the enclosing parentheses are not
- part of the comment; the comment is what is contained between the two
- parentheses. As stated earlier, the "\" in any quoted-pair and the
- CRLF in any FWS that appears within the comment are semantically
- "invisible" and therefore not part of the comment either.
-
- Runs of FWS, comment, or CFWS that occur between lexical tokens in a
- structured header field are semantically interpreted as a single
- space character.
-
-3.2.3. Atom
-
- Several productions in structured header field bodies are simply
- strings of certain basic characters. Such productions are called
- atoms.
-
- Some of the structured header field bodies also allow the period
- character (".", ASCII value 46) within runs of atext. An additional
- "dot-atom" token is defined for those purposes.
-
- Note: The "specials" token does not appear anywhere else in this
- specification. It is simply the visible (i.e., non-control, non-
- white space) characters that do not appear in atext. It is
- provided only because it is useful for implementers who use tools
- that lexically analyze messages. Each of the characters in
- specials can be used to indicate a tokenization point in lexical
- analysis.
-
-
-
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-
- atext = ALPHA / DIGIT / ; Printable US-ASCII
- "!" / "#" / ; characters not including
- "$" / "%" / ; specials. Used for atoms.
- "&" / "'" /
- "*" / "+" /
- "-" / "/" /
- "=" / "?" /
- "^" / "_" /
- "`" / "{" /
- "|" / "}" /
- "~"
-
- atom = [CFWS] 1*atext [CFWS]
-
- dot-atom-text = 1*atext *("." 1*atext)
-
- dot-atom = [CFWS] dot-atom-text [CFWS]
-
- specials = "(" / ")" / ; Special characters that do
- "<" / ">" / ; not appear in atext
- "[" / "]" /
- ":" / ";" /
- "@" / "\" /
- "," / "." /
- DQUOTE
-
- Both atom and dot-atom are interpreted as a single unit, comprising
- the string of characters that make it up. Semantically, the optional
- comments and FWS surrounding the rest of the characters are not part
- of the atom; the atom is only the run of atext characters in an atom,
- or the atext and "." characters in a dot-atom.
-
-3.2.4. Quoted Strings
-
- Strings of characters that include characters other than those
- allowed in atoms can be represented in a quoted string format, where
- the characters are surrounded by quote (DQUOTE, ASCII value 34)
- characters.
-
-
-
-
-
-
-
-
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-
- qtext = %d33 / ; Printable US-ASCII
- %d35-91 / ; characters not including
- %d93-126 / ; "\" or the quote character
- obs-qtext
-
- qcontent = qtext / quoted-pair
-
- quoted-string = [CFWS]
- DQUOTE *([FWS] qcontent) [FWS] DQUOTE
- [CFWS]
-
- A quoted-string is treated as a unit. That is, quoted-string is
- identical to atom, semantically. Since a quoted-string is allowed to
- contain FWS, folding is permitted. Also note that since quoted-pair
- is allowed in a quoted-string, the quote and backslash characters may
- appear in a quoted-string so long as they appear as a quoted-pair.
-
- Semantically, neither the optional CFWS outside of the quote
- characters nor the quote characters themselves are part of the
- quoted-string; the quoted-string is what is contained between the two
- quote characters. As stated earlier, the "\" in any quoted-pair and
- the CRLF in any FWS/CFWS that appears within the quoted-string are
- semantically "invisible" and therefore not part of the quoted-string
- either.
-
-3.2.5. Miscellaneous Tokens
-
- Three additional tokens are defined: word and phrase for combinations
- of atoms and/or quoted-strings, and unstructured for use in
- unstructured header fields and in some places within structured
- header fields.
-
- word = atom / quoted-string
-
- phrase = 1*word / obs-phrase
-
- unstructured = (*([FWS] VCHAR) *WSP) / obs-unstruct
-
-3.3. Date and Time Specification
-
- Date and time values occur in several header fields. This section
- specifies the syntax for a full date and time specification. Though
- folding white space is permitted throughout the date-time
- specification, it is RECOMMENDED that a single space be used in each
- place that FWS appears (whether it is required or optional); some
- older implementations will not interpret longer sequences of folding
- white space correctly.
-
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-
- date-time = [ day-of-week "," ] date time [CFWS]
-
- day-of-week = ([FWS] day-name) / obs-day-of-week
-
- day-name = "Mon" / "Tue" / "Wed" / "Thu" /
- "Fri" / "Sat" / "Sun"
-
- date = day month year
-
- day = ([FWS] 1*2DIGIT FWS) / obs-day
-
- month = "Jan" / "Feb" / "Mar" / "Apr" /
- "May" / "Jun" / "Jul" / "Aug" /
- "Sep" / "Oct" / "Nov" / "Dec"
-
- year = (FWS 4*DIGIT FWS) / obs-year
-
- time = time-of-day zone
-
- time-of-day = hour ":" minute [ ":" second ]
-
- hour = 2DIGIT / obs-hour
-
- minute = 2DIGIT / obs-minute
-
- second = 2DIGIT / obs-second
-
- zone = (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
-
- The day is the numeric day of the month. The year is any numeric
- year 1900 or later.
-
- The time-of-day specifies the number of hours, minutes, and
- optionally seconds since midnight of the date indicated.
-
- The date and time-of-day SHOULD express local time.
-
- The zone specifies the offset from Coordinated Universal Time (UTC,
- formerly referred to as "Greenwich Mean Time") that the date and
- time-of-day represent. The "+" or "-" indicates whether the time-of-
- day is ahead of (i.e., east of) or behind (i.e., west of) Universal
- Time. The first two digits indicate the number of hours difference
- from Universal Time, and the last two digits indicate the number of
- additional minutes difference from Universal Time. (Hence, +hhmm
- means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
- minutes). The form "+0000" SHOULD be used to indicate a time zone at
- Universal Time. Though "-0000" also indicates Universal Time, it is
-
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-
- used to indicate that the time was generated on a system that may be
- in a local time zone other than Universal Time and that the date-time
- contains no information about the local time zone.
-
- A date-time specification MUST be semantically valid. That is, the
- day-of-week (if included) MUST be the day implied by the date, the
- numeric day-of-month MUST be between 1 and the number of days allowed
- for the specified month (in the specified year), the time-of-day MUST
- be in the range 00:00:00 through 23:59:60 (the number of seconds
- allowing for a leap second; see [RFC1305]), and the last two digits
- of the zone MUST be within the range 00 through 59.
-
-3.4. Address Specification
-
- Addresses occur in several message header fields to indicate senders
- and recipients of messages. An address may either be an individual
- mailbox, or a group of mailboxes.
-
- address = mailbox / group
-
- mailbox = name-addr / addr-spec
-
- name-addr = [display-name] angle-addr
-
- angle-addr = [CFWS] "<" addr-spec ">" [CFWS] /
- obs-angle-addr
-
- group = display-name ":" [group-list] ";" [CFWS]
-
- display-name = phrase
-
- mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
-
- address-list = (address *("," address)) / obs-addr-list
-
- group-list = mailbox-list / CFWS / obs-group-list
-
- A mailbox receives mail. It is a conceptual entity that does not
- necessarily pertain to file storage. For example, some sites may
- choose to print mail on a printer and deliver the output to the
- addressee's desk.
-
- Normally, a mailbox is composed of two parts: (1) an optional display
- name that indicates the name of the recipient (which can be a person
- or a system) that could be displayed to the user of a mail
- application, and (2) an addr-spec address enclosed in angle brackets
-
-
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-
- ("<" and ">"). There is an alternate simple form of a mailbox where
- the addr-spec address appears alone, without the recipient's name or
- the angle brackets. The Internet addr-spec address is described in
- section 3.4.1.
-
- Note: Some legacy implementations used the simple form where the
- addr-spec appears without the angle brackets, but included the
- name of the recipient in parentheses as a comment following the
- addr-spec. Since the meaning of the information in a comment is
- unspecified, implementations SHOULD use the full name-addr form of
- the mailbox, instead of the legacy form, to specify the display
- name associated with a mailbox. Also, because some legacy
- implementations interpret the comment, comments generally SHOULD
- NOT be used in address fields to avoid confusing such
- implementations.
-
- When it is desirable to treat several mailboxes as a single unit
- (i.e., in a distribution list), the group construct can be used. The
- group construct allows the sender to indicate a named group of
- recipients. This is done by giving a display name for the group,
- followed by a colon, followed by a comma-separated list of any number
- of mailboxes (including zero and one), and ending with a semicolon.
- Because the list of mailboxes can be empty, using the group construct
- is also a simple way to communicate to recipients that the message
- was sent to one or more named sets of recipients, without actually
- providing the individual mailbox address for any of those recipients.
-
-3.4.1. Addr-Spec Specification
-
- An addr-spec is a specific Internet identifier that contains a
- locally interpreted string followed by the at-sign character ("@",
- ASCII value 64) followed by an Internet domain. The locally
- interpreted string is either a quoted-string or a dot-atom. If the
- string can be represented as a dot-atom (that is, it contains no
- characters other than atext characters or "." surrounded by atext
- characters), then the dot-atom form SHOULD be used and the quoted-
- string form SHOULD NOT be used. Comments and folding white space
- SHOULD NOT be used around the "@" in the addr-spec.
-
- Note: A liberal syntax for the domain portion of addr-spec is
- given here. However, the domain portion contains addressing
- information specified by and used in other protocols (e.g.,
- [RFC1034], [RFC1035], [RFC1123], [RFC5321]). It is therefore
- incumbent upon implementations to conform to the syntax of
- addresses for the context in which they are used.
-
-
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-
- addr-spec = local-part "@" domain
-
- local-part = dot-atom / quoted-string / obs-local-part
-
- domain = dot-atom / domain-literal / obs-domain
-
- domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
-
- dtext = %d33-90 / ; Printable US-ASCII
- %d94-126 / ; characters not including
- obs-dtext ; "[", "]", or "\"
-
- The domain portion identifies the point to which the mail is
- delivered. In the dot-atom form, this is interpreted as an Internet
- domain name (either a host name or a mail exchanger name) as
- described in [RFC1034], [RFC1035], and [RFC1123]. In the domain-
- literal form, the domain is interpreted as the literal Internet
- address of the particular host. In both cases, how addressing is
- used and how messages are transported to a particular host is covered
- in separate documents, such as [RFC5321]. These mechanisms are
- outside of the scope of this document.
-
- The local-part portion is a domain-dependent string. In addresses,
- it is simply interpreted on the particular host as a name of a
- particular mailbox.
-
-3.5. Overall Message Syntax
-
- A message consists of header fields, optionally followed by a message
- body. Lines in a message MUST be a maximum of 998 characters
- excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
- characters excluding the CRLF. (See section 2.1.1 for explanation.)
- In a message body, though all of the characters listed in the text
- rule MAY be used, the use of US-ASCII control characters (values 1
- through 8, 11, 12, and 14 through 31) is discouraged since their
- interpretation by receivers for display is not guaranteed.
-
- message = (fields / obs-fields)
- [CRLF body]
-
- body = (*(*998text CRLF) *998text) / obs-body
-
- text = %d1-9 / ; Characters excluding CR
- %d11 / ; and LF
- %d12 /
- %d14-127
-
-
-
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-
-
- The header fields carry most of the semantic information and are
- defined in section 3.6. The body is simply a series of lines of text
- that are uninterpreted for the purposes of this specification.
-
-3.6. Field Definitions
-
- The header fields of a message are defined here. All header fields
- have the same general syntactic structure: a field name, followed by
- a colon, followed by the field body. The specific syntax for each
- header field is defined in the subsequent sections.
-
- Note: In the ABNF syntax for each field in subsequent sections,
- each field name is followed by the required colon. However, for
- brevity, sometimes the colon is not referred to in the textual
- description of the syntax. It is, nonetheless, required.
-
- It is important to note that the header fields are not guaranteed to
- be in a particular order. They may appear in any order, and they
- have been known to be reordered occasionally when transported over
- the Internet. However, for the purposes of this specification,
- header fields SHOULD NOT be reordered when a message is transported
- or transformed. More importantly, the trace header fields and resent
- header fields MUST NOT be reordered, and SHOULD be kept in blocks
- prepended to the message. See sections 3.6.6 and 3.6.7 for more
- information.
-
- The only required header fields are the origination date field and
- the originator address field(s). All other header fields are
- syntactically optional. More information is contained in the table
- following this definition.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- fields = *(trace
- *optional-field /
- *(resent-date /
- resent-from /
- resent-sender /
- resent-to /
- resent-cc /
- resent-bcc /
- resent-msg-id))
- *(orig-date /
- from /
- sender /
- reply-to /
- to /
- cc /
- bcc /
- message-id /
- in-reply-to /
- references /
- subject /
- comments /
- keywords /
- optional-field)
-
- The following table indicates limits on the number of times each
- field may occur in the header section of a message as well as any
- special limitations on the use of those fields. An asterisk ("*")
- next to a value in the minimum or maximum column indicates that a
- special restriction appears in the Notes column.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-
- +----------------+--------+------------+----------------------------+
- | Field | Min | Max number | Notes |
- | | number | | |
- +----------------+--------+------------+----------------------------+
- | trace | 0 | unlimited | Block prepended - see |
- | | | | 3.6.7 |
- | resent-date | 0* | unlimited* | One per block, required if |
- | | | | other resent fields are |
- | | | | present - see 3.6.6 |
- | resent-from | 0 | unlimited* | One per block - see 3.6.6 |
- | resent-sender | 0* | unlimited* | One per block, MUST occur |
- | | | | with multi-address |
- | | | | resent-from - see 3.6.6 |
- | resent-to | 0 | unlimited* | One per block - see 3.6.6 |
- | resent-cc | 0 | unlimited* | One per block - see 3.6.6 |
- | resent-bcc | 0 | unlimited* | One per block - see 3.6.6 |
- | resent-msg-id | 0 | unlimited* | One per block - see 3.6.6 |
- | orig-date | 1 | 1 | |
- | from | 1 | 1 | See sender and 3.6.2 |
- | sender | 0* | 1 | MUST occur with |
- | | | | multi-address from - see |
- | | | | 3.6.2 |
- | reply-to | 0 | 1 | |
- | to | 0 | 1 | |
- | cc | 0 | 1 | |
- | bcc | 0 | 1 | |
- | message-id | 0* | 1 | SHOULD be present - see |
- | | | | 3.6.4 |
- | in-reply-to | 0* | 1 | SHOULD occur in some |
- | | | | replies - see 3.6.4 |
- | references | 0* | 1 | SHOULD occur in some |
- | | | | replies - see 3.6.4 |
- | subject | 0 | 1 | |
- | comments | 0 | unlimited | |
- | keywords | 0 | unlimited | |
- | optional-field | 0 | unlimited | |
- +----------------+--------+------------+----------------------------+
-
- The exact interpretation of each field is described in subsequent
- sections.
-
-
-
-
-
-
-
-
-
-
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-
-
-3.6.1. The Origination Date Field
-
- The origination date field consists of the field name "Date" followed
- by a date-time specification.
-
- orig-date = "Date:" date-time CRLF
-
- The origination date specifies the date and time at which the creator
- of the message indicated that the message was complete and ready to
- enter the mail delivery system. For instance, this might be the time
- that a user pushes the "send" or "submit" button in an application
- program. In any case, it is specifically not intended to convey the
- time that the message is actually transported, but rather the time at
- which the human or other creator of the message has put the message
- into its final form, ready for transport. (For example, a portable
- computer user who is not connected to a network might queue a message
- for delivery. The origination date is intended to contain the date
- and time that the user queued the message, not the time when the user
- connected to the network to send the message.)
-
-3.6.2. Originator Fields
-
- The originator fields of a message consist of the from field, the
- sender field (when applicable), and optionally the reply-to field.
- The from field consists of the field name "From" and a comma-
- separated list of one or more mailbox specifications. If the from
- field contains more than one mailbox specification in the mailbox-
- list, then the sender field, containing the field name "Sender" and a
- single mailbox specification, MUST appear in the message. In either
- case, an optional reply-to field MAY also be included, which contains
- the field name "Reply-To" and a comma-separated list of one or more
- addresses.
-
- from = "From:" mailbox-list CRLF
-
- sender = "Sender:" mailbox CRLF
-
- reply-to = "Reply-To:" address-list CRLF
-
- The originator fields indicate the mailbox(es) of the source of the
- message. The "From:" field specifies the author(s) of the message,
- that is, the mailbox(es) of the person(s) or system(s) responsible
- for the writing of the message. The "Sender:" field specifies the
- mailbox of the agent responsible for the actual transmission of the
- message. For example, if a secretary were to send a message for
- another person, the mailbox of the secretary would appear in the
- "Sender:" field and the mailbox of the actual author would appear in
- the "From:" field. If the originator of the message can be indicated
-
-
-
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-
-
- by a single mailbox and the author and transmitter are identical, the
- "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
- appear.
-
- Note: The transmitter information is always present. The absence
- of the "Sender:" field is sometimes mistakenly taken to mean that
- the agent responsible for transmission of the message has not been
- specified. This absence merely means that the transmitter is
- identical to the author and is therefore not redundantly placed
- into the "Sender:" field.
-
- The originator fields also provide the information required when
- replying to a message. When the "Reply-To:" field is present, it
- indicates the address(es) to which the author of the message suggests
- that replies be sent. In the absence of the "Reply-To:" field,
- replies SHOULD by default be sent to the mailbox(es) specified in the
- "From:" field unless otherwise specified by the person composing the
- reply.
-
- In all cases, the "From:" field SHOULD NOT contain any mailbox that
- does not belong to the author(s) of the message. See also section
- 3.6.3 for more information on forming the destination addresses for a
- reply.
-
-3.6.3. Destination Address Fields
-
- The destination fields of a message consist of three possible fields,
- each of the same form: the field name, which is either "To", "Cc", or
- "Bcc", followed by a comma-separated list of one or more addresses
- (either mailbox or group syntax).
-
- to = "To:" address-list CRLF
-
- cc = "Cc:" address-list CRLF
-
- bcc = "Bcc:" [address-list / CFWS] CRLF
-
- The destination fields specify the recipients of the message. Each
- destination field may have one or more addresses, and the addresses
- indicate the intended recipients of the message. The only difference
- between the three fields is how each is used.
-
- The "To:" field contains the address(es) of the primary recipient(s)
- of the message.
-
-
-
-
-
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-
-
- The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
- making a copy on a typewriter using carbon paper) contains the
- addresses of others who are to receive the message, though the
- content of the message may not be directed at them.
-
- The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
- addresses of recipients of the message whose addresses are not to be
- revealed to other recipients of the message. There are three ways in
- which the "Bcc:" field is used. In the first case, when a message
- containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
- removed even though all of the recipients (including those specified
- in the "Bcc:" field) are sent a copy of the message. In the second
- case, recipients specified in the "To:" and "Cc:" lines each are sent
- a copy of the message with the "Bcc:" line removed as above, but the
- recipients on the "Bcc:" line get a separate copy of the message
- containing a "Bcc:" line. (When there are multiple recipient
- addresses in the "Bcc:" field, some implementations actually send a
- separate copy of the message to each recipient with a "Bcc:"
- containing only the address of that particular recipient.) Finally,
- since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
- sent without any addresses indicating to the recipients that blind
- copies were sent to someone. Which method to use with "Bcc:" fields
- is implementation dependent, but refer to the "Security
- Considerations" section of this document for a discussion of each.
-
- When a message is a reply to another message, the mailboxes of the
- authors of the original message (the mailboxes in the "From:" field)
- or mailboxes specified in the "Reply-To:" field (if it exists) MAY
- appear in the "To:" field of the reply since these would normally be
- the primary recipients of the reply. If a reply is sent to a message
- that has destination fields, it is often desirable to send a copy of
- the reply to all of the recipients of the message, in addition to the
- author. When such a reply is formed, addresses in the "To:" and
- "Cc:" fields of the original message MAY appear in the "Cc:" field of
- the reply, since these are normally secondary recipients of the
- reply. If a "Bcc:" field is present in the original message,
- addresses in that field MAY appear in the "Bcc:" field of the reply,
- but they SHOULD NOT appear in the "To:" or "Cc:" fields.
-
- Note: Some mail applications have automatic reply commands that
- include the destination addresses of the original message in the
- destination addresses of the reply. How those reply commands
- behave is implementation dependent and is beyond the scope of this
- document. In particular, whether or not to include the original
- destination addresses when the original message had a "Reply-To:"
- field is not addressed here.
-
-
-
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-
-
-3.6.4. Identification Fields
-
- Though listed as optional in the table in section 3.6, every message
- SHOULD have a "Message-ID:" field. Furthermore, reply messages
- SHOULD have "In-Reply-To:" and "References:" fields as appropriate
- and as described below.
-
- The "Message-ID:" field contains a single unique message identifier.
- The "References:" and "In-Reply-To:" fields each contain one or more
- unique message identifiers, optionally separated by CFWS.
-
- The message identifier (msg-id) syntax is a limited version of the
- addr-spec construct enclosed in the angle bracket characters, "<" and
- ">". Unlike addr-spec, this syntax only permits the dot-atom-text
- form on the left-hand side of the "@" and does not have internal CFWS
- anywhere in the message identifier.
-
- Note: As with addr-spec, a liberal syntax is given for the right-
- hand side of the "@" in a msg-id. However, later in this section,
- the use of a domain for the right-hand side of the "@" is
- RECOMMENDED. Again, the syntax of domain constructs is specified
- by and used in other protocols (e.g., [RFC1034], [RFC1035],
- [RFC1123], [RFC5321]). It is therefore incumbent upon
- implementations to conform to the syntax of addresses for the
- context in which they are used.
-
- message-id = "Message-ID:" msg-id CRLF
-
- in-reply-to = "In-Reply-To:" 1*msg-id CRLF
-
- references = "References:" 1*msg-id CRLF
-
- msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
-
- id-left = dot-atom-text / obs-id-left
-
- id-right = dot-atom-text / no-fold-literal / obs-id-right
-
- no-fold-literal = "[" *dtext "]"
-
- The "Message-ID:" field provides a unique message identifier that
- refers to a particular version of a particular message. The
- uniqueness of the message identifier is guaranteed by the host that
- generates it (see below). This message identifier is intended to be
- machine readable and not necessarily meaningful to humans. A message
- identifier pertains to exactly one version of a particular message;
- subsequent revisions to the message each receive new message
- identifiers.
-
-
-
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-RFC 5322 Internet Message Format October 2008
-
-
- Note: There are many instances when messages are "changed", but
- those changes do not constitute a new instantiation of that
- message, and therefore the message would not get a new message
- identifier. For example, when messages are introduced into the
- transport system, they are often prepended with additional header
- fields such as trace fields (described in section 3.6.7) and
- resent fields (described in section 3.6.6). The addition of such
- header fields does not change the identity of the message and
- therefore the original "Message-ID:" field is retained. In all
- cases, it is the meaning that the sender of the message wishes to
- convey (i.e., whether this is the same message or a different
- message) that determines whether or not the "Message-ID:" field
- changes, not any particular syntactic difference that appears (or
- does not appear) in the message.
-
- The "In-Reply-To:" and "References:" fields are used when creating a
- reply to a message. They hold the message identifier of the original
- message and the message identifiers of other messages (for example,
- in the case of a reply to a message that was itself a reply). The
- "In-Reply-To:" field may be used to identify the message (or
- messages) to which the new message is a reply, while the
- "References:" field may be used to identify a "thread" of
- conversation.
-
- When creating a reply to a message, the "In-Reply-To:" and
- "References:" fields of the resultant message are constructed as
- follows:
-
- The "In-Reply-To:" field will contain the contents of the
- "Message-ID:" field of the message to which this one is a reply (the
- "parent message"). If there is more than one parent message, then
- the "In-Reply-To:" field will contain the contents of all of the
- parents' "Message-ID:" fields. If there is no "Message-ID:" field in
- any of the parent messages, then the new message will have no "In-
- Reply-To:" field.
-
- The "References:" field will contain the contents of the parent's
- "References:" field (if any) followed by the contents of the parent's
- "Message-ID:" field (if any). If the parent message does not contain
- a "References:" field but does have an "In-Reply-To:" field
- containing a single message identifier, then the "References:" field
- will contain the contents of the parent's "In-Reply-To:" field
- followed by the contents of the parent's "Message-ID:" field (if
- any). If the parent has none of the "References:", "In-Reply-To:",
- or "Message-ID:" fields, then the new message will have no
- "References:" field.
-
-
-
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-RFC 5322 Internet Message Format October 2008
-
-
- Note: Some implementations parse the "References:" field to
- display the "thread of the discussion". These implementations
- assume that each new message is a reply to a single parent and
- hence that they can walk backwards through the "References:" field
- to find the parent of each message listed there. Therefore,
- trying to form a "References:" field for a reply that has multiple
- parents is discouraged; how to do so is not defined in this
- document.
-
- The message identifier (msg-id) itself MUST be a globally unique
- identifier for a message. The generator of the message identifier
- MUST guarantee that the msg-id is unique. There are several
- algorithms that can be used to accomplish this. Since the msg-id has
- a similar syntax to addr-spec (identical except that quoted strings,
- comments, and folding white space are not allowed), a good method is
- to put the domain name (or a domain literal IP address) of the host
- on which the message identifier was created on the right-hand side of
- the "@" (since domain names and IP addresses are normally unique),
- and put a combination of the current absolute date and time along
- with some other currently unique (perhaps sequential) identifier
- available on the system (for example, a process id number) on the
- left-hand side. Though other algorithms will work, it is RECOMMENDED
- that the right-hand side contain some domain identifier (either of
- the host itself or otherwise) such that the generator of the message
- identifier can guarantee the uniqueness of the left-hand side within
- the scope of that domain.
-
- Semantically, the angle bracket characters are not part of the
- msg-id; the msg-id is what is contained between the two angle bracket
- characters.
-
-3.6.5. Informational Fields
-
- The informational fields are all optional. The "Subject:" and
- "Comments:" fields are unstructured fields as defined in section
- 2.2.1, and therefore may contain text or folding white space. The
- "Keywords:" field contains a comma-separated list of one or more
- words or quoted-strings.
-
- subject = "Subject:" unstructured CRLF
-
- comments = "Comments:" unstructured CRLF
-
- keywords = "Keywords:" phrase *("," phrase) CRLF
-
- These three fields are intended to have only human-readable content
- with information about the message. The "Subject:" field is the most
- common and contains a short string identifying the topic of the
-
-
-
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-RFC 5322 Internet Message Format October 2008
-
-
- message. When used in a reply, the field body MAY start with the
- string "Re: " (an abbreviation of the Latin "in re", meaning "in the
- matter of") followed by the contents of the "Subject:" field body of
- the original message. If this is done, only one instance of the
- literal string "Re: " ought to be used since use of other strings or
- more than one instance can lead to undesirable consequences. The
- "Comments:" field contains any additional comments on the text of the
- body of the message. The "Keywords:" field contains a comma-
- separated list of important words and phrases that might be useful
- for the recipient.
-
-3.6.6. Resent Fields
-
- Resent fields SHOULD be added to any message that is reintroduced by
- a user into the transport system. A separate set of resent fields
- SHOULD be added each time this is done. All of the resent fields
- corresponding to a particular resending of the message SHOULD be
- grouped together. Each new set of resent fields is prepended to the
- message; that is, the most recent set of resent fields appears
- earlier in the message. No other fields in the message are changed
- when resent fields are added.
-
- Each of the resent fields corresponds to a particular field elsewhere
- in the syntax. For instance, the "Resent-Date:" field corresponds to
- the "Date:" field and the "Resent-To:" field corresponds to the "To:"
- field. In each case, the syntax for the field body is identical to
- the syntax given previously for the corresponding field.
-
- When resent fields are used, the "Resent-From:" and "Resent-Date:"
- fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
- "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
- identical to "Resent-From:".
-
- resent-date = "Resent-Date:" date-time CRLF
-
- resent-from = "Resent-From:" mailbox-list CRLF
-
- resent-sender = "Resent-Sender:" mailbox CRLF
-
- resent-to = "Resent-To:" address-list CRLF
-
- resent-cc = "Resent-Cc:" address-list CRLF
-
- resent-bcc = "Resent-Bcc:" [address-list / CFWS] CRLF
-
- resent-msg-id = "Resent-Message-ID:" msg-id CRLF
-
-
-
-
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-
-
- Resent fields are used to identify a message as having been
- reintroduced into the transport system by a user. The purpose of
- using resent fields is to have the message appear to the final
- recipient as if it were sent directly by the original sender, with
- all of the original fields remaining the same. Each set of resent
- fields correspond to a particular resending event. That is, if a
- message is resent multiple times, each set of resent fields gives
- identifying information for each individual time. Resent fields are
- strictly informational. They MUST NOT be used in the normal
- processing of replies or other such automatic actions on messages.
-
- Note: Reintroducing a message into the transport system and using
- resent fields is a different operation from "forwarding".
- "Forwarding" has two meanings: One sense of forwarding is that a
- mail reading program can be told by a user to forward a copy of a
- message to another person, making the forwarded message the body
- of the new message. A forwarded message in this sense does not
- appear to have come from the original sender, but is an entirely
- new message from the forwarder of the message. Forwarding may
- also mean that a mail transport program gets a message and
- forwards it on to a different destination for final delivery.
- Resent header fields are not intended for use with either type of
- forwarding.
-
- The resent originator fields indicate the mailbox of the person(s) or
- system(s) that resent the message. As with the regular originator
- fields, there are two forms: a simple "Resent-From:" form, which
- contains the mailbox of the individual doing the resending, and the
- more complex form, when one individual (identified in the "Resent-
- Sender:" field) resends a message on behalf of one or more others
- (identified in the "Resent-From:" field).
-
- Note: When replying to a resent message, replies behave just as
- they would with any other message, using the original "From:",
- "Reply-To:", "Message-ID:", and other fields. The resent fields
- are only informational and MUST NOT be used in the normal
- processing of replies.
-
- The "Resent-Date:" indicates the date and time at which the resent
- message is dispatched by the resender of the message. Like the
- "Date:" field, it is not the date and time that the message was
- actually transported.
-
- The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
- identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
- except that they indicate the recipients of the resent message, not
- the recipients of the original message.
-
-
-
-
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-RFC 5322 Internet Message Format October 2008
-
-
- The "Resent-Message-ID:" field provides a unique identifier for the
- resent message.
-
-3.6.7. Trace Fields
-
- The trace fields are a group of header fields consisting of an
- optional "Return-Path:" field, and one or more "Received:" fields.
- The "Return-Path:" header field contains a pair of angle brackets
- that enclose an optional addr-spec. The "Received:" field contains a
- (possibly empty) list of tokens followed by a semicolon and a date-
- time specification. Each token must be a word, angle-addr, addr-
- spec, or a domain. Further restrictions are applied to the syntax of
- the trace fields by specifications that provide for their use, such
- as [RFC5321].
-
- trace = [return]
- 1*received
-
- return = "Return-Path:" path CRLF
-
- path = angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
-
- received = "Received:" *received-token ";" date-time CRLF
-
- received-token = word / angle-addr / addr-spec / domain
-
- A full discussion of the Internet mail use of trace fields is
- contained in [RFC5321]. For the purposes of this specification, the
- trace fields are strictly informational, and any formal
- interpretation of them is outside of the scope of this document.
-
-3.6.8. Optional Fields
-
- Fields may appear in messages that are otherwise unspecified in this
- document. They MUST conform to the syntax of an optional-field.
- This is a field name, made up of the printable US-ASCII characters
- except SP and colon, followed by a colon, followed by any text that
- conforms to the unstructured syntax.
-
- The field names of any optional field MUST NOT be identical to any
- field name specified elsewhere in this document.
-
-
-
-
-
-
-
-
-
-
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-
-RFC 5322 Internet Message Format October 2008
-
-
- optional-field = field-name ":" unstructured CRLF
-
- field-name = 1*ftext
-
- ftext = %d33-57 / ; Printable US-ASCII
- %d59-126 ; characters not including
- ; ":".
-
- For the purposes of this specification, any optional field is
- uninterpreted.
-
-4. Obsolete Syntax
-
- Earlier versions of this specification allowed for different (usually
- more liberal) syntax than is allowed in this version. Also, there
- have been syntactic elements used in messages on the Internet whose
- interpretations have never been documented. Though these syntactic
- forms MUST NOT be generated according to the grammar in section 3,
- they MUST be accepted and parsed by a conformant receiver. This
- section documents many of these syntactic elements. Taking the
- grammar in section 3 and adding the definitions presented in this
- section will result in the grammar to use for the interpretation of
- messages.
-
- Note: This section identifies syntactic forms that any
- implementation MUST reasonably interpret. However, there are
- certainly Internet messages that do not conform to even the
- additional syntax given in this section. The fact that a
- particular form does not appear in any section of this document is
- not justification for computer programs to crash or for malformed
- data to be irretrievably lost by any implementation. It is up to
- the implementation to deal with messages robustly.
-
- One important difference between the obsolete (interpreting) and the
- current (generating) syntax is that in structured header field bodies
- (i.e., between the colon and the CRLF of any structured header
- field), white space characters, including folding white space, and
- comments could be freely inserted between any syntactic tokens. This
- allowed many complex forms that have proven difficult for some
- implementations to parse.
-
- Another key difference between the obsolete and the current syntax is
- that the rule in section 3.2.2 regarding lines composed entirely of
- white space in comments and folding white space does not apply. See
- the discussion of folding white space in section 4.2 below.
-
- Finally, certain characters that were formerly allowed in messages
- appear in this section. The NUL character (ASCII value 0) was once
-
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-
- allowed, but is no longer for compatibility reasons. Similarly, US-
- ASCII control characters other than CR, LF, SP, and HTAB (ASCII
- values 1 through 8, 11, 12, 14 through 31, and 127) were allowed to
- appear in header field bodies. CR and LF were allowed to appear in
- messages other than as CRLF; this use is also shown here.
-
- Other differences in syntax and semantics are noted in the following
- sections.
-
-4.1. Miscellaneous Obsolete Tokens
-
- These syntactic elements are used elsewhere in the obsolete syntax or
- in the main syntax. Bare CR, bare LF, and NUL are added to obs-qp,
- obs-body, and obs-unstruct. US-ASCII control characters are added to
- obs-qp, obs-unstruct, obs-ctext, and obs-qtext. The period character
- is added to obs-phrase. The obs-phrase-list provides for a
- (potentially empty) comma-separated list of phrases that may include
- "null" elements. That is, there could be two or more commas in such
- a list with nothing in between them, or commas at the beginning or
- end of the list.
-
- Note: The "period" (or "full stop") character (".") in obs-phrase
- is not a form that was allowed in earlier versions of this or any
- other specification. Period (nor any other character from
- specials) was not allowed in phrase because it introduced a
- parsing difficulty distinguishing between phrases and portions of
- an addr-spec (see section 4.4). It appears here because the
- period character is currently used in many messages in the
- display-name portion of addresses, especially for initials in
- names, and therefore must be interpreted properly.
-
- obs-NO-WS-CTL = %d1-8 / ; US-ASCII control
- %d11 / ; characters that do not
- %d12 / ; include the carriage
- %d14-31 / ; return, line feed, and
- %d127 ; white space characters
-
- obs-ctext = obs-NO-WS-CTL
-
- obs-qtext = obs-NO-WS-CTL
-
- obs-utext = %d0 / obs-NO-WS-CTL / VCHAR
-
- obs-qp = "\" (%d0 / obs-NO-WS-CTL / LF / CR)
-
- obs-body = *((*LF *CR *((%d0 / text) *LF *CR)) / CRLF)
-
- obs-unstruct = *((*LF *CR *(obs-utext *LF *CR)) / FWS)
-
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-
- obs-phrase = word *(word / "." / CFWS)
-
- obs-phrase-list = [phrase / CFWS] *("," [phrase / CFWS])
-
- Bare CR and bare LF appear in messages with two different meanings.
- In many cases, bare CR or bare LF are used improperly instead of CRLF
- to indicate line separators. In other cases, bare CR and bare LF are
- used simply as US-ASCII control characters with their traditional
- ASCII meanings.
-
-4.2. Obsolete Folding White Space
-
- In the obsolete syntax, any amount of folding white space MAY be
- inserted where the obs-FWS rule is allowed. This creates the
- possibility of having two consecutive "folds" in a line, and
- therefore the possibility that a line which makes up a folded header
- field could be composed entirely of white space.
-
- obs-FWS = 1*WSP *(CRLF 1*WSP)
-
-4.3. Obsolete Date and Time
-
- The syntax for the obsolete date format allows a 2 digit year in the
- date field and allows for a list of alphabetic time zone specifiers
- that were used in earlier versions of this specification. It also
- permits comments and folding white space between many of the tokens.
-
- obs-day-of-week = [CFWS] day-name [CFWS]
-
- obs-day = [CFWS] 1*2DIGIT [CFWS]
-
- obs-year = [CFWS] 2*DIGIT [CFWS]
-
- obs-hour = [CFWS] 2DIGIT [CFWS]
-
- obs-minute = [CFWS] 2DIGIT [CFWS]
-
- obs-second = [CFWS] 2DIGIT [CFWS]
-
- obs-zone = "UT" / "GMT" / ; Universal Time
- ; North American UT
- ; offsets
- "EST" / "EDT" / ; Eastern: - 5/ - 4
- "CST" / "CDT" / ; Central: - 6/ - 5
- "MST" / "MDT" / ; Mountain: - 7/ - 6
- "PST" / "PDT" / ; Pacific: - 8/ - 7
- ;
-
-
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-
- %d65-73 / ; Military zones - "A"
- %d75-90 / ; through "I" and "K"
- %d97-105 / ; through "Z", both
- %d107-122 ; upper and lower case
-
- Where a two or three digit year occurs in a date, the year is to be
- interpreted as follows: If a two digit year is encountered whose
- value is between 00 and 49, the year is interpreted by adding 2000,
- ending up with a value between 2000 and 2049. If a two digit year is
- encountered with a value between 50 and 99, or any three digit year
- is encountered, the year is interpreted by adding 1900.
-
- In the obsolete time zone, "UT" and "GMT" are indications of
- "Universal Time" and "Greenwich Mean Time", respectively, and are
- both semantically identical to "+0000".
-
- The remaining three character zones are the US time zones. The first
- letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
- "Mountain", and "Pacific". The second letter is either "S" for
- "Standard" time, or "D" for "Daylight Savings" (or summer) time.
- Their interpretations are as follows:
-
- EDT is semantically equivalent to -0400
- EST is semantically equivalent to -0500
- CDT is semantically equivalent to -0500
- CST is semantically equivalent to -0600
- MDT is semantically equivalent to -0600
- MST is semantically equivalent to -0700
- PDT is semantically equivalent to -0700
- PST is semantically equivalent to -0800
-
- The 1 character military time zones were defined in a non-standard
- way in [RFC0822] and are therefore unpredictable in their meaning.
- The original definitions of the military zones "A" through "I" are
- equivalent to "+0100" through "+0900", respectively; "K", "L", and
- "M" are equivalent to "+1000", "+1100", and "+1200", respectively;
- "N" through "Y" are equivalent to "-0100" through "-1200".
- respectively; and "Z" is equivalent to "+0000". However, because of
- the error in [RFC0822], they SHOULD all be considered equivalent to
- "-0000" unless there is out-of-band information confirming their
- meaning.
-
- Other multi-character (usually between 3 and 5) alphabetic time zones
- have been used in Internet messages. Any such time zone whose
- meaning is not known SHOULD be considered equivalent to "-0000"
- unless there is out-of-band information confirming their meaning.
-
-
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-
-4.4. Obsolete Addressing
-
- There are four primary differences in addressing. First, mailbox
- addresses were allowed to have a route portion before the addr-spec
- when enclosed in "<" and ">". The route is simply a comma-separated
- list of domain names, each preceded by "@", and the list terminated
- by a colon. Second, CFWS were allowed between the period-separated
- elements of local-part and domain (i.e., dot-atom was not used). In
- addition, local-part is allowed to contain quoted-string in addition
- to just atom. Third, mailbox-list and address-list were allowed to
- have "null" members. That is, there could be two or more commas in
- such a list with nothing in between them, or commas at the beginning
- or end of the list. Finally, US-ASCII control characters and quoted-
- pairs were allowed in domain literals and are added here.
-
- obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
-
- obs-route = obs-domain-list ":"
-
- obs-domain-list = *(CFWS / ",") "@" domain
- *("," [CFWS] ["@" domain])
-
- obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
-
- obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
-
- obs-group-list = 1*([CFWS] ",") [CFWS]
-
- obs-local-part = word *("." word)
-
- obs-domain = atom *("." atom)
-
- obs-dtext = obs-NO-WS-CTL / quoted-pair
-
- When interpreting addresses, the route portion SHOULD be ignored.
-
-4.5. Obsolete Header Fields
-
- Syntactically, the primary difference in the obsolete field syntax is
- that it allows multiple occurrences of any of the fields and they may
- occur in any order. Also, any amount of white space is allowed
- before the ":" at the end of the field name.
-
-
-
-
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-
- obs-fields = *(obs-return /
- obs-received /
- obs-orig-date /
- obs-from /
- obs-sender /
- obs-reply-to /
- obs-to /
- obs-cc /
- obs-bcc /
- obs-message-id /
- obs-in-reply-to /
- obs-references /
- obs-subject /
- obs-comments /
- obs-keywords /
- obs-resent-date /
- obs-resent-from /
- obs-resent-send /
- obs-resent-rply /
- obs-resent-to /
- obs-resent-cc /
- obs-resent-bcc /
- obs-resent-mid /
- obs-optional)
-
- Except for destination address fields (described in section 4.5.3),
- the interpretation of multiple occurrences of fields is unspecified.
- Also, the interpretation of trace fields and resent fields that do
- not occur in blocks prepended to the message is unspecified as well.
- Unless otherwise noted in the following sections, interpretation of
- other fields is identical to the interpretation of their non-obsolete
- counterparts in section 3.
-
-4.5.1. Obsolete Origination Date Field
-
- obs-orig-date = "Date" *WSP ":" date-time CRLF
-
-4.5.2. Obsolete Originator Fields
-
- obs-from = "From" *WSP ":" mailbox-list CRLF
-
- obs-sender = "Sender" *WSP ":" mailbox CRLF
-
- obs-reply-to = "Reply-To" *WSP ":" address-list CRLF
-
-
-
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-
-
-4.5.3. Obsolete Destination Address Fields
-
- obs-to = "To" *WSP ":" address-list CRLF
-
- obs-cc = "Cc" *WSP ":" address-list CRLF
-
- obs-bcc = "Bcc" *WSP ":"
- (address-list / (*([CFWS] ",") [CFWS])) CRLF
-
- When multiple occurrences of destination address fields occur in a
- message, they SHOULD be treated as if the address list in the first
- occurrence of the field is combined with the address lists of the
- subsequent occurrences by adding a comma and concatenating.
-
-4.5.4. Obsolete Identification Fields
-
- The obsolete "In-Reply-To:" and "References:" fields differ from the
- current syntax in that they allow phrase (words or quoted strings) to
- appear. The obsolete forms of the left and right sides of msg-id
- allow interspersed CFWS, making them syntactically identical to
- local-part and domain, respectively.
-
- obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
-
- obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
-
- obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
-
- obs-id-left = local-part
-
- obs-id-right = domain
-
- For purposes of interpretation, the phrases in the "In-Reply-To:" and
- "References:" fields are ignored.
-
- Semantically, none of the optional CFWS in the local-part and the
- domain is part of the obs-id-left and obs-id-right, respectively.
-
-4.5.5. Obsolete Informational Fields
-
- obs-subject = "Subject" *WSP ":" unstructured CRLF
-
- obs-comments = "Comments" *WSP ":" unstructured CRLF
-
- obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
-
-
-
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-
-
-4.5.6. Obsolete Resent Fields
-
- The obsolete syntax adds a "Resent-Reply-To:" field, which consists
- of the field name, the optional comments and folding white space, the
- colon, and a comma separated list of addresses.
-
- obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
-
- obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
-
- obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
-
- obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
-
- obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
-
- obs-resent-bcc = "Resent-Bcc" *WSP ":"
- (address-list / (*([CFWS] ",") [CFWS])) CRLF
-
- obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
-
- obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
-
- As with other resent fields, the "Resent-Reply-To:" field is to be
- treated as trace information only.
-
-4.5.7. Obsolete Trace Fields
-
- The obs-return and obs-received are again given here as template
- definitions, just as return and received are in section 3. Their
- full syntax is given in [RFC5321].
-
- obs-return = "Return-Path" *WSP ":" path CRLF
-
- obs-received = "Received" *WSP ":" *received-token CRLF
-
-4.5.8. Obsolete optional fields
-
- obs-optional = field-name *WSP ":" unstructured CRLF
-
-5. Security Considerations
-
- Care needs to be taken when displaying messages on a terminal or
- terminal emulator. Powerful terminals may act on escape sequences
- and other combinations of US-ASCII control characters with a variety
- of consequences. They can remap the keyboard or permit other
- modifications to the terminal that could lead to denial of service or
- even damaged data. They can trigger (sometimes programmable)
-
-
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-
-
- answerback messages that can allow a message to cause commands to be
- issued on the recipient's behalf. They can also affect the operation
- of terminal attached devices such as printers. Message viewers may
- wish to strip potentially dangerous terminal escape sequences from
- the message prior to display. However, other escape sequences appear
- in messages for useful purposes (cf. [ISO.2022.1994], [RFC2045],
- [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]) and therefore
- should not be stripped indiscriminately.
-
- Transmission of non-text objects in messages raises additional
- security issues. These issues are discussed in [RFC2045], [RFC2046],
- [RFC2047], [RFC2049], [RFC4288], and [RFC4289].
-
- Many implementations use the "Bcc:" (blind carbon copy) field,
- described in section 3.6.3, to facilitate sending messages to
- recipients without revealing the addresses of one or more of the
- addressees to the other recipients. Mishandling this use of "Bcc:"
- may disclose confidential information that could eventually lead to
- security problems through knowledge of even the existence of a
- particular mail address. For example, if using the first method
- described in section 3.6.3, where the "Bcc:" line is removed from the
- message, blind recipients have no explicit indication that they have
- been sent a blind copy, except insofar as their address does not
- appear in the header section of a message. Because of this, one of
- the blind addressees could potentially send a reply to all of the
- shown recipients and accidentally reveal that the message went to the
- blind recipient. When the second method from section 3.6.3 is used,
- the blind recipient's address appears in the "Bcc:" field of a
- separate copy of the message. If the "Bcc:" field sent contains all
- of the blind addressees, all of the "Bcc:" recipients will be seen by
- each "Bcc:" recipient. Even if a separate message is sent to each
- "Bcc:" recipient with only the individual's address, implementations
- still need to be careful to process replies to the message as per
- section 3.6.3 so as not to accidentally reveal the blind recipient to
- other recipients.
-
-6. IANA Considerations
-
- This document updates the registrations that appeared in [RFC4021]
- that referred to the definitions in [RFC2822]. IANA has updated the
- Permanent Message Header Field Repository with the following header
- fields, in accordance with the procedures set out in [RFC3864].
-
- Header field name: Date
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.1)
-
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-
- Header field name: From
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.2)
-
- Header field name: Sender
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.2)
-
- Header field name: Reply-To
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.2)
-
- Header field name: To
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.3)
-
- Header field name: Cc
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.3)
-
- Header field name: Bcc
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.3)
-
- Header field name: Message-ID
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.4)
-
- Header field name: In-Reply-To
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.4)
-
-
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-
- Header field name: References
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.4)
-
- Header field name: Subject
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.5)
-
- Header field name: Comments
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.5)
-
- Header field name: Keywords
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.5)
-
- Header field name: Resent-Date
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Resent-From
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Resent-Sender
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Resent-To
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
-
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-
-
- Header field name: Resent-Cc
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Resent-Bcc
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Resent-Reply-To
- Applicable protocol: Mail
- Status: obsolete
- Author/Change controller: IETF
- Specification document(s): This document (section 4.5.6)
-
- Header field name: Resent-Message-ID
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.6)
-
- Header field name: Return-Path
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.7)
-
- Header field name: Received
- Applicable protocol: Mail
- Status: standard
- Author/Change controller: IETF
- Specification document(s): This document (section 3.6.7)
- Related information: [RFC5321]
-
-
-
-
-
-
-
-
-
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-
-Appendix A. Example Messages
-
- This section presents a selection of messages. These are intended to
- assist in the implementation of this specification, but should not be
- taken as normative; that is to say, although the examples in this
- section were carefully reviewed, if there happens to be a conflict
- between these examples and the syntax described in sections 3 and 4
- of this document, the syntax in those sections is to be taken as
- correct.
-
- In the text version of this document, messages in this section are
- delimited between lines of "----". The "----" lines are not part of
- the message itself.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-Appendix A.1. Addressing Examples
-
- The following are examples of messages that might be sent between two
- individuals.
-
-Appendix A.1.1. A Message from One Person to Another with Simple
- Addressing
-
- This could be called a canonical message. It has a single author,
- John Doe, a single recipient, Mary Smith, a subject, the date, a
- message identifier, and a textual message in the body.
-
- ----
- From: John Doe <jdoe@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
- If John's secretary Michael actually sent the message, even though
- John was the author and replies to this message should go back to
- him, the sender field would be used:
-
- ----
- From: John Doe <jdoe@machine.example>
- Sender: Michael Jones <mjones@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
-
-
-
-
-
-
-
-
-
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-
-Appendix A.1.2. Different Types of Mailboxes
-
- This message includes multiple addresses in the destination fields
- and also uses several different forms of addresses.
-
- ----
- From: "Joe Q. Public" <john.q.public@example.com>
- To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
- Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
- Date: Tue, 1 Jul 2003 10:52:37 +0200
- Message-ID: <5678.21-Nov-1997@example.com>
-
- Hi everyone.
- ----
-
- Note that the display names for Joe Q. Public and Giant; "Big" Box
- needed to be enclosed in double-quotes because the former contains
- the period and the latter contains both semicolon and double-quote
- characters (the double-quote characters appearing as quoted-pair
- constructs). Conversely, the display name for Who? could appear
- without them because the question mark is legal in an atom. Notice
- also that jdoe@example.org and boss@nil.test have no display names
- associated with them at all, and jdoe@example.org uses the simpler
- address form without the angle brackets.
-
-Appendix A.1.3. Group Addresses
-
- ----
- From: Pete <pete@silly.example>
- To: A Group:Ed Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
- Cc: Undisclosed recipients:;
- Date: Thu, 13 Feb 1969 23:32:54 -0330
- Message-ID: <testabcd.1234@silly.example>
-
- Testing.
- ----
-
- In this message, the "To:" field has a single group recipient named
- "A Group", which contains 3 addresses, and a "Cc:" field with an
- empty group recipient named Undisclosed recipients.
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 45]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Appendix A.2. Reply Messages
-
- The following is a series of three messages that make up a
- conversation thread between John and Mary. John first sends a
- message to Mary, Mary then replies to John's message, and then John
- replies to Mary's reply message.
-
- Note especially the "Message-ID:", "References:", and "In-Reply-To:"
- fields in each message.
-
- ----
- From: John Doe <jdoe@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
- When sending replies, the Subject field is often retained, though
- prepended with "Re: " as described in section 3.6.5.
-
- ----
- From: Mary Smith <mary@example.net>
- To: John Doe <jdoe@machine.example>
- Reply-To: "Mary Smith: Personal Account" <smith@home.example>
- Subject: Re: Saying Hello
- Date: Fri, 21 Nov 1997 10:01:10 -0600
- Message-ID: <3456@example.net>
- In-Reply-To: <1234@local.machine.example>
- References: <1234@local.machine.example>
-
- This is a reply to your hello.
- ----
-
- Note the "Reply-To:" field in the above message. When John replies
- to Mary's message above, the reply should go to the address in the
- "Reply-To:" field instead of the address in the "From:" field.
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 46]
-
-RFC 5322 Internet Message Format October 2008
-
-
- ----
- To: "Mary Smith: Personal Account" <smith@home.example>
- From: John Doe <jdoe@machine.example>
- Subject: Re: Saying Hello
- Date: Fri, 21 Nov 1997 11:00:00 -0600
- Message-ID: <abcd.1234@local.machine.test>
- In-Reply-To: <3456@example.net>
- References: <1234@local.machine.example> <3456@example.net>
-
- This is a reply to your reply.
- ----
-
-Appendix A.3. Resent Messages
-
- Start with the message that has been used as an example several
- times:
-
- ----
- From: John Doe <jdoe@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
- Say that Mary, upon receiving this message, wishes to send a copy of
- the message to Jane such that (a) the message would appear to have
- come straight from John; (b) if Jane replies to the message, the
- reply should go back to John; and (c) all of the original
- information, like the date the message was originally sent to Mary,
- the message identifier, and the original addressee, is preserved. In
- this case, resent fields are prepended to the message:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 47]
-
-RFC 5322 Internet Message Format October 2008
-
-
- ----
- Resent-From: Mary Smith <mary@example.net>
- Resent-To: Jane Brown <j-brown@other.example>
- Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
- Resent-Message-ID: <78910@example.net>
- From: John Doe <jdoe@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
- If Jane, in turn, wished to resend this message to another person,
- she would prepend her own set of resent header fields to the above
- and send that. (Note that for brevity, trace fields are not shown.)
-
-Appendix A.4. Messages with Trace Fields
-
- As messages are sent through the transport system as described in
- [RFC5321], trace fields are prepended to the message. The following
- is an example of what those trace fields might look like. Note that
- there is some folding white space in the first one since these lines
- can be long.
-
- ----
- Received: from x.y.test
- by example.net
- via TCP
- with ESMTP
- id ABC12345
- for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
- Received: from node.example by x.y.test; 21 Nov 1997 10:01:22 -0600
- From: John Doe <jdoe@node.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: Fri, 21 Nov 1997 09:55:06 -0600
- Message-ID: <1234@local.node.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
-
-
-
-
-
-
-Resnick Standards Track [Page 48]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Appendix A.5. White Space, Comments, and Other Oddities
-
- White space, including folding white space, and comments can be
- inserted between many of the tokens of fields. Taking the example
- from A.1.3, white space and comments can be inserted into all of the
- fields.
-
- ----
- From: Pete(A nice \) chap) <pete(his account)@silly.test(his host)>
- To:A Group(Some people)
- :Chris Jones <c@(Chris's host.)public.example>,
- joe@example.org,
- John <jdoe@one.test> (my dear friend); (the end of the group)
- Cc:(Empty list)(start)Hidden recipients :(nobody(that I know)) ;
- Date: Thu,
- 13
- Feb
- 1969
- 23:32
- -0330 (Newfoundland Time)
- Message-ID: <testabcd.1234@silly.test>
-
- Testing.
- ----
-
- The above example is aesthetically displeasing, but perfectly legal.
- Note particularly (1) the comments in the "From:" field (including
- one that has a ")" character appearing as part of a quoted-pair); (2)
- the white space absent after the ":" in the "To:" field as well as
- the comment and folding white space after the group name, the special
- character (".") in the comment in Chris Jones's address, and the
- folding white space before and after "joe@example.org,"; (3) the
- multiple and nested comments in the "Cc:" field as well as the
- comment immediately following the ":" after "Cc"; (4) the folding
- white space (but no comments except at the end) and the missing
- seconds in the time of the date field; and (5) the white space before
- (but not within) the identifier in the "Message-ID:" field.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 49]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Appendix A.6. Obsoleted Forms
-
- The following are examples of obsolete (that is, the "MUST NOT
- generate") syntactic elements described in section 4 of this
- document.
-
-Appendix A.6.1. Obsolete Addressing
-
- Note in the example below the lack of quotes around Joe Q. Public,
- the route that appears in the address for Mary Smith, the two commas
- that appear in the "To:" field, and the spaces that appear around the
- "." in the jdoe address.
-
- ----
- From: Joe Q. Public <john.q.public@example.com>
- To: Mary Smith <@node.test:mary@example.net>, , jdoe@test . example
- Date: Tue, 1 Jul 2003 10:52:37 +0200
- Message-ID: <5678.21-Nov-1997@example.com>
-
- Hi everyone.
- ----
-
-Appendix A.6.2. Obsolete Dates
-
- The following message uses an obsolete date format, including a non-
- numeric time zone and a two digit year. Note that although the day-
- of-week is missing, that is not specific to the obsolete syntax; it
- is optional in the current syntax as well.
-
- ----
- From: John Doe <jdoe@machine.example>
- To: Mary Smith <mary@example.net>
- Subject: Saying Hello
- Date: 21 Nov 97 09:55:06 GMT
- Message-ID: <1234@local.machine.example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 50]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Appendix A.6.3. Obsolete White Space and Comments
-
- White space and comments can appear between many more elements than
- in the current syntax. Also, folding lines that are made up entirely
- of white space are legal.
-
- ----
- From : John Doe <jdoe@machine(comment). example>
- To : Mary Smith
- __
- <mary@example.net>
- Subject : Saying Hello
- Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
- Message-ID : <1234 @ local(blah) .machine .example>
-
- This is a message just to say hello.
- So, "Hello".
- ----
-
- Note especially the second line of the "To:" field. It starts with
- two space characters. (Note that "__" represent blank spaces.)
- Therefore, it is considered part of the folding, as described in
- section 4.2. Also, the comments and white space throughout
- addresses, dates, and message identifiers are all part of the
- obsolete syntax.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 51]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Appendix B. Differences from Earlier Specifications
-
- This appendix contains a list of changes that have been made in the
- Internet Message Format from earlier specifications, specifically
- [RFC0822], [RFC1123], and [RFC2822]. Items marked with an asterisk
- (*) below are items which appear in section 4 of this document and
- therefore can no longer be generated.
-
- The following are the changes made from [RFC0822] and [RFC1123] to
- [RFC2822] that remain in this document:
-
- 1. Period allowed in obsolete form of phrase.
- 2. ABNF moved out of document, now in [RFC5234].
- 3. Four or more digits allowed for year.
- 4. Header field ordering (and lack thereof) made explicit.
- 5. Encrypted header field removed.
- 6. Specifically allow and give meaning to "-0000" time zone.
- 7. Folding white space is not allowed between every token.
- 8. Requirement for destinations removed.
- 9. Forwarding and resending redefined.
- 10. Extension header fields no longer specifically called out.
- 11. ASCII 0 (null) removed.*
- 12. Folding continuation lines cannot contain only white space.*
- 13. Free insertion of comments not allowed in date.*
- 14. Non-numeric time zones not allowed.*
- 15. Two digit years not allowed.*
- 16. Three digit years interpreted, but not allowed for generation.*
- 17. Routes in addresses not allowed.*
- 18. CFWS within local-parts and domains not allowed.*
- 19. Empty members of address lists not allowed.*
- 20. Folding white space between field name and colon not allowed.*
- 21. Comments between field name and colon not allowed.
- 22. Tightened syntax of in-reply-to and references.*
- 23. CFWS within msg-id not allowed.*
- 24. Tightened semantics of resent fields as informational only.
- 25. Resent-Reply-To not allowed.*
- 26. No multiple occurrences of fields (except resent and received).*
- 27. Free CR and LF not allowed.*
- 28. Line length limits specified.
- 29. Bcc more clearly specified.
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 52]
-
-RFC 5322 Internet Message Format October 2008
-
-
- The following are changes from [RFC2822].
- 1. Assorted typographical/grammatical errors fixed and
- clarifications made.
- 2. Changed "standard" to "document" or "specification" throughout.
- 3. Made distinction between "header field" and "header section".
- 4. Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
- 5. Moved discussion of specials to the "Atom" section. Moved text
- to "Overall message syntax" section.
- 6. Simplified CFWS syntax.
- 7. Fixed unstructured syntax.
- 8. Changed date and time syntax to deal with white space in
- obsolete date syntax.
- 9. Removed quoted-pair from domain literals and message
- identifiers.*
- 10. Clarified that other specifications limit domain syntax.
- 11. Simplified "Bcc:" and "Resent-Bcc:" syntax.
- 12. Allowed optional-field to appear within trace information.
- 13. Removed no-fold-quote from msg-id. Clarified syntax
- limitations.
- 14. Generalized "Received:" syntax to fix bugs and move definition
- out of this document.
- 15. Simplified obs-qp. Fixed and simplified obs-utext (which now
- only appears in the obsolete syntax). Removed obs-text and obs-
- char, adding obs-body.
- 16. Fixed obsolete date syntax to allow for more (or less) comments
- and white space.
- 17. Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list,
- obs-addr-list, obs-phrase-list, and the newly added obs-group-
- list).
- 18. Fixed obs-reply-to syntax.
- 19. Fixed obs-bcc and obs-resent-bcc to allow empty lists.
- 20. Removed obs-path.
-
-Appendix C. Acknowledgements
-
- Many people contributed to this document. They included folks who
- participated in the Detailed Revision and Update of Messaging
- Standards (DRUMS) Working Group of the Internet Engineering Task
- Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
- people who simply sent their comments in via email. The editor is
- deeply indebted to them all and thanks them sincerely. The below
- list includes everyone who sent email concerning both this document
- and [RFC2822]. Hopefully, everyone who contributed is named here:
-
- +--------------------+----------------------+---------------------+
- | Matti Aarnio | Tanaka Akira | Russ Allbery |
- | Eric Allman | Harald Alvestrand | Ran Atkinson |
- | Jos Backus | Bruce Balden | Dave Barr |
-
-
-
-Resnick Standards Track [Page 53]
-
-RFC 5322 Internet Message Format October 2008
-
-
- | Alan Barrett | John Beck | J Robert von Behren |
- | Jos den Bekker | D J Bernstein | James Berriman |
- | Oliver Block | Norbert Bollow | Raj Bose |
- | Antony Bowesman | Scott Bradner | Randy Bush |
- | Tom Byrer | Bruce Campbell | Larry Campbell |
- | W J Carpenter | Michael Chapman | Richard Clayton |
- | Maurizio Codogno | Jim Conklin | R Kelley Cook |
- | Nathan Coulter | Steve Coya | Mark Crispin |
- | Dave Crocker | Matt Curtin | Michael D'Errico |
- | Cyrus Daboo | Michael D Dean | Jutta Degener |
- | Mark Delany | Steve Dorner | Harold A Driscoll |
- | Michael Elkins | Frank Ellerman | Robert Elz |
- | Johnny Eriksson | Erik E Fair | Roger Fajman |
- | Patrik Faltstrom | Claus Andre Faerber | Barry Finkel |
- | Erik Forsberg | Chuck Foster | Paul Fox |
- | Klaus M Frank | Ned Freed | Jochen Friedrich |
- | Randall C Gellens | Sukvinder Singh Gill | Tim Goodwin |
- | Philip Guenther | Arnt Gulbrandsen | Eric A Hall |
- | Tony Hansen | John Hawkinson | Philip Hazel |
- | Kai Henningsen | Robert Herriot | Paul Hethmon |
- | Jim Hill | Alfred Hoenes | Paul E Hoffman |
- | Steve Hole | Kari Hurtta | Marco S Hyman |
- | Ofer Inbar | Olle Jarnefors | Kevin Johnson |
- | Sudish Joseph | Maynard Kang | Prabhat Keni |
- | John C Klensin | Graham Klyne | Brad Knowles |
- | Shuhei Kobayashi | Peter Koch | Dan Kohn |
- | Christian Kuhtz | Anand Kumria | Steen Larsen |
- | Eliot Lear | Barry Leiba | Jay Levitt |
- | Bruce Lilly | Lars-Johan Liman | Charles Lindsey |
- | Pete Loshin | Simon Lyall | Bill Manning |
- | John Martin | Mark Martinec | Larry Masinter |
- | Denis McKeon | William P McQuillan | Alexey Melnikov |
- | Perry E Metzger | Steven Miller | S Moonesamy |
- | Keith Moore | John Gardiner Myers | Chris Newman |
- | John W Noerenberg | Eric Norman | Mike O'Dell |
- | Larry Osterman | Paul Overell | Jacob Palme |
- | Michael A Patton | Uzi Paz | Michael A Quinlan |
- | Robert Rapplean | Eric S Raymond | Sam Roberts |
- | Hugh Sasse | Bart Schaefer | Tom Scola |
- | Wolfgang Segmuller | Nick Shelness | John Stanley |
- | Einar Stefferud | Jeff Stephenson | Bernard Stern |
- | Peter Sylvester | Mark Symons | Eric Thomas |
- | Lee Thompson | Karel De Vriendt | Matthew Wall |
- | Rolf Weber | Brent B Welch | Dan Wing |
- | Jack De Winter | Gregory J Woodhouse | Greg A Woods |
- | Kazu Yamamoto | Alain Zahm | Jamie Zawinski |
- | Timothy S Zurcher | | |
- +--------------------+----------------------+---------------------+
-
-
-
-Resnick Standards Track [Page 54]
-
-RFC 5322 Internet Message Format October 2008
-
-
-7. References
-
-7.1. Normative References
-
- [ANSI.X3-4.1986] American National Standards Institute, "Coded
- Character Set - 7-bit American Standard Code for
- Information Interchange", ANSI X3.4, 1986.
-
- [RFC1034] Mockapetris, P., "Domain names - concepts and
- facilities", STD 13, RFC 1034, November 1987.
-
- [RFC1035] Mockapetris, P., "Domain names - implementation and
- specification", STD 13, RFC 1035, November 1987.
-
- [RFC1123] Braden, R., "Requirements for Internet Hosts -
- Application and Support", STD 3, RFC 1123,
- October 1989.
-
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for
- Syntax Specifications: ABNF", STD 68, RFC 5234,
- January 2008.
-
-7.2. Informative References
-
- [RFC0822] Crocker, D., "Standard for the format of ARPA
- Internet text messages", STD 11, RFC 822,
- August 1982.
-
- [RFC1305] Mills, D., "Network Time Protocol (Version 3)
- Specification, Implementation", RFC 1305,
- March 1992.
-
- [ISO.2022.1994] International Organization for Standardization,
- "Information technology - Character code structure
- and extension techniques", ISO Standard 2022, 1994.
-
- [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
- Mail Extensions (MIME) Part One: Format of Internet
- Message Bodies", RFC 2045, November 1996.
-
- [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet
- Mail Extensions (MIME) Part Two: Media Types",
- RFC 2046, November 1996.
-
-
-
-
-
-Resnick Standards Track [Page 55]
-
-RFC 5322 Internet Message Format October 2008
-
-
- [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
- Extensions) Part Three: Message Header Extensions
- for Non-ASCII Text", RFC 2047, November 1996.
-
- [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet
- Mail Extensions (MIME) Part Five: Conformance
- Criteria and Examples", RFC 2049, November 1996.
-
- [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
- April 2001.
-
- [RFC3864] Klyne, G., Nottingham, M., and J. Mogul,
- "Registration Procedures for Message Header
- Fields", BCP 90, RFC 3864, September 2004.
-
- [RFC4021] Klyne, G. and J. Palme, "Registration of Mail and
- MIME Header Fields", RFC 4021, March 2005.
-
- [RFC4288] Freed, N. and J. Klensin, "Media Type
- Specifications and Registration Procedures",
- BCP 13, RFC 4288, December 2005.
-
- [RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet
- Mail Extensions (MIME) Part Four: Registration
- Procedures", BCP 13, RFC 4289, December 2005.
-
- [RFC5321] Klensin, J., "Simple Mail Transfer Protocol",
- RFC 5321, October 2008.
-
-Author's Address
-
- Peter W. Resnick (editor)
- Qualcomm Incorporated
- 5775 Morehouse Drive
- San Diego, CA 92121-1714
- US
-
- Phone: +1 858 651 4478
- EMail: presnick@qualcomm.com
- URI: http://www.qualcomm.com/~presnick/
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 56]
-
-RFC 5322 Internet Message Format October 2008
-
-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008).
-
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
- THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
- OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
- THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-
-
-
-
-
-
-
-
-
-
-
-Resnick Standards Track [Page 57]
-
diff --git a/proto/rfc5804.txt b/proto/rfc5804.txt
@@ -1,2747 +0,0 @@
-
-
-
-
-
-
-Internet Engineering Task Force (IETF) A. Melnikov, Ed.
-Request for Comments: 5804 Isode Limited
-Category: Standards Track T. Martin
-ISSN: 2070-1721 BeThereBeSquare, Inc.
- July 2010
-
-
- A Protocol for Remotely Managing Sieve Scripts
-
-Abstract
-
- Sieve scripts allow users to filter incoming email. Message stores
- are commonly sealed servers so users cannot log into them, yet users
- must be able to update their scripts on them. This document
- describes a protocol "ManageSieve" for securely managing Sieve
- scripts on a remote server. This protocol allows a user to have
- multiple scripts, and also alerts a user to syntactically flawed
- scripts.
-
-Status of This Memo
-
- This is an Internet Standards Track document.
-
- This document is a product of the Internet Engineering Task Force
- (IETF). It represents the consensus of the IETF community. It has
- received public review and has been approved for publication by the
- Internet Engineering Steering Group (IESG). Further information on
- Internet Standards is available in Section 2 of RFC 5741.
-
- Information about the current status of this document, any errata,
- and how to provide feedback on it may be obtained at
- http://www.rfc-editor.org/info/rfc5804.
-
-Copyright Notice
-
- Copyright (c) 2010 IETF Trust and the persons identified as the
- document authors. All rights reserved.
-
- This document is subject to BCP 78 and the IETF Trust's Legal
- Provisions Relating to IETF Documents
- (http://trustee.ietf.org/license-info) in effect on the date of
- publication of this document. Please review these documents
- carefully, as they describe your rights and restrictions with respect
- to this document. Code Components extracted from this document must
- include Simplified BSD License text as described in Section 4.e of
- the Trust Legal Provisions and are provided without warranty as
- described in the Simplified BSD License.
-
-
-
-
-Melnikov & Martin Standards Track [Page 1]
-
-RFC 5804 ManageSieve July 2010
-
-
-Table of Contents
-
- 1. Introduction ....................................................3
- 1.1. Commands and Responses .....................................3
- 1.2. Syntax .....................................................3
- 1.3. Response Codes .............................................3
- 1.4. Active Script ..............................................6
- 1.5. Quotas .....................................................6
- 1.6. Script Names ...............................................6
- 1.7. Capabilities ...............................................7
- 1.8. Transport ..................................................9
- 1.9. Conventions Used in This Document .........................10
- 2. Commands .......................................................10
- 2.1. AUTHENTICATE Command ......................................11
- 2.1.1. Use of SASL PLAIN Mechanism over TLS ...............16
- 2.2. STARTTLS Command ..........................................16
- 2.2.1. Server Identity Check ..............................17
- 2.3. LOGOUT Command ............................................20
- 2.4. CAPABILITY Command ........................................20
- 2.5. HAVESPACE Command .........................................20
- 2.6. PUTSCRIPT Command .........................................21
- 2.7. LISTSCRIPTS Command .......................................23
- 2.8. SETACTIVE Command .........................................24
- 2.9. GETSCRIPT Command .........................................25
- 2.10. DELETESCRIPT Command .....................................25
- 2.11. RENAMESCRIPT Command .....................................26
- 2.12. CHECKSCRIPT Command ......................................27
- 2.13. NOOP Command .............................................28
- 2.14. Recommended Extensions ...................................28
- 2.14.1. UNAUTHENTICATE Command ............................28
- 3. Sieve URL Scheme ...............................................29
- 4. Formal Syntax ..................................................31
- 5. Security Considerations ........................................37
- 6. IANA Considerations ............................................38
- 6.1. ManageSieve Capability Registration Template ..............39
- 6.2. Registration of Initial ManageSieve Capabilities ..........39
- 6.3. ManageSieve Response Code Registration Template ...........41
- 6.4. Registration of Initial ManageSieve Response Codes ........41
- 7. Internationalization Considerations ............................46
- 8. Acknowledgements ...............................................46
- 9. References .....................................................47
- 9.1. Normative References ......................................47
- 9.2. Informative References ....................................48
-
-
-
-
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-
-1. Introduction
-
-1.1. Commands and Responses
-
- A ManageSieve connection consists of the establishment of a client/
- server network connection, an initial greeting from the server, and
- client/server interactions. These client/server interactions consist
- of a client command, server data, and a server completion result
- response.
-
- All interactions transmitted by client and server are in the form of
- lines, that is, strings that end with a CRLF. The protocol receiver
- of a ManageSieve client or server is either reading a line or reading
- a sequence of octets with a known count followed by a line.
-
-1.2. Syntax
-
- ManageSieve is a line-oriented protocol much like [IMAP] or [ACAP],
- which runs over TCP. There are three data types: atoms, numbers and
- strings. Strings may be quoted or literal. See [ACAP] for detailed
- descriptions of these types.
-
- Each command consists of an atom (the command name) followed by zero
- or more strings and numbers terminated by CRLF.
-
- All client queries are replied to with either an OK, NO, or BYE
- response. Each response may be followed by a response code (see
- Section 1.3) and by a string consisting of human-readable text in the
- local language (as returned by the LANGUAGE capability; see
- Section 1.7), encoded in UTF-8 [UTF-8]. The contents of the string
- SHOULD be shown to the user ,and implementations MUST NOT attempt to
- parse the message for meaning.
-
- The BYE response SHOULD be used if the server wishes to close the
- connection. A server may wish to do this because the client was idle
- for too long or there were too many failed authentication attempts.
- This response can be issued at any time and should be immediately
- followed by a server hang-up of the connection. If a server has an
- inactivity timeout resulting in client autologout, it MUST be no less
- than 30 minutes after successful authentication. The inactivity
- timeout MAY be less before authentication.
-
-1.3. Response Codes
-
- An OK, NO, or BYE response from the server MAY contain a response
- code to describe the event in a more detailed machine-parsable
- fashion. A response code consists of data inside parentheses in the
- form of an atom, possibly followed by a space and arguments.
-
-
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-
- Response codes are defined when there is a specific action that a
- client can take based upon the additional information. In order to
- support future extension, the response code is represented as a
- slash-separated (Solidus, %x2F) hierarchy with each level of
- hierarchy representing increasing detail about the error. Response
- codes MUST NOT start with the Solidus character. Clients MUST
- tolerate additional hierarchical response code detail that they don't
- understand. For example, if the client supports the "QUOTA" response
- code, but doesn't understand the "QUOTA/MAXSCRIPTS" response code, it
- should treat "QUOTA/MAXSCRIPTS" as "QUOTA".
-
- Client implementations MUST tolerate (ignore) response codes that
- they do not recognize.
-
- The currently defined response codes are the following:
-
- AUTH-TOO-WEAK
-
- This response code is returned in the NO or BYE response from an
- AUTHENTICATE command. It indicates that site security policy forbids
- the use of the requested mechanism for the specified authentication
- identity.
-
- ENCRYPT-NEEDED
-
- This response code is returned in the NO or BYE response from an
- AUTHENTICATE command. It indicates that site security policy
- requires the use of a strong encryption mechanism for the specified
- authentication identity and mechanism.
-
- QUOTA
-
- If this response code is returned in the NO/BYE response, it means
- that the command would have placed the user above the site-defined
- quota constraints. If this response code is returned in the OK
- response, it can mean that the user's storage is near its quota, or
- it can mean that the account exceeded its quota but that the
- condition is being allowed by the server (the server supports
- so-called soft quotas). The QUOTA response code has two more
- detailed variants: "QUOTA/MAXSCRIPTS" (the maximum number of per-user
- scripts) and "QUOTA/MAXSIZE" (the maximum script size).
-
- REFERRAL
-
- This response code may be returned with a BYE result from any
- command, and includes a mandatory parameter that indicates what
- server to access to manage this user's Sieve scripts. The server
- will be specified by a Sieve URL (see Section 3). The scriptname
-
-
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-
- portion of the URL MUST NOT be specified. The client should
- authenticate to the specified server and use it for all further
- commands in the current session.
-
- SASL
-
- This response code can occur in the OK response to a successful
- AUTHENTICATE command and includes the optional final server response
- data from the server as specified by [SASL].
-
- TRANSITION-NEEDED
-
- This response code occurs in a NO response of an AUTHENTICATE
- command. It indicates that the user name is valid, but the entry in
- the authentication database needs to be updated in order to permit
- authentication with the specified mechanism. This is typically done
- by establishing a secure channel using TLS, verifying server identity
- as specified in Section 2.2.1, and finally authenticating once using
- the [PLAIN] authentication mechanism. The selected mechanism SHOULD
- then work for authentications in subsequent sessions.
-
- This condition can happen if a user has an entry in a system
- authentication database such as Unix /etc/passwd, but does not have
- credentials suitable for use by the specified mechanism.
-
- TRYLATER
-
- A command failed due to a temporary server failure. The client MAY
- continue using local information and try the command later. This
- response code only makes sense when returned in a NO/BYE response.
-
- ACTIVE
-
- A command failed because it is not allowed on the active script, for
- example, DELETESCRIPT on the active script. This response code only
- makes sense when returned in a NO/BYE response.
-
- NONEXISTENT
-
- A command failed because the referenced script name doesn't exist.
- This response code only makes sense when returned in a NO/BYE
- response.
-
- ALREADYEXISTS
-
- A command failed because the referenced script name already exists.
- This response code only makes sense when returned in a NO/BYE
- response.
-
-
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-
- TAG
-
- This response code name is followed by a string specified in the
- command. See Section 2.13 for a possible use case.
-
- WARNINGS
-
- This response code MAY be returned by the server in the OK response
- (but it might be returned with the NO/BYE response as well) and
- signals the client that even though the script is syntactically
- valid, it might contain errors not intended by the script writer.
- This response code is typically returned in response to PUTSCRIPT
- and/or CHECKSCRIPT commands. A client seeing such response code
- SHOULD present the returned warning text to the user.
-
-1.4. Active Script
-
- A user may have multiple Sieve scripts on the server, yet only one
- script may be used for filtering of incoming messages. This is the
- active script. Users may have zero or one active script and MUST use
- the SETACTIVE command described below for changing the active script
- or disabling Sieve processing. For example, users may have an
- everyday script they normally use and a special script they use when
- they go on vacation. Users can change which script is being used
- without having to download and upload a script stored somewhere else.
-
-1.5. Quotas
-
- Servers SHOULD impose quotas to prevent malicious users from
- overflowing available storage. If a command would place a user over
- a quota setting, servers that impose such quotas MUST reply with a NO
- response containing the QUOTA response code. Client implementations
- MUST be able to handle commands failing because of quota
- restrictions.
-
-1.6. Script Names
-
- A Sieve script name is a sequence of Unicode characters encoded in
- UTF-8 [UTF-8]. A script name MUST comply with Net-Unicode Definition
- (Section 2 of [NET-UNICODE]), with the additional restriction of
- prohibiting the following Unicode characters:
-
- o 0000-001F; [CONTROL CHARACTERS]
-
- o 007F; DELETE
-
- o 0080-009F; [CONTROL CHARACTERS]
-
-
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-
- o 2028; LINE SEPARATOR
-
- o 2029; PARAGRAPH SEPARATOR
-
- Sieve script names MUST be at least one octet (and hence Unicode
- character) long. Zero octets script name has a special meaning (see
- Section 2.8). Servers MUST allow names of up to 128 Unicode
- characters in length (which can take up to 512 bytes when encoded in
- UTF-8, not counting the terminating NUL), and MAY allow longer names.
- A server that receives a script name longer than its internal limit
- MUST reject the corresponding operation, in particular it MUST NOT
- truncate the script name.
-
-1.7. Capabilities
-
- Server capabilities are sent automatically by the server upon a
- client connection, or after successful STARTTLS and AUTHENTICATE
- (which establishes a Simple Authentication and Security Layer (SASL))
- commands. Capabilities may change immediately after a successfully
- completed STARTTLS command, and/or immediately after a successfully
- completed AUTHENTICATE command, and/or after a successfully completed
- UNAUTHENTICATE command (see Section 2.14.1). Capabilities MUST
- remain static at all other times.
-
- Clients MAY request the capabilities at a later time by issuing the
- CAPABILITY command described later. The capabilities consist of a
- series of lines each with one or two strings. The first string is
- the name of the capability, which is case-insensitive. The second
- optional string is the value associated with that capability. Order
- of capabilities is arbitrary, but each capability name can appear at
- most once.
-
- The following capabilities are defined in this document:
-
- IMPLEMENTATION - Name of implementation and version. This capability
- MUST always be returned by the server.
-
- SASL - List of SASL mechanisms supported by the server, each
- separated by a space. This list can be empty if and only if STARTTLS
- is also advertised. This means that the client must negotiate TLS
- encryption with STARTTLS first, at which point the SASL capability
- will list a non-empty list of SASL mechanisms.
-
- SIEVE - List of space-separated Sieve extensions (as listed in Sieve
- "require" action [SIEVE]) supported by the Sieve engine. This
- capability MUST always be returned by the server.
-
-
-
-
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-
- STARTTLS - If TLS [TLS] is supported by this implementation. Before
- advertising this capability a server MUST verify to the best of its
- ability that TLS can be successfully negotiated by a client with
- common cipher suites. Specifically, a server should verify that a
- server certificate has been installed and that the TLS subsystem has
- successfully initialized. This capability SHOULD NOT be advertised
- once STARTTLS or AUTHENTICATE command completes successfully. Client
- and server implementations MUST implement the STARTTLS extension.
-
- MAXREDIRECTS - Specifies the limit on the number of Sieve "redirect"
- actions a script can perform during a single evaluation. Note that
- this is different from the total number of "redirect" actions a
- script can contain. The value is a non-negative number represented
- as a ManageSieve string.
-
- NOTIFY - A space-separated list of URI schema parts for supported
- notification methods. This capability MUST be specified if the Sieve
- implementation supports the "enotify" extension [NOTIFY].
-
- LANGUAGE - The language (<Language-Tag> from [RFC5646]) currently
- used for human-readable error messages. If this capability is not
- returned, the "i-default" [RFC2277] language is assumed. Note that
- the current language MAY be per-user configurable (i.e., it MAY
- change after authentication).
-
- OWNER - The canonical name of the logged-in user (SASL "authorization
- identity") encoded in UTF-8. This capability MUST NOT be returned in
- unauthenticated state and SHOULD be returned once the AUTHENTICATE
- command succeeds.
-
- VERSION - This capability MUST be returned by servers compliant with
- this document or its successor. For servers compliant with this
- document, the capability value is the string "1.0". Lack of this
- capability means that the server predates this specification and thus
- doesn't support the following commands: RENAMESCRIPT, CHECKSCRIPT,
- and NOOP.
-
- Section 2.14 defines some additional ManageSieve extensions and their
- respective capabilities.
-
- A server implementation MUST return SIEVE, IMPLEMENTATION, and
- VERSION capabilities.
-
- A client implementation MUST ignore any listed capabilities that it
- does not understand.
-
-
-
-
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-
- Example:
-
- S: "IMPlemENTATION" "Example1 ManageSieved v001"
- S: "SASl" "DIGEST-MD5 GSSAPI"
- S: "SIeVE" "fileinto vacation"
- S: "StaRTTLS"
- S: "NOTIFY" "xmpp mailto"
- S: "MAXREdIRECTS" "5"
- S: "VERSION" "1.0"
- S: OK
-
- After successful authentication, this might look like this:
-
- Example:
-
- S: "IMPlemENTATION" "Example1 ManageSieved v001"
- S: "SASl" "DIGEST-MD5 GSSAPI"
- S: "SIeVE" "fileinto vacation"
- S: "NOTIFY" "xmpp mailto"
- S: "OWNER" "alexey@example.com"
- S: "MAXREdIRECTS" "5"
- S: "VERSION" "1.0"
- S: OK
-
-1.8. Transport
-
- The ManageSieve protocol assumes a reliable data stream such as that
- provided by TCP. When TCP is used, a ManageSieve server typically
- listens on port 4190.
-
- Before opening the TCP connection, the ManageSieve client first MUST
- resolve the Domain Name System (DNS) hostname associated with the
- receiving entity and determine the appropriate TCP port for
- communication with the receiving entity. The process is as follows:
-
- 1. Attempt to resolve the hostname using a [DNS-SRV] Service of
- "sieve" and a Proto of "tcp" for the target domain (e.g.,
- "example.net"), resulting in resource records such as
- "_sieve._tcp.example.net.". The result of the SRV lookup, if
- successful, will be one or more combinations of a port and
- hostname; the ManageSieve client MUST resolve the returned
- hostnames to IPv4/IPv6 addresses according to returned SRV record
- weight. IP addresses from the first successfully resolved
- hostname (with the corresponding port number returned by SRV
- lookup) are used to connect to the server. If connection using
- one of the IP addresses fails, the next resolved IP address is
-
-
-
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-
- used to connect. If connection to all resolved IP addresses
- fails, then the resolution/connect is repeated for the next
- hostname returned by SRV lookup.
-
- 2. If the SRV lookup fails, the fallback SHOULD be a normal IPv4 or
- IPv6 address record resolution to determine the IP address, where
- the port used is the default ManageSieve port of 4190.
-
-1.9. Conventions Used in This Document
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in [KEYWORDS].
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server respectively. Line breaks that do not start a new "C:" or
- "S:" exist for editorial reasons.
-
- Examples of authentication in this document are using DIGEST-MD5
- [DIGEST-MD5] and GSSAPI [GSSAPI] SASL mechanisms.
-
-2. Commands
-
- This section and its subsections describe valid ManageSieve commands.
- Upon initial connection to the server, the client's session is in
- non-authenticated state. Prior to successful authentication, only
- the AUTHENTICATE, CAPABILITY, STARTTLS, LOGOUT, and NOOP (see Section
- 2.13) commands are valid. ManageSieve extensions MAY define other
- commands that are valid in non-authenticated state. Servers MUST
- reject all other commands with a NO response. Clients may pipeline
- commands (send more than one command at a time without waiting for
- completion of the first command). However, a group of commands sent
- together MUST NOT have an AUTHENTICATE (*), a STARTTLS, or a
- HAVESPACE command anywhere but the last command in the list.
-
- (*) - The only exception to this rule is when the AUTHENTICATE
- command contains an initial response for a SASL mechanism that allows
- clients to send data first, the mechanism is known to complete in one
- round trip, and the mechanism doesn't negotiate a SASL security
- layer. Two examples of such SASL mechanisms are PLAIN [PLAIN] and
- EXTERNAL [SASL].
-
-
-
-
-
-
-
-
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-
-2.1. AUTHENTICATE Command
-
- Arguments: String - mechanism
- String - initial data (optional)
-
- The AUTHENTICATE command indicates a SASL [SASL] authentication
- mechanism to the server. If the server supports the requested
- authentication mechanism, it performs an authentication protocol
- exchange to identify and authenticate the user. Optionally, it also
- negotiates a security layer for subsequent protocol interactions. If
- the requested authentication mechanism is not supported, the server
- rejects the AUTHENTICATE command by sending the NO response.
-
- The authentication protocol exchange consists of a series of server
- challenges and client responses that are specific to the selected
- authentication mechanism. A server challenge consists of a string
- (quoted or literal) followed by a CRLF. The contents of the string
- is a base-64 encoding [BASE64] of the SASL data. A client response
- consists of a string (quoted or literal) with the base-64 encoding of
- the SASL data followed by a CRLF. If the client wishes to cancel the
- authentication exchange, it issues a string containing a single "*".
- If the server receives such a response, it MUST reject the
- AUTHENTICATE command by sending a NO reply.
-
- Note that an empty challenge/response is sent as an empty string. If
- the mechanism dictates that the final response is sent by the server,
- this data MAY be placed within the data portion of the SASL response
- code to save a round trip.
-
- The optional initial-response argument to the AUTHENTICATE command is
- used to save a round trip when using authentication mechanisms that
- are defined to send no data in the initial challenge. When the
- initial-response argument is used with such a mechanism, the initial
- empty challenge is not sent to the client and the server uses the
- data in the initial-response argument as if it were sent in response
- to the empty challenge. If the initial-response argument to the
- AUTHENTICATE command is used with a mechanism that sends data in the
- initial challenge, the server MUST reject the AUTHENTICATE command by
- sending the NO response.
-
- The service name specified by this protocol's profile of SASL is
- "sieve".
-
- Reauthentication is not supported by ManageSieve protocol's profile
- of SASL. That is, after a successfully completed AUTHENTICATE
- command, no more AUTHENTICATE commands may be issued in the same
- session. After a successful AUTHENTICATE command completes, a server
- MUST reject any further AUTHENTICATE commands with a NO reply.
-
-
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-
- However, note that a server may implement the UNAUTHENTICATE
- extension described in Section 2.14.1.
-
- If a security layer is negotiated through the SASL authentication
- exchange, it takes effect immediately following the CRLF that
- concludes the successful authentication exchange for the client, and
- the CRLF of the OK response for the server.
-
- When a security layer takes effect, the ManageSieve protocol is reset
- to the initial state (the state in ManageSieve after a client has
- connected to the server). The server MUST discard any knowledge
- obtained from the client that was not obtained from the SASL (or TLS)
- negotiation itself. Likewise, the client MUST discard any knowledge
- obtained from the server, such as the list of ManageSieve extensions,
- that was not obtained from the SASL (and/or TLS) negotiation itself.
- (Note that a client MAY compare the advertised SASL mechanisms before
- and after authentication in order to detect an active down-
- negotiation attack. See below.)
-
- Once a SASL security layer is established, the server MUST re-issue
- the capability results, followed by an OK response. This is
- necessary to protect against man-in-the-middle attacks that alter the
- capabilities list prior to SASL negotiation. The capability results
- MUST include all SASL mechanisms the server was capable of
- negotiating with that client. This is done in order to allow the
- client to detect an active down-negotiation attack. If a user-
- oriented client detects such a down-negotiation attack, it SHOULD
- either notify the user (it MAY give the user the opportunity to
- continue with the ManageSieve session in this case) or close the
- transport connection and indicate that a down-negotiation attack
- might be in progress. If an automated client detects a down-
- negotiation attack, it SHOULD return or log an error indicating that
- a possible attack might be in progress and/or SHOULD close the
- transport connection.
-
- When both [TLS] and SASL security layers are in effect, the TLS
- encoding MUST be applied (when sending data) after the SASL encoding.
-
- Server implementations SHOULD support SASL proxy authentication so
- that an administrator can administer a user's scripts. Proxy
- authentication is when a user authenticates as herself/himself but
- requests the server to act (authorize) as another user.
-
- The authorization identity generated by this [SASL] exchange is a
- "simple username" (in the sense defined in [SASLprep]), and both
- client and server MUST use the [SASLprep] profile of the [StringPrep]
- algorithm to prepare these names for transmission or comparison. If
- preparation of the authorization identity fails or results in an
-
-
-
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-RFC 5804 ManageSieve July 2010
-
-
- empty string (unless it was transmitted as the empty string), the
- server MUST fail the authentication.
-
- If an AUTHENTICATE command fails with a NO response, the client MAY
- try another authentication mechanism by issuing another AUTHENTICATE
- command. In other words, the client may request authentication types
- in decreasing order of preference.
-
- Note that a failed (NO) response to the AUTHENTICATE command may
- contain one of the following response codes: AUTH-TOO-WEAK, ENCRYPT-
- NEEDED, or TRANSITION-NEEDED. See Section 1.3 for detailed
- description of the relevant conditions.
-
- To ensure interoperability, both client and server implementations of
- the ManageSieve protocol MUST implement the SCRAM-SHA-1 [SCRAM] SASL
- mechanism, as well as [PLAIN] over [TLS].
-
- Note: use of PLAIN over TLS reflects current use of PLAIN over TLS in
- other email-related protocols; however, a longer-term goal is to
- migrate email-related protocols from using PLAIN over TLS to SCRAM-
- SHA-1 mechanism.
-
- Examples (Note that long lines are folded for readability and are not
- part of protocol exchange):
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: "VERSION" "1.0"
- S: OK
- C: Authenticate "DIGEST-MD5"
- S: "cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
- 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
- cyxjaGFyc2V0PXV0Zi04"
- C: "Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
- QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
- aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
- N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
- ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
- A9YXV0aA=="
- S: OK (SASL "cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZ
- mZmZA==")
-
-
-
-
-
-
-
-
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-
-
- A slightly different variant of the same authentication exchange is:
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "VERSION" "1.0"
- S: "STARTTLS"
- S: OK
- C: Authenticate "DIGEST-MD5"
- S: {136}
- S: cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
- 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
- cyxjaGFyc2V0PXV0Zi04
- C: {300+}
- C: Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
- QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
- aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
- N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
- ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
- A9YXV0aA==
- S: {56}
- S: cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
- C: ""
- S: OK
-
-
-
-
-
-
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-
-
- Another example demonstrating use of SASL PLAIN mechanism under TLS
- follows. This example also demonstrate use of SASL "initial
- response" (the second parameter to the Authenticate command):
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" ""
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: OK
- C: STARTTLS
- S: OK
- <TLS negotiation, further commands are under TLS layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN"
- S: "SIEVE" "fileinto vacation"
- S: OK
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xu"
- S: NO
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xz"
- S: NO
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xy"
- S: BYE "Too many failed authentication attempts"
- <Server closes connection>
-
-
-
-
-
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-
- The following example demonstrates use of SASL "initial response".
- It also demonstrates that an empty response can be sent as a literal
- and that negotiating a SASL security layer results in the server
- re-issuing server capabilities:
-
- C: AUTHENTICATE "GSSAPI" {1488+}
- C: YIIE[...1480 octets here ...]dA==
- S: {208}
- S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKic
- [...114 octets here ...]
- /yzpAy9p+Y0LanLskOTvMc0MnjgAa4YEr3eJ6
- C: {0+}
- C:
- S: {44}
- S: BQQF/wAMAAwAAAAAYRGFAo6W0vIHti8i1UXODgEAEAA=
- C: {44+}
- C: BQQE/wAMAAwAAAAAIsT1iv9UkZApw471iXt6cwEAAAE=
- S: OK
- <Further commands/responses are under SASL security layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "LANGUAGE" "ru"
- S: "MAXREDIRECTS" "3"
- S: ok
-
-2.1.1. Use of SASL PLAIN Mechanism over TLS
-
- This section is normative for ManageSieve client implementations that
- support SASL [PLAIN] over [TLS].
-
- If a ManageSieve client is willing to use SASL PLAIN over TLS to
- authenticate to the ManageSieve server, the client MUST verify the
- server identity (see Section 2.2.1). If the server identity can't be
- verified (e.g., the server has not provided any certificate, or if
- the certificate verification fails), the client MUST NOT attempt to
- authenticate using the SASL PLAIN mechanism.
-
-2.2. STARTTLS Command
-
- Support for STARTTLS command in servers is optional. Its
- availability is advertised with "STARTTLS" capability as described in
- Section 1.7.
-
- The STARTTLS command requests commencement of a TLS [TLS]
- negotiation. The negotiation begins immediately after the CRLF in
- the OK response. After a client issues a STARTTLS command, it MUST
-
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-
- NOT issue further commands until a server response is seen and the
- TLS negotiation is complete.
-
- The STARTTLS command is only valid in non-authenticated state. The
- server remains in non-authenticated state, even if client credentials
- are supplied during the TLS negotiation. The SASL [SASL] EXTERNAL
- mechanism MAY be used to authenticate once TLS client credentials are
- successfully exchanged, but servers supporting the STARTTLS command
- are not required to support the EXTERNAL mechanism.
-
- After the TLS layer is established, the server MUST re-issue the
- capability results, followed by an OK response. This is necessary to
- protect against man-in-the-middle attacks that alter the capabilities
- list prior to STARTTLS. This capability result MUST NOT include the
- STARTTLS capability.
-
- The client MUST discard cached capability information and replace it
- with the new information. The server MAY advertise different
- capabilities after STARTTLS.
-
- Example:
-
- C: StartTls
- S: oK
- <TLS negotiation, further commands are under TLS layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "VERSION" "1.0"
- S: "LANGUAGE" "fr"
- S: ok
-
-2.2.1. Server Identity Check
-
- During the TLS negotiation, the ManageSieve client MUST check its
- understanding of the server hostname/IP address against the server's
- identity as presented in the server Certificate message, in order to
- prevent man-in-the-middle attacks. In this section, the client's
- understanding of the server's identity is called the "reference
- identity".
-
- Checking is performed according to the following rules:
-
- o If the reference identity is a hostname:
-
- 1. If a subjectAltName extension of the SRVName [X509-SRV],
- dNSName [X509] (in that order of preference) type is present
- in the server's certificate, then it SHOULD be used as the
-
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-
- source of the server's identity. Matching is performed as
- described in Section 2.2.1.1, with the exception that no
- wildcard matching is allowed for SRVName type. If the
- certificate contains multiple names (e.g., more than one
- dNSName field), then a match with any one of the fields is
- considered acceptable.
-
- 2. The client MAY use other types of subjectAltName for
- performing comparison.
-
- 3. The server's identity MAY also be verified by comparing the
- reference identity to the Common Name (CN) [RFC4519] value in
- the leaf Relative Distinguished Name (RDN) of the subjectName
- field of the server's certificate. This comparison is
- performed using the rules for comparison of DNS names in
- Section 2.2.1.1, below. Although the use of the Common Name
- value is existing practice, it is deprecated, and
- Certification Authorities are encouraged to provide
- subjectAltName values instead. Note that the TLS
- implementation may represent DNs in certificates according to
- X.500 or other conventions. For example, some X.500
- implementations order the RDNs in a DN using a left-to-right
- (most significant to least significant) convention instead of
- LDAP's right-to-left convention.
-
- o When the reference identity is an IP address, the iPAddress
- subjectAltName SHOULD be used by the client for comparison. The
- comparison is performed as described in Section 2.2.1.2.
-
- If the server identity check fails, user-oriented clients SHOULD
- either notify the user (clients MAY give the user the opportunity to
- continue with the ManageSieve session in this case) or close the
- transport connection and indicate that the server's identity is
- suspect. Automated clients SHOULD return or log an error indicating
- that the server's identity is suspect and/or SHOULD close the
- transport connection. Automated clients MAY provide a configuration
- setting that disables this check, but MUST provide a setting that
- enables it.
-
- Beyond the server identity check described in this section, clients
- should be prepared to do further checking to ensure that the server
- is authorized to provide the service it is requested to provide. The
- client may need to make use of local policy information in making
- this determination.
-
-
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-
-2.2.1.1. Comparison of DNS Names
-
- If the reference identity is an internationalized domain name,
- conforming implementations MUST convert it to the ASCII Compatible
- Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
- before comparison with subjectAltName values of type dNSName.
- Specifically, conforming implementations MUST perform the conversion
- operation specified in Section 4 of [RFC3490] as follows:
-
- o in step 1, the domain name SHALL be considered a "stored string";
-
- o in step 3, set the flag called "UseSTD3ASCIIRules";
-
- o in step 4, process each label with the "ToASCII" operation; and
-
- o in step 5, change all label separators to U+002E (full stop).
-
- After performing the "to-ASCII" conversion, the DNS labels and names
- MUST be compared for equality according to the rules specified in
- Section 3 of [RFC3490]; i.e., once all label separators are replaced
- with U+002E (dot) they are compared in the case-insensitive manner.
-
- The '*' (ASCII 42) wildcard character is allowed in subjectAltName
- values of type dNSName, and then only as the left-most (least
- significant) DNS label in that value. This wildcard matches any
- left-most DNS label in the server name. That is, the subject
- *.example.com matches the server names a.example.com and
- b.example.com, but does not match example.com or a.b.example.com.
-
-2.2.1.2. Comparison of IP Addresses
-
- When the reference identity is an IP address, the identity MUST be
- converted to the "network byte order" octet string representation
- [RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the
- octet string will contain exactly four octets. For IP Version 6, as
- specified in RFC 2460, the octet string will contain exactly sixteen
- octets. This octet string is then compared against subjectAltName
- values of type iPAddress. A match occurs if the reference identity
- octet string and value octet strings are identical.
-
-2.2.1.3. Comparison of Other subjectName Types
-
- Client implementations MAY support matching against subjectAltName
- values of other types as described in other documents.
-
-
-
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-
-2.3. LOGOUT Command
-
- The client sends the LOGOUT command when it is finished with a
- connection and wishes to terminate it. The server MUST reply with an
- OK response. The server MUST ignore commands issued by the client
- after the LOGOUT command.
-
- The client SHOULD wait for the OK response before closing the
- connection. This avoids the TCP connection going into the TIME_WAIT
- state on the server. In order to avoid going into the TIME_WAIT TCP
- state, the server MAY wait for a short while for the client to close
- the TCP connection first. Whether or not the server waits for the
- client to close the connection, it MUST then close the connection
- itself.
-
- Example:
-
- C: Logout
- S: Ok
- <connection is terminated>
-
-2.4. CAPABILITY Command
-
- The CAPABILITY command requests the server capabilities as described
- earlier in this document. It has no parameters.
-
- Example:
-
- C: CAPABILITY
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN SCRAM-SHA-1 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: OK
-
-2.5. HAVESPACE Command
-
- Arguments: String - name
- Number - script size
-
- The HAVESPACE command is used to query the server for available
- space. Clients specify the name they wish to save the script as and
- its size in octets. Both parameters can be used by the server to see
- if the script with the specified name and size is within a user's
- quota(s). For example, the server MAY use the script name to check
- if a script would be replaced or a new one would be created. Servers
- respond with a NO if storing a script with that name and size would
-
-
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-
- fail or OK otherwise. Clients SHOULD issue this command before
- attempting to place a script on the server.
-
- Note that the OK response from the HAVESPACE command does not
- constitute a guarantee of success as server disk space conditions
- could change between the client issuing the HAVESPACE and the client
- issuing the PUTSCRIPT commands. A QUOTA response code (see
- Section 1.3) remains a possible (albeit unlikely) response to a
- subsequent PUTSCRIPT with the same name and size.
-
- Example:
-
- C: HAVESPACE "myscript" 999999
- S: NO (QUOTA/MAXSIZE) "Quota exceeded"
-
- C: HAVESPACE "foobar" 435
- S: OK
-
-2.6. PUTSCRIPT Command
-
- Arguments: String - Script name
- String - Script content
-
- The PUTSCRIPT command is used by the client to submit a Sieve script
- to the server.
-
- If the script already exists, upon success the old script will be
- overwritten. The old script MUST NOT be overwritten if PUTSCRIPT
- fails in any way. A script of zero length SHOULD be disallowed.
-
- This command places the script on the server. It does not affect
- whether the script is processed on incoming mail, unless it replaces
- the script that is already active. The SETACTIVE command is used to
- mark a script as active.
-
- When submitting large scripts, clients SHOULD use the HAVESPACE
- command beforehand to query if the server is willing to accept a
- script of that size.
-
- The server MUST check the submitted script for validity, which
- includes checking that the script complies with the Sieve grammar
- [SIEVE] and that all Sieve extensions mentioned in the script's
- "require" statement(s) are supported by the Sieve interpreter. (Note
- that if the Sieve interpreter supports the Sieve "ihave" extension
- [I-HAVE], any unrecognized/unsupported extension mentioned in the
- "ihave" test MUST NOT cause the validation failure.) Other checks
- such as validating the supplied command arguments for each command
- MAY be performed. Essentially, the performed validation SHOULD be
-
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-
- the same as performed when compiling the script for execution.
- Implementations that use a binary representation to store compiled
- scripts can extend the validation to a full compilation, in order to
- avoid validating uploaded scripts multiple times.
-
- If the script fails the validation, the server MUST reply with a NO
- response. Any script that fails the validity test MUST NOT be stored
- on the server. The message given with a NO response MUST be human
- readable and SHOULD contain a specific error message giving the line
- number of the first error. Implementors should strive to produce
- helpful error messages similar to those given by programming language
- compilers. Client implementations should note that this may be a
- multiline literal string with more than one error message separated
- by CRLFs. The human-readable message is in the language returned in
- the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
- encoded in UTF-8 [UTF-8].
-
- An OK response MAY contain the WARNINGS response code. In such a
- case the human-readable message that follows the OK response SHOULD
- contain a specific warning message (or messages) giving the line
- number(s) in the script that might contain errors not intended by the
- script writer. The human-readable message is in the language
- returned in the latest LANGUAGE capability (or in "i-default"; see
- Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
- response code SHOULD present the message to the user.
-
-
-
-
-
-
-
-
-
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-
-
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-
- Examples:
-
- C: Putscript "foo" {31+}
- C: #comment
- C: InvalidSieveCommand
- C:
- S: NO "line 2: Syntax error"
-
- C: Putscript "mysievescript" {110+}
- C: require ["fileinto"];
- C:
- C: if envelope :contains "to" "tmartin+sent" {
- C: fileinto "INBOX.sent";
- C: }
- S: OK
-
- C: Putscript "myforwards" {190+}
- C: redirect "111@example.net";
- C:
- C: if size :under 10k {
- C: redirect "mobile@cell.example.com";
- C: }
- C:
- C: if envelope :contains "to" "tmartin+lists" {
- C: redirect "lists@groups.example.com";
- C: }
- S: OK (WARNINGS) "line 8: server redirect action
- limit is 2, this redirect might be ignored"
-
-2.7. LISTSCRIPTS Command
-
- This command lists the scripts the user has on the server. Upon
- success, a list of CRLF-separated script names (each represented as a
- quoted or literal string) is returned followed by an OK response. If
- there exists an active script, the atom ACTIVE is appended to the
- corresponding script name. The atom ACTIVE MUST NOT appear on more
- than one response line.
-
-
-
-
-
-
-
-
-
-
-
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-
- Example:
-
- C: Listscripts
- S: "summer_script"
- S: "vacation_script"
- S: {13}
- S: clever"script
- S: "main_script" ACTIVE
- S: OK
-
- C: listscripts
- S: "summer_script"
- S: "main_script" active
- S: OK
-
-2.8. SETACTIVE Command
-
- Arguments: String - script name
-
- This command sets a script active. If the script name is the empty
- string (i.e., ""), then any active script is disabled. Disabling an
- active script when there is no script active is not an error and MUST
- result in an OK reply.
-
- If the script does not exist on the server, then the server MUST
- reply with a NO response. Such a reply SHOULD contain the
- NONEXISTENT response code.
-
- Examples:
-
- C: Setactive "vacationscript"
- S: Ok
-
- C: Setactive ""
- S: Ok
-
- C: Setactive "baz"
- S: No (NONEXISTENT) "There is no script by that name"
-
- C: Setactive "baz"
- S: No (NONEXISTENT) {31}
- S: There is no script by that name
-
-
-
-
-
-
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-
-2.9. GETSCRIPT Command
-
- Arguments: String - script name
-
- This command gets the contents of the specified script. If the
- script does not exist, the server MUST reply with a NO response.
- Such a reply SHOULD contain the NONEXISTENT response code.
-
- Upon success, a string with the contents of the script is returned
- followed by an OK response.
-
- Example:
-
- C: Getscript "myscript"
- S: {54}
- S: #this is my wonderful script
- S: reject "I reject all";
- S:
- S: OK
-
-2.10. DELETESCRIPT Command
-
- Arguments: String - script name
-
- This command is used to delete a user's Sieve script. Servers MUST
- reply with a NO response if the script does not exist. Such
- responses SHOULD include the NONEXISTENT response code.
-
- The server MUST NOT allow the client to delete an active script, so
- the server MUST reply with a NO response if attempted. Such a
- response SHOULD contain the ACTIVE response code. If a client wishes
- to delete an active script, it should use the SETACTIVE command to
- disable the script first.
-
- Example:
-
- C: Deletescript "foo"
- S: Ok
-
- C: Deletescript "baz"
- S: No (ACTIVE) "You may not delete an active script"
-
-
-
-
-
-
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-
-2.11. RENAMESCRIPT Command
-
- Arguments: String - Old Script name
- String - New Script name
-
- This command is used to rename a user's Sieve script. Servers MUST
- reply with a NO response if the old script does not exist (in which
- case the NONEXISTENT response code SHOULD be included), or a script
- with the new name already exists (in which case the ALREADYEXISTS
- response code SHOULD be included). Renaming the active script is
- allowed; the renamed script remains active.
-
- Example:
-
- C: Renamescript "foo" "bar"
- S: Ok
-
- C: Renamescript "baz" "bar"
- S: No "bar already exists"
-
- If the server doesn't support the RENAMESCRIPT command, the client
- can emulate it by performing the following steps:
-
- 1. List available scripts with LISTSCRIPTS. If the script with the
- new script name exists, then the client should ask the user
- whether to abort the operation, to replace the script (by issuing
- the DELETESCRIPT <newname> after that), or to choose a different
- name.
-
- 2. Download the old script with GETSCRIPT <oldname>.
-
- 3. Upload the old script with the new name: PUTSCRIPT <newname>.
-
- 4. If the old script was active (as reported by LISTSCRIPTS in step
- 1), then make the new script active: SETACTIVE <newname>.
-
- 5. Delete the old script: DELETESCRIPT <oldname>.
-
- Note that these steps don't describe how to handle various other
- error conditions (for example, NO response containing QUOTA response
- code in step 3). Error handling is left as an exercise for the
- reader.
-
-
-
-
-
-
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-
-2.12. CHECKSCRIPT Command
-
- Arguments: String - Script content
-
- The CHECKSCRIPT command is used by the client to verify Sieve script
- validity without storing the script on the server.
-
- The server MUST check the submitted script for syntactic validity,
- which includes checking that all Sieve extensions mentioned in Sieve
- script "require" statement(s) are supported by the Sieve interpreter.
- (Note that if the Sieve interpreter supports the Sieve "ihave"
- extension [I-HAVE], any unrecognized/unsupported extension mentioned
- in the "ihave" test MUST NOT cause the syntactic validation failure.)
- If the script fails this test, the server MUST reply with a NO
- response. The message given with a NO response MUST be human
- readable and SHOULD contain a specific error message giving the line
- number of the first error. Implementors should strive to produce
- helpful error messages similar to those given by programming language
- compilers. Client implementations should note that this may be a
- multiline literal string with more than one error message separated
- by CRLFs. The human-readable message is in the language returned in
- the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
- encoded in UTF-8 [UTF-8].
-
- Examples:
-
- C: CheckScript {31+}
- C: #comment
- C: InvalidSieveCommand
- C:
- S: NO "line 2: Syntax error"
-
- A ManageSieve server supporting this command MUST NOT check if the
- script will put the current user over its quota limit.
-
- An OK response MAY contain the WARNINGS response code. In such a
- case, the human-readable message that follows the OK response SHOULD
- contain a specific warning message (or messages) giving the line
- number(s) in the script that might contain errors not intended by the
- script writer. The human-readable message is in the language
- returned in the latest LANGUAGE capability (or in "i-default"; see
- Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
- response code SHOULD present the message to the user.
-
-
-
-
-
-
-
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-
-2.13. NOOP Command
-
- Arguments: String - tag to echo back (optional)
-
- The NOOP command does nothing, beyond returning a response to the
- client. It may be used by clients for protocol re-synchronization or
- to reset any inactivity auto-logout timer on the server.
-
- The response to the NOOP command is always OK, followed by the TAG
- response code together with the supplied string. If no string was
- supplied in the NOOP command, the TAG response code MUST NOT be
- included.
-
- Examples:
-
- C: NOOP
- S: OK "NOOP completed"
-
- C: NOOP "STARTTLS-SYNC-42"
- S: OK (TAG {16}
- S: STARTTLS-SYNC-42) "Done"
-
-2.14. Recommended Extensions
-
- The UNAUTHENTICATE extension (advertised as the "UNAUTHENTICATE"
- capability with no parameters) defines a new UNAUTHENTICATE command,
- which allows a client to return the server to non-authenticated
- state. Support for this extension is RECOMMENDED.
-
-2.14.1. UNAUTHENTICATE Command
-
- The UNAUTHENTICATE command returns the server to the
- non-authenticated state. It doesn't affect any previously
- established TLS [TLS] or SASL (Section 2.1) security layer.
-
- The UNAUTHENTICATE command is only valid in authenticated state. If
- issued in a wrong state, the server MUST reject it with a NO
- response.
-
- The UNAUTHENTICATE command has no parameters.
-
- When issued in the authenticated state, the UNAUTHENTICATE command
- MUST NOT fail (i.e., it must never return anything other than OK or
- BYE).
-
-
-
-
-
-
-
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-
-
-3. Sieve URL Scheme
-
- URI scheme name: sieve
-
- Status: permanent
-
- URI scheme syntax: Described using ABNF [ABNF]. Some ABNF
- productions not defined below are from [URI-GEN].
-
- sieveurl = sieveurl-server / sieveurl-list-scripts /
- sieveurl-script
-
- sieveurl-server = "sieve://" authority
-
- sieveurl-list-scripts = "sieve://" authority ["/"]
-
- sieveurl-script = "sieve://" authority "/"
- [owner "/"] scriptname
-
- authority = <defined in [URI-GEN]>
-
- owner = *ochar
- ;; %-encoded version of [SASL] authorization
- ;; identity (script owner) or "userid".
- ;;
- ;; Empty owner is used to reference
- ;; global scripts.
- ;;
- ;; Note that ASCII characters such as " ", ";",
- ;; "&", "=", "/" and "?" must be %-encoded
- ;; as per rule specified in [URI-GEN].
-
- scriptname = 1*ochar
- ;; %-encoded version of UTF-8 representation
- ;; of the script name.
- ;; Note that ASCII characters such as " ", ";",
- ;; "&", "=", "/" and "?" must be %-encoded
- ;; as per rule specified in [URI-GEN].
-
- ochar = unreserved / pct-encoded / sub-delims-sh /
- ":" / "@"
- ;; Same as [URI-GEN] 'pchar',
- ;; but without ";", "&" and "=".
-
- unreserved = <defined in [URI-GEN]>
-
- pct-encoded = <defined in [URI-GEN]>
-
-
-
-
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-
-
- sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
- "*" / "+" / ","
- ;; Same as [URI-GEN] sub-delims,
- ;; but without ";", "&" and "=".
-
- URI scheme semantics:
-
- A Sieve URL identifies a Sieve server or a Sieve script on a Sieve
- server. The latter form is associated with the application/sieve
- MIME type defined in [SIEVE]. There is no MIME type associated
- with the former form of Sieve URI.
-
- The server form is used in the REFERRAL response code (see Section
- 1.3) in order to designate another server where the client should
- perform its operations.
-
- The script form allows to retrieve (GETSCRIPT), update
- (PUTSCRIPT), delete (DELETESCRIPT), or activate (SETACTIVE) the
- named script; however, the most typical action would be to
- retrieve the script. If the script name is empty (omitted), the
- URI requests that the client lists available scripts using the
- LISTSCRIPTS command.
-
- Encoding considerations:
-
- The script name and/or the owner, if present, is in UTF-8. Non--
- US-ASCII UTF-8 octets MUST be percent-encoded as described in
- [URI-GEN]. US-ASCII characters such as " " (space), ";", "&",
- "=", "/" and "?" MUST be %-encoded as described in [URI-GEN].
- Note that "&" and "?" are in this list in order to allow for
- future extensions.
-
- Note that the empty owner (e.g., sieve://example.com//script) is
- different from the missing owner (e.g.,
- sieve://example.com/script) and is reserved for referencing global
- scripts.
-
- The user name (in the "authority" part), if present, is in UTF-8.
- Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
- [URI-GEN].
-
- Applications/protocols that use this URI scheme name:
- ManageSieve [RFC5804] clients and servers. Clients that can store
- user preferences in protocols such as [LDAP] or [ACAP].
-
- Interoperability considerations: None.
-
-
-
-
-
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-
-
- Security considerations:
- The <scriptname> part of a ManageSieve URL might potentially disclose
- some confidential information about the author of the script or,
- depending on a ManageSieve implementation, about configuration of the
- mail system. The latter might be used to prepare for a more complex
- attack on the mail system.
-
- Clients resolving ManageSieve URLs that wish to achieve data
- confidentiality and/or integrity SHOULD use the STARTTLS command (if
- supported by the server) before starting authentication, or use a
- SASL mechanism, such as GSSAPI, that provides a confidentiality
- security layer.
-
- Contact: Alexey Melnikov <alexey.melnikov@isode.com>
-
- Author/Change controller: IESG.
-
- References: This document and RFC 5228 [SIEVE].
-
-4. Formal Syntax
-
- The following syntax specification uses the Augmented Backus-Naur
- Form (BNF) notation as specified in [ABNF]. This uses the ABNF core
- rules as specified in Appendix A of the ABNF specification [ABNF].
- "UTF8-2", "UTF8-3", and "UTF8-4" non-terminal are defined in [UTF-8].
-
- Except as noted otherwise, all alphabetic characters are case-
- insensitive. The use of upper- or lowercase characters to define
- token strings is for editorial clarity only. Implementations MUST
- accept these strings in a case-insensitive fashion.
-
- SAFE-CHAR = %x01-09 / %x0B-0C / %x0E-21 / %x23-5B /
- %x5D-7F
- ;; any TEXT-CHAR except QUOTED-SPECIALS
-
- QUOTED-CHAR = SAFE-UTF8-CHAR / "\" QUOTED-SPECIALS
-
- QUOTED-SPECIALS = DQUOTE / "\"
-
- SAFE-UTF8-CHAR = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4
- ;; <UTF8-2>, <UTF8-3>, and <UTF8-4>
- ;; are defined in [UTF-8].
-
- ATOM-CHAR = "!" / %x23-27 / %x2A-5B / %x5D-7A / %x7C-7E
- ;; Any CHAR except ATOM-SPECIALS
-
- ATOM-SPECIALS = "(" / ")" / "{" / SP / CTL / QUOTED-SPECIALS
-
-
-
-
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-
-
- NZDIGIT = %x31-39
- ;; 1-9
-
- atom = 1*1024ATOM-CHAR
-
- iana-token = atom
- ;; MUST be registered with IANA
-
- auth-type = DQUOTE auth-type-name DQUOTE
-
- auth-type-name = iana-token
- ;; as defined in SASL [SASL]
-
- command = (command-any / command-auth /
- command-nonauth) CRLF
- ;; Modal based on state
-
- command-any = command-capability / command-logout /
- command-noop
- ;; Valid in all states
-
- command-auth = command-getscript / command-setactive /
- command-listscripts / command-deletescript /
- command-putscript / command-checkscript /
- command-havespace /
- command-renamescript /
- command-unauthenticate
- ;; Valid only in Authenticated state
-
- command-nonauth = command-authenticate / command-starttls
- ;; Valid only when in Non-Authenticated
- ;; state
-
- command-authenticate = "AUTHENTICATE" SP auth-type [SP string]
- *(CRLF string)
-
- command-capability = "CAPABILITY"
-
- command-deletescript = "DELETESCRIPT" SP sieve-name
-
- command-getscript = "GETSCRIPT" SP sieve-name
-
- command-havespace = "HAVESPACE" SP sieve-name SP number
-
- command-listscripts = "LISTSCRIPTS"
-
- command-noop = "NOOP" [SP string]
-
-
-
-
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-
-
- command-logout = "LOGOUT"
-
- command-putscript = "PUTSCRIPT" SP sieve-name SP sieve-script
-
- command-checkscript = "CHECKSCRIPT" SP sieve-script
-
- sieve-script = string
-
- command-renamescript = "RENAMESCRIPT" SP old-sieve-name SP
- new-sieve-name
-
- old-sieve-name = sieve-name
-
- new-sieve-name = sieve-name
-
- command-setactive = "SETACTIVE" SP active-sieve-name
-
- command-starttls = "STARTTLS"
-
- command-unauthenticate= "UNAUTHENTICATE"
-
- extend-token = atom
- ;; MUST be defined by a Standards Track or
- ;; IESG-approved experimental protocol
- ;; extension
-
- extension-data = extension-item *(SP extension-item)
-
- extension-item = extend-token / string / number /
- "(" [extension-data] ")"
-
- literal-c2s = "{" number "+}" CRLF *OCTET
- ;; The number represents the number of
- ;; octets.
- ;; This type of literal can only be sent
- ;; from the client to the server.
-
- literal-s2c = "{" number "}" CRLF *OCTET
- ;; Almost identical to literal-c2s,
- ;; but with no '+' character.
- ;; The number represents the number of
- ;; octets.
- ;; This type of literal can only be sent
- ;; from the server to the client.
-
-
-
-
-
-
-
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-
-
- number = (NZDIGIT *DIGIT) / "0"
- ;; A 32-bit unsigned number
- ;; with no extra leading zeros.
- ;; (0 <= n < 4,294,967,296)
-
- number-str = string
- ;; <number> encoded as a <string>.
-
- quoted = DQUOTE *1024QUOTED-CHAR DQUOTE
- ;; limited to 1024 octets between the <">s
-
- resp-code = "AUTH-TOO-WEAK" / "ENCRYPT-NEEDED" / "QUOTA"
- ["/" ("MAXSCRIPTS" / "MAXSIZE")] /
- resp-code-sasl /
- resp-code-referral /
- "TRANSITION-NEEDED" / "TRYLATER" /
- "ACTIVE" / "NONEXISTENT" /
- "ALREADYEXISTS" / "WARNINGS" /
- "TAG" SP string /
- resp-code-ext
-
- resp-code-referral = "REFERRAL" SP sieveurl
-
- resp-code-sasl = "SASL" SP string
-
- resp-code-name = iana-token
- ;; The response code name is hierarchical,
- ;; separated by '/'.
- ;; The response code name MUST NOT start
- ;; with '/'.
-
- resp-code-ext = resp-code-name [SP extension-data]
- ;; unknown response codes MUST be tolerated
- ;; by the client.
-
- response = response-authenticate /
- response-logout /
- response-getscript /
- response-setactive /
- response-listscripts /
- response-deletescript /
- response-putscript /
- response-checkscript /
- response-capability /
- response-havespace /
- response-starttls /
- response-renamescript /
- response-noop /
-
-
-
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-
-
- response-unauthenticate
-
- response-authenticate = *(string CRLF)
- ((response-ok [response-capability]) /
- response-nobye)
- ;; <response-capability> is REQUIRED if a
- ;; SASL security layer was negotiated and
- ;; MUST be omitted otherwise.
-
- response-capability = *(single-capability) response-oknobye
-
- single-capability = capability-name [SP string] CRLF
-
- capability-name = string
-
- ;; Note that literal-s2c is allowed.
-
- initial-capabilities = DQUOTE "IMPLEMENTATION" DQUOTE SP string /
- DQUOTE "SASL" DQUOTE SP sasl-mechs /
- DQUOTE "SIEVE" DQUOTE SP sieve-extensions /
- DQUOTE "MAXREDIRECTS" DQUOTE SP number-str /
- DQUOTE "NOTIFY" DQUOTE SP notify-mechs /
- DQUOTE "STARTTLS" DQUOTE /
- DQUOTE "LANGUAGE" DQUOTE SP language /
- DQUOTE "VERSION" DQUOTE SP version /
- DQUOTE "OWNER" DQUOTE SP string
- ;; Each capability conforms to
- ;; the syntax for single-capability.
- ;; Also, note that the capability name
- ;; can be returned as either literal-s2c
- ;; or quoted, even though only "quoted"
- ;; string is shown above.
-
- version = ( DQUOTE "1.0" DQUOTE ) / version-ext
-
- version-ext = DQUOTE ver-major "." ver-minor DQUOTE
- ; Future versions specified in updates
- ; to this document. An increment to
- ; the ver-major means a backward-incompatible
- ; change to the protocol, e.g., "3.5" (ver-major "3")
- ; is not backward-compatible with any "2.X" version.
- ; Any version "Z.W" MUST be backward compatible
- ; with any version "Z.Q", where Q < W.
- ; For example, version "2.4" is backward compatible
- ; with version "2.0", "2.1", "2.2", and "2.3".
-
- ver-major = number
-
-
-
-
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-
-
- ver-minor = number
-
- sasl-mechs = string
- ; Space-separated list of SASL mechanisms,
- ; each SASL mechanism name complies with rules
- ; specified in [SASL].
- ; Can be empty.
-
- sieve-extensions = string
- ; Space-separated list of supported SIEVE extensions.
- ; Can be empty.
-
- language = string
- ; Contains <Language-Tag> from [RFC5646].
-
-
- notify-mechs = string
- ; Space-separated list of URI schema parts
- ; for supported notification [NOTIFY] methods.
- ; MUST NOT be empty.
-
- response-deletescript = response-oknobye
-
- response-getscript = (sieve-script CRLF response-ok) /
- response-nobye
-
- response-havespace = response-oknobye
-
- response-listscripts = *(sieve-name [SP "ACTIVE"] CRLF)
- response-oknobye
- ;; ACTIVE may only occur with one sieve-name
-
- response-logout = response-oknobye
-
- response-unauthenticate= response-oknobye
- ;; "NO" response can only be returned when
- ;; the command is issued in a wrong state
- ;; or has a wrong number of parameters
-
- response-ok = "OK" [SP "(" resp-code ")"]
- [SP string] CRLF
- ;; The string contains human-readable text
- ;; encoded as UTF-8.
-
- response-nobye = ("NO" / "BYE") [SP "(" resp-code ")"]
- [SP string] CRLF
- ;; The string contains human-readable text
- ;; encoded as UTF-8.
-
-
-
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-
-
- response-oknobye = response-ok / response-nobye
-
- response-noop = response-ok
-
- response-putscript = response-oknobye
-
- response-checkscript = response-oknobye
-
- response-renamescript = response-oknobye
-
- response-setactive = response-oknobye
-
- response-starttls = (response-ok response-capability) /
- response-nobye
-
- sieve-name = string
- ;; See Section 1.6 for the full list of
- ;; prohibited characters.
- ;; Empty string is not allowed.
-
- active-sieve-name = string
- ;; See Section 1.6 for the full list of
- ;; prohibited characters.
- ;; This is similar to <sieve-name>, but
- ;; empty string is allowed and has a special
- ;; meaning.
-
- string = quoted / literal-c2s / literal-s2c
- ;; literal-c2s is only allowed when sent
- ;; from the client to the server.
- ;; literal-s2c is only allowed when sent
- ;; from the server to the client.
- ;; quoted is allowed in either direction.
-
-5. Security Considerations
-
- The AUTHENTICATE command uses SASL [SASL] to provide authentication
- and authorization services. Integrity and privacy services can be
- provided by [SASL] and/or [TLS]. When a SASL mechanism is used, the
- security considerations for that mechanism apply.
-
- This protocol's transactions are susceptible to passive observers or
- man-in-the-middle attacks that alter the data, unless the optional
- encryption and integrity services of the SASL (via the AUTHENTICATE
- command) and/or [TLS] (via the STARTTLS command) are enabled, or an
- external security mechanism is used for protection. It may be useful
- to allow configuration of both clients and servers to refuse to
- transfer sensitive information in the absence of strong encryption.
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- If an implementation supports SASL mechanisms that are vulnerable to
- passive eavesdropping attacks (such as [PLAIN]), then the
- implementation MUST support at least one configuration where these
- SASL mechanisms are not advertised or used without the presence of an
- external security layer such as [TLS].
-
- Some response codes returned on failed AUTHENTICATE command may
- disclose whether or not the username is valid (e.g., TRANSITION-
- NEEDED), so server implementations SHOULD provide the ability to
- disable these features (or make them not conditional on a per-user
- basis) for sites concerned about such disclosure. In the case of
- ENCRYPT-NEEDED, if it is applied to all identities then no extra
- information is disclosed, but if it is applied on a per-user basis it
- can disclose information.
-
- A compromised or malicious server can use the TRANSITION-NEEDED
- response code to force the client that is configured to use a
- mechanism that does not disclose the user's password to the server
- (e.g., Kerberos), to send the bare password to the server. Clients
- SHOULD have the ability to disable the password transition feature,
- or disclose that risk to the user and offer the user an option of how
- to proceed.
-
-6. IANA Considerations
-
- IANA has reserved TCP port number 4190 for use with the ManageSieve
- protocol described in this document.
-
- IANA has registered the "sieve" URI scheme defined in Section 3 of
- this document.
-
- IANA has registered "sieve" in the "GSSAPI/Kerberos/SASL Service
- Names" registry.
-
- IANA has created a new registry for ManageSieve capabilities. The
- registration template for ManageSieve capabilities is specified in
- Section 6.1. ManageSieve protocol capabilities MUST be specified in
- a Standards-Track or IESG-approved Experimental RFC.
-
- IANA has created a new registry for ManageSieve response codes. The
- registration template for ManageSieve response codes is specified in
- Section 6.3. ManageSieve protocol response codes MUST be specified
- in a Standards-Track or IESG-approved Experimental RFC.
-
-
-
-
-
-
-
-
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-RFC 5804 ManageSieve July 2010
-
-
-6.1. ManageSieve Capability Registration Template
-
- To: iana@iana.org
- Subject: ManageSieve Capability Registration
-
- Please register the following ManageSieve capability:
-
- Capability name:
- Description:
- Relevant publications:
- Person & email address to contact for further information:
- Author/Change controller:
-
-6.2. Registration of Initial ManageSieve Capabilities
-
- To: iana@iana.org
- Subject: ManageSieve Capability Registration
-
- Please register the following ManageSieve capabilities:
-
- Capability name: IMPLEMENTATION
- Description: Its value contains the name of the server
- implementation and its version.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: SASL
- Description: Its value contains a space-separated list of SASL
- mechanisms supported by the server.
- Relevant publications: this RFC, Sections 1.7 and 2.1.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: SIEVE
- Description: Its value contains a space-separated list of supported
- SIEVE extensions.
- Relevant publications: this RFC, Section 1.7. Also [SIEVE].
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
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-RFC 5804 ManageSieve July 2010
-
-
- Capability name: STARTTLS
- Description: This capability is returned if the server supports TLS
- (STARTTLS command).
- Relevant publications: this RFC, Sections 1.7 and 2.2.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: NOTIFY
- Description: This capability is returned if the server supports the
- 'enotify' [NOTIFY] Sieve extension.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: MAXREDIRECTS
- Description: This capability returns the limit on the number of
- Sieve "redirect" actions a script can perform during a
- single evaluation. The value is a non-negative number
- represented as a ManageSieve string.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: LANGUAGE
- Description: The language (<Language-Tag> from [RFC5646]) currently
- used for human-readable error messages.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: OWNER
- Description: Its value contains the UTF-8-encoded name of the
- currently logged-in user ("authorization identity"
- according to RFC 4422).
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- Capability name: VERSION
- Description: This capability is returned if the server is compliant
- with RFC 5804; i.e., that it supports RENAMESCRIPT,
- CHECKSCRIPT, and NOOP commands.
- Relevant publications: this RFC, Sections 2.11, 2.12, and 2.13.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-6.3. ManageSieve Response Code Registration Template
-
- To: iana@iana.org
- Subject: ManageSieve Response Code Registration
-
- Please register the following ManageSieve response code:
-
- Response Code:
- Arguments (use ABNF to specify syntax, or the word NONE if none
- can be specified):
- Purpose:
- Published Specification(s):
- Person & email address to contact for further information:
- Author/Change controller:
-
-6.4. Registration of Initial ManageSieve Response Codes
-
- To: iana@iana.org
- Subject: ManageSieve Response Code Registration
-
- Please register the following ManageSieve response codes:
-
- Response Code: AUTH-TOO-WEAK
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code is returned in the NO response from
- an AUTHENTICATE command. It indicates that site
- security policy forbids the use of the requested
- mechanism for the specified authentication identity.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- Response Code: ENCRYPT-NEEDED
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code is returned in the NO response from
- an AUTHENTICATE command. It indicates that site
- security policy requires the use of a strong
- encryption mechanism for the specified authentication
- identity and mechanism.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: QUOTA
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined quota constraints. If
- this response code is returned in the OK response, it
- can mean that the user is near its quota or that the
- user exceeded its quota, but the server supports soft
- quotas.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: QUOTA/MAXSCRIPTS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined limit on the number of
- Sieve scripts. If this response code is returned in
- the OK response, it can mean that the user is near its
- quota or that the user exceeded its quota, but the
- server supports soft quotas. This response code is a
- more specific version of the QUOTA response code.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
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-
-
- Response Code: QUOTA/MAXSIZE
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined maximum script size.
- If this response code is returned in the OK response,
- it can mean that the user is near its quota or that
- the user exceeded its quota, but the server supports
- soft quotas. This response code is a more specific
- version of the QUOTA response code.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: REFERRAL
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): <sieveurl>
- Purpose: This response code may be returned with a BYE result
- from any command, and includes a mandatory parameter
- that indicates what server to access to manage this
- user's Sieve scripts. The server will be specified by
- a Sieve URL (see Section 3). The scriptname portion
- of the URL MUST NOT be specified. The client should
- authenticate to the specified server and use it for
- all further commands in the current session.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: SASL
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): <string>
- Purpose: This response code can occur in the OK response to a
- successful AUTHENTICATE command and includes the
- optional final server response data from the server as
- specified by [SASL].
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 43]
-
-RFC 5804 ManageSieve July 2010
-
-
- Response Code: TRANSITION-NEEDED
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code occurs in a NO response of an
- AUTHENTICATE command. It indicates that the user name
- is valid, but the entry in the authentication database
- needs to be updated in order to permit authentication
- with the specified mechanism. This is typically done
- by establishing a secure channel using TLS, followed
- by authenticating once using the [PLAIN]
- authentication mechanism. The selected mechanism
- SHOULD then work for authentications in subsequent
- sessions.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: TRYLATER
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed due to a temporary server failure.
- The client MAY continue using local information and
- try the command later. This response code only make
- sense when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: ACTIVE
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because it is not allowed on the
- active script, for example, DELETESCRIPT on the active
- script. This response code only makes sense when
- returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 44]
-
-RFC 5804 ManageSieve July 2010
-
-
- Response Code: NONEXISTENT
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because the referenced script name
- doesn't exist. This response code only makes sense
- when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: ALREADYEXISTS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because the referenced script name
- already exists. This response code only makes sense
- when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: WARNINGS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code MAY be returned by the server in
- the OK response (but it might be returned with the NO/
- BYE response as well) and signals the client that even
- though the script is syntactically valid, it might
- contain errors not intended by the script writer.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: TAG
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): string
- Purpose: This response code name is followed by a string
- specified in the command that caused this response.
- It is typically used for client state synchronization.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 45]
-
-RFC 5804 ManageSieve July 2010
-
-
-7. Internationalization Considerations
-
- The LANGUAGE capability (see Section 1.7) allows a client to discover
- the current language used in all human-readable responses that might
- be returned at the end of any OK/NO/BYE response. Human-readable
- text in OK responses typically doesn't need to be shown to the user,
- unless it is returned in response to a PUTSCRIPT or CHECKSCRIPT
- command that also contains the WARNINGS response code (Section 1.3).
- Human-readable text from NO/BYE responses is intended be shown to the
- user, unless the client can automatically handle failure of the
- command that caused such a response. Clients SHOULD use response
- codes (Section 1.3) for automatic error handling. Response codes MAY
- also be used by the client to present error messages in a language
- understood by the user, for example, if the LANGUAGE capability
- doesn't return a language understood by the user.
-
- Note that the human-readable text from OK (WARNINGS) or NO/BYE
- responses for PUTSCRIPT/CHECKSCRIPT commands is intended for advanced
- users that understand Sieve language. Such advanced users are often
- sophisticated enough to be able to handle whatever language the
- server is using, even if it is not their preferred language, and will
- want to see error/warning text no matter what language the server
- puts it in.
-
- A client that generates Sieve script automatically, for example, if
- the script is generated without user intervention or from a UI that
- presents an abstract list of conditions and corresponding actions,
- SHOULD NOT present warning/error messages to the user, because the
- user might not even be aware that the client is using Sieve
- underneath. However, if the client has a debugging mode, such
- warnings/errors SHOULD be available in the debugging mode.
-
- Note that this document doesn't provide a way to modify the currently
- used language. It is expected that a future extension will address
- that.
-
-8. Acknowledgements
-
- Thanks to Simon Josefsson, Larry Greenfield, Allen Johnson, Chris
- Newman, Lyndon Nerenberg, Tim Showalter, Sarah Robeson, Walter Wong,
- Barry Leiba, Arnt Gulbrandsen, Stephan Bosch, Ken Murchison, Phil
- Pennock, Ned Freed, Jeffrey Hutzelman, Mark E. Mallett, Dilyan
- Palauzov, Dave Cridland, Aaron Stone, Robert Burrell Donkin, Patrick
- Ben Koetter, Bjoern Hoehrmann, Martin Duerst, Pasi Eronen, Magnus
- Westerlund, Tim Polk, and Julien Coloos for help with this document.
- Special thank you to Phil Pennock for providing text for the NOOP
- command, as well as finding various bugs in the document.
-
-
-
-
-Melnikov & Martin Standards Track [Page 46]
-
-RFC 5804 ManageSieve July 2010
-
-
-9. References
-
-9.1. Normative References
-
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", STD 68, RFC 5234, January 2008.
-
- [ACAP] Newman, C. and J. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November
- 1997.
-
- [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
- Encodings", RFC 4648, October 2006.
-
- [DNS-SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR
- for specifying the location of services (DNS SRV)",
- RFC 2782, February 2000.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [NET-UNICODE] Klensin, J. and M. Padlipsky, "Unicode Format for
- Network Interchange", RFC 5198, March 2008.
-
- [NOTIFY] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
- "Sieve Email Filtering: Extension for Notifications",
- RFC 5435, January 2009.
-
- [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
- Languages", BCP 18, RFC 2277, January 1998.
-
- [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version
- 6 (IPv6) Specification", RFC 2460, December 1998.
-
- [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
- "Internationalizing Domain Names in Applications
- (IDNA)", RFC 3490, March 2003.
-
- [RFC4519] Sciberras, A., "Lightweight Directory Access Protocol
- (LDAP): Schema for User Applications", RFC 4519, June
- 2006.
-
- [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
- Languages", BCP 47, RFC 5646, September 2009.
-
- [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
- September 1981.
-
-
-
-
-Melnikov & Martin Standards Track [Page 47]
-
-RFC 5804 ManageSieve July 2010
-
-
- [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication
- and Security Layer (SASL)", RFC 4422, June 2006.
-
- [SASLprep] Zeilenga, K., "SASLprep: Stringprep Profile for User
- Names and Passwords", RFC 4013, February 2005.
-
- [SCRAM] Menon-Sen, A., Melnikov, A., Newman, C., and N.
- Williams, "Salted Challenge Response Authentication
- Mechanism (SCRAM) SASL and GSS-API Mechanisms", RFC
- 5802, July 2010.
-
- [SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email
- Filtering Language", RFC 5228, January 2008.
-
- [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
- Internationalized Strings ("stringprep")", RFC 3454,
- December 2002.
-
- [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
- Security (TLS) Protocol Version 1.2", RFC 5246, August
- 2008.
-
- [URI-GEN] Berners-Lee, T., Fielding, R., and L. Masinter,
- "Uniform Resource Identifier (URI): Generic Syntax",
- STD 66, RFC 3986, January 2005.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", STD 63, RFC 3629, November 2003.
-
- [X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
- Housley, R., and W. Polk, "Internet X.509 Public Key
- Infrastructure Certificate and Certificate Revocation
- List (CRL) Profile", RFC 5280, May 2008.
-
- [X509-SRV] Santesson, S., "Internet X.509 Public Key
- Infrastructure Subject Alternative Name for Expression
- of Service Name", RFC 4985, August 2007.
-
-9.2. Informative References
-
- [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication
- as a SASL Mechanism", RFC 2831, May 2000.
-
- [GSSAPI] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
- Authentication and Security Layer (SASL) Mechanism",
- RFC 4752, November 2006.
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 48]
-
-RFC 5804 ManageSieve July 2010
-
-
- [I-HAVE] Freed, N., "Sieve Email Filtering: Ihave Extension",
- RFC 5463, March 2009.
-
- [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
- VERSION 4rev1", RFC 3501, March 2003.
-
- [LDAP] Zeilenga, K., "Lightweight Directory Access Protocol
- (LDAP): Technical Specification Road Map", RFC 4510,
- June 2006.
-
- [PLAIN] Zeilenga, K., "The PLAIN Simple Authentication and
- Security Layer (SASL) Mechanism", RFC 4616, August
- 2006.
-
-Authors' Addresses
-
- Alexey Melnikov (editor)
- Isode Limited
- 5 Castle Business Village
- 36 Station Road
- Hampton, Middlesex TW12 2BX
- UK
-
- EMail: Alexey.Melnikov@isode.com
-
-
- Tim Martin
- BeThereBeSquare, Inc.
- 672 Haight st.
- San Francisco, CA 94117
- USA
-
- Phone: +1 510 260-4175
- EMail: timmartin@alumni.cmu.edu
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 49]
-
diff --git a/proto/rfc822.txt b/proto/rfc822.txt
@@ -1,2901 +0,0 @@
-
-
-
-
-
-
- RFC # 822
-
- Obsoletes: RFC #733 (NIC #41952)
-
-
-
-
-
-
-
-
-
-
-
-
- STANDARD FOR THE FORMAT OF
-
- ARPA INTERNET TEXT MESSAGES
-
-
-
-
-
-
- August 13, 1982
-
-
-
-
-
-
- Revised by
-
- David H. Crocker
-
-
- Dept. of Electrical Engineering
- University of Delaware, Newark, DE 19711
- Network: DCrocker @ UDel-Relay
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- TABLE OF CONTENTS
-
-
- PREFACE .................................................... ii
-
- 1. INTRODUCTION ........................................... 1
-
- 1.1. Scope ............................................ 1
- 1.2. Communication Framework .......................... 2
-
- 2. NOTATIONAL CONVENTIONS ................................. 3
-
- 3. LEXICAL ANALYSIS OF MESSAGES ........................... 5
-
- 3.1. General Description .............................. 5
- 3.2. Header Field Definitions ......................... 9
- 3.3. Lexical Tokens ................................... 10
- 3.4. Clarifications ................................... 11
-
- 4. MESSAGE SPECIFICATION .................................. 17
-
- 4.1. Syntax ........................................... 17
- 4.2. Forwarding ....................................... 19
- 4.3. Trace Fields ..................................... 20
- 4.4. Originator Fields ................................ 21
- 4.5. Receiver Fields .................................. 23
- 4.6. Reference Fields ................................. 23
- 4.7. Other Fields ..................................... 24
-
- 5. DATE AND TIME SPECIFICATION ............................ 26
-
- 5.1. Syntax ........................................... 26
- 5.2. Semantics ........................................ 26
-
- 6. ADDRESS SPECIFICATION .................................. 27
-
- 6.1. Syntax ........................................... 27
- 6.2. Semantics ........................................ 27
- 6.3. Reserved Address ................................. 33
-
- 7. BIBLIOGRAPHY ........................................... 34
-
-
- APPENDIX
-
- A. EXAMPLES ............................................... 36
- B. SIMPLE FIELD PARSING ................................... 40
- C. DIFFERENCES FROM RFC #733 .............................. 41
- D. ALPHABETICAL LISTING OF SYNTAX RULES ................... 44
-
-
- August 13, 1982 - i - RFC #822
-
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- PREFACE
-
-
- By 1977, the Arpanet employed several informal standards for
- the text messages (mail) sent among its host computers. It was
- felt necessary to codify these practices and provide for those
- features that seemed imminent. The result of that effort was
- Request for Comments (RFC) #733, "Standard for the Format of ARPA
- Network Text Message", by Crocker, Vittal, Pogran, and Henderson.
- The specification attempted to avoid major changes in existing
- software, while permitting several new features.
-
- This document revises the specifications in RFC #733, in
- order to serve the needs of the larger and more complex ARPA
- Internet. Some of RFC #733's features failed to gain adequate
- acceptance. In order to simplify the standard and the software
- that follows it, these features have been removed. A different
- addressing scheme is used, to handle the case of inter-network
- mail; and the concept of re-transmission has been introduced.
-
- This specification is intended for use in the ARPA Internet.
- However, an attempt has been made to free it of any dependence on
- that environment, so that it can be applied to other network text
- message systems.
-
- The specification of RFC #733 took place over the course of
- one year, using the ARPANET mail environment, itself, to provide
- an on-going forum for discussing the capabilities to be included.
- More than twenty individuals, from across the country, partici-
- pated in the original discussion. The development of this
- revised specification has, similarly, utilized network mail-based
- group discussion. Both specification efforts greatly benefited
- from the comments and ideas of the participants.
-
- The syntax of the standard, in RFC #733, was originally
- specified in the Backus-Naur Form (BNF) meta-language. Ken L.
- Harrenstien, of SRI International, was responsible for re-coding
- the BNF into an augmented BNF that makes the representation
- smaller and easier to understand.
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - ii - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 1. INTRODUCTION
-
- 1.1. SCOPE
-
- This standard specifies a syntax for text messages that are
- sent among computer users, within the framework of "electronic
- mail". The standard supersedes the one specified in ARPANET
- Request for Comments #733, "Standard for the Format of ARPA Net-
- work Text Messages".
-
- In this context, messages are viewed as having an envelope
- and contents. The envelope contains whatever information is
- needed to accomplish transmission and delivery. The contents
- compose the object to be delivered to the recipient. This stan-
- dard applies only to the format and some of the semantics of mes-
- sage contents. It contains no specification of the information
- in the envelope.
-
- However, some message systems may use information from the
- contents to create the envelope. It is intended that this stan-
- dard facilitate the acquisition of such information by programs.
-
- Some message systems may store messages in formats that
- differ from the one specified in this standard. This specifica-
- tion is intended strictly as a definition of what message content
- format is to be passed BETWEEN hosts.
-
- Note: This standard is NOT intended to dictate the internal for-
- mats used by sites, the specific message system features
- that they are expected to support, or any of the charac-
- teristics of user interface programs that create or read
- messages.
-
- A distinction should be made between what the specification
- REQUIRES and what it ALLOWS. Messages can be made complex and
- rich with formally-structured components of information or can be
- kept small and simple, with a minimum of such information. Also,
- the standard simplifies the interpretation of differing visual
- formats in messages; only the visual aspect of a message is
- affected and not the interpretation of information within it.
- Implementors may choose to retain such visual distinctions.
-
- The formal definition is divided into four levels. The bot-
- tom level describes the meta-notation used in this document. The
- second level describes basic lexical analyzers that feed tokens
- to higher-level parsers. Next is an overall specification for
- messages; it permits distinguishing individual fields. Finally,
- there is definition of the contents of several structured fields.
-
-
-
- August 13, 1982 - 1 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 1.2. COMMUNICATION FRAMEWORK
-
- Messages consist of lines of text. No special provisions
- are made for encoding drawings, facsimile, speech, or structured
- text. No significant consideration has been given to questions
- of data compression or to transmission and storage efficiency,
- and the standard tends to be free with the number of bits con-
- sumed. For example, field names are specified as free text,
- rather than special terse codes.
-
- A general "memo" framework is used. That is, a message con-
- sists of some information in a rigid format, followed by the main
- part of the message, with a format that is not specified in this
- document. The syntax of several fields of the rigidly-formated
- ("headers") section is defined in this specification; some of
- these fields must be included in all messages.
-
- The syntax that distinguishes between header fields is
- specified separately from the internal syntax for particular
- fields. This separation is intended to allow simple parsers to
- operate on the general structure of messages, without concern for
- the detailed structure of individual header fields. Appendix B
- is provided to facilitate construction of these parsers.
-
- In addition to the fields specified in this document, it is
- expected that other fields will gain common use. As necessary,
- the specifications for these "extension-fields" will be published
- through the same mechanism used to publish this document. Users
- may also wish to extend the set of fields that they use
- privately. Such "user-defined fields" are permitted.
-
- The framework severely constrains document tone and appear-
- ance and is primarily useful for most intra-organization communi-
- cations and well-structured inter-organization communication.
- It also can be used for some types of inter-process communica-
- tion, such as simple file transfer and remote job entry. A more
- robust framework might allow for multi-font, multi-color, multi-
- dimension encoding of information. A less robust one, as is
- present in most single-machine message systems, would more
- severely constrain the ability to add fields and the decision to
- include specific fields. In contrast with paper-based communica-
- tion, it is interesting to note that the RECEIVER of a message
- can exercise an extraordinary amount of control over the
- message's appearance. The amount of actual control available to
- message receivers is contingent upon the capabilities of their
- individual message systems.
-
-
-
-
-
- August 13, 1982 - 2 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 2. NOTATIONAL CONVENTIONS
-
- This specification uses an augmented Backus-Naur Form (BNF)
- notation. The differences from standard BNF involve naming rules
- and indicating repetition and "local" alternatives.
-
- 2.1. RULE NAMING
-
- Angle brackets ("<", ">") are not used, in general. The
- name of a rule is simply the name itself, rather than "<name>".
- Quotation-marks enclose literal text (which may be upper and/or
- lower case). Certain basic rules are in uppercase, such as
- SPACE, TAB, CRLF, DIGIT, ALPHA, etc. Angle brackets are used in
- rule definitions, and in the rest of this document, whenever
- their presence will facilitate discerning the use of rule names.
-
- 2.2. RULE1 / RULE2: ALTERNATIVES
-
- Elements separated by slash ("/") are alternatives. There-
- fore "foo / bar" will accept foo or bar.
-
- 2.3. (RULE1 RULE2): LOCAL ALTERNATIVES
-
- Elements enclosed in parentheses are treated as a single
- element. Thus, "(elem (foo / bar) elem)" allows the token
- sequences "elem foo elem" and "elem bar elem".
-
- 2.4. *RULE: REPETITION
-
- The character "*" preceding an element indicates repetition.
- The full form is:
-
- <l>*<m>element
-
- indicating at least <l> and at most <m> occurrences of element.
- Default values are 0 and infinity so that "*(element)" allows any
- number, including zero; "1*element" requires at least one; and
- "1*2element" allows one or two.
-
- 2.5. [RULE]: OPTIONAL
-
- Square brackets enclose optional elements; "[foo bar]" is
- equivalent to "*1(foo bar)".
-
- 2.6. NRULE: SPECIFIC REPETITION
-
- "<n>(element)" is equivalent to "<n>*<n>(element)"; that is,
- exactly <n> occurrences of (element). Thus 2DIGIT is a 2-digit
- number, and 3ALPHA is a string of three alphabetic characters.
-
-
- August 13, 1982 - 3 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 2.7. #RULE: LISTS
-
- A construct "#" is defined, similar to "*", as follows:
-
- <l>#<m>element
-
- indicating at least <l> and at most <m> elements, each separated
- by one or more commas (","). This makes the usual form of lists
- very easy; a rule such as '(element *("," element))' can be shown
- as "1#element". Wherever this construct is used, null elements
- are allowed, but do not contribute to the count of elements
- present. That is, "(element),,(element)" is permitted, but
- counts as only two elements. Therefore, where at least one ele-
- ment is required, at least one non-null element must be present.
- Default values are 0 and infinity so that "#(element)" allows any
- number, including zero; "1#element" requires at least one; and
- "1#2element" allows one or two.
-
- 2.8. ; COMMENTS
-
- A semi-colon, set off some distance to the right of rule
- text, starts a comment that continues to the end of line. This
- is a simple way of including useful notes in parallel with the
- specifications.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 4 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 3. LEXICAL ANALYSIS OF MESSAGES
-
- 3.1. GENERAL DESCRIPTION
-
- A message consists of header fields and, optionally, a body.
- The body is simply a sequence of lines containing ASCII charac-
- ters. It is separated from the headers by a null line (i.e., a
- line with nothing preceding the CRLF).
-
- 3.1.1. LONG HEADER FIELDS
-
- Each header field can be viewed as a single, logical line of
- ASCII characters, comprising a field-name and a field-body.
- For convenience, the field-body portion of this conceptual
- entity can be split into a multiple-line representation; this
- is called "folding". The general rule is that wherever there
- may be linear-white-space (NOT simply LWSP-chars), a CRLF
- immediately followed by AT LEAST one LWSP-char may instead be
- inserted. Thus, the single line
-
- To: "Joe & J. Harvey" <ddd @Org>, JJV @ BBN
-
- can be represented as:
-
- To: "Joe & J. Harvey" <ddd @ Org>,
- JJV@BBN
-
- and
-
- To: "Joe & J. Harvey"
- <ddd@ Org>, JJV
- @BBN
-
- and
-
- To: "Joe &
- J. Harvey" <ddd @ Org>, JJV @ BBN
-
- The process of moving from this folded multiple-line
- representation of a header field to its single line represen-
- tation is called "unfolding". Unfolding is accomplished by
- regarding CRLF immediately followed by a LWSP-char as
- equivalent to the LWSP-char.
-
- Note: While the standard permits folding wherever linear-
- white-space is permitted, it is recommended that struc-
- tured fields, such as those containing addresses, limit
- folding to higher-level syntactic breaks. For address
- fields, it is recommended that such folding occur
-
-
- August 13, 1982 - 5 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- between addresses, after the separating comma.
-
- 3.1.2. STRUCTURE OF HEADER FIELDS
-
- Once a field has been unfolded, it may be viewed as being com-
- posed of a field-name followed by a colon (":"), followed by a
- field-body, and terminated by a carriage-return/line-feed.
- The field-name must be composed of printable ASCII characters
- (i.e., characters that have values between 33. and 126.,
- decimal, except colon). The field-body may be composed of any
- ASCII characters, except CR or LF. (While CR and/or LF may be
- present in the actual text, they are removed by the action of
- unfolding the field.)
-
- Certain field-bodies of headers may be interpreted according
- to an internal syntax that some systems may wish to parse.
- These fields are called "structured fields". Examples
- include fields containing dates and addresses. Other fields,
- such as "Subject" and "Comments", are regarded simply as
- strings of text.
-
- Note: Any field which has a field-body that is defined as
- other than simply <text> is to be treated as a struc-
- tured field.
-
- Field-names, unstructured field bodies and structured
- field bodies each are scanned by their own, independent
- "lexical" analyzers.
-
- 3.1.3. UNSTRUCTURED FIELD BODIES
-
- For some fields, such as "Subject" and "Comments", no struc-
- turing is assumed, and they are treated simply as <text>s, as
- in the message body. Rules of folding apply to these fields,
- so that such field bodies which occupy several lines must
- therefore have the second and successive lines indented by at
- least one LWSP-char.
-
- 3.1.4. STRUCTURED FIELD BODIES
-
- To aid in the creation and reading of structured fields, the
- free insertion of linear-white-space (which permits folding
- by inclusion of CRLFs) is allowed between lexical tokens.
- Rather than obscuring the syntax specifications for these
- structured fields with explicit syntax for this linear-white-
- space, the existence of another "lexical" analyzer is assumed.
- This analyzer does not apply for unstructured field bodies
- that are simply strings of text, as described above. The
- analyzer provides an interpretation of the unfolded text
-
-
- August 13, 1982 - 6 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- composing the body of the field as a sequence of lexical sym-
- bols.
-
- These symbols are:
-
- - individual special characters
- - quoted-strings
- - domain-literals
- - comments
- - atoms
-
- The first four of these symbols are self-delimiting. Atoms
- are not; they are delimited by the self-delimiting symbols and
- by linear-white-space. For the purposes of regenerating
- sequences of atoms and quoted-strings, exactly one SPACE is
- assumed to exist, and should be used, between them. (Also, in
- the "Clarifications" section on "White Space", below, note the
- rules about treatment of multiple contiguous LWSP-chars.)
-
- So, for example, the folded body of an address field
-
- ":sysmail"@ Some-Group. Some-Org,
- Muhammed.(I am the greatest) Ali @(the)Vegas.WBA
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 7 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- is analyzed into the following lexical symbols and types:
-
- :sysmail quoted string
- @ special
- Some-Group atom
- . special
- Some-Org atom
- , special
- Muhammed atom
- . special
- (I am the greatest) comment
- Ali atom
- @ atom
- (the) comment
- Vegas atom
- . special
- WBA atom
-
- The canonical representations for the data in these addresses
- are the following strings:
-
- ":sysmail"@Some-Group.Some-Org
-
- and
-
- Muhammed.Ali@Vegas.WBA
-
- Note: For purposes of display, and when passing such struc-
- tured information to other systems, such as mail proto-
- col services, there must be NO linear-white-space
- between <word>s that are separated by period (".") or
- at-sign ("@") and exactly one SPACE between all other
- <word>s. Also, headers should be in a folded form.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 8 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 3.2. HEADER FIELD DEFINITIONS
-
- These rules show a field meta-syntax, without regard for the
- particular type or internal syntax. Their purpose is to permit
- detection of fields; also, they present to higher-level parsers
- an image of each field as fitting on one line.
-
- field = field-name ":" [ field-body ] CRLF
-
- field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
-
- field-body = field-body-contents
- [CRLF LWSP-char field-body]
-
- field-body-contents =
- <the ASCII characters making up the field-body, as
- defined in the following sections, and consisting
- of combinations of atom, quoted-string, and
- specials tokens, or else consisting of texts>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 9 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 3.3. LEXICAL TOKENS
-
- The following rules are used to define an underlying lexical
- analyzer, which feeds tokens to higher level parsers. See the
- ANSI references, in the Bibliography.
-
- ; ( Octal, Decimal.)
- CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
- ALPHA = <any ASCII alphabetic character>
- ; (101-132, 65.- 90.)
- ; (141-172, 97.-122.)
- DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.)
- CTL = <any ASCII control ; ( 0- 37, 0.- 31.)
- character and DEL> ; ( 177, 127.)
- CR = <ASCII CR, carriage return> ; ( 15, 13.)
- LF = <ASCII LF, linefeed> ; ( 12, 10.)
- SPACE = <ASCII SP, space> ; ( 40, 32.)
- HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.)
- <"> = <ASCII quote mark> ; ( 42, 34.)
- CRLF = CR LF
-
- LWSP-char = SPACE / HTAB ; semantics = SPACE
-
- linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE
- ; CRLF => folding
-
- specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-
- / "," / ";" / ":" / "\" / <"> ; string, to use
- / "." / "[" / "]" ; within a word.
-
- delimiters = specials / linear-white-space / comment
-
- text = <any CHAR, including bare ; => atoms, specials,
- CR & bare LF, but NOT ; comments and
- including CRLF> ; quoted-strings are
- ; NOT recognized.
-
- atom = 1*<any CHAR except specials, SPACE and CTLs>
-
- quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
- ; quoted chars.
-
- qtext = <any CHAR excepting <">, ; => may be folded
- "\" & CR, and including
- linear-white-space>
-
- domain-literal = "[" *(dtext / quoted-pair) "]"
-
-
-
-
- August 13, 1982 - 10 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- dtext = <any CHAR excluding "[", ; => may be folded
- "]", "\" & CR, & including
- linear-white-space>
-
- comment = "(" *(ctext / quoted-pair / comment) ")"
-
- ctext = <any CHAR excluding "(", ; => may be folded
- ")", "\" & CR, & including
- linear-white-space>
-
- quoted-pair = "\" CHAR ; may quote any char
-
- phrase = 1*word ; Sequence of words
-
- word = atom / quoted-string
-
-
- 3.4. CLARIFICATIONS
-
- 3.4.1. QUOTING
-
- Some characters are reserved for special interpretation, such
- as delimiting lexical tokens. To permit use of these charac-
- ters as uninterpreted data, a quoting mechanism is provided.
- To quote a character, precede it with a backslash ("\").
-
- This mechanism is not fully general. Characters may be quoted
- only within a subset of the lexical constructs. In particu-
- lar, quoting is limited to use within:
-
- - quoted-string
- - domain-literal
- - comment
-
- Within these constructs, quoting is REQUIRED for CR and "\"
- and for the character(s) that delimit the token (e.g., "(" and
- ")" for a comment). However, quoting is PERMITTED for any
- character.
-
- Note: In particular, quoting is NOT permitted within atoms.
- For example when the local-part of an addr-spec must
- contain a special character, a quoted string must be
- used. Therefore, a specification such as:
-
- Full\ Name@Domain
-
- is not legal and must be specified as:
-
- "Full Name"@Domain
-
-
- August 13, 1982 - 11 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 3.4.2. WHITE SPACE
-
- Note: In structured field bodies, multiple linear space ASCII
- characters (namely HTABs and SPACEs) are treated as
- single spaces and may freely surround any symbol. In
- all header fields, the only place in which at least one
- LWSP-char is REQUIRED is at the beginning of continua-
- tion lines in a folded field.
-
- When passing text to processes that do not interpret text
- according to this standard (e.g., mail protocol servers), then
- NO linear-white-space characters should occur between a period
- (".") or at-sign ("@") and a <word>. Exactly ONE SPACE should
- be used in place of arbitrary linear-white-space and comment
- sequences.
-
- Note: Within systems conforming to this standard, wherever a
- member of the list of delimiters is allowed, LWSP-chars
- may also occur before and/or after it.
-
- Writers of mail-sending (i.e., header-generating) programs
- should realize that there is no network-wide definition of the
- effect of ASCII HT (horizontal-tab) characters on the appear-
- ance of text at another network host; therefore, the use of
- tabs in message headers, though permitted, is discouraged.
-
- 3.4.3. COMMENTS
-
- A comment is a set of ASCII characters, which is enclosed in
- matching parentheses and which is not within a quoted-string
- The comment construct permits message originators to add text
- which will be useful for human readers, but which will be
- ignored by the formal semantics. Comments should be retained
- while the message is subject to interpretation according to
- this standard. However, comments must NOT be included in
- other cases, such as during protocol exchanges with mail
- servers.
-
- Comments nest, so that if an unquoted left parenthesis occurs
- in a comment string, there must also be a matching right
- parenthesis. When a comment acts as the delimiter between a
- sequence of two lexical symbols, such as two atoms, it is lex-
- ically equivalent with a single SPACE, for the purposes of
- regenerating the sequence, such as when passing the sequence
- onto a mail protocol server. Comments are detected as such
- only within field-bodies of structured fields.
-
- If a comment is to be "folded" onto multiple lines, then the
- syntax for folding must be adhered to. (See the "Lexical
-
-
- August 13, 1982 - 12 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- Analysis of Messages" section on "Folding Long Header Fields"
- above, and the section on "Case Independence" below.) Note
- that the official semantics therefore do not "see" any
- unquoted CRLFs that are in comments, although particular pars-
- ing programs may wish to note their presence. For these pro-
- grams, it would be reasonable to interpret a "CRLF LWSP-char"
- as being a CRLF that is part of the comment; i.e., the CRLF is
- kept and the LWSP-char is discarded. Quoted CRLFs (i.e., a
- backslash followed by a CR followed by a LF) still must be
- followed by at least one LWSP-char.
-
- 3.4.4. DELIMITING AND QUOTING CHARACTERS
-
- The quote character (backslash) and characters that delimit
- syntactic units are not, generally, to be taken as data that
- are part of the delimited or quoted unit(s). In particular,
- the quotation-marks that define a quoted-string, the
- parentheses that define a comment and the backslash that
- quotes a following character are NOT part of the quoted-
- string, comment or quoted character. A quotation-mark that is
- to be part of a quoted-string, a parenthesis that is to be
- part of a comment and a backslash that is to be part of either
- must each be preceded by the quote-character backslash ("\").
- Note that the syntax allows any character to be quoted within
- a quoted-string or comment; however only certain characters
- MUST be quoted to be included as data. These characters are
- the ones that are not part of the alternate text group (i.e.,
- ctext or qtext).
-
- The one exception to this rule is that a single SPACE is
- assumed to exist between contiguous words in a phrase, and
- this interpretation is independent of the actual number of
- LWSP-chars that the creator places between the words. To
- include more than one SPACE, the creator must make the LWSP-
- chars be part of a quoted-string.
-
- Quotation marks that delimit a quoted string and backslashes
- that quote the following character should NOT accompany the
- quoted-string when the string is passed to processes that do
- not interpret data according to this specification (e.g., mail
- protocol servers).
-
- 3.4.5. QUOTED-STRINGS
-
- Where permitted (i.e., in words in structured fields) quoted-
- strings are treated as a single symbol. That is, a quoted-
- string is equivalent to an atom, syntactically. If a quoted-
- string is to be "folded" onto multiple lines, then the syntax
- for folding must be adhered to. (See the "Lexical Analysis of
-
-
- August 13, 1982 - 13 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- Messages" section on "Folding Long Header Fields" above, and
- the section on "Case Independence" below.) Therefore, the
- official semantics do not "see" any bare CRLFs that are in
- quoted-strings; however particular parsing programs may wish
- to note their presence. For such programs, it would be rea-
- sonable to interpret a "CRLF LWSP-char" as being a CRLF which
- is part of the quoted-string; i.e., the CRLF is kept and the
- LWSP-char is discarded. Quoted CRLFs (i.e., a backslash fol-
- lowed by a CR followed by a LF) are also subject to rules of
- folding, but the presence of the quoting character (backslash)
- explicitly indicates that the CRLF is data to the quoted
- string. Stripping off the first following LWSP-char is also
- appropriate when parsing quoted CRLFs.
-
- 3.4.6. BRACKETING CHARACTERS
-
- There is one type of bracket which must occur in matched pairs
- and may have pairs nested within each other:
-
- o Parentheses ("(" and ")") are used to indicate com-
- ments.
-
- There are three types of brackets which must occur in matched
- pairs, and which may NOT be nested:
-
- o Colon/semi-colon (":" and ";") are used in address
- specifications to indicate that the included list of
- addresses are to be treated as a group.
-
- o Angle brackets ("<" and ">") are generally used to
- indicate the presence of a one machine-usable refer-
- ence (e.g., delimiting mailboxes), possibly including
- source-routing to the machine.
-
- o Square brackets ("[" and "]") are used to indicate the
- presence of a domain-literal, which the appropriate
- name-domain is to use directly, bypassing normal
- name-resolution mechanisms.
-
- 3.4.7. CASE INDEPENDENCE
-
- Except as noted, alphabetic strings may be represented in any
- combination of upper and lower case. The only syntactic units
-
-
-
-
-
-
-
-
- August 13, 1982 - 14 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- which requires preservation of case information are:
-
- - text
- - qtext
- - dtext
- - ctext
- - quoted-pair
- - local-part, except "Postmaster"
-
- When matching any other syntactic unit, case is to be ignored.
- For example, the field-names "From", "FROM", "from", and even
- "FroM" are semantically equal and should all be treated ident-
- ically.
-
- When generating these units, any mix of upper and lower case
- alphabetic characters may be used. The case shown in this
- specification is suggested for message-creating processes.
-
- Note: The reserved local-part address unit, "Postmaster", is
- an exception. When the value "Postmaster" is being
- interpreted, it must be accepted in any mixture of
- case, including "POSTMASTER", and "postmaster".
-
- 3.4.8. FOLDING LONG HEADER FIELDS
-
- Each header field may be represented on exactly one line con-
- sisting of the name of the field and its body, and terminated
- by a CRLF; this is what the parser sees. For readability, the
- field-body portion of long header fields may be "folded" onto
- multiple lines of the actual field. "Long" is commonly inter-
- preted to mean greater than 65 or 72 characters. The former
- length serves as a limit, when the message is to be viewed on
- most simple terminals which use simple display software; how-
- ever, the limit is not imposed by this standard.
-
- Note: Some display software often can selectively fold lines,
- to suit the display terminal. In such cases, sender-
- provided folding can interfere with the display
- software.
-
- 3.4.9. BACKSPACE CHARACTERS
-
- ASCII BS characters (Backspace, decimal 8) may be included in
- texts and quoted-strings to effect overstriking. However, any
- use of backspaces which effects an overstrike to the left of
- the beginning of the text or quoted-string is prohibited.
-
-
-
-
-
- August 13, 1982 - 15 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 3.4.10. NETWORK-SPECIFIC TRANSFORMATIONS
-
- During transmission through heterogeneous networks, it may be
- necessary to force data to conform to a network's local con-
- ventions. For example, it may be required that a CR be fol-
- lowed either by LF, making a CRLF, or by <null>, if the CR is
- to stand alone). Such transformations are reversed, when the
- message exits that network.
-
- When crossing network boundaries, the message should be
- treated as passing through two modules. It will enter the
- first module containing whatever network-specific transforma-
- tions that were necessary to permit migration through the
- "current" network. It then passes through the modules:
-
- o Transformation Reversal
-
- The "current" network's idiosyncracies are removed and
- the message is returned to the canonical form speci-
- fied in this standard.
-
- o Transformation
-
- The "next" network's local idiosyncracies are imposed
- on the message.
-
- ------------------
- From ==> | Remove Net-A |
- Net-A | idiosyncracies |
- ------------------
- ||
- \/
- Conformance
- with standard
- ||
- \/
- ------------------
- | Impose Net-B | ==> To
- | idiosyncracies | Net-B
- ------------------
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 16 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 4. MESSAGE SPECIFICATION
-
- 4.1. SYNTAX
-
- Note: Due to an artifact of the notational conventions, the syn-
- tax indicates that, when present, some fields, must be in
- a particular order. Header fields are NOT required to
- occur in any particular order, except that the message
- body must occur AFTER the headers. It is recommended
- that, if present, headers be sent in the order "Return-
- Path", "Received", "Date", "From", "Subject", "Sender",
- "To", "cc", etc.
-
- This specification permits multiple occurrences of most
- fields. Except as noted, their interpretation is not
- specified here, and their use is discouraged.
-
- The following syntax for the bodies of various fields should
- be thought of as describing each field body as a single long
- string (or line). The "Lexical Analysis of Message" section on
- "Long Header Fields", above, indicates how such long strings can
- be represented on more than one line in the actual transmitted
- message.
-
- message = fields *( CRLF *text ) ; Everything after
- ; first null line
- ; is message body
-
- fields = dates ; Creation time,
- source ; author id & one
- 1*destination ; address required
- *optional-field ; others optional
-
- source = [ trace ] ; net traversals
- originator ; original mail
- [ resent ] ; forwarded
-
- trace = return ; path to sender
- 1*received ; receipt tags
-
- return = "Return-path" ":" route-addr ; return address
-
- received = "Received" ":" ; one per relay
- ["from" domain] ; sending host
- ["by" domain] ; receiving host
- ["via" atom] ; physical path
- *("with" atom) ; link/mail protocol
- ["id" msg-id] ; receiver msg id
- ["for" addr-spec] ; initial form
-
-
- August 13, 1982 - 17 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- ";" date-time ; time received
-
- originator = authentic ; authenticated addr
- [ "Reply-To" ":" 1#address] )
-
- authentic = "From" ":" mailbox ; Single author
- / ( "Sender" ":" mailbox ; Actual submittor
- "From" ":" 1#mailbox) ; Multiple authors
- ; or not sender
-
- resent = resent-authentic
- [ "Resent-Reply-To" ":" 1#address] )
-
- resent-authentic =
- = "Resent-From" ":" mailbox
- / ( "Resent-Sender" ":" mailbox
- "Resent-From" ":" 1#mailbox )
-
- dates = orig-date ; Original
- [ resent-date ] ; Forwarded
-
- orig-date = "Date" ":" date-time
-
- resent-date = "Resent-Date" ":" date-time
-
- destination = "To" ":" 1#address ; Primary
- / "Resent-To" ":" 1#address
- / "cc" ":" 1#address ; Secondary
- / "Resent-cc" ":" 1#address
- / "bcc" ":" #address ; Blind carbon
- / "Resent-bcc" ":" #address
-
- optional-field =
- / "Message-ID" ":" msg-id
- / "Resent-Message-ID" ":" msg-id
- / "In-Reply-To" ":" *(phrase / msg-id)
- / "References" ":" *(phrase / msg-id)
- / "Keywords" ":" #phrase
- / "Subject" ":" *text
- / "Comments" ":" *text
- / "Encrypted" ":" 1#2word
- / extension-field ; To be defined
- / user-defined-field ; May be pre-empted
-
- msg-id = "<" addr-spec ">" ; Unique message id
-
-
-
-
-
-
- August 13, 1982 - 18 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- extension-field =
- <Any field which is defined in a document
- published as a formal extension to this
- specification; none will have names beginning
- with the string "X-">
-
- user-defined-field =
- <Any field which has not been defined
- in this specification or published as an
- extension to this specification; names for
- such fields must be unique and may be
- pre-empted by published extensions>
-
- 4.2. FORWARDING
-
- Some systems permit mail recipients to forward a message,
- retaining the original headers, by adding some new fields. This
- standard supports such a service, through the "Resent-" prefix to
- field names.
-
- Whenever the string "Resent-" begins a field name, the field
- has the same semantics as a field whose name does not have the
- prefix. However, the message is assumed to have been forwarded
- by an original recipient who attached the "Resent-" field. This
- new field is treated as being more recent than the equivalent,
- original field. For example, the "Resent-From", indicates the
- person that forwarded the message, whereas the "From" field indi-
- cates the original author.
-
- Use of such precedence information depends upon partici-
- pants' communication needs. For example, this standard does not
- dictate when a "Resent-From:" address should receive replies, in
- lieu of sending them to the "From:" address.
-
- Note: In general, the "Resent-" fields should be treated as con-
- taining a set of information that is independent of the
- set of original fields. Information for one set should
- not automatically be taken from the other. The interpre-
- tation of multiple "Resent-" fields, of the same type, is
- undefined.
-
- In the remainder of this specification, occurrence of legal
- "Resent-" fields are treated identically with the occurrence of
-
-
-
-
-
-
-
-
- August 13, 1982 - 19 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- fields whose names do not contain this prefix.
-
- 4.3. TRACE FIELDS
-
- Trace information is used to provide an audit trail of mes-
- sage handling. In addition, it indicates a route back to the
- sender of the message.
-
- The list of known "via" and "with" values are registered
- with the Network Information Center, SRI International, Menlo
- Park, California.
-
- 4.3.1. RETURN-PATH
-
- This field is added by the final transport system that
- delivers the message to its recipient. The field is intended
- to contain definitive information about the address and route
- back to the message's originator.
-
- Note: The "Reply-To" field is added by the originator and
- serves to direct replies, whereas the "Return-Path"
- field is used to identify a path back to the origina-
- tor.
-
- While the syntax indicates that a route specification is
- optional, every attempt should be made to provide that infor-
- mation in this field.
-
- 4.3.2. RECEIVED
-
- A copy of this field is added by each transport service that
- relays the message. The information in the field can be quite
- useful for tracing transport problems.
-
- The names of the sending and receiving hosts and time-of-
- receipt may be specified. The "via" parameter may be used, to
- indicate what physical mechanism the message was sent over,
- such as Arpanet or Phonenet, and the "with" parameter may be
- used to indicate the mail-, or connection-, level protocol
- that was used, such as the SMTP mail protocol, or X.25 tran-
- sport protocol.
-
- Note: Several "with" parameters may be included, to fully
- specify the set of protocols that were used.
-
- Some transport services queue mail; the internal message iden-
- tifier that is assigned to the message may be noted, using the
- "id" parameter. When the sending host uses a destination
- address specification that the receiving host reinterprets, by
-
-
- August 13, 1982 - 20 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- expansion or transformation, the receiving host may wish to
- record the original specification, using the "for" parameter.
- For example, when a copy of mail is sent to the member of a
- distribution list, this parameter may be used to record the
- original address that was used to specify the list.
-
- 4.4. ORIGINATOR FIELDS
-
- The standard allows only a subset of the combinations possi-
- ble with the From, Sender, Reply-To, Resent-From, Resent-Sender,
- and Resent-Reply-To fields. The limitation is intentional.
-
- 4.4.1. FROM / RESENT-FROM
-
- This field contains the identity of the person(s) who wished
- this message to be sent. The message-creation process should
- default this field to be a single, authenticated machine
- address, indicating the AGENT (person, system or process)
- entering the message. If this is not done, the "Sender" field
- MUST be present. If the "From" field IS defaulted this way,
- the "Sender" field is optional and is redundant with the
- "From" field. In all cases, addresses in the "From" field
- must be machine-usable (addr-specs) and may not contain named
- lists (groups).
-
- 4.4.2. SENDER / RESENT-SENDER
-
- This field contains the authenticated identity of the AGENT
- (person, system or process) that sends the message. It is
- intended for use when the sender is not the author of the mes-
- sage, or to indicate who among a group of authors actually
- sent the message. If the contents of the "Sender" field would
- be completely redundant with the "From" field, then the
- "Sender" field need not be present and its use is discouraged
- (though still legal). In particular, the "Sender" field MUST
- be present if it is NOT the same as the "From" Field.
-
- The Sender mailbox specification includes a word sequence
- which must correspond to a specific agent (i.e., a human user
- or a computer program) rather than a standard address. This
- indicates the expectation that the field will identify the
- single AGENT (person, system, or process) responsible for
- sending the mail and not simply include the name of a mailbox
- from which the mail was sent. For example in the case of a
- shared login name, the name, by itself, would not be adequate.
- The local-part address unit, which refers to this agent, is
- expected to be a computer system term, and not (for example) a
- generalized person reference which can be used outside the
- network text message context.
-
-
- August 13, 1982 - 21 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- Since the critical function served by the "Sender" field is
- identification of the agent responsible for sending mail and
- since computer programs cannot be held accountable for their
- behavior, it is strongly recommended that when a computer pro-
- gram generates a message, the HUMAN who is responsible for
- that program be referenced as part of the "Sender" field mail-
- box specification.
-
- 4.4.3. REPLY-TO / RESENT-REPLY-TO
-
- This field provides a general mechanism for indicating any
- mailbox(es) to which responses are to be sent. Three typical
- uses for this feature can be distinguished. In the first
- case, the author(s) may not have regular machine-based mail-
- boxes and therefore wish(es) to indicate an alternate machine
- address. In the second case, an author may wish additional
- persons to be made aware of, or responsible for, replies. A
- somewhat different use may be of some help to "text message
- teleconferencing" groups equipped with automatic distribution
- services: include the address of that service in the "Reply-
- To" field of all messages submitted to the teleconference;
- then participants can "reply" to conference submissions to
- guarantee the correct distribution of any submission of their
- own.
-
- Note: The "Return-Path" field is added by the mail transport
- service, at the time of final deliver. It is intended
- to identify a path back to the orginator of the mes-
- sage. The "Reply-To" field is added by the message
- originator and is intended to direct replies.
-
- 4.4.4. AUTOMATIC USE OF FROM / SENDER / REPLY-TO
-
- For systems which automatically generate address lists for
- replies to messages, the following recommendations are made:
-
- o The "Sender" field mailbox should be sent notices of
- any problems in transport or delivery of the original
- messages. If there is no "Sender" field, then the
- "From" field mailbox should be used.
-
- o The "Sender" field mailbox should NEVER be used
- automatically, in a recipient's reply message.
-
- o If the "Reply-To" field exists, then the reply should
- go to the addresses indicated in that field and not to
- the address(es) indicated in the "From" field.
-
-
-
-
- August 13, 1982 - 22 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- o If there is a "From" field, but no "Reply-To" field,
- the reply should be sent to the address(es) indicated
- in the "From" field.
-
- Sometimes, a recipient may actually wish to communicate with
- the person that initiated the message transfer. In such
- cases, it is reasonable to use the "Sender" address.
-
- This recommendation is intended only for automated use of
- originator-fields and is not intended to suggest that replies
- may not also be sent to other recipients of messages. It is
- up to the respective mail-handling programs to decide what
- additional facilities will be provided.
-
- Examples are provided in Appendix A.
-
- 4.5. RECEIVER FIELDS
-
- 4.5.1. TO / RESENT-TO
-
- This field contains the identity of the primary recipients of
- the message.
-
- 4.5.2. CC / RESENT-CC
-
- This field contains the identity of the secondary (informa-
- tional) recipients of the message.
-
- 4.5.3. BCC / RESENT-BCC
-
- This field contains the identity of additional recipients of
- the message. The contents of this field are not included in
- copies of the message sent to the primary and secondary reci-
- pients. Some systems may choose to include the text of the
- "Bcc" field only in the author(s)'s copy, while others may
- also include it in the text sent to all those indicated in the
- "Bcc" list.
-
- 4.6. REFERENCE FIELDS
-
- 4.6.1. MESSAGE-ID / RESENT-MESSAGE-ID
-
- This field contains a unique identifier (the local-part
- address unit) which refers to THIS version of THIS message.
- The uniqueness of the message identifier is guaranteed by the
- host which generates it. This identifier is intended to be
- machine readable and not necessarily meaningful to humans. A
- message identifier pertains to exactly one instantiation of a
- particular message; subsequent revisions to the message should
-
-
- August 13, 1982 - 23 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- each receive new message identifiers.
-
- 4.6.2. IN-REPLY-TO
-
- The contents of this field identify previous correspon-
- dence which this message answers. Note that if message iden-
- tifiers are used in this field, they must use the msg-id
- specification format.
-
- 4.6.3. REFERENCES
-
- The contents of this field identify other correspondence
- which this message references. Note that if message identif-
- iers are used, they must use the msg-id specification format.
-
- 4.6.4. KEYWORDS
-
- This field contains keywords or phrases, separated by
- commas.
-
- 4.7. OTHER FIELDS
-
- 4.7.1. SUBJECT
-
- This is intended to provide a summary, or indicate the
- nature, of the message.
-
- 4.7.2. COMMENTS
-
- Permits adding text comments onto the message without
- disturbing the contents of the message's body.
-
- 4.7.3. ENCRYPTED
-
- Sometimes, data encryption is used to increase the
- privacy of message contents. If the body of a message has
- been encrypted, to keep its contents private, the "Encrypted"
- field can be used to note the fact and to indicate the nature
- of the encryption. The first <word> parameter indicates the
- software used to encrypt the body, and the second, optional
- <word> is intended to aid the recipient in selecting the
- proper decryption key. This code word may be viewed as an
- index to a table of keys held by the recipient.
-
- Note: Unfortunately, headers must contain envelope, as well
- as contents, information. Consequently, it is neces-
- sary that they remain unencrypted, so that mail tran-
- sport services may access them. Since names,
- addresses, and "Subject" field contents may contain
-
-
- August 13, 1982 - 24 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- sensitive information, this requirement limits total
- message privacy.
-
- Names of encryption software are registered with the Net-
- work Information Center, SRI International, Menlo Park, Cali-
- fornia.
-
- 4.7.4. EXTENSION-FIELD
-
- A limited number of common fields have been defined in
- this document. As network mail requirements dictate, addi-
- tional fields may be standardized. To provide user-defined
- fields with a measure of safety, in name selection, such
- extension-fields will never have names that begin with the
- string "X-".
-
- Names of Extension-fields are registered with the Network
- Information Center, SRI International, Menlo Park, California.
-
- 4.7.5. USER-DEFINED-FIELD
-
- Individual users of network mail are free to define and
- use additional header fields. Such fields must have names
- which are not already used in the current specification or in
- any definitions of extension-fields, and the overall syntax of
- these user-defined-fields must conform to this specification's
- rules for delimiting and folding fields. Due to the
- extension-field publishing process, the name of a user-
- defined-field may be pre-empted
-
- Note: The prefatory string "X-" will never be used in the
- names of Extension-fields. This provides user-defined
- fields with a protected set of names.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 25 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 5. DATE AND TIME SPECIFICATION
-
- 5.1. SYNTAX
-
- date-time = [ day "," ] date time ; dd mm yy
- ; hh:mm:ss zzz
-
- day = "Mon" / "Tue" / "Wed" / "Thu"
- / "Fri" / "Sat" / "Sun"
-
- date = 1*2DIGIT month 2DIGIT ; day month year
- ; e.g. 20 Jun 82
-
- month = "Jan" / "Feb" / "Mar" / "Apr"
- / "May" / "Jun" / "Jul" / "Aug"
- / "Sep" / "Oct" / "Nov" / "Dec"
-
- time = hour zone ; ANSI and Military
-
- hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT]
- ; 00:00:00 - 23:59:59
-
- zone = "UT" / "GMT" ; Universal Time
- ; North American : UT
- / "EST" / "EDT" ; Eastern: - 5/ - 4
- / "CST" / "CDT" ; Central: - 6/ - 5
- / "MST" / "MDT" ; Mountain: - 7/ - 6
- / "PST" / "PDT" ; Pacific: - 8/ - 7
- / 1ALPHA ; Military: Z = UT;
- ; A:-1; (J not used)
- ; M:-12; N:+1; Y:+12
- / ( ("+" / "-") 4DIGIT ) ; Local differential
- ; hours+min. (HHMM)
-
- 5.2. SEMANTICS
-
- If included, day-of-week must be the day implied by the date
- specification.
-
- Time zone may be indicated in several ways. "UT" is Univer-
- sal Time (formerly called "Greenwich Mean Time"); "GMT" is per-
- mitted as a reference to Universal Time. The military standard
- uses a single character for each zone. "Z" is Universal Time.
- "A" indicates one hour earlier, and "M" indicates 12 hours ear-
- lier; "N" is one hour later, and "Y" is 12 hours later. The
- letter "J" is not used. The other remaining two forms are taken
- from ANSI standard X3.51-1975. One allows explicit indication of
- the amount of offset from UT; the other uses common 3-character
- strings for indicating time zones in North America.
-
-
- August 13, 1982 - 26 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 6. ADDRESS SPECIFICATION
-
- 6.1. SYNTAX
-
- address = mailbox ; one addressee
- / group ; named list
-
- group = phrase ":" [#mailbox] ";"
-
- mailbox = addr-spec ; simple address
- / phrase route-addr ; name & addr-spec
-
- route-addr = "<" [route] addr-spec ">"
-
- route = 1#("@" domain) ":" ; path-relative
-
- addr-spec = local-part "@" domain ; global address
-
- local-part = word *("." word) ; uninterpreted
- ; case-preserved
-
- domain = sub-domain *("." sub-domain)
-
- sub-domain = domain-ref / domain-literal
-
- domain-ref = atom ; symbolic reference
-
- 6.2. SEMANTICS
-
- A mailbox receives mail. It is a conceptual entity which
- does not necessarily pertain to file storage. For example, some
- sites may choose to print mail on their line printer and deliver
- the output to the addressee's desk.
-
- A mailbox specification comprises a person, system or pro-
- cess name reference, a domain-dependent string, and a name-domain
- reference. The name reference is optional and is usually used to
- indicate the human name of a recipient. The name-domain refer-
- ence specifies a sequence of sub-domains. The domain-dependent
- string is uninterpreted, except by the final sub-domain; the rest
- of the mail service merely transmits it as a literal string.
-
- 6.2.1. DOMAINS
-
- A name-domain is a set of registered (mail) names. A name-
- domain specification resolves to a subordinate name-domain
- specification or to a terminal domain-dependent string.
- Hence, domain specification is extensible, permitting any
- number of registration levels.
-
-
- August 13, 1982 - 27 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- Name-domains model a global, logical, hierarchical addressing
- scheme. The model is logical, in that an address specifica-
- tion is related to name registration and is not necessarily
- tied to transmission path. The model's hierarchy is a
- directed graph, called an in-tree, such that there is a single
- path from the root of the tree to any node in the hierarchy.
- If more than one path actually exists, they are considered to
- be different addresses.
-
- The root node is common to all addresses; consequently, it is
- not referenced. Its children constitute "top-level" name-
- domains. Usually, a service has access to its own full domain
- specification and to the names of all top-level name-domains.
-
- The "top" of the domain addressing hierarchy -- a child of the
- root -- is indicated by the right-most field, in a domain
- specification. Its child is specified to the left, its child
- to the left, and so on.
-
- Some groups provide formal registration services; these con-
- stitute name-domains that are independent logically of
- specific machines. In addition, networks and machines impli-
- citly compose name-domains, since their membership usually is
- registered in name tables.
-
- In the case of formal registration, an organization implements
- a (distributed) data base which provides an address-to-route
- mapping service for addresses of the form:
-
- person@registry.organization
-
- Note that "organization" is a logical entity, separate from
- any particular communication network.
-
- A mechanism for accessing "organization" is universally avail-
- able. That mechanism, in turn, seeks an instantiation of the
- registry; its location is not indicated in the address specif-
- ication. It is assumed that the system which operates under
- the name "organization" knows how to find a subordinate regis-
- try. The registry will then use the "person" string to deter-
- mine where to send the mail specification.
-
- The latter, network-oriented case permits simple, direct,
- attachment-related address specification, such as:
-
- user@host.network
-
- Once the network is accessed, it is expected that a message
- will go directly to the host and that the host will resolve
-
-
- August 13, 1982 - 28 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- the user name, placing the message in the user's mailbox.
-
- 6.2.2. ABBREVIATED DOMAIN SPECIFICATION
-
- Since any number of levels is possible within the domain
- hierarchy, specification of a fully qualified address can
- become inconvenient. This standard permits abbreviated domain
- specification, in a special case:
-
- For the address of the sender, call the left-most
- sub-domain Level N. In a header address, if all of
- the sub-domains above (i.e., to the right of) Level N
- are the same as those of the sender, then they do not
- have to appear in the specification. Otherwise, the
- address must be fully qualified.
-
- This feature is subject to approval by local sub-
- domains. Individual sub-domains may require their
- member systems, which originate mail, to provide full
- domain specification only. When permitted, abbrevia-
- tions may be present only while the message stays
- within the sub-domain of the sender.
-
- Use of this mechanism requires the sender's sub-domain
- to reserve the names of all top-level domains, so that
- full specifications can be distinguished from abbrevi-
- ated specifications.
-
- For example, if a sender's address is:
-
- sender@registry-A.registry-1.organization-X
-
- and one recipient's address is:
-
- recipient@registry-B.registry-1.organization-X
-
- and another's is:
-
- recipient@registry-C.registry-2.organization-X
-
- then ".registry-1.organization-X" need not be specified in the
- the message, but "registry-C.registry-2" DOES have to be
- specified. That is, the first two addresses may be abbrevi-
- ated, but the third address must be fully specified.
-
- When a message crosses a domain boundary, all addresses must
- be specified in the full format, ending with the top-level
- name-domain in the right-most field. It is the responsibility
- of mail forwarding services to ensure that addresses conform
-
-
- August 13, 1982 - 29 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- with this requirement. In the case of abbreviated addresses,
- the relaying service must make the necessary expansions. It
- should be noted that it often is difficult for such a service
- to locate all occurrences of address abbreviations. For exam-
- ple, it will not be possible to find such abbreviations within
- the body of the message. The "Return-Path" field can aid
- recipients in recovering from these errors.
-
- Note: When passing any portion of an addr-spec onto a process
- which does not interpret data according to this stan-
- dard (e.g., mail protocol servers). There must be NO
- LWSP-chars preceding or following the at-sign or any
- delimiting period ("."), such as shown in the above
- examples, and only ONE SPACE between contiguous
- <word>s.
-
- 6.2.3. DOMAIN TERMS
-
- A domain-ref must be THE official name of a registry, network,
- or host. It is a symbolic reference, within a name sub-
- domain. At times, it is necessary to bypass standard mechan-
- isms for resolving such references, using more primitive
- information, such as a network host address rather than its
- associated host name.
-
- To permit such references, this standard provides the domain-
- literal construct. Its contents must conform with the needs
- of the sub-domain in which it is interpreted.
-
- Domain-literals which refer to domains within the ARPA Inter-
- net specify 32-bit Internet addresses, in four 8-bit fields
- noted in decimal, as described in Request for Comments #820,
- "Assigned Numbers." For example:
-
- [10.0.3.19]
-
- Note: THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED. It
- is permitted only as a means of bypassing temporary
- system limitations, such as name tables which are not
- complete.
-
- The names of "top-level" domains, and the names of domains
- under in the ARPA Internet, are registered with the Network
- Information Center, SRI International, Menlo Park, California.
-
- 6.2.4. DOMAIN-DEPENDENT LOCAL STRING
-
- The local-part of an addr-spec in a mailbox specification
- (i.e., the host's name for the mailbox) is understood to be
-
-
- August 13, 1982 - 30 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- whatever the receiving mail protocol server allows. For exam-
- ple, some systems do not understand mailbox references of the
- form "P. D. Q. Bach", but others do.
-
- This specification treats periods (".") as lexical separators.
- Hence, their presence in local-parts which are not quoted-
- strings, is detected. However, such occurrences carry NO
- semantics. That is, if a local-part has periods within it, an
- address parser will divide the local-part into several tokens,
- but the sequence of tokens will be treated as one uninter-
- preted unit. The sequence will be re-assembled, when the
- address is passed outside of the system such as to a mail pro-
- tocol service.
-
- For example, the address:
-
- First.Last@Registry.Org
-
- is legal and does not require the local-part to be surrounded
- with quotation-marks. (However, "First Last" DOES require
- quoting.) The local-part of the address, when passed outside
- of the mail system, within the Registry.Org domain, is
- "First.Last", again without quotation marks.
-
- 6.2.5. BALANCING LOCAL-PART AND DOMAIN
-
- In some cases, the boundary between local-part and domain can
- be flexible. The local-part may be a simple string, which is
- used for the final determination of the recipient's mailbox.
- All other levels of reference are, therefore, part of the
- domain.
-
- For some systems, in the case of abbreviated reference to the
- local and subordinate sub-domains, it may be possible to
- specify only one reference within the domain part and place
- the other, subordinate name-domain references within the
- local-part. This would appear as:
-
- mailbox.sub1.sub2@this-domain
-
- Such a specification would be acceptable to address parsers
- which conform to RFC #733, but do not support this newer
- Internet standard. While contrary to the intent of this stan-
- dard, the form is legal.
-
- Also, some sub-domains have a specification syntax which does
- not conform to this standard. For example:
-
- sub-net.mailbox@sub-domain.domain
-
-
- August 13, 1982 - 31 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- uses a different parsing sequence for local-part than for
- domain.
-
- Note: As a rule, the domain specification should contain
- fields which are encoded according to the syntax of
- this standard and which contain generally-standardized
- information. The local-part specification should con-
- tain only that portion of the address which deviates
- from the form or intention of the domain field.
-
- 6.2.6. MULTIPLE MAILBOXES
-
- An individual may have several mailboxes and wish to receive
- mail at whatever mailbox is convenient for the sender to
- access. This standard does not provide a means of specifying
- "any member of" a list of mailboxes.
-
- A set of individuals may wish to receive mail as a single unit
- (i.e., a distribution list). The <group> construct permits
- specification of such a list. Recipient mailboxes are speci-
- fied within the bracketed part (":" - ";"). A copy of the
- transmitted message is to be sent to each mailbox listed.
- This standard does not permit recursive specification of
- groups within groups.
-
- While a list must be named, it is not required that the con-
- tents of the list be included. In this case, the <address>
- serves only as an indication of group distribution and would
- appear in the form:
-
- name:;
-
- Some mail services may provide a group-list distribution
- facility, accepting a single mailbox reference, expanding it
- to the full distribution list, and relaying the mail to the
- list's members. This standard provides no additional syntax
- for indicating such a service. Using the <group> address
- alternative, while listing one mailbox in it, can mean either
- that the mailbox reference will be expanded to a list or that
- there is a group with one member.
-
- 6.2.7. EXPLICIT PATH SPECIFICATION
-
- At times, a message originator may wish to indicate the
- transmission path that a message should follow. This is
- called source routing. The normal addressing scheme, used in
- an addr-spec, is carefully separated from such information;
- the <route> portion of a route-addr is provided for such occa-
- sions. It specifies the sequence of hosts and/or transmission
-
-
- August 13, 1982 - 32 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- services that are to be traversed. Both domain-refs and
- domain-literals may be used.
-
- Note: The use of source routing is discouraged. Unless the
- sender has special need of path restriction, the choice
- of transmission route should be left to the mail tran-
- sport service.
-
- 6.3. RESERVED ADDRESS
-
- It often is necessary to send mail to a site, without know-
- ing any of its valid addresses. For example, there may be mail
- system dysfunctions, or a user may wish to find out a person's
- correct address, at that site.
-
- This standard specifies a single, reserved mailbox address
- (local-part) which is to be valid at each site. Mail sent to
- that address is to be routed to a person responsible for the
- site's mail system or to a person with responsibility for general
- site operation. The name of the reserved local-part address is:
-
- Postmaster
-
- so that "Postmaster@domain" is required to be valid.
-
- Note: This reserved local-part must be matched without sensi-
- tivity to alphabetic case, so that "POSTMASTER", "postmas-
- ter", and even "poStmASteR" is to be accepted.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 33 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- 7. BIBLIOGRAPHY
-
-
- ANSI. "USA Standard Code for Information Interchange," X3.4.
- American National Standards Institute: New York (1968). Also
- in: Feinler, E. and J. Postel, eds., "ARPANET Protocol Hand-
- book", NIC 7104.
-
- ANSI. "Representations of Universal Time, Local Time Differen-
- tials, and United States Time Zone References for Information
- Interchange," X3.51-1975. American National Standards Insti-
- tute: New York (1975).
-
- Bemer, R.W., "Time and the Computer." In: Interface Age (Feb.
- 1979).
-
- Bennett, C.J. "JNT Mail Protocol". Joint Network Team, Ruther-
- ford and Appleton Laboratory: Didcot, England.
-
- Bhushan, A.K., Pogran, K.T., Tomlinson, R.S., and White, J.E.
- "Standardizing Network Mail Headers," ARPANET Request for
- Comments No. 561, Network Information Center No. 18516; SRI
- International: Menlo Park (September 1973).
-
- Birrell, A.D., Levin, R., Needham, R.M., and Schroeder, M.D.
- "Grapevine: An Exercise in Distributed Computing," Communica-
- tions of the ACM 25, 4 (April 1982), 260-274.
-
- Crocker, D.H., Vittal, J.J., Pogran, K.T., Henderson, D.A.
- "Standard for the Format of ARPA Network Text Message,"
- ARPANET Request for Comments No. 733, Network Information
- Center No. 41952. SRI International: Menlo Park (November
- 1977).
-
- Feinler, E.J. and Postel, J.B. ARPANET Protocol Handbook, Net-
- work Information Center No. 7104 (NTIS AD A003890). SRI
- International: Menlo Park (April 1976).
-
- Harary, F. "Graph Theory". Addison-Wesley: Reading, Mass.
- (1969).
-
- Levin, R. and Schroeder, M. "Transport of Electronic Messages
- through a Network," TeleInformatics 79, pp. 29-33. North
- Holland (1979). Also as Xerox Palo Alto Research Center
- Technical Report CSL-79-4.
-
- Myer, T.H. and Henderson, D.A. "Message Transmission Protocol,"
- ARPANET Request for Comments, No. 680, Network Information
- Center No. 32116. SRI International: Menlo Park (1975).
-
-
- August 13, 1982 - 34 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- NBS. "Specification of Message Format for Computer Based Message
- Systems, Recommended Federal Information Processing Standard."
- National Bureau of Standards: Gaithersburg, Maryland
- (October 1981).
-
- NIC. Internet Protocol Transition Workbook. Network Information
- Center, SRI-International, Menlo Park, California (March
- 1982).
-
- Oppen, D.C. and Dalal, Y.K. "The Clearinghouse: A Decentralized
- Agent for Locating Named Objects in a Distributed Environ-
- ment," OPD-T8103. Xerox Office Products Division: Palo Alto,
- CA. (October 1981).
-
- Postel, J.B. "Assigned Numbers," ARPANET Request for Comments,
- No. 820. SRI International: Menlo Park (August 1982).
-
- Postel, J.B. "Simple Mail Transfer Protocol," ARPANET Request
- for Comments, No. 821. SRI International: Menlo Park (August
- 1982).
-
- Shoch, J.F. "Internetwork naming, addressing and routing," in
- Proc. 17th IEEE Computer Society International Conference, pp.
- 72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C.
-
- Su, Z. and Postel, J. "The Domain Naming Convention for Internet
- User Applications," ARPANET Request for Comments, No. 819.
- SRI International: Menlo Park (August 1982).
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 35 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- APPENDIX
-
-
- A. EXAMPLES
-
- A.1. ADDRESSES
-
- A.1.1. Alfred Neuman <Neuman@BBN-TENEXA>
-
- A.1.2. Neuman@BBN-TENEXA
-
- These two "Alfred Neuman" examples have identical seman-
- tics, as far as the operation of the local host's mail sending
- (distribution) program (also sometimes called its "mailer")
- and the remote host's mail protocol server are concerned. In
- the first example, the "Alfred Neuman" is ignored by the
- mailer, as "Neuman@BBN-TENEXA" completely specifies the reci-
- pient. The second example contains no superfluous informa-
- tion, and, again, "Neuman@BBN-TENEXA" is the intended reci-
- pient.
-
- Note: When the message crosses name-domain boundaries, then
- these specifications must be changed, so as to indicate
- the remainder of the hierarchy, starting with the top
- level.
-
- A.1.3. "George, Ted" <Shared@Group.Arpanet>
-
- This form might be used to indicate that a single mailbox
- is shared by several users. The quoted string is ignored by
- the originating host's mailer, because "Shared@Group.Arpanet"
- completely specifies the destination mailbox.
-
- A.1.4. Wilt . (the Stilt) Chamberlain@NBA.US
-
- The "(the Stilt)" is a comment, which is NOT included in
- the destination mailbox address handed to the originating
- system's mailer. The local-part of the address is the string
- "Wilt.Chamberlain", with NO space between the first and second
- words.
-
- A.1.5. Address Lists
-
- Gourmets: Pompous Person <WhoZiWhatZit@Cordon-Bleu>,
- Childs@WGBH.Boston, Galloping Gourmet@
- ANT.Down-Under (Australian National Television),
- Cheapie@Discount-Liquors;,
- Cruisers: Port@Portugal, Jones@SEA;,
- Another@Somewhere.SomeOrg
-
-
- August 13, 1982 - 36 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- This group list example points out the use of comments and the
- mixing of addresses and groups.
-
- A.2. ORIGINATOR ITEMS
-
- A.2.1. Author-sent
-
- George Jones logs into his host as "Jones". He sends
- mail himself.
-
- From: Jones@Group.Org
-
- or
-
- From: George Jones <Jones@Group.Org>
-
- A.2.2. Secretary-sent
-
- George Jones logs in as Jones on his host. His secre-
- tary, who logs in as Secy sends mail for him. Replies to the
- mail should go to George.
-
- From: George Jones <Jones@Group>
- Sender: Secy@Other-Group
-
- A.2.3. Secretary-sent, for user of shared directory
-
- George Jones' secretary sends mail for George. Replies
- should go to George.
-
- From: George Jones<Shared@Group.Org>
- Sender: Secy@Other-Group
-
- Note that there need not be a space between "Jones" and the
- "<", but adding a space enhances readability (as is the case
- in other examples.
-
- A.2.4. Committee activity, with one author
-
- George is a member of a committee. He wishes to have any
- replies to his message go to all committee members.
-
- From: George Jones <Jones@Host.Net>
- Sender: Jones@Host
- Reply-To: The Committee: Jones@Host.Net,
- Smith@Other.Org,
- Doe@Somewhere-Else;
-
- Note that if George had not included himself in the
-
-
- August 13, 1982 - 37 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- enumeration of The Committee, he would not have gotten an
- implicit reply; the presence of the "Reply-to" field SUPER-
- SEDES the sending of a reply to the person named in the "From"
- field.
-
- A.2.5. Secretary acting as full agent of author
-
- George Jones asks his secretary (Secy@Host) to send a
- message for him in his capacity as Group. He wants his secre-
- tary to handle all replies.
-
- From: George Jones <Group@Host>
- Sender: Secy@Host
- Reply-To: Secy@Host
-
- A.2.6. Agent for user without online mailbox
-
- A friend of George's, Sarah, is visiting. George's
- secretary sends some mail to a friend of Sarah in computer-
- land. Replies should go to George, whose mailbox is Jones at
- Registry.
-
- From: Sarah Friendly <Secy@Registry>
- Sender: Secy-Name <Secy@Registry>
- Reply-To: Jones@Registry.
-
- A.2.7. Agent for member of a committee
-
- George's secretary sends out a message which was authored
- jointly by all the members of a committee. Note that the name
- of the committee cannot be specified, since <group> names are
- not permitted in the From field.
-
- From: Jones@Host,
- Smith@Other-Host,
- Doe@Somewhere-Else
- Sender: Secy@SHost
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 38 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- A.3. COMPLETE HEADERS
-
- A.3.1. Minimum required
-
- Date: 26 Aug 76 1429 EDT Date: 26 Aug 76 1429 EDT
- From: Jones@Registry.Org or From: Jones@Registry.Org
- Bcc: To: Smith@Registry.Org
-
- Note that the "Bcc" field may be empty, while the "To" field
- is required to have at least one address.
-
- A.3.2. Using some of the additional fields
-
- Date: 26 Aug 76 1430 EDT
- From: George Jones<Group@Host>
- Sender: Secy@SHOST
- To: "Al Neuman"@Mad-Host,
- Sam.Irving@Other-Host
- Message-ID: <some.string@SHOST>
-
- A.3.3. About as complex as you're going to get
-
- Date : 27 Aug 76 0932 PDT
- From : Ken Davis <KDavis@This-Host.This-net>
- Subject : Re: The Syntax in the RFC
- Sender : KSecy@Other-Host
- Reply-To : Sam.Irving@Reg.Organization
- To : George Jones <Group@Some-Reg.An-Org>,
- Al.Neuman@MAD.Publisher
- cc : Important folk:
- Tom Softwood <Balsa@Tree.Root>,
- "Sam Irving"@Other-Host;,
- Standard Distribution:
- /main/davis/people/standard@Other-Host,
- "<Jones>standard.dist.3"@Tops-20-Host>;
- Comment : Sam is away on business. He asked me to handle
- his mail for him. He'll be able to provide a
- more accurate explanation when he returns
- next week.
- In-Reply-To: <some.string@DBM.Group>, George's message
- X-Special-action: This is a sample of user-defined field-
- names. There could also be a field-name
- "Special-action", but its name might later be
- preempted
- Message-ID: <4231.629.XYzi-What@Other-Host>
-
-
-
-
-
-
- August 13, 1982 - 39 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- B. SIMPLE FIELD PARSING
-
- Some mail-reading software systems may wish to perform only
- minimal processing, ignoring the internal syntax of structured
- field-bodies and treating them the same as unstructured-field-
- bodies. Such software will need only to distinguish:
-
- o Header fields from the message body,
-
- o Beginnings of fields from lines which continue fields,
-
- o Field-names from field-contents.
-
- The abbreviated set of syntactic rules which follows will
- suffice for this purpose. It describes a limited view of mes-
- sages and is a subset of the syntactic rules provided in the main
- part of this specification. One small exception is that the con-
- tents of field-bodies consist only of text:
-
- B.1. SYNTAX
-
-
- message = *field *(CRLF *text)
-
- field = field-name ":" [field-body] CRLF
-
- field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
-
- field-body = *text [CRLF LWSP-char field-body]
-
-
- B.2. SEMANTICS
-
- Headers occur before the message body and are terminated by
- a null line (i.e., two contiguous CRLFs).
-
- A line which continues a header field begins with a SPACE or
- HTAB character, while a line beginning a field starts with a
- printable character which is not a colon.
-
- A field-name consists of one or more printable characters
- (excluding colon, space, and control-characters). A field-name
- MUST be contained on one line. Upper and lower case are not dis-
- tinguished when comparing field-names.
-
-
-
-
-
-
-
- August 13, 1982 - 40 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- C. DIFFERENCES FROM RFC #733
-
- The following summarizes the differences between this stan-
- dard and the one specified in Arpanet Request for Comments #733,
- "Standard for the Format of ARPA Network Text Messages". The
- differences are listed in the order of their occurrence in the
- current specification.
-
- C.1. FIELD DEFINITIONS
-
- C.1.1. FIELD NAMES
-
- These now must be a sequence of printable characters. They
- may not contain any LWSP-chars.
-
- C.2. LEXICAL TOKENS
-
- C.2.1. SPECIALS
-
- The characters period ("."), left-square bracket ("["), and
- right-square bracket ("]") have been added. For presentation
- purposes, and when passing a specification to a system that
- does not conform to this standard, periods are to be contigu-
- ous with their surrounding lexical tokens. No linear-white-
- space is permitted between them. The presence of one LWSP-
- char between other tokens is still directed.
-
- C.2.2. ATOM
-
- Atoms may not contain SPACE.
-
- C.2.3. SPECIAL TEXT
-
- ctext and qtext have had backslash ("\") added to the list of
- prohibited characters.
-
- C.2.4. DOMAINS
-
- The lexical tokens <domain-literal> and <dtext> have been
- added.
-
- C.3. MESSAGE SPECIFICATION
-
- C.3.1. TRACE
-
- The "Return-path:" and "Received:" fields have been specified.
-
-
-
-
-
- August 13, 1982 - 41 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- C.3.2. FROM
-
- The "From" field must contain machine-usable addresses (addr-
- spec). Multiple addresses may be specified, but named-lists
- (groups) may not.
-
- C.3.3. RESENT
-
- The meta-construct of prefacing field names with the string
- "Resent-" has been added, to indicate that a message has been
- forwarded by an intermediate recipient.
-
- C.3.4. DESTINATION
-
- A message must contain at least one destination address field.
- "To" and "CC" are required to contain at least one address.
-
- C.3.5. IN-REPLY-TO
-
- The field-body is no longer a comma-separated list, although a
- sequence is still permitted.
-
- C.3.6. REFERENCE
-
- The field-body is no longer a comma-separated list, although a
- sequence is still permitted.
-
- C.3.7. ENCRYPTED
-
- A field has been specified that permits senders to indicate
- that the body of a message has been encrypted.
-
- C.3.8. EXTENSION-FIELD
-
- Extension fields are prohibited from beginning with the char-
- acters "X-".
-
- C.4. DATE AND TIME SPECIFICATION
-
- C.4.1. SIMPLIFICATION
-
- Fewer optional forms are permitted and the list of three-
- letter time zones has been shortened.
-
- C.5. ADDRESS SPECIFICATION
-
-
-
-
-
-
- August 13, 1982 - 42 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- C.5.1. ADDRESS
-
- The use of quoted-string, and the ":"-atom-":" construct, have
- been removed. An address now is either a single mailbox
- reference or is a named list of addresses. The latter indi-
- cates a group distribution.
-
- C.5.2. GROUPS
-
- Group lists are now required to to have a name. Group lists
- may not be nested.
-
- C.5.3. MAILBOX
-
- A mailbox specification may indicate a person's name, as
- before. Such a named list no longer may specify multiple
- mailboxes and may not be nested.
-
- C.5.4. ROUTE ADDRESSING
-
- Addresses now are taken to be absolute, global specifications,
- independent of transmission paths. The <route> construct has
- been provided, to permit explicit specification of transmis-
- sion path. RFC #733's use of multiple at-signs ("@") was
- intended as a general syntax for indicating routing and/or
- hierarchical addressing. The current standard separates these
- specifications and only one at-sign is permitted.
-
- C.5.5. AT-SIGN
-
- The string " at " no longer is used as an address delimiter.
- Only at-sign ("@") serves the function.
-
- C.5.6. DOMAINS
-
- Hierarchical, logical name-domains have been added.
-
- C.6. RESERVED ADDRESS
-
- The local-part "Postmaster" has been reserved, so that users can
- be guaranteed at least one valid address at a site.
-
-
-
-
-
-
-
-
-
-
- August 13, 1982 - 43 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- D. ALPHABETICAL LISTING OF SYNTAX RULES
-
- address = mailbox ; one addressee
- / group ; named list
- addr-spec = local-part "@" domain ; global address
- ALPHA = <any ASCII alphabetic character>
- ; (101-132, 65.- 90.)
- ; (141-172, 97.-122.)
- atom = 1*<any CHAR except specials, SPACE and CTLs>
- authentic = "From" ":" mailbox ; Single author
- / ( "Sender" ":" mailbox ; Actual submittor
- "From" ":" 1#mailbox) ; Multiple authors
- ; or not sender
- CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
- comment = "(" *(ctext / quoted-pair / comment) ")"
- CR = <ASCII CR, carriage return> ; ( 15, 13.)
- CRLF = CR LF
- ctext = <any CHAR excluding "(", ; => may be folded
- ")", "\" & CR, & including
- linear-white-space>
- CTL = <any ASCII control ; ( 0- 37, 0.- 31.)
- character and DEL> ; ( 177, 127.)
- date = 1*2DIGIT month 2DIGIT ; day month year
- ; e.g. 20 Jun 82
- dates = orig-date ; Original
- [ resent-date ] ; Forwarded
- date-time = [ day "," ] date time ; dd mm yy
- ; hh:mm:ss zzz
- day = "Mon" / "Tue" / "Wed" / "Thu"
- / "Fri" / "Sat" / "Sun"
- delimiters = specials / linear-white-space / comment
- destination = "To" ":" 1#address ; Primary
- / "Resent-To" ":" 1#address
- / "cc" ":" 1#address ; Secondary
- / "Resent-cc" ":" 1#address
- / "bcc" ":" #address ; Blind carbon
- / "Resent-bcc" ":" #address
- DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.)
- domain = sub-domain *("." sub-domain)
- domain-literal = "[" *(dtext / quoted-pair) "]"
- domain-ref = atom ; symbolic reference
- dtext = <any CHAR excluding "[", ; => may be folded
- "]", "\" & CR, & including
- linear-white-space>
- extension-field =
- <Any field which is defined in a document
- published as a formal extension to this
- specification; none will have names beginning
- with the string "X-">
-
-
- August 13, 1982 - 44 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- field = field-name ":" [ field-body ] CRLF
- fields = dates ; Creation time,
- source ; author id & one
- 1*destination ; address required
- *optional-field ; others optional
- field-body = field-body-contents
- [CRLF LWSP-char field-body]
- field-body-contents =
- <the ASCII characters making up the field-body, as
- defined in the following sections, and consisting
- of combinations of atom, quoted-string, and
- specials tokens, or else consisting of texts>
- field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
- group = phrase ":" [#mailbox] ";"
- hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT]
- ; 00:00:00 - 23:59:59
- HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.)
- LF = <ASCII LF, linefeed> ; ( 12, 10.)
- linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE
- ; CRLF => folding
- local-part = word *("." word) ; uninterpreted
- ; case-preserved
- LWSP-char = SPACE / HTAB ; semantics = SPACE
- mailbox = addr-spec ; simple address
- / phrase route-addr ; name & addr-spec
- message = fields *( CRLF *text ) ; Everything after
- ; first null line
- ; is message body
- month = "Jan" / "Feb" / "Mar" / "Apr"
- / "May" / "Jun" / "Jul" / "Aug"
- / "Sep" / "Oct" / "Nov" / "Dec"
- msg-id = "<" addr-spec ">" ; Unique message id
- optional-field =
- / "Message-ID" ":" msg-id
- / "Resent-Message-ID" ":" msg-id
- / "In-Reply-To" ":" *(phrase / msg-id)
- / "References" ":" *(phrase / msg-id)
- / "Keywords" ":" #phrase
- / "Subject" ":" *text
- / "Comments" ":" *text
- / "Encrypted" ":" 1#2word
- / extension-field ; To be defined
- / user-defined-field ; May be pre-empted
- orig-date = "Date" ":" date-time
- originator = authentic ; authenticated addr
- [ "Reply-To" ":" 1#address] )
- phrase = 1*word ; Sequence of words
-
-
-
-
- August 13, 1982 - 45 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- qtext = <any CHAR excepting <">, ; => may be folded
- "\" & CR, and including
- linear-white-space>
- quoted-pair = "\" CHAR ; may quote any char
- quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
- ; quoted chars.
- received = "Received" ":" ; one per relay
- ["from" domain] ; sending host
- ["by" domain] ; receiving host
- ["via" atom] ; physical path
- *("with" atom) ; link/mail protocol
- ["id" msg-id] ; receiver msg id
- ["for" addr-spec] ; initial form
- ";" date-time ; time received
-
- resent = resent-authentic
- [ "Resent-Reply-To" ":" 1#address] )
- resent-authentic =
- = "Resent-From" ":" mailbox
- / ( "Resent-Sender" ":" mailbox
- "Resent-From" ":" 1#mailbox )
- resent-date = "Resent-Date" ":" date-time
- return = "Return-path" ":" route-addr ; return address
- route = 1#("@" domain) ":" ; path-relative
- route-addr = "<" [route] addr-spec ">"
- source = [ trace ] ; net traversals
- originator ; original mail
- [ resent ] ; forwarded
- SPACE = <ASCII SP, space> ; ( 40, 32.)
- specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-
- / "," / ";" / ":" / "\" / <"> ; string, to use
- / "." / "[" / "]" ; within a word.
- sub-domain = domain-ref / domain-literal
- text = <any CHAR, including bare ; => atoms, specials,
- CR & bare LF, but NOT ; comments and
- including CRLF> ; quoted-strings are
- ; NOT recognized.
- time = hour zone ; ANSI and Military
- trace = return ; path to sender
- 1*received ; receipt tags
- user-defined-field =
- <Any field which has not been defined
- in this specification or published as an
- extension to this specification; names for
- such fields must be unique and may be
- pre-empted by published extensions>
- word = atom / quoted-string
-
-
-
-
- August 13, 1982 - 46 - RFC #822
-
-
-
- Standard for ARPA Internet Text Messages
-
-
- zone = "UT" / "GMT" ; Universal Time
- ; North American : UT
- / "EST" / "EDT" ; Eastern: - 5/ - 4
- / "CST" / "CDT" ; Central: - 6/ - 5
- / "MST" / "MDT" ; Mountain: - 7/ - 6
- / "PST" / "PDT" ; Pacific: - 8/ - 7
- / 1ALPHA ; Military: Z = UT;
- <"> = <ASCII quote mark> ; ( 42, 34.)
-
-
-
-
-
-
-
-
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diff --git a/proto/sieve/rfc3028.txt b/proto/sieve/rfc3028.txt
@@ -1,2019 +0,0 @@
-
-
-
-
-
-
-Network Working Group T. Showalter
-Request for Comments: 3028 Mirapoint, Inc.
-Category: Standards Track January 2001
-
-
- Sieve: A Mail Filtering Language
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2001). All Rights Reserved.
-
-Abstract
-
- This document describes a language for filtering e-mail messages at
- time of final delivery. It is designed to be implementable on either
- a mail client or mail server. It is meant to be extensible, simple,
- and independent of access protocol, mail architecture, and operating
- system. It is suitable for running on a mail server where users may
- not be allowed to execute arbitrary programs, such as on black box
- Internet Message Access Protocol (IMAP) servers, as it has no
- variables, loops, or ability to shell out to external programs.
-
-Table of Contents
-
- 1. Introduction ........................................... 3
- 1.1. Conventions Used in This Document ..................... 4
- 1.2. Example mail messages ................................. 4
- 2. Design ................................................. 5
- 2.1. Form of the Language .................................. 5
- 2.2. Whitespace ............................................ 5
- 2.3. Comments .............................................. 6
- 2.4. Literal Data .......................................... 6
- 2.4.1. Numbers ............................................... 6
- 2.4.2. Strings ............................................... 7
- 2.4.2.1. String Lists .......................................... 7
- 2.4.2.2. Headers ............................................... 8
- 2.4.2.3. Addresses ............................................. 8
- 2.4.2.4. MIME Parts ............................................ 9
- 2.5. Tests ................................................. 9
- 2.5.1. Test Lists ............................................ 9
-
-
-
-Showalter Standards Track [Page 1]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- 2.6. Arguments ............................................. 9
- 2.6.1. Positional Arguments .................................. 9
- 2.6.2. Tagged Arguments ...................................... 10
- 2.6.3. Optional Arguments .................................... 10
- 2.6.4. Types of Arguments .................................... 10
- 2.7. String Comparison ..................................... 11
- 2.7.1. Match Type ............................................ 11
- 2.7.2. Comparisons Across Character Sets ..................... 12
- 2.7.3. Comparators ........................................... 12
- 2.7.4. Comparisons Against Addresses ......................... 13
- 2.8. Blocks ................................................ 14
- 2.9. Commands .............................................. 14
- 2.10. Evaluation ............................................ 15
- 2.10.1. Action Interaction .................................... 15
- 2.10.2. Implicit Keep ......................................... 15
- 2.10.3. Message Uniqueness in a Mailbox ....................... 15
- 2.10.4. Limits on Numbers of Actions .......................... 16
- 2.10.5. Extensions and Optional Features ...................... 16
- 2.10.6. Errors ................................................ 17
- 2.10.7. Limits on Execution ................................... 17
- 3. Control Commands ....................................... 17
- 3.1. Control Structure If .................................. 18
- 3.2. Control Structure Require ............................. 19
- 3.3. Control Structure Stop ................................ 19
- 4. Action Commands ........................................ 19
- 4.1. Action reject ......................................... 20
- 4.2. Action fileinto ....................................... 20
- 4.3. Action redirect ....................................... 21
- 4.4. Action keep ........................................... 21
- 4.5. Action discard ........................................ 22
- 5. Test Commands .......................................... 22
- 5.1. Test address .......................................... 23
- 5.2. Test allof ............................................ 23
- 5.3. Test anyof ............................................ 24
- 5.4. Test envelope ......................................... 24
- 5.5. Test exists ........................................... 25
- 5.6. Test false ............................................ 25
- 5.7. Test header ........................................... 25
- 5.8. Test not .............................................. 26
- 5.9. Test size ............................................. 26
- 5.10. Test true ............................................. 26
- 6. Extensibility .......................................... 26
- 6.1. Capability String ..................................... 27
- 6.2. IANA Considerations ................................... 28
- 6.2.1. Template for Capability Registrations ................. 28
- 6.2.2. Initial Capability Registrations ...................... 28
- 6.3. Capability Transport .................................. 29
- 7. Transmission ........................................... 29
-
-
-
-Showalter Standards Track [Page 2]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- 8. Parsing ................................................ 30
- 8.1. Lexical Tokens ........................................ 30
- 8.2. Grammar ............................................... 31
- 9. Extended Example ....................................... 32
- 10. Security Considerations ................................ 34
- 11. Acknowledgments ........................................ 34
- 12. Author's Address ....................................... 34
- 13. References ............................................. 34
- 14. Full Copyright Statement ............................... 36
-
-1. Introduction
-
- This memo documents a language that can be used to create filters for
- electronic mail. It is not tied to any particular operating system or
- mail architecture. It requires the use of [IMAIL]-compliant
- messages, but should otherwise generalize to many systems.
-
- The language is powerful enough to be useful but limited in order to
- allow for a safe server-side filtering system. The intention is to
- make it impossible for users to do anything more complex (and
- dangerous) than write simple mail filters, along with facilitating
- the use of GUIs for filter creation and manipulation. The language is
- not Turing-complete: it provides no way to write a loop or a function
- and variables are not provided.
-
- Scripts written in Sieve are executed during final delivery, when the
- message is moved to the user-accessible mailbox. In systems where
- the MTA does final delivery, such as traditional Unix mail, it is
- reasonable to sort when the MTA deposits mail into the user's
- mailbox.
-
- There are a number of reasons to use a filtering system. Mail
- traffic for most users has been increasing due to increased usage of
- e-mail, the emergence of unsolicited email as a form of advertising,
- and increased usage of mailing lists.
-
- Experience at Carnegie Mellon has shown that if a filtering system is
- made available to users, many will make use of it in order to file
- messages from specific users or mailing lists. However, many others
- did not make use of the Andrew system's FLAMES filtering language
- [FLAMES] due to difficulty in setting it up.
-
- Because of the expectation that users will make use of filtering if
- it is offered and easy to use, this language has been made simple
- enough to allow many users to make use of it, but rich enough that it
- can be used productively. However, it is expected that GUI-based
- editors will be the preferred way of editing filters for a large
- number of users.
-
-
-
-Showalter Standards Track [Page 3]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-1.1. Conventions Used in This Document
-
- In the sections of this document that discuss the requirements of
- various keywords and operators, the following conventions have been
- adopted.
-
- The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and
- "MAY" in this document are to be interpreted as defined in
- [KEYWORDS].
-
- Each section on a command (test, action, or control structure) has a
- line labeled "Syntax:". This line describes the syntax of the
- command, including its name and its arguments. Required arguments
- are listed inside angle brackets ("<" and ">"). Optional arguments
- are listed inside square brackets ("[" and "]"). Each argument is
- followed by its type, so "<key: string>" represents an argument
- called "key" that is a string. Literal strings are represented with
- double-quoted strings. Alternatives are separated with slashes, and
- parenthesis are used for grouping, similar to [ABNF].
-
- In the "Syntax" line, there are three special pieces of syntax that
- are frequently repeated, MATCH-TYPE, COMPARATOR, and ADDRESS-PART.
- These are discussed in sections 2.7.1, 2.7.3, and 2.7.4,
- respectively.
-
- The formal grammar for these commands in section 10 and is the
- authoritative reference on how to construct commands, but the formal
- grammar does not specify the order, semantics, number or types of
- arguments to commands, nor the legal command names. The intent is to
- allow for extension without changing the grammar.
-
-1.2. Example mail messages
-
- The following mail messages will be used throughout this document in
- examples.
-
- Message A
- -----------------------------------------------------------
- Date: Tue, 1 Apr 1997 09:06:31 -0800 (PST)
- From: coyote@desert.example.org
- To: roadrunner@acme.example.com
- Subject: I have a present for you
-
- Look, I'm sorry about the whole anvil thing, and I really
- didn't mean to try and drop it on you from the top of the
- cliff. I want to try to make it up to you. I've got some
- great birdseed over here at my place--top of the line
-
-
-
-
-Showalter Standards Track [Page 4]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- stuff--and if you come by, I'll have it all wrapped up
- for you. I'm really sorry for all the problems I've caused
- for you over the years, but I know we can work this out.
- --
- Wile E. Coyote "Super Genius" coyote@desert.example.org
- -----------------------------------------------------------
-
- Message B
- -----------------------------------------------------------
- From: youcouldberich!@reply-by-postal-mail.invalid
- Sender: b1ff@de.res.example.com
- To: rube@landru.example.edu
- Date: Mon, 31 Mar 1997 18:26:10 -0800
- Subject: $$$ YOU, TOO, CAN BE A MILLIONAIRE! $$$
-
- YOU MAY HAVE ALREADY WON TEN MILLION DOLLARS, BUT I DOUBT
- IT! SO JUST POST THIS TO SIX HUNDRED NEWSGROUPS! IT WILL
- GUARANTEE THAT YOU GET AT LEAST FIVE RESPONSES WITH MONEY!
- MONEY! MONEY! COLD HARD CASH! YOU WILL RECEIVE OVER
- $20,000 IN LESS THAN TWO MONTHS! AND IT'S LEGAL!!!!!!!!!
- !!!!!!!!!!!!!!!!!!111111111!!!!!!!11111111111!!1 JUST
- SEND $5 IN SMALL, UNMARKED BILLS TO THE ADDRESSES BELOW!
- -----------------------------------------------------------
-
-2. Design
-
-2.1. Form of the Language
-
- The language consists of a set of commands. Each command consists of
- a set of tokens delimited by whitespace. The command identifier is
- the first token and it is followed by zero or more argument tokens.
- Arguments may be literal data, tags, blocks of commands, or test
- commands.
-
- The language is represented in UTF-8, as specified in [UTF-8].
-
- Tokens in the ASCII range are considered case-insensitive.
-
-2.2. Whitespace
-
- Whitespace is used to separate tokens. Whitespace is made up of
- tabs, newlines (CRLF, never just CR or LF), and the space character.
- The amount of whitespace used is not significant.
-
-
-
-
-
-
-
-
-Showalter Standards Track [Page 5]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-2.3. Comments
-
- Two types of comments are offered. Comments are semantically
- equivalent to whitespace and can be used anyplace that whitespace is
- (with one exception in multi-line strings, as described in the
- grammar).
-
- Hash comments begin with a "#" character that is not contained within
- a string and continue until the next CRLF.
-
- Example: if size :over 100K { # this is a comment
- discard;
- }
-
- Bracketed comments begin with the token "/*" and end with "*/" outside
- of a string. Bracketed comments may span multiple lines. Bracketed
- comments do not nest.
-
- Example: if size :over 100K { /* this is a comment
- this is still a comment */ discard /* this is a comment
- */ ;
- }
-
-2.4. Literal Data
-
- Literal data means data that is not executed, merely evaluated "as
- is", to be used as arguments to commands. Literal data is limited to
- numbers and strings.
-
-2.4.1. Numbers
-
- Numbers are given as ordinary decimal numbers. However, those
- numbers that have a tendency to be fairly large, such as message
- sizes, MAY have a "K", "M", or "G" appended to indicate a multiple of
- a power of two. To be comparable with the power-of-two-based
- versions of SI units that computers frequently use, K specifies
- kibi-, or 1,024 (2^10) times the value of the number; M specifies
- mebi-, or 1,048,576 (2^20) times the value of the number; and G
- specifies tebi-, or 1,073,741,824 (2^30) times the value of the
- number [BINARY-SI].
-
- Implementations MUST provide 31 bits of magnitude in numbers, but MAY
- provide more.
-
- Only positive integers are permitted by this specification.
-
-
-
-
-
-
-Showalter Standards Track [Page 6]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-2.4.2. Strings
-
- Scripts involve large numbers of strings as they are used for pattern
- matching, addresses, textual bodies, etc. Typically, short quoted
- strings suffice for most uses, but a more convenient form is provided
- for longer strings such as bodies of messages.
-
- A quoted string starts and ends with a single double quote (the <">
- character, ASCII 34). A backslash ("\", ASCII 92) inside of a quoted
- string is followed by either another backslash or a double quote.
- This two-character sequence represents a single backslash or double-
- quote within the string, respectively.
-
- No other characters should be escaped with a single backslash.
-
- An undefined escape sequence (such as "\a" in a context where "a" has
- no special meaning) is interpreted as if there were no backslash (in
- this case, "\a" is just "a").
-
- Non-printing characters such as tabs, CR and LF, and control
- characters are permitted in quoted strings. Quoted strings MAY span
- multiple lines. NUL (ASCII 0) is not allowed in strings.
-
- For entering larger amounts of text, such as an email message, a
- multi-line form is allowed. It starts with the keyword "text:",
- followed by a CRLF, and ends with the sequence of a CRLF, a single
- period, and another CRLF. In order to allow the message to contain
- lines with a single-dot, lines are dot-stuffed. That is, when
- composing a message body, an extra `.' is added before each line
- which begins with a `.'. When the server interprets the script,
- these extra dots are removed. Note that a line that begins with a
- dot followed by a non-dot character is not interpreted dot-stuffed;
- that is, ".foo" is interpreted as ".foo". However, because this is
- potentially ambiguous, scripts SHOULD be properly dot-stuffed so such
- lines do not appear.
-
- Note that a hashed comment or whitespace may occur in between the
- "text:" and the CRLF, but not within the string itself. Bracketed
- comments are not allowed here.
-
-2.4.2.1. String Lists
-
- When matching patterns, it is frequently convenient to match against
- groups of strings instead of single strings. For this reason, a list
- of strings is allowed in many tests, implying that if the test is
- true using any one of the strings, then the test is true.
- Implementations are encouraged to use short-circuit evaluation in
- these cases.
-
-
-
-Showalter Standards Track [Page 7]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- For instance, the test `header :contains ["To", "Cc"]
- ["me@example.com", "me00@landru.example.edu"]' is true if either the
- To header or Cc header of the input message contains either of the
- e-mail addresses "me@example.com" or "me00@landru.example.edu".
-
- Conversely, in any case where a list of strings is appropriate, a
- single string is allowed without being a member of a list: it is
- equivalent to a list with a single member. This means that the test
- `exists "To"' is equivalent to the test `exists ["To"]'.
-
-2.4.2.2. Headers
-
- Headers are a subset of strings. In the Internet Message
- Specification [IMAIL] [RFC1123], each header line is allowed to have
- whitespace nearly anywhere in the line, including after the field
- name and before the subsequent colon. Extra spaces between the
- header name and the ":" in a header field are ignored.
-
- A header name never contains a colon. The "From" header refers to a
- line beginning "From:" (or "From :", etc.). No header will match
- the string "From:" due to the trailing colon.
-
- Folding of long header lines (as described in [IMAIL] 3.4.8) is
- removed prior to interpretation of the data. The folding syntax (the
- CRLF that ends a line plus any leading whitespace at the beginning of
- the next line that indicates folding) are interpreted as if they were
- a single space.
-
-2.4.2.3. Addresses
-
- A number of commands call for email addresses, which are also a
- subset of strings. When these addresses are used in outbound
- contexts, addresses must be compliant with [IMAIL], but are further
- constrained. Using the symbols defined in [IMAIL], section 6.1, the
- syntax of an address is:
-
- sieve-address = addr-spec ; simple address
- / phrase "<" addr-spec ">" ; name & addr-spec
-
- That is, routes and group syntax are not permitted. If multiple
- addresses are required, use a string list. Named groups are not used
- here.
-
- Implementations MUST ensure that the addresses are syntactically
- valid, but need not ensure that they actually identify an email
- recipient.
-
-
-
-
-
-Showalter Standards Track [Page 8]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-2.4.2.4. MIME Parts
-
- In a few places, [MIME] body parts are represented as strings. These
- parts include MIME headers and the body. This provides a way of
- embedding typed data within a Sieve script so that, among other
- things, character sets other than UTF-8 can be used for output
- messages.
-
-2.5. Tests
-
- Tests are given as arguments to commands in order to control their
- actions. In this document, tests are given to if/elsif/else to
- decide which block of code is run.
-
- Tests MUST NOT have side effects. That is, a test cannot affect the
- state of the filter or message. No tests in this specification have
- side effects, and side effects are forbidden in extension tests as
- well.
-
- The rationale for this is that tests with side effects impair
- readability and maintainability and are difficult to represent in a
- graphic interface for generating scripts. Side effects are confined
- to actions where they are clearer.
-
-2.5.1. Test Lists
-
- Some tests ("allof" and "anyof", which implement logical "and" and
- logical "or", respectively) may require more than a single test as an
- argument. The test-list syntax element provides a way of grouping
- tests.
-
- Example: if anyof (not exists ["From", "Date"],
- header :contains "from" "fool@example.edu") {
- discard;
- }
-
-2.6. Arguments
-
- In order to specify what to do, most commands take arguments. There
- are three types of arguments: positional, tagged, and optional.
-
-2.6.1. Positional Arguments
-
- Positional arguments are given to a command which discerns their
- meaning based on their order. When a command takes positional
- arguments, all positional arguments must be supplied and must be in
- the order prescribed.
-
-
-
-
-Showalter Standards Track [Page 9]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-2.6.2. Tagged Arguments
-
- This document provides for tagged arguments in the style of
- CommonLISP. These are also similar to flags given to commands in
- most command-line systems.
-
- A tagged argument is an argument for a command that begins with ":"
- followed by a tag naming the argument, such as ":contains". This
- argument means that zero or more of the next tokens have some
- particular meaning depending on the argument. These next tokens may
- be numbers or strings but they are never blocks.
-
- Tagged arguments are similar to positional arguments, except that
- instead of the meaning being derived from the command, it is derived
- from the tag.
-
- Tagged arguments must appear before positional arguments, but they
- may appear in any order with other tagged arguments. For simplicity
- of the specification, this is not expressed in the syntax definitions
- with commands, but they still may be reordered arbitrarily provided
- they appear before positional arguments. Tagged arguments may be
- mixed with optional arguments.
-
- To simplify this specification, tagged arguments SHOULD NOT take
- tagged arguments as arguments.
-
-2.6.3. Optional Arguments
-
- Optional arguments are exactly like tagged arguments except that they
- may be left out, in which case a default value is implied. Because
- optional arguments tend to result in shorter scripts, they have been
- used far more than tagged arguments.
-
- One particularly noteworthy case is the ":comparator" argument, which
- allows the user to specify which [ACAP] comparator will be used to
- compare two strings, since different languages may impose different
- orderings on UTF-8 [UTF-8] characters.
-
-2.6.4. Types of Arguments
-
- Abstractly, arguments may be literal data, tests, or blocks of
- commands. In this way, an "if" control structure is merely a command
- that happens to take a test and a block as arguments and may execute
- the block of code.
-
- However, this abstraction is ambiguous from a parsing standpoint.
- The grammar in section 9.2 presents a parsable version of this:
- Arguments are string-lists, numbers, and tags, which may be followed
-
-
-
-Showalter Standards Track [Page 10]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- by a test or a test-list, which may be followed by a block of
- commands. No more than one test or test list, nor more than one
- block of commands, may be used, and commands that end with blocks of
- commands do not end with semicolons.
-
-2.7. String Comparison
-
- When matching one string against another, there are a number of ways
- of performing the match operation. These are accomplished with three
- types of matches: an exact match, a substring match, and a wildcard
- glob-style match. These are described below.
-
- In order to provide for matches between character sets and case
- insensitivity, Sieve borrows ACAP's comparator registry.
-
- However, when a string represents the name of a header, the
- comparator is never user-specified. Header comparisons are always
- done with the "i;ascii-casemap" operator, i.e., case-insensitive
- comparisons, because this is the way things are defined in the
- message specification [IMAIL].
-
-2.7.1. Match Type
-
- There are three match types describing the matching used in this
- specification: ":is", ":contains", and ":matches". Match type
- arguments are supplied to those commands which allow them to specify
- what kind of match is to be performed.
-
- These are used as tagged arguments to tests that perform string
- comparison.
-
- The ":contains" match type describes a substring match. If the value
- argument contains the key argument as a substring, the match is true.
- For instance, the string "frobnitzm" contains "frob" and "nit", but
- not "fbm". The null key ("") is contained in all values.
-
- The ":is" match type describes an absolute match; if the contents of
- the first string are absolutely the same as the contents of the
- second string, they match. Only the string "frobnitzm" is the string
- "frobnitzm". The null key ":is" and only ":is" the null value.
-
- The ":matches" version specifies a wildcard match using the
- characters "*" and "?". "*" matches zero or more characters, and "?"
- matches a single character. "?" and "*" may be escaped as "\\?" and
- "\\*" in strings to match against themselves. The first backslash
- escapes the second backslash; together, they escape the "*". This is
- awkward, but it is commonplace in several programming languages that
- use globs and regular expressions.
-
-
-
-Showalter Standards Track [Page 11]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- In order to specify what type of match is supposed to happen,
- commands that support matching take optional tagged arguments
- ":matches", ":is", and ":contains". Commands default to using ":is"
- matching if no match type argument is supplied. Note that these
- modifiers may interact with comparators; in particular, some
- comparators are not suitable for matching with ":contains" or
- ":matches". It is an error to use a comparator with ":contains" or
- ":matches" that is not compatible with it.
-
- It is an error to give more than one of these arguments to a given
- command.
-
- For convenience, the "MATCH-TYPE" syntax element is defined here as
- follows:
-
- Syntax: ":is" / ":contains" / ":matches"
-
-2.7.2. Comparisons Across Character Sets
-
- All Sieve scripts are represented in UTF-8, but messages may involve
- a number of character sets. In order for comparisons to work across
- character sets, implementations SHOULD implement the following
- behavior:
-
- Implementations decode header charsets to UTF-8. Two strings are
- considered equal if their UTF-8 representations are identical.
- Implementations should decode charsets represented in the forms
- specified by [MIME] for both message headers and bodies.
- Implementations must be capable of decoding US-ASCII, ISO-8859-1,
- the ASCII subset of ISO-8859-* character sets, and UTF-8.
-
- If implementations fail to support the above behavior, they MUST
- conform to the following:
-
- No two strings can be considered equal if one contains octets
- greater than 127.
-
-2.7.3. Comparators
-
- In order to allow for language-independent, case-independent matches,
- the match type may be coupled with a comparator name. Comparators
- are described for [ACAP]; a registry is defined for ACAP, and this
- specification uses that registry.
-
- ACAP defines multiple comparator types. Only equality types are used
- in this specification.
-
-
-
-
-
-Showalter Standards Track [Page 12]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- All implementations MUST support the "i;octet" comparator (simply
- compares octets) and the "i;ascii-casemap" comparator (which treats
- uppercase and lowercase characters in the ASCII subset of UTF-8 as
- the same). If left unspecified, the default is "i;ascii-casemap".
-
- Some comparators may not be usable with substring matches; that is,
- they may only work with ":is". It is an error to try and use a
- comparator with ":matches" or ":contains" that is not compatible with
- it.
-
- A comparator is specified by the ":comparator" option with commands
- that support matching. This option is followed by a string providing
- the name of the comparator to be used. For convenience, the syntax
- of a comparator is abbreviated to "COMPARATOR", and (repeated in
- several tests) is as follows:
-
- Syntax: ":comparator" <comparator-name: string>
-
- So in this example,
-
- Example: if header :contains :comparator "i;octet" "Subject"
- "MAKE MONEY FAST" {
- discard;
- }
-
- would discard any message with subjects like "You can MAKE MONEY
- FAST", but not "You can Make Money Fast", since the comparator used
- is case-sensitive.
-
- Comparators other than i;octet and i;ascii-casemap must be declared
- with require, as they are extensions. If a comparator declared with
- require is not known, it is an error, and execution fails. If the
- comparator is not declared with require, it is also an error, even if
- the comparator is supported. (See 2.10.5.)
-
- Both ":matches" and ":contains" match types are compatible with the
- "i;octet" and "i;ascii-casemap" comparators and may be used with
- them.
-
- It is an error to give more than one of these arguments to a given
- command.
-
-2.7.4. Comparisons Against Addresses
-
- Addresses are one of the most frequent things represented as strings.
- These are structured, and being able to compare against the local-
- part or the domain of an address is useful, so some tests that act
-
-
-
-
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-
-
- exclusively on addresses take an additional optional argument that
- specifies what the test acts on.
-
- These optional arguments are ":localpart", ":domain", and ":all",
- which act on the local-part (left-side), the domain part (right-
- side), and the whole address.
-
- The kind of comparison done, such as whether or not the test done is
- case-insensitive, is specified as a comparator argument to the test.
-
- If an optional address-part is omitted, the default is ":all".
-
- It is an error to give more than one of these arguments to a given
- command.
-
- For convenience, the "ADDRESS-PART" syntax element is defined here as
- follows:
-
- Syntax: ":localpart" / ":domain" / ":all"
-
-2.8. Blocks
-
- Blocks are sets of commands enclosed within curly braces. Blocks are
- supplied to commands so that the commands can implement control
- commands.
-
- A control structure is a command that happens to take a test and a
- block as one of its arguments; depending on the result of the test
- supplied as another argument, it runs the code in the block some
- number of times.
-
- With the commands supplied in this memo, there are no loops. The
- control structures supplied--if, elsif, and else--run a block either
- once or not at all. So there are two arguments, the test and the
- block.
-
-2.9. Commands
-
- Sieve scripts are sequences of commands. Commands can take any of
- the tokens above as arguments, and arguments may be either tagged or
- positional arguments. Not all commands take all arguments.
-
- There are three kinds of commands: test commands, action commands,
- and control commands.
-
- The simplest is an action command. An action command is an
- identifier followed by zero or more arguments, terminated by a
- semicolon. Action commands do not take tests or blocks as arguments.
-
-
-
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-
-
- A control command is similar, but it takes a test as an argument, and
- ends with a block instead of a semicolon.
-
- A test command is used as part of a control command. It is used to
- specify whether or not the block of code given to the control command
- is executed.
-
-2.10. Evaluation
-
-2.10.1. Action Interaction
-
- Some actions cannot be used with other actions because the result
- would be absurd. These restrictions are noted throughout this memo.
-
- Extension actions MUST state how they interact with actions defined
- in this specification.
-
-2.10.2. Implicit Keep
-
- Previous experience with filtering systems suggests that cases tend
- to be missed in scripts. To prevent errors, Sieve has an "implicit
- keep".
-
- An implicit keep is a keep action (see 4.4) performed in absence of
- any action that cancels the implicit keep.
-
- An implicit keep is performed if a message is not written to a
- mailbox, redirected to a new address, or explicitly thrown out. That
- is, if a fileinto, a keep, a redirect, or a discard is performed, an
- implicit keep is not.
-
- Some actions may be defined to not cancel the implicit keep. These
- actions may not directly affect the delivery of a message, and are
- used for their side effects. None of the actions specified in this
- document meet that criteria, but extension actions will.
-
- For instance, with any of the short messages offered above, the
- following script produces no actions.
-
- Example: if size :over 500K { discard; }
-
- As a result, the implicit keep is taken.
-
-2.10.3. Message Uniqueness in a Mailbox
-
- Implementations SHOULD NOT deliver a message to the same folder more
- than once, even if a script explicitly asks for a message to be
- written to a mailbox twice.
-
-
-
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-
-
- The test for equality of two messages is implementation-defined.
-
- If a script asks for a message to be written to a mailbox twice, it
- MUST NOT be treated as an error.
-
-2.10.4. Limits on Numbers of Actions
-
- Site policy MAY limit numbers of actions taken and MAY impose
- restrictions on which actions can be used together. In the event
- that a script hits a policy limit on the number of actions taken for
- a particular message, an error occurs.
-
- Implementations MUST prohibit more than one reject.
-
- Implementations MUST allow at least one keep or one fileinto. If
- fileinto is not implemented, implementations MUST allow at least one
- keep.
-
- Implementations SHOULD prohibit reject when used with other actions.
-
-2.10.5. Extensions and Optional Features
-
- Because of the differing capabilities of many mail systems, several
- features of this specification are optional. Before any of these
- extensions can be executed, they must be declared with the "require"
- action.
-
- If an extension is not enabled with "require", implementations MUST
- treat it as if they did not support it at all.
-
- If a script does not understand an extension declared with require,
- the script must not be used at all. Implementations MUST NOT execute
- scripts which require unknown capability names.
-
- Note: The reason for this restriction is that prior experiences with
- languages such as LISP and Tcl suggest that this is a workable
- way of noting that a given script uses an extension.
-
- Experience with PostScript suggests that mechanisms that allow
- a script to work around missing extensions are not used in
- practice.
-
- Extensions which define actions MUST state how they interact with
- actions discussed in the base specification.
-
-
-
-
-
-
-
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-
-
-2.10.6. Errors
-
- In any programming language, there are compile-time and run-time
- errors.
-
- Compile-time errors are ones in syntax that are detectable if a
- syntax check is done.
-
- Run-time errors are not detectable until the script is run. This
- includes transient failures like disk full conditions, but also
- includes issues like invalid combinations of actions.
-
- When an error occurs in a Sieve script, all processing stops.
-
- Implementations MAY choose to do a full parse, then evaluate the
- script, then do all actions. Implementations might even go so far as
- to ensure that execution is atomic (either all actions are executed
- or none are executed).
-
- Other implementations may choose to parse and run at the same time.
- Such implementations are simpler, but have issues with partial
- failure (some actions happen, others don't).
-
- Implementations might even go so far as to ensure that scripts can
- never execute an invalid set of actions (e.g., reject + fileinto)
- before execution, although this could involve solving the Halting
- Problem.
-
- This specification allows any of these approaches. Solving the
- Halting Problem is considered extra credit.
-
- When an error happens, implementations MUST notify the user that an
- error occurred, which actions (if any) were taken, and do an implicit
- keep.
-
-2.10.7. Limits on Execution
-
- Implementations may limit certain constructs. However, this
- specification places a lower bound on some of these limits.
-
- Implementations MUST support fifteen levels of nested blocks.
-
- Implementations MUST support fifteen levels of nested test lists.
-
-3. Control Commands
-
- Control structures are needed to allow for multiple and conditional
- actions.
-
-
-
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-
-
-3.1. Control Structure If
-
- There are three pieces to if: "if", "elsif", and "else". Each is
- actually a separate command in terms of the grammar. However, an
- elsif MUST only follow an if, and an else MUST follow only either an
- if or an elsif. An error occurs if these conditions are not met.
-
- Syntax: if <test1: test> <block1: block>
-
- Syntax: elsif <test2: test> <block2: block>
-
- Syntax: else <block>
-
- The semantics are similar to those of any of the many other
- programming languages these control commands appear in. When the
- interpreter sees an "if", it evaluates the test associated with it.
- If the test is true, it executes the block associated with it.
-
- If the test of the "if" is false, it evaluates the test of the first
- "elsif" (if any). If the test of "elsif" is true, it runs the
- elsif's block. An elsif may be followed by an elsif, in which case,
- the interpreter repeats this process until it runs out of elsifs.
-
- When the interpreter runs out of elsifs, there may be an "else" case.
- If there is, and none of the if or elsif tests were true, the
- interpreter runs the else case.
-
- This provides a way of performing exactly one of the blocks in the
- chain.
-
- In the following example, both Message A and B are dropped.
-
- Example: require "fileinto";
- if header :contains "from" "coyote" {
- discard;
- } elsif header :contains ["subject"] ["$$$"] {
- discard;
- } else {
- fileinto "INBOX";
- }
-
-
- When the script below is run over message A, it redirects the message
- to acm@example.edu; message B, to postmaster@example.edu; any other
- message is redirected to field@example.edu.
-
-
-
-
-
-
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-
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-
-
- Example: if header :contains ["From"] ["coyote"] {
- redirect "acm@example.edu";
- } elsif header :contains "Subject" "$$$" {
- redirect "postmaster@example.edu";
- } else {
- redirect "field@example.edu";
- }
-
- Note that this definition prohibits the "... else if ..." sequence
- used by C. This is intentional, because this construct produces a
- shift-reduce conflict.
-
-3.2. Control Structure Require
-
- Syntax: require <capabilities: string-list>
-
- The require action notes that a script makes use of a certain
- extension. Such a declaration is required to use the extension, as
- discussed in section 2.10.5. Multiple capabilities can be declared
- with a single require.
-
- The require command, if present, MUST be used before anything other
- than a require can be used. An error occurs if a require appears
- after a command other than require.
-
- Example: require ["fileinto", "reject"];
-
- Example: require "fileinto";
- require "vacation";
-
-3.3. Control Structure Stop
-
- Syntax: stop
-
- The "stop" action ends all processing. If no actions have been
- executed, then the keep action is taken.
-
-4. Action Commands
-
- This document supplies five actions that may be taken on a message:
- keep, fileinto, redirect, reject, and discard.
-
- Implementations MUST support the "keep", "discard", and "redirect"
- actions.
-
- Implementations SHOULD support "reject" and "fileinto".
-
-
-
-
-
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-
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-
-
- Implementations MAY limit the number of certain actions taken (see
- section 2.10.4).
-
-4.1. Action reject
-
- Syntax: reject <reason: string>
-
- The optional "reject" action refuses delivery of a message by sending
- back an [MDN] to the sender. It resends the message to the sender,
- wrapping it in a "reject" form, noting that it was rejected by the
- recipient. In the following script, message A is rejected and
- returned to the sender.
-
- Example: if header :contains "from" "coyote@desert.example.org" {
- reject "I am not taking mail from you, and I don't want
- your birdseed, either!";
- }
-
- A reject message MUST take the form of a failure MDN as specified by
- [MDN]. The human-readable portion of the message, the first
- component of the MDN, contains the human readable message describing
- the error, and it SHOULD contain additional text alerting the
- original sender that mail was refused by a filter. This part of the
- MDN might appear as follows:
-
- ------------------------------------------------------------
- Message was refused by recipient's mail filtering program. Reason
- given was as follows:
-
- I am not taking mail from you, and I don't want your birdseed,
- either!
- ------------------------------------------------------------
-
- The MDN action-value field as defined in the MDN specification MUST
- be "deleted" and MUST have the MDN-sent-automatically and automatic-
- action modes set.
-
- Because some implementations can not or will not implement the reject
- command, it is optional. The capability string to be used with the
- require command is "reject".
-
-4.2. Action fileinto
-
- Syntax: fileinto <folder: string>
-
- The "fileinto" action delivers the message into the specified folder.
- Implementations SHOULD support fileinto, but in some environments
- this may be impossible.
-
-
-
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-
-
- The capability string for use with the require command is "fileinto".
-
- In the following script, message A is filed into folder
- "INBOX.harassment".
-
- Example: require "fileinto";
- if header :contains ["from"] "coyote" {
- fileinto "INBOX.harassment";
- }
-
-4.3. Action redirect
-
- Syntax: redirect <address: string>
-
- The "redirect" action is used to send the message to another user at
- a supplied address, as a mail forwarding feature does. The
- "redirect" action makes no changes to the message body or existing
- headers, but it may add new headers. The "redirect" modifies the
- envelope recipient.
-
- The redirect command performs an MTA-style "forward"--that is, what
- you get from a .forward file using sendmail under UNIX. The address
- on the SMTP envelope is replaced with the one on the redirect command
- and the message is sent back out. (This is not an MUA-style forward,
- which creates a new message with a different sender and message ID,
- wrapping the old message in a new one.)
-
- A simple script can be used for redirecting all mail:
-
- Example: redirect "bart@example.edu";
-
- Implementations SHOULD take measures to implement loop control,
- possibly including adding headers to the message or counting received
- headers. If an implementation detects a loop, it causes an error.
-
-4.4. Action keep
-
- Syntax: keep
-
- The "keep" action is whatever action is taken in lieu of all other
- actions, if no filtering happens at all; generally, this simply means
- to file the message into the user's main mailbox. This command
- provides a way to execute this action without needing to know the
- name of the user's main mailbox, providing a way to call it without
- needing to understand the user's setup, or the underlying mail
- system.
-
-
-
-
-
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-
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-
-
- For instance, in an implementation where the IMAP server is running
- scripts on behalf of the user at time of delivery, a keep command is
- equivalent to a fileinto "INBOX".
-
- Example: if size :under 1M { keep; } else { discard; }
-
- Note that the above script is identical to the one below.
-
- Example: if not size :under 1M { discard; }
-
-4.5. Action discard
-
- Syntax: discard
-
- Discard is used to silently throw away the message. It does so by
- simply canceling the implicit keep. If discard is used with other
- actions, the other actions still happen. Discard is compatible with
- all other actions. (For instance fileinto+discard is equivalent to
- fileinto.)
-
- Discard MUST be silent; that is, it MUST NOT return a non-delivery
- notification of any kind ([DSN], [MDN], or otherwise).
-
- In the following script, any mail from "idiot@example.edu" is thrown
- out.
-
- Example: if header :contains ["from"] ["idiot@example.edu"] {
- discard;
- }
-
- While an important part of this language, "discard" has the potential
- to create serious problems for users: Students who leave themselves
- logged in to an unattended machine in a public computer lab may find
- their script changed to just "discard". In order to protect users in
- this situation (along with similar situations), implementations MAY
- keep messages destroyed by a script for an indefinite period, and MAY
- disallow scripts that throw out all mail.
-
-5. Test Commands
-
- Tests are used in conditionals to decide which part(s) of the
- conditional to execute.
-
- Implementations MUST support these tests: "address", "allof",
- "anyof", "exists", "false", "header", "not", "size", and "true".
-
- Implementations SHOULD support the "envelope" test.
-
-
-
-
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-
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-
-
-5.1. Test address
-
- Syntax: address [ADDRESS-PART] [COMPARATOR] [MATCH-TYPE]
- <header-list: string-list> <key-list: string-list>
-
- The address test matches Internet addresses in structured headers
- that contain addresses. It returns true if any header contains any
- key in the specified part of the address, as modified by the
- comparator and the match keyword.
-
- Like envelope and header, this test returns true if any combination
- of the header-list and key-list arguments match.
-
- Internet email addresses [IMAIL] have the somewhat awkward
- characteristic that the local-part to the left of the at-sign is
- considered case sensitive, and the domain-part to the right of the
- at-sign is case insensitive. The "address" command does not deal
- with this itself, but provides the ADDRESS-PART argument for allowing
- users to deal with it.
-
- The address primitive never acts on the phrase part of an email
- address, nor on comments within that address. It also never acts on
- group names, although it does act on the addresses within the group
- construct.
-
- Implementations MUST restrict the address test to headers that
- contain addresses, but MUST include at least From, To, Cc, Bcc,
- Sender, Resent-From, Resent-To, and SHOULD include any other header
- that utilizes an "address-list" structured header body.
-
- Example: if address :is :all "from" "tim@example.com" {
- discard;
-
-5.2. Test allof
-
- Syntax: allof <tests: test-list>
-
- The allof test performs a logical AND on the tests supplied to it.
-
- Example: allof (false, false) => false
- allof (false, true) => false
- allof (true, true) => true
-
- The allof test takes as its argument a test-list.
-
-
-
-
-
-
-
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-
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-
-
-5.3. Test anyof
-
- Syntax: anyof <tests: test-list>
-
- The anyof test performs a logical OR on the tests supplied to it.
-
- Example: anyof (false, false) => false
- anyof (false, true) => true
- anyof (true, true) => true
-
-5.4. Test envelope
-
- Syntax: envelope [COMPARATOR] [ADDRESS-PART] [MATCH-TYPE]
- <envelope-part: string-list> <key-list: string-list>
-
- The "envelope" test is true if the specified part of the SMTP (or
- equivalent) envelope matches the specified key.
-
- If one of the envelope-part strings is (case insensitive) "from",
- then matching occurs against the FROM address used in the SMTP MAIL
- command.
-
- If one of the envelope-part strings is (case insensitive) "to", then
- matching occurs against the TO address used in the SMTP RCPT command
- that resulted in this message getting delivered to this user. Note
- that only the most recent TO is available, and only the one relevant
- to this user.
-
- The envelope-part is a string list and may contain more than one
- parameter, in which case all of the strings specified in the key-list
- are matched against all parts given in the envelope-part list.
-
- Like address and header, this test returns true if any combination of
- the envelope-part and key-list arguments is true.
-
- All tests against envelopes MUST drop source routes.
-
- If the SMTP transaction involved several RCPT commands, only the data
- from the RCPT command that caused delivery to this user is available
- in the "to" part of the envelope.
-
- If a protocol other than SMTP is used for message transport,
- implementations are expected to adapt this command appropriately.
-
- The envelope command is optional. Implementations SHOULD support it,
- but the necessary information may not be available in all cases.
-
-
-
-
-
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-
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-
-
- Example: require "envelope";
- if envelope :all :is "from" "tim@example.com" {
- discard;
- }
-
-5.5. Test exists
-
- Syntax: exists <header-names: string-list>
-
- The "exists" test is true if the headers listed in the header-names
- argument exist within the message. All of the headers must exist or
- the test is false.
-
- The following example throws out mail that doesn't have a From header
- and a Date header.
-
- Example: if not exists ["From","Date"] {
- discard;
- }
-
-5.6. Test false
-
- Syntax: false
-
- The "false" test always evaluates to false.
-
-5.7. Test header
-
- Syntax: header [COMPARATOR] [MATCH-TYPE]
- <header-names: string-list> <key-list: string-list>
-
- The "header" test evaluates to true if any header name matches any
- key. The type of match is specified by the optional match argument,
- which defaults to ":is" if not specified, as specified in section
- 2.6.
-
- Like address and envelope, this test returns true if any combination
- of the string-list and key-list arguments match.
-
- If a header listed in the header-names argument exists, it contains
- the null key (""). However, if the named header is not present, it
- does not contain the null key. So if a message contained the header
-
- X-Caffeine: C8H10N4O2
-
-
-
-
-
-
-
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-
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-
-
- these tests on that header evaluate as follows:
-
- header :is ["X-Caffeine"] [""] => false
- header :contains ["X-Caffeine"] [""] => true
-
-5.8. Test not
-
- Syntax: not <test>
-
- The "not" test takes some other test as an argument, and yields the
- opposite result. "not false" evaluates to "true" and "not true"
- evaluates to "false".
-
-5.9. Test size
-
- Syntax: size <":over" / ":under"> <limit: number>
-
- The "size" test deals with the size of a message. It takes either a
- tagged argument of ":over" or ":under", followed by a number
- representing the size of the message.
-
- If the argument is ":over", and the size of the message is greater
- than the number provided, the test is true; otherwise, it is false.
-
- If the argument is ":under", and the size of the message is less than
- the number provided, the test is true; otherwise, it is false.
-
- Exactly one of ":over" or ":under" must be specified, and anything
- else is an error.
-
- The size of a message is defined to be the number of octets from the
- initial header until the last character in the message body.
-
- Note that for a message that is exactly 4,000 octets, the message is
- neither ":over" 4000 octets or ":under" 4000 octets.
-
-5.10. Test true
-
- Syntax: true
-
- The "true" test always evaluates to true.
-
-6. Extensibility
-
- New control structures, actions, and tests can be added to the
- language. Sites must make these features known to their users; this
- document does not define a way to discover the list of extensions
- supported by the server.
-
-
-
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-
-
- Any extensions to this language MUST define a capability string that
- uniquely identifies that extension. If a new version of an extension
- changes the functionality of a previously defined extension, it MUST
- use a different name.
-
- In a situation where there is a submission protocol and an extension
- advertisement mechanism aware of the details of this language,
- scripts submitted can be checked against the mail server to prevent
- use of an extension that the server does not support.
-
- Extensions MUST state how they interact with constraints defined in
- section 2.10, e.g., whether they cancel the implicit keep, and which
- actions they are compatible and incompatible with.
-
-6.1. Capability String
-
- Capability strings are typically short strings describing what
- capabilities are supported by the server.
-
- Capability strings beginning with "vnd." represent vendor-defined
- extensions. Such extensions are not defined by Internet standards or
- RFCs, but are still registered with IANA in order to prevent
- conflicts. Extensions starting with "vnd." SHOULD be followed by the
- name of the vendor and product, such as "vnd.acme.rocket-sled".
-
- The following capability strings are defined by this document:
-
- envelope The string "envelope" indicates that the implementation
- supports the "envelope" command.
-
- fileinto The string "fileinto" indicates that the implementation
- supports the "fileinto" command.
-
- reject The string "reject" indicates that the implementation
- supports the "reject" command.
-
- comparator- The string "comparator-elbonia" is provided if the
- implementation supports the "elbonia" comparator.
- Therefore, all implementations have at least the
- "comparator-i;octet" and "comparator-i;ascii-casemap"
- capabilities. However, these comparators may be used
- without being declared with require.
-
-
-
-
-
-
-
-
-
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-
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-
-
-6.2. IANA Considerations
-
- In order to provide a standard set of extensions, a registry is
- provided by IANA. Capability names may be registered on a first-
- come, first-served basis. Extensions designed for interoperable use
- SHOULD be defined as standards track or IESG approved experimental
- RFCs.
-
-6.2.1. Template for Capability Registrations
-
- The following template is to be used for registering new Sieve
- extensions with IANA.
-
- To: iana@iana.org
- Subject: Registration of new Sieve extension
-
- Capability name:
- Capability keyword:
- Capability arguments:
- Standards Track/IESG-approved experimental RFC number:
- Person and email address to contact for further information:
-
-6.2.2. Initial Capability Registrations
-
- The following are to be added to the IANA registry for Sieve
- extensions as the initial contents of the capability registry.
-
- Capability name: fileinto
- Capability keyword: fileinto
- Capability arguments: fileinto <folder: string>
- Standards Track/IESG-approved experimental RFC number:
- RFC 3028 (Sieve base spec)
- Person and email address to contact for further information:
- Tim Showalter
- tjs@mirapoint.com
-
- Capability name: reject
- Capability keyword: reject
- Capability arguments: reject <reason: string>
- Standards Track/IESG-approved experimental RFC number:
- RFC 3028 (Sieve base spec)
- Person and email address to contact for further information:
- Tim Showalter
- tjs@mirapoint.com
-
-
-
-
-
-
-
-Showalter Standards Track [Page 28]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- Capability name: envelope
- Capability keyword: envelope
- Capability arguments:
- envelope [COMPARATOR] [ADDRESS-PART] [MATCH-TYPE]
- <envelope-part: string-list> <key-list: string-list>
- Standards Track/IESG-approved experimental RFC number:
- RFC 3028 (Sieve base spec)
- Person and email address to contact for further information:
- Tim Showalter
- tjs@mirapoint.com
-
- Capability name: comparator-*
- Capability keyword:
- comparator-* (anything starting with "comparator-")
- Capability arguments: (none)
- Standards Track/IESG-approved experimental RFC number:
- RFC 3028, Sieve, by reference of
- RFC 2244, Application Configuration Access Protocol
- Person and email address to contact for further information:
- Tim Showalter
- tjs@mirapoint.com
-
-6.3. Capability Transport
-
- As the range of mail systems that this document is intended to apply
- to is quite varied, a method of advertising which capabilities an
- implementation supports is difficult due to the wide range of
- possible implementations. Such a mechanism, however, should have
- property that the implementation can advertise the complete set of
- extensions that it supports.
-
-7. Transmission
-
- The MIME type for a Sieve script is "application/sieve".
-
- The registration of this type for RFC 2048 requirements is as
- follows:
-
- Subject: Registration of MIME media type application/sieve
-
- MIME media type name: application
- MIME subtype name: sieve
- Required parameters: none
- Optional parameters: none
- Encoding considerations: Most sieve scripts will be textual,
- written in UTF-8. When non-7bit characters are used,
- quoted-printable is appropriate for transport systems
- that require 7bit encoding.
-
-
-
-Showalter Standards Track [Page 29]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- Security considerations: Discussed in section 10 of RFC 3028.
- Interoperability considerations: Discussed in section 2.10.5
- of RFC 3028.
- Published specification: RFC 3028.
- Applications which use this media type: sieve-enabled mail servers
- Additional information:
- Magic number(s):
- File extension(s): .siv
- Macintosh File Type Code(s):
- Person & email address to contact for further information:
- See the discussion list at ietf-mta-filters@imc.org.
- Intended usage:
- COMMON
- Author/Change controller:
- See Author information in RFC 3028.
-
-8. Parsing
-
- The Sieve grammar is separated into tokens and a separate grammar as
- most programming languages are.
-
-8.1. Lexical Tokens
-
- Sieve scripts are encoded in UTF-8. The following assumes a valid
- UTF-8 encoding; special characters in Sieve scripts are all ASCII.
-
- The following are tokens in Sieve:
-
- - identifiers
- - tags
- - numbers
- - quoted strings
- - multi-line strings
- - other separators
-
- Blanks, horizontal tabs, CRLFs, and comments ("white space") are
- ignored except as they separate tokens. Some white space is required
- to separate otherwise adjacent tokens and in specific places in the
- multi-line strings.
-
- The other separators are single individual characters, and are
- mentioned explicitly in the grammar.
-
- The lexical structure of sieve is defined in the following BNF (as
- described in [ABNF]):
-
-
-
-
-
-
-Showalter Standards Track [Page 30]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- bracket-comment = "/*" *(CHAR-NOT-STAR / ("*" CHAR-NOT-SLASH)) "*/"
- ;; No */ allowed inside a comment.
- ;; (No * is allowed unless it is the last character,
- ;; or unless it is followed by a character that isn't a
- ;; slash.)
-
- CHAR-NOT-DOT = (%x01-09 / %x0b-0c / %x0e-2d / %x2f-ff)
- ;; no dots, no CRLFs
-
- CHAR-NOT-CRLF = (%x01-09 / %x0b-0c / %x0e-ff)
-
- CHAR-NOT-SLASH = (%x00-57 / %x58-ff)
-
- CHAR-NOT-STAR = (%x00-51 / %x53-ff)
-
- comment = bracket-comment / hash-comment
-
- hash-comment = ( "#" *CHAR-NOT-CRLF CRLF )
-
- identifier = (ALPHA / "_") *(ALPHA DIGIT "_")
-
- tag = ":" identifier
-
- number = 1*DIGIT [QUANTIFIER]
-
- QUANTIFIER = "K" / "M" / "G"
-
- quoted-string = DQUOTE *CHAR DQUOTE
- ;; in general, \ CHAR inside a string maps to CHAR
- ;; so \" maps to " and \\ maps to \
- ;; note that newlines and other characters are all allowed
- ;; strings
-
- multi-line = "text:" *(SP / HTAB) (hash-comment / CRLF)
- *(multi-line-literal / multi-line-dotstuff)
- "." CRLF
- multi-line-literal = [CHAR-NOT-DOT *CHAR-NOT-CRLF] CRLF
- multi-line-dotstuff = "." 1*CHAR-NOT-CRLF CRLF
- ;; A line containing only "." ends the multi-line.
- ;; Remove a leading '.' if followed by another '.'.
-
- white-space = 1*(SP / CRLF / HTAB) / comment
-
-8.2. Grammar
-
- The following is the grammar of Sieve after it has been lexically
- interpreted. No white space or comments appear below. The start
- symbol is "start".
-
-
-
-Showalter Standards Track [Page 31]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- argument = string-list / number / tag
-
- arguments = *argument [test / test-list]
-
- block = "{" commands "}"
-
- command = identifier arguments ( ";" / block )
-
- commands = *command
-
- start = commands
-
- string = quoted-string / multi-line
-
- string-list = "[" string *("," string) "]" / string ;; if
- there is only a single string, the brackets are optional
-
- test = identifier arguments
-
- test-list = "(" test *("," test) ")"
-
-9. Extended Example
-
- The following is an extended example of a Sieve script. Note that it
- does not make use of the implicit keep.
-
- #
- # Example Sieve Filter
- # Declare any optional features or extension used by the script
- #
- require ["fileinto", "reject"];
-
- #
- # Reject any large messages (note that the four leading dots get
- # "stuffed" to three)
- #
- if size :over 1M
- {
- reject text:
- Please do not send me large attachments.
- Put your file on a server and send me the URL.
- Thank you.
- .... Fred
- .
- ;
- stop;
- }
- #
-
-
-
-Showalter Standards Track [Page 32]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- # Handle messages from known mailing lists
- # Move messages from IETF filter discussion list to filter folder
- #
- if header :is "Sender" "owner-ietf-mta-filters@imc.org"
- {
- fileinto "filter"; # move to "filter" folder
- }
- #
- # Keep all messages to or from people in my company
- #
- elsif address :domain :is ["From", "To"] "example.com"
- {
- keep; # keep in "In" folder
- }
-
- #
- # Try and catch unsolicited email. If a message is not to me,
- # or it contains a subject known to be spam, file it away.
- #
- elsif anyof (not address :all :contains
- ["To", "Cc", "Bcc"] "me@example.com",
- header :matches "subject"
- ["*make*money*fast*", "*university*dipl*mas*"])
- {
- # If message header does not contain my address,
- # it's from a list.
- fileinto "spam"; # move to "spam" folder
- }
- else
- {
- # Move all other (non-company) mail to "personal"
- # folder.
- fileinto "personal";
- }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Showalter Standards Track [Page 33]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-10. Security Considerations
-
- Users must get their mail. It is imperative that whatever method
- implementations use to store the user-defined filtering scripts be
- secure.
-
- It is equally important that implementations sanity-check the user's
- scripts, and not allow users to create on-demand mailbombs. For
- instance, an implementation that allows a user to reject or redirect
- multiple times to a single message might also allow a user to create
- a mailbomb triggered by mail from a specific user. Site- or
- implementation-defined limits on actions are useful for this.
-
- Several commands, such as "discard", "redirect", and "fileinto" allow
- for actions to be taken that are potentially very dangerous.
-
- Implementations SHOULD take measures to prevent languages from
- looping.
-
-11. Acknowledgments
-
- I am very thankful to Chris Newman for his support and his ABNF
- syntax checker, to John Myers and Steve Hole for outlining the
- requirements for the original drafts, to Larry Greenfield for nagging
- me about the grammar and finally fixing it, to Greg Sereda for
- repeatedly fixing and providing examples, to Ned Freed for fixing
- everything else, to Rob Earhart for an early implementation and a
- great deal of help, and to Randall Gellens for endless amounts of
- proofreading. I am grateful to Carnegie Mellon University where most
- of the work on this document was done. I am also indebted to all of
- the readers of the ietf-mta-filters@imc.org mailing list.
-
-12. Author's Address
-
- Tim Showalter
- Mirapoint, Inc.
- 909 Hermosa Court
- Sunnyvale, CA 94085
-
- EMail: tjs@mirapoint.com
-
-13. References
-
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 2234, November 1997.
-
-
-
-
-
-
-Showalter Standards Track [Page 34]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
- [ACAP] Newman, C. and J. G. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November 1997.
-
- [BINARY-SI] "Standard IEC 60027-2: Letter symbols to be used in
- electrical technology - Part 2: Telecommunications and
- electronics", January 1999.
-
- [DSN] Moore, K. and G. Vaudreuil, "An Extensible Message Format
- for Delivery Status Notifications", RFC 1894, January
- 1996.
-
- [FLAMES] Borenstein, N, and C. Thyberg, "Power, Ease of Use, and
- Cooperative Work in a Practical Multimedia Message
- System", Int. J. of Man-Machine Studies, April, 1991.
- Reprinted in Computer-Supported Cooperative Work and
- Groupware, Saul Greenberg, editor, Harcourt Brace
- Jovanovich, 1991. Reprinted in Readings in Groupware and
- Computer-Supported Cooperative Work, Ronald Baecker,
- editor, Morgan Kaufmann, 1993.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [IMAP] Crispin, M., "Internet Message Access Protocol - version
- 4rev1", RFC 2060, December 1996.
-
- [IMAIL] Crocker, D., "Standard for the Format of ARPA Internet
- Text Messages", STD 11, RFC 822, August 1982.
-
- [MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part One: Format of Internet Message
- Bodies", RFC 2045, November 1996.
-
- [MDN] Fajman, R., "An Extensible Message Format for Message
- Disposition Notifications", RFC 2298, March 1998.
-
- [RFC1123] Braden, R., "Requirements for Internet Hosts --
- Application and Support", STD 3, RFC 1123, November 1989.
-
- [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
- 821, August 1982.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of Unicode
- and ISO 10646", RFC 2044, October 1996.
-
-
-
-
-
-
-
-Showalter Standards Track [Page 35]
-
-RFC 3028 Sieve: A Mail Filtering Language January 2001
-
-
-14. Full Copyright Statement
-
- Copyright (C) The Internet Society (2001). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Showalter Standards Track [Page 36]
-
diff --git a/proto/sieve/rfc3431.txt b/proto/sieve/rfc3431.txt
@@ -1,451 +0,0 @@
-
-
-
-
-
-
-Network Working Group W. Segmuller
-Request for Comment: 3431 IBM T.J. Watson Research Center
-Category: Standards Track December 2002
-
-
- Sieve Extension: Relational Tests
-
-Status of this Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (C) The Internet Society (2002). All Rights Reserved.
-
-Abstract
-
- This document describes the RELATIONAL extension to the Sieve mail
- filtering language defined in RFC 3028. This extension extends
- existing conditional tests in Sieve to allow relational operators.
- In addition to testing their content, it also allows for testing of
- the number of entities in header and envelope fields.
-
-1 Introduction
-
- Sieve [SIEVE] is a language for filtering e-mail messages at the time
- of final delivery. It is designed to be implementable on either a
- mail client or mail server. It is meant to be extensible, simple,
- and independent of access protocol, mail architecture, and operating
- system. It is suitable for running on a mail server where users may
- not be allowed to execute arbitrary programs, such as on black box
- Internet Messages Access Protocol (IMAP) servers, as it has no
- variables, loops, nor the ability to shell out to external programs.
-
- The RELATIONAL extension provides relational operators on the
- address, envelope, and header tests. This extension also provides a
- way of counting the entities in a message header or address field.
-
- With this extension, the sieve script may now determine if a field is
- greater than or less than a value instead of just equivalent. One
- use is for the x-priority field: move messages with a priority
- greater than 3 to the "work on later" folder. Mail could also be
- sorted by the from address. Those userids that start with 'a'-'m' go
- to one folder, and the rest go to another folder.
-
-
-
-Segmuller Standards Track [Page 1]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
- The sieve script can also determine the number of fields in the
- header, or the number of addresses in a recipient field. For
- example: are there more than 5 addresses in the to and cc fields.
-
-2 Conventions used in this document
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in BCP 14, RFC 2119.
-
- Conventions for notations are as in [SIEVE] section 1.1, including
- the use of [KEYWORDS] and "Syntax:" label for the definition of
- action and tagged arguments syntax, and the use of [ABNF].
-
- The capability string associated with extension defined in this
- document is "relational".
-
-3 Comparators
-
- This document does not define any comparators or exempt any
- comparators from the require clause. Any comparator used, other than
- "i;octet" and "i;ascii-casemap", MUST be declared a require clause as
- defined in [SIEVE].
-
- The "i;ascii-numeric" comparator, as defined in [ACAP], MUST be
- supported for any implementation of this extension. The comparator
- "i;ascii-numeric" MUST support at least 32 bit unsigned integers.
-
- Larger integers MAY be supported. Note: the "i;ascii-numeric"
- comparator does not support negative numbers.
-
-4 Match Type
-
- This document defines two new match types. They are the VALUE match
- type and the COUNT match type.
-
- The syntax is:
-
- MATCH-TYPE =/ COUNT / VALUE
-
- COUNT = ":count" relational-match
-
- VALUE = ":value" relational-match
-
- relational-match = DQUOTE ( "gt" / "ge" / "lt"
- / "le" / "eq" / "ne" ) DQUOTE
-
-
-
-
-
-Segmuller Standards Track [Page 2]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
-4.1 Match Type Value
-
- The VALUE match type does a relational comparison between strings.
-
- The VALUE match type may be used with any comparator which returns
- sort information.
-
- Leading and trailing white space MUST be removed from the value of
- the message for the comparison. White space is defined as
-
- SP / HTAB / CRLF
-
- A value from the message is considered the left side of the relation.
- A value from the test expression, the key-list for address, envelope,
- and header tests, is the right side of the relation.
-
- If there are multiple values on either side or both sides, the test
- is considered true, if any pair is true.
-
-4.2 Match Type Count
-
- The COUNT match type first determines the number of the specified
- entities in the message and does a relational comparison of the
- number of entities to the values specified in the test expression.
-
- The COUNT match type SHOULD only be used with numeric comparators.
-
- The Address Test counts the number of recipients in the specified
- fields. Group names are ignored.
-
- The Envelope Test counts the number of recipients in the specified
- envelope parts. The envelope "to" will always have only one entry,
- which is the address of the user for whom the sieve script is
- running. There is no way a sieve script can determine if the message
- was actually sent to someone else using this test. The envelope
- "from" will be 0 if the MAIL FROM is blank, or 1 if MAIL FROM is not
- blank.
-
- The Header Test counts the total number of instances of the specified
- fields. This does not count individual addresses in the "to", "cc",
- and other recipient fields.
-
- In all cases, if more than one field name is specified, the counts
- for all specified fields are added together to obtain the number for
- comparison. Thus, specifying ["to", "cc"] in an address COUNT test,
- comparing the total number of "to" and "cc" addresses; if separate
- counts are desired, they must be done in two comparisons, perhaps
- joined by "allof" or "anyof".
-
-
-
-Segmuller Standards Track [Page 3]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
-5 Security Considerations
-
- Security considerations are discussed in [SIEVE].
-
- An implementation MUST ensure that the test for envelope "to" only
- reflects the delivery to the current user. It MUST not be possible
- for a user to determine if this message was delivered to someone else
- using this test.
-
-6 Example
-
- Using the message:
-
- received: ...
- received: ...
- subject: example
- to: foo@example.com.invalid, baz@example.com.invalid
- cc: qux@example.com.invalid
-
- The test:
-
- address :count "ge" :comparator "i;ascii-numeric" ["to", "cc"]
- ["3"]
-
- would be true and the test
-
- anyof ( address :count "ge" :comparator "i;ascii-numeric"
- ["to"] ["3"],
- address :count "ge" :comparator "i;ascii-numeric"
- ["cc"] ["3"] )
-
- would be false.
-
- To check the number of received fields in the header, the
- following test may be used:
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["received"] ["3"]
-
- This would return false. But
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["received", "subject"] ["3"]
-
- would return true.
-
-
-
-
-
-
-Segmuller Standards Track [Page 4]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
- The test:
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["to", "cc"] ["3"]
-
- will always return false on an RFC 2822 compliant message [RFC2822],
- since a message can have at most one "to" field and at most one "cc"
- field. This test counts the number of fields, not the number of
- addresses.
-
-7 Extended Example
-
- require ["relational", "comparator-i;ascii-numeric"];
-
- if header :value "lt" :comparator "i;ascii-numeric"
- ["x-priority"] ["3"]
- {
- fileinto "Priority";
- }
-
- elseif address :count "gt" :comparator "i;ascii-numeric"
- ["to"] ["5"]
- {
- # everything with more than 5 recipients in the "to" field
- # is considered SPAM
- fileinto "SPAM";
- }
-
- elseif address :value "gt" :all :comparator "i;ascii-casemap"
- ["from"] ["M"]
- {
- fileinto "From N-Z";
- } else {
- fileinto "From A-M";
- }
-
- if allof ( address :count "eq" :comparator "i;ascii-numeric"
- ["to", "cc"] ["1"] ,
- address :all :comparator "i;ascii-casemap"
- ["to", "cc"] ["me@foo.example.com.invalid"]
- {
- fileinto "Only me";
- }
-
-
-
-
-
-
-
-
-Segmuller Standards Track [Page 5]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
-8 IANA Considerations
-
- The following template specifies the IANA registration of the Sieve
- extension specified in this document:
-
- To: iana@iana.org
- Subject: Registration of new Sieve extension
-
- Capability name: RELATIONAL
- Capability keyword: relational
- Capability arguments: N/A
- Standards Track/IESG-approved experimental RFC number: this RFC
- Person and email address to contact for further information:
- Wolfgang Segmuller
- IBM T.J. Watson Research Center
- 30 Saw Mill River Rd
- Hawthorne, NY 10532
-
- Email: whs@watson.ibm.com
-
- This information should be added to the list of sieve extensions
- given on http://www.iana.org/assignments/sieve-extensions.
-
-9 References
-
-9.1 Normative References
-
- [SIEVE] Showalter, T., "Sieve: A Mail Filtering Language", RFC
- 3028, January 2001.
-
- [Keywords] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [ABNF] Crocker, D., "Augmented BNF for Syntax Specifications:
- ABNF", RFC 2234, November 1997.
-
- [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
- 2001.
-
-9.2 Non-Normative References
-
- [ACAP] Newman, C. and J. G. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November 1997.
-
-
-
-
-
-
-
-
-Segmuller Standards Track [Page 6]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
-10 Author's Address
-
- Wolfgang Segmuller
- IBM T.J. Watson Research Center
- 30 Saw Mill River Rd
- Hawthorne, NY 10532
-
- EMail: whs@watson.ibm.com
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Segmuller Standards Track [Page 7]
-
-RFC 3431 Sieve Extension: Relational Tests December 2002
-
-
-11 Full Copyright Statement
-
- Copyright (C) The Internet Society (2002). All Rights Reserved.
-
- This document and translations of it may be copied and furnished to
- others, and derivative works that comment on or otherwise explain it
- or assist in its implementation may be prepared, copied, published
- and distributed, in whole or in part, without restriction of any
- kind, provided that the above copyright notice and this paragraph are
- included on all such copies and derivative works. However, this
- document itself may not be modified in any way, such as by removing
- the copyright notice or references to the Internet Society or other
- Internet organizations, except as needed for the purpose of
- developing Internet standards in which case the procedures for
- copyrights defined in the Internet Standards process must be
- followed, or as required to translate it into languages other than
- English.
-
- The limited permissions granted above are perpetual and will not be
- revoked by the Internet Society or its successors or assigns.
-
- This document and the information contained herein is provided on an
- "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
- TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
- BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
- HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Acknowledgement
-
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
-
-
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diff --git a/proto/sieve/rfc5231.txt b/proto/sieve/rfc5231.txt
@@ -1,507 +0,0 @@
-
-
-
-
-
-
-Network Working Group W. Segmuller
-Request for Comments: 5231 B. Leiba
-Obsoletes: 3431 IBM T.J. Watson Research Center
-Category: Standards Track January 2008
-
-
- Sieve Email Filtering: Relational Extension
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- This document describes the RELATIONAL extension to the Sieve mail
- filtering language defined in RFC 3028. This extension extends
- existing conditional tests in Sieve to allow relational operators.
- In addition to testing their content, it also allows for testing of
- the number of entities in header and envelope fields.
-
- This document obsoletes RFC 3431.
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
- 2. Conventions Used in This Document . . . . . . . . . . . . . . . 2
- 3. Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . 2
- 4. Match Types . . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 4.1. Match Type VALUE . . . . . . . . . . . . . . . . . . . . . 3
- 4.2. Match Type COUNT . . . . . . . . . . . . . . . . . . . . . 3
- 5. Interaction with Other Sieve Actions . . . . . . . . . . . . . 4
- 6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
- 7. Extended Example . . . . . . . . . . . . . . . . . . . . . . . 6
- 8. Changes since RFC 3431 . . . . . . . . . . . . . . . . . . . . 6
- 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
- 10. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
- 11. Normative References . . . . . . . . . . . . . . . . . . . . . 7
-
-
-
-
-
-
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-
-Segmuller & Leiba Standards Track [Page 1]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
-1. Introduction
-
- The RELATIONAL extension to the Sieve mail filtering language [Sieve]
- provides relational operators on the address, envelope, and header
- tests. This extension also provides a way of counting the entities
- in a message header or address field.
-
- With this extension, the Sieve script may now determine if a field is
- greater than or less than a value instead of just equivalent. One
- use is for the x-priority field: move messages with a priority
- greater than 3 to the "work on later" folder. Mail could also be
- sorted by the from address. Those userids that start with 'a'-'m' go
- to one folder, and the rest go to another folder.
-
- The Sieve script can also determine the number of fields in the
- header, or the number of addresses in a recipient field, for example,
- whether there are more than 5 addresses in the to and cc fields.
-
- The capability string associated with the extension defined in this
- document is "relational".
-
-2. Conventions Used in This Document
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in BCP 14, RFC 2119.
-
- Conventions for notations are as in [Sieve] section 1.1, including
- the use of [Kwds] and the use of [ABNF].
-
-3. Comparators
-
- This document does not define any comparators or exempt any
- comparators from the require clause. Any comparator used must be
- treated as defined in [Sieve].
-
- The "i;ascii-numeric" comparator, as defined in [RFC4790], MUST be
- supported for any implementation of this extension. The comparator
- "i;ascii-numeric" MUST support at least 32-bit unsigned integers.
-
- Larger integers MAY be supported. Note: the "i;ascii-numeric"
- comparator does not support negative numbers.
-
-
-
-
-
-
-
-
-
-Segmuller & Leiba Standards Track [Page 2]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
-4. Match Types
-
- This document defines two new match types. They are the VALUE match
- type and the COUNT match type.
-
- The syntax is:
-
- MATCH-TYPE =/ COUNT / VALUE
-
- COUNT = ":count" relational-match
-
- VALUE = ":value" relational-match
-
- relational-match = DQUOTE
- ("gt" / "ge" / "lt" / "le" / "eq" / "ne") DQUOTE
- ; "gt" means "greater than", the C operator ">".
- ; "ge" means "greater than or equal", the C operator ">=".
- ; "lt" means "less than", the C operator "<".
- ; "le" means "less than or equal", the C operator "<=".
- ; "eq" means "equal to", the C operator "==".
- ; "ne" means "not equal to", the C operator "!=".
-
-4.1. Match Type VALUE
-
- The VALUE match type does a relational comparison between strings.
-
- The VALUE match type may be used with any comparator that returns
- sort information.
-
- A value from the message is considered the left side of the relation.
- A value from the test expression, the key-list for address, envelope,
- and header tests, is the right side of the relation.
-
- If there are multiple values on either side or both sides, the test
- is considered true if any pair is true.
-
-4.2. Match Type COUNT
-
- The COUNT match type first determines the number of the specified
- entities in the message and does a relational comparison of the
- number of entities, as defined below, to the values specified in the
- test expression.
-
- The COUNT match type SHOULD only be used with numeric comparators.
-
- The Address Test counts the number of addresses (the number of
- "mailbox" elements, as defined in [RFC2822]) in the specified fields.
- Group names are ignored, but the contained mailboxes are counted.
-
-
-
-Segmuller & Leiba Standards Track [Page 3]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
- The Envelope Test counts the number of addresses in the specified
- envelope parts. The envelope "to" will always have only one entry,
- which is the address of the user for whom the Sieve script is
- running. Using this test, there is no way a Sieve script can
- determine if the message was actually sent to someone else. The
- envelope "from" will be 0 if the MAIL FROM is empty, or 1 if MAIL
- FROM is not empty.
-
- The Header Test counts the total number of instances of the specified
- fields. This does not count individual addresses in the "to", "cc",
- and other recipient fields.
-
- In all cases, if more than one field name is specified, the counts
- for all specified fields are added together to obtain the number for
- comparison. Thus, specifying ["to", "cc"] in an address COUNT test
- compares the total number of "to" and "cc" addresses; if separate
- counts are desired, they must be done in two comparisons, perhaps
- joined by "allof" or "anyof".
-
-5. Interaction with Other Sieve Actions
-
- This specification adds two match types. The VALUE match type only
- works with comparators that return sort information. The COUNT match
- type only makes sense with numeric comparators.
-
- There is no interaction with any other Sieve operations, nor with any
- known extensions. In particular, this specification has no effect on
- implicit KEEP, nor on any explicit message actions.
-
-6. Example
-
- Using the message:
-
- received: ...
- received: ...
- subject: example
- to: foo@example.com, baz@example.com
- cc: qux@example.com
-
- The test:
-
- address :count "ge" :comparator "i;ascii-numeric"
- ["to", "cc"] ["3"]
-
- would evaluate to true, and the test
-
-
-
-
-
-
-Segmuller & Leiba Standards Track [Page 4]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
- anyof ( address :count "ge" :comparator "i;ascii-numeric"
- ["to"] ["3"],
- address :count "ge" :comparator "i;ascii-numeric"
- ["cc"] ["3"] )
-
- would evaluate to false.
-
- To check the number of received fields in the header, the following
- test may be used:
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["received"] ["3"]
-
- This would evaluate to false. But
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["received", "subject"] ["3"]
-
- would evaluate to true.
-
- The test:
-
- header :count "ge" :comparator "i;ascii-numeric"
- ["to", "cc"] ["3"]
-
- will always evaluate to false on an RFC 2822 compliant message
- [RFC2822], since a message can have at most one "to" field and at
- most one "cc" field. This test counts the number of fields, not the
- number of addresses.
-
-
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-Segmuller & Leiba Standards Track [Page 5]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
-7. Extended Example
-
- require ["relational", "comparator-i;ascii-numeric", "fileinto"];
-
- if header :value "lt" :comparator "i;ascii-numeric"
- ["x-priority"] ["3"]
- {
- fileinto "Priority";
- }
-
- elsif address :count "gt" :comparator "i;ascii-numeric"
- ["to"] ["5"]
- {
- # everything with more than 5 recipients in the "to" field
- # is considered SPAM
- fileinto "SPAM";
- }
-
- elsif address :value "gt" :all :comparator "i;ascii-casemap"
- ["from"] ["M"]
- {
- fileinto "From N-Z";
- } else {
- fileinto "From A-M";
- }
-
- if allof ( address :count "eq" :comparator "i;ascii-numeric"
- ["to", "cc"] ["1"] ,
- address :all :comparator "i;ascii-casemap"
- ["to", "cc"] ["me@foo.example.com"] )
- {
- fileinto "Only me";
- }
-
-8. Changes since RFC 3431
-
- Apart from several minor editorial/wording changes, the following
- list describes the notable changes to this specification since RFC
- 3431.
-
- o Updated references, including changing the comparator reference
- from the Application Configuration Access Protocol (ACAP) to the
- "Internet Application Protocol Collation Registry" document
- [RFC4790].
-
- o Updated and corrected the examples.
-
-
-
-
-
-Segmuller & Leiba Standards Track [Page 6]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
- o Added definition comments to ABNF for "gt", "lt", etc.
-
- o Clarified what RFC 2822 elements are counted in the COUNT test.
-
- o Removed the requirement to strip white space from header fields
- before comparing; a more general version of this requirement has
- been added to the Sieve base spec.
-
-9. IANA Considerations
-
- The following template specifies the IANA registration of the
- relational Sieve extension specified in this document:
-
- To: iana@iana.org
- Subject: Registration of new Sieve extension
-
- Capability name: relational
- Description: Extends existing conditional tests in Sieve language
- to allow relational operators
- RFC number: RFC 5231
- Contact address: The Sieve discussion list <ietf-mta-filters@imc.org>
-
-10. Security Considerations
-
- An implementation MUST ensure that the test for envelope "to" only
- reflects the delivery to the current user. Using this test, it MUST
- not be possible for a user to determine if this message was delivered
- to someone else.
-
- Additional security considerations are discussed in [Sieve].
-
-11. Normative References
-
- [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 4234, October 2005.
-
- [Kwds] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", RFC 2119, March 1997.
-
- [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
- April 2001.
-
- [RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet
- Application Protocol Collation Registry", RFC 4790,
- March 2007.
-
- [Sieve] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
- Filtering Language", RFC 5228, January 2008.
-
-
-
-Segmuller & Leiba Standards Track [Page 7]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
-Authors' Addresses
-
- Wolfgang Segmuller
- IBM T.J. Watson Research Center
- 19 Skyline Drive
- Hawthorne, NY 10532
- US
-
- Phone: +1 914 784 7408
- EMail: werewolf@us.ibm.com
-
-
- Barry Leiba
- IBM T.J. Watson Research Center
- 19 Skyline Drive
- Hawthorne, NY 10532
- US
-
- Phone: +1 914 784 7941
- EMail: leiba@watson.ibm.com
-
-
-
-
-
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-Segmuller & Leiba Standards Track [Page 8]
-
-RFC 5231 Sieve: Relational Extension January 2008
-
-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008).
-
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
- THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
- OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
- THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-
-
-
-
-
-
-
-
-
-
-
-Segmuller & Leiba Standards Track [Page 9]
-
diff --git a/proto/sieve/rfc5260.txt b/proto/sieve/rfc5260.txt
@@ -1,731 +0,0 @@
-
-
-
-
-
-
-Network Working Group N. Freed
-Request for Comments: 5260 Sun Microsystems
-Category: Standards Track July 2008
-
-
- Sieve Email Filtering: Date and Index Extensions
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Abstract
-
- This document describes the "date" and "index" extensions to the
- Sieve email filtering language. The "date" extension gives Sieve the
- ability to test date and time values in various ways. The "index"
- extension provides a means to limit header and address tests to
- specific instances of header fields when header fields are repeated.
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
- 2. Conventions Used in This Document . . . . . . . . . . . . . . 2
- 3. Capability Identifiers . . . . . . . . . . . . . . . . . . . . 3
- 4. Date Test . . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 4.1. Zone and Originalzone Arguments . . . . . . . . . . . . . 4
- 4.2. Date-part Argument . . . . . . . . . . . . . . . . . . . . 4
- 4.3. Comparator Interactions with Date-part Arguments . . . . . 5
- 4.4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
- 5. Currentdate Test . . . . . . . . . . . . . . . . . . . . . . . 6
- 5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
- 6. Index Extension . . . . . . . . . . . . . . . . . . . . . . . 7
- 6.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8
- 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
- 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
- 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
- 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
- 9.2. Informative References . . . . . . . . . . . . . . . . . . 10
- Appendix A. Julian Date Conversions . . . . . . . . . . . . . . . 11
- Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 12
-
-
-
-
-
-
-
-Freed Standards Track [Page 1]
-
-RFC 5260 Sieve Date and Index Extensions July 2008
-
-
-1. Introduction
-
- Sieve [RFC5228] is a language for filtering email messages at or
- around the time of final delivery. It is designed to be
- implementable on either a mail client or mail server. It is meant to
- be extensible, simple, and independent of access protocol, mail
- architecture, and operating system. It is suitable for running on a
- mail server where users may not be allowed to execute arbitrary
- programs, such as on black box Internet Message Access Protocol
- [RFC3501] servers, as it does not have user-controlled loops or the
- ability to run external programs.
-
- The "date" extension provides a new date test to extract and match
- date/time information from structured header fields. The date test
- is similar in concept to the address test specified in [RFC5228],
- which performs similar operations on addresses in header fields.
-
- The "date" extension also provides a currentdate test that operates
- on the date and time when the Sieve script is executed.
-
- Some header fields containing date/time information, e.g., Received:,
- naturally occur more than once in a single header. In such cases it
- is useful to be able to restrict the date test to some subset of the
- fields that are present. For example, it may be useful to apply a
- date test to the last (earliest) Received: field. Additionally, it
- may also be useful to apply similar restrictions to either the header
- or address tests specified in [RFC5228].
-
- For this reason, this specification also defines an "index"
- extension. This extension adds two additional tagged arguments
- :index and :last to the header, address, and date tests. If present,
- these arguments specify which occurrence of the named header field is
- to be tested.
-
-2. Conventions Used in This Document
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in RFC 2119 [RFC2119].
-
- The terms used to describe the various components of the Sieve
- language are taken from Section 1.1 of [RFC5228]. Section 2 of the
- same document describes basic Sieve language syntax and semantics.
- The date-time syntactic element defined using ABNF notation [RFC5234]
- in [RFC3339] is also used here.
-
-
-
-
-
-
-Freed Standards Track [Page 2]
-
-RFC 5260 Sieve Date and Index Extensions July 2008
-
-
-3. Capability Identifiers
-
- The capability strings associated with the two extensions defined in
- this document are "date" and "index".
-
-4. Date Test
-
- Usage: date [<":zone" <time-zone: string>> / ":originalzone"]
- [COMPARATOR] [MATCH-TYPE] <header-name: string>
- <date-part: string> <key-list: string-list>
-
- The date test matches date/time information derived from headers
- containing [RFC2822] date-time values. The date/time information is
- extracted from the header, shifted to the specified time zone, and
- the value of the given date-part is determined. The test returns
- true if the resulting string matches any of the strings specified in
- the key-list, as controlled by the comparator and match keywords.
- The date test returns false unconditionally if the specified header
- field does not exist, the field exists but does not contain a
- syntactically valid date-time specification, the date-time isn't
- valid according to the rules of the calendar system (e.g., January
- 32nd, February 29 in a non-leap year), or the resulting string fails
- to match any key-list value.
-
- The type of match defaults to ":is" and the default comparator is
- "i;ascii-casemap".
-
- Unlike the header and address tests, the date test can only be
- applied to a single header field at a time. If multiple header
- fields with the same name are present, only the first field that is
- found is used. (Note, however, that this behavior can be modified
- with the "index" extension defined below.) These restrictions
- simplify the test and keep the meaning clear.
-
- The "relational" extension [RFC5231] adds a match type called
- ":count". The count of a date test is 1 if the specified field
- exists and contains a valid date; 0, otherwise.
-
- Implementations MUST support extraction of RFC 2822 date-time
- information that either makes up the entire header field (e.g., as it
- does in a standard Date: header field) or appears at the end of a
- header field following a semicolon (e.g., as it does in a standard
- Received: header field). Implementations MAY support extraction of
- date and time information in RFC2822 or other formats that appears in
- other positions in header field content. In the case of a field
- containing more than one date or time value, the last one that
- appears SHOULD be used.
-
-
-
-
-Freed Standards Track [Page 3]
-
-RFC 5260 Sieve Date and Index Extensions July 2008
-
-
-4.1. Zone and Originalzone Arguments
-
- The :originalzone argument specifies that the time zone offset
- originally in the extracted date-time value should be retained. The
- :zone argument specifies a specific time zone offset that the date-
- time value is to be shifted to prior to testing. It is an error to
- specify both :zone and :originalzone.
-
- The value of time-zone MUST be an offset relative to UTC with the
- following syntax:
-
- time-zone = ( "+" / "-" ) 4DIGIT
-
- The "+" or "-" indicates whether the time-of-day is ahead of (i.e.,
- east of) or behind (i.e., west of) UTC. The first two digits
- indicate the number of hours difference from Universal Time, and the
- last two digits indicate the number of minutes difference from
- Universal Time. Note that this agrees with the RFC 2822 format for
- time zone offsets, not the ISO 8601 format.
-
- If both the :zone and :originalzone arguments are omitted, the local
- time zone MUST be used.
-
-4.2. Date-part Argument
-
- The date-part argument specifies a particular part of the resulting
- date/time value to match against the key-list. Possible case-
- insensitive values are:
-
- "year" => the year, "0000" .. "9999".
- "month" => the month, "01" .. "12".
- "day" => the day, "01" .. "31".
- "date" => the date in "yyyy-mm-dd" format.
- "julian" => the Modified Julian Day, that is, the date
- expressed as an integer number of days since
- 00:00 UTC on November 17, 1858 (using the Gregorian
- calendar). This corresponds to the regular
- Julian Day minus 2400000.5. Sample routines to
- convert to and from modified Julian dates are
- given in Appendix A.
- "hour" => the hour, "00" .. "23".
- "minute" => the minute, "00" .. "59".
- "second" => the second, "00" .. "60".
- "time" => the time in "hh:mm:ss" format.
- "iso8601" => the date and time in restricted ISO 8601 format.
- "std11" => the date and time in a format appropriate
- for use in a Date: header field [RFC2822].
-
-
-
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-
- "zone" => the time zone in use. If the user specified a
- time zone with ":zone", "zone" will
- contain that value. If :originalzone is specified
- this value will be the original zone specified
- in the date-time value. If neither argument is
- specified the value will be the server's default
- time zone in offset format "+hhmm" or "-hhmm". An
- offset of 0 (Zulu) always has a positive sign.
- "weekday" => the day of the week expressed as an integer between
- "0" and "6". "0" is Sunday, "1" is Monday, etc.
-
- The restricted ISO 8601 format is specified by the date-time ABNF
- production given in [RFC3339], Section 5.6, with the added
- restrictions that the letters "T" and "Z" MUST be in upper case, and
- a time zone offset of zero MUST be represented by "Z" and not
- "+00:00".
-
-4.3. Comparator Interactions with Date-part Arguments
-
- Not all comparators are suitable with all date-part arguments. In
- general, the date-parts can be compared and tested for equality with
- either "i;ascii-casemap" (the default) or "i;octet", but there are
- two exceptions:
-
- julian This is an integer, and may or may not have leading zeros.
- As such, "i;ascii-numeric" is almost certainly the best
- comparator to use with it.
-
- std11 This is provided as a means to obtain date/time values in a
- format appropriate for inclusion in email header fields. The
- wide range of possible syntaxes for a std11 date/time --
- which implementations of this extension are free to use when
- composing a std11 string -- makes this format a poor choice
- for comparisons. Nevertheless, if a comparison must be
- performed, this is case-insensitive, and therefore "i;ascii-
- casemap" needs to be used.
-
- "year", "month", "day", "hour", "minute", "second" and "weekday" all
- use fixed-width string representations of integers, and can therefore
- be compared with "i;octet", "i;ascii-casemap", and "i;ascii-numeric"
- with equivalent results.
-
- "date" and "time" also use fixed-width string representations of
- integers, and can therefore be compared with "i;octet" and "i;ascii-
- casemap"; however, "i;ascii-numeric" can't be used with it, as
- "i;ascii-numeric" doesn't allow for non-digit characters.
-
-
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-
-4.4. Examples
-
- The Date: field can be checked to test when the sender claims to have
- created the message and act accordingly:
-
- require ["date", "relational", "fileinto"];
- if allof(header :is "from" "boss@example.com",
- date :value "ge" :originalzone "date" "hour" "09",
- date :value "lt" :originalzone "date" "hour" "17")
- { fileinto "urgent"; }
-
- Testing the initial Received: field can provide an indication of when
- a message was actually received by the local system:
-
- require ["date", "relational", "fileinto"];
- if anyof(date :is "received" "weekday" "0",
- date :is "received" "weekday" "6")
- { fileinto "weekend"; }
-
-5. Currentdate Test
-
- Usage: currentdate [":zone" <time-zone: string>]
- [COMPARATOR] [MATCH-TYPE]
- <date-part: string>
- <key-list: string-list>
-
- The currentdate test is similar to the date test, except that it
- operates on the current date/time rather than a value extracted from
- the message header. In particular, the ":zone" and date-part
- arguments are the same as those in the date test.
-
- All currentdate tests in a single Sieve script MUST refer to the same
- point in time during execution of the script.
-
- The :count value of a currentdate test is always 1.
-
-5.1. Examples
-
- The simplest use of currentdate is to have an action that only
- operates at certain times. For example, a user might want to have
- messages redirected to their pager after business hours and on
- weekends:
-
-
-
-
-
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-
- require ["date", "relational"];
- if anyof(currentdate :is "weekday" "0",
- currentdate :is "weekday" "6",
- currentdate :value "lt" "hour" "09",
- currentdate :value "ge" "hour" "17")
- { redirect "pager@example.com"; }
-
- Currentdate can be used to set up vacation [RFC5230] responses in
- advance and to stop response generation automatically:
-
- require ["date", "relational", "vacation"];
- if allof(currentdate :value "ge" "date" "2007-06-30",
- currentdate :value "le" "date" "2007-07-07")
- { vacation :days 7 "I'm away during the first week in July."; }
-
- Currentdate may also be used in conjunction with the variables
- extension to pass time-dependent arguments to other tests and
- actions. The following Sieve places messages in a folder named
- according to the current month and year:
-
- require ["date", "variables", "fileinto"];
- if currentdate :matches "month" "*" { set "month" "${1}"; }
- if currentdate :matches "year" "*" { set "year" "${1}"; }
- fileinto "${month}-${year}";
-
- Finally, currentdate can be used in conjunction with the editheader
- extension to insert a header-field containing date/time information:
-
- require ["variables", "date", "editheader"];
- if currentdate :matches "std11" "*"
- {addheader "Processing-date" "${0}";}
-
-6. Index Extension
-
- The "index" extension, if specified, adds optional :index and :last
- arguments to the header, address, and date tests as follows:
-
- Syntax: date [":index" <fieldno: number> [":last"]]
- [<":zone" <time-zone: string>> / ":originalzone"]
- [COMPARATOR] [MATCH-TYPE] <header-name: string>
- <date-part: string> <key-list: string-list>
-
-
- Syntax: header [":index" <fieldno: number> [":last"]]
- [COMPARATOR] [MATCH-TYPE]
- <header-names: string-list> <key-list: string-list>
-
-
-
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-
-
- Syntax: address [":index" <fieldno: number> [":last"]]
- [ADDRESS-PART] [COMPARATOR] [MATCH-TYPE]
- <header-list: string-list> <key-list: string-list>
-
- If :index <fieldno> is specified, the attempts to match a value are
- limited to the header field fieldno (beginning at 1, the first named
- header field). If :last is also specified, the count is backwards; 1
- denotes the last named header field, 2 the second to last, and so on.
- Specifying :last without :index is an error.
-
- :index only counts separate header fields, not multiple occurrences
- within a single field. In particular, :index cannot be used to test
- a specific address in an address list contained within a single
- header field.
-
- Both header and address allow the specification of more than one
- header field name. If more than one header field name is specified,
- all the named header fields are counted in the order specified by the
- header-list.
-
-6.1. Example
-
- Mail delivery may involve multiple hops, resulting in the Received:
- field containing information about when a message first entered the
- local administrative domain being the second or subsequent field in
- the message. As long as the field offset is consistent, it can be
- tested:
-
- # Implement the Internet-Draft cutoff date check assuming the
- # second Received: field specifies when the message first
- # entered the local email infrastructure.
- require ["date", "relational", "index"];
- if date :value "gt" :index 2 :zone "-0500" "received"
- "iso8601" "2007-02-26T09:00:00-05:00",
- { redirect "aftercutoff@example.org"; }
-
-7. Security Considerations
-
- The facilities defined here, like the facilities in the base Sieve
- specification, operate on message header information that can easily
- be forged. Note, however, that some fields are inherently more
- reliable than others. For example, the Date: field is typically
- inserted by the message sender and can be altered at any point. By
- contrast, the uppermost Received: field is typically inserted by the
- local mail system and is therefore difficult for the sender or an
- intermediary to falsify.
-
-
-
-
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-
-
- Use of the currentdate test makes script behavior inherently less
- predictable and harder to analyze. This may have consequences for
- systems that use script analysis to try and spot problematic scripts.
-
- All of the security considerations given in the base Sieve
- specification also apply to these extensions.
-
-8. IANA Considerations
-
- The following templates specify the IANA registrations of the two
- Sieve extensions specified in this document:
-
- To: iana@iana.org
- Subject: Registration of new Sieve extensions
-
- Capability name: date
- Description: The "date" extension gives Sieve the ability
- to test date and time values.
- RFC number: RFC 5260
- Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
-
- Capability name: index
- Description: The "index" extension provides a means to
- limit header and address tests to specific
- instances when more than one field of a
- given type is present.
- RFC number: RFC 5260
- Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
-
-9. References
-
-9.1. Normative References
-
- [CALGO199] Tantzen, R., "Algorithm 199: Conversions Between Calendar
- Date and Julian Day Number", Collected Algorithms from
- CACM 199.
-
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
- April 2001.
-
- [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
- Internet: Timestamps", RFC 3339, July 2002.
-
- [RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
- Language", RFC 5228, January 2008.
-
-
-
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-
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-
-
- [RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering:
- Relational Extension", RFC 5231, January 2008.
-
- [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", STD 68, RFC 5234, January 2008.
-
-9.2. Informative References
-
- [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
- 4rev1", RFC 3501, March 2003.
-
- [RFC5230] Showalter, T. and N. Freed, "Sieve Email Filtering:
- Vacation Extension", RFC 5230, January 2008.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
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-
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-
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-
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-
-
-Appendix A. Julian Date Conversions
-
- The following C routines show how to translate day/month/year
- information to and from modified Julian dates. These routines are
- straightforward translations of the Algol routines specified in CACM
- Algorithm 199 [CALGO199].
-
- Given the day, month, and year, jday returns the modified Julian
- date.
-
- int jday(int year, int month, int day)
- {
- int j, c, ya;
-
- if (month > 2)
- month -= 3;
- else
- {
- month += 9;
- year--;
- }
- c = year / 100;
- ya = year - c * 100;
- return (c * 146097 / 4 + ya * 1461 / 4 + (month * 153 + 2) / 5 +
- day + 1721119);
- }
-
-
-
-
-
-
-
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-
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-
-
-
-
-
-
-
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-
-
- Given j, the modified Julian date, jdate returns the day, month, and
- year.
-
- void jdate(int j, int *year, int *month, int *day)
- {
- int y, m, d;
-
- j -= 1721119;
- y = (j * 4 - 1) / 146097;
- j = j * 4 - y * 146097 - 1;
- d = j / 4;
- j = (d * 4 + 3) / 1461;
- d = d * 4 - j * 1461 + 3;
- d = (d + 4) / 4;
- m = (d * 5 - 3) / 153;
- d = d * 5 - m * 153 - 3;
- *day = (d + 5) / 5;
- *year = y * 100 + j;
- if (m < 10)
- *month = m + 3;
- else
- {
- *month = m - 9;
- *year += 1;
- }
- }
-
-Appendix B. Acknowledgements
-
- Dave Cridland contributed the text describing the proper comparators
- to use with different date-parts. Cyrus Daboo, Frank Ellerman,
- Alexey Melnikov, Chris Newman, Dilyan Palauzov, and Aaron Stone
- provided helpful suggestions and corrections.
-
-Author's Address
-
- Ned Freed
- Sun Microsystems
- 800 Royal Oaks
- Monrovia, CA 91016-6347
- USA
-
- Phone: +1 909 457 4293
- EMail: ned.freed@mrochek.com
-
-
-
-
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-
-
-Full Copyright Statement
-
- Copyright (C) The IETF Trust (2008).
-
- This document is subject to the rights, licenses and restrictions
- contained in BCP 78, and except as set forth therein, the authors
- retain all their rights.
-
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
- THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
- OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
- THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
-
-Intellectual Property
-
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the procedures with respect to rights in RFC documents can be
- found in BCP 78 and BCP 79.
-
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
-
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at
- ietf-ipr@ietf.org.
-
-
-
-
-
-
-
-
-
-
-
-
-Freed Standards Track [Page 13]
-
diff --git a/proto/sieve/rfc5437.txt b/proto/sieve/rfc5437.txt
@@ -1,787 +0,0 @@
-
-
-
-
-
-
-Network Working Group P. Saint-Andre
-Request for Comments: 5437 Cisco
-Category: Standards Track A. Melnikov
- Isode Limited
- January 2009
-
-
- Sieve Notification Mechanism:
- Extensible Messaging and Presence Protocol (XMPP)
-
-Status of This Memo
-
- This document specifies an Internet standards track protocol for the
- Internet community, and requests discussion and suggestions for
- improvements. Please refer to the current edition of the "Internet
- Official Protocol Standards" (STD 1) for the standardization state
- and status of this protocol. Distribution of this memo is unlimited.
-
-Copyright Notice
-
- Copyright (c) 2009 IETF Trust and the persons identified as the
- document authors. All rights reserved.
-
- This document is subject to BCP 78 and the IETF Trust's Legal
- Provisions Relating to IETF Documents (http://trustee.ietf.org/
- license-info) in effect on the date of publication of this document.
- Please review these documents carefully, as they describe your rights
- and restrictions with respect to this document.
-
-Abstract
-
- This document describes a profile of the Sieve extension for
- notifications, to allow notifications to be sent over the Extensible
- Messaging and Presence Protocol (XMPP), also known as Jabber.
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-Saint-Andre & Melnikov Standards Track [Page 1]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-Table of Contents
-
- 1. Introduction ....................................................3
- 1.1. Overview ...................................................3
- 1.2. Terminology ................................................3
- 2. Definition ......................................................3
- 2.1. Notify Parameter "method" ..................................3
- 2.2. Test notify_method_capability ..............................3
- 2.3. Notify Tag ":from" .........................................4
- 2.4. Notify Tag ":importance" ...................................4
- 2.5. Notify Tag ":message" ......................................4
- 2.6. Notify Tag ":options" ......................................4
- 2.7. XMPP Syntax ................................................4
- 3. Examples ........................................................6
- 3.1. Basic Action ...............................................6
- 3.2. Action with "body" .........................................7
- 3.3. Action with "body", ":importance", ":message", and
- "subject" ..................................................7
- 3.4. Action with ":from", ":message", ":importance",
- "body", and "subject" ......................................8
- 4. Requirements Conformance ........................................9
- 5. Internationalization Considerations ............................10
- 6. Security Considerations ........................................11
- 7. IANA Considerations ............................................12
- 8. References .....................................................12
- 8.1. Normative References ......................................12
- 8.2. Informative References ....................................13
-
-
-
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-Saint-Andre & Melnikov Standards Track [Page 2]
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-
-
-1. Introduction
-
-1.1. Overview
-
- The [NOTIFY] extension to the [SIEVE] mail filtering language is a
- framework for providing notifications by employing URIs to specify
- the notification mechanism. This document defines how xmpp URIs (see
- [XMPP-URI]) are used to generate notifications via the Extensible
- Messaging and Presence Protocol [XMPP], which is widely implemented
- in Jabber instant messaging technologies.
-
-1.2. Terminology
-
- This document inherits terminology from [NOTIFY], [SIEVE], and
- [XMPP]. In particular, the terms "parameter" and "tag" are used as
- described in [NOTIFY] to refer to aspects of Sieve scripts, and the
- term "key" is used as described in [XMPP-URI] to refer to aspects of
- an XMPP URI.
-
- The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
- "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
- RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
- interpreted as described in [TERMS].
-
-2. Definition
-
-2.1. Notify Parameter "method"
-
- The "method" parameter MUST be a URI that conforms to the xmpp URI
- scheme (as specified in [XMPP-URI]) and that identifies an XMPP
- account associated with the email inbox. The URI MAY include the
- resource identifier of an XMPP address and/or the query component
- portion of an XMPP URI, but SHOULD NOT include an authority component
- or fragment identifier component. The processing application MUST
- extract an XMPP address from the URI in accordance with the
- processing rules specified in [XMPP-URI]. The resulting XMPP address
- MUST be encapsulated in XMPP syntax as the value of the XMPP 'to'
- attribute.
-
-2.2. Test notify_method_capability
-
- In response to a notify_method_capability test for the "online"
- notification-capability, an implementation SHOULD return a value of
- "yes" if it has knowledge of an active presence session (see
- [XMPP-IM]) for the specified XMPP notification-uri; otherwise, it
- SHOULD return a value of "maybe" (since typical XMPP systems may not
- allow a Sieve engine to gain knowledge about the presence of XMPP
- entities).
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 3]
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-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-2.3. Notify Tag ":from"
-
- If included, the ":from" tag MUST be an electronic address that
- conforms to the "Mailbox" rule defined in [RFC5321]. The value of
- the ":from" tag MAY be included in the human-readable XML character
- data of the XMPP notification; alternatively or in addition, it MAY
- be transformed into formal XMPP syntax, in which case it MUST be
- encapsulated as the value of an XMPP SHIM (Stanza Headers and
- Internet Metadata) [SHIM] header named "Resent-From".
-
-2.4. Notify Tag ":importance"
-
- The ":importance" tag has no special meaning for this notification
- mechanism, and this specification puts no restriction on its use.
- The value of the ":importance" tag MAY be transformed into XMPP
- syntax (in addition to or instead of including appropriate text in
- the XML character data of the XMPP <body/> element); if so, it SHOULD
- be encapsulated as the value of an XMPP SHIM (Stanza Headers and
- Internet Metadata) [SHIM] header named "Urgency", where the XML
- character of that header is "high" if the value of the ":importance"
- tag is "1", "medium" if the value of the ":importance" tag is "2",
- and "low" if the value of the ":importance" tag is "3".
-
-2.5. Notify Tag ":message"
-
- If the ":message" tag is included, that string MUST be transformed
- into the XML character data of an XMPP <body/> element (where the
- string is generated according to the guidelines specified in Section
- 3.6 of [NOTIFY]).
-
-2.6. Notify Tag ":options"
-
- The ":options" tag has no special meaning for this notification
- mechanism. Any handling of this tag is the responsibility of an
- implementation.
-
-2.7. XMPP Syntax
-
- The xmpp mechanism results in the sending of an XMPP message to
- notify a recipient about an email message. The general XMPP syntax
- is as follows:
-
- o The notification MUST be an XMPP <message/> stanza.
-
-
-
-
-
-
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-Saint-Andre & Melnikov Standards Track [Page 4]
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-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- o The value of the XMPP 'from' attribute SHOULD be the XMPP address
- of the notification service associated with the Sieve engine or
- the XMPP address of the entity to be notified. The value of the
- XMPP 'from' attribute MUST NOT be generated from the Sieve ":from"
- tag.
-
- o The value of the XMPP 'to' attribute MUST be the XMPP address
- specified in the XMPP URI contained in the "method" notify
- parameter.
-
- o The value of the XMPP 'type' attribute MUST be 'headline' or
- 'normal'.
-
- o The XMPP <message/> stanza MUST include a <body/> child element.
- If the ":message" tag is included in the Sieve script, that string
- MUST be used as the XML character data of the <body/> element. If
- not and if the XMPP URI contained in the "method" notify parameter
- specified a "body" key in the query component, that value SHOULD
- be used. Otherwise, the XML character data SHOULD be some
- configurable text indicating that the message is a Sieve
- notification.
-
- o The XMPP <message/> stanza MAY include a <subject/> child element.
- If the XMPP URI contained in the "method" notify parameter
- specified a "subject" key in the query component, that value
- SHOULD be used as the XML character data of the <subject/>
- element. Otherwise, the XML character data SHOULD be some
- configurable text indicating that the message is a Sieve
- notification.
-
- o The XMPP <message/> stanza SHOULD include a URI, for the recipient
- to use as a hint in locating the message, encapsulated as the XML
- character data of a <url/> child element of an <x/> element
- qualified by the 'jabber:x:oob' namespace, as specified in [OOB].
- If included, the URI SHOULD be an Internet Message Access Protocol
- [IMAP] URL that specifies the location of the message, as defined
- in [IMAP-URL], but MAY be another URI type that can specify or
- hint at the location of an email message, such as a URI for an
- HTTP resource [HTTP] or a Post Office Protocol Version 3 (POP3)
- mailbox [POP-URL] at which the message can be accessed. It is not
- expected that an XMPP user agent shall directly handle such a URI,
- but instead that it shall invoke an appropriate helper application
- to handle the URI.
-
- o The XMPP <message/> stanza MAY include an XMPP SHIM (Stanza
- Headers and Internet Metadata) [SHIM] header named "Resent-From".
- If the Sieve script included a ":from" tag, the "Resent-From"
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 5]
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-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- value MUST be the value of the ":from" tag; otherwise, the
- "Resent-From" value SHOULD be the envelope recipient address of
- the original email message that triggered the notification.
-
-3. Examples
-
- In the following examples, the sender of the email has an address of
- <mailto:juliet@example.org>, the entity to be notified has an email
- address of <mailto:romeo@example.com> and an XMPP address of
- romeo@im.example.com (resulting in an XMPP URI of
- <xmpp:romeo@im.example.com>), and the notification service associated
- with the Sieve engine has an XMPP address of notify.example.com.
-
- Note: In the following examples, line breaks are included in XMPP
- URIs solely for the purpose of readability.
-
-3.1. Basic Action
-
- The following is a basic Sieve notify action with only a method. The
- XML character data of the XMPP <body/> and <subject/> elements are
- therefore generated by the Sieve engine based on configuration. In
- addition, the Sieve engine includes a URI pointing to the message.
-
- Basic action (Sieve syntax)
-
- notify "xmpp:romeo@im.example.com"
-
- The resulting XMPP <message/> stanza might be as follows:
-
- Basic action (XMPP syntax)
-
- <message from='notify.example.com'
- to='romeo@im.example.com'
- type='headline'
- xml:lang='en'>
- <subject>SIEVE</subject>
- <body><juliet@example.com> You got mail.</body>
- <x xmlns='jabber:x:oob'>
- <url>
- imap://romeo@example.com/INBOX;UIDVALIDITY=385759043/;UID=18
- </url>
- </x>
- </message>
-
-
-
-
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 6]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-3.2. Action with "body"
-
- The following action contains a "body" key in the query component of
- the XMPP URI but no ":message" tag in the Sieve script. As a result,
- the XML character data of the XMPP <body/> element in the XMPP
- notification is taken from the XMPP URI. In addition, the Sieve
- engine includes a URI pointing to the message.
-
- Action with "body" (Sieve syntax)
-
- notify "xmpp:romeo@im.example.com?message
- ;body=Wherefore%20art%20thou%3F"
-
- The resulting XMPP <message/> stanza might be as follows.
-
- Action with "body" (XMPP syntax)
-
- <message from='notify.example.com'
- to='romeo@im.example.com'
- type='headline'
- xml:lang='en'>
- <subject>SIEVE</subject>
- <body>Wherefore art thou?</body>
- <x xmlns='jabber:x:oob'>
- <url>
- imap://romeo@example.com/INBOX;UIDVALIDITY=385759044/;UID=19
- </url>
- </x>
- </message>
-
-3.3. Action with "body", ":importance", ":message", and "subject"
-
- The following action specifies an ":importance" tag and a ":message"
- tag in the Sieve script, as well as a "body" key and a "subject" key
- in the query component of the XMPP URI. As a result, the ":message"
- tag from the Sieve script overrides the "body" key from the XMPP URI
- when generating the XML character data of the XMPP <body/> element.
- In addition, the Sieve engine includes a URI pointing to the message.
-
- Action with "body", ":importance", ":message", and "subject" (Sieve
- syntax)
-
- notify :importance "1"
- :message "Contact Juliet immediately!"
- "xmpp:romeo@im.example.com?message
- ;body=You%27re%20in%20trouble
- ;subject=ALERT%21"
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 7]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- The resulting XMPP <message/> stanza might be as follows.
-
- Action with "body", ":importance", ":message", and "subject" (XMPP
- syntax)
-
- <message from='notify.example.com'
- to='romeo@im.example.com'
- type='headline'
- xml:lang='en'>
- <subject>ALERT!</subject>
- <body>Contact Juliet immediately!</body>
- <headers xmlns='http://jabber.org/protocol/shim'>
- <header name='Urgency'>high</header>
- </headers>
- <x xmlns='jabber:x:oob'>
- <url>
- imap://romeo@example.com/INBOX;UIDVALIDITY=385759045/;UID=20
- </url>
- </x>
- </message>
-
-3.4. Action with ":from", ":message", ":importance", "body", and
- "subject"
-
- The following action specifies a ":from" tag, an ":importance" tag,
- and a ":message" tag in the Sieve script, as well as a "body" key and
- a "subject" key in the query component of the XMPP URI. As a result,
- the ":message" tag from the Sieve script overrides the "body" key
- from the XMPP URI when generating the XML character data of the XMPP
- <body/> element. In addition, the Sieve engine includes a URI
- pointing to the message, as well as an XMPP SHIM (Stanza Headers and
- Internet Metadata) [SHIM] header named "Resent-From" (which
- encapsulates the value of the ":from" tag).
-
- Action with ":from", ":importance", ":message", "body", and "subject"
- (Sieve syntax)
-
- notify :from "romeo.my.romeo@example.com"
- :importance "1"
- :message "Contact Juliet immediately!"
- "xmpp:romeo@im.example.com?message
- ;body=You%27re%20in%20trouble
- ;subject=ALERT%21"
-
- The resulting XMPP <message/> stanza might be as follows.
-
-
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 8]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- Action with ":from", ":importance", ":message", "body", and "subject"
- (XMPP syntax)
-
- <message from='notify.example.com'
- to='romeo@im.example.com'
- type='headline'
- xml:lang='en'>
- <subject>ALERT!</subject>
- <body>Contact Juliet immediately!</body>
- <headers xmlns='http://jabber.org/protocol/shim'>
- <header name='Resent-From'>romeo.my.romeo@example.com</header>
- <header name='Urgency'>high</header>
- </headers>
- <x xmlns='jabber:x:oob'>
- <url>
- imap://romeo@example.com/INBOX;UIDVALIDITY=385759045/;UID=21
- </url>
- </x>
- </message>
-
-4. Requirements Conformance
-
- Section 3.8 of [NOTIFY] specifies a set of requirements for Sieve
- notification methods. The conformance of the xmpp notification
- mechanism is provided here.
-
- 1. An implementation of the xmpp notification method SHOULD NOT
- modify the final notification text (e.g., to limit the length);
- however, a given deployment MAY do so (e.g., if recipients pay
- per character or byte for XMPP messages). Modification of
- characters themselves should not be necessary, since XMPP
- character data is encoded in [UTF-8].
-
- 2. An implementation MAY ignore parameters specified in the
- ":from", ":importance", and ":options" tags.
-
- 3. There is no recommended default message for an implementation to
- include if the ":message" tag is not specified.
-
- 4. A notification sent via the xmpp notification method MAY include
- a timestamp in the textual message.
-
- 5. The value of the XMPP 'from' attribute MUST be the XMPP address
- of the notification service associated with the Sieve engine.
- The value of the Sieve ":from" tag MAY be transformed into the
- value of an XMPP SHIM (Stanza Headers and Internet Metadata)
- [SHIM] header named "Resent-From".
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 9]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- 6. The value of the XMPP 'to' attribute MUST be the XMPP address
- specified in the XMPP URI contained in the "method" parameter.
-
- 7. In accordance with [XMPP-URI], an implementation MUST ignore any
- URI action or key it does not understand (i.e., the URI MUST be
- processed as if the action or key were not present). It is
- RECOMMENDED to support the XMPP "message" query type (see
- [QUERIES]) and the associated "body" and "subject" keys, which
- SHOULD be mapped to the XMPP <body/> and <subject/> child
- elements of the XMPP <message/> stanza, respectively. However,
- if included, then the Sieve notify ":message" tag MUST be mapped
- to the XMPP <body/> element, overriding the "body" key (if any)
- included in the XMPP URI.
-
- 8. An implementation MUST NOT include any other extraneous
- information not specified in parameters to the notify action.
-
- 9. In response to a notify_method_capability test for the "online"
- notification-capability, an implementation SHOULD return a value
- of "yes" if it has knowledge of an active presence session (see
- [XMPP-IM]) for the specified XMPP notification-uri, but only if
- the entity that requested the test is authorized to know the
- presence of the associated XMPP entity (e.g., via explicit
- presence subscription as specified in [XMPP-IM]); otherwise, it
- SHOULD return a value of "maybe" (since typical XMPP systems may
- not allow a Sieve engine to gain knowledge about the presence of
- XMPP entities).
-
- 10. An implementation SHOULD NOT attempt to retry delivery of a
- notification if it receives an XMPP error of type "auth" or
- "cancel", MAY attempt to retry delivery if it receives an XMPP
- error of type "wait", and MAY attempt to retry delivery if it
- receives an XMPP error of "modify", but only if it makes
- appropriate modifications to the notification (see [XMPP]); in
- any case, the number of retries SHOULD be limited to a
- configurable number no less than 3 and no more than 10. An
- implementation MAY throttle notifications if the number of
- notifications within a given time period becomes excessive
- according to local service policy. Duplicate suppression (if
- any) is a matter of implementation and is not specified herein.
-
-5. Internationalization Considerations
-
- Although an XMPP address may contain nearly any [UNICODE] character,
- the value of the "method" parameter MUST be a Uniform Resource
- Identifier (see [URI]) rather than an Internationalized Resource
- Identifier (see [IRI]). The rules specified in [XMPP-URI] MUST be
- followed when generating XMPP URIs.
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 10]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
- In accordance with Section 13 of RFC 3920, all data sent over XMPP
- MUST be encoded in [UTF-8].
-
-6. Security Considerations
-
- Depending on the information included, sending a notification can be
- comparable to forwarding mail to the notification recipient. Care
- must be taken when forwarding mail automatically, to ensure that
- confidential information is not sent into an insecure environment.
- In particular, implementations MUST conform to the security
- considerations given in [NOTIFY], [SIEVE], and [XMPP].
-
- [NOTIFY] specifies that a notification method MUST provide mechanisms
- for avoiding notification loops. One type of notification loop can
- be caused by message forwarding; however, such loops are prevented
- because XMPP does not support the forwarding of messages from one
- XMPP address to another. Another type of notification loop can be
- caused by auto-replies to XMPP messages received by the XMPP
- notification service associated with the Sieve engine; therefore,
- such a service MUST NOT auto-reply to XMPP messages it receives.
-
- A common use case might be for a user to create a script that enables
- the Sieve engine to act differently if the user is currently
- available at a particular type of service (e.g., send notifications
- to the user's XMPP address if the user has an active session at an
- XMPP service). Whether the user is currently available can be
- determined by means of a notify_method_capability test for the
- "online" notification-capability. In XMPP, information about current
- network availability is called "presence" (see also [MODEL]). Since
- [XMPP-IM] requires that a user must approve a presence subscription
- before an entity can gain access to the user's presence information,
- a limited but reasonably safe implementation might be for the Sieve
- engine to request a subscription to the user's presence. The user
- would then need to approve that subscription request so that the
- Sieve engine can act appropriately depending on whether the user is
- online or offline. However, the Sieve engine MUST NOT use the user's
- presence information when processing scripts on behalf of a script
- owner other than the user, unless the Sieve engine has explicit
- knowledge (e.g., via integration with an XMPP server's presence
- authorization rules) that the script owner is authorized to know the
- user's presence. While it would be possible to design a more
- advanced approach to the delegation of presence authorization, any
- such approach is left to future standards work.
-
-
-
-
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 11]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-7. IANA Considerations
-
- The following template provides the IANA registration of the Sieve
- notification mechanism specified in this document:
-
- To: iana@iana.org
- Subject: Registration of new Sieve notification mechanism
- Mechanism name: xmpp
- Mechanism URI: RFC 5122 [XMPP-URI]
- Mechanism-specific options: none
- Permanent and readily available reference: RFC 5437
- Person and email address to contact for further information:
- Peter Saint-Andre <registrar@xmpp.org>
-
- This information has been added to the list of Sieve notification
- mechanisms maintained at <http://www.iana.org>.
-
-8. References
-
-8.1. Normative References
-
- [NOTIFY] Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
- Martin, "Sieve Email Filtering: Extension for
- Notifications", RFC 5435, January 2009.
-
- [OOB] Saint-Andre, P., "Out of Band Data", XSF XEP 0066,
- August 2006.
-
- [QUERIES] Saint-Andre, P., "XMPP URI Scheme Query Components", XSF
- XEP 0147, September 2006.
-
- [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
- October 2008.
-
- [SHIM] Saint-Andre, P. and J. Hildebrand, "Stanza Headers and
- Internet Metadata", XSF XEP 0131, July 2006.
-
- [SIEVE] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
- Filtering Language", RFC 5228, January 2008.
-
- [TERMS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [XMPP-URI] Saint-Andre, P., "Internationalized Resource Identifiers
- (IRIs) and Uniform Resource Identifiers (URIs) for the
- Extensible Messaging and Presence Protocol (XMPP)",
- RFC 5122, February 2008.
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 12]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-8.2. Informative References
-
- [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
- Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
- Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
-
- [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
- 4rev1", RFC 3501, March 2003.
-
- [IMAP-URL] Melnikov, A. and C. Newman, "IMAP URL Scheme", RFC 5092,
- November 2007.
-
- [IRI] Duerst, M. and M. Suignard, "Internationalized Resource
- Identifiers (IRIs)", RFC 3987, January 2005.
-
- [MODEL] Day, M., Rosenberg, J., and H. Sugano, "A Model for
- Presence and Instant Messaging", RFC 2778, February 2000.
-
- [POP-URL] Gellens, R., "POP URL Scheme", RFC 2384, August 1998.
-
- [UNICODE] The Unicode Consortium, "The Unicode Standard, Version
- 3.2.0", 2000.
-
- The Unicode Standard, Version 3.2.0 is defined by The
- Unicode Standard, Version 3.0 (Reading, MA, Addison-
- Wesley, 2000. ISBN 0-201-61633-5), as amended by the
- Unicode Standard Annex #27: Unicode 3.1
- (http://www.unicode.org/reports/tr27/) and by the Unicode
- Standard Annex #28: Unicode 3.2
- (http://www.unicode.org/reports/tr28/).
-
- [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
- Resource Identifier (URI): Generic Syntax", STD 66,
- RFC 3986, January 2005.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", STD 63, RFC 3629, November 2003.
-
- [XMPP] Saint-Andre, P., "Extensible Messaging and Presence
- Protocol (XMPP): Core", RFC 3920, October 2004.
-
- [XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence
- Protocol (XMPP): Instant Messaging and Presence",
- RFC 3921, October 2004.
-
-
-
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 13]
-
-RFC 5437 Sieve Notify Method: XMPP January 2009
-
-
-Authors' Addresses
-
- Peter Saint-Andre
- Cisco
-
- EMail: psaintan@cisco.com
-
-
- Alexey Melnikov
- Isode Limited
-
- EMail: Alexey.Melnikov@isode.com
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Saint-Andre & Melnikov Standards Track [Page 14]
-
diff --git a/proto/sieve/rfc5804.txt b/proto/sieve/rfc5804.txt
@@ -1,2747 +0,0 @@
-
-
-
-
-
-
-Internet Engineering Task Force (IETF) A. Melnikov, Ed.
-Request for Comments: 5804 Isode Limited
-Category: Standards Track T. Martin
-ISSN: 2070-1721 BeThereBeSquare, Inc.
- July 2010
-
-
- A Protocol for Remotely Managing Sieve Scripts
-
-Abstract
-
- Sieve scripts allow users to filter incoming email. Message stores
- are commonly sealed servers so users cannot log into them, yet users
- must be able to update their scripts on them. This document
- describes a protocol "ManageSieve" for securely managing Sieve
- scripts on a remote server. This protocol allows a user to have
- multiple scripts, and also alerts a user to syntactically flawed
- scripts.
-
-Status of This Memo
-
- This is an Internet Standards Track document.
-
- This document is a product of the Internet Engineering Task Force
- (IETF). It represents the consensus of the IETF community. It has
- received public review and has been approved for publication by the
- Internet Engineering Steering Group (IESG). Further information on
- Internet Standards is available in Section 2 of RFC 5741.
-
- Information about the current status of this document, any errata,
- and how to provide feedback on it may be obtained at
- http://www.rfc-editor.org/info/rfc5804.
-
-Copyright Notice
-
- Copyright (c) 2010 IETF Trust and the persons identified as the
- document authors. All rights reserved.
-
- This document is subject to BCP 78 and the IETF Trust's Legal
- Provisions Relating to IETF Documents
- (http://trustee.ietf.org/license-info) in effect on the date of
- publication of this document. Please review these documents
- carefully, as they describe your rights and restrictions with respect
- to this document. Code Components extracted from this document must
- include Simplified BSD License text as described in Section 4.e of
- the Trust Legal Provisions and are provided without warranty as
- described in the Simplified BSD License.
-
-
-
-
-Melnikov & Martin Standards Track [Page 1]
-
-RFC 5804 ManageSieve July 2010
-
-
-Table of Contents
-
- 1. Introduction ....................................................3
- 1.1. Commands and Responses .....................................3
- 1.2. Syntax .....................................................3
- 1.3. Response Codes .............................................3
- 1.4. Active Script ..............................................6
- 1.5. Quotas .....................................................6
- 1.6. Script Names ...............................................6
- 1.7. Capabilities ...............................................7
- 1.8. Transport ..................................................9
- 1.9. Conventions Used in This Document .........................10
- 2. Commands .......................................................10
- 2.1. AUTHENTICATE Command ......................................11
- 2.1.1. Use of SASL PLAIN Mechanism over TLS ...............16
- 2.2. STARTTLS Command ..........................................16
- 2.2.1. Server Identity Check ..............................17
- 2.3. LOGOUT Command ............................................20
- 2.4. CAPABILITY Command ........................................20
- 2.5. HAVESPACE Command .........................................20
- 2.6. PUTSCRIPT Command .........................................21
- 2.7. LISTSCRIPTS Command .......................................23
- 2.8. SETACTIVE Command .........................................24
- 2.9. GETSCRIPT Command .........................................25
- 2.10. DELETESCRIPT Command .....................................25
- 2.11. RENAMESCRIPT Command .....................................26
- 2.12. CHECKSCRIPT Command ......................................27
- 2.13. NOOP Command .............................................28
- 2.14. Recommended Extensions ...................................28
- 2.14.1. UNAUTHENTICATE Command ............................28
- 3. Sieve URL Scheme ...............................................29
- 4. Formal Syntax ..................................................31
- 5. Security Considerations ........................................37
- 6. IANA Considerations ............................................38
- 6.1. ManageSieve Capability Registration Template ..............39
- 6.2. Registration of Initial ManageSieve Capabilities ..........39
- 6.3. ManageSieve Response Code Registration Template ...........41
- 6.4. Registration of Initial ManageSieve Response Codes ........41
- 7. Internationalization Considerations ............................46
- 8. Acknowledgements ...............................................46
- 9. References .....................................................47
- 9.1. Normative References ......................................47
- 9.2. Informative References ....................................48
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 2]
-
-RFC 5804 ManageSieve July 2010
-
-
-1. Introduction
-
-1.1. Commands and Responses
-
- A ManageSieve connection consists of the establishment of a client/
- server network connection, an initial greeting from the server, and
- client/server interactions. These client/server interactions consist
- of a client command, server data, and a server completion result
- response.
-
- All interactions transmitted by client and server are in the form of
- lines, that is, strings that end with a CRLF. The protocol receiver
- of a ManageSieve client or server is either reading a line or reading
- a sequence of octets with a known count followed by a line.
-
-1.2. Syntax
-
- ManageSieve is a line-oriented protocol much like [IMAP] or [ACAP],
- which runs over TCP. There are three data types: atoms, numbers and
- strings. Strings may be quoted or literal. See [ACAP] for detailed
- descriptions of these types.
-
- Each command consists of an atom (the command name) followed by zero
- or more strings and numbers terminated by CRLF.
-
- All client queries are replied to with either an OK, NO, or BYE
- response. Each response may be followed by a response code (see
- Section 1.3) and by a string consisting of human-readable text in the
- local language (as returned by the LANGUAGE capability; see
- Section 1.7), encoded in UTF-8 [UTF-8]. The contents of the string
- SHOULD be shown to the user ,and implementations MUST NOT attempt to
- parse the message for meaning.
-
- The BYE response SHOULD be used if the server wishes to close the
- connection. A server may wish to do this because the client was idle
- for too long or there were too many failed authentication attempts.
- This response can be issued at any time and should be immediately
- followed by a server hang-up of the connection. If a server has an
- inactivity timeout resulting in client autologout, it MUST be no less
- than 30 minutes after successful authentication. The inactivity
- timeout MAY be less before authentication.
-
-1.3. Response Codes
-
- An OK, NO, or BYE response from the server MAY contain a response
- code to describe the event in a more detailed machine-parsable
- fashion. A response code consists of data inside parentheses in the
- form of an atom, possibly followed by a space and arguments.
-
-
-
-Melnikov & Martin Standards Track [Page 3]
-
-RFC 5804 ManageSieve July 2010
-
-
- Response codes are defined when there is a specific action that a
- client can take based upon the additional information. In order to
- support future extension, the response code is represented as a
- slash-separated (Solidus, %x2F) hierarchy with each level of
- hierarchy representing increasing detail about the error. Response
- codes MUST NOT start with the Solidus character. Clients MUST
- tolerate additional hierarchical response code detail that they don't
- understand. For example, if the client supports the "QUOTA" response
- code, but doesn't understand the "QUOTA/MAXSCRIPTS" response code, it
- should treat "QUOTA/MAXSCRIPTS" as "QUOTA".
-
- Client implementations MUST tolerate (ignore) response codes that
- they do not recognize.
-
- The currently defined response codes are the following:
-
- AUTH-TOO-WEAK
-
- This response code is returned in the NO or BYE response from an
- AUTHENTICATE command. It indicates that site security policy forbids
- the use of the requested mechanism for the specified authentication
- identity.
-
- ENCRYPT-NEEDED
-
- This response code is returned in the NO or BYE response from an
- AUTHENTICATE command. It indicates that site security policy
- requires the use of a strong encryption mechanism for the specified
- authentication identity and mechanism.
-
- QUOTA
-
- If this response code is returned in the NO/BYE response, it means
- that the command would have placed the user above the site-defined
- quota constraints. If this response code is returned in the OK
- response, it can mean that the user's storage is near its quota, or
- it can mean that the account exceeded its quota but that the
- condition is being allowed by the server (the server supports
- so-called soft quotas). The QUOTA response code has two more
- detailed variants: "QUOTA/MAXSCRIPTS" (the maximum number of per-user
- scripts) and "QUOTA/MAXSIZE" (the maximum script size).
-
- REFERRAL
-
- This response code may be returned with a BYE result from any
- command, and includes a mandatory parameter that indicates what
- server to access to manage this user's Sieve scripts. The server
- will be specified by a Sieve URL (see Section 3). The scriptname
-
-
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-
- portion of the URL MUST NOT be specified. The client should
- authenticate to the specified server and use it for all further
- commands in the current session.
-
- SASL
-
- This response code can occur in the OK response to a successful
- AUTHENTICATE command and includes the optional final server response
- data from the server as specified by [SASL].
-
- TRANSITION-NEEDED
-
- This response code occurs in a NO response of an AUTHENTICATE
- command. It indicates that the user name is valid, but the entry in
- the authentication database needs to be updated in order to permit
- authentication with the specified mechanism. This is typically done
- by establishing a secure channel using TLS, verifying server identity
- as specified in Section 2.2.1, and finally authenticating once using
- the [PLAIN] authentication mechanism. The selected mechanism SHOULD
- then work for authentications in subsequent sessions.
-
- This condition can happen if a user has an entry in a system
- authentication database such as Unix /etc/passwd, but does not have
- credentials suitable for use by the specified mechanism.
-
- TRYLATER
-
- A command failed due to a temporary server failure. The client MAY
- continue using local information and try the command later. This
- response code only makes sense when returned in a NO/BYE response.
-
- ACTIVE
-
- A command failed because it is not allowed on the active script, for
- example, DELETESCRIPT on the active script. This response code only
- makes sense when returned in a NO/BYE response.
-
- NONEXISTENT
-
- A command failed because the referenced script name doesn't exist.
- This response code only makes sense when returned in a NO/BYE
- response.
-
- ALREADYEXISTS
-
- A command failed because the referenced script name already exists.
- This response code only makes sense when returned in a NO/BYE
- response.
-
-
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-
- TAG
-
- This response code name is followed by a string specified in the
- command. See Section 2.13 for a possible use case.
-
- WARNINGS
-
- This response code MAY be returned by the server in the OK response
- (but it might be returned with the NO/BYE response as well) and
- signals the client that even though the script is syntactically
- valid, it might contain errors not intended by the script writer.
- This response code is typically returned in response to PUTSCRIPT
- and/or CHECKSCRIPT commands. A client seeing such response code
- SHOULD present the returned warning text to the user.
-
-1.4. Active Script
-
- A user may have multiple Sieve scripts on the server, yet only one
- script may be used for filtering of incoming messages. This is the
- active script. Users may have zero or one active script and MUST use
- the SETACTIVE command described below for changing the active script
- or disabling Sieve processing. For example, users may have an
- everyday script they normally use and a special script they use when
- they go on vacation. Users can change which script is being used
- without having to download and upload a script stored somewhere else.
-
-1.5. Quotas
-
- Servers SHOULD impose quotas to prevent malicious users from
- overflowing available storage. If a command would place a user over
- a quota setting, servers that impose such quotas MUST reply with a NO
- response containing the QUOTA response code. Client implementations
- MUST be able to handle commands failing because of quota
- restrictions.
-
-1.6. Script Names
-
- A Sieve script name is a sequence of Unicode characters encoded in
- UTF-8 [UTF-8]. A script name MUST comply with Net-Unicode Definition
- (Section 2 of [NET-UNICODE]), with the additional restriction of
- prohibiting the following Unicode characters:
-
- o 0000-001F; [CONTROL CHARACTERS]
-
- o 007F; DELETE
-
- o 0080-009F; [CONTROL CHARACTERS]
-
-
-
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-
- o 2028; LINE SEPARATOR
-
- o 2029; PARAGRAPH SEPARATOR
-
- Sieve script names MUST be at least one octet (and hence Unicode
- character) long. Zero octets script name has a special meaning (see
- Section 2.8). Servers MUST allow names of up to 128 Unicode
- characters in length (which can take up to 512 bytes when encoded in
- UTF-8, not counting the terminating NUL), and MAY allow longer names.
- A server that receives a script name longer than its internal limit
- MUST reject the corresponding operation, in particular it MUST NOT
- truncate the script name.
-
-1.7. Capabilities
-
- Server capabilities are sent automatically by the server upon a
- client connection, or after successful STARTTLS and AUTHENTICATE
- (which establishes a Simple Authentication and Security Layer (SASL))
- commands. Capabilities may change immediately after a successfully
- completed STARTTLS command, and/or immediately after a successfully
- completed AUTHENTICATE command, and/or after a successfully completed
- UNAUTHENTICATE command (see Section 2.14.1). Capabilities MUST
- remain static at all other times.
-
- Clients MAY request the capabilities at a later time by issuing the
- CAPABILITY command described later. The capabilities consist of a
- series of lines each with one or two strings. The first string is
- the name of the capability, which is case-insensitive. The second
- optional string is the value associated with that capability. Order
- of capabilities is arbitrary, but each capability name can appear at
- most once.
-
- The following capabilities are defined in this document:
-
- IMPLEMENTATION - Name of implementation and version. This capability
- MUST always be returned by the server.
-
- SASL - List of SASL mechanisms supported by the server, each
- separated by a space. This list can be empty if and only if STARTTLS
- is also advertised. This means that the client must negotiate TLS
- encryption with STARTTLS first, at which point the SASL capability
- will list a non-empty list of SASL mechanisms.
-
- SIEVE - List of space-separated Sieve extensions (as listed in Sieve
- "require" action [SIEVE]) supported by the Sieve engine. This
- capability MUST always be returned by the server.
-
-
-
-
-
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-
- STARTTLS - If TLS [TLS] is supported by this implementation. Before
- advertising this capability a server MUST verify to the best of its
- ability that TLS can be successfully negotiated by a client with
- common cipher suites. Specifically, a server should verify that a
- server certificate has been installed and that the TLS subsystem has
- successfully initialized. This capability SHOULD NOT be advertised
- once STARTTLS or AUTHENTICATE command completes successfully. Client
- and server implementations MUST implement the STARTTLS extension.
-
- MAXREDIRECTS - Specifies the limit on the number of Sieve "redirect"
- actions a script can perform during a single evaluation. Note that
- this is different from the total number of "redirect" actions a
- script can contain. The value is a non-negative number represented
- as a ManageSieve string.
-
- NOTIFY - A space-separated list of URI schema parts for supported
- notification methods. This capability MUST be specified if the Sieve
- implementation supports the "enotify" extension [NOTIFY].
-
- LANGUAGE - The language (<Language-Tag> from [RFC5646]) currently
- used for human-readable error messages. If this capability is not
- returned, the "i-default" [RFC2277] language is assumed. Note that
- the current language MAY be per-user configurable (i.e., it MAY
- change after authentication).
-
- OWNER - The canonical name of the logged-in user (SASL "authorization
- identity") encoded in UTF-8. This capability MUST NOT be returned in
- unauthenticated state and SHOULD be returned once the AUTHENTICATE
- command succeeds.
-
- VERSION - This capability MUST be returned by servers compliant with
- this document or its successor. For servers compliant with this
- document, the capability value is the string "1.0". Lack of this
- capability means that the server predates this specification and thus
- doesn't support the following commands: RENAMESCRIPT, CHECKSCRIPT,
- and NOOP.
-
- Section 2.14 defines some additional ManageSieve extensions and their
- respective capabilities.
-
- A server implementation MUST return SIEVE, IMPLEMENTATION, and
- VERSION capabilities.
-
- A client implementation MUST ignore any listed capabilities that it
- does not understand.
-
-
-
-
-
-
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-
-
- Example:
-
- S: "IMPlemENTATION" "Example1 ManageSieved v001"
- S: "SASl" "DIGEST-MD5 GSSAPI"
- S: "SIeVE" "fileinto vacation"
- S: "StaRTTLS"
- S: "NOTIFY" "xmpp mailto"
- S: "MAXREdIRECTS" "5"
- S: "VERSION" "1.0"
- S: OK
-
- After successful authentication, this might look like this:
-
- Example:
-
- S: "IMPlemENTATION" "Example1 ManageSieved v001"
- S: "SASl" "DIGEST-MD5 GSSAPI"
- S: "SIeVE" "fileinto vacation"
- S: "NOTIFY" "xmpp mailto"
- S: "OWNER" "alexey@example.com"
- S: "MAXREdIRECTS" "5"
- S: "VERSION" "1.0"
- S: OK
-
-1.8. Transport
-
- The ManageSieve protocol assumes a reliable data stream such as that
- provided by TCP. When TCP is used, a ManageSieve server typically
- listens on port 4190.
-
- Before opening the TCP connection, the ManageSieve client first MUST
- resolve the Domain Name System (DNS) hostname associated with the
- receiving entity and determine the appropriate TCP port for
- communication with the receiving entity. The process is as follows:
-
- 1. Attempt to resolve the hostname using a [DNS-SRV] Service of
- "sieve" and a Proto of "tcp" for the target domain (e.g.,
- "example.net"), resulting in resource records such as
- "_sieve._tcp.example.net.". The result of the SRV lookup, if
- successful, will be one or more combinations of a port and
- hostname; the ManageSieve client MUST resolve the returned
- hostnames to IPv4/IPv6 addresses according to returned SRV record
- weight. IP addresses from the first successfully resolved
- hostname (with the corresponding port number returned by SRV
- lookup) are used to connect to the server. If connection using
- one of the IP addresses fails, the next resolved IP address is
-
-
-
-
-
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-
- used to connect. If connection to all resolved IP addresses
- fails, then the resolution/connect is repeated for the next
- hostname returned by SRV lookup.
-
- 2. If the SRV lookup fails, the fallback SHOULD be a normal IPv4 or
- IPv6 address record resolution to determine the IP address, where
- the port used is the default ManageSieve port of 4190.
-
-1.9. Conventions Used in This Document
-
- The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
- "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in [KEYWORDS].
-
- In examples, "C:" and "S:" indicate lines sent by the client and
- server respectively. Line breaks that do not start a new "C:" or
- "S:" exist for editorial reasons.
-
- Examples of authentication in this document are using DIGEST-MD5
- [DIGEST-MD5] and GSSAPI [GSSAPI] SASL mechanisms.
-
-2. Commands
-
- This section and its subsections describe valid ManageSieve commands.
- Upon initial connection to the server, the client's session is in
- non-authenticated state. Prior to successful authentication, only
- the AUTHENTICATE, CAPABILITY, STARTTLS, LOGOUT, and NOOP (see Section
- 2.13) commands are valid. ManageSieve extensions MAY define other
- commands that are valid in non-authenticated state. Servers MUST
- reject all other commands with a NO response. Clients may pipeline
- commands (send more than one command at a time without waiting for
- completion of the first command). However, a group of commands sent
- together MUST NOT have an AUTHENTICATE (*), a STARTTLS, or a
- HAVESPACE command anywhere but the last command in the list.
-
- (*) - The only exception to this rule is when the AUTHENTICATE
- command contains an initial response for a SASL mechanism that allows
- clients to send data first, the mechanism is known to complete in one
- round trip, and the mechanism doesn't negotiate a SASL security
- layer. Two examples of such SASL mechanisms are PLAIN [PLAIN] and
- EXTERNAL [SASL].
-
-
-
-
-
-
-
-
-
-
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-
-
-2.1. AUTHENTICATE Command
-
- Arguments: String - mechanism
- String - initial data (optional)
-
- The AUTHENTICATE command indicates a SASL [SASL] authentication
- mechanism to the server. If the server supports the requested
- authentication mechanism, it performs an authentication protocol
- exchange to identify and authenticate the user. Optionally, it also
- negotiates a security layer for subsequent protocol interactions. If
- the requested authentication mechanism is not supported, the server
- rejects the AUTHENTICATE command by sending the NO response.
-
- The authentication protocol exchange consists of a series of server
- challenges and client responses that are specific to the selected
- authentication mechanism. A server challenge consists of a string
- (quoted or literal) followed by a CRLF. The contents of the string
- is a base-64 encoding [BASE64] of the SASL data. A client response
- consists of a string (quoted or literal) with the base-64 encoding of
- the SASL data followed by a CRLF. If the client wishes to cancel the
- authentication exchange, it issues a string containing a single "*".
- If the server receives such a response, it MUST reject the
- AUTHENTICATE command by sending a NO reply.
-
- Note that an empty challenge/response is sent as an empty string. If
- the mechanism dictates that the final response is sent by the server,
- this data MAY be placed within the data portion of the SASL response
- code to save a round trip.
-
- The optional initial-response argument to the AUTHENTICATE command is
- used to save a round trip when using authentication mechanisms that
- are defined to send no data in the initial challenge. When the
- initial-response argument is used with such a mechanism, the initial
- empty challenge is not sent to the client and the server uses the
- data in the initial-response argument as if it were sent in response
- to the empty challenge. If the initial-response argument to the
- AUTHENTICATE command is used with a mechanism that sends data in the
- initial challenge, the server MUST reject the AUTHENTICATE command by
- sending the NO response.
-
- The service name specified by this protocol's profile of SASL is
- "sieve".
-
- Reauthentication is not supported by ManageSieve protocol's profile
- of SASL. That is, after a successfully completed AUTHENTICATE
- command, no more AUTHENTICATE commands may be issued in the same
- session. After a successful AUTHENTICATE command completes, a server
- MUST reject any further AUTHENTICATE commands with a NO reply.
-
-
-
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-
-
- However, note that a server may implement the UNAUTHENTICATE
- extension described in Section 2.14.1.
-
- If a security layer is negotiated through the SASL authentication
- exchange, it takes effect immediately following the CRLF that
- concludes the successful authentication exchange for the client, and
- the CRLF of the OK response for the server.
-
- When a security layer takes effect, the ManageSieve protocol is reset
- to the initial state (the state in ManageSieve after a client has
- connected to the server). The server MUST discard any knowledge
- obtained from the client that was not obtained from the SASL (or TLS)
- negotiation itself. Likewise, the client MUST discard any knowledge
- obtained from the server, such as the list of ManageSieve extensions,
- that was not obtained from the SASL (and/or TLS) negotiation itself.
- (Note that a client MAY compare the advertised SASL mechanisms before
- and after authentication in order to detect an active down-
- negotiation attack. See below.)
-
- Once a SASL security layer is established, the server MUST re-issue
- the capability results, followed by an OK response. This is
- necessary to protect against man-in-the-middle attacks that alter the
- capabilities list prior to SASL negotiation. The capability results
- MUST include all SASL mechanisms the server was capable of
- negotiating with that client. This is done in order to allow the
- client to detect an active down-negotiation attack. If a user-
- oriented client detects such a down-negotiation attack, it SHOULD
- either notify the user (it MAY give the user the opportunity to
- continue with the ManageSieve session in this case) or close the
- transport connection and indicate that a down-negotiation attack
- might be in progress. If an automated client detects a down-
- negotiation attack, it SHOULD return or log an error indicating that
- a possible attack might be in progress and/or SHOULD close the
- transport connection.
-
- When both [TLS] and SASL security layers are in effect, the TLS
- encoding MUST be applied (when sending data) after the SASL encoding.
-
- Server implementations SHOULD support SASL proxy authentication so
- that an administrator can administer a user's scripts. Proxy
- authentication is when a user authenticates as herself/himself but
- requests the server to act (authorize) as another user.
-
- The authorization identity generated by this [SASL] exchange is a
- "simple username" (in the sense defined in [SASLprep]), and both
- client and server MUST use the [SASLprep] profile of the [StringPrep]
- algorithm to prepare these names for transmission or comparison. If
- preparation of the authorization identity fails or results in an
-
-
-
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-RFC 5804 ManageSieve July 2010
-
-
- empty string (unless it was transmitted as the empty string), the
- server MUST fail the authentication.
-
- If an AUTHENTICATE command fails with a NO response, the client MAY
- try another authentication mechanism by issuing another AUTHENTICATE
- command. In other words, the client may request authentication types
- in decreasing order of preference.
-
- Note that a failed (NO) response to the AUTHENTICATE command may
- contain one of the following response codes: AUTH-TOO-WEAK, ENCRYPT-
- NEEDED, or TRANSITION-NEEDED. See Section 1.3 for detailed
- description of the relevant conditions.
-
- To ensure interoperability, both client and server implementations of
- the ManageSieve protocol MUST implement the SCRAM-SHA-1 [SCRAM] SASL
- mechanism, as well as [PLAIN] over [TLS].
-
- Note: use of PLAIN over TLS reflects current use of PLAIN over TLS in
- other email-related protocols; however, a longer-term goal is to
- migrate email-related protocols from using PLAIN over TLS to SCRAM-
- SHA-1 mechanism.
-
- Examples (Note that long lines are folded for readability and are not
- part of protocol exchange):
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: "VERSION" "1.0"
- S: OK
- C: Authenticate "DIGEST-MD5"
- S: "cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
- 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
- cyxjaGFyc2V0PXV0Zi04"
- C: "Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
- QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
- aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
- N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
- ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
- A9YXV0aA=="
- S: OK (SASL "cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZ
- mZmZA==")
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- A slightly different variant of the same authentication exchange is:
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "VERSION" "1.0"
- S: "STARTTLS"
- S: OK
- C: Authenticate "DIGEST-MD5"
- S: {136}
- S: cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
- 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
- cyxjaGFyc2V0PXV0Zi04
- C: {300+}
- C: Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
- QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
- aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
- N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
- ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
- A9YXV0aA==
- S: {56}
- S: cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
- C: ""
- S: OK
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 14]
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-RFC 5804 ManageSieve July 2010
-
-
- Another example demonstrating use of SASL PLAIN mechanism under TLS
- follows. This example also demonstrate use of SASL "initial
- response" (the second parameter to the Authenticate command):
-
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" ""
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: OK
- C: STARTTLS
- S: OK
- <TLS negotiation, further commands are under TLS layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN"
- S: "SIEVE" "fileinto vacation"
- S: OK
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xu"
- S: NO
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xz"
- S: NO
- C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xy"
- S: BYE "Too many failed authentication attempts"
- <Server closes connection>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- The following example demonstrates use of SASL "initial response".
- It also demonstrates that an empty response can be sent as a literal
- and that negotiating a SASL security layer results in the server
- re-issuing server capabilities:
-
- C: AUTHENTICATE "GSSAPI" {1488+}
- C: YIIE[...1480 octets here ...]dA==
- S: {208}
- S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKic
- [...114 octets here ...]
- /yzpAy9p+Y0LanLskOTvMc0MnjgAa4YEr3eJ6
- C: {0+}
- C:
- S: {44}
- S: BQQF/wAMAAwAAAAAYRGFAo6W0vIHti8i1UXODgEAEAA=
- C: {44+}
- C: BQQE/wAMAAwAAAAAIsT1iv9UkZApw471iXt6cwEAAAE=
- S: OK
- <Further commands/responses are under SASL security layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "LANGUAGE" "ru"
- S: "MAXREDIRECTS" "3"
- S: ok
-
-2.1.1. Use of SASL PLAIN Mechanism over TLS
-
- This section is normative for ManageSieve client implementations that
- support SASL [PLAIN] over [TLS].
-
- If a ManageSieve client is willing to use SASL PLAIN over TLS to
- authenticate to the ManageSieve server, the client MUST verify the
- server identity (see Section 2.2.1). If the server identity can't be
- verified (e.g., the server has not provided any certificate, or if
- the certificate verification fails), the client MUST NOT attempt to
- authenticate using the SASL PLAIN mechanism.
-
-2.2. STARTTLS Command
-
- Support for STARTTLS command in servers is optional. Its
- availability is advertised with "STARTTLS" capability as described in
- Section 1.7.
-
- The STARTTLS command requests commencement of a TLS [TLS]
- negotiation. The negotiation begins immediately after the CRLF in
- the OK response. After a client issues a STARTTLS command, it MUST
-
-
-
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-
-
- NOT issue further commands until a server response is seen and the
- TLS negotiation is complete.
-
- The STARTTLS command is only valid in non-authenticated state. The
- server remains in non-authenticated state, even if client credentials
- are supplied during the TLS negotiation. The SASL [SASL] EXTERNAL
- mechanism MAY be used to authenticate once TLS client credentials are
- successfully exchanged, but servers supporting the STARTTLS command
- are not required to support the EXTERNAL mechanism.
-
- After the TLS layer is established, the server MUST re-issue the
- capability results, followed by an OK response. This is necessary to
- protect against man-in-the-middle attacks that alter the capabilities
- list prior to STARTTLS. This capability result MUST NOT include the
- STARTTLS capability.
-
- The client MUST discard cached capability information and replace it
- with the new information. The server MAY advertise different
- capabilities after STARTTLS.
-
- Example:
-
- C: StartTls
- S: oK
- <TLS negotiation, further commands are under TLS layer>
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "VERSION" "1.0"
- S: "LANGUAGE" "fr"
- S: ok
-
-2.2.1. Server Identity Check
-
- During the TLS negotiation, the ManageSieve client MUST check its
- understanding of the server hostname/IP address against the server's
- identity as presented in the server Certificate message, in order to
- prevent man-in-the-middle attacks. In this section, the client's
- understanding of the server's identity is called the "reference
- identity".
-
- Checking is performed according to the following rules:
-
- o If the reference identity is a hostname:
-
- 1. If a subjectAltName extension of the SRVName [X509-SRV],
- dNSName [X509] (in that order of preference) type is present
- in the server's certificate, then it SHOULD be used as the
-
-
-
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-
-
- source of the server's identity. Matching is performed as
- described in Section 2.2.1.1, with the exception that no
- wildcard matching is allowed for SRVName type. If the
- certificate contains multiple names (e.g., more than one
- dNSName field), then a match with any one of the fields is
- considered acceptable.
-
- 2. The client MAY use other types of subjectAltName for
- performing comparison.
-
- 3. The server's identity MAY also be verified by comparing the
- reference identity to the Common Name (CN) [RFC4519] value in
- the leaf Relative Distinguished Name (RDN) of the subjectName
- field of the server's certificate. This comparison is
- performed using the rules for comparison of DNS names in
- Section 2.2.1.1, below. Although the use of the Common Name
- value is existing practice, it is deprecated, and
- Certification Authorities are encouraged to provide
- subjectAltName values instead. Note that the TLS
- implementation may represent DNs in certificates according to
- X.500 or other conventions. For example, some X.500
- implementations order the RDNs in a DN using a left-to-right
- (most significant to least significant) convention instead of
- LDAP's right-to-left convention.
-
- o When the reference identity is an IP address, the iPAddress
- subjectAltName SHOULD be used by the client for comparison. The
- comparison is performed as described in Section 2.2.1.2.
-
- If the server identity check fails, user-oriented clients SHOULD
- either notify the user (clients MAY give the user the opportunity to
- continue with the ManageSieve session in this case) or close the
- transport connection and indicate that the server's identity is
- suspect. Automated clients SHOULD return or log an error indicating
- that the server's identity is suspect and/or SHOULD close the
- transport connection. Automated clients MAY provide a configuration
- setting that disables this check, but MUST provide a setting that
- enables it.
-
- Beyond the server identity check described in this section, clients
- should be prepared to do further checking to ensure that the server
- is authorized to provide the service it is requested to provide. The
- client may need to make use of local policy information in making
- this determination.
-
-
-
-
-
-
-
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-
-
-2.2.1.1. Comparison of DNS Names
-
- If the reference identity is an internationalized domain name,
- conforming implementations MUST convert it to the ASCII Compatible
- Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
- before comparison with subjectAltName values of type dNSName.
- Specifically, conforming implementations MUST perform the conversion
- operation specified in Section 4 of [RFC3490] as follows:
-
- o in step 1, the domain name SHALL be considered a "stored string";
-
- o in step 3, set the flag called "UseSTD3ASCIIRules";
-
- o in step 4, process each label with the "ToASCII" operation; and
-
- o in step 5, change all label separators to U+002E (full stop).
-
- After performing the "to-ASCII" conversion, the DNS labels and names
- MUST be compared for equality according to the rules specified in
- Section 3 of [RFC3490]; i.e., once all label separators are replaced
- with U+002E (dot) they are compared in the case-insensitive manner.
-
- The '*' (ASCII 42) wildcard character is allowed in subjectAltName
- values of type dNSName, and then only as the left-most (least
- significant) DNS label in that value. This wildcard matches any
- left-most DNS label in the server name. That is, the subject
- *.example.com matches the server names a.example.com and
- b.example.com, but does not match example.com or a.b.example.com.
-
-2.2.1.2. Comparison of IP Addresses
-
- When the reference identity is an IP address, the identity MUST be
- converted to the "network byte order" octet string representation
- [RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the
- octet string will contain exactly four octets. For IP Version 6, as
- specified in RFC 2460, the octet string will contain exactly sixteen
- octets. This octet string is then compared against subjectAltName
- values of type iPAddress. A match occurs if the reference identity
- octet string and value octet strings are identical.
-
-2.2.1.3. Comparison of Other subjectName Types
-
- Client implementations MAY support matching against subjectAltName
- values of other types as described in other documents.
-
-
-
-
-
-
-
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-
-
-2.3. LOGOUT Command
-
- The client sends the LOGOUT command when it is finished with a
- connection and wishes to terminate it. The server MUST reply with an
- OK response. The server MUST ignore commands issued by the client
- after the LOGOUT command.
-
- The client SHOULD wait for the OK response before closing the
- connection. This avoids the TCP connection going into the TIME_WAIT
- state on the server. In order to avoid going into the TIME_WAIT TCP
- state, the server MAY wait for a short while for the client to close
- the TCP connection first. Whether or not the server waits for the
- client to close the connection, it MUST then close the connection
- itself.
-
- Example:
-
- C: Logout
- S: Ok
- <connection is terminated>
-
-2.4. CAPABILITY Command
-
- The CAPABILITY command requests the server capabilities as described
- earlier in this document. It has no parameters.
-
- Example:
-
- C: CAPABILITY
- S: "IMPLEMENTATION" "Example1 ManageSieved v001"
- S: "VERSION" "1.0"
- S: "SASL" "PLAIN SCRAM-SHA-1 GSSAPI"
- S: "SIEVE" "fileinto vacation"
- S: "STARTTLS"
- S: OK
-
-2.5. HAVESPACE Command
-
- Arguments: String - name
- Number - script size
-
- The HAVESPACE command is used to query the server for available
- space. Clients specify the name they wish to save the script as and
- its size in octets. Both parameters can be used by the server to see
- if the script with the specified name and size is within a user's
- quota(s). For example, the server MAY use the script name to check
- if a script would be replaced or a new one would be created. Servers
- respond with a NO if storing a script with that name and size would
-
-
-
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-
-
- fail or OK otherwise. Clients SHOULD issue this command before
- attempting to place a script on the server.
-
- Note that the OK response from the HAVESPACE command does not
- constitute a guarantee of success as server disk space conditions
- could change between the client issuing the HAVESPACE and the client
- issuing the PUTSCRIPT commands. A QUOTA response code (see
- Section 1.3) remains a possible (albeit unlikely) response to a
- subsequent PUTSCRIPT with the same name and size.
-
- Example:
-
- C: HAVESPACE "myscript" 999999
- S: NO (QUOTA/MAXSIZE) "Quota exceeded"
-
- C: HAVESPACE "foobar" 435
- S: OK
-
-2.6. PUTSCRIPT Command
-
- Arguments: String - Script name
- String - Script content
-
- The PUTSCRIPT command is used by the client to submit a Sieve script
- to the server.
-
- If the script already exists, upon success the old script will be
- overwritten. The old script MUST NOT be overwritten if PUTSCRIPT
- fails in any way. A script of zero length SHOULD be disallowed.
-
- This command places the script on the server. It does not affect
- whether the script is processed on incoming mail, unless it replaces
- the script that is already active. The SETACTIVE command is used to
- mark a script as active.
-
- When submitting large scripts, clients SHOULD use the HAVESPACE
- command beforehand to query if the server is willing to accept a
- script of that size.
-
- The server MUST check the submitted script for validity, which
- includes checking that the script complies with the Sieve grammar
- [SIEVE] and that all Sieve extensions mentioned in the script's
- "require" statement(s) are supported by the Sieve interpreter. (Note
- that if the Sieve interpreter supports the Sieve "ihave" extension
- [I-HAVE], any unrecognized/unsupported extension mentioned in the
- "ihave" test MUST NOT cause the validation failure.) Other checks
- such as validating the supplied command arguments for each command
- MAY be performed. Essentially, the performed validation SHOULD be
-
-
-
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-
-
- the same as performed when compiling the script for execution.
- Implementations that use a binary representation to store compiled
- scripts can extend the validation to a full compilation, in order to
- avoid validating uploaded scripts multiple times.
-
- If the script fails the validation, the server MUST reply with a NO
- response. Any script that fails the validity test MUST NOT be stored
- on the server. The message given with a NO response MUST be human
- readable and SHOULD contain a specific error message giving the line
- number of the first error. Implementors should strive to produce
- helpful error messages similar to those given by programming language
- compilers. Client implementations should note that this may be a
- multiline literal string with more than one error message separated
- by CRLFs. The human-readable message is in the language returned in
- the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
- encoded in UTF-8 [UTF-8].
-
- An OK response MAY contain the WARNINGS response code. In such a
- case the human-readable message that follows the OK response SHOULD
- contain a specific warning message (or messages) giving the line
- number(s) in the script that might contain errors not intended by the
- script writer. The human-readable message is in the language
- returned in the latest LANGUAGE capability (or in "i-default"; see
- Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
- response code SHOULD present the message to the user.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- Examples:
-
- C: Putscript "foo" {31+}
- C: #comment
- C: InvalidSieveCommand
- C:
- S: NO "line 2: Syntax error"
-
- C: Putscript "mysievescript" {110+}
- C: require ["fileinto"];
- C:
- C: if envelope :contains "to" "tmartin+sent" {
- C: fileinto "INBOX.sent";
- C: }
- S: OK
-
- C: Putscript "myforwards" {190+}
- C: redirect "111@example.net";
- C:
- C: if size :under 10k {
- C: redirect "mobile@cell.example.com";
- C: }
- C:
- C: if envelope :contains "to" "tmartin+lists" {
- C: redirect "lists@groups.example.com";
- C: }
- S: OK (WARNINGS) "line 8: server redirect action
- limit is 2, this redirect might be ignored"
-
-2.7. LISTSCRIPTS Command
-
- This command lists the scripts the user has on the server. Upon
- success, a list of CRLF-separated script names (each represented as a
- quoted or literal string) is returned followed by an OK response. If
- there exists an active script, the atom ACTIVE is appended to the
- corresponding script name. The atom ACTIVE MUST NOT appear on more
- than one response line.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- Example:
-
- C: Listscripts
- S: "summer_script"
- S: "vacation_script"
- S: {13}
- S: clever"script
- S: "main_script" ACTIVE
- S: OK
-
- C: listscripts
- S: "summer_script"
- S: "main_script" active
- S: OK
-
-2.8. SETACTIVE Command
-
- Arguments: String - script name
-
- This command sets a script active. If the script name is the empty
- string (i.e., ""), then any active script is disabled. Disabling an
- active script when there is no script active is not an error and MUST
- result in an OK reply.
-
- If the script does not exist on the server, then the server MUST
- reply with a NO response. Such a reply SHOULD contain the
- NONEXISTENT response code.
-
- Examples:
-
- C: Setactive "vacationscript"
- S: Ok
-
- C: Setactive ""
- S: Ok
-
- C: Setactive "baz"
- S: No (NONEXISTENT) "There is no script by that name"
-
- C: Setactive "baz"
- S: No (NONEXISTENT) {31}
- S: There is no script by that name
-
-
-
-
-
-
-
-
-
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-
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-
-
-2.9. GETSCRIPT Command
-
- Arguments: String - script name
-
- This command gets the contents of the specified script. If the
- script does not exist, the server MUST reply with a NO response.
- Such a reply SHOULD contain the NONEXISTENT response code.
-
- Upon success, a string with the contents of the script is returned
- followed by an OK response.
-
- Example:
-
- C: Getscript "myscript"
- S: {54}
- S: #this is my wonderful script
- S: reject "I reject all";
- S:
- S: OK
-
-2.10. DELETESCRIPT Command
-
- Arguments: String - script name
-
- This command is used to delete a user's Sieve script. Servers MUST
- reply with a NO response if the script does not exist. Such
- responses SHOULD include the NONEXISTENT response code.
-
- The server MUST NOT allow the client to delete an active script, so
- the server MUST reply with a NO response if attempted. Such a
- response SHOULD contain the ACTIVE response code. If a client wishes
- to delete an active script, it should use the SETACTIVE command to
- disable the script first.
-
- Example:
-
- C: Deletescript "foo"
- S: Ok
-
- C: Deletescript "baz"
- S: No (ACTIVE) "You may not delete an active script"
-
-
-
-
-
-
-
-
-
-
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-
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-
-
-2.11. RENAMESCRIPT Command
-
- Arguments: String - Old Script name
- String - New Script name
-
- This command is used to rename a user's Sieve script. Servers MUST
- reply with a NO response if the old script does not exist (in which
- case the NONEXISTENT response code SHOULD be included), or a script
- with the new name already exists (in which case the ALREADYEXISTS
- response code SHOULD be included). Renaming the active script is
- allowed; the renamed script remains active.
-
- Example:
-
- C: Renamescript "foo" "bar"
- S: Ok
-
- C: Renamescript "baz" "bar"
- S: No "bar already exists"
-
- If the server doesn't support the RENAMESCRIPT command, the client
- can emulate it by performing the following steps:
-
- 1. List available scripts with LISTSCRIPTS. If the script with the
- new script name exists, then the client should ask the user
- whether to abort the operation, to replace the script (by issuing
- the DELETESCRIPT <newname> after that), or to choose a different
- name.
-
- 2. Download the old script with GETSCRIPT <oldname>.
-
- 3. Upload the old script with the new name: PUTSCRIPT <newname>.
-
- 4. If the old script was active (as reported by LISTSCRIPTS in step
- 1), then make the new script active: SETACTIVE <newname>.
-
- 5. Delete the old script: DELETESCRIPT <oldname>.
-
- Note that these steps don't describe how to handle various other
- error conditions (for example, NO response containing QUOTA response
- code in step 3). Error handling is left as an exercise for the
- reader.
-
-
-
-
-
-
-
-
-
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-
-
-2.12. CHECKSCRIPT Command
-
- Arguments: String - Script content
-
- The CHECKSCRIPT command is used by the client to verify Sieve script
- validity without storing the script on the server.
-
- The server MUST check the submitted script for syntactic validity,
- which includes checking that all Sieve extensions mentioned in Sieve
- script "require" statement(s) are supported by the Sieve interpreter.
- (Note that if the Sieve interpreter supports the Sieve "ihave"
- extension [I-HAVE], any unrecognized/unsupported extension mentioned
- in the "ihave" test MUST NOT cause the syntactic validation failure.)
- If the script fails this test, the server MUST reply with a NO
- response. The message given with a NO response MUST be human
- readable and SHOULD contain a specific error message giving the line
- number of the first error. Implementors should strive to produce
- helpful error messages similar to those given by programming language
- compilers. Client implementations should note that this may be a
- multiline literal string with more than one error message separated
- by CRLFs. The human-readable message is in the language returned in
- the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
- encoded in UTF-8 [UTF-8].
-
- Examples:
-
- C: CheckScript {31+}
- C: #comment
- C: InvalidSieveCommand
- C:
- S: NO "line 2: Syntax error"
-
- A ManageSieve server supporting this command MUST NOT check if the
- script will put the current user over its quota limit.
-
- An OK response MAY contain the WARNINGS response code. In such a
- case, the human-readable message that follows the OK response SHOULD
- contain a specific warning message (or messages) giving the line
- number(s) in the script that might contain errors not intended by the
- script writer. The human-readable message is in the language
- returned in the latest LANGUAGE capability (or in "i-default"; see
- Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
- response code SHOULD present the message to the user.
-
-
-
-
-
-
-
-
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-
-
-2.13. NOOP Command
-
- Arguments: String - tag to echo back (optional)
-
- The NOOP command does nothing, beyond returning a response to the
- client. It may be used by clients for protocol re-synchronization or
- to reset any inactivity auto-logout timer on the server.
-
- The response to the NOOP command is always OK, followed by the TAG
- response code together with the supplied string. If no string was
- supplied in the NOOP command, the TAG response code MUST NOT be
- included.
-
- Examples:
-
- C: NOOP
- S: OK "NOOP completed"
-
- C: NOOP "STARTTLS-SYNC-42"
- S: OK (TAG {16}
- S: STARTTLS-SYNC-42) "Done"
-
-2.14. Recommended Extensions
-
- The UNAUTHENTICATE extension (advertised as the "UNAUTHENTICATE"
- capability with no parameters) defines a new UNAUTHENTICATE command,
- which allows a client to return the server to non-authenticated
- state. Support for this extension is RECOMMENDED.
-
-2.14.1. UNAUTHENTICATE Command
-
- The UNAUTHENTICATE command returns the server to the
- non-authenticated state. It doesn't affect any previously
- established TLS [TLS] or SASL (Section 2.1) security layer.
-
- The UNAUTHENTICATE command is only valid in authenticated state. If
- issued in a wrong state, the server MUST reject it with a NO
- response.
-
- The UNAUTHENTICATE command has no parameters.
-
- When issued in the authenticated state, the UNAUTHENTICATE command
- MUST NOT fail (i.e., it must never return anything other than OK or
- BYE).
-
-
-
-
-
-
-
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-
-
-3. Sieve URL Scheme
-
- URI scheme name: sieve
-
- Status: permanent
-
- URI scheme syntax: Described using ABNF [ABNF]. Some ABNF
- productions not defined below are from [URI-GEN].
-
- sieveurl = sieveurl-server / sieveurl-list-scripts /
- sieveurl-script
-
- sieveurl-server = "sieve://" authority
-
- sieveurl-list-scripts = "sieve://" authority ["/"]
-
- sieveurl-script = "sieve://" authority "/"
- [owner "/"] scriptname
-
- authority = <defined in [URI-GEN]>
-
- owner = *ochar
- ;; %-encoded version of [SASL] authorization
- ;; identity (script owner) or "userid".
- ;;
- ;; Empty owner is used to reference
- ;; global scripts.
- ;;
- ;; Note that ASCII characters such as " ", ";",
- ;; "&", "=", "/" and "?" must be %-encoded
- ;; as per rule specified in [URI-GEN].
-
- scriptname = 1*ochar
- ;; %-encoded version of UTF-8 representation
- ;; of the script name.
- ;; Note that ASCII characters such as " ", ";",
- ;; "&", "=", "/" and "?" must be %-encoded
- ;; as per rule specified in [URI-GEN].
-
- ochar = unreserved / pct-encoded / sub-delims-sh /
- ":" / "@"
- ;; Same as [URI-GEN] 'pchar',
- ;; but without ";", "&" and "=".
-
- unreserved = <defined in [URI-GEN]>
-
- pct-encoded = <defined in [URI-GEN]>
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
- "*" / "+" / ","
- ;; Same as [URI-GEN] sub-delims,
- ;; but without ";", "&" and "=".
-
- URI scheme semantics:
-
- A Sieve URL identifies a Sieve server or a Sieve script on a Sieve
- server. The latter form is associated with the application/sieve
- MIME type defined in [SIEVE]. There is no MIME type associated
- with the former form of Sieve URI.
-
- The server form is used in the REFERRAL response code (see Section
- 1.3) in order to designate another server where the client should
- perform its operations.
-
- The script form allows to retrieve (GETSCRIPT), update
- (PUTSCRIPT), delete (DELETESCRIPT), or activate (SETACTIVE) the
- named script; however, the most typical action would be to
- retrieve the script. If the script name is empty (omitted), the
- URI requests that the client lists available scripts using the
- LISTSCRIPTS command.
-
- Encoding considerations:
-
- The script name and/or the owner, if present, is in UTF-8. Non--
- US-ASCII UTF-8 octets MUST be percent-encoded as described in
- [URI-GEN]. US-ASCII characters such as " " (space), ";", "&",
- "=", "/" and "?" MUST be %-encoded as described in [URI-GEN].
- Note that "&" and "?" are in this list in order to allow for
- future extensions.
-
- Note that the empty owner (e.g., sieve://example.com//script) is
- different from the missing owner (e.g.,
- sieve://example.com/script) and is reserved for referencing global
- scripts.
-
- The user name (in the "authority" part), if present, is in UTF-8.
- Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
- [URI-GEN].
-
- Applications/protocols that use this URI scheme name:
- ManageSieve [RFC5804] clients and servers. Clients that can store
- user preferences in protocols such as [LDAP] or [ACAP].
-
- Interoperability considerations: None.
-
-
-
-
-
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-
-RFC 5804 ManageSieve July 2010
-
-
- Security considerations:
- The <scriptname> part of a ManageSieve URL might potentially disclose
- some confidential information about the author of the script or,
- depending on a ManageSieve implementation, about configuration of the
- mail system. The latter might be used to prepare for a more complex
- attack on the mail system.
-
- Clients resolving ManageSieve URLs that wish to achieve data
- confidentiality and/or integrity SHOULD use the STARTTLS command (if
- supported by the server) before starting authentication, or use a
- SASL mechanism, such as GSSAPI, that provides a confidentiality
- security layer.
-
- Contact: Alexey Melnikov <alexey.melnikov@isode.com>
-
- Author/Change controller: IESG.
-
- References: This document and RFC 5228 [SIEVE].
-
-4. Formal Syntax
-
- The following syntax specification uses the Augmented Backus-Naur
- Form (BNF) notation as specified in [ABNF]. This uses the ABNF core
- rules as specified in Appendix A of the ABNF specification [ABNF].
- "UTF8-2", "UTF8-3", and "UTF8-4" non-terminal are defined in [UTF-8].
-
- Except as noted otherwise, all alphabetic characters are case-
- insensitive. The use of upper- or lowercase characters to define
- token strings is for editorial clarity only. Implementations MUST
- accept these strings in a case-insensitive fashion.
-
- SAFE-CHAR = %x01-09 / %x0B-0C / %x0E-21 / %x23-5B /
- %x5D-7F
- ;; any TEXT-CHAR except QUOTED-SPECIALS
-
- QUOTED-CHAR = SAFE-UTF8-CHAR / "\" QUOTED-SPECIALS
-
- QUOTED-SPECIALS = DQUOTE / "\"
-
- SAFE-UTF8-CHAR = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4
- ;; <UTF8-2>, <UTF8-3>, and <UTF8-4>
- ;; are defined in [UTF-8].
-
- ATOM-CHAR = "!" / %x23-27 / %x2A-5B / %x5D-7A / %x7C-7E
- ;; Any CHAR except ATOM-SPECIALS
-
- ATOM-SPECIALS = "(" / ")" / "{" / SP / CTL / QUOTED-SPECIALS
-
-
-
-
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-
-
- NZDIGIT = %x31-39
- ;; 1-9
-
- atom = 1*1024ATOM-CHAR
-
- iana-token = atom
- ;; MUST be registered with IANA
-
- auth-type = DQUOTE auth-type-name DQUOTE
-
- auth-type-name = iana-token
- ;; as defined in SASL [SASL]
-
- command = (command-any / command-auth /
- command-nonauth) CRLF
- ;; Modal based on state
-
- command-any = command-capability / command-logout /
- command-noop
- ;; Valid in all states
-
- command-auth = command-getscript / command-setactive /
- command-listscripts / command-deletescript /
- command-putscript / command-checkscript /
- command-havespace /
- command-renamescript /
- command-unauthenticate
- ;; Valid only in Authenticated state
-
- command-nonauth = command-authenticate / command-starttls
- ;; Valid only when in Non-Authenticated
- ;; state
-
- command-authenticate = "AUTHENTICATE" SP auth-type [SP string]
- *(CRLF string)
-
- command-capability = "CAPABILITY"
-
- command-deletescript = "DELETESCRIPT" SP sieve-name
-
- command-getscript = "GETSCRIPT" SP sieve-name
-
- command-havespace = "HAVESPACE" SP sieve-name SP number
-
- command-listscripts = "LISTSCRIPTS"
-
- command-noop = "NOOP" [SP string]
-
-
-
-
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-
-
- command-logout = "LOGOUT"
-
- command-putscript = "PUTSCRIPT" SP sieve-name SP sieve-script
-
- command-checkscript = "CHECKSCRIPT" SP sieve-script
-
- sieve-script = string
-
- command-renamescript = "RENAMESCRIPT" SP old-sieve-name SP
- new-sieve-name
-
- old-sieve-name = sieve-name
-
- new-sieve-name = sieve-name
-
- command-setactive = "SETACTIVE" SP active-sieve-name
-
- command-starttls = "STARTTLS"
-
- command-unauthenticate= "UNAUTHENTICATE"
-
- extend-token = atom
- ;; MUST be defined by a Standards Track or
- ;; IESG-approved experimental protocol
- ;; extension
-
- extension-data = extension-item *(SP extension-item)
-
- extension-item = extend-token / string / number /
- "(" [extension-data] ")"
-
- literal-c2s = "{" number "+}" CRLF *OCTET
- ;; The number represents the number of
- ;; octets.
- ;; This type of literal can only be sent
- ;; from the client to the server.
-
- literal-s2c = "{" number "}" CRLF *OCTET
- ;; Almost identical to literal-c2s,
- ;; but with no '+' character.
- ;; The number represents the number of
- ;; octets.
- ;; This type of literal can only be sent
- ;; from the server to the client.
-
-
-
-
-
-
-
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-
- number = (NZDIGIT *DIGIT) / "0"
- ;; A 32-bit unsigned number
- ;; with no extra leading zeros.
- ;; (0 <= n < 4,294,967,296)
-
- number-str = string
- ;; <number> encoded as a <string>.
-
- quoted = DQUOTE *1024QUOTED-CHAR DQUOTE
- ;; limited to 1024 octets between the <">s
-
- resp-code = "AUTH-TOO-WEAK" / "ENCRYPT-NEEDED" / "QUOTA"
- ["/" ("MAXSCRIPTS" / "MAXSIZE")] /
- resp-code-sasl /
- resp-code-referral /
- "TRANSITION-NEEDED" / "TRYLATER" /
- "ACTIVE" / "NONEXISTENT" /
- "ALREADYEXISTS" / "WARNINGS" /
- "TAG" SP string /
- resp-code-ext
-
- resp-code-referral = "REFERRAL" SP sieveurl
-
- resp-code-sasl = "SASL" SP string
-
- resp-code-name = iana-token
- ;; The response code name is hierarchical,
- ;; separated by '/'.
- ;; The response code name MUST NOT start
- ;; with '/'.
-
- resp-code-ext = resp-code-name [SP extension-data]
- ;; unknown response codes MUST be tolerated
- ;; by the client.
-
- response = response-authenticate /
- response-logout /
- response-getscript /
- response-setactive /
- response-listscripts /
- response-deletescript /
- response-putscript /
- response-checkscript /
- response-capability /
- response-havespace /
- response-starttls /
- response-renamescript /
- response-noop /
-
-
-
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-
-
- response-unauthenticate
-
- response-authenticate = *(string CRLF)
- ((response-ok [response-capability]) /
- response-nobye)
- ;; <response-capability> is REQUIRED if a
- ;; SASL security layer was negotiated and
- ;; MUST be omitted otherwise.
-
- response-capability = *(single-capability) response-oknobye
-
- single-capability = capability-name [SP string] CRLF
-
- capability-name = string
-
- ;; Note that literal-s2c is allowed.
-
- initial-capabilities = DQUOTE "IMPLEMENTATION" DQUOTE SP string /
- DQUOTE "SASL" DQUOTE SP sasl-mechs /
- DQUOTE "SIEVE" DQUOTE SP sieve-extensions /
- DQUOTE "MAXREDIRECTS" DQUOTE SP number-str /
- DQUOTE "NOTIFY" DQUOTE SP notify-mechs /
- DQUOTE "STARTTLS" DQUOTE /
- DQUOTE "LANGUAGE" DQUOTE SP language /
- DQUOTE "VERSION" DQUOTE SP version /
- DQUOTE "OWNER" DQUOTE SP string
- ;; Each capability conforms to
- ;; the syntax for single-capability.
- ;; Also, note that the capability name
- ;; can be returned as either literal-s2c
- ;; or quoted, even though only "quoted"
- ;; string is shown above.
-
- version = ( DQUOTE "1.0" DQUOTE ) / version-ext
-
- version-ext = DQUOTE ver-major "." ver-minor DQUOTE
- ; Future versions specified in updates
- ; to this document. An increment to
- ; the ver-major means a backward-incompatible
- ; change to the protocol, e.g., "3.5" (ver-major "3")
- ; is not backward-compatible with any "2.X" version.
- ; Any version "Z.W" MUST be backward compatible
- ; with any version "Z.Q", where Q < W.
- ; For example, version "2.4" is backward compatible
- ; with version "2.0", "2.1", "2.2", and "2.3".
-
- ver-major = number
-
-
-
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-
- ver-minor = number
-
- sasl-mechs = string
- ; Space-separated list of SASL mechanisms,
- ; each SASL mechanism name complies with rules
- ; specified in [SASL].
- ; Can be empty.
-
- sieve-extensions = string
- ; Space-separated list of supported SIEVE extensions.
- ; Can be empty.
-
- language = string
- ; Contains <Language-Tag> from [RFC5646].
-
-
- notify-mechs = string
- ; Space-separated list of URI schema parts
- ; for supported notification [NOTIFY] methods.
- ; MUST NOT be empty.
-
- response-deletescript = response-oknobye
-
- response-getscript = (sieve-script CRLF response-ok) /
- response-nobye
-
- response-havespace = response-oknobye
-
- response-listscripts = *(sieve-name [SP "ACTIVE"] CRLF)
- response-oknobye
- ;; ACTIVE may only occur with one sieve-name
-
- response-logout = response-oknobye
-
- response-unauthenticate= response-oknobye
- ;; "NO" response can only be returned when
- ;; the command is issued in a wrong state
- ;; or has a wrong number of parameters
-
- response-ok = "OK" [SP "(" resp-code ")"]
- [SP string] CRLF
- ;; The string contains human-readable text
- ;; encoded as UTF-8.
-
- response-nobye = ("NO" / "BYE") [SP "(" resp-code ")"]
- [SP string] CRLF
- ;; The string contains human-readable text
- ;; encoded as UTF-8.
-
-
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-
-
- response-oknobye = response-ok / response-nobye
-
- response-noop = response-ok
-
- response-putscript = response-oknobye
-
- response-checkscript = response-oknobye
-
- response-renamescript = response-oknobye
-
- response-setactive = response-oknobye
-
- response-starttls = (response-ok response-capability) /
- response-nobye
-
- sieve-name = string
- ;; See Section 1.6 for the full list of
- ;; prohibited characters.
- ;; Empty string is not allowed.
-
- active-sieve-name = string
- ;; See Section 1.6 for the full list of
- ;; prohibited characters.
- ;; This is similar to <sieve-name>, but
- ;; empty string is allowed and has a special
- ;; meaning.
-
- string = quoted / literal-c2s / literal-s2c
- ;; literal-c2s is only allowed when sent
- ;; from the client to the server.
- ;; literal-s2c is only allowed when sent
- ;; from the server to the client.
- ;; quoted is allowed in either direction.
-
-5. Security Considerations
-
- The AUTHENTICATE command uses SASL [SASL] to provide authentication
- and authorization services. Integrity and privacy services can be
- provided by [SASL] and/or [TLS]. When a SASL mechanism is used, the
- security considerations for that mechanism apply.
-
- This protocol's transactions are susceptible to passive observers or
- man-in-the-middle attacks that alter the data, unless the optional
- encryption and integrity services of the SASL (via the AUTHENTICATE
- command) and/or [TLS] (via the STARTTLS command) are enabled, or an
- external security mechanism is used for protection. It may be useful
- to allow configuration of both clients and servers to refuse to
- transfer sensitive information in the absence of strong encryption.
-
-
-
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-
- If an implementation supports SASL mechanisms that are vulnerable to
- passive eavesdropping attacks (such as [PLAIN]), then the
- implementation MUST support at least one configuration where these
- SASL mechanisms are not advertised or used without the presence of an
- external security layer such as [TLS].
-
- Some response codes returned on failed AUTHENTICATE command may
- disclose whether or not the username is valid (e.g., TRANSITION-
- NEEDED), so server implementations SHOULD provide the ability to
- disable these features (or make them not conditional on a per-user
- basis) for sites concerned about such disclosure. In the case of
- ENCRYPT-NEEDED, if it is applied to all identities then no extra
- information is disclosed, but if it is applied on a per-user basis it
- can disclose information.
-
- A compromised or malicious server can use the TRANSITION-NEEDED
- response code to force the client that is configured to use a
- mechanism that does not disclose the user's password to the server
- (e.g., Kerberos), to send the bare password to the server. Clients
- SHOULD have the ability to disable the password transition feature,
- or disclose that risk to the user and offer the user an option of how
- to proceed.
-
-6. IANA Considerations
-
- IANA has reserved TCP port number 4190 for use with the ManageSieve
- protocol described in this document.
-
- IANA has registered the "sieve" URI scheme defined in Section 3 of
- this document.
-
- IANA has registered "sieve" in the "GSSAPI/Kerberos/SASL Service
- Names" registry.
-
- IANA has created a new registry for ManageSieve capabilities. The
- registration template for ManageSieve capabilities is specified in
- Section 6.1. ManageSieve protocol capabilities MUST be specified in
- a Standards-Track or IESG-approved Experimental RFC.
-
- IANA has created a new registry for ManageSieve response codes. The
- registration template for ManageSieve response codes is specified in
- Section 6.3. ManageSieve protocol response codes MUST be specified
- in a Standards-Track or IESG-approved Experimental RFC.
-
-
-
-
-
-
-
-
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-
-
-6.1. ManageSieve Capability Registration Template
-
- To: iana@iana.org
- Subject: ManageSieve Capability Registration
-
- Please register the following ManageSieve capability:
-
- Capability name:
- Description:
- Relevant publications:
- Person & email address to contact for further information:
- Author/Change controller:
-
-6.2. Registration of Initial ManageSieve Capabilities
-
- To: iana@iana.org
- Subject: ManageSieve Capability Registration
-
- Please register the following ManageSieve capabilities:
-
- Capability name: IMPLEMENTATION
- Description: Its value contains the name of the server
- implementation and its version.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: SASL
- Description: Its value contains a space-separated list of SASL
- mechanisms supported by the server.
- Relevant publications: this RFC, Sections 1.7 and 2.1.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: SIEVE
- Description: Its value contains a space-separated list of supported
- SIEVE extensions.
- Relevant publications: this RFC, Section 1.7. Also [SIEVE].
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
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-
- Capability name: STARTTLS
- Description: This capability is returned if the server supports TLS
- (STARTTLS command).
- Relevant publications: this RFC, Sections 1.7 and 2.2.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: NOTIFY
- Description: This capability is returned if the server supports the
- 'enotify' [NOTIFY] Sieve extension.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: MAXREDIRECTS
- Description: This capability returns the limit on the number of
- Sieve "redirect" actions a script can perform during a
- single evaluation. The value is a non-negative number
- represented as a ManageSieve string.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: LANGUAGE
- Description: The language (<Language-Tag> from [RFC5646]) currently
- used for human-readable error messages.
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Capability name: OWNER
- Description: Its value contains the UTF-8-encoded name of the
- currently logged-in user ("authorization identity"
- according to RFC 4422).
- Relevant publications: this RFC, Section 1.7.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
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-
-
- Capability name: VERSION
- Description: This capability is returned if the server is compliant
- with RFC 5804; i.e., that it supports RENAMESCRIPT,
- CHECKSCRIPT, and NOOP commands.
- Relevant publications: this RFC, Sections 2.11, 2.12, and 2.13.
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-6.3. ManageSieve Response Code Registration Template
-
- To: iana@iana.org
- Subject: ManageSieve Response Code Registration
-
- Please register the following ManageSieve response code:
-
- Response Code:
- Arguments (use ABNF to specify syntax, or the word NONE if none
- can be specified):
- Purpose:
- Published Specification(s):
- Person & email address to contact for further information:
- Author/Change controller:
-
-6.4. Registration of Initial ManageSieve Response Codes
-
- To: iana@iana.org
- Subject: ManageSieve Response Code Registration
-
- Please register the following ManageSieve response codes:
-
- Response Code: AUTH-TOO-WEAK
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code is returned in the NO response from
- an AUTHENTICATE command. It indicates that site
- security policy forbids the use of the requested
- mechanism for the specified authentication identity.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
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-
-
- Response Code: ENCRYPT-NEEDED
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code is returned in the NO response from
- an AUTHENTICATE command. It indicates that site
- security policy requires the use of a strong
- encryption mechanism for the specified authentication
- identity and mechanism.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: QUOTA
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined quota constraints. If
- this response code is returned in the OK response, it
- can mean that the user is near its quota or that the
- user exceeded its quota, but the server supports soft
- quotas.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: QUOTA/MAXSCRIPTS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined limit on the number of
- Sieve scripts. If this response code is returned in
- the OK response, it can mean that the user is near its
- quota or that the user exceeded its quota, but the
- server supports soft quotas. This response code is a
- more specific version of the QUOTA response code.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
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-
-
- Response Code: QUOTA/MAXSIZE
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: If this response code is returned in the NO/BYE
- response, it means that the command would have placed
- the user above the site-defined maximum script size.
- If this response code is returned in the OK response,
- it can mean that the user is near its quota or that
- the user exceeded its quota, but the server supports
- soft quotas. This response code is a more specific
- version of the QUOTA response code.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: REFERRAL
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): <sieveurl>
- Purpose: This response code may be returned with a BYE result
- from any command, and includes a mandatory parameter
- that indicates what server to access to manage this
- user's Sieve scripts. The server will be specified by
- a Sieve URL (see Section 3). The scriptname portion
- of the URL MUST NOT be specified. The client should
- authenticate to the specified server and use it for
- all further commands in the current session.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: SASL
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): <string>
- Purpose: This response code can occur in the OK response to a
- successful AUTHENTICATE command and includes the
- optional final server response data from the server as
- specified by [SASL].
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
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-
-
- Response Code: TRANSITION-NEEDED
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code occurs in a NO response of an
- AUTHENTICATE command. It indicates that the user name
- is valid, but the entry in the authentication database
- needs to be updated in order to permit authentication
- with the specified mechanism. This is typically done
- by establishing a secure channel using TLS, followed
- by authenticating once using the [PLAIN]
- authentication mechanism. The selected mechanism
- SHOULD then work for authentications in subsequent
- sessions.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: TRYLATER
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed due to a temporary server failure.
- The client MAY continue using local information and
- try the command later. This response code only make
- sense when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: ACTIVE
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because it is not allowed on the
- active script, for example, DELETESCRIPT on the active
- script. This response code only makes sense when
- returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-
-
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-
-
- Response Code: NONEXISTENT
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because the referenced script name
- doesn't exist. This response code only makes sense
- when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: ALREADYEXISTS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: A command failed because the referenced script name
- already exists. This response code only makes sense
- when returned in a NO/BYE response.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: WARNINGS
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): NONE
- Purpose: This response code MAY be returned by the server in
- the OK response (but it might be returned with the NO/
- BYE response as well) and signals the client that even
- though the script is syntactically valid, it might
- contain errors not intended by the script writer.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
- Response Code: TAG
- Arguments (use ABNF to specify syntax, or the word NONE if none can
- be specified): string
- Purpose: This response code name is followed by a string
- specified in the command that caused this response.
- It is typically used for client state synchronization.
- Published Specification(s): [RFC5804]
- Person & email address to contact for further information:
- Alexey Melnikov <alexey.melnikov@isode.com>
- Author/Change controller: IESG.
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 45]
-
-RFC 5804 ManageSieve July 2010
-
-
-7. Internationalization Considerations
-
- The LANGUAGE capability (see Section 1.7) allows a client to discover
- the current language used in all human-readable responses that might
- be returned at the end of any OK/NO/BYE response. Human-readable
- text in OK responses typically doesn't need to be shown to the user,
- unless it is returned in response to a PUTSCRIPT or CHECKSCRIPT
- command that also contains the WARNINGS response code (Section 1.3).
- Human-readable text from NO/BYE responses is intended be shown to the
- user, unless the client can automatically handle failure of the
- command that caused such a response. Clients SHOULD use response
- codes (Section 1.3) for automatic error handling. Response codes MAY
- also be used by the client to present error messages in a language
- understood by the user, for example, if the LANGUAGE capability
- doesn't return a language understood by the user.
-
- Note that the human-readable text from OK (WARNINGS) or NO/BYE
- responses for PUTSCRIPT/CHECKSCRIPT commands is intended for advanced
- users that understand Sieve language. Such advanced users are often
- sophisticated enough to be able to handle whatever language the
- server is using, even if it is not their preferred language, and will
- want to see error/warning text no matter what language the server
- puts it in.
-
- A client that generates Sieve script automatically, for example, if
- the script is generated without user intervention or from a UI that
- presents an abstract list of conditions and corresponding actions,
- SHOULD NOT present warning/error messages to the user, because the
- user might not even be aware that the client is using Sieve
- underneath. However, if the client has a debugging mode, such
- warnings/errors SHOULD be available in the debugging mode.
-
- Note that this document doesn't provide a way to modify the currently
- used language. It is expected that a future extension will address
- that.
-
-8. Acknowledgements
-
- Thanks to Simon Josefsson, Larry Greenfield, Allen Johnson, Chris
- Newman, Lyndon Nerenberg, Tim Showalter, Sarah Robeson, Walter Wong,
- Barry Leiba, Arnt Gulbrandsen, Stephan Bosch, Ken Murchison, Phil
- Pennock, Ned Freed, Jeffrey Hutzelman, Mark E. Mallett, Dilyan
- Palauzov, Dave Cridland, Aaron Stone, Robert Burrell Donkin, Patrick
- Ben Koetter, Bjoern Hoehrmann, Martin Duerst, Pasi Eronen, Magnus
- Westerlund, Tim Polk, and Julien Coloos for help with this document.
- Special thank you to Phil Pennock for providing text for the NOOP
- command, as well as finding various bugs in the document.
-
-
-
-
-Melnikov & Martin Standards Track [Page 46]
-
-RFC 5804 ManageSieve July 2010
-
-
-9. References
-
-9.1. Normative References
-
- [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", STD 68, RFC 5234, January 2008.
-
- [ACAP] Newman, C. and J. Myers, "ACAP -- Application
- Configuration Access Protocol", RFC 2244, November
- 1997.
-
- [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
- Encodings", RFC 4648, October 2006.
-
- [DNS-SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR
- for specifying the location of services (DNS SRV)",
- RFC 2782, February 2000.
-
- [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [NET-UNICODE] Klensin, J. and M. Padlipsky, "Unicode Format for
- Network Interchange", RFC 5198, March 2008.
-
- [NOTIFY] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
- "Sieve Email Filtering: Extension for Notifications",
- RFC 5435, January 2009.
-
- [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
- Languages", BCP 18, RFC 2277, January 1998.
-
- [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version
- 6 (IPv6) Specification", RFC 2460, December 1998.
-
- [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
- "Internationalizing Domain Names in Applications
- (IDNA)", RFC 3490, March 2003.
-
- [RFC4519] Sciberras, A., "Lightweight Directory Access Protocol
- (LDAP): Schema for User Applications", RFC 4519, June
- 2006.
-
- [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
- Languages", BCP 47, RFC 5646, September 2009.
-
- [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
- September 1981.
-
-
-
-
-Melnikov & Martin Standards Track [Page 47]
-
-RFC 5804 ManageSieve July 2010
-
-
- [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication
- and Security Layer (SASL)", RFC 4422, June 2006.
-
- [SASLprep] Zeilenga, K., "SASLprep: Stringprep Profile for User
- Names and Passwords", RFC 4013, February 2005.
-
- [SCRAM] Menon-Sen, A., Melnikov, A., Newman, C., and N.
- Williams, "Salted Challenge Response Authentication
- Mechanism (SCRAM) SASL and GSS-API Mechanisms", RFC
- 5802, July 2010.
-
- [SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email
- Filtering Language", RFC 5228, January 2008.
-
- [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
- Internationalized Strings ("stringprep")", RFC 3454,
- December 2002.
-
- [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
- Security (TLS) Protocol Version 1.2", RFC 5246, August
- 2008.
-
- [URI-GEN] Berners-Lee, T., Fielding, R., and L. Masinter,
- "Uniform Resource Identifier (URI): Generic Syntax",
- STD 66, RFC 3986, January 2005.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
- 10646", STD 63, RFC 3629, November 2003.
-
- [X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
- Housley, R., and W. Polk, "Internet X.509 Public Key
- Infrastructure Certificate and Certificate Revocation
- List (CRL) Profile", RFC 5280, May 2008.
-
- [X509-SRV] Santesson, S., "Internet X.509 Public Key
- Infrastructure Subject Alternative Name for Expression
- of Service Name", RFC 4985, August 2007.
-
-9.2. Informative References
-
- [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication
- as a SASL Mechanism", RFC 2831, May 2000.
-
- [GSSAPI] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
- Authentication and Security Layer (SASL) Mechanism",
- RFC 4752, November 2006.
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 48]
-
-RFC 5804 ManageSieve July 2010
-
-
- [I-HAVE] Freed, N., "Sieve Email Filtering: Ihave Extension",
- RFC 5463, March 2009.
-
- [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
- VERSION 4rev1", RFC 3501, March 2003.
-
- [LDAP] Zeilenga, K., "Lightweight Directory Access Protocol
- (LDAP): Technical Specification Road Map", RFC 4510,
- June 2006.
-
- [PLAIN] Zeilenga, K., "The PLAIN Simple Authentication and
- Security Layer (SASL) Mechanism", RFC 4616, August
- 2006.
-
-Authors' Addresses
-
- Alexey Melnikov (editor)
- Isode Limited
- 5 Castle Business Village
- 36 Station Road
- Hampton, Middlesex TW12 2BX
- UK
-
- EMail: Alexey.Melnikov@isode.com
-
-
- Tim Martin
- BeThereBeSquare, Inc.
- 672 Haight st.
- San Francisco, CA 94117
- USA
-
- Phone: +1 510 260-4175
- EMail: timmartin@alumni.cmu.edu
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Melnikov & Martin Standards Track [Page 49]
-
diff --git a/rfc/rfc1341.txt b/rfc/rfc1341.txt
@@ -0,0 +1,5265 @@
+
+
+
+
+
+
+ Network Working Group N. Borenstein, Bellcore
+ Request for Comments: 1341 N. Freed, Innosoft
+ June 1992
+
+
+
+ MIME (Multipurpose Internet Mail Extensions):
+
+
+ Mechanisms for Specifying and Describing
+ the Format of Internet Message Bodies
+
+
+ Status of this Memo
+
+ This RFC specifies an IAB standards track protocol for the
+ Internet community, and requests discussion and suggestions
+ for improvements. Please refer to the current edition of
+ the "IAB Official Protocol Standards" for the
+ standardization state and status of this protocol.
+ Distribution of this memo is unlimited.
+
+ Abstract
+
+ RFC 822 defines a message representation protocol which
+ specifies considerable detail about message headers, but
+ which leaves the message content, or message body, as flat
+ ASCII text. This document redefines the format of message
+ bodies to allow multi-part textual and non-textual message
+ bodies to be represented and exchanged without loss of
+ information. This is based on earlier work documented in
+ RFC 934 and RFC 1049, but extends and revises that work.
+ Because RFC 822 said so little about message bodies, this
+ document is largely orthogonal to (rather than a revision
+ of) RFC 822.
+
+ In particular, this document is designed to provide
+ facilities to include multiple objects in a single message,
+ to represent body text in character sets other than US-
+ ASCII, to represent formatted multi-font text messages, to
+ represent non-textual material such as images and audio
+ fragments, and generally to facilitate later extensions
+ defining new types of Internet mail for use by cooperating
+ mail agents.
+
+ This document does NOT extend Internet mail header fields to
+ permit anything other than US-ASCII text data. It is
+ recognized that such extensions are necessary, and they are
+ the subject of a companion document [RFC -1342].
+
+ A table of contents appears at the end of this document.
+
+
+
+
+
+
+ Borenstein & Freed [Page i]
+
+
+
+
+
+
+
+ 1 Introduction
+
+ Since its publication in 1982, RFC 822 [RFC-822] has defined
+ the standard format of textual mail messages on the
+ Internet. Its success has been such that the RFC 822 format
+ has been adopted, wholly or partially, well beyond the
+ confines of the Internet and the Internet SMTP transport
+ defined by RFC 821 [RFC-821]. As the format has seen wider
+ use, a number of limitations have proven increasingly
+ restrictive for the user community.
+
+ RFC 822 was intended to specify a format for text messages.
+ As such, non-text messages, such as multimedia messages that
+ might include audio or images, are simply not mentioned.
+ Even in the case of text, however, RFC 822 is inadequate for
+ the needs of mail users whose languages require the use of
+ character sets richer than US ASCII [US-ASCII]. Since RFC
+ 822 does not specify mechanisms for mail containing audio,
+ video, Asian language text, or even text in most European
+ languages, additional specifications are needed
+
+ One of the notable limitations of RFC 821/822 based mail
+ systems is the fact that they limit the contents of
+ electronic mail messages to relatively short lines of
+ seven-bit ASCII. This forces users to convert any non-
+ textual data that they may wish to send into seven-bit bytes
+ representable as printable ASCII characters before invoking
+ a local mail UA (User Agent, a program with which human
+ users send and receive mail). Examples of such encodings
+ currently used in the Internet include pure hexadecimal,
+ uuencode, the 3-in-4 base 64 scheme specified in RFC 1113,
+ the Andrew Toolkit Representation [ATK], and many others.
+
+ The limitations of RFC 822 mail become even more apparent as
+ gateways are designed to allow for the exchange of mail
+ messages between RFC 822 hosts and X.400 hosts. X.400 [X400]
+ specifies mechanisms for the inclusion of non-textual body
+ parts within electronic mail messages. The current
+ standards for the mapping of X.400 messages to RFC 822
+ messages specify that either X.400 non-textual body parts
+ should be converted to (not encoded in) an ASCII format, or
+ that they should be discarded, notifying the RFC 822 user
+ that discarding has occurred. This is clearly undesirable,
+ as information that a user may wish to receive is lost.
+ Even though a user's UA may not have the capability of
+ dealing with the non-textual body part, the user might have
+ some mechanism external to the UA that can extract useful
+ information from the body part. Moreover, it does not allow
+ for the fact that the message may eventually be gatewayed
+ back into an X.400 message handling system (i.e., the X.400
+ message is "tunneled" through Internet mail), where the
+ non-textual information would definitely become useful
+ again.
+
+
+
+
+ Borenstein & Freed [Page 1]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ This document describes several mechanisms that combine to
+ solve most of these problems without introducing any serious
+ incompatibilities with the existing world of RFC 822 mail.
+ In particular, it describes:
+
+ 1. A MIME-Version header field, which uses a version number
+ to declare a message to be conformant with this
+ specification and allows mail processing agents to
+ distinguish between such messages and those generated
+ by older or non-conformant software, which is presumed
+ to lack such a field.
+
+ 2. A Content-Type header field, generalized from RFC 1049
+ [RFC-1049], which can be used to specify the type and
+ subtype of data in the body of a message and to fully
+ specify the native representation (encoding) of such
+ data.
+
+ 2.a. A "text" Content-Type value, which can be used to
+ represent textual information in a number of
+ character sets and formatted text description
+ languages in a standardized manner.
+
+ 2.b. A "multipart" Content-Type value, which can be
+ used to combine several body parts, possibly of
+ differing types of data, into a single message.
+
+ 2.c. An "application" Content-Type value, which can be
+ used to transmit application data or binary data,
+ and hence, among other uses, to implement an
+ electronic mail file transfer service.
+
+ 2.d. A "message" Content-Type value, for encapsulating
+ a mail message.
+
+ 2.e An "image" Content-Type value, for transmitting
+ still image (picture) data.
+
+ 2.f. An "audio" Content-Type value, for transmitting
+ audio or voice data.
+
+ 2.g. A "video" Content-Type value, for transmitting
+ video or moving image data, possibly with audio as
+ part of the composite video data format.
+
+ 3. A Content-Transfer-Encoding header field, which can be
+ used to specify an auxiliary encoding that was applied
+ to the data in order to allow it to pass through mail
+ transport mechanisms which may have data or character
+ set limitations.
+
+ 4. Two optional header fields that can be used to further
+ describe the data in a message body, the Content-ID and
+ Content-Description header fields.
+
+
+
+ Borenstein & Freed [Page 2]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ MIME has been carefully designed as an extensible mechanism,
+ and it is expected that the set of content-type/subtype
+ pairs and their associated parameters will grow
+ significantly with time. Several other MIME fields, notably
+ including character set names, are likely to have new values
+ defined over time. In order to ensure that the set of such
+ values is developed in an orderly, well-specified, and
+ public manner, MIME defines a registration process which
+ uses the Internet Assigned Numbers Authority (IANA) as a
+ central registry for such values. Appendix F provides
+ details about how IANA registration is accomplished.
+
+ Finally, to specify and promote interoperability, Appendix A
+ of this document provides a basic applicability statement
+ for a subset of the above mechanisms that defines a minimal
+ level of "conformance" with this document.
+
+ HISTORICAL NOTE: Several of the mechanisms described in
+ this document may seem somewhat strange or even baroque at
+ first reading. It is important to note that compatibility
+ with existing standards AND robustness across existing
+ practice were two of the highest priorities of the working
+ group that developed this document. In particular,
+ compatibility was always favored over elegance.
+
+ 2 Notations, Conventions, and Generic BNF Grammar
+
+ This document is being published in two versions, one as
+ plain ASCII text and one as PostScript. The latter is
+ recommended, though the textual contents are identical. An
+ Andrew-format copy of this document is also available from
+ the first author (Borenstein).
+
+ Although the mechanisms specified in this document are all
+ described in prose, most are also described formally in the
+ modified BNF notation of RFC 822. Implementors will need to
+ be familiar with this notation in order to understand this
+ specification, and are referred to RFC 822 for a complete
+ explanation of the modified BNF notation.
+
+ Some of the modified BNF in this document makes reference to
+ syntactic entities that are defined in RFC 822 and not in
+ this document. A complete formal grammar, then, is obtained
+ by combining the collected grammar appendix of this document
+ with that of RFC 822.
+
+ The term CRLF, in this document, refers to the sequence of
+ the two ASCII characters CR (13) and LF (10) which, taken
+ together, in this order, denote a line break in RFC 822
+ mail.
+
+ The term "character set", wherever it is used in this
+ document, refers to a coded character set, in the sense of
+ ISO character set standardization work, and must not be
+
+
+
+ Borenstein & Freed [Page 3]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ misinterpreted as meaning "a set of characters."
+
+ The term "message", when not further qualified, means either
+ the (complete or "top-level") message being transferred on a
+ network, or a message encapsulated in a body of type
+ "message".
+
+ The term "body part", in this document, means one of the
+ parts of the body of a multipart entity. A body part has a
+ header and a body, so it makes sense to speak about the body
+ of a body part.
+
+ The term "entity", in this document, means either a message
+ or a body part. All kinds of entities share the property
+ that they have a header and a body.
+
+ The term "body", when not further qualified, means the body
+ of an entity, that is the body of either a message or of a
+ body part.
+
+ Note : the previous four definitions are clearly circular.
+ This is unavoidable, since the overal structure of a MIME
+ message is indeed recursive.
+
+ In this document, all numeric and octet values are given in
+ decimal notation.
+
+ It must be noted that Content-Type values, subtypes, and
+ parameter names as defined in this document are case-
+ insensitive. However, parameter values are case-sensitive
+ unless otherwise specified for the specific parameter.
+
+ FORMATTING NOTE: This document has been carefully formatted
+ for ease of reading. The PostScript version of this
+ document, in particular, places notes like this one, which
+ may be skipped by the reader, in a smaller, italicized,
+ font, and indents it as well. In the text version, only the
+ indentation is preserved, so if you are reading the text
+ version of this you might consider using the PostScript
+ version instead. However, all such notes will be indented
+ and preceded by "NOTE:" or some similar introduction, even
+ in the text version.
+
+ The primary purpose of these non-essential notes is to
+ convey information about the rationale of this document, or
+ to place this document in the proper historical or
+ evolutionary context. Such information may be skipped by
+ those who are focused entirely on building a compliant
+ implementation, but may be of use to those who wish to
+ understand why this document is written as it is.
+
+ For ease of recognition, all BNF definitions have been
+ placed in a fixed-width font in the PostScript version of
+ this document.
+
+
+
+ Borenstein & Freed [Page 4]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 3 The MIME-Version Header Field
+
+ Since RFC 822 was published in 1982, there has really been
+ only one format standard for Internet messages, and there
+ has been little perceived need to declare the format
+ standard in use. This document is an independent document
+ that complements RFC 822. Although the extensions in this
+ document have been defined in such a way as to be compatible
+ with RFC 822, there are still circumstances in which it
+ might be desirable for a mail-processing agent to know
+ whether a message was composed with the new standard in
+ mind.
+
+ Therefore, this document defines a new header field, "MIME-
+ Version", which is to be used to declare the version of the
+ Internet message body format standard in use.
+
+ Messages composed in accordance with this document MUST
+ include such a header field, with the following verbatim
+ text:
+
+ MIME-Version: 1.0
+
+ The presence of this header field is an assertion that the
+ message has been composed in compliance with this document.
+
+ Since it is possible that a future document might extend the
+ message format standard again, a formal BNF is given for the
+ content of the MIME-Version field:
+
+ MIME-Version := text
+
+ Thus, future format specifiers, which might replace or
+ extend "1.0", are (minimally) constrained by the definition
+ of "text", which appears in RFC 822.
+
+ Note that the MIME-Version header field is required at the
+ top level of a message. It is not required for each body
+ part of a multipart entity. It is required for the embedded
+ headers of a body of type "message" if and only if the
+ embedded message is itself claimed to be MIME-compliant.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 5]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 4 The Content-Type Header Field
+
+ The purpose of the Content-Type field is to describe the
+ data contained in the body fully enough that the receiving
+ user agent can pick an appropriate agent or mechanism to
+ present the data to the user, or otherwise deal with the
+ data in an appropriate manner.
+
+ HISTORICAL NOTE: The Content-Type header field was first
+ defined in RFC 1049. RFC 1049 Content-types used a simpler
+ and less powerful syntax, but one that is largely compatible
+ with the mechanism given here.
+
+ The Content-Type header field is used to specify the nature
+ of the data in the body of an entity, by giving type and
+ subtype identifiers, and by providing auxiliary information
+ that may be required for certain types. After the type and
+ subtype names, the remainder of the header field is simply a
+ set of parameters, specified in an attribute/value notation.
+ The set of meaningful parameters differs for the different
+ types. The ordering of parameters is not significant.
+ Among the defined parameters is a "charset" parameter by
+ which the character set used in the body may be declared.
+ Comments are allowed in accordance with RFC 822 rules for
+ structured header fields.
+
+ In general, the top-level Content-Type is used to declare
+ the general type of data, while the subtype specifies a
+ specific format for that type of data. Thus, a Content-Type
+ of "image/xyz" is enough to tell a user agent that the data
+ is an image, even if the user agent has no knowledge of the
+ specific image format "xyz". Such information can be used,
+ for example, to decide whether or not to show a user the raw
+ data from an unrecognized subtype -- such an action might be
+ reasonable for unrecognized subtypes of text, but not for
+ unrecognized subtypes of image or audio. For this reason,
+ registered subtypes of audio, image, text, and video, should
+ not contain embedded information that is really of a
+ different type. Such compound types should be represented
+ using the "multipart" or "application" types.
+
+ Parameters are modifiers of the content-subtype, and do not
+ fundamentally affect the requirements of the host system.
+ Although most parameters make sense only with certain
+ content-types, others are "global" in the sense that they
+ might apply to any subtype. For example, the "boundary"
+ parameter makes sense only for the "multipart" content-type,
+ but the "charset" parameter might make sense with several
+ content-types.
+
+ An initial set of seven Content-Types is defined by this
+ document. This set of top-level names is intended to be
+ substantially complete. It is expected that additions to
+ the larger set of supported types can generally be
+
+
+
+ Borenstein & Freed [Page 6]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ accomplished by the creation of new subtypes of these
+ initial types. In the future, more top-level types may be
+ defined only by an extension to this standard. If another
+ primary type is to be used for any reason, it must be given
+ a name starting with "X-" to indicate its non-standard
+ status and to avoid a potential conflict with a future
+ official name.
+
+ In the Extended BNF notation of RFC 822, a Content-Type
+ header field value is defined as follows:
+
+ Content-Type := type "/" subtype *[";" parameter]
+
+ type := "application" / "audio"
+ / "image" / "message"
+ / "multipart" / "text"
+ / "video" / x-token
+
+ x-token := <The two characters "X-" followed, with no
+ intervening white space, by any token>
+
+ subtype := token
+
+ parameter := attribute "=" value
+
+ attribute := token
+
+ value := token / quoted-string
+
+ token := 1*<any CHAR except SPACE, CTLs, or tspecials>
+
+ tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in
+ / "," / ";" / ":" / "\" / <"> ; quoted-string,
+ / "/" / "[" / "]" / "?" / "." ; to use within
+ / "=" ; parameter values
+
+ Note that the definition of "tspecials" is the same as the
+ RFC 822 definition of "specials" with the addition of the
+ three characters "/", "?", and "=".
+
+ Note also that a subtype specification is MANDATORY. There
+ are no default subtypes.
+
+ The type, subtype, and parameter names are not case
+ sensitive. For example, TEXT, Text, and TeXt are all
+ equivalent. Parameter values are normally case sensitive,
+ but certain parameters are interpreted to be case-
+ insensitive, depending on the intended use. (For example,
+ multipart boundaries are case-sensitive, but the "access-
+ type" for message/External-body is not case-sensitive.)
+
+ Beyond this syntax, the only constraint on the definition of
+ subtype names is the desire that their uses must not
+ conflict. That is, it would be undesirable to have two
+
+
+
+ Borenstein & Freed [Page 7]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ different communities using "Content-Type:
+ application/foobar" to mean two different things. The
+ process of defining new content-subtypes, then, is not
+ intended to be a mechanism for imposing restrictions, but
+ simply a mechanism for publicizing the usages. There are,
+ therefore, two acceptable mechanisms for defining new
+ Content-Type subtypes:
+
+ 1. Private values (starting with "X-") may be
+ defined bilaterally between two cooperating
+ agents without outside registration or
+ standardization.
+
+ 2. New standard values must be documented,
+ registered with, and approved by IANA, as
+ described in Appendix F. Where intended for
+ public use, the formats they refer to must
+ also be defined by a published specification,
+ and possibly offered for standardization.
+
+ The seven standard initial predefined Content-Types are
+ detailed in the bulk of this document. They are:
+
+ text -- textual information. The primary subtype,
+ "plain", indicates plain (unformatted) text. No
+ special software is required to get the full
+ meaning of the text, aside from support for the
+ indicated character set. Subtypes are to be used
+ for enriched text in forms where application
+ software may enhance the appearance of the text,
+ but such software must not be required in order to
+ get the general idea of the content. Possible
+ subtypes thus include any readable word processor
+ format. A very simple and portable subtype,
+ richtext, is defined in this document.
+ multipart -- data consisting of multiple parts of
+ independent data types. Four initial subtypes
+ are defined, including the primary "mixed"
+ subtype, "alternative" for representing the same
+ data in multiple formats, "parallel" for parts
+ intended to be viewed simultaneously, and "digest"
+ for multipart entities in which each part is of
+ type "message".
+ message -- an encapsulated message. A body of
+ Content-Type "message" is itself a fully formatted
+ RFC 822 conformant message which may contain its
+ own different Content-Type header field. The
+ primary subtype is "rfc822". The "partial"
+ subtype is defined for partial messages, to permit
+ the fragmented transmission of bodies that are
+ thought to be too large to be passed through mail
+ transport facilities. Another subtype,
+ "External-body", is defined for specifying large
+ bodies by reference to an external data source.
+
+
+
+ Borenstein & Freed [Page 8]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ image -- image data. Image requires a display device
+ (such as a graphical display, a printer, or a FAX
+ machine) to view the information. Initial
+ subtypes are defined for two widely-used image
+ formats, jpeg and gif.
+ audio -- audio data, with initial subtype "basic".
+ Audio requires an audio output device (such as a
+ speaker or a telephone) to "display" the contents.
+ video -- video data. Video requires the capability to
+ display moving images, typically including
+ specialized hardware and software. The initial
+ subtype is "mpeg".
+ application -- some other kind of data, typically
+ either uninterpreted binary data or information to
+ be processed by a mail-based application. The
+ primary subtype, "octet-stream", is to be used in
+ the case of uninterpreted binary data, in which
+ case the simplest recommended action is to offer
+ to write the information into a file for the user.
+ Two additional subtypes, "ODA" and "PostScript",
+ are defined for transporting ODA and PostScript
+ documents in bodies. Other expected uses for
+ "application" include spreadsheets, data for
+ mail-based scheduling systems, and languages for
+ "active" (computational) email. (Note that active
+ email entails several securityconsiderations,
+ which are discussed later in this memo,
+ particularly in the context of
+ application/PostScript.)
+
+ Default RFC 822 messages are typed by this protocol as plain
+ text in the US-ASCII character set, which can be explicitly
+ specified as "Content-type: text/plain; charset=us-ascii".
+ If no Content-Type is specified, either by error or by an
+ older user agent, this default is assumed. In the presence
+ of a MIME-Version header field, a receiving User Agent can
+ also assume that plain US-ASCII text was the sender's
+ intent. In the absence of a MIME-Version specification,
+ plain US-ASCII text must still be assumed, but the sender's
+ intent might have been otherwise.
+
+ RATIONALE: In the absence of any Content-Type header field
+ or MIME-Version header field, it is impossible to be certain
+ that a message is actually text in the US-ASCII character
+ set, since it might well be a message that, using the
+ conventions that predate this document, includes text in
+ another character set or non-textual data in a manner that
+ cannot be automatically recognized (e.g., a uuencoded
+ compressed UNIX tar file). Although there is no fully
+ acceptable alternative to treating such untyped messages as
+ "text/plain; charset=us-ascii", implementors should remain
+ aware that if a message lacks both the MIME-Version and the
+ Content-Type header fields, it may in practice contain
+ almost anything.
+
+
+
+ Borenstein & Freed [Page 9]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ It should be noted that the list of Content-Type values
+ given here may be augmented in time, via the mechanisms
+ described above, and that the set of subtypes is expected to
+ grow substantially.
+
+ When a mail reader encounters mail with an unknown Content-
+ type value, it should generally treat it as equivalent to
+ "application/octet-stream", as described later in this
+ document.
+
+ 5 The Content-Transfer-Encoding Header Field
+
+ Many Content-Types which could usefully be transported via
+ email are represented, in their "natural" format, as 8-bit
+ character or binary data. Such data cannot be transmitted
+ over some transport protocols. For example, RFC 821
+ restricts mail messages to 7-bit US-ASCII data with 1000
+ character lines.
+
+ It is necessary, therefore, to define a standard mechanism
+ for re-encoding such data into a 7-bit short-line format.
+ This document specifies that such encodings will be
+ indicated by a new "Content-Transfer-Encoding" header field.
+ The Content-Transfer-Encoding field is used to indicate the
+ type of transformation that has been used in order to
+ represent the body in an acceptable manner for transport.
+
+ Unlike Content-Types, a proliferation of Content-Transfer-
+ Encoding values is undesirable and unnecessary. However,
+ establishing only a single Content-Transfer-Encoding
+ mechanism does not seem possible. There is a tradeoff
+ between the desire for a compact and efficient encoding of
+ largely-binary data and the desire for a readable encoding
+ of data that is mostly, but not entirely, 7-bit data. For
+ this reason, at least two encoding mechanisms are necessary:
+ a "readable" encoding and a "dense" encoding.
+
+ The Content-Transfer-Encoding field is designed to specify
+ an invertible mapping between the "native" representation of
+ a type of data and a representation that can be readily
+ exchanged using 7 bit mail transport protocols, such as
+ those defined by RFC 821 (SMTP). This field has not been
+ defined by any previous standard. The field's value is a
+ single token specifying the type of encoding, as enumerated
+ below. Formally:
+
+ Content-Transfer-Encoding := "BASE64" / "QUOTED-PRINTABLE" /
+ "8BIT" / "7BIT" /
+ "BINARY" / x-token
+
+ These values are not case sensitive. That is, Base64 and
+ BASE64 and bAsE64 are all equivalent. An encoding type of
+ 7BIT requires that the body is already in a seven-bit mail-
+ ready representation. This is the default value -- that is,
+
+
+
+ Borenstein & Freed [Page 10]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ "Content-Transfer-Encoding: 7BIT" is assumed if the
+ Content-Transfer-Encoding header field is not present.
+
+ The values "8bit", "7bit", and "binary" all imply that NO
+ encoding has been performed. However, they are potentially
+ useful as indications of the kind of data contained in the
+ object, and therefore of the kind of encoding that might
+ need to be performed for transmission in a given transport
+ system. "7bit" means that the data is all represented as
+ short lines of US-ASCII data. "8bit" means that the lines
+ are short, but there may be non-ASCII characters (octets
+ with the high-order bit set). "Binary" means that not only
+ may non-ASCII characters be present, but also that the lines
+ are not necessarily short enough for SMTP transport.
+
+ The difference between "8bit" (or any other conceivable
+ bit-width token) and the "binary" token is that "binary"
+ does not require adherence to any limits on line length or
+ to the SMTP CRLF semantics, while the bit-width tokens do
+ require such adherence. If the body contains data in any
+ bit-width other than 7-bit, the appropriate bit-width
+ Content-Transfer-Encoding token must be used (e.g., "8bit"
+ for unencoded 8 bit wide data). If the body contains binary
+ data, the "binary" Content-Transfer-Encoding token must be
+ used.
+
+ NOTE: The distinction between the Content-Transfer-Encoding
+ values of "binary," "8bit," etc. may seem unimportant, in
+ that all of them really mean "none" -- that is, there has
+ been no encoding of the data for transport. However, clear
+ labeling will be of enormous value to gateways between
+ future mail transport systems with differing capabilities in
+ transporting data that do not meet the restrictions of RFC
+ 821 transport.
+
+ As of the publication of this document, there are no
+ standardized Internet transports for which it is legitimate
+ to include unencoded 8-bit or binary data in mail bodies.
+ Thus there are no circumstances in which the "8bit" or
+ "binary" Content-Transfer-Encoding is actually legal on the
+ Internet. However, in the event that 8-bit or binary mail
+ transport becomes a reality in Internet mail, or when this
+ document is used in conjunction with any other 8-bit or
+ binary-capable transport mechanism, 8-bit or binary bodies
+ should be labeled as such using this mechanism.
+
+ NOTE: The five values defined for the Content-Transfer-
+ Encoding field imply nothing about the Content-Type other
+ than the algorithm by which it was encoded or the transport
+ system requirements if unencoded.
+
+ Implementors may, if necessary, define new Content-
+ Transfer-Encoding values, but must use an x-token, which is
+ a name prefixed by "X-" to indicate its non-standard status,
+
+
+
+ Borenstein & Freed [Page 11]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ e.g., "Content-Transfer-Encoding: x-my-new-encoding".
+ However, unlike Content-Types and subtypes, the creation of
+ new Content-Transfer-Encoding values is explicitly and
+ strongly discouraged, as it seems likely to hinder
+ interoperability with little potential benefit. Their use
+ is allowed only as the result of an agreement between
+ cooperating user agents.
+
+ If a Content-Transfer-Encoding header field appears as part
+ of a message header, it applies to the entire body of that
+ message. If a Content-Transfer-Encoding header field
+ appears as part of a body part's headers, it applies only to
+ the body of that body part. If an entity is of type
+ "multipart" or "message", the Content-Transfer-Encoding is
+ not permitted to have any value other than a bit width
+ (e.g., "7bit", "8bit", etc.) or "binary".
+
+ It should be noted that email is character-oriented, so that
+ the mechanisms described here are mechanisms for encoding
+ arbitrary byte streams, not bit streams. If a bit stream is
+ to be encoded via one of these mechanisms, it must first be
+ converted to an 8-bit byte stream using the network standard
+ bit order ("big-endian"), in which the earlier bits in a
+ stream become the higher-order bits in a byte. A bit stream
+ not ending at an 8-bit boundary must be padded with zeroes.
+ This document provides a mechanism for noting the addition
+ of such padding in the case of the application Content-Type,
+ which has a "padding" parameter.
+
+ The encoding mechanisms defined here explicitly encode all
+ data in ASCII. Thus, for example, suppose an entity has
+ header fields such as:
+
+ Content-Type: text/plain; charset=ISO-8859-1
+ Content-transfer-encoding: base64
+
+ This should be interpreted to mean that the body is a base64
+ ASCII encoding of data that was originally in ISO-8859-1,
+ and will be in that character set again after decoding.
+
+ The following sections will define the two standard encoding
+ mechanisms. The definition of new content-transfer-
+ encodings is explicitly discouraged and should only occur
+ when absolutely necessary. All content-transfer-encoding
+ namespace except that beginning with "X-" is explicitly
+ reserved to the IANA for future use. Private agreements
+ about content-transfer-encodings are also explicitly
+ discouraged.
+
+ Certain Content-Transfer-Encoding values may only be used on
+ certain Content-Types. In particular, it is expressly
+ forbidden to use any encodings other than "7bit", "8bit", or
+ "binary" with any Content-Type that recursively includes
+ other Content-Type fields, notably the "multipart" and
+
+
+
+ Borenstein & Freed [Page 12]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ "message" Content-Types. All encodings that are desired for
+ bodies of type multipart or message must be done at the
+ innermost level, by encoding the actual body that needs to
+ be encoded.
+
+ NOTE ON ENCODING RESTRICTIONS: Though the prohibition
+ against using content-transfer-encodings on data of type
+ multipart or message may seem overly restrictive, it is
+ necessary to prevent nested encodings, in which data are
+ passed through an encoding algorithm multiple times, and
+ must be decoded multiple times in order to be properly
+ viewed. Nested encodings add considerable complexity to
+ user agents: aside from the obvious efficiency problems
+ with such multiple encodings, they can obscure the basic
+ structure of a message. In particular, they can imply that
+ several decoding operations are necessary simply to find out
+ what types of objects a message contains. Banning nested
+ encodings may complicate the job of certain mail gateways,
+ but this seems less of a problem than the effect of nested
+ encodings on user agents.
+
+ NOTE ON THE RELATIONSHIP BETWEEN CONTENT-TYPE AND CONTENT-
+ TRANSFER-ENCODING: It may seem that the Content-Transfer-
+ Encoding could be inferred from the characteristics of the
+ Content-Type that is to be encoded, or, at the very least,
+ that certain Content-Transfer-Encodings could be mandated
+ for use with specific Content-Types. There are several
+ reasons why this is not the case. First, given the varying
+ types of transports used for mail, some encodings may be
+ appropriate for some Content-Type/transport combinations and
+ not for others. (For example, in an 8-bit transport, no
+ encoding would be required for text in certain character
+ sets, while such encodings are clearly required for 7-bit
+ SMTP.) Second, certain Content-Types may require different
+ types of transfer encoding under different circumstances.
+ For example, many PostScript bodies might consist entirely
+ of short lines of 7-bit data and hence require little or no
+ encoding. Other PostScript bodies (especially those using
+ Level 2 PostScript's binary encoding mechanism) may only be
+ reasonably represented using a binary transport encoding.
+ Finally, since Content-Type is intended to be an open-ended
+ specification mechanism, strict specification of an
+ association between Content-Types and encodings effectively
+ couples the specification of an application protocol with a
+ specific lower-level transport. This is not desirable since
+ the developers of a Content-Type should not have to be aware
+ of all the transports in use and what their limitations are.
+
+ NOTE ON TRANSLATING ENCODINGS: The quoted-printable and
+ base64 encodings are designed so that conversion between
+ them is possible. The only issue that arises in such a
+ conversion is the handling of line breaks. When converting
+ from quoted-printable to base64 a line break must be
+ converted into a CRLF sequence. Similarly, a CRLF sequence
+
+
+
+ Borenstein & Freed [Page 13]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ in base64 data should be converted to a quoted-printable
+ line break, but ONLY when converting text data.
+
+ NOTE ON CANONICAL ENCODING MODEL: There was some
+ confusion, in earlier drafts of this memo, regarding the
+ model for when email data was to be converted to canonical
+ form and encoded, and in particular how this process would
+ affect the treatment of CRLFs, given that the representation
+ of newlines varies greatly from system to system. For this
+ reason, a canonical model for encoding is presented as
+ Appendix H.
+
+ 5.1 Quoted-Printable Content-Transfer-Encoding
+
+ The Quoted-Printable encoding is intended to represent data
+ that largely consists of octets that correspond to printable
+ characters in the ASCII character set. It encodes the data
+ in such a way that the resulting octets are unlikely to be
+ modified by mail transport. If the data being encoded are
+ mostly ASCII text, the encoded form of the data remains
+ largely recognizable by humans. A body which is entirely
+ ASCII may also be encoded in Quoted-Printable to ensure the
+ integrity of the data should the message pass through a
+ character-translating, and/or line-wrapping gateway.
+
+ In this encoding, octets are to be represented as determined
+ by the following rules:
+
+ Rule #1: (General 8-bit representation) Any octet,
+ except those indicating a line break according to the
+ newline convention of the canonical form of the data
+ being encoded, may be represented by an "=" followed by
+ a two digit hexadecimal representation of the octet's
+ value. The digits of the hexadecimal alphabet, for this
+ purpose, are "0123456789ABCDEF". Uppercase letters must
+ be
+ used when sending hexadecimal data, though a robust
+ implementation may choose to recognize lowercase
+ letters on receipt. Thus, for example, the value 12
+ (ASCII form feed) can be represented by "=0C", and the
+ value 61 (ASCII EQUAL SIGN) can be represented by
+ "=3D". Except when the following rules allow an
+ alternative encoding, this rule is mandatory.
+
+ Rule #2: (Literal representation) Octets with decimal
+ values of 33 through 60 inclusive, and 62 through 126,
+ inclusive, MAY be represented as the ASCII characters
+ which correspond to those octets (EXCLAMATION POINT
+ through LESS THAN, and GREATER THAN through TILDE,
+ respectively).
+
+ Rule #3: (White Space): Octets with values of 9 and 32
+ MAY be represented as ASCII TAB (HT) and SPACE
+ characters, respectively, but MUST NOT be so
+
+
+
+ Borenstein & Freed [Page 14]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ represented at the end of an encoded line. Any TAB (HT)
+ or SPACE characters on an encoded line MUST thus be
+ followed on that line by a printable character. In
+ particular, an "=" at the end of an encoded line,
+ indicating a soft line break (see rule #5) may follow
+ one or more TAB (HT) or SPACE characters. It follows
+ that an octet with value 9 or 32 appearing at the end
+ of an encoded line must be represented according to
+ Rule #1. This rule is necessary because some MTAs
+ (Message Transport Agents, programs which transport
+ messages from one user to another, or perform a part of
+ such transfers) are known to pad lines of text with
+ SPACEs, and others are known to remove "white space"
+ characters from the end of a line. Therefore, when
+ decoding a Quoted-Printable body, any trailing white
+ space on a line must be deleted, as it will necessarily
+ have been added by intermediate transport agents.
+
+ Rule #4 (Line Breaks): A line break in a text body
+ part, independent of what its representation is
+ following the canonical representation of the data
+ being encoded, must be represented by a (RFC 822) line
+ break, which is a CRLF sequence, in the Quoted-
+ Printable encoding. If isolated CRs and LFs, or LF CR
+ and CR LF sequences are allowed to appear in binary
+ data according to the canonical form, they must be
+ represented using the "=0D", "=0A", "=0A=0D" and
+ "=0D=0A" notations respectively.
+
+ Note that many implementation may elect to encode the
+ local representation of various content types directly.
+ In particular, this may apply to plain text material on
+ systems that use newline conventions other than CRLF
+ delimiters. Such an implementation is permissible, but
+ the generation of line breaks must be generalized to
+ account for the case where alternate representations of
+ newline sequences are used.
+
+ Rule #5 (Soft Line Breaks): The Quoted-Printable
+ encoding REQUIRES that encoded lines be no more than 76
+ characters long. If longer lines are to be encoded with
+ the Quoted-Printable encoding, 'soft' line breaks must
+ be used. An equal sign as the last character on a
+ encoded line indicates such a non-significant ('soft')
+ line break in the encoded text. Thus if the "raw" form
+ of the line is a single unencoded line that says:
+
+ Now's the time for all folk to come to the aid of
+ their country.
+
+ This can be represented, in the Quoted-Printable
+ encoding, as
+
+
+
+
+
+ Borenstein & Freed [Page 15]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Now's the time =
+ for all folk to come=
+ to the aid of their country.
+
+ This provides a mechanism with which long lines are
+ encoded in such a way as to be restored by the user
+ agent. The 76 character limit does not count the
+ trailing CRLF, but counts all other characters,
+ including any equal signs.
+
+ Since the hyphen character ("-") is represented as itself in
+ the Quoted-Printable encoding, care must be taken, when
+ encapsulating a quoted-printable encoded body in a multipart
+ entity, to ensure that the encapsulation boundary does not
+ appear anywhere in the encoded body. (A good strategy is to
+ choose a boundary that includes a character sequence such as
+ "=_" which can never appear in a quoted-printable body. See
+ the definition of multipart messages later in this
+ document.)
+
+ NOTE: The quoted-printable encoding represents something of
+ a compromise between readability and reliability in
+ transport. Bodies encoded with the quoted-printable
+ encoding will work reliably over most mail gateways, but may
+ not work perfectly over a few gateways, notably those
+ involving translation into EBCDIC. (In theory, an EBCDIC
+ gateway could decode a quoted-printable body and re-encode
+ it using base64, but such gateways do not yet exist.) A
+ higher level of confidence is offered by the base64
+ Content-Transfer-Encoding. A way to get reasonably reliable
+ transport through EBCDIC gateways is to also quote the ASCII
+ characters
+
+ !"#$@[\]^`{|}~
+
+ according to rule #1. See Appendix B for more information.
+
+ Because quoted-printable data is generally assumed to be
+ line-oriented, it is to be expected that the breaks between
+ the lines of quoted printable data may be altered in
+ transport, in the same manner that plain text mail has
+ always been altered in Internet mail when passing between
+ systems with differing newline conventions. If such
+ alterations are likely to constitute a corruption of the
+ data, it is probably more sensible to use the base64
+ encoding rather than the quoted-printable encoding.
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 16]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 5.2 Base64 Content-Transfer-Encoding
+
+ The Base64 Content-Transfer-Encoding is designed to
+ represent arbitrary sequences of octets in a form that is
+ not humanly readable. The encoding and decoding algorithms
+ are simple, but the encoded data are consistently only about
+ 33 percent larger than the unencoded data. This encoding is
+ based on the one used in Privacy Enhanced Mail applications,
+ as defined in RFC 1113. The base64 encoding is adapted
+ from RFC 1113, with one change: base64 eliminates the "*"
+ mechanism for embedded clear text.
+
+ A 65-character subset of US-ASCII is used, enabling 6 bits
+ to be represented per printable character. (The extra 65th
+ character, "=", is used to signify a special processing
+ function.)
+
+ NOTE: This subset has the important property that it is
+ represented identically in all versions of ISO 646,
+ including US ASCII, and all characters in the subset are
+ also represented identically in all versions of EBCDIC.
+ Other popular encodings, such as the encoding used by the
+ UUENCODE utility and the base85 encoding specified as part
+ of Level 2 PostScript, do not share these properties, and
+ thus do not fulfill the portability requirements a binary
+ transport encoding for mail must meet.
+
+ The encoding process represents 24-bit groups of input bits
+ as output strings of 4 encoded characters. Proceeding from
+ left to right, a 24-bit input group is formed by
+ concatenating 3 8-bit input groups. These 24 bits are then
+ treated as 4 concatenated 6-bit groups, each of which is
+ translated into a single digit in the base64 alphabet. When
+ encoding a bit stream via the base64 encoding, the bit
+ stream must be presumed to be ordered with the most-
+ significant-bit first. That is, the first bit in the stream
+ will be the high-order bit in the first byte, and the eighth
+ bit will be the low-order bit in the first byte, and so on.
+
+ Each 6-bit group is used as an index into an array of 64
+ printable characters. The character referenced by the index
+ is placed in the output string. These characters, identified
+ in Table 1, below, are selected so as to be universally
+ representable, and the set excludes characters with
+ particular significance to SMTP (e.g., ".", "CR", "LF") and
+ to the encapsulation boundaries defined in this document
+ (e.g., "-").
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 17]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Table 1: The Base64 Alphabet
+
+ Value Encoding Value Encoding Value Encoding Value
+ Encoding
+ 0 A 17 R 34 i 51 z
+ 1 B 18 S 35 j 52 0
+ 2 C 19 T 36 k 53 1
+ 3 D 20 U 37 l 54 2
+ 4 E 21 V 38 m 55 3
+ 5 F 22 W 39 n 56 4
+ 6 G 23 X 40 o 57 5
+ 7 H 24 Y 41 p 58 6
+ 8 I 25 Z 42 q 59 7
+ 9 J 26 a 43 r 60 8
+ 10 K 27 b 44 s 61 9
+ 11 L 28 c 45 t 62 +
+ 12 M 29 d 46 u 63 /
+ 13 N 30 e 47 v
+ 14 O 31 f 48 w (pad) =
+ 15 P 32 g 49 x
+ 16 Q 33 h 50 y
+
+ The output stream (encoded bytes) must be represented in
+ lines of no more than 76 characters each. All line breaks
+ or other characters not found in Table 1 must be ignored by
+ decoding software. In base64 data, characters other than
+ those in Table 1, line breaks, and other white space
+ probably indicate a transmission error, about which a
+ warning message or even a message rejection might be
+ appropriate under some circumstances.
+
+ Special processing is performed if fewer than 24 bits are
+ available at the end of the data being encoded. A full
+ encoding quantum is always completed at the end of a body.
+ When fewer than 24 input bits are available in an input
+ group, zero bits are added (on the right) to form an
+ integral number of 6-bit groups. Output character positions
+ which are not required to represent actual input data are
+ set to the character "=". Since all base64 input is an
+ integral number of octets, only the following cases can
+ arise: (1) the final quantum of encoding input is an
+ integral multiple of 24 bits; here, the final unit of
+ encoded output will be an integral multiple of 4 characters
+ with no "=" padding, (2) the final quantum of encoding input
+ is exactly 8 bits; here, the final unit of encoded output
+ will be two characters followed by two "=" padding
+ characters, or (3) the final quantum of encoding input is
+ exactly 16 bits; here, the final unit of encoded output will
+ be three characters followed by one "=" padding character.
+
+ Care must be taken to use the proper octets for line breaks
+ if base64 encoding is applied directly to text material that
+ has not been converted to canonical form. In particular,
+ text line breaks should be converted into CRLF sequences
+
+
+
+ Borenstein & Freed [Page 18]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ prior to base64 encoding. The important thing to note is
+ that this may be done directly by the encoder rather than in
+ a prior canonicalization step in some implementations.
+
+ NOTE: There is no need to worry about quoting apparent
+ encapsulation boundaries within base64-encoded parts of
+ multipart entities because no hyphen characters are used in
+ the base64 encoding.
+
+ 6 Additional Optional Content- Header Fields
+
+ 6.1 Optional Content-ID Header Field
+
+ In constructing a high-level user agent, it may be desirable
+ to allow one body to make reference to another.
+ Accordingly, bodies may be labeled using the "Content-ID"
+ header field, which is syntactically identical to the
+ "Message-ID" header field:
+
+ Content-ID := msg-id
+
+ Like the Message-ID values, Content-ID values must be
+ generated to be as unique as possible.
+
+ 6.2 Optional Content-Description Header Field
+
+ The ability to associate some descriptive information with a
+ given body is often desirable. For example, it may be useful
+ to mark an "image" body as "a picture of the Space Shuttle
+ Endeavor." Such text may be placed in the Content-
+ Description header field.
+
+ Content-Description := *text
+
+ The description is presumed to be given in the US-ASCII
+ character set, although the mechanism specified in [RFC-
+ 1342] may be used for non-US-ASCII Content-Description
+ values.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 19]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7 The Predefined Content-Type Values
+
+ This document defines seven initial Content-Type values and
+ an extension mechanism for private or experimental types.
+ Further standard types must be defined by new published
+ specifications. It is expected that most innovation in new
+ types of mail will take place as subtypes of the seven types
+ defined here. The most essential characteristics of the
+ seven content-types are summarized in Appendix G.
+
+ 7.1 The Text Content-Type
+
+ The text Content-Type is intended for sending material which
+ is principally textual in form. It is the default Content-
+ Type. A "charset" parameter may be used to indicate the
+ character set of the body text. The primary subtype of text
+ is "plain". This indicates plain (unformatted) text. The
+ default Content-Type for Internet mail is "text/plain;
+ charset=us-ascii".
+
+ Beyond plain text, there are many formats for representing
+ what might be known as "extended text" -- text with embedded
+ formatting and presentation information. An interesting
+ characteristic of many such representations is that they are
+ to some extent readable even without the software that
+ interprets them. It is useful, then, to distinguish them,
+ at the highest level, from such unreadable data as images,
+ audio, or text represented in an unreadable form. In the
+ absence of appropriate interpretation software, it is
+ reasonable to show subtypes of text to the user, while it is
+ not reasonable to do so with most nontextual data.
+
+ Such formatted textual data should be represented using
+ subtypes of text. Plausible subtypes of text are typically
+ given by the common name of the representation format, e.g.,
+ "text/richtext".
+
+ 7.1.1 The charset parameter
+
+ A critical parameter that may be specified in the Content-
+ Type field for text data is the character set. This is
+ specified with a "charset" parameter, as in:
+
+ Content-type: text/plain; charset=us-ascii
+
+ Unlike some other parameter values, the values of the
+ charset parameter are NOT case sensitive. The default
+ character set, which must be assumed in the absence of a
+ charset parameter, is US-ASCII.
+
+ An initial list of predefined character set names can be
+ found at the end of this section. Additional character sets
+ may be registered with IANA as described in Appendix F,
+ although the standardization of their use requires the usual
+
+
+
+ Borenstein & Freed [Page 20]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ IAB review and approval. Note that if the specified
+ character set includes 8-bit data, a Content-Transfer-
+ Encoding header field and a corresponding encoding on the
+ data are required in order to transmit the body via some
+ mail transfer protocols, such as SMTP.
+
+ The default character set, US-ASCII, has been the subject of
+ some confusion and ambiguity in the past. Not only were
+ there some ambiguities in the definition, there have been
+ wide variations in practice. In order to eliminate such
+ ambiguity and variations in the future, it is strongly
+ recommended that new user agents explicitly specify a
+ character set via the Content-Type header field. "US-ASCII"
+ does not indicate an arbitrary seven-bit character code, but
+ specifies that the body uses character coding that uses the
+ exact correspondence of codes to characters specified in
+ ASCII. National use variations of ISO 646 [ISO-646] are NOT
+ ASCII and their use in Internet mail is explicitly
+ discouraged. The omission of the ISO 646 character set is
+ deliberate in this regard. The character set name of "US-
+ ASCII" explicitly refers to ANSI X3.4-1986 [US-ASCII] only.
+ The character set name "ASCII" is reserved and must not be
+ used for any purpose.
+
+ NOTE: RFC 821 explicitly specifies "ASCII", and references
+ an earlier version of the American Standard. Insofar as one
+ of the purposes of specifying a Content-Type and character
+ set is to permit the receiver to unambiguously determine how
+ the sender intended the coded message to be interpreted,
+ assuming anything other than "strict ASCII" as the default
+ would risk unintentional and incompatible changes to the
+ semantics of messages now being transmitted. This also
+ implies that messages containing characters coded according
+ to national variations on ISO 646, or using code-switching
+ procedures (e.g., those of ISO 2022), as well as 8-bit or
+ multiple octet character encodings MUST use an appropriate
+ character set specification to be consistent with this
+ specification.
+
+ The complete US-ASCII character set is listed in [US-ASCII].
+ Note that the control characters including DEL (0-31, 127)
+ have no defined meaning apart from the combination CRLF
+ (ASCII values 13 and 10) indicating a new line. Two of the
+ characters have de facto meanings in wide use: FF (12) often
+ means "start subsequent text on the beginning of a new
+ page"; and TAB or HT (9) often (though not always) means
+ "move the cursor to the next available column after the
+ current position where the column number is a multiple of 8
+ (counting the first column as column 0)." Apart from this,
+ any use of the control characters or DEL in a body must be
+ part of a private agreement between the sender and
+ recipient. Such private agreements are discouraged and
+ should be replaced by the other capabilities of this
+ document.
+
+
+
+ Borenstein & Freed [Page 21]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ NOTE: Beyond US-ASCII, an enormous proliferation of
+ character sets is possible. It is the opinion of the IETF
+ working group that a large number of character sets is NOT a
+ good thing. We would prefer to specify a single character
+ set that can be used universally for representing all of the
+ world's languages in electronic mail. Unfortunately,
+ existing practice in several communities seems to point to
+ the continued use of multiple character sets in the near
+ future. For this reason, we define names for a small number
+ of character sets for which a strong constituent base
+ exists. It is our hope that ISO 10646 or some other
+ effort will eventually define a single world character set
+ which can then be specified for use in Internet mail, but in
+ the advance of that definition we cannot specify the use of
+ ISO 10646, Unicode, or any other character set whose
+ definition is, as of this writing, incomplete.
+
+ The defined charset values are:
+
+ US-ASCII -- as defined in [US-ASCII].
+
+ ISO-8859-X -- where "X" is to be replaced, as
+ necessary, for the parts of ISO-8859 [ISO-
+ 8859]. Note that the ISO 646 character sets
+ have deliberately been omitted in favor of
+ their 8859 replacements, which are the
+ designated character sets for Internet mail.
+ As of the publication of this document, the
+ legitimate values for "X" are the digits 1
+ through 9.
+
+ Note that the character set used, if anything other than
+ US-ASCII, must always be explicitly specified in the
+ Content-Type field.
+
+ No other character set name may be used in Internet mail
+ without the publication of a formal specification and its
+ registration with IANA as described in Appendix F, or by
+ private agreement, in which case the character set name must
+ begin with "X-".
+
+ Implementors are discouraged from defining new character
+ sets for mail use unless absolutely necessary.
+
+ The "charset" parameter has been defined primarily for the
+ purpose of textual data, and is described in this section
+ for that reason. However, it is conceivable that non-
+ textual data might also wish to specify a charset value for
+ some purpose, in which case the same syntax and values
+ should be used.
+
+ In general, mail-sending software should always use the
+ "lowest common denominator" character set possible. For
+ example, if a body contains only US-ASCII characters, it
+
+
+
+ Borenstein & Freed [Page 22]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ should be marked as being in the US-ASCII character set, not
+ ISO-8859-1, which, like all the ISO-8859 family of character
+ sets, is a superset of US-ASCII. More generally, if a
+ widely-used character set is a subset of another character
+ set, and a body contains only characters in the widely-used
+ subset, it should be labeled as being in that subset. This
+ will increase the chances that the recipient will be able to
+ view the mail correctly.
+
+ 7.1.2 The Text/plain subtype
+
+ The primary subtype of text is "plain". This indicates
+ plain (unformatted) text. The default Content-Type for
+ Internet mail, "text/plain; charset=us-ascii", describes
+ existing Internet practice, that is, it is the type of body
+ defined by RFC 822.
+
+ 7.1.3 The Text/richtext subtype
+
+ In order to promote the wider interoperability of simple
+ formatted text, this document defines an extremely simple
+ subtype of "text", the "richtext" subtype. This subtype was
+ designed to meet the following criteria:
+
+ 1. The syntax must be extremely simple to parse,
+ so that even teletype-oriented mail systems can
+ easily strip away the formatting information and
+ leave only the readable text.
+
+ 2. The syntax must be extensible to allow for new
+ formatting commands that are deemed essential.
+
+ 3. The capabilities must be extremely limited, to
+ ensure that it can represent no more than is
+ likely to be representable by the user's primary
+ word processor. While this limits what can be
+ sent, it increases the likelihood that what is
+ sent can be properly displayed.
+
+ 4. The syntax must be compatible with SGML, so
+ that, with an appropriate DTD (Document Type
+ Definition, the standard mechanism for defining a
+ document type using SGML), a general SGML parser
+ could be made to parse richtext. However, despite
+ this compatibility, the syntax should be far
+ simpler than full SGML, so that no SGML knowledge
+ is required in order to implement it.
+
+ The syntax of "richtext" is very simple. It is assumed, at
+ the top-level, to be in the US-ASCII character set, unless
+ of course a different charset parameter was specified in the
+ Content-type field. All characters represent themselves,
+ with the exception of the "<" character (ASCII 60), which is
+ used to mark the beginning of a formatting command.
+
+
+
+ Borenstein & Freed [Page 23]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Formatting instructions consist of formatting commands
+ surrounded by angle brackets ("<>", ASCII 60 and 62). Each
+ formatting command may be no more than 40 characters in
+ length, all in US-ASCII, restricted to the alphanumeric and
+ hyphen ("-") characters. Formatting commands may be preceded
+ by a forward slash or solidus ("/", ASCII 47), making them
+ negations, and such negations must always exist to balance
+ the initial opening commands, except as noted below. Thus,
+ if the formatting command "<bold>" appears at some point,
+ there must later be a "</bold>" to balance it. There are
+ only three exceptions to this "balancing" rule: First, the
+ command "<lt>" is used to represent a literal "<" character.
+ Second, the command "<nl>" is used to represent a required
+ line break. (Otherwise, CRLFs in the data are treated as
+ equivalent to a single SPACE character.) Finally, the
+ command "<np>" is used to represent a page break. (NOTE:
+ The 40 character limit on formatting commands does not
+ include the "<", ">", or "/" characters that might be
+ attached to such commands.)
+
+ Initially defined formatting commands, not all of which will
+ be implemented by all richtext implementations, include:
+
+ Bold -- causes the subsequent text to be in a bold
+ font.
+ Italic -- causes the subsequent text to be in an italic
+ font.
+ Fixed -- causes the subsequent text to be in a fixed
+ width font.
+ Smaller -- causes the subsequent text to be in a
+ smaller font.
+ Bigger -- causes the subsequent text to be in a bigger
+ font.
+ Underline -- causes the subsequent text to be
+ underlined.
+ Center -- causes the subsequent text to be centered.
+ FlushLeft -- causes the subsequent text to be left
+ justified.
+ FlushRight -- causes the subsequent text to be right
+ justified.
+ Indent -- causes the subsequent text to be indented at
+ the left margin.
+ IndentRight -- causes the subsequent text to be
+ indented at the right margin.
+ Outdent -- causes the subsequent text to be outdented
+ at the left margin.
+ OutdentRight -- causes the subsequent text to be
+ outdented at the right margin.
+ SamePage -- causes the subsequent text to be grouped,
+ if possible, on one page.
+ Subscript -- causes the subsequent text to be
+ interpreted as a subscript.
+
+
+
+
+
+ Borenstein & Freed [Page 24]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Superscript -- causes the subsequent text to be
+ interpreted as a superscript.
+ Heading -- causes the subsequent text to be interpreted
+ as a page heading.
+ Footing -- causes the subsequent text to be interpreted
+ as a page footing.
+ ISO-8859-X (for any value of X that is legal as a
+ "charset" parameter) -- causes the subsequent text
+ to be interpreted as text in the appropriate
+ character set.
+ US-ASCII -- causes the subsequent text to be
+ interpreted as text in the US-ASCII character set.
+ Excerpt -- causes the subsequent text to be interpreted
+ as a textual excerpt from another source.
+ Typically this will be displayed using indentation
+ and an alternate font, but such decisions are up
+ to the viewer.
+ Paragraph -- causes the subsequent text to be
+ interpreted as a single paragraph, with
+ appropriate paragraph breaks (typically blank
+ space) before and after.
+ Signature -- causes the subsequent text to be
+ interpreted as a "signature". Some systems may
+ wish to display signatures in a smaller font or
+ otherwise set them apart from the main text of the
+ message.
+ Comment -- causes the subsequent text to be interpreted
+ as a comment, and hence not shown to the reader.
+ No-op -- has no effect on the subsequent text.
+ lt -- <lt> is replaced by a literal "<" character. No
+ balancing </lt> is allowed.
+ nl -- <nl> causes a line break. No balancing </nl> is
+ allowed.
+ np -- <np> causes a page break. No balancing </np> is
+ allowed.
+
+ Each positive formatting command affects all subsequent text
+ until the matching negative formatting command. Such pairs
+ of formatting commands must be properly balanced and nested.
+ Thus, a proper way to describe text in bold italics is:
+
+ <bold><italic>the-text</italic></bold>
+
+ or, alternately,
+
+ <italic><bold>the-text</bold></italic>
+
+ but, in particular, the following is illegal
+ richtext:
+
+ <bold><italic>the-text</bold></italic>
+
+ NOTE: The nesting requirement for formatting commands
+ imposes a slightly higher burden upon the composers of
+
+
+
+ Borenstein & Freed [Page 25]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ richtext bodies, but potentially simplifies richtext
+ displayers by allowing them to be stack-based. The main
+ goal of richtext is to be simple enough to make multifont,
+ formatted email widely readable, so that those with the
+ capability of sending it will be able to do so with
+ confidence. Thus slightly increased complexity in the
+ composing software was deemed a reasonable tradeoff for
+ simplified reading software. Nonetheless, implementors of
+ richtext readers are encouraged to follow the general
+ Internet guidelines of being conservative in what you send
+ and liberal in what you accept. Those implementations that
+ can do so are encouraged to deal reasonably with improperly
+ nested richtext.
+
+ Implementations must regard any unrecognized formatting
+ command as equivalent to "No-op", thus facilitating future
+ extensions to "richtext". Private extensions may be defined
+ using formatting commands that begin with "X-", by analogy
+ to Internet mail header field names.
+
+ It is worth noting that no special behavior is required for
+ the TAB (HT) character. It is recommended, however, that, at
+ least when fixed-width fonts are in use, the common
+ semantics of the TAB (HT) character should be observed,
+ namely that it moves to the next column position that is a
+ multiple of 8. (In other words, if a TAB (HT) occurs in
+ column n, where the leftmost column is column 0, then that
+ TAB (HT) should be replaced by 8-(n mod 8) SPACE
+ characters.)
+
+ Richtext also differentiates between "hard" and "soft" line
+ breaks. A line break (CRLF) in the richtext data stream is
+ interpreted as a "soft" line break, one that is included
+ only for purposes of mail transport, and is to be treated as
+ white space by richtext interpreters. To include a "hard"
+ line break (one that must be displayed as such), the "<nl>"
+ or "<paragraph> formatting constructs should be used. In
+ general, a soft line break should be treated as white space,
+ but when soft line breaks immediately follow a <nl> or a
+ </paragraph> tag they should be ignored rather than treated
+ as white space.
+
+ Putting all this together, the following "text/richtext"
+ body fragment:
+
+ <bold>Now</bold> is the time for
+ <italic>all</italic> good men
+ <smaller>(and <lt>women>)</smaller> to
+ <ignoreme></ignoreme> come
+
+ to the aid of their
+ <nl>
+
+
+
+
+
+ Borenstein & Freed [Page 26]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ beloved <nl><nl>country. <comment> Stupid
+ quote! </comment> -- the end
+
+ represents the following formatted text (which will, no
+ doubt, look cryptic in the text-only version of this
+ document):
+
+ Now is the time for all good men (and <women>) to
+ come to the aid of their
+ beloved
+
+ country. -- the end
+
+ Richtext conformance: A minimal richtext implementation is
+ one that simply converts "<lt>" to "<", converts CRLFs to
+ SPACE, converts <nl> to a newline according to local newline
+ convention, removes everything between a <comment> command
+ and the next balancing </comment> command, and removes all
+ other formatting commands (all text enclosed in angle
+ brackets).
+
+ NOTE ON THE RELATIONSHIP OF RICHTEXT TO SGML: Richtext is
+ decidedly not SGML, and must not be used to transport
+ arbitrary SGML documents. Those who wish to use SGML
+ document types as a mail transport format must define a new
+ text or application subtype, e.g., "text/sgml-dtd-whatever"
+ or "application/sgml-dtd-whatever", depending on the
+ perceived readability of the DTD in use. Richtext is
+ designed to be compatible with SGML, and specifically so
+ that it will be possible to define a richtext DTD if one is
+ needed. However, this does not imply that arbitrary SGML
+ can be called richtext, nor that richtext implementors have
+ any need to understand SGML; the description in this
+ document is a complete definition of richtext, which is far
+ simpler than complete SGML.
+
+ NOTE ON THE INTENDED USE OF RICHTEXT: It is recognized that
+ implementors of future mail systems will want rich text
+ functionality far beyond that currently defined for
+ richtext. The intent of richtext is to provide a common
+ format for expressing that functionality in a form in which
+ much of it, at least, will be understood by interoperating
+ software. Thus, in particular, software with a richer
+ notion of formatted text than richtext can still use
+ richtext as its basic representation, but can extend it with
+ new formatting commands and by hiding information specific
+ to that software system in richtext comments. As such
+ systems evolve, it is expected that the definition of
+ richtext will be further refined by future published
+ specifications, but richtext as defined here provides a
+ platform on which evolutionary refinements can be based.
+
+ IMPLEMENTATION NOTE: In some environments, it might be
+ impossible to combine certain richtext formatting commands,
+
+
+
+ Borenstein & Freed [Page 27]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ whereas in others they might be combined easily. For
+ example, the combination of <bold> and <italic> might
+ produce bold italics on systems that support such fonts, but
+ there exist systems that can make text bold or italicized,
+ but not both. In such cases, the most recently issued
+ recognized formatting command should be preferred.
+
+ One of the major goals in the design of richtext was to make
+ it so simple that even text-only mailers will implement
+ richtext-to-plain-text translators, thus increasing the
+ likelihood that multifont text will become "safe" to use
+ very widely. To demonstrate this simplicity, an extremely
+ simple 35-line C program that converts richtext input into
+ plain text output is included in Appendix D.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 28]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.2 The Multipart Content-Type
+
+ In the case of multiple part messages, in which one or more
+ different sets of data are combined in a single body, a
+ "multipart" Content-Type field must appear in the entity's
+ header. The body must then contain one or more "body parts,"
+ each preceded by an encapsulation boundary, and the last one
+ followed by a closing boundary. Each part starts with an
+ encapsulation boundary, and then contains a body part
+ consisting of header area, a blank line, and a body area.
+ Thus a body part is similar to an RFC 822 message in syntax,
+ but different in meaning.
+
+ A body part is NOT to be interpreted as actually being an
+ RFC 822 message. To begin with, NO header fields are
+ actually required in body parts. A body part that starts
+ with a blank line, therefore, is allowed and is a body part
+ for which all default values are to be assumed. In such a
+ case, the absence of a Content-Type header field implies
+ that the encapsulation is plain US-ASCII text. The only
+ header fields that have defined meaning for body parts are
+ those the names of which begin with "Content-". All other
+ header fields are generally to be ignored in body parts.
+ Although they should generally be retained in mail
+ processing, they may be discarded by gateways if necessary.
+ Such other fields are permitted to appear in body parts but
+ should not be depended on. "X-" fields may be created for
+ experimental or private purposes, with the recognition that
+ the information they contain may be lost at some gateways.
+
+ The distinction between an RFC 822 message and a body part
+ is subtle, but important. A gateway between Internet and
+ X.400 mail, for example, must be able to tell the difference
+ between a body part that contains an image and a body part
+ that contains an encapsulated message, the body of which is
+ an image. In order to represent the latter, the body part
+ must have "Content-Type: message", and its body (after the
+ blank line) must be the encapsulated message, with its own
+ "Content-Type: image" header field. The use of similar
+ syntax facilitates the conversion of messages to body parts,
+ and vice versa, but the distinction between the two must be
+ understood by implementors. (For the special case in which
+ all parts actually are messages, a "digest" subtype is also
+ defined.)
+
+ As stated previously, each body part is preceded by an
+ encapsulation boundary. The encapsulation boundary MUST NOT
+ appear inside any of the encapsulated parts. Thus, it is
+ crucial that the composing agent be able to choose and
+ specify the unique boundary that will separate the parts.
+
+ All present and future subtypes of the "multipart" type must
+ use an identical syntax. Subtypes may differ in their
+ semantics, and may impose additional restrictions on syntax,
+
+
+
+ Borenstein & Freed [Page 29]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ but must conform to the required syntax for the multipart
+ type. This requirement ensures that all conformant user
+ agents will at least be able to recognize and separate the
+ parts of any multipart entity, even of an unrecognized
+ subtype.
+
+ As stated in the definition of the Content-Transfer-Encoding
+ field, no encoding other than "7bit", "8bit", or "binary" is
+ permitted for entities of type "multipart". The multipart
+ delimiters and header fields are always 7-bit ASCII in any
+ case, and data within the body parts can be encoded on a
+ part-by-part basis, with Content-Transfer-Encoding fields
+ for each appropriate body part.
+
+ Mail gateways, relays, and other mail handling agents are
+ commonly known to alter the top-level header of an RFC 822
+ message. In particular, they frequently add, remove, or
+ reorder header fields. Such alterations are explicitly
+ forbidden for the body part headers embedded in the bodies
+ of messages of type "multipart."
+
+ 7.2.1 Multipart: The common syntax
+
+ All subtypes of "multipart" share a common syntax, defined
+ in this section. A simple example of a multipart message
+ also appears in this section. An example of a more complex
+ multipart message is given in Appendix C.
+
+ The Content-Type field for multipart entities requires one
+ parameter, "boundary", which is used to specify the
+ encapsulation boundary. The encapsulation boundary is
+ defined as a line consisting entirely of two hyphen
+ characters ("-", decimal code 45) followed by the boundary
+ parameter value from the Content-Type header field.
+
+ NOTE: The hyphens are for rough compatibility with the
+ earlier RFC 934 method of message encapsulation, and for
+ ease of searching for the boundaries in some
+ implementations. However, it should be noted that multipart
+ messages are NOT completely compatible with RFC 934
+ encapsulations; in particular, they do not obey RFC 934
+ quoting conventions for embedded lines that begin with
+ hyphens. This mechanism was chosen over the RFC 934
+ mechanism because the latter causes lines to grow with each
+ level of quoting. The combination of this growth with the
+ fact that SMTP implementations sometimes wrap long lines
+ made the RFC 934 mechanism unsuitable for use in the event
+ that deeply-nested multipart structuring is ever desired.
+
+ Thus, a typical multipart Content-Type header field might
+ look like this:
+
+ Content-Type: multipart/mixed;
+
+
+
+
+ Borenstein & Freed [Page 30]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ boundary=gc0p4Jq0M2Yt08jU534c0p
+
+ This indicates that the entity consists of several parts,
+ each itself with a structure that is syntactically identical
+ to an RFC 822 message, except that the header area might be
+ completely empty, and that the parts are each preceded by
+ the line
+
+ --gc0p4Jq0M2Yt08jU534c0p
+
+ Note that the encapsulation boundary must occur at the
+ beginning of a line, i.e., following a CRLF, and that that
+ initial CRLF is considered to be part of the encapsulation
+ boundary rather than part of the preceding part. The
+ boundary must be followed immediately either by another CRLF
+ and the header fields for the next part, or by two CRLFs, in
+ which case there are no header fields for the next part (and
+ it is therefore assumed to be of Content-Type text/plain).
+
+ NOTE: The CRLF preceding the encapsulation line is
+ considered part of the boundary so that it is possible to
+ have a part that does not end with a CRLF (line break).
+ Body parts that must be considered to end with line breaks,
+ therefore, should have two CRLFs preceding the encapsulation
+ line, the first of which is part of the preceding body part,
+ and the second of which is part of the encapsulation
+ boundary.
+
+ The requirement that the encapsulation boundary begins with
+ a CRLF implies that the body of a multipart entity must
+ itself begin with a CRLF before the first encapsulation line
+ -- that is, if the "preamble" area is not used, the entity
+ headers must be followed by TWO CRLFs. This is indeed how
+ such entities should be composed. A tolerant mail reading
+ program, however, may interpret a body of type multipart
+ that begins with an encapsulation line NOT initiated by a
+ CRLF as also being an encapsulation boundary, but a
+ compliant mail sending program must not generate such
+ entities.
+
+ Encapsulation boundaries must not appear within the
+ encapsulations, and must be no longer than 70 characters,
+ not counting the two leading hyphens.
+
+ The encapsulation boundary following the last body part is a
+ distinguished delimiter that indicates that no further body
+ parts will follow. Such a delimiter is identical to the
+ previous delimiters, with the addition of two more hyphens
+ at the end of the line:
+
+ --gc0p4Jq0M2Yt08jU534c0p--
+
+ There appears to be room for additional information prior to
+ the first encapsulation boundary and following the final
+
+
+
+ Borenstein & Freed [Page 31]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ boundary. These areas should generally be left blank, and
+ implementations should ignore anything that appears before
+ the first boundary or after the last one.
+
+ NOTE: These "preamble" and "epilogue" areas are not used
+ because of the lack of proper typing of these parts and the
+ lack of clear semantics for handling these areas at
+ gateways, particularly X.400 gateways.
+
+ NOTE: Because encapsulation boundaries must not appear in
+ the body parts being encapsulated, a user agent must
+ exercise care to choose a unique boundary. The boundary in
+ the example above could have been the result of an algorithm
+ designed to produce boundaries with a very low probability
+ of already existing in the data to be encapsulated without
+ having to prescan the data. Alternate algorithms might
+ result in more 'readable' boundaries for a recipient with an
+ old user agent, but would require more attention to the
+ possibility that the boundary might appear in the
+ encapsulated part. The simplest boundary possible is
+ something like "---", with a closing boundary of "-----".
+
+ As a very simple example, the following multipart message
+ has two parts, both of them plain text, one of them
+ explicitly typed and one of them implicitly typed:
+
+ From: Nathaniel Borenstein <nsb@bellcore.com>
+ To: Ned Freed <ned@innosoft.com>
+ Subject: Sample message
+ MIME-Version: 1.0
+ Content-type: multipart/mixed; boundary="simple
+ boundary"
+
+ This is the preamble. It is to be ignored, though it
+ is a handy place for mail composers to include an
+ explanatory note to non-MIME compliant readers.
+ --simple boundary
+
+ This is implicitly typed plain ASCII text.
+ It does NOT end with a linebreak.
+ --simple boundary
+ Content-type: text/plain; charset=us-ascii
+
+ This is explicitly typed plain ASCII text.
+ It DOES end with a linebreak.
+
+ --simple boundary--
+ This is the epilogue. It is also to be ignored.
+
+ The use of a Content-Type of multipart in a body part within
+ another multipart entity is explicitly allowed. In such
+ cases, for obvious reasons, care must be taken to ensure
+ that each nested multipart entity must use a different
+ boundary delimiter. See Appendix C for an example of nested
+
+
+
+ Borenstein & Freed [Page 32]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ multipart entities.
+
+ The use of the multipart Content-Type with only a single
+ body part may be useful in certain contexts, and is
+ explicitly permitted.
+
+ The only mandatory parameter for the multipart Content-Type
+ is the boundary parameter, which consists of 1 to 70
+ characters from a set of characters known to be very robust
+ through email gateways, and NOT ending with white space.
+ (If a boundary appears to end with white space, the white
+ space must be presumed to have been added by a gateway, and
+ should be deleted.) It is formally specified by the
+ following BNF:
+
+ boundary := 0*69<bchars> bcharsnospace
+
+ bchars := bcharsnospace / " "
+
+ bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /
+ "_"
+ / "," / "-" / "." / "/" / ":" / "=" / "?"
+
+ Overall, the body of a multipart entity may be specified as
+ follows:
+
+ multipart-body := preamble 1*encapsulation
+ close-delimiter epilogue
+
+ encapsulation := delimiter CRLF body-part
+
+ delimiter := CRLF "--" boundary ; taken from Content-Type
+ field.
+ ; when content-type is
+ multipart
+ ; There must be no space
+ ; between "--" and boundary.
+
+ close-delimiter := delimiter "--" ; Again, no space before
+ "--"
+
+ preamble := *text ; to be ignored upon
+ receipt.
+
+ epilogue := *text ; to be ignored upon
+ receipt.
+
+ body-part = <"message" as defined in RFC 822,
+ with all header fields optional, and with the
+ specified delimiter not occurring anywhere in
+ the message body, either on a line by itself
+ or as a substring anywhere. Note that the
+
+
+
+
+
+ Borenstein & Freed [Page 33]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ semantics of a part differ from the semantics
+ of a message, as described in the text.>
+
+ NOTE: Conspicuously missing from the multipart type is a
+ notion of structured, related body parts. In general, it
+ seems premature to try to standardize interpart structure
+ yet. It is recommended that those wishing to provide a more
+ structured or integrated multipart messaging facility should
+ define a subtype of multipart that is syntactically
+ identical, but that always expects the inclusion of a
+ distinguished part that can be used to specify the structure
+ and integration of the other parts, probably referring to
+ them by their Content-ID field. If this approach is used,
+ other implementations will not recognize the new subtype,
+ but will treat it as the primary subtype (multipart/mixed)
+ and will thus be able to show the user the parts that are
+ recognized.
+
+ 7.2.2 The Multipart/mixed (primary) subtype
+
+ The primary subtype for multipart, "mixed", is intended for
+ use when the body parts are independent and intended to be
+ displayed serially. Any multipart subtypes that an
+ implementation does not recognize should be treated as being
+ of subtype "mixed".
+
+ 7.2.3 The Multipart/alternative subtype
+
+ The multipart/alternative type is syntactically identical to
+ multipart/mixed, but the semantics are different. In
+ particular, each of the parts is an "alternative" version of
+ the same information. User agents should recognize that the
+ content of the various parts are interchangeable. The user
+ agent should either choose the "best" type based on the
+ user's environment and preferences, or offer the user the
+ available alternatives. In general, choosing the best type
+ means displaying only the LAST part that can be displayed.
+ This may be used, for example, to send mail in a fancy text
+ format in such a way that it can easily be displayed
+ anywhere:
+
+ From: Nathaniel Borenstein <nsb@bellcore.com>
+ To: Ned Freed <ned@innosoft.com>
+ Subject: Formatted text mail
+ MIME-Version: 1.0
+ Content-Type: multipart/alternative; boundary=boundary42
+
+
+ --boundary42
+ Content-Type: text/plain; charset=us-ascii
+
+ ...plain text version of message goes here....
+
+
+
+
+
+ Borenstein & Freed [Page 34]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ --boundary42
+ Content-Type: text/richtext
+
+ .... richtext version of same message goes here ...
+ --boundary42
+ Content-Type: text/x-whatever
+
+ .... fanciest formatted version of same message goes here
+ ...
+ --boundary42--
+
+ In this example, users whose mail system understood the
+ "text/x-whatever" format would see only the fancy version,
+ while other users would see only the richtext or plain text
+ version, depending on the capabilities of their system.
+
+ In general, user agents that compose multipart/alternative
+ entities should place the body parts in increasing order of
+ preference, that is, with the preferred format last. For
+ fancy text, the sending user agent should put the plainest
+ format first and the richest format last. Receiving user
+ agents should pick and display the last format they are
+ capable of displaying. In the case where one of the
+ alternatives is itself of type "multipart" and contains
+ unrecognized sub-parts, the user agent may choose either to
+ show that alternative, an earlier alternative, or both.
+
+ NOTE: From an implementor's perspective, it might seem more
+ sensible to reverse this ordering, and have the plainest
+ alternative last. However, placing the plainest alternative
+ first is the friendliest possible option when
+ mutlipart/alternative entities are viewed using a non-MIME-
+ compliant mail reader. While this approach does impose some
+ burden on compliant mail readers, interoperability with
+ older mail readers was deemed to be more important in this
+ case.
+
+ It may be the case that some user agents, if they can
+ recognize more than one of the formats, will prefer to offer
+ the user the choice of which format to view. This makes
+ sense, for example, if mail includes both a nicely-formatted
+ image version and an easily-edited text version. What is
+ most critical, however, is that the user not automatically
+ be shown multiple versions of the same data. Either the
+ user should be shown the last recognized version or should
+ explicitly be given the choice.
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 35]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.2.4 The Multipart/digest subtype
+
+ This document defines a "digest" subtype of the multipart
+ Content-Type. This type is syntactically identical to
+ multipart/mixed, but the semantics are different. In
+ particular, in a digest, the default Content-Type value for
+ a body part is changed from "text/plain" to
+ "message/rfc822". This is done to allow a more readable
+ digest format that is largely compatible (except for the
+ quoting convention) with RFC 934.
+
+ A digest in this format might, then, look something like
+ this:
+
+ From: Moderator-Address
+ MIME-Version: 1.0
+ Subject: Internet Digest, volume 42
+ Content-Type: multipart/digest;
+ boundary="---- next message ----"
+
+
+ ------ next message ----
+
+ From: someone-else
+ Subject: my opinion
+
+ ...body goes here ...
+
+ ------ next message ----
+
+ From: someone-else-again
+ Subject: my different opinion
+
+ ... another body goes here...
+
+ ------ next message ------
+
+ 7.2.5 The Multipart/parallel subtype
+
+ This document defines a "parallel" subtype of the multipart
+ Content-Type. This type is syntactically identical to
+ multipart/mixed, but the semantics are different. In
+ particular, in a parallel entity, all of the parts are
+ intended to be presented in parallel, i.e., simultaneously,
+ on hardware and software that are capable of doing so.
+ Composing agents should be aware that many mail readers will
+ lack this capability and will show the parts serially in any
+ event.
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 36]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.3 The Message Content-Type
+
+ It is frequently desirable, in sending mail, to encapsulate
+ another mail message. For this common operation, a special
+ Content-Type, "message", is defined. The primary subtype,
+ message/rfc822, has no required parameters in the Content-
+ Type field. Additional subtypes, "partial" and "External-
+ body", do have required parameters. These subtypes are
+ explained below.
+
+ NOTE: It has been suggested that subtypes of message might
+ be defined for forwarded or rejected messages. However,
+ forwarded and rejected messages can be handled as multipart
+ messages in which the first part contains any control or
+ descriptive information, and a second part, of type
+ message/rfc822, is the forwarded or rejected message.
+ Composing rejection and forwarding messages in this manner
+ will preserve the type information on the original message
+ and allow it to be correctly presented to the recipient, and
+ hence is strongly encouraged.
+
+ As stated in the definition of the Content-Transfer-Encoding
+ field, no encoding other than "7bit", "8bit", or "binary" is
+ permitted for messages or parts of type "message". The
+ message header fields are always US-ASCII in any case, and
+ data within the body can still be encoded, in which case the
+ Content-Transfer-Encoding header field in the encapsulated
+ message will reflect this. Non-ASCII text in the headers of
+ an encapsulated message can be specified using the
+ mechanisms described in [RFC-1342].
+
+ Mail gateways, relays, and other mail handling agents are
+ commonly known to alter the top-level header of an RFC 822
+ message. In particular, they frequently add, remove, or
+ reorder header fields. Such alterations are explicitly
+ forbidden for the encapsulated headers embedded in the
+ bodies of messages of type "message."
+
+ 7.3.1 The Message/rfc822 (primary) subtype
+
+ A Content-Type of "message/rfc822" indicates that the body
+ contains an encapsulated message, with the syntax of an RFC
+ 822 message.
+
+ 7.3.2 The Message/Partial subtype
+
+ A subtype of message, "partial", is defined in order to
+ allow large objects to be delivered as several separate
+ pieces of mail and automatically reassembled by the
+ receiving user agent. (The concept is similar to IP
+ fragmentation/reassembly in the basic Internet Protocols.)
+ This mechanism can be used when intermediate transport
+ agents limit the size of individual messages that can be
+ sent. Content-Type "message/partial" thus indicates that
+
+
+
+ Borenstein & Freed [Page 37]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ the body contains a fragment of a larger message.
+
+ Three parameters must be specified in the Content-Type field
+ of type message/partial: The first, "id", is a unique
+ identifier, as close to a world-unique identifier as
+ possible, to be used to match the parts together. (In
+ general, the identifier is essentially a message-id; if
+ placed in double quotes, it can be any message-id, in
+ accordance with the BNF for "parameter" given earlier in
+ this specification.) The second, "number", an integer, is
+ the part number, which indicates where this part fits into
+ the sequence of fragments. The third, "total", another
+ integer, is the total number of parts. This third subfield
+ is required on the final part, and is optional on the
+ earlier parts. Note also that these parameters may be given
+ in any order.
+
+ Thus, part 2 of a 3-part message may have either of the
+ following header fields:
+
+ Content-Type: Message/Partial;
+ number=2; total=3;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
+
+ Content-Type: Message/Partial;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
+ number=2
+
+ But part 3 MUST specify the total number of parts:
+
+ Content-Type: Message/Partial;
+ number=3; total=3;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
+
+ Note that part numbering begins with 1, not 0.
+
+ When the parts of a message broken up in this manner are put
+ together, the result is a complete RFC 822 format message,
+ which may have its own Content-Type header field, and thus
+ may contain any other data type.
+
+ Message fragmentation and reassembly: The semantics of a
+ reassembled partial message must be those of the "inner"
+ message, rather than of a message containing the inner
+ message. This makes it possible, for example, to send a
+ large audio message as several partial messages, and still
+ have it appear to the recipient as a simple audio message
+ rather than as an encapsulated message containing an audio
+ message. That is, the encapsulation of the message is
+ considered to be "transparent".
+
+ When generating and reassembling the parts of a
+ message/partial message, the headers of the encapsulated
+ message must be merged with the headers of the enclosing
+
+
+
+ Borenstein & Freed [Page 38]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ entities. In this process the following rules must be
+ observed:
+
+ (1) All of the headers from the initial enclosing
+ entity (part one), except those that start with
+ "Content-" and "Message-ID", must be copied, in
+ order, to the new message.
+
+ (2) Only those headers in the enclosed message
+ which start with "Content-" and "Message-ID" must
+ be appended, in order, to the headers of the new
+ message. Any headers in the enclosed message
+ which do not start with "Content-" (except for
+ "Message-ID") will be ignored.
+
+ (3) All of the headers from the second and any
+ subsequent messages will be ignored.
+
+ For example, if an audio message is broken into two parts,
+ the first part might look something like this:
+
+ X-Weird-Header-1: Foo
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Subject: Audio mail
+ Message-ID: id1@host.com
+ MIME-Version: 1.0
+ Content-type: message/partial;
+ id="ABC@host.com";
+ number=1; total=2
+
+ X-Weird-Header-1: Bar
+ X-Weird-Header-2: Hello
+ Message-ID: anotherid@foo.com
+ Content-type: audio/basic
+ Content-transfer-encoding: base64
+
+ ... first half of encoded audio data goes here...
+
+ and the second half might look something like this:
+
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Subject: Audio mail
+ MIME-Version: 1.0
+ Message-ID: id2@host.com
+ Content-type: message/partial;
+ id="ABC@host.com"; number=2; total=2
+
+ ... second half of encoded audio data goes here...
+
+ Then, when the fragmented message is reassembled, the
+ resulting message to be displayed to the user should look
+ something like this:
+
+
+
+ Borenstein & Freed [Page 39]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ X-Weird-Header-1: Foo
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Subject: Audio mail
+ Message-ID: anotherid@foo.com
+ MIME-Version: 1.0
+ Content-type: audio/basic
+ Content-transfer-encoding: base64
+
+ ... first half of encoded audio data goes here...
+ ... second half of encoded audio data goes here...
+
+ It should be noted that, because some message transfer
+ agents may choose to automatically fragment large messages,
+ and because such agents may use different fragmentation
+ thresholds, it is possible that the pieces of a partial
+ message, upon reassembly, may prove themselves to comprise a
+ partial message. This is explicitly permitted.
+
+ It should also be noted that the inclusion of a "References"
+ field in the headers of the second and subsequent pieces of
+ a fragmented message that references the Message-Id on the
+ previous piece may be of benefit to mail readers that
+ understand and track references. However, the generation of
+ such "References" fields is entirely optional.
+
+ 7.3.3 The Message/External-Body subtype
+
+ The external-body subtype indicates that the actual body
+ data are not included, but merely referenced. In this case,
+ the parameters describe a mechanism for accessing the
+ external data.
+
+ When a message body or body part is of type
+ "message/external-body", it consists of a header, two
+ consecutive CRLFs, and the message header for the
+ encapsulated message. If another pair of consecutive CRLFs
+ appears, this of course ends the message header for the
+ encapsulated message. However, since the encapsulated
+ message's body is itself external, it does NOT appear in the
+ area that follows. For example, consider the following
+ message:
+
+ Content-type: message/external-body; access-
+ type=local-file;
+ name=/u/nsb/Me.gif
+
+ Content-type: image/gif
+
+ THIS IS NOT REALLY THE BODY!
+
+ The area at the end, which might be called the "phantom
+ body", is ignored for most external-body messages. However,
+ it may be used to contain auxilliary information for some
+
+
+
+ Borenstein & Freed [Page 40]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ such messages, as indeed it is when the access-type is
+ "mail-server". Of the access-types defined by this
+ document, the phantom body is used only when the access-type
+ is "mail-server". In all other cases, the phantom body is
+ ignored.
+
+ The only always-mandatory parameter for message/external-
+ body is "access-type"; all of the other parameters may be
+ mandatory or optional depending on the value of access-type.
+
+ ACCESS-TYPE -- One or more case-insensitive words,
+ comma-separated, indicating supported access
+ mechanisms by which the file or data may be
+ obtained. Values include, but are not limited to,
+ "FTP", "ANON-FTP", "TFTP", "AFS", "LOCAL-FILE",
+ and "MAIL-SERVER". Future values, except for
+ experimental values beginning with "X-", must be
+ registered with IANA, as described in Appendix F .
+
+ In addition, the following two parameters are optional for
+ ALL access-types:
+
+ EXPIRATION -- The date (in the RFC 822 "date-time"
+ syntax, as extended by RFC 1123 to permit 4 digits
+ in the date field) after which the existence of
+ the external data is not guaranteed.
+
+ SIZE -- The size (in octets) of the data. The
+ intent of this parameter is to help the recipient
+ decide whether or not to expend the necessary
+ resources to retrieve the external data.
+
+ PERMISSION -- A field that indicates whether or
+ not it is expected that clients might also attempt
+ to overwrite the data. By default, or if
+ permission is "read", the assumption is that they
+ are not, and that if the data is retrieved once,
+ it is never needed again. If PERMISSION is "read-
+ write", this assumption is invalid, and any local
+ copy must be considered no more than a cache.
+ "Read" and "Read-write" are the only defined
+ values of permission.
+
+ The precise semantics of the access-types defined here are
+ described in the sections that follow.
+
+ 7.3.3.1 The "ftp" and "tftp" access-types
+
+ An access-type of FTP or TFTP indicates that the message
+ body is accessible as a file using the FTP [RFC-959] or TFTP
+ [RFC-783] protocols, respectively. For these access-types,
+ the following additional parameters are mandatory:
+
+
+
+
+
+ Borenstein & Freed [Page 41]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ NAME -- The name of the file that contains the
+ actual body data.
+
+ SITE -- A machine from which the file may be
+ obtained, using the given protocol
+
+ Before the data is retrieved, using these protocols, the
+ user will generally need to be asked to provide a login id
+ and a password for the machine named by the site parameter.
+
+ In addition, the following optional parameters may also
+ appear when the access-type is FTP or ANON-FTP:
+
+ DIRECTORY -- A directory from which the data named
+ by NAME should be retrieved.
+
+ MODE -- A transfer mode for retrieving the
+ information, e.g. "image".
+
+ 7.3.3.2 The "anon-ftp" access-type
+
+ The "anon-ftp" access-type is identical to the "ftp" access
+ type, except that the user need not be asked to provide a
+ name and password for the specified site. Instead, the ftp
+ protocol will be used with login "anonymous" and a password
+ that corresponds to the user's email address.
+
+ 7.3.3.3 The "local-file" and "afs" access-types
+
+ An access-type of "local-file" indicates that the actual
+ body is accessible as a file on the local machine. An
+ access-type of "afs" indicates that the file is accessible
+ via the global AFS file system. In both cases, only a
+ single parameter is required:
+
+ NAME -- The name of the file that contains the
+ actual body data.
+
+ The following optional parameter may be used to describe the
+ locality of reference for the data, that is, the site or
+ sites at which the file is expected to be visible:
+
+ SITE -- A domain specifier for a machine or set of
+ machines that are known to have access to the data
+ file. Asterisks may be used for wildcard matching
+ to a part of a domain name, such as
+ "*.bellcore.com", to indicate a set of machines on
+ which the data should be directly visible, while a
+ single asterisk may be used to indicate a file
+ that is expected to be universally available,
+ e.g., via a global file system.
+
+ 7.3.3.4 The "mail-server" access-type
+
+
+
+
+ Borenstein & Freed [Page 42]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ The "mail-server" access-type indicates that the actual body
+ is available from a mail server. The mandatory parameter
+ for this access-type is:
+
+ SERVER -- The email address of the mail server
+ from which the actual body data can be obtained.
+
+ Because mail servers accept a variety of syntax, some of
+ which is multiline, the full command to be sent to a mail
+ server is not included as a parameter on the content-type
+ line. Instead, it may be provided as the "phantom body"
+ when the content-type is message/external-body and the
+ access-type is mail-server.
+
+ Note that MIME does not define a mail server syntax.
+ Rather, it allows the inclusion of arbitrary mail server
+ commands in the phantom body. Implementations should
+ include the phantom body in the body of the message it sends
+ to the mail server address to retrieve the relevant data.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 43]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.3.3.5 Examples and Further Explanations
+
+ With the emerging possibility of very wide-area file
+ systems, it becomes very hard to know in advance the set of
+ machines where a file will and will not be accessible
+ directly from the file system. Therefore it may make sense
+ to provide both a file name, to be tried directly, and the
+ name of one or more sites from which the file is known to be
+ accessible. An implementation can try to retrieve remote
+ files using FTP or any other protocol, using anonymous file
+ retrieval or prompting the user for the necessary name and
+ password. If an external body is accessible via multiple
+ mechanisms, the sender may include multiple parts of type
+ message/external-body within an entity of type
+ multipart/alternative.
+
+ However, the external-body mechanism is not intended to be
+ limited to file retrieval, as shown by the mail-server
+ access-type. Beyond this, one can imagine, for example,
+ using a video server for external references to video clips.
+
+ If an entity is of type "message/external-body", then the
+ body of the entity will contain the header fields of the
+ encapsulated message. The body itself is to be found in the
+ external location. This means that if the body of the
+ "message/external-body" message contains two consecutive
+ CRLFs, everything after those pairs is NOT part of the
+ message itself. For most message/external-body messages,
+ this trailing area must simply be ignored. However, it is a
+ convenient place for additional data that cannot be included
+ in the content-type header field. In particular, if the
+ "access-type" value is "mail-server", then the trailing area
+ must contain commands to be sent to the mail server at the
+ address given by NAME@SITE, where NAME and SITE are the
+ values of the NAME and SITE parameters, respectively.
+
+ The embedded message header fields which appear in the body
+ of the message/external-body data can be used to declare the
+ Content-type of the external body. Thus a complete
+ message/external-body message, referring to a document in
+ PostScript format, might look like this:
+
+ From: Whomever
+ Subject: whatever
+ MIME-Version: 1.0
+ Message-ID: id1@host.com
+ Content-Type: multipart/alternative; boundary=42
+
+
+ --42
+ Content-Type: message/external-body;
+ name="BodyFormats.ps";
+
+
+
+
+
+ Borenstein & Freed [Page 44]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ site="thumper.bellcore.com";
+ access-type=ANON-FTP;
+ directory="pub";
+ mode="image";
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+
+ --42
+ Content-Type: message/external-body;
+ name="/u/nsb/writing/rfcs/RFC-XXXX.ps";
+ site="thumper.bellcore.com";
+ access-type=AFS
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+
+ --42
+ Content-Type: message/external-body;
+ access-type=mail-server
+ server="listserv@bogus.bitnet";
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+
+ get rfc-xxxx doc
+
+ --42--
+
+ Like the message/partial type, the message/external-body
+ type is intended to be transparent, that is, to convey the
+ data type in the external body rather than to convey a
+ message with a body of that type. Thus the headers on the
+ outer and inner parts must be merged using the same rules as
+ for message/partial. In particular, this means that the
+ Content-type header is overridden, but the From and Subject
+ headers are preserved.
+
+ Note that since the external bodies are not transported as
+ mail, they need not conform to the 7-bit and line length
+ requirements, but might in fact be binary files. Thus a
+ Content-Transfer-Encoding is not generally necessary, though
+ it is permitted.
+
+ Note that the body of a message of type "message/external-
+ body" is governed by the basic syntax for an RFC 822
+ message. In particular, anything before the first
+ consecutive pair of CRLFs is header information, while
+ anything after it is body information, which is ignored for
+ most access-types.
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 45]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.4 The Application Content-Type
+
+ The "application" Content-Type is to be used for data which
+ do not fit in any of the other categories, and particularly
+ for data to be processed by mail-based uses of application
+ programs. This is information which must be processed by an
+ application before it is viewable or usable to a user.
+ Expected uses for Content-Type application include mail-
+ based file transfer, spreadsheets, data for mail-based
+ scheduling systems, and languages for "active"
+ (computational) email. (The latter, in particular, can pose
+ security problems which should be understood by
+ implementors, and are considered in detail in the discussion
+ of the application/PostScript content-type.)
+
+ For example, a meeting scheduler might define a standard
+ representation for information about proposed meeting dates.
+ An intelligent user agent would use this information to
+ conduct a dialog with the user, and might then send further
+ mail based on that dialog. More generally, there have been
+ several "active" messaging languages developed in which
+ programs in a suitably specialized language are sent through
+ the mail and automatically run in the recipient's
+ environment.
+
+ Such applications may be defined as subtypes of the
+ "application" Content-Type. This document defines three
+ subtypes: octet-stream, ODA, and PostScript.
+
+ In general, the subtype of application will often be the
+ name of the application for which the data are intended.
+ This does not mean, however, that any application program
+ name may be used freely as a subtype of application. Such
+ usages must be registered with IANA, as described in
+ Appendix F.
+
+ 7.4.1 The Application/Octet-Stream (primary) subtype
+
+ The primary subtype of application, "octet-stream", may be
+ used to indicate that a body contains binary data. The set
+ of possible parameters includes, but is not limited to:
+
+ NAME -- a suggested name for the binary data if
+ stored as a file.
+
+ TYPE -- the general type or category of binary
+ data. This is intended as information for the
+ human recipient rather than for any automatic
+ processing.
+
+ CONVERSIONS -- the set of operations that have
+ been performed on the data before putting it in
+ the mail (and before any Content-Transfer-Encoding
+ that might have been applied). If multiple
+
+
+
+ Borenstein & Freed [Page 46]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ conversions have occurred, they must be separated
+ by commas and specified in the order they were
+ applied -- that is, the leftmost conversion must
+ have occurred first, and conversions are undone
+ from right to left. Note that NO conversion
+ values are defined by this document. Any
+ conversion values that that do not begin with "X-"
+ must be preceded by a published specification and
+ by registration with IANA, as described in
+ Appendix F.
+
+ PADDING -- the number of bits of padding that were
+ appended to the bitstream comprising the actual
+ contents to produce the enclosed byte-oriented
+ data. This is useful for enclosing a bitstream in
+ a body when the total number of bits is not a
+ multiple of the byte size.
+
+ The values for these attributes are left undefined at
+ present, but may require specification in the future. An
+ example of a common (though UNIX-specific) usage might be:
+
+ Content-Type: application/octet-stream;
+ name=foo.tar.Z; type=tar;
+ conversions="x-encrypt,x-compress"
+
+ However, it should be noted that the use of such conversions
+ is explicitly discouraged due to a lack of portability and
+ standardization. The use of uuencode is particularly
+ discouraged, in favor of the Content-Transfer-Encoding
+ mechanism, which is both more standardized and more portable
+ across mail boundaries.
+
+ The recommended action for an implementation that receives
+ application/octet-stream mail is to simply offer to put the
+ data in a file, with any Content-Transfer-Encoding undone,
+ or perhaps to use it as input to a user-specified process.
+
+ To reduce the danger of transmitting rogue programs through
+ the mail, it is strongly recommended that implementations
+ NOT implement a path-search mechanism whereby an arbitrary
+ program named in the Content-Type parameter (e.g., an
+ "interpreter=" parameter) is found and executed using the
+ mail body as input.
+
+ 7.4.2 The Application/PostScript subtype
+
+ A Content-Type of "application/postscript" indicates a
+ PostScript program. The language is defined in
+ [POSTSCRIPT]. It is recommended that Postscript as sent
+ through email should use Postscript document structuring
+ conventions if at all possible, and correctly.
+
+
+
+
+
+ Borenstein & Freed [Page 47]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ The execution of general-purpose PostScript interpreters
+ entails serious security risks, and implementors are
+ discouraged from simply sending PostScript email bodies to
+ "off-the-shelf" interpreters. While it is usually safe to
+ send PostScript to a printer, where the potential for harm
+ is greatly constrained, implementors should consider all of
+ the following before they add interactive display of
+ PostScript bodies to their mail readers.
+
+ The remainder of this section outlines some, though probably
+ not all, of the possible problems with sending PostScript
+ through the mail.
+
+ Dangerous operations in the PostScript language include, but
+ may not be limited to, the PostScript operators deletefile,
+ renamefile, filenameforall, and file. File is only
+ dangerous when applied to something other than standard
+ input or output. Implementations may also define additional
+ nonstandard file operators; these may also pose a threat to
+ security. Filenameforall, the wildcard file search
+ operator, may appear at first glance to be harmless. Note,
+ however, that this operator has the potential to reveal
+ information about what files the recipient has access to,
+ and this information may itself be sensitive. Message
+ senders should avoid the use of potentially dangerous file
+ operators, since these operators are quite likely to be
+ unavailable in secure PostScript implementations. Message-
+ receiving and -displaying software should either completely
+ disable all potentially dangerous file operators or take
+ special care not to delegate any special authority to their
+ operation. These operators should be viewed as being done by
+ an outside agency when interpreting PostScript documents.
+ Such disabling and/or checking should be done completely
+ outside of the reach of the PostScript language itself; care
+ should be taken to insure that no method exists for
+ reenabling full-function versions of these operators.
+
+ The PostScript language provides facilities for exiting the
+ normal interpreter, or server, loop. Changes made in this
+ "outer" environment are customarily retained across
+ documents, and may in some cases be retained semipermanently
+ in nonvolatile memory. The operators associated with exiting
+ the interpreter loop have the potential to interfere with
+ subsequent document processing. As such, their unrestrained
+ use constitutes a threat of service denial. PostScript
+ operators that exit the interpreter loop include, but may
+ not be limited to, the exitserver and startjob operators.
+ Message-sending software should not generate PostScript that
+ depends on exiting the interpreter loop to operate. The
+ ability to exit will probably be unavailable in secure
+ PostScript implementations. Message-receiving and
+ -displaying software should, if possible, disable the
+ ability to make retained changes to the PostScript
+ environment. Eliminate the startjob and exitserver commands.
+
+
+
+ Borenstein & Freed [Page 48]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ If these commands cannot be eliminated, at least set the
+ password associated with them to a hard-to-guess value.
+
+ PostScript provides operators for setting system-wide and
+ device-specific parameters. These parameter settings may be
+ retained across jobs and may potentially pose a threat to
+ the correct operation of the interpreter. The PostScript
+ operators that set system and device parameters include, but
+ may not be limited to, the setsystemparams and setdevparams
+ operators. Message-sending software should not generate
+ PostScript that depends on the setting of system or device
+ parameters to operate correctly. The ability to set these
+ parameters will probably be unavailable in secure PostScript
+ implementations. Message-receiving and -displaying software
+ should, if possible, disable the ability to change system
+ and device parameters. If these operators cannot be
+ disabled, at least set the password associated with them to
+ a hard-to-guess value.
+
+ Some PostScript implementations provide nonstandard
+ facilities for the direct loading and execution of machine
+ code. Such facilities are quite obviously open to
+ substantial abuse. Message-sending software should not
+ make use of such features. Besides being totally hardware-
+ specific, they are also likely to be unavailable in secure
+ implementations of PostScript. Message-receiving and
+ -displaying software should not allow such operators to be
+ used if they exist.
+
+ PostScript is an extensible language, and many, if not most,
+ implementations of it provide a number of their own
+ extensions. This document does not deal with such extensions
+ explicitly since they constitute an unknown factor.
+ Message-sending software should not make use of nonstandard
+ extensions; they are likely to be missing from some
+ implementations. Message-receiving and -displaying software
+ should make sure that any nonstandard PostScript operators
+ are secure and don't present any kind of threat.
+
+ It is possible to write PostScript that consumes huge
+ amounts of various system resources. It is also possible to
+ write PostScript programs that loop infinitely. Both types
+ of programs have the potential to cause damage if sent to
+ unsuspecting recipients. Message-sending software should
+ avoid the construction and dissemination of such programs,
+ which is antisocial. Message-receiving and -displaying
+ software should provide appropriate mechanisms to abort
+ processing of a document after a reasonable amount of time
+ has elapsed. In addition, PostScript interpreters should be
+ limited to the consumption of only a reasonable amount of
+ any given system resource.
+
+ Finally, bugs may exist in some PostScript interpreters
+ which could possibly be exploited to gain unauthorized
+
+
+
+ Borenstein & Freed [Page 49]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ access to a recipient's system. Apart from noting this
+ possibility, there is no specific action to take to prevent
+ this, apart from the timely correction of such bugs if any
+ are found.
+
+ 7.4.3 The Application/ODA subtype
+
+ The "ODA" subtype of application is used to indicate that a
+ body contains information encoded according to the Office
+ Document Architecture [ODA] standards, using the ODIF
+ representation format. For application/oda, the Content-
+ Type line should also specify an attribute/value pair that
+ indicates the document application profile (DAP), using the
+ key word "profile". Thus an appropriate header field might
+ look like this:
+
+ Content-Type: application/oda; profile=Q112
+
+ Consult the ODA standard [ODA] for further information.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 50]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 7.5 The Image Content-Type
+
+ A Content-Type of "image" indicates that the bodycontains an
+ image. The subtype names the specific image format. These
+ names are case insensitive. Two initial subtypes are "jpeg"
+ for the JPEG format, JFIF encoding, and "gif" for GIF format
+ [GIF].
+
+ The list of image subtypes given here is neither exclusive
+ nor exhaustive, and is expected to grow as more types are
+ registered with IANA, as described in Appendix F.
+
+ 7.6 The Audio Content-Type
+
+ A Content-Type of "audio" indicates that the body contains
+ audio data. Although there is not yet a consensus on an
+ "ideal" audio format for use with computers, there is a
+ pressing need for a format capable of providing
+ interoperable behavior.
+
+ The initial subtype of "basic" is specified to meet this
+ requirement by providing an absolutely minimal lowest common
+ denominator audio format. It is expected that richer
+ formats for higher quality and/or lower bandwidth audio will
+ be defined by a later document.
+
+ The content of the "audio/basic" subtype is audio encoded
+ using 8-bit ISDN u-law [PCM]. When this subtype is present,
+ a sample rate of 8000 Hz and a single channel is assumed.
+
+ 7.7 The Video Content-Type
+
+ A Content-Type of "video" indicates that the body contains a
+ time-varying-picture image, possibly with color and
+ coordinated sound. The term "video" is used extremely
+ generically, rather than with reference to any particular
+ technology or format, and is not meant to preclude subtypes
+ such as animated drawings encoded compactly. The subtype
+ "mpeg" refers to video coded according to the MPEG standard
+ [MPEG].
+
+ Note that although in general this document strongly
+ discourages the mixing of multiple media in a single body,
+ it is recognized that many so-called "video" formats include
+ a representation for synchronized audio, and this is
+ explicitly permitted for subtypes of "video".
+
+ 7.8 Experimental Content-Type Values
+
+ A Content-Type value beginning with the characters "X-" is a
+ private value, to be used by consenting mail systems by
+ mutual agreement. Any format without a rigorous and public
+ definition must be named with an "X-" prefix, and publicly
+ specified values shall never begin with "X-". (Older
+
+
+
+ Borenstein & Freed [Page 51]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ versions of the widely-used Andrew system use the "X-BE2"
+ name, so new systems should probably choose a different
+ name.)
+
+ In general, the use of "X-" top-level types is strongly
+ discouraged. Implementors should invent subtypes of the
+ existing types whenever possible. The invention of new
+ types is intended to be restricted primarily to the
+ development of new media types for email, such as digital
+ odors or holography, and not for new data formats in
+ general. In many cases, a subtype of application will be
+ more appropriate than a new top-level type.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 52]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Summary
+
+ Using the MIME-Version, Content-Type, and Content-Transfer-
+ Encoding header fields, it is possible to include, in a
+ standardized way, arbitrary types of data objects with RFC
+ 822 conformant mail messages. No restrictions imposed by
+ either RFC 821 or RFC 822 are violated, and care has been
+ taken to avoid problems caused by additional restrictions
+ imposed by the characteristics of some Internet mail
+ transport mechanisms (see Appendix B). The "multipart" and
+ "message" Content-Types allow mixing and hierarchical
+ structuring of objects of different types in a single
+ message. Further Content-Types provide a standardized
+ mechanism for tagging messages or body parts as audio,
+ image, or several other kinds of data. A distinguished
+ parameter syntax allows further specification of data format
+ details, particularly the specification of alternate
+ character sets. Additional optional header fields provide
+ mechanisms for certain extensions deemed desirable by many
+ implementors. Finally, a number of useful Content-Types are
+ defined for general use by consenting user agents, notably
+ text/richtext, message/partial, and message/external-body.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 53]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Acknowledgements
+
+ This document is the result of the collective effort of a
+ large number of people, at several IETF meetings, on the
+ IETF-SMTP and IETF-822 mailing lists, and elsewhere.
+ Although any enumeration seems doomed to suffer from
+ egregious omissions, the following are among the many
+ contributors to this effort:
+
+ Harald Tveit Alvestrand Timo Lehtinen
+ Randall Atkinson John R. MacMillan
+ Philippe Brandon Rick McGowan
+ Kevin Carosso Leo Mclaughlin
+ Uhhyung Choi Goli Montaser-Kohsari
+ Cristian Constantinof Keith Moore
+ Mark Crispin Tom Moore
+ Dave Crocker Erik Naggum
+ Terry Crowley Mark Needleman
+ Walt Daniels John Noerenberg
+ Frank Dawson Mats Ohrman
+ Hitoshi Doi Julian Onions
+ Kevin Donnelly Michael Patton
+ Keith Edwards David J. Pepper
+ Chris Eich Blake C. Ramsdell
+ Johnny Eriksson Luc Rooijakkers
+ Craig Everhart Marshall T. Rose
+ Patrik Faeltstroem Jonathan Rosenberg
+ Erik E. Fair Jan Rynning
+ Roger Fajman Harri Salminen
+ Alain Fontaine Michael Sanderson
+ James M. Galvin Masahiro Sekiguchi
+ Philip Gladstone Mark Sherman
+ Thomas Gordon Keld Simonsen
+ Phill Gross Bob Smart
+ James Hamilton Peter Speck
+ Steve Hardcastle-Kille Henry Spencer
+ David Herron Einar Stefferud
+ Bruce Howard Michael Stein
+ Bill Janssen Klaus Steinberger
+ Olle Jaernefors Peter Svanberg
+ Risto Kankkunen James Thompson
+ Phil Karn Steve Uhler
+ Alan Katz Stuart Vance
+ Tim Kehres Erik van der Poel
+ Neil Katin Guido van Rossum
+ Kyuho Kim Peter Vanderbilt
+ Anders Klemets Greg Vaudreuil
+ John Klensin Ed Vielmetti
+ Valdis Kletniek Ryan Waldron
+ Jim Knowles Wally Wedel
+ Stev Knowles Sven-Ove Westberg
+ Bob Kummerfeld Brian Wideen
+
+
+
+
+
+ Borenstein & Freed [Page 54]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Pekka Kytolaakso John Wobus
+ Stellan Lagerstr.m Glenn Wright
+ Vincent Lau Rayan Zachariassen
+ Donald Lindsay David Zimmerman
+ The authors apologize for any omissions from this list,
+ which are certainly unintentional.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 55]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix A -- Minimal MIME-Conformance
+
+ The mechanisms described in this document are open-ended.
+ It is definitely not expected that all implementations will
+ support all of the Content-Types described, nor that they
+ will all share the same extensions. In order to promote
+ interoperability, however, it is useful to define the
+ concept of "MIME-conformance" to define a certain level of
+ implementation that allows the useful interworking of
+ messages with content that differs from US ASCII text. In
+ this section, we specify the requirements for such
+ conformance.
+
+ A mail user agent that is MIME-conformant MUST:
+
+ 1. Always generate a "MIME-Version: 1.0" header
+ field.
+
+ 2. Recognize the Content-Transfer-Encoding header
+ field, and decode all received data encoded with
+ either the quoted-printable or base64
+ implementations. Encode any data sent that is
+ not in seven-bit mail-ready representation using
+ one of these transformations and include the
+ appropriate Content-Transfer-Encoding header
+ field, unless the underlying transport mechanism
+ supports non-seven-bit data, as SMTP does not.
+
+ 3. Recognize and interpret the Content-Type
+ header field, and avoid showing users raw data
+ with a Content-Type field other than text. Be
+ able to send at least text/plain messages, with
+ the character set specified as a parameter if it
+ is not US-ASCII.
+
+ 4. Explicitly handle the following Content-Type
+ values, to at least the following extents:
+
+ Text:
+ -- Recognize and display "text" mail
+ with the character set "US-ASCII."
+ -- Recognize other character sets at
+ least to the extent of being able
+ to inform the user about what
+ character set the message uses.
+ -- Recognize the "ISO-8859-*" character
+ sets to the extent of being able to
+ display those characters that are
+ common to ISO-8859-* and US-ASCII,
+ namely all characters represented
+ by octet values 0-127.
+ -- For unrecognized subtypes, show or
+ offer to show the user the "raw"
+ version of the data. An ability at
+
+
+
+ Borenstein & Freed [Page 56]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ least to convert "text/richtext" to
+ plain text, as shown in Appendix D,
+ is encouraged, but not required for
+ conformance.
+ Message:
+ --Recognize and display at least the
+ primary (822) encapsulation.
+ Multipart:
+ -- Recognize the primary (mixed)
+ subtype. Display all relevant
+ information on the message level
+ and the body part header level and
+ then display or offer to display
+ each of the body parts
+ individually.
+ -- Recognize the "alternative" subtype,
+ and avoid showing the user
+ redundant parts of
+ multipart/alternative mail.
+ -- Treat any unrecognized subtypes as if
+ they were "mixed".
+ Application:
+ -- Offer the ability to remove either of
+ the two types of Content-Transfer-
+ Encoding defined in this document
+ and put the resulting information
+ in a user file.
+
+ 5. Upon encountering any unrecognized Content-
+ Type, an implementation must treat it as if it had
+ a Content-Type of "application/octet-stream" with
+ no parameter sub-arguments. How such data are
+ handled is up to an implementation, but likely
+ options for handling such unrecognized data
+ include offering the user to write it into a file
+ (decoded from its mail transport format) or
+ offering the user to name a program to which the
+ decoded data should be passed as input.
+ Unrecognized predefined types, which in a MIME-
+ conformant mailer might still include audio,
+ image, or video, should also be treated in this
+ way.
+
+ A user agent that meets the above conditions is said to be
+ MIME-conformant. The meaning of this phrase is that it is
+ assumed to be "safe" to send virtually any kind of
+ properly-marked data to users of such mail systems, because
+ such systems will at least be able to treat the data as
+ undifferentiated binary, and will not simply splash it onto
+ the screen of unsuspecting users. There is another sense
+ in which it is always "safe" to send data in a format that
+ is MIME-conformant, which is that such data will not break
+ or be broken by any known systems that are conformant with
+ RFC 821 and RFC 822. User agents that are MIME-conformant
+
+
+
+ Borenstein & Freed [Page 57]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ have the additional guarantee that the user will not be
+ shown data that were never intended to be viewed as text.
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
+
+ Borenstein & Freed [Page 58]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix B -- General Guidelines For Sending Email Data
+
+ Internet email is not a perfect, homogeneous system. Mail
+ may become corrupted at several stages in its travel to a
+ final destination. Specifically, email sent throughout the
+ Internet may travel across many networking technologies.
+ Many networking and mail technologies do not support the
+ full functionality possible in the SMTP transport
+ environment. Mail traversing these systems is likely to be
+ modified in such a way that it can be transported.
+
+ There exist many widely-deployed non-conformant MTAs in the
+ Internet. These MTAs, speaking the SMTP protocol, alter
+ messages on the fly to take advantage of the internal data
+ structure of the hosts they are implemented on, or are just
+ plain broken.
+
+ The following guidelines may be useful to anyone devising a
+ data format (Content-Type) that will survive the widest
+ range of networking technologies and known broken MTAs
+ unscathed. Note that anything encoded in the base64
+ encoding will satisfy these rules, but that some well-known
+ mechanisms, notably the UNIX uuencode facility, will not.
+ Note also that anything encoded in the Quoted-Printable
+ encoding will survive most gateways intact, but possibly not
+ some gateways to systems that use the EBCDIC character set.
+
+ (1) Under some circumstances the encoding used for
+ data may change as part of normal gateway or user
+ agent operation. In particular, conversion from
+ base64 to quoted-printable and vice versa may be
+ necessary. This may result in the confusion of
+ CRLF sequences with line breaks in text body
+ parts. As such, the persistence of CRLF as
+ something other than a line break should not be
+ relied on.
+
+ (2) Many systems may elect to represent and store
+ text data using local newline conventions. Local
+ newline conventions may not match the RFC822 CRLF
+ convention -- systems are known that use plain CR,
+ plain LF, CRLF, or counted records. The result is
+ that isolated CR and LF characters are not well
+ tolerated in general; they may be lost or
+ converted to delimiters on some systems, and hence
+ should not be relied on.
+
+ (3) TAB (HT) characters may be misinterpreted or
+ may be automatically converted to variable numbers
+ of spaces. This is unavoidable in some
+ environments, notably those not based on the ASCII
+ character set. Such conversion is STRONGLY
+ DISCOURAGED, but it may occur, and mail formats
+ should not rely on the persistence of TAB (HT)
+
+
+
+ Borenstein & Freed [Page 59]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ characters.
+
+ (4) Lines longer than 76 characters may be wrapped
+ or truncated in some environments. Line wrapping
+ and line truncation are STRONGLY DISCOURAGED, but
+ unavoidable in some cases. Applications which
+ require long lines should somehow differentiate
+ between soft and hard line breaks. (A simple way
+ to do this is to use the quoted-printable
+ encoding.)
+
+ (5) Trailing "white space" characters (SPACE, TAB
+ (HT)) on a line may be discarded by some transport
+ agents, while other transport agents may pad lines
+ with these characters so that all lines in a mail
+ file are of equal length. The persistence of
+ trailing white space, therefore, should not be
+ relied on.
+
+ (6) Many mail domains use variations on the ASCII
+ character set, or use character sets such as
+ EBCDIC which contain most but not all of the US-
+ ASCII characters. The correct translation of
+ characters not in the "invariant" set cannot be
+ depended on across character converting gateways.
+ For example, this situation is a problem when
+ sending uuencoded information across BITNET, an
+ EBCDIC system. Similar problems can occur without
+ crossing a gateway, since many Internet hosts use
+ character sets other than ASCII internally. The
+ definition of Printable Strings in X.400 adds
+ further restrictions in certain special cases. In
+ particular, the only characters that are known to
+ be consistent across all gateways are the 73
+ characters that correspond to the upper and lower
+ case letters A-Z and a-z, the 10 digits 0-9, and
+ the following eleven special characters:
+
+ "'" (ASCII code 39)
+ "(" (ASCII code 40)
+ ")" (ASCII code 41)
+ "+" (ASCII code 43)
+ "," (ASCII code 44)
+ "-" (ASCII code 45)
+ "." (ASCII code 46)
+ "/" (ASCII code 47)
+ ":" (ASCII code 58)
+ "=" (ASCII code 61)
+ "?" (ASCII code 63)
+
+ A maximally portable mail representation, such as
+ the base64 encoding, will confine itself to
+ relatively short lines of text in which the only
+ meaningful characters are taken from this set of
+
+
+
+ Borenstein & Freed [Page 60]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ 73 characters.
+
+ Please note that the above list is NOT a list of recommended
+ practices for MTAs. RFC 821 MTAs are prohibited from
+ altering the character of white space or wrapping long
+ lines. These BAD and illegal practices are known to occur
+ on established networks, and implementions should be robust
+ in dealing with the bad effects they can cause.
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
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+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 61]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix C -- A Complex Multipart Example
+
+ What follows is the outline of a complex multipart message.
+ This message has five parts to be displayed serially: two
+ introductory plain text parts, an embedded multipart
+ message, a richtext part, and a closing encapsulated text
+ message in a non-ASCII character set. The embedded
+ multipart message has two parts to be displayed in parallel,
+ a picture and an audio fragment.
+
+ MIME-Version: 1.0
+ From: Nathaniel Borenstein <nsb@bellcore.com>
+ Subject: A multipart example
+ Content-Type: multipart/mixed;
+ boundary=unique-boundary-1
+
+ This is the preamble area of a multipart message.
+ Mail readers that understand multipart format
+ should ignore this preamble.
+ If you are reading this text, you might want to
+ consider changing to a mail reader that understands
+ how to properly display multipart messages.
+ --unique-boundary-1
+
+ ...Some text appears here...
+ [Note that the preceding blank line means
+ no header fields were given and this is text,
+ with charset US ASCII. It could have been
+ done with explicit typing as in the next part.]
+
+ --unique-boundary-1
+ Content-type: text/plain; charset=US-ASCII
+
+ This could have been part of the previous part,
+ but illustrates explicit versus implicit
+ typing of body parts.
+
+ --unique-boundary-1
+ Content-Type: multipart/parallel;
+ boundary=unique-boundary-2
+
+
+ --unique-boundary-2
+ Content-Type: audio/basic
+ Content-Transfer-Encoding: base64
+
+ ... base64-encoded 8000 Hz single-channel
+ u-law-format audio data goes here....
+
+ --unique-boundary-2
+ Content-Type: image/gif
+ Content-Transfer-Encoding: Base64
+
+
+
+
+
+ Borenstein & Freed [Page 62]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ ... base64-encoded image data goes here....
+
+ --unique-boundary-2--
+
+ --unique-boundary-1
+ Content-type: text/richtext
+
+ This is <bold><italic>richtext.</italic></bold>
+ <nl><nl>Isn't it
+ <bigger><bigger>cool?</bigger></bigger>
+
+ --unique-boundary-1
+ Content-Type: message/rfc822
+
+ From: (name in US-ASCII)
+ Subject: (subject in US-ASCII)
+ Content-Type: Text/plain; charset=ISO-8859-1
+ Content-Transfer-Encoding: Quoted-printable
+
+ ... Additional text in ISO-8859-1 goes here ...
+
+ --unique-boundary-1--
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
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+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 63]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix D -- A Simple Richtext-to-Text Translator in C
+
+ One of the major goals in the design of the richtext subtype
+ of the text Content-Type is to make formatted text so simple
+ that even text-only mailers will implement richtext-to-
+ plain-text translators, thus increasing the likelihood that
+ multifont text will become "safe" to use very widely. To
+ demonstrate this simplicity, what follows is an extremely
+ simple 44-line C program that converts richtext input into
+ plain text output:
+
+ #include <stdio.h>
+ #include <ctype.h>
+ main() {
+ int c, i;
+ char token[50];
+
+ while((c = getc(stdin)) != EOF) {
+ if (c == '<') {
+ for (i=0; (i<49 && (c = getc(stdin)) != '>'
+ && c != EOF); ++i) {
+ token[i] = isupper(c) ? tolower(c) : c;
+ }
+ if (c == EOF) break;
+ if (c != '>') while ((c = getc(stdin)) !=
+ '>'
+ && c != EOF) {;}
+ if (c == EOF) break;
+ token[i] = '\0';
+ if (!strcmp(token, "lt")) {
+ putc('<', stdout);
+ } else if (!strcmp(token, "nl")) {
+ putc('\n', stdout);
+ } else if (!strcmp(token, "/paragraph")) {
+ fputs("\n\n", stdout);
+ } else if (!strcmp(token, "comment")) {
+ int commct=1;
+ while (commct > 0) {
+ while ((c = getc(stdin)) != '<'
+ && c != EOF) ;
+ if (c == EOF) break;
+ for (i=0; (c = getc(stdin)) != '>'
+ && c != EOF; ++i) {
+ token[i] = isupper(c) ?
+ tolower(c) : c;
+ }
+ if (c== EOF) break;
+ token[i] = NULL;
+ if (!strcmp(token, "/comment")) --
+ commct;
+ if (!strcmp(token, "comment"))
+ ++commct;
+
+
+
+
+
+ Borenstein & Freed [Page 64]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ }
+ } /* Ignore all other tokens */
+ } else if (c != '\n') putc(c, stdout);
+ }
+ putc('\n', stdout); /* for good measure */
+ }
+ It should be noted that one can do considerably better than
+ this in displaying richtext data on a dumb terminal. In
+ particular, one can replace font information such as "bold"
+ with textual emphasis (like *this* or _T_H_I_S_). One can
+ also properly handle the richtext formatting commands
+ regarding indentation, justification, and others. However,
+ the above program is all that is necessary in order to
+ present richtext on a dumb terminal.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
+
+
+
+
+
+ Borenstein & Freed [Page 65]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix E -- Collected Grammar
+
+ This appendix contains the complete BNF grammar for all the
+ syntax specified by this document.
+
+ By itself, however, this grammar is incomplete. It refers
+ to several entities that are defined by RFC 822. Rather
+ than reproduce those definitions here, and risk
+ unintentional differences between the two, this document
+ simply refers the reader to RFC 822 for the remaining
+ definitions. Wherever a term is undefined, it refers to the
+ RFC 822 definition.
+
+ attribute := token
+
+ body-part = <"message" as defined in RFC 822,
+ with all header fields optional, and with the
+ specified delimiter not occurring anywhere in
+ the message body, either on a line by itself
+ or as a substring anywhere.>
+
+ boundary := 0*69<bchars> bcharsnospace
+
+ bchars := bcharsnospace / " "
+
+ bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /
+ "_"
+ / "," / "-" / "." / "/" / ":" / "=" / "?"
+
+ close-delimiter := delimiter "--"
+
+ Content-Description := *text
+
+ Content-ID := msg-id
+
+ Content-Transfer-Encoding := "BASE64" / "QUOTED-
+ PRINTABLE" /
+ "8BIT" / "7BIT" /
+ "BINARY" / x-token
+
+ Content-Type := type "/" subtype *[";" parameter]
+
+ delimiter := CRLF "--" boundary ; taken from Content-Type
+ field.
+ ; when content-type is
+ multipart
+ ; There should be no space
+ ; between "--" and boundary.
+
+ encapsulation := delimiter CRLF body-part
+
+ epilogue := *text ; to be ignored upon
+ receipt.
+
+
+
+
+ Borenstein & Freed [Page 66]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ MIME-Version := 1*text
+
+ multipart-body := preamble 1*encapsulation close-delimiter
+ epilogue
+
+ parameter := attribute "=" value
+
+ preamble := *text ; to be ignored upon
+ receipt.
+
+ subtype := token
+
+ token := 1*<any CHAR except SPACE, CTLs, or tspecials>
+
+ tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in
+ / "," / ";" / ":" / "\" / <"> ; quoted-string,
+ / "/" / "[" / "]" / "?" / "." ; to use within
+ / "=" ; parameter values
+
+
+ type := "application" / "audio" ; case-
+ insensitive
+ / "image" / "message"
+ / "multipart" / "text"
+ / "video" / x-token
+
+ value := token / quoted-string
+
+ x-token := <The two characters "X-" followed, with no
+ intervening white space, by any token>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 67]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix F -- IANA Registration Procedures
+
+ MIME has been carefully designed to have extensible
+ mechanisms, and it is expected that the set of content-
+ type/subtype pairs and their associated parameters will grow
+ significantly with time. Several other MIME fields, notably
+ character set names, access-type parameters for the
+ message/external-body type, conversions parameters for the
+ application type, and possibly even Content-Transfer-
+ Encoding values, are likely to have new values defined over
+ time. In order to ensure that the set of such values is
+ developed in an orderly, well-specified, and public manner,
+ MIME defines a registration process which uses the Internet
+ Assigned Numbers Authority (IANA) as a central registry for
+ such values.
+
+ In general, parameters in the content-type header field are
+ used to convey supplemental information for various content
+ types, and their use is defined when the content-type and
+ subtype are defined. New parameters should not be defined
+ as a way to introduce new functionality.
+
+ In order to simplify and standardize the registration
+ process, this appendix gives templates for the registration
+ of new values with IANA. Each of these is given in the form
+ of an email message template, to be filled in by the
+ registering party.
+
+ F.1 Registration of New Content-type/subtype Values
+
+ Note that MIME is generally expected to be extended by
+ subtypes. If a new fundamental top-level type is needed,
+ its specification should be published as an RFC or
+ submitted in a form suitable to become an RFC, and be
+ subject to the Internet standards process.
+
+ To: IANA@isi.edu
+ Subject: Registration of new MIME content-type/subtype
+
+ MIME type name:
+
+ (If the above is not an existing top-level MIME type,
+ please explain why an existing type cannot be used.)
+
+ MIME subtype name:
+
+ Required parameters:
+
+ Optional parameters:
+
+ Encoding considerations:
+
+ Security considerations:
+
+
+
+
+ Borenstein & Freed [Page 68]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Published specification:
+
+ (The published specification must be an Internet RFC or
+ RFC-to-be if a new top-level type is being defined, and
+ must be a publicly available specification in any
+ case.)
+
+ Person & email address to contact for further
+ information:
+ F.2 Registration of New Character Set Values
+
+ To: IANA@isi.edu
+ Subject: Registration of new MIME character set value
+
+ MIME character set name:
+
+ Published specification:
+
+ (The published specification must be an Internet RFC or
+ RFC-to-be or an international standard.)
+
+ Person & email address to contact for further
+ information:
+
+ F.3 Registration of New Access-type Values for
+ Message/external-body
+
+ To: IANA@isi.edu
+ Subject: Registration of new MIME Access-type for
+ Message/external-body content-type
+
+ MIME access-type name:
+
+ Required parameters:
+
+ Optional parameters:
+
+ Published specification:
+
+ (The published specification must be an Internet RFC or
+ RFC-to-be.)
+
+ Person & email address to contact for further
+ information:
+
+
+ F.4 Registration of New Conversions Values for Application
+
+ To: IANA@isi.edu
+ Subject: Registration of new MIME Conversions value
+ for Application content-type
+
+ MIME Conversions name:
+
+
+
+
+ Borenstein & Freed [Page 69]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Published specification:
+
+ (The published specification must be an Internet RFC or
+ RFC-to-be.)
+
+ Person & email address to contact for further
+ information:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 70]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix G -- Summary of the Seven Content-types
+
+ Content-type: text
+
+ Subtypes defined by this document: plain, richtext
+
+ Important Parameters: charset
+
+ Encoding notes: quoted-printable generally preferred if an
+ encoding is needed and the character set is mostly an
+ ASCII superset.
+
+ Security considerations: Rich text formats such as TeX and
+ Troff often contain mechanisms for executing arbitrary
+ commands or file system operations, and should not be
+ used automatically unless these security problems have
+ been addressed. Even plain text may contain control
+ characters that can be used to exploit the capabilities
+ of "intelligent" terminals and cause security
+ violations. User interfaces designed to run on such
+ terminals should be aware of and try to prevent such
+ problems.
+ ________________________________________________________________
+
+ Content-type: multipart
+
+ Subtypes defined by this document: mixed, alternative,
+ digest, parallel.
+
+ Important Parameters: boundary
+
+ Encoding notes: No content-transfer-encoding is permitted.
+
+ ________________________________________________________________
+
+ Content-type: message
+
+ Subtypes defined by this document: rfc822, partial,
+ external-body
+
+ Important Parameters: id, number, total
+
+ Encoding notes: No content-transfer-encoding is permitted.
+
+ ________________________________________________________________
+
+ Content-type: application
+
+ Subtypes defined by this document: octet-stream,
+ postscript, oda
+
+ Important Parameters: profile
+
+
+
+
+
+ Borenstein & Freed [Page 71]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Encoding notes: base64 generally preferred for octet-stream
+ or other unreadable subtypes.
+
+ Security considerations: This type is intended for the
+ transmission of data to be interpreted by locally-installed
+ programs. If used, for example, to transmit executable
+ binary programs or programs in general-purpose interpreted
+ languages, such as LISP programs or shell scripts, severe
+ security problems could result. In general, authors of
+ mail-reading agents are cautioned against giving their
+ systems the power to execute mail-based application data
+ without carefully considering the security implications.
+ While it is certainly possible to define safe application
+ formats and even safe interpreters for unsafe formats, each
+ interpreter should be evaluated separately for possible
+ security problems.
+ ________________________________________________________________
+
+ Content-type: image
+
+ Subtypes defined by this document: jpeg, gif
+
+ Important Parameters: none
+
+ Encoding notes: base64 generally preferred
+
+ ________________________________________________________________
+
+ Content-type: audio
+
+ Subtypes defined by this document: basic
+
+ Important Parameters: none
+
+ Encoding notes: base64 generally preferred
+
+ ________________________________________________________________
+
+ Content-type: video
+
+ Subtypes defined by this document: mpeg
+
+ Important Parameters: none
+
+ Encoding notes: base64 generally preferred
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 72]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Appendix H -- Canonical Encoding Model
+
+
+
+ There was some confusion, in earlier drafts of this memo,
+ regarding the model for when email data was to be converted
+ to canonical form and encoded, and in particular how this
+ process would affect the treatment of CRLFs, given that the
+ representation of newlines varies greatly from system to
+ system. For this reason, a canonical model for encoding is
+ presented below.
+
+ The process of composing a MIME message part can be modelled
+ as being done in a number of steps. Note that these steps
+ are roughly similar to those steps used in RFC1113:
+
+ Step 1. Creation of local form.
+
+ The body part to be transmitted is created in the system's
+ native format. The native character set is used, and where
+ appropriate local end of line conventions are used as well.
+ The may be a UNIX-style text file, or a Sun raster image, or
+ a VMS indexed file, or audio data in a system-dependent
+ format stored only in memory, or anything else that
+ corresponds to the local model for the representation of
+ some form of information.
+
+ Step 2. Conversion to canonical form.
+
+ The entire body part, including "out-of-band" information
+ such as record lengths and possibly file attribute
+ information, is converted to a universal canonical form.
+ The specific content type of the body part as well as its
+ associated attributes dictate the nature of the canonical
+ form that is used. Conversion to the proper canonical form
+ may involve character set conversion, transformation of
+ audio data, compression, or various other operations
+ specific to the various content types.
+
+ For example, in the case of text/plain data, the text must
+ be converted to a supported character set and lines must be
+ delimited with CRLF delimiters in accordance with RFC822.
+ Note that the restriction on line lengths implied by RFC822
+ is eliminated if the next step employs either quoted-
+ printable or base64 encoding.
+
+ Step 3. Apply transfer encoding.
+
+ A Content-Transfer-Encoding appropriate for this body part
+ is applied. Note that there is no fixed relationship
+ between the content type and the transfer encoding. In
+ particular, it may be appropriate to base the choice of
+ base64 or quoted-printable on character frequency counts
+ which are specific to a given instance of body part.
+
+
+
+ Borenstein & Freed [Page 73]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Step 4. Insertion into message.
+
+ The encoded object is inserted into a MIME message with
+ appropriate body part headers and boundary markers.
+
+ It is vital to note that these steps are only a model; they
+ are specifically NOT a blueprint for how an actual system
+ would be built. In particular, the model fails to account
+ for two common designs:
+
+ 1. In many cases the conversion to a canonical
+ form prior to encoding will be subsumed into the
+ encoder itself, which understands local formats
+ directly. For example, the local newline
+ convention for text bodyparts might be carried
+ through to the encoder itself along with knowledge
+ of what that format is.
+
+ 2. The output of the encoders may have to pass
+ through one or more additional steps prior to
+ being transmitted as a message. As such, the
+ output of the encoder may not be compliant with
+ the formats specified by RFC822. In particular,
+ once again it may be appropriate for the
+ converter's output to be expressed using local
+ newline conventions rather than using the standard
+ RFC822 CRLF delimiters.
+
+ Other implementation variations are conceivable as well.
+ The only important aspect of this discussion is that the
+ resulting messages are consistent with those produced by the
+ model described here.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Borenstein & Freed [Page 74]
+
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+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ References
+
+ [US-ASCII] Coded Character Set--7-Bit American Standard Code
+ for Information Interchange, ANSI X3.4-1986.
+
+ [ATK] Borenstein, Nathaniel S., Multimedia Applications
+ Development with the Andrew Toolkit, Prentice-Hall, 1990.
+
+ [GIF] Graphics Interchange Format (Version 89a), Compuserve,
+ Inc., Columbus, Ohio, 1990.
+
+ [ISO-2022] International Standard--Information Processing--
+ ISO 7-bit and 8-bit coded character sets--Code extension
+ techniques, ISO 2022:1986.
+
+ [ISO-8859] Information Processing -- 8-bit Single-Byte Coded
+ Graphic Character Sets -- Part 1: Latin Alphabet No. 1, ISO
+ 8859-1:1987. Part 2: Latin alphabet No. 2, ISO 8859-2,
+ 1987. Part 3: Latin alphabet No. 3, ISO 8859-3, 1988. Part
+ 4: Latin alphabet No. 4, ISO 8859-4, 1988. Part 5:
+ Latin/Cyrillic alphabet, ISO 8859-5, 1988. Part 6:
+ Latin/Arabic alphabet, ISO 8859-6, 1987. Part 7:
+ Latin/Greek alphabet, ISO 8859-7, 1987. Part 8:
+ Latin/Hebrew alphabet, ISO 8859-8, 1988. Part 9: Latin
+ alphabet No. 5, ISO 8859-9, 1990.
+
+ [ISO-646] International Standard--Information Processing--
+ ISO 7-bit coded character set for information interchange,
+ ISO 646:1983.
+
+ [MPEG] Video Coding Draft Standard ISO 11172 CD, ISO
+ IEC/TJC1/SC2/WG11 (Motion Picture Experts Group), May, 1991.
+
+ [ODA] ISO 8613; Information Processing: Text and Office
+ System; Office Document Architecture (ODA) and Interchange
+ Format (ODIF), Part 1-8, 1989.
+
+ [PCM] CCITT, Fascicle III.4 - Recommendation G.711, Geneva,
+ 1972, "Pulse Code Modulation (PCM) of Voice Frequencies".
+
+ [POSTSCRIPT] Adobe Systems, Inc., PostScript Language
+ Reference Manual, Addison-Wesley, 1985.
+
+ [X400] Schicker, Pietro, "Message Handling Systems, X.400",
+ Message Handling Systems and Distributed Applications, E.
+ Stefferud, O-j. Jacobsen, and P. Schicker, eds., North-
+ Holland, 1989, pp. 3-41.
+
+ [RFC-783] Sollins, K.R. TFTP Protocol (revision 2). June,
+ 1981, MIT, RFC-783.
+
+ [RFC-821] Postel, J.B. Simple Mail Transfer Protocol.
+ August, 1982, USC/Information Sciences Institute, RFC-821.
+
+
+
+
+ Borenstein & Freed [Page 75]
+
+
+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ [RFC-822] Crocker, D. Standard for the format of ARPA
+ Internet text messages. August, 1982, UDEL, RFC-822.
+
+ [RFC-934] Rose, M.T.; Stefferud, E.A. Proposed standard
+ for message encapsulation. January, 1985, Delaware
+ and NMA, RFC-934.
+
+ [RFC-959] Postel, J.B.; Reynolds, J.K. File Transfer
+ Protocol. October, 1985, USC/Information Sciences
+ Institute, RFC-959.
+
+ [RFC-1049] Sirbu, M.A. Content-Type header field for
+ Internet messages. March, 1988, CMU, RFC-1049.
+
+ [RFC-1113] Linn, J. Privacy enhancement for Internet
+ electronic mail: Part I - message encipherment and
+ authentication procedures. August, 1989, IAB Privacy Task
+ Force, RFC-1113.
+
+ [RFC-1154] Robinson, D.; Ullmann, R. Encoding header field
+ for Internet messages. April, 1990, Prime Computer,
+ Inc., RFC-1154.
+
+ [RFC-1342] Moore, Keith, Representation of Non-Ascii Text in
+ Internet Message Headers. June, 1992, University of
+ Tennessee, RFC-1342.
+
+ Security Considerations
+
+ Security issues are discussed in Section 7.4.2 and in
+ Appendix G. Implementors should pay special attention to
+ the security implications of any mail content-types that can
+ cause the remote execution of any actions in the recipient's
+ environment. In such cases, the discussion of the
+ applicaton/postscript content-type in Section 7.4.2 may
+ serve as a model for considering other content-types with
+ remote execution capabilities.
+
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+ Borenstein & Freed [Page 76]
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+
+
+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
+
+
+ Authors' Addresses
+
+ For more information, the authors of this document may be
+ contacted via Internet mail:
+
+ Nathaniel S. Borenstein
+ MRE 2D-296, Bellcore
+ 445 South St.
+ Morristown, NJ 07962-1910
+
+ Phone: +1 201 829 4270
+ Fax: +1 201 829 7019
+ Email: nsb@bellcore.com
+
+
+ Ned Freed
+ Innosoft International, Inc.
+ 250 West First Street
+ Suite 240
+ Claremont, CA 91711
+
+ Phone: +1 714 624 7907
+ Fax: +1 714 621 5319
+ Email: ned@innosoft.com
+
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+ RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
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+ THIS PAGE INTENTIONALLY LEFT BLANK.
+
+ Please discard this page and place the following table of
+ contents after the title page.
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+ Table of Contents
+
+
+ 1 Introduction....................................... 1
+ 2 Notations, Conventions, and Generic BNF Grammar.... 3
+ 3 The MIME-Version Header Field...................... 5
+ 4 The Content-Type Header Field...................... 6
+ 5 The Content-Transfer-Encoding Header Field......... 10
+ 5.1 Quoted-Printable Content-Transfer-Encoding......... 14
+ 5.2 Base64 Content-Transfer-Encoding................... 17
+ 6 Additional Optional Content- Header Fields......... 19
+ 6.1 Optional Content-ID Header Field................... 19
+ 6.2 Optional Content-Description Header Field.......... 19
+ 7 The Predefined Content-Type Values................. 20
+ 7.1 The Text Content-Type.............................. 20
+ 7.1.1 The charset parameter.............................. 20
+ 7.1.2 The Text/plain subtype............................. 23
+ 7.1.3 The Text/richtext subtype.......................... 23
+ 7.2 The Multipart Content-Type......................... 29
+ 7.2.1 Multipart: The common syntax...................... 30
+ 7.2.2 The Multipart/mixed (primary) subtype.............. 34
+ 7.2.3 The Multipart/alternative subtype.................. 34
+ 7.2.4 The Multipart/digest subtype....................... 36
+ 7.2.5 The Multipart/parallel subtype..................... 36
+ 7.3 The Message Content-Type........................... 37
+ 7.3.1 The Message/rfc822 (primary) subtype............... 37
+ 7.3.2 The Message/Partial subtype........................ 37
+ 7.3.3 The Message/External-Body subtype.................. 40
+ 7.4 The Application Content-Type....................... 46
+ 7.4.1 The Application/Octet-Stream (primary) subtype..... 46
+ 7.4.2 The Application/PostScript subtype................. 47
+ 7.4.3 The Application/ODA subtype........................ 50
+ 7.5 The Image Content-Type............................. 51
+ 7.6 The Audio Content-Type............................. 51
+ 7.7 The Video Content-Type............................. 51
+ 7.8 Experimental Content-Type Values................... 51
+ Summary............................................ 53
+ Acknowledgements................................... 54
+ Appendix A -- Minimal MIME-Conformance............. 56
+ Appendix B -- General Guidelines For Sending Email Data59
+ Appendix C -- A Complex Multipart Example.......... 62
+ Appendix D -- A Simple Richtext-to-Text Translator in C64
+ Appendix E -- Collected Grammar.................... 66
+ Appendix F -- IANA Registration Procedures......... 68
+ F.1 Registration of New Content-type/subtype Values..68
+ F.2 Registration of New Character Set Values...... 69
+ F.3 Registration of New Access-type Values for Message/external-body69
+ F.4 Registration of New Conversions Values for Application69
+ Appendix G -- Summary of the Seven Content-types... 71
+ Appendix H -- Canonical Encoding Model............. 73
+ References......................................... 75
+ Security Considerations............................ 76
+ Authors' Addresses................................. 77
+
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diff --git a/rfc/rfc2045.txt b/rfc/rfc2045.txt
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+
+
+Network Working Group N. Freed
+Request for Comments: 2045 Innosoft
+Obsoletes: 1521, 1522, 1590 N. Borenstein
+Category: Standards Track First Virtual
+ November 1996
+
+
+ Multipurpose Internet Mail Extensions
+ (MIME) Part One:
+ Format of Internet Message Bodies
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ STD 11, RFC 822, defines a message representation protocol specifying
+ considerable detail about US-ASCII message headers, and leaves the
+ message content, or message body, as flat US-ASCII text. This set of
+ documents, collectively called the Multipurpose Internet Mail
+ Extensions, or MIME, redefines the format of messages to allow for
+
+ (1) textual message bodies in character sets other than
+ US-ASCII,
+
+ (2) an extensible set of different formats for non-textual
+ message bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than
+ US-ASCII.
+
+ These documents are based on earlier work documented in RFC 934, STD
+ 11, and RFC 1049, but extends and revises them. Because RFC 822 said
+ so little about message bodies, these documents are largely
+ orthogonal to (rather than a revision of) RFC 822.
+
+ This initial document specifies the various headers used to describe
+ the structure of MIME messages. The second document, RFC 2046,
+ defines the general structure of the MIME media typing system and
+ defines an initial set of media types. The third document, RFC 2047,
+ describes extensions to RFC 822 to allow non-US-ASCII text data in
+
+
+
+Freed & Borenstein Standards Track [Page 1]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ Internet mail header fields. The fourth document, RFC 2048, specifies
+ various IANA registration procedures for MIME-related facilities. The
+ fifth and final document, RFC 2049, describes MIME conformance
+ criteria as well as providing some illustrative examples of MIME
+ message formats, acknowledgements, and the bibliography.
+
+ These documents are revisions of RFCs 1521, 1522, and 1590, which
+ themselves were revisions of RFCs 1341 and 1342. An appendix in RFC
+ 2049 describes differences and changes from previous versions.
+
+Table of Contents
+
+ 1. Introduction ......................................... 3
+ 2. Definitions, Conventions, and Generic BNF Grammar .... 5
+ 2.1 CRLF ................................................ 5
+ 2.2 Character Set ....................................... 6
+ 2.3 Message ............................................. 6
+ 2.4 Entity .............................................. 6
+ 2.5 Body Part ........................................... 7
+ 2.6 Body ................................................ 7
+ 2.7 7bit Data ........................................... 7
+ 2.8 8bit Data ........................................... 7
+ 2.9 Binary Data ......................................... 7
+ 2.10 Lines .............................................. 7
+ 3. MIME Header Fields ................................... 8
+ 4. MIME-Version Header Field ............................ 8
+ 5. Content-Type Header Field ............................ 10
+ 5.1 Syntax of the Content-Type Header Field ............. 12
+ 5.2 Content-Type Defaults ............................... 14
+ 6. Content-Transfer-Encoding Header Field ............... 14
+ 6.1 Content-Transfer-Encoding Syntax .................... 14
+ 6.2 Content-Transfer-Encodings Semantics ................ 15
+ 6.3 New Content-Transfer-Encodings ...................... 16
+ 6.4 Interpretation and Use .............................. 16
+ 6.5 Translating Encodings ............................... 18
+ 6.6 Canonical Encoding Model ............................ 19
+ 6.7 Quoted-Printable Content-Transfer-Encoding .......... 19
+ 6.8 Base64 Content-Transfer-Encoding .................... 24
+ 7. Content-ID Header Field .............................. 26
+ 8. Content-Description Header Field ..................... 27
+ 9. Additional MIME Header Fields ........................ 27
+ 10. Summary ............................................. 27
+ 11. Security Considerations ............................. 27
+ 12. Authors' Addresses .................................. 28
+ A. Collected Grammar .................................... 29
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 2]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+1. Introduction
+
+ Since its publication in 1982, RFC 822 has defined the standard
+ format of textual mail messages on the Internet. Its success has
+ been such that the RFC 822 format has been adopted, wholly or
+ partially, well beyond the confines of the Internet and the Internet
+ SMTP transport defined by RFC 821. As the format has seen wider use,
+ a number of limitations have proven increasingly restrictive for the
+ user community.
+
+ RFC 822 was intended to specify a format for text messages. As such,
+ non-text messages, such as multimedia messages that might include
+ audio or images, are simply not mentioned. Even in the case of text,
+ however, RFC 822 is inadequate for the needs of mail users whose
+ languages require the use of character sets richer than US-ASCII.
+ Since RFC 822 does not specify mechanisms for mail containing audio,
+ video, Asian language text, or even text in most European languages,
+ additional specifications are needed.
+
+ One of the notable limitations of RFC 821/822 based mail systems is
+ the fact that they limit the contents of electronic mail messages to
+ relatively short lines (e.g. 1000 characters or less [RFC-821]) of
+ 7bit US-ASCII. This forces users to convert any non-textual data
+ that they may wish to send into seven-bit bytes representable as
+ printable US-ASCII characters before invoking a local mail UA (User
+ Agent, a program with which human users send and receive mail).
+ Examples of such encodings currently used in the Internet include
+ pure hexadecimal, uuencode, the 3-in-4 base 64 scheme specified in
+ RFC 1421, the Andrew Toolkit Representation [ATK], and many others.
+
+ The limitations of RFC 822 mail become even more apparent as gateways
+ are designed to allow for the exchange of mail messages between RFC
+ 822 hosts and X.400 hosts. X.400 [X400] specifies mechanisms for the
+ inclusion of non-textual material within electronic mail messages.
+ The current standards for the mapping of X.400 messages to RFC 822
+ messages specify either that X.400 non-textual material must be
+ converted to (not encoded in) IA5Text format, or that they must be
+ discarded, notifying the RFC 822 user that discarding has occurred.
+ This is clearly undesirable, as information that a user may wish to
+ receive is lost. Even though a user agent may not have the
+ capability of dealing with the non-textual material, the user might
+ have some mechanism external to the UA that can extract useful
+ information from the material. Moreover, it does not allow for the
+ fact that the message may eventually be gatewayed back into an X.400
+ message handling system (i.e., the X.400 message is "tunneled"
+ through Internet mail), where the non-textual information would
+ definitely become useful again.
+
+
+
+
+Freed & Borenstein Standards Track [Page 3]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ This document describes several mechanisms that combine to solve most
+ of these problems without introducing any serious incompatibilities
+ with the existing world of RFC 822 mail. In particular, it
+ describes:
+
+ (1) A MIME-Version header field, which uses a version
+ number to declare a message to be conformant with MIME
+ and allows mail processing agents to distinguish
+ between such messages and those generated by older or
+ non-conformant software, which are presumed to lack
+ such a field.
+
+ (2) A Content-Type header field, generalized from RFC 1049,
+ which can be used to specify the media type and subtype
+ of data in the body of a message and to fully specify
+ the native representation (canonical form) of such
+ data.
+
+ (3) A Content-Transfer-Encoding header field, which can be
+ used to specify both the encoding transformation that
+ was applied to the body and the domain of the result.
+ Encoding transformations other than the identity
+ transformation are usually applied to data in order to
+ allow it to pass through mail transport mechanisms
+ which may have data or character set limitations.
+
+ (4) Two additional header fields that can be used to
+ further describe the data in a body, the Content-ID and
+ Content-Description header fields.
+
+ All of the header fields defined in this document are subject to the
+ general syntactic rules for header fields specified in RFC 822. In
+ particular, all of these header fields except for Content-Disposition
+ can include RFC 822 comments, which have no semantic content and
+ should be ignored during MIME processing.
+
+ Finally, to specify and promote interoperability, RFC 2049 provides a
+ basic applicability statement for a subset of the above mechanisms
+ that defines a minimal level of "conformance" with this document.
+
+ HISTORICAL NOTE: Several of the mechanisms described in this set of
+ documents may seem somewhat strange or even baroque at first reading.
+ It is important to note that compatibility with existing standards
+ AND robustness across existing practice were two of the highest
+ priorities of the working group that developed this set of documents.
+ In particular, compatibility was always favored over elegance.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 4]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ Please refer to the current edition of the "Internet Official
+ Protocol Standards" for the standardization state and status of this
+ protocol. RFC 822 and STD 3, RFC 1123 also provide essential
+ background for MIME since no conforming implementation of MIME can
+ violate them. In addition, several other informational RFC documents
+ will be of interest to the MIME implementor, in particular RFC 1344,
+ RFC 1345, and RFC 1524.
+
+2. Definitions, Conventions, and Generic BNF Grammar
+
+ Although the mechanisms specified in this set of documents are all
+ described in prose, most are also described formally in the augmented
+ BNF notation of RFC 822. Implementors will need to be familiar with
+ this notation in order to understand this set of documents, and are
+ referred to RFC 822 for a complete explanation of the augmented BNF
+ notation.
+
+ Some of the augmented BNF in this set of documents makes named
+ references to syntax rules defined in RFC 822. A complete formal
+ grammar, then, is obtained by combining the collected grammar
+ appendices in each document in this set with the BNF of RFC 822 plus
+ the modifications to RFC 822 defined in RFC 1123 (which specifically
+ changes the syntax for `return', `date' and `mailbox').
+
+ All numeric and octet values are given in decimal notation in this
+ set of documents. All media type values, subtype values, and
+ parameter names as defined are case-insensitive. However, parameter
+ values are case-sensitive unless otherwise specified for the specific
+ parameter.
+
+ FORMATTING NOTE: Notes, such at this one, provide additional
+ nonessential information which may be skipped by the reader without
+ missing anything essential. The primary purpose of these non-
+ essential notes is to convey information about the rationale of this
+ set of documents, or to place these documents in the proper
+ historical or evolutionary context. Such information may in
+ particular be skipped by those who are focused entirely on building a
+ conformant implementation, but may be of use to those who wish to
+ understand why certain design choices were made.
+
+2.1. CRLF
+
+ The term CRLF, in this set of documents, refers to the sequence of
+ octets corresponding to the two US-ASCII characters CR (decimal value
+ 13) and LF (decimal value 10) which, taken together, in this order,
+ denote a line break in RFC 822 mail.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 5]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+2.2. Character Set
+
+ The term "character set" is used in MIME to refer to a method of
+ converting a sequence of octets into a sequence of characters. Note
+ that unconditional and unambiguous conversion in the other direction
+ is not required, in that not all characters may be representable by a
+ given character set and a character set may provide more than one
+ sequence of octets to represent a particular sequence of characters.
+
+ This definition is intended to allow various kinds of character
+ encodings, from simple single-table mappings such as US-ASCII to
+ complex table switching methods such as those that use ISO 2022's
+ techniques, to be used as character sets. However, the definition
+ associated with a MIME character set name must fully specify the
+ mapping to be performed. In particular, use of external profiling
+ information to determine the exact mapping is not permitted.
+
+ NOTE: The term "character set" was originally to describe such
+ straightforward schemes as US-ASCII and ISO-8859-1 which have a
+ simple one-to-one mapping from single octets to single characters.
+ Multi-octet coded character sets and switching techniques make the
+ situation more complex. For example, some communities use the term
+ "character encoding" for what MIME calls a "character set", while
+ using the phrase "coded character set" to denote an abstract mapping
+ from integers (not octets) to characters.
+
+2.3. Message
+
+ The term "message", when not further qualified, means either a
+ (complete or "top-level") RFC 822 message being transferred on a
+ network, or a message encapsulated in a body of type "message/rfc822"
+ or "message/partial".
+
+2.4. Entity
+
+ The term "entity", refers specifically to the MIME-defined header
+ fields and contents of either a message or one of the parts in the
+ body of a multipart entity. The specification of such entities is
+ the essence of MIME. Since the contents of an entity are often
+ called the "body", it makes sense to speak about the body of an
+ entity. Any sort of field may be present in the header of an entity,
+ but only those fields whose names begin with "content-" actually have
+ any MIME-related meaning. Note that this does NOT imply thay they
+ have no meaning at all -- an entity that is also a message has non-
+ MIME header fields whose meanings are defined by RFC 822.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 6]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+2.5. Body Part
+
+ The term "body part" refers to an entity inside of a multipart
+ entity.
+
+2.6. Body
+
+ The term "body", when not further qualified, means the body of an
+ entity, that is, the body of either a message or of a body part.
+
+ NOTE: The previous four definitions are clearly circular. This is
+ unavoidable, since the overall structure of a MIME message is indeed
+ recursive.
+
+2.7. 7bit Data
+
+ "7bit data" refers to data that is all represented as relatively
+ short lines with 998 octets or less between CRLF line separation
+ sequences [RFC-821]. No octets with decimal values greater than 127
+ are allowed and neither are NULs (octets with decimal value 0). CR
+ (decimal value 13) and LF (decimal value 10) octets only occur as
+ part of CRLF line separation sequences.
+
+2.8. 8bit Data
+
+ "8bit data" refers to data that is all represented as relatively
+ short lines with 998 octets or less between CRLF line separation
+ sequences [RFC-821]), but octets with decimal values greater than 127
+ may be used. As with "7bit data" CR and LF octets only occur as part
+ of CRLF line separation sequences and no NULs are allowed.
+
+2.9. Binary Data
+
+ "Binary data" refers to data where any sequence of octets whatsoever
+ is allowed.
+
+2.10. Lines
+
+ "Lines" are defined as sequences of octets separated by a CRLF
+ sequences. This is consistent with both RFC 821 and RFC 822.
+ "Lines" only refers to a unit of data in a message, which may or may
+ not correspond to something that is actually displayed by a user
+ agent.
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 7]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+3. MIME Header Fields
+
+ MIME defines a number of new RFC 822 header fields that are used to
+ describe the content of a MIME entity. These header fields occur in
+ at least two contexts:
+
+ (1) As part of a regular RFC 822 message header.
+
+ (2) In a MIME body part header within a multipart
+ construct.
+
+ The formal definition of these header fields is as follows:
+
+ entity-headers := [ content CRLF ]
+ [ encoding CRLF ]
+ [ id CRLF ]
+ [ description CRLF ]
+ *( MIME-extension-field CRLF )
+
+ MIME-message-headers := entity-headers
+ fields
+ version CRLF
+ ; The ordering of the header
+ ; fields implied by this BNF
+ ; definition should be ignored.
+
+ MIME-part-headers := entity-headers
+ [ fields ]
+ ; Any field not beginning with
+ ; "content-" can have no defined
+ ; meaning and may be ignored.
+ ; The ordering of the header
+ ; fields implied by this BNF
+ ; definition should be ignored.
+
+ The syntax of the various specific MIME header fields will be
+ described in the following sections.
+
+4. MIME-Version Header Field
+
+ Since RFC 822 was published in 1982, there has really been only one
+ format standard for Internet messages, and there has been little
+ perceived need to declare the format standard in use. This document
+ is an independent specification that complements RFC 822. Although
+ the extensions in this document have been defined in such a way as to
+ be compatible with RFC 822, there are still circumstances in which it
+ might be desirable for a mail-processing agent to know whether a
+ message was composed with the new standard in mind.
+
+
+
+Freed & Borenstein Standards Track [Page 8]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ Therefore, this document defines a new header field, "MIME-Version",
+ which is to be used to declare the version of the Internet message
+ body format standard in use.
+
+ Messages composed in accordance with this document MUST include such
+ a header field, with the following verbatim text:
+
+ MIME-Version: 1.0
+
+ The presence of this header field is an assertion that the message
+ has been composed in compliance with this document.
+
+ Since it is possible that a future document might extend the message
+ format standard again, a formal BNF is given for the content of the
+ MIME-Version field:
+
+ version := "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
+
+ Thus, future format specifiers, which might replace or extend "1.0",
+ are constrained to be two integer fields, separated by a period. If
+ a message is received with a MIME-version value other than "1.0", it
+ cannot be assumed to conform with this document.
+
+ Note that the MIME-Version header field is required at the top level
+ of a message. It is not required for each body part of a multipart
+ entity. It is required for the embedded headers of a body of type
+ "message/rfc822" or "message/partial" if and only if the embedded
+ message is itself claimed to be MIME-conformant.
+
+ It is not possible to fully specify how a mail reader that conforms
+ with MIME as defined in this document should treat a message that
+ might arrive in the future with some value of MIME-Version other than
+ "1.0".
+
+ It is also worth noting that version control for specific media types
+ is not accomplished using the MIME-Version mechanism. In particular,
+ some formats (such as application/postscript) have version numbering
+ conventions that are internal to the media format. Where such
+ conventions exist, MIME does nothing to supersede them. Where no
+ such conventions exist, a MIME media type might use a "version"
+ parameter in the content-type field if necessary.
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 9]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ NOTE TO IMPLEMENTORS: When checking MIME-Version values any RFC 822
+ comment strings that are present must be ignored. In particular, the
+ following four MIME-Version fields are equivalent:
+
+ MIME-Version: 1.0
+
+ MIME-Version: 1.0 (produced by MetaSend Vx.x)
+
+ MIME-Version: (produced by MetaSend Vx.x) 1.0
+
+ MIME-Version: 1.(produced by MetaSend Vx.x)0
+
+ In the absence of a MIME-Version field, a receiving mail user agent
+ (whether conforming to MIME requirements or not) may optionally
+ choose to interpret the body of the message according to local
+ conventions. Many such conventions are currently in use and it
+ should be noted that in practice non-MIME messages can contain just
+ about anything.
+
+ It is impossible to be certain that a non-MIME mail message is
+ actually plain text in the US-ASCII character set since it might well
+ be a message that, using some set of nonstandard local conventions
+ that predate MIME, includes text in another character set or non-
+ textual data presented in a manner that cannot be automatically
+ recognized (e.g., a uuencoded compressed UNIX tar file).
+
+5. Content-Type Header Field
+
+ The purpose of the Content-Type field is to describe the data
+ contained in the body fully enough that the receiving user agent can
+ pick an appropriate agent or mechanism to present the data to the
+ user, or otherwise deal with the data in an appropriate manner. The
+ value in this field is called a media type.
+
+ HISTORICAL NOTE: The Content-Type header field was first defined in
+ RFC 1049. RFC 1049 used a simpler and less powerful syntax, but one
+ that is largely compatible with the mechanism given here.
+
+ The Content-Type header field specifies the nature of the data in the
+ body of an entity by giving media type and subtype identifiers, and
+ by providing auxiliary information that may be required for certain
+ media types. After the media type and subtype names, the remainder
+ of the header field is simply a set of parameters, specified in an
+ attribute=value notation. The ordering of parameters is not
+ significant.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 10]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ In general, the top-level media type is used to declare the general
+ type of data, while the subtype specifies a specific format for that
+ type of data. Thus, a media type of "image/xyz" is enough to tell a
+ user agent that the data is an image, even if the user agent has no
+ knowledge of the specific image format "xyz". Such information can
+ be used, for example, to decide whether or not to show a user the raw
+ data from an unrecognized subtype -- such an action might be
+ reasonable for unrecognized subtypes of text, but not for
+ unrecognized subtypes of image or audio. For this reason, registered
+ subtypes of text, image, audio, and video should not contain embedded
+ information that is really of a different type. Such compound
+ formats should be represented using the "multipart" or "application"
+ types.
+
+ Parameters are modifiers of the media subtype, and as such do not
+ fundamentally affect the nature of the content. The set of
+ meaningful parameters depends on the media type and subtype. Most
+ parameters are associated with a single specific subtype. However, a
+ given top-level media type may define parameters which are applicable
+ to any subtype of that type. Parameters may be required by their
+ defining content type or subtype or they may be optional. MIME
+ implementations must ignore any parameters whose names they do not
+ recognize.
+
+ For example, the "charset" parameter is applicable to any subtype of
+ "text", while the "boundary" parameter is required for any subtype of
+ the "multipart" media type.
+
+ There are NO globally-meaningful parameters that apply to all media
+ types. Truly global mechanisms are best addressed, in the MIME
+ model, by the definition of additional Content-* header fields.
+
+ An initial set of seven top-level media types is defined in RFC 2046.
+ Five of these are discrete types whose content is essentially opaque
+ as far as MIME processing is concerned. The remaining two are
+ composite types whose contents require additional handling by MIME
+ processors.
+
+ This set of top-level media types is intended to be substantially
+ complete. It is expected that additions to the larger set of
+ supported types can generally be accomplished by the creation of new
+ subtypes of these initial types. In the future, more top-level types
+ may be defined only by a standards-track extension to this standard.
+ If another top-level type is to be used for any reason, it must be
+ given a name starting with "X-" to indicate its non-standard status
+ and to avoid a potential conflict with a future official name.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 11]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+5.1. Syntax of the Content-Type Header Field
+
+ In the Augmented BNF notation of RFC 822, a Content-Type header field
+ value is defined as follows:
+
+ content := "Content-Type" ":" type "/" subtype
+ *(";" parameter)
+ ; Matching of media type and subtype
+ ; is ALWAYS case-insensitive.
+
+ type := discrete-type / composite-type
+
+ discrete-type := "text" / "image" / "audio" / "video" /
+ "application" / extension-token
+
+ composite-type := "message" / "multipart" / extension-token
+
+ extension-token := ietf-token / x-token
+
+ ietf-token := <An extension token defined by a
+ standards-track RFC and registered
+ with IANA.>
+
+ x-token := <The two characters "X-" or "x-" followed, with
+ no intervening white space, by any token>
+
+ subtype := extension-token / iana-token
+
+ iana-token := <A publicly-defined extension token. Tokens
+ of this form must be registered with IANA
+ as specified in RFC 2048.>
+
+ parameter := attribute "=" value
+
+ attribute := token
+ ; Matching of attributes
+ ; is ALWAYS case-insensitive.
+
+ value := token / quoted-string
+
+ token := 1*<any (US-ASCII) CHAR except SPACE, CTLs,
+ or tspecials>
+
+ tspecials := "(" / ")" / "<" / ">" / "@" /
+ "," / ";" / ":" / "\" / <">
+ "/" / "[" / "]" / "?" / "="
+ ; Must be in quoted-string,
+ ; to use within parameter values
+
+
+
+Freed & Borenstein Standards Track [Page 12]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ Note that the definition of "tspecials" is the same as the RFC 822
+ definition of "specials" with the addition of the three characters
+ "/", "?", and "=", and the removal of ".".
+
+ Note also that a subtype specification is MANDATORY -- it may not be
+ omitted from a Content-Type header field. As such, there are no
+ default subtypes.
+
+ The type, subtype, and parameter names are not case sensitive. For
+ example, TEXT, Text, and TeXt are all equivalent top-level media
+ types. Parameter values are normally case sensitive, but sometimes
+ are interpreted in a case-insensitive fashion, depending on the
+ intended use. (For example, multipart boundaries are case-sensitive,
+ but the "access-type" parameter for message/External-body is not
+ case-sensitive.)
+
+ Note that the value of a quoted string parameter does not include the
+ quotes. That is, the quotation marks in a quoted-string are not a
+ part of the value of the parameter, but are merely used to delimit
+ that parameter value. In addition, comments are allowed in
+ accordance with RFC 822 rules for structured header fields. Thus the
+ following two forms
+
+ Content-type: text/plain; charset=us-ascii (Plain text)
+
+ Content-type: text/plain; charset="us-ascii"
+
+ are completely equivalent.
+
+ Beyond this syntax, the only syntactic constraint on the definition
+ of subtype names is the desire that their uses must not conflict.
+ That is, it would be undesirable to have two different communities
+ using "Content-Type: application/foobar" to mean two different
+ things. The process of defining new media subtypes, then, is not
+ intended to be a mechanism for imposing restrictions, but simply a
+ mechanism for publicizing their definition and usage. There are,
+ therefore, two acceptable mechanisms for defining new media subtypes:
+
+ (1) Private values (starting with "X-") may be defined
+ bilaterally between two cooperating agents without
+ outside registration or standardization. Such values
+ cannot be registered or standardized.
+
+ (2) New standard values should be registered with IANA as
+ described in RFC 2048.
+
+ The second document in this set, RFC 2046, defines the initial set of
+ media types for MIME.
+
+
+
+Freed & Borenstein Standards Track [Page 13]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+5.2. Content-Type Defaults
+
+ Default RFC 822 messages without a MIME Content-Type header are taken
+ by this protocol to be plain text in the US-ASCII character set,
+ which can be explicitly specified as:
+
+ Content-type: text/plain; charset=us-ascii
+
+ This default is assumed if no Content-Type header field is specified.
+ It is also recommend that this default be assumed when a
+ syntactically invalid Content-Type header field is encountered. In
+ the presence of a MIME-Version header field and the absence of any
+ Content-Type header field, a receiving User Agent can also assume
+ that plain US-ASCII text was the sender's intent. Plain US-ASCII
+ text may still be assumed in the absence of a MIME-Version or the
+ presence of an syntactically invalid Content-Type header field, but
+ the sender's intent might have been otherwise.
+
+6. Content-Transfer-Encoding Header Field
+
+ Many media types which could be usefully transported via email are
+ represented, in their "natural" format, as 8bit character or binary
+ data. Such data cannot be transmitted over some transfer protocols.
+ For example, RFC 821 (SMTP) restricts mail messages to 7bit US-ASCII
+ data with lines no longer than 1000 characters including any trailing
+ CRLF line separator.
+
+ It is necessary, therefore, to define a standard mechanism for
+ encoding such data into a 7bit short line format. Proper labelling
+ of unencoded material in less restrictive formats for direct use over
+ less restrictive transports is also desireable. This document
+ specifies that such encodings will be indicated by a new "Content-
+ Transfer-Encoding" header field. This field has not been defined by
+ any previous standard.
+
+6.1. Content-Transfer-Encoding Syntax
+
+ The Content-Transfer-Encoding field's value is a single token
+ specifying the type of encoding, as enumerated below. Formally:
+
+ encoding := "Content-Transfer-Encoding" ":" mechanism
+
+ mechanism := "7bit" / "8bit" / "binary" /
+ "quoted-printable" / "base64" /
+ ietf-token / x-token
+
+ These values are not case sensitive -- Base64 and BASE64 and bAsE64
+ are all equivalent. An encoding type of 7BIT requires that the body
+
+
+
+Freed & Borenstein Standards Track [Page 14]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ is already in a 7bit mail-ready representation. This is the default
+ value -- that is, "Content-Transfer-Encoding: 7BIT" is assumed if the
+ Content-Transfer-Encoding header field is not present.
+
+6.2. Content-Transfer-Encodings Semantics
+
+ This single Content-Transfer-Encoding token actually provides two
+ pieces of information. It specifies what sort of encoding
+ transformation the body was subjected to and hence what decoding
+ operation must be used to restore it to its original form, and it
+ specifies what the domain of the result is.
+
+ The transformation part of any Content-Transfer-Encodings specifies,
+ either explicitly or implicitly, a single, well-defined decoding
+ algorithm, which for any sequence of encoded octets either transforms
+ it to the original sequence of octets which was encoded, or shows
+ that it is illegal as an encoded sequence. Content-Transfer-
+ Encodings transformations never depend on any additional external
+ profile information for proper operation. Note that while decoders
+ must produce a single, well-defined output for a valid encoding no
+ such restrictions exist for encoders: Encoding a given sequence of
+ octets to different, equivalent encoded sequences is perfectly legal.
+
+ Three transformations are currently defined: identity, the "quoted-
+ printable" encoding, and the "base64" encoding. The domains are
+ "binary", "8bit" and "7bit".
+
+ The Content-Transfer-Encoding values "7bit", "8bit", and "binary" all
+ mean that the identity (i.e. NO) encoding transformation has been
+ performed. As such, they serve simply as indicators of the domain of
+ the body data, and provide useful information about the sort of
+ encoding that might be needed for transmission in a given transport
+ system. The terms "7bit data", "8bit data", and "binary data" are
+ all defined in Section 2.
+
+ The quoted-printable and base64 encodings transform their input from
+ an arbitrary domain into material in the "7bit" range, thus making it
+ safe to carry over restricted transports. The specific definition of
+ the transformations are given below.
+
+ The proper Content-Transfer-Encoding label must always be used.
+ Labelling unencoded data containing 8bit characters as "7bit" is not
+ allowed, nor is labelling unencoded non-line-oriented data as
+ anything other than "binary" allowed.
+
+ Unlike media subtypes, a proliferation of Content-Transfer-Encoding
+ values is both undesirable and unnecessary. However, establishing
+ only a single transformation into the "7bit" domain does not seem
+
+
+
+Freed & Borenstein Standards Track [Page 15]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ possible. There is a tradeoff between the desire for a compact and
+ efficient encoding of largely- binary data and the desire for a
+ somewhat readable encoding of data that is mostly, but not entirely,
+ 7bit. For this reason, at least two encoding mechanisms are
+ necessary: a more or less readable encoding (quoted-printable) and a
+ "dense" or "uniform" encoding (base64).
+
+ Mail transport for unencoded 8bit data is defined in RFC 1652. As of
+ the initial publication of this document, there are no standardized
+ Internet mail transports for which it is legitimate to include
+ unencoded binary data in mail bodies. Thus there are no
+ circumstances in which the "binary" Content-Transfer-Encoding is
+ actually valid in Internet mail. However, in the event that binary
+ mail transport becomes a reality in Internet mail, or when MIME is
+ used in conjunction with any other binary-capable mail transport
+ mechanism, binary bodies must be labelled as such using this
+ mechanism.
+
+ NOTE: The five values defined for the Content-Transfer-Encoding field
+ imply nothing about the media type other than the algorithm by which
+ it was encoded or the transport system requirements if unencoded.
+
+6.3. New Content-Transfer-Encodings
+
+ Implementors may, if necessary, define private Content-Transfer-
+ Encoding values, but must use an x-token, which is a name prefixed by
+ "X-", to indicate its non-standard status, e.g., "Content-Transfer-
+ Encoding: x-my-new-encoding". Additional standardized Content-
+ Transfer-Encoding values must be specified by a standards-track RFC.
+ The requirements such specifications must meet are given in RFC 2048.
+ As such, all content-transfer-encoding namespace except that
+ beginning with "X-" is explicitly reserved to the IETF for future
+ use.
+
+ Unlike media types and subtypes, the creation of new Content-
+ Transfer-Encoding values is STRONGLY discouraged, as it seems likely
+ to hinder interoperability with little potential benefit
+
+6.4. Interpretation and Use
+
+ If a Content-Transfer-Encoding header field appears as part of a
+ message header, it applies to the entire body of that message. If a
+ Content-Transfer-Encoding header field appears as part of an entity's
+ headers, it applies only to the body of that entity. If an entity is
+ of type "multipart" the Content-Transfer-Encoding is not permitted to
+ have any value other than "7bit", "8bit" or "binary". Even more
+ severe restrictions apply to some subtypes of the "message" type.
+
+
+
+
+Freed & Borenstein Standards Track [Page 16]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ It should be noted that most media types are defined in terms of
+ octets rather than bits, so that the mechanisms described here are
+ mechanisms for encoding arbitrary octet streams, not bit streams. If
+ a bit stream is to be encoded via one of these mechanisms, it must
+ first be converted to an 8bit byte stream using the network standard
+ bit order ("big-endian"), in which the earlier bits in a stream
+ become the higher-order bits in a 8bit byte. A bit stream not ending
+ at an 8bit boundary must be padded with zeroes. RFC 2046 provides a
+ mechanism for noting the addition of such padding in the case of the
+ application/octet-stream media type, which has a "padding" parameter.
+
+ The encoding mechanisms defined here explicitly encode all data in
+ US-ASCII. Thus, for example, suppose an entity has header fields
+ such as:
+
+ Content-Type: text/plain; charset=ISO-8859-1
+ Content-transfer-encoding: base64
+
+ This must be interpreted to mean that the body is a base64 US-ASCII
+ encoding of data that was originally in ISO-8859-1, and will be in
+ that character set again after decoding.
+
+ Certain Content-Transfer-Encoding values may only be used on certain
+ media types. In particular, it is EXPRESSLY FORBIDDEN to use any
+ encodings other than "7bit", "8bit", or "binary" with any composite
+ media type, i.e. one that recursively includes other Content-Type
+ fields. Currently the only composite media types are "multipart" and
+ "message". All encodings that are desired for bodies of type
+ multipart or message must be done at the innermost level, by encoding
+ the actual body that needs to be encoded.
+
+ It should also be noted that, by definition, if a composite entity
+ has a transfer-encoding value such as "7bit", but one of the enclosed
+ entities has a less restrictive value such as "8bit", then either the
+ outer "7bit" labelling is in error, because 8bit data are included,
+ or the inner "8bit" labelling placed an unnecessarily high demand on
+ the transport system because the actual included data were actually
+ 7bit-safe.
+
+ NOTE ON ENCODING RESTRICTIONS: Though the prohibition against using
+ content-transfer-encodings on composite body data may seem overly
+ restrictive, it is necessary to prevent nested encodings, in which
+ data are passed through an encoding algorithm multiple times, and
+ must be decoded multiple times in order to be properly viewed.
+ Nested encodings add considerable complexity to user agents: Aside
+ from the obvious efficiency problems with such multiple encodings,
+ they can obscure the basic structure of a message. In particular,
+ they can imply that several decoding operations are necessary simply
+
+
+
+Freed & Borenstein Standards Track [Page 17]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ to find out what types of bodies a message contains. Banning nested
+ encodings may complicate the job of certain mail gateways, but this
+ seems less of a problem than the effect of nested encodings on user
+ agents.
+
+ Any entity with an unrecognized Content-Transfer-Encoding must be
+ treated as if it has a Content-Type of "application/octet-stream",
+ regardless of what the Content-Type header field actually says.
+
+ NOTE ON THE RELATIONSHIP BETWEEN CONTENT-TYPE AND CONTENT-TRANSFER-
+ ENCODING: It may seem that the Content-Transfer-Encoding could be
+ inferred from the characteristics of the media that is to be encoded,
+ or, at the very least, that certain Content-Transfer-Encodings could
+ be mandated for use with specific media types. There are several
+ reasons why this is not the case. First, given the varying types of
+ transports used for mail, some encodings may be appropriate for some
+ combinations of media types and transports but not for others. (For
+ example, in an 8bit transport, no encoding would be required for text
+ in certain character sets, while such encodings are clearly required
+ for 7bit SMTP.)
+
+ Second, certain media types may require different types of transfer
+ encoding under different circumstances. For example, many PostScript
+ bodies might consist entirely of short lines of 7bit data and hence
+ require no encoding at all. Other PostScript bodies (especially
+ those using Level 2 PostScript's binary encoding mechanism) may only
+ be reasonably represented using a binary transport encoding.
+ Finally, since the Content-Type field is intended to be an open-ended
+ specification mechanism, strict specification of an association
+ between media types and encodings effectively couples the
+ specification of an application protocol with a specific lower-level
+ transport. This is not desirable since the developers of a media
+ type should not have to be aware of all the transports in use and
+ what their limitations are.
+
+6.5. Translating Encodings
+
+ The quoted-printable and base64 encodings are designed so that
+ conversion between them is possible. The only issue that arises in
+ such a conversion is the handling of hard line breaks in quoted-
+ printable encoding output. When converting from quoted-printable to
+ base64 a hard line break in the quoted-printable form represents a
+ CRLF sequence in the canonical form of the data. It must therefore be
+ converted to a corresponding encoded CRLF in the base64 form of the
+ data. Similarly, a CRLF sequence in the canonical form of the data
+ obtained after base64 decoding must be converted to a quoted-
+ printable hard line break, but ONLY when converting text data.
+
+
+
+
+Freed & Borenstein Standards Track [Page 18]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+6.6. Canonical Encoding Model
+
+ There was some confusion, in the previous versions of this RFC,
+ regarding the model for when email data was to be converted to
+ canonical form and encoded, and in particular how this process would
+ affect the treatment of CRLFs, given that the representation of
+ newlines varies greatly from system to system, and the relationship
+ between content-transfer-encodings and character sets. A canonical
+ model for encoding is presented in RFC 2049 for this reason.
+
+6.7. Quoted-Printable Content-Transfer-Encoding
+
+ The Quoted-Printable encoding is intended to represent data that
+ largely consists of octets that correspond to printable characters in
+ the US-ASCII character set. It encodes the data in such a way that
+ the resulting octets are unlikely to be modified by mail transport.
+ If the data being encoded are mostly US-ASCII text, the encoded form
+ of the data remains largely recognizable by humans. A body which is
+ entirely US-ASCII may also be encoded in Quoted-Printable to ensure
+ the integrity of the data should the message pass through a
+ character-translating, and/or line-wrapping gateway.
+
+ In this encoding, octets are to be represented as determined by the
+ following rules:
+
+ (1) (General 8bit representation) Any octet, except a CR or
+ LF that is part of a CRLF line break of the canonical
+ (standard) form of the data being encoded, may be
+ represented by an "=" followed by a two digit
+ hexadecimal representation of the octet's value. The
+ digits of the hexadecimal alphabet, for this purpose,
+ are "0123456789ABCDEF". Uppercase letters must be
+ used; lowercase letters are not allowed. Thus, for
+ example, the decimal value 12 (US-ASCII form feed) can
+ be represented by "=0C", and the decimal value 61 (US-
+ ASCII EQUAL SIGN) can be represented by "=3D". This
+ rule must be followed except when the following rules
+ allow an alternative encoding.
+
+ (2) (Literal representation) Octets with decimal values of
+ 33 through 60 inclusive, and 62 through 126, inclusive,
+ MAY be represented as the US-ASCII characters which
+ correspond to those octets (EXCLAMATION POINT through
+ LESS THAN, and GREATER THAN through TILDE,
+ respectively).
+
+ (3) (White Space) Octets with values of 9 and 32 MAY be
+ represented as US-ASCII TAB (HT) and SPACE characters,
+
+
+
+Freed & Borenstein Standards Track [Page 19]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ respectively, but MUST NOT be so represented at the end
+ of an encoded line. Any TAB (HT) or SPACE characters
+ on an encoded line MUST thus be followed on that line
+ by a printable character. In particular, an "=" at the
+ end of an encoded line, indicating a soft line break
+ (see rule #5) may follow one or more TAB (HT) or SPACE
+ characters. It follows that an octet with decimal
+ value 9 or 32 appearing at the end of an encoded line
+ must be represented according to Rule #1. This rule is
+ necessary because some MTAs (Message Transport Agents,
+ programs which transport messages from one user to
+ another, or perform a portion of such transfers) are
+ known to pad lines of text with SPACEs, and others are
+ known to remove "white space" characters from the end
+ of a line. Therefore, when decoding a Quoted-Printable
+ body, any trailing white space on a line must be
+ deleted, as it will necessarily have been added by
+ intermediate transport agents.
+
+ (4) (Line Breaks) A line break in a text body, represented
+ as a CRLF sequence in the text canonical form, must be
+ represented by a (RFC 822) line break, which is also a
+ CRLF sequence, in the Quoted-Printable encoding. Since
+ the canonical representation of media types other than
+ text do not generally include the representation of
+ line breaks as CRLF sequences, no hard line breaks
+ (i.e. line breaks that are intended to be meaningful
+ and to be displayed to the user) can occur in the
+ quoted-printable encoding of such types. Sequences
+ like "=0D", "=0A", "=0A=0D" and "=0D=0A" will routinely
+ appear in non-text data represented in quoted-
+ printable, of course.
+
+ Note that many implementations may elect to encode the
+ local representation of various content types directly
+ rather than converting to canonical form first,
+ encoding, and then converting back to local
+ representation. In particular, this may apply to plain
+ text material on systems that use newline conventions
+ other than a CRLF terminator sequence. Such an
+ implementation optimization is permissible, but only
+ when the combined canonicalization-encoding step is
+ equivalent to performing the three steps separately.
+
+ (5) (Soft Line Breaks) The Quoted-Printable encoding
+ REQUIRES that encoded lines be no more than 76
+ characters long. If longer lines are to be encoded
+ with the Quoted-Printable encoding, "soft" line breaks
+
+
+
+Freed & Borenstein Standards Track [Page 20]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ must be used. An equal sign as the last character on a
+ encoded line indicates such a non-significant ("soft")
+ line break in the encoded text.
+
+ Thus if the "raw" form of the line is a single unencoded line that
+ says:
+
+ Now's the time for all folk to come to the aid of their country.
+
+ This can be represented, in the Quoted-Printable encoding, as:
+
+ Now's the time =
+ for all folk to come=
+ to the aid of their country.
+
+ This provides a mechanism with which long lines are encoded in such a
+ way as to be restored by the user agent. The 76 character limit does
+ not count the trailing CRLF, but counts all other characters,
+ including any equal signs.
+
+ Since the hyphen character ("-") may be represented as itself in the
+ Quoted-Printable encoding, care must be taken, when encapsulating a
+ quoted-printable encoded body inside one or more multipart entities,
+ to ensure that the boundary delimiter does not appear anywhere in the
+ encoded body. (A good strategy is to choose a boundary that includes
+ a character sequence such as "=_" which can never appear in a
+ quoted-printable body. See the definition of multipart messages in
+ RFC 2046.)
+
+ NOTE: The quoted-printable encoding represents something of a
+ compromise between readability and reliability in transport. Bodies
+ encoded with the quoted-printable encoding will work reliably over
+ most mail gateways, but may not work perfectly over a few gateways,
+ notably those involving translation into EBCDIC. A higher level of
+ confidence is offered by the base64 Content-Transfer-Encoding. A way
+ to get reasonably reliable transport through EBCDIC gateways is to
+ also quote the US-ASCII characters
+
+ !"#$@[\]^`{|}~
+
+ according to rule #1.
+
+ Because quoted-printable data is generally assumed to be line-
+ oriented, it is to be expected that the representation of the breaks
+ between the lines of quoted-printable data may be altered in
+ transport, in the same manner that plain text mail has always been
+ altered in Internet mail when passing between systems with differing
+ newline conventions. If such alterations are likely to constitute a
+
+
+
+Freed & Borenstein Standards Track [Page 21]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ corruption of the data, it is probably more sensible to use the
+ base64 encoding rather than the quoted-printable encoding.
+
+ NOTE: Several kinds of substrings cannot be generated according to
+ the encoding rules for the quoted-printable content-transfer-
+ encoding, and hence are formally illegal if they appear in the output
+ of a quoted-printable encoder. This note enumerates these cases and
+ suggests ways to handle such illegal substrings if any are
+ encountered in quoted-printable data that is to be decoded.
+
+ (1) An "=" followed by two hexadecimal digits, one or both
+ of which are lowercase letters in "abcdef", is formally
+ illegal. A robust implementation might choose to
+ recognize them as the corresponding uppercase letters.
+
+ (2) An "=" followed by a character that is neither a
+ hexadecimal digit (including "abcdef") nor the CR
+ character of a CRLF pair is illegal. This case can be
+ the result of US-ASCII text having been included in a
+ quoted-printable part of a message without itself
+ having been subjected to quoted-printable encoding. A
+ reasonable approach by a robust implementation might be
+ to include the "=" character and the following
+ character in the decoded data without any
+ transformation and, if possible, indicate to the user
+ that proper decoding was not possible at this point in
+ the data.
+
+ (3) An "=" cannot be the ultimate or penultimate character
+ in an encoded object. This could be handled as in case
+ (2) above.
+
+ (4) Control characters other than TAB, or CR and LF as
+ parts of CRLF pairs, must not appear. The same is true
+ for octets with decimal values greater than 126. If
+ found in incoming quoted-printable data by a decoder, a
+ robust implementation might exclude them from the
+ decoded data and warn the user that illegal characters
+ were discovered.
+
+ (5) Encoded lines must not be longer than 76 characters,
+ not counting the trailing CRLF. If longer lines are
+ found in incoming, encoded data, a robust
+ implementation might nevertheless decode the lines, and
+ might report the erroneous encoding to the user.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 22]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ WARNING TO IMPLEMENTORS: If binary data is encoded in quoted-
+ printable, care must be taken to encode CR and LF characters as "=0D"
+ and "=0A", respectively. In particular, a CRLF sequence in binary
+ data should be encoded as "=0D=0A". Otherwise, if CRLF were
+ represented as a hard line break, it might be incorrectly decoded on
+ platforms with different line break conventions.
+
+ For formalists, the syntax of quoted-printable data is described by
+ the following grammar:
+
+ quoted-printable := qp-line *(CRLF qp-line)
+
+ qp-line := *(qp-segment transport-padding CRLF)
+ qp-part transport-padding
+
+ qp-part := qp-section
+ ; Maximum length of 76 characters
+
+ qp-segment := qp-section *(SPACE / TAB) "="
+ ; Maximum length of 76 characters
+
+ qp-section := [*(ptext / SPACE / TAB) ptext]
+
+ ptext := hex-octet / safe-char
+
+ safe-char := <any octet with decimal value of 33 through
+ 60 inclusive, and 62 through 126>
+ ; Characters not listed as "mail-safe" in
+ ; RFC 2049 are also not recommended.
+
+ hex-octet := "=" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
+ ; Octet must be used for characters > 127, =,
+ ; SPACEs or TABs at the ends of lines, and is
+ ; recommended for any character not listed in
+ ; RFC 2049 as "mail-safe".
+
+ transport-padding := *LWSP-char
+ ; Composers MUST NOT generate
+ ; non-zero length transport
+ ; padding, but receivers MUST
+ ; be able to handle padding
+ ; added by message transports.
+
+ IMPORTANT: The addition of LWSP between the elements shown in this
+ BNF is NOT allowed since this BNF does not specify a structured
+ header field.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 23]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+6.8. Base64 Content-Transfer-Encoding
+
+ The Base64 Content-Transfer-Encoding is designed to represent
+ arbitrary sequences of octets in a form that need not be humanly
+ readable. The encoding and decoding algorithms are simple, but the
+ encoded data are consistently only about 33 percent larger than the
+ unencoded data. This encoding is virtually identical to the one used
+ in Privacy Enhanced Mail (PEM) applications, as defined in RFC 1421.
+
+ A 65-character subset of US-ASCII is used, enabling 6 bits to be
+ represented per printable character. (The extra 65th character, "=",
+ is used to signify a special processing function.)
+
+ NOTE: This subset has the important property that it is represented
+ identically in all versions of ISO 646, including US-ASCII, and all
+ characters in the subset are also represented identically in all
+ versions of EBCDIC. Other popular encodings, such as the encoding
+ used by the uuencode utility, Macintosh binhex 4.0 [RFC-1741], and
+ the base85 encoding specified as part of Level 2 PostScript, do not
+ share these properties, and thus do not fulfill the portability
+ requirements a binary transport encoding for mail must meet.
+
+ The encoding process represents 24-bit groups of input bits as output
+ strings of 4 encoded characters. Proceeding from left to right, a
+ 24-bit input group is formed by concatenating 3 8bit input groups.
+ These 24 bits are then treated as 4 concatenated 6-bit groups, each
+ of which is translated into a single digit in the base64 alphabet.
+ When encoding a bit stream via the base64 encoding, the bit stream
+ must be presumed to be ordered with the most-significant-bit first.
+ That is, the first bit in the stream will be the high-order bit in
+ the first 8bit byte, and the eighth bit will be the low-order bit in
+ the first 8bit byte, and so on.
+
+ Each 6-bit group is used as an index into an array of 64 printable
+ characters. The character referenced by the index is placed in the
+ output string. These characters, identified in Table 1, below, are
+ selected so as to be universally representable, and the set excludes
+ characters with particular significance to SMTP (e.g., ".", CR, LF)
+ and to the multipart boundary delimiters defined in RFC 2046 (e.g.,
+ "-").
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 24]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ Table 1: The Base64 Alphabet
+
+ Value Encoding Value Encoding Value Encoding Value Encoding
+ 0 A 17 R 34 i 51 z
+ 1 B 18 S 35 j 52 0
+ 2 C 19 T 36 k 53 1
+ 3 D 20 U 37 l 54 2
+ 4 E 21 V 38 m 55 3
+ 5 F 22 W 39 n 56 4
+ 6 G 23 X 40 o 57 5
+ 7 H 24 Y 41 p 58 6
+ 8 I 25 Z 42 q 59 7
+ 9 J 26 a 43 r 60 8
+ 10 K 27 b 44 s 61 9
+ 11 L 28 c 45 t 62 +
+ 12 M 29 d 46 u 63 /
+ 13 N 30 e 47 v
+ 14 O 31 f 48 w (pad) =
+ 15 P 32 g 49 x
+ 16 Q 33 h 50 y
+
+ The encoded output stream must be represented in lines of no more
+ than 76 characters each. All line breaks or other characters not
+ found in Table 1 must be ignored by decoding software. In base64
+ data, characters other than those in Table 1, line breaks, and other
+ white space probably indicate a transmission error, about which a
+ warning message or even a message rejection might be appropriate
+ under some circumstances.
+
+ Special processing is performed if fewer than 24 bits are available
+ at the end of the data being encoded. A full encoding quantum is
+ always completed at the end of a body. When fewer than 24 input bits
+ are available in an input group, zero bits are added (on the right)
+ to form an integral number of 6-bit groups. Padding at the end of
+ the data is performed using the "=" character. Since all base64
+ input is an integral number of octets, only the following cases can
+ arise: (1) the final quantum of encoding input is an integral
+ multiple of 24 bits; here, the final unit of encoded output will be
+ an integral multiple of 4 characters with no "=" padding, (2) the
+ final quantum of encoding input is exactly 8 bits; here, the final
+ unit of encoded output will be two characters followed by two "="
+ padding characters, or (3) the final quantum of encoding input is
+ exactly 16 bits; here, the final unit of encoded output will be three
+ characters followed by one "=" padding character.
+
+ Because it is used only for padding at the end of the data, the
+ occurrence of any "=" characters may be taken as evidence that the
+ end of the data has been reached (without truncation in transit). No
+
+
+
+Freed & Borenstein Standards Track [Page 25]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ such assurance is possible, however, when the number of octets
+ transmitted was a multiple of three and no "=" characters are
+ present.
+
+ Any characters outside of the base64 alphabet are to be ignored in
+ base64-encoded data.
+
+ Care must be taken to use the proper octets for line breaks if base64
+ encoding is applied directly to text material that has not been
+ converted to canonical form. In particular, text line breaks must be
+ converted into CRLF sequences prior to base64 encoding. The
+ important thing to note is that this may be done directly by the
+ encoder rather than in a prior canonicalization step in some
+ implementations.
+
+ NOTE: There is no need to worry about quoting potential boundary
+ delimiters within base64-encoded bodies within multipart entities
+ because no hyphen characters are used in the base64 encoding.
+
+7. Content-ID Header Field
+
+ In constructing a high-level user agent, it may be desirable to allow
+ one body to make reference to another. Accordingly, bodies may be
+ labelled using the "Content-ID" header field, which is syntactically
+ identical to the "Message-ID" header field:
+
+ id := "Content-ID" ":" msg-id
+
+ Like the Message-ID values, Content-ID values must be generated to be
+ world-unique.
+
+ The Content-ID value may be used for uniquely identifying MIME
+ entities in several contexts, particularly for caching data
+ referenced by the message/external-body mechanism. Although the
+ Content-ID header is generally optional, its use is MANDATORY in
+ implementations which generate data of the optional MIME media type
+ "message/external-body". That is, each message/external-body entity
+ must have a Content-ID field to permit caching of such data.
+
+ It is also worth noting that the Content-ID value has special
+ semantics in the case of the multipart/alternative media type. This
+ is explained in the section of RFC 2046 dealing with
+ multipart/alternative.
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 26]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+8. Content-Description Header Field
+
+ The ability to associate some descriptive information with a given
+ body is often desirable. For example, it may be useful to mark an
+ "image" body as "a picture of the Space Shuttle Endeavor." Such text
+ may be placed in the Content-Description header field. This header
+ field is always optional.
+
+ description := "Content-Description" ":" *text
+
+ The description is presumed to be given in the US-ASCII character
+ set, although the mechanism specified in RFC 2047 may be used for
+ non-US-ASCII Content-Description values.
+
+9. Additional MIME Header Fields
+
+ Future documents may elect to define additional MIME header fields
+ for various purposes. Any new header field that further describes
+ the content of a message should begin with the string "Content-" to
+ allow such fields which appear in a message header to be
+ distinguished from ordinary RFC 822 message header fields.
+
+ MIME-extension-field := <Any RFC 822 header field which
+ begins with the string
+ "Content-">
+
+10. Summary
+
+ Using the MIME-Version, Content-Type, and Content-Transfer-Encoding
+ header fields, it is possible to include, in a standardized way,
+ arbitrary types of data with RFC 822 conformant mail messages. No
+ restrictions imposed by either RFC 821 or RFC 822 are violated, and
+ care has been taken to avoid problems caused by additional
+ restrictions imposed by the characteristics of some Internet mail
+ transport mechanisms (see RFC 2049).
+
+ The next document in this set, RFC 2046, specifies the initial set of
+ media types that can be labelled and transported using these headers.
+
+11. Security Considerations
+
+ Security issues are discussed in the second document in this set, RFC
+ 2046.
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 27]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+12. Authors' Addresses
+
+ For more information, the authors of this document are best contacted
+ via Internet mail:
+
+ Ned Freed
+ Innosoft International, Inc.
+ 1050 East Garvey Avenue South
+ West Covina, CA 91790
+ USA
+
+ Phone: +1 818 919 3600
+ Fax: +1 818 919 3614
+ EMail: ned@innosoft.com
+
+
+ Nathaniel S. Borenstein
+ First Virtual Holdings
+ 25 Washington Avenue
+ Morristown, NJ 07960
+ USA
+
+ Phone: +1 201 540 8967
+ Fax: +1 201 993 3032
+ EMail: nsb@nsb.fv.com
+
+
+ MIME is a result of the work of the Internet Engineering Task Force
+ Working Group on RFC 822 Extensions. The chairman of that group,
+ Greg Vaudreuil, may be reached at:
+
+ Gregory M. Vaudreuil
+ Octel Network Services
+ 17080 Dallas Parkway
+ Dallas, TX 75248-1905
+ USA
+
+ EMail: Greg.Vaudreuil@Octel.Com
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 28]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+Appendix A -- Collected Grammar
+
+ This appendix contains the complete BNF grammar for all the syntax
+ specified by this document.
+
+ By itself, however, this grammar is incomplete. It refers by name to
+ several syntax rules that are defined by RFC 822. Rather than
+ reproduce those definitions here, and risk unintentional differences
+ between the two, this document simply refers the reader to RFC 822
+ for the remaining definitions. Wherever a term is undefined, it
+ refers to the RFC 822 definition.
+
+ attribute := token
+ ; Matching of attributes
+ ; is ALWAYS case-insensitive.
+
+ composite-type := "message" / "multipart" / extension-token
+
+ content := "Content-Type" ":" type "/" subtype
+ *(";" parameter)
+ ; Matching of media type and subtype
+ ; is ALWAYS case-insensitive.
+
+ description := "Content-Description" ":" *text
+
+ discrete-type := "text" / "image" / "audio" / "video" /
+ "application" / extension-token
+
+ encoding := "Content-Transfer-Encoding" ":" mechanism
+
+ entity-headers := [ content CRLF ]
+ [ encoding CRLF ]
+ [ id CRLF ]
+ [ description CRLF ]
+ *( MIME-extension-field CRLF )
+
+ extension-token := ietf-token / x-token
+
+ hex-octet := "=" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
+ ; Octet must be used for characters > 127, =,
+ ; SPACEs or TABs at the ends of lines, and is
+ ; recommended for any character not listed in
+ ; RFC 2049 as "mail-safe".
+
+ iana-token := <A publicly-defined extension token. Tokens
+ of this form must be registered with IANA
+ as specified in RFC 2048.>
+
+
+
+
+Freed & Borenstein Standards Track [Page 29]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ ietf-token := <An extension token defined by a
+ standards-track RFC and registered
+ with IANA.>
+
+ id := "Content-ID" ":" msg-id
+
+ mechanism := "7bit" / "8bit" / "binary" /
+ "quoted-printable" / "base64" /
+ ietf-token / x-token
+
+ MIME-extension-field := <Any RFC 822 header field which
+ begins with the string
+ "Content-">
+
+ MIME-message-headers := entity-headers
+ fields
+ version CRLF
+ ; The ordering of the header
+ ; fields implied by this BNF
+ ; definition should be ignored.
+
+ MIME-part-headers := entity-headers
+ [fields]
+ ; Any field not beginning with
+ ; "content-" can have no defined
+ ; meaning and may be ignored.
+ ; The ordering of the header
+ ; fields implied by this BNF
+ ; definition should be ignored.
+
+ parameter := attribute "=" value
+
+ ptext := hex-octet / safe-char
+
+ qp-line := *(qp-segment transport-padding CRLF)
+ qp-part transport-padding
+
+ qp-part := qp-section
+ ; Maximum length of 76 characters
+
+ qp-section := [*(ptext / SPACE / TAB) ptext]
+
+ qp-segment := qp-section *(SPACE / TAB) "="
+ ; Maximum length of 76 characters
+
+ quoted-printable := qp-line *(CRLF qp-line)
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 30]
+
+RFC 2045 Internet Message Bodies November 1996
+
+
+ safe-char := <any octet with decimal value of 33 through
+ 60 inclusive, and 62 through 126>
+ ; Characters not listed as "mail-safe" in
+ ; RFC 2049 are also not recommended.
+
+ subtype := extension-token / iana-token
+
+ token := 1*<any (US-ASCII) CHAR except SPACE, CTLs,
+ or tspecials>
+
+ transport-padding := *LWSP-char
+ ; Composers MUST NOT generate
+ ; non-zero length transport
+ ; padding, but receivers MUST
+ ; be able to handle padding
+ ; added by message transports.
+
+ tspecials := "(" / ")" / "<" / ">" / "@" /
+ "," / ";" / ":" / "\" / <">
+ "/" / "[" / "]" / "?" / "="
+ ; Must be in quoted-string,
+ ; to use within parameter values
+
+ type := discrete-type / composite-type
+
+ value := token / quoted-string
+
+ version := "MIME-Version" ":" 1*DIGIT "." 1*DIGIT
+
+ x-token := <The two characters "X-" or "x-" followed, with
+ no intervening white space, by any token>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 31]
+
diff --git a/rfc/rfc2046.txt b/rfc/rfc2046.txt
@@ -0,0 +1,2467 @@
+
+
+
+
+
+
+Network Working Group N. Freed
+Request for Comments: 2046 Innosoft
+Obsoletes: 1521, 1522, 1590 N. Borenstein
+Category: Standards Track First Virtual
+ November 1996
+
+
+ Multipurpose Internet Mail Extensions
+ (MIME) Part Two:
+ Media Types
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ STD 11, RFC 822 defines a message representation protocol specifying
+ considerable detail about US-ASCII message headers, but which leaves
+ the message content, or message body, as flat US-ASCII text. This
+ set of documents, collectively called the Multipurpose Internet Mail
+ Extensions, or MIME, redefines the format of messages to allow for
+
+ (1) textual message bodies in character sets other than
+ US-ASCII,
+
+ (2) an extensible set of different formats for non-textual
+ message bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than
+ US-ASCII.
+
+ These documents are based on earlier work documented in RFC 934, STD
+ 11, and RFC 1049, but extends and revises them. Because RFC 822 said
+ so little about message bodies, these documents are largely
+ orthogonal to (rather than a revision of) RFC 822.
+
+ The initial document in this set, RFC 2045, specifies the various
+ headers used to describe the structure of MIME messages. This second
+ document defines the general structure of the MIME media typing
+ system and defines an initial set of media types. The third document,
+ RFC 2047, describes extensions to RFC 822 to allow non-US-ASCII text
+
+
+
+Freed & Borenstein Standards Track [Page 1]
+
+RFC 2046 Media Types November 1996
+
+
+ data in Internet mail header fields. The fourth document, RFC 2048,
+ specifies various IANA registration procedures for MIME-related
+ facilities. The fifth and final document, RFC 2049, describes MIME
+ conformance criteria as well as providing some illustrative examples
+ of MIME message formats, acknowledgements, and the bibliography.
+
+ These documents are revisions of RFCs 1521 and 1522, which themselves
+ were revisions of RFCs 1341 and 1342. An appendix in RFC 2049
+ describes differences and changes from previous versions.
+
+Table of Contents
+
+ 1. Introduction ......................................... 3
+ 2. Definition of a Top-Level Media Type ................. 4
+ 3. Overview Of The Initial Top-Level Media Types ........ 4
+ 4. Discrete Media Type Values ........................... 6
+ 4.1 Text Media Type ..................................... 6
+ 4.1.1 Representation of Line Breaks ..................... 7
+ 4.1.2 Charset Parameter ................................. 7
+ 4.1.3 Plain Subtype ..................................... 11
+ 4.1.4 Unrecognized Subtypes ............................. 11
+ 4.2 Image Media Type .................................... 11
+ 4.3 Audio Media Type .................................... 11
+ 4.4 Video Media Type .................................... 12
+ 4.5 Application Media Type .............................. 12
+ 4.5.1 Octet-Stream Subtype .............................. 13
+ 4.5.2 PostScript Subtype ................................ 14
+ 4.5.3 Other Application Subtypes ........................ 17
+ 5. Composite Media Type Values .......................... 17
+ 5.1 Multipart Media Type ................................ 17
+ 5.1.1 Common Syntax ..................................... 19
+ 5.1.2 Handling Nested Messages and Multiparts ........... 24
+ 5.1.3 Mixed Subtype ..................................... 24
+ 5.1.4 Alternative Subtype ............................... 24
+ 5.1.5 Digest Subtype .................................... 26
+ 5.1.6 Parallel Subtype .................................. 27
+ 5.1.7 Other Multipart Subtypes .......................... 28
+ 5.2 Message Media Type .................................. 28
+ 5.2.1 RFC822 Subtype .................................... 28
+ 5.2.2 Partial Subtype ................................... 29
+ 5.2.2.1 Message Fragmentation and Reassembly ............ 30
+ 5.2.2.2 Fragmentation and Reassembly Example ............ 31
+ 5.2.3 External-Body Subtype ............................. 33
+ 5.2.4 Other Message Subtypes ............................ 40
+ 6. Experimental Media Type Values ....................... 40
+ 7. Summary .............................................. 41
+ 8. Security Considerations .............................. 41
+ 9. Authors' Addresses ................................... 42
+
+
+
+Freed & Borenstein Standards Track [Page 2]
+
+RFC 2046 Media Types November 1996
+
+
+ A. Collected Grammar .................................... 43
+
+1. Introduction
+
+ The first document in this set, RFC 2045, defines a number of header
+ fields, including Content-Type. The Content-Type field is used to
+ specify the nature of the data in the body of a MIME entity, by
+ giving media type and subtype identifiers, and by providing auxiliary
+ information that may be required for certain media types. After the
+ type and subtype names, the remainder of the header field is simply a
+ set of parameters, specified in an attribute/value notation. The
+ ordering of parameters is not significant.
+
+ In general, the top-level media type is used to declare the general
+ type of data, while the subtype specifies a specific format for that
+ type of data. Thus, a media type of "image/xyz" is enough to tell a
+ user agent that the data is an image, even if the user agent has no
+ knowledge of the specific image format "xyz". Such information can
+ be used, for example, to decide whether or not to show a user the raw
+ data from an unrecognized subtype -- such an action might be
+ reasonable for unrecognized subtypes of "text", but not for
+ unrecognized subtypes of "image" or "audio". For this reason,
+ registered subtypes of "text", "image", "audio", and "video" should
+ not contain embedded information that is really of a different type.
+ Such compound formats should be represented using the "multipart" or
+ "application" types.
+
+ Parameters are modifiers of the media subtype, and as such do not
+ fundamentally affect the nature of the content. The set of
+ meaningful parameters depends on the media type and subtype. Most
+ parameters are associated with a single specific subtype. However, a
+ given top-level media type may define parameters which are applicable
+ to any subtype of that type. Parameters may be required by their
+ defining media type or subtype or they may be optional. MIME
+ implementations must also ignore any parameters whose names they do
+ not recognize.
+
+ MIME's Content-Type header field and media type mechanism has been
+ carefully designed to be extensible, and it is expected that the set
+ of media type/subtype pairs and their associated parameters will grow
+ significantly over time. Several other MIME facilities, such as
+ transfer encodings and "message/external-body" access types, are
+ likely to have new values defined over time. In order to ensure that
+ the set of such values is developed in an orderly, well-specified,
+ and public manner, MIME sets up a registration process which uses the
+ Internet Assigned Numbers Authority (IANA) as a central registry for
+ MIME's various areas of extensibility. The registration process for
+ these areas is described in a companion document, RFC 2048.
+
+
+
+Freed & Borenstein Standards Track [Page 3]
+
+RFC 2046 Media Types November 1996
+
+
+ The initial seven standard top-level media type are defined and
+ described in the remainder of this document.
+
+2. Definition of a Top-Level Media Type
+
+ The definition of a top-level media type consists of:
+
+ (1) a name and a description of the type, including
+ criteria for whether a particular type would qualify
+ under that type,
+
+ (2) the names and definitions of parameters, if any, which
+ are defined for all subtypes of that type (including
+ whether such parameters are required or optional),
+
+ (3) how a user agent and/or gateway should handle unknown
+ subtypes of this type,
+
+ (4) general considerations on gatewaying entities of this
+ top-level type, if any, and
+
+ (5) any restrictions on content-transfer-encodings for
+ entities of this top-level type.
+
+3. Overview Of The Initial Top-Level Media Types
+
+ The five discrete top-level media types are:
+
+ (1) text -- textual information. The subtype "plain" in
+ particular indicates plain text containing no
+ formatting commands or directives of any sort. Plain
+ text is intended to be displayed "as-is". No special
+ software is required to get the full meaning of the
+ text, aside from support for the indicated character
+ set. Other subtypes are to be used for enriched text in
+ forms where application software may enhance the
+ appearance of the text, but such software must not be
+ required in order to get the general idea of the
+ content. Possible subtypes of "text" thus include any
+ word processor format that can be read without
+ resorting to software that understands the format. In
+ particular, formats that employ embeddded binary
+ formatting information are not considered directly
+ readable. A very simple and portable subtype,
+ "richtext", was defined in RFC 1341, with a further
+ revision in RFC 1896 under the name "enriched".
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 4]
+
+RFC 2046 Media Types November 1996
+
+
+ (2) image -- image data. "Image" requires a display device
+ (such as a graphical display, a graphics printer, or a
+ FAX machine) to view the information. An initial
+ subtype is defined for the widely-used image format
+ JPEG. . subtypes are defined for two widely-used image
+ formats, jpeg and gif.
+
+ (3) audio -- audio data. "Audio" requires an audio output
+ device (such as a speaker or a telephone) to "display"
+ the contents. An initial subtype "basic" is defined in
+ this document.
+
+ (4) video -- video data. "Video" requires the capability
+ to display moving images, typically including
+ specialized hardware and software. An initial subtype
+ "mpeg" is defined in this document.
+
+ (5) application -- some other kind of data, typically
+ either uninterpreted binary data or information to be
+ processed by an application. The subtype "octet-
+ stream" is to be used in the case of uninterpreted
+ binary data, in which case the simplest recommended
+ action is to offer to write the information into a file
+ for the user. The "PostScript" subtype is also defined
+ for the transport of PostScript material. Other
+ expected uses for "application" include spreadsheets,
+ data for mail-based scheduling systems, and languages
+ for "active" (computational) messaging, and word
+ processing formats that are not directly readable.
+ Note that security considerations may exist for some
+ types of application data, most notably
+ "application/PostScript" and any form of active
+ messaging. These issues are discussed later in this
+ document.
+
+ The two composite top-level media types are:
+
+ (1) multipart -- data consisting of multiple entities of
+ independent data types. Four subtypes are initially
+ defined, including the basic "mixed" subtype specifying
+ a generic mixed set of parts, "alternative" for
+ representing the same data in multiple formats,
+ "parallel" for parts intended to be viewed
+ simultaneously, and "digest" for multipart entities in
+ which each part has a default type of "message/rfc822".
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 5]
+
+RFC 2046 Media Types November 1996
+
+
+ (2) message -- an encapsulated message. A body of media
+ type "message" is itself all or a portion of some kind
+ of message object. Such objects may or may not in turn
+ contain other entities. The "rfc822" subtype is used
+ when the encapsulated content is itself an RFC 822
+ message. The "partial" subtype is defined for partial
+ RFC 822 messages, to permit the fragmented transmission
+ of bodies that are thought to be too large to be passed
+ through transport facilities in one piece. Another
+ subtype, "external-body", is defined for specifying
+ large bodies by reference to an external data source.
+
+ It should be noted that the list of media type values given here may
+ be augmented in time, via the mechanisms described above, and that
+ the set of subtypes is expected to grow substantially.
+
+4. Discrete Media Type Values
+
+ Five of the seven initial media type values refer to discrete bodies.
+ The content of these types must be handled by non-MIME mechanisms;
+ they are opaque to MIME processors.
+
+4.1. Text Media Type
+
+ The "text" media type is intended for sending material which is
+ principally textual in form. A "charset" parameter may be used to
+ indicate the character set of the body text for "text" subtypes,
+ notably including the subtype "text/plain", which is a generic
+ subtype for plain text. Plain text does not provide for or allow
+ formatting commands, font attribute specifications, processing
+ instructions, interpretation directives, or content markup. Plain
+ text is seen simply as a linear sequence of characters, possibly
+ interrupted by line breaks or page breaks. Plain text may allow the
+ stacking of several characters in the same position in the text.
+ Plain text in scripts like Arabic and Hebrew may also include
+ facilitites that allow the arbitrary mixing of text segments with
+ opposite writing directions.
+
+ Beyond plain text, there are many formats for representing what might
+ be known as "rich text". An interesting characteristic of many such
+ representations is that they are to some extent readable even without
+ the software that interprets them. It is useful, then, to
+ distinguish them, at the highest level, from such unreadable data as
+ images, audio, or text represented in an unreadable form. In the
+ absence of appropriate interpretation software, it is reasonable to
+ show subtypes of "text" to the user, while it is not reasonable to do
+ so with most nontextual data. Such formatted textual data should be
+ represented using subtypes of "text".
+
+
+
+Freed & Borenstein Standards Track [Page 6]
+
+RFC 2046 Media Types November 1996
+
+
+4.1.1. Representation of Line Breaks
+
+ The canonical form of any MIME "text" subtype MUST always represent a
+ line break as a CRLF sequence. Similarly, any occurrence of CRLF in
+ MIME "text" MUST represent a line break. Use of CR and LF outside of
+ line break sequences is also forbidden.
+
+ This rule applies regardless of format or character set or sets
+ involved.
+
+ NOTE: The proper interpretation of line breaks when a body is
+ displayed depends on the media type. In particular, while it is
+ appropriate to treat a line break as a transition to a new line when
+ displaying a "text/plain" body, this treatment is actually incorrect
+ for other subtypes of "text" like "text/enriched" [RFC-1896].
+ Similarly, whether or not line breaks should be added during display
+ operations is also a function of the media type. It should not be
+ necessary to add any line breaks to display "text/plain" correctly,
+ whereas proper display of "text/enriched" requires the appropriate
+ addition of line breaks.
+
+ NOTE: Some protocols defines a maximum line length. E.g. SMTP [RFC-
+ 821] allows a maximum of 998 octets before the next CRLF sequence.
+ To be transported by such protocols, data which includes too long
+ segments without CRLF sequences must be encoded with a suitable
+ content-transfer-encoding.
+
+4.1.2. Charset Parameter
+
+ A critical parameter that may be specified in the Content-Type field
+ for "text/plain" data is the character set. This is specified with a
+ "charset" parameter, as in:
+
+ Content-type: text/plain; charset=iso-8859-1
+
+ Unlike some other parameter values, the values of the charset
+ parameter are NOT case sensitive. The default character set, which
+ must be assumed in the absence of a charset parameter, is US-ASCII.
+
+ The specification for any future subtypes of "text" must specify
+ whether or not they will also utilize a "charset" parameter, and may
+ possibly restrict its values as well. For other subtypes of "text"
+ than "text/plain", the semantics of the "charset" parameter should be
+ defined to be identical to those specified here for "text/plain",
+ i.e., the body consists entirely of characters in the given charset.
+ In particular, definers of future "text" subtypes should pay close
+ attention to the implications of multioctet character sets for their
+ subtype definitions.
+
+
+
+Freed & Borenstein Standards Track [Page 7]
+
+RFC 2046 Media Types November 1996
+
+
+ The charset parameter for subtypes of "text" gives a name of a
+ character set, as "character set" is defined in RFC 2045. The rules
+ regarding line breaks detailed in the previous section must also be
+ observed -- a character set whose definition does not conform to
+ these rules cannot be used in a MIME "text" subtype.
+
+ An initial list of predefined character set names can be found at the
+ end of this section. Additional character sets may be registered
+ with IANA.
+
+ Other media types than subtypes of "text" might choose to employ the
+ charset parameter as defined here, but with the CRLF/line break
+ restriction removed. Therefore, all character sets that conform to
+ the general definition of "character set" in RFC 2045 can be
+ registered for MIME use.
+
+ Note that if the specified character set includes 8-bit characters
+ and such characters are used in the body, a Content-Transfer-Encoding
+ header field and a corresponding encoding on the data are required in
+ order to transmit the body via some mail transfer protocols, such as
+ SMTP [RFC-821].
+
+ The default character set, US-ASCII, has been the subject of some
+ confusion and ambiguity in the past. Not only were there some
+ ambiguities in the definition, there have been wide variations in
+ practice. In order to eliminate such ambiguity and variations in the
+ future, it is strongly recommended that new user agents explicitly
+ specify a character set as a media type parameter in the Content-Type
+ header field. "US-ASCII" does not indicate an arbitrary 7-bit
+ character set, but specifies that all octets in the body must be
+ interpreted as characters according to the US-ASCII character set.
+ National and application-oriented versions of ISO 646 [ISO-646] are
+ usually NOT identical to US-ASCII, and in that case their use in
+ Internet mail is explicitly discouraged. The omission of the ISO 646
+ character set from this document is deliberate in this regard. The
+ character set name of "US-ASCII" explicitly refers to the character
+ set defined in ANSI X3.4-1986 [US- ASCII]. The new international
+ reference version (IRV) of the 1991 edition of ISO 646 is identical
+ to US-ASCII. The character set name "ASCII" is reserved and must not
+ be used for any purpose.
+
+ NOTE: RFC 821 explicitly specifies "ASCII", and references an earlier
+ version of the American Standard. Insofar as one of the purposes of
+ specifying a media type and character set is to permit the receiver
+ to unambiguously determine how the sender intended the coded message
+ to be interpreted, assuming anything other than "strict ASCII" as the
+ default would risk unintentional and incompatible changes to the
+ semantics of messages now being transmitted. This also implies that
+
+
+
+Freed & Borenstein Standards Track [Page 8]
+
+RFC 2046 Media Types November 1996
+
+
+ messages containing characters coded according to other versions of
+ ISO 646 than US-ASCII and the 1991 IRV, or using code-switching
+ procedures (e.g., those of ISO 2022), as well as 8bit or multiple
+ octet character encodings MUST use an appropriate character set
+ specification to be consistent with MIME.
+
+ The complete US-ASCII character set is listed in ANSI X3.4- 1986.
+ Note that the control characters including DEL (0-31, 127) have no
+ defined meaning in apart from the combination CRLF (US-ASCII values
+ 13 and 10) indicating a new line. Two of the characters have de
+ facto meanings in wide use: FF (12) often means "start subsequent
+ text on the beginning of a new page"; and TAB or HT (9) often (though
+ not always) means "move the cursor to the next available column after
+ the current position where the column number is a multiple of 8
+ (counting the first column as column 0)." Aside from these
+ conventions, any use of the control characters or DEL in a body must
+ either occur
+
+ (1) because a subtype of text other than "plain"
+ specifically assigns some additional meaning, or
+
+ (2) within the context of a private agreement between the
+ sender and recipient. Such private agreements are
+ discouraged and should be replaced by the other
+ capabilities of this document.
+
+ NOTE: An enormous proliferation of character sets exist beyond US-
+ ASCII. A large number of partially or totally overlapping character
+ sets is NOT a good thing. A SINGLE character set that can be used
+ universally for representing all of the world's languages in Internet
+ mail would be preferrable. Unfortunately, existing practice in
+ several communities seems to point to the continued use of multiple
+ character sets in the near future. A small number of standard
+ character sets are, therefore, defined for Internet use in this
+ document.
+
+ The defined charset values are:
+
+ (1) US-ASCII -- as defined in ANSI X3.4-1986 [US-ASCII].
+
+ (2) ISO-8859-X -- where "X" is to be replaced, as
+ necessary, for the parts of ISO-8859 [ISO-8859]. Note
+ that the ISO 646 character sets have deliberately been
+ omitted in favor of their 8859 replacements, which are
+ the designated character sets for Internet mail. As of
+ the publication of this document, the legitimate values
+ for "X" are the digits 1 through 10.
+
+
+
+
+Freed & Borenstein Standards Track [Page 9]
+
+RFC 2046 Media Types November 1996
+
+
+ Characters in the range 128-159 has no assigned meaning in ISO-8859-
+ X. Characters with values below 128 in ISO-8859-X have the same
+ assigned meaning as they do in US-ASCII.
+
+ Part 6 of ISO 8859 (Latin/Arabic alphabet) and part 8 (Latin/Hebrew
+ alphabet) includes both characters for which the normal writing
+ direction is right to left and characters for which it is left to
+ right, but do not define a canonical ordering method for representing
+ bi-directional text. The charset values "ISO-8859-6" and "ISO-8859-
+ 8", however, specify that the visual method is used [RFC-1556].
+
+ All of these character sets are used as pure 7bit or 8bit sets
+ without any shift or escape functions. The meaning of shift and
+ escape sequences in these character sets is not defined.
+
+ The character sets specified above are the ones that were relatively
+ uncontroversial during the drafting of MIME. This document does not
+ endorse the use of any particular character set other than US-ASCII,
+ and recognizes that the future evolution of world character sets
+ remains unclear.
+
+ Note that the character set used, if anything other than US- ASCII,
+ must always be explicitly specified in the Content-Type field.
+
+ No character set name other than those defined above may be used in
+ Internet mail without the publication of a formal specification and
+ its registration with IANA, or by private agreement, in which case
+ the character set name must begin with "X-".
+
+ Implementors are discouraged from defining new character sets unless
+ absolutely necessary.
+
+ The "charset" parameter has been defined primarily for the purpose of
+ textual data, and is described in this section for that reason.
+ However, it is conceivable that non-textual data might also wish to
+ specify a charset value for some purpose, in which case the same
+ syntax and values should be used.
+
+ In general, composition software should always use the "lowest common
+ denominator" character set possible. For example, if a body contains
+ only US-ASCII characters, it SHOULD be marked as being in the US-
+ ASCII character set, not ISO-8859-1, which, like all the ISO-8859
+ family of character sets, is a superset of US-ASCII. More generally,
+ if a widely-used character set is a subset of another character set,
+ and a body contains only characters in the widely-used subset, it
+ should be labelled as being in that subset. This will increase the
+ chances that the recipient will be able to view the resulting entity
+ correctly.
+
+
+
+Freed & Borenstein Standards Track [Page 10]
+
+RFC 2046 Media Types November 1996
+
+
+4.1.3. Plain Subtype
+
+ The simplest and most important subtype of "text" is "plain". This
+ indicates plain text that does not contain any formatting commands or
+ directives. Plain text is intended to be displayed "as-is", that is,
+ no interpretation of embedded formatting commands, font attribute
+ specifications, processing instructions, interpretation directives,
+ or content markup should be necessary for proper display. The
+ default media type of "text/plain; charset=us-ascii" for Internet
+ mail describes existing Internet practice. That is, it is the type
+ of body defined by RFC 822.
+
+ No other "text" subtype is defined by this document.
+
+4.1.4. Unrecognized Subtypes
+
+ Unrecognized subtypes of "text" should be treated as subtype "plain"
+ as long as the MIME implementation knows how to handle the charset.
+ Unrecognized subtypes which also specify an unrecognized charset
+ should be treated as "application/octet- stream".
+
+4.2. Image Media Type
+
+ A media type of "image" indicates that the body contains an image.
+ The subtype names the specific image format. These names are not
+ case sensitive. An initial subtype is "jpeg" for the JPEG format
+ using JFIF encoding [JPEG].
+
+ The list of "image" subtypes given here is neither exclusive nor
+ exhaustive, and is expected to grow as more types are registered with
+ IANA, as described in RFC 2048.
+
+ Unrecognized subtypes of "image" should at a miniumum be treated as
+ "application/octet-stream". Implementations may optionally elect to
+ pass subtypes of "image" that they do not specifically recognize to a
+ secure and robust general-purpose image viewing application, if such
+ an application is available.
+
+ NOTE: Using of a generic-purpose image viewing application this way
+ inherits the security problems of the most dangerous type supported
+ by the application.
+
+4.3. Audio Media Type
+
+ A media type of "audio" indicates that the body contains audio data.
+ Although there is not yet a consensus on an "ideal" audio format for
+ use with computers, there is a pressing need for a format capable of
+ providing interoperable behavior.
+
+
+
+Freed & Borenstein Standards Track [Page 11]
+
+RFC 2046 Media Types November 1996
+
+
+ The initial subtype of "basic" is specified to meet this requirement
+ by providing an absolutely minimal lowest common denominator audio
+ format. It is expected that richer formats for higher quality and/or
+ lower bandwidth audio will be defined by a later document.
+
+ The content of the "audio/basic" subtype is single channel audio
+ encoded using 8bit ISDN mu-law [PCM] at a sample rate of 8000 Hz.
+
+ Unrecognized subtypes of "audio" should at a miniumum be treated as
+ "application/octet-stream". Implementations may optionally elect to
+ pass subtypes of "audio" that they do not specifically recognize to a
+ robust general-purpose audio playing application, if such an
+ application is available.
+
+4.4. Video Media Type
+
+ A media type of "video" indicates that the body contains a time-
+ varying-picture image, possibly with color and coordinated sound.
+ The term 'video' is used in its most generic sense, rather than with
+ reference to any particular technology or format, and is not meant to
+ preclude subtypes such as animated drawings encoded compactly. The
+ subtype "mpeg" refers to video coded according to the MPEG standard
+ [MPEG].
+
+ Note that although in general this document strongly discourages the
+ mixing of multiple media in a single body, it is recognized that many
+ so-called video formats include a representation for synchronized
+ audio, and this is explicitly permitted for subtypes of "video".
+
+ Unrecognized subtypes of "video" should at a minumum be treated as
+ "application/octet-stream". Implementations may optionally elect to
+ pass subtypes of "video" that they do not specifically recognize to a
+ robust general-purpose video display application, if such an
+ application is available.
+
+4.5. Application Media Type
+
+ The "application" media type is to be used for discrete data which do
+ not fit in any of the other categories, and particularly for data to
+ be processed by some type of application program. This is
+ information which must be processed by an application before it is
+ viewable or usable by a user. Expected uses for the "application"
+ media type include file transfer, spreadsheets, data for mail-based
+ scheduling systems, and languages for "active" (computational)
+ material. (The latter, in particular, can pose security problems
+ which must be understood by implementors, and are considered in
+ detail in the discussion of the "application/PostScript" media type.)
+
+
+
+
+Freed & Borenstein Standards Track [Page 12]
+
+RFC 2046 Media Types November 1996
+
+
+ For example, a meeting scheduler might define a standard
+ representation for information about proposed meeting dates. An
+ intelligent user agent would use this information to conduct a dialog
+ with the user, and might then send additional material based on that
+ dialog. More generally, there have been several "active" messaging
+ languages developed in which programs in a suitably specialized
+ language are transported to a remote location and automatically run
+ in the recipient's environment.
+
+ Such applications may be defined as subtypes of the "application"
+ media type. This document defines two subtypes:
+
+ octet-stream, and PostScript.
+
+ The subtype of "application" will often be either the name or include
+ part of the name of the application for which the data are intended.
+ This does not mean, however, that any application program name may be
+ used freely as a subtype of "application".
+
+4.5.1. Octet-Stream Subtype
+
+ The "octet-stream" subtype is used to indicate that a body contains
+ arbitrary binary data. The set of currently defined parameters is:
+
+ (1) TYPE -- the general type or category of binary data.
+ This is intended as information for the human recipient
+ rather than for any automatic processing.
+
+ (2) PADDING -- the number of bits of padding that were
+ appended to the bit-stream comprising the actual
+ contents to produce the enclosed 8bit byte-oriented
+ data. This is useful for enclosing a bit-stream in a
+ body when the total number of bits is not a multiple of
+ 8.
+
+ Both of these parameters are optional.
+
+ An additional parameter, "CONVERSIONS", was defined in RFC 1341 but
+ has since been removed. RFC 1341 also defined the use of a "NAME"
+ parameter which gave a suggested file name to be used if the data
+ were to be written to a file. This has been deprecated in
+ anticipation of a separate Content-Disposition header field, to be
+ defined in a subsequent RFC.
+
+ The recommended action for an implementation that receives an
+ "application/octet-stream" entity is to simply offer to put the data
+ in a file, with any Content-Transfer-Encoding undone, or perhaps to
+ use it as input to a user-specified process.
+
+
+
+Freed & Borenstein Standards Track [Page 13]
+
+RFC 2046 Media Types November 1996
+
+
+ To reduce the danger of transmitting rogue programs, it is strongly
+ recommended that implementations NOT implement a path-search
+ mechanism whereby an arbitrary program named in the Content-Type
+ parameter (e.g., an "interpreter=" parameter) is found and executed
+ using the message body as input.
+
+4.5.2. PostScript Subtype
+
+ A media type of "application/postscript" indicates a PostScript
+ program. Currently two variants of the PostScript language are
+ allowed; the original level 1 variant is described in [POSTSCRIPT]
+ and the more recent level 2 variant is described in [POSTSCRIPT2].
+
+ PostScript is a registered trademark of Adobe Systems, Inc. Use of
+ the MIME media type "application/postscript" implies recognition of
+ that trademark and all the rights it entails.
+
+ The PostScript language definition provides facilities for internal
+ labelling of the specific language features a given program uses.
+ This labelling, called the PostScript document structuring
+ conventions, or DSC, is very general and provides substantially more
+ information than just the language level. The use of document
+ structuring conventions, while not required, is strongly recommended
+ as an aid to interoperability. Documents which lack proper
+ structuring conventions cannot be tested to see whether or not they
+ will work in a given environment. As such, some systems may assume
+ the worst and refuse to process unstructured documents.
+
+ The execution of general-purpose PostScript interpreters entails
+ serious security risks, and implementors are discouraged from simply
+ sending PostScript bodies to "off- the-shelf" interpreters. While it
+ is usually safe to send PostScript to a printer, where the potential
+ for harm is greatly constrained by typical printer environments,
+ implementors should consider all of the following before they add
+ interactive display of PostScript bodies to their MIME readers.
+
+ The remainder of this section outlines some, though probably not all,
+ of the possible problems with the transport of PostScript entities.
+
+ (1) Dangerous operations in the PostScript language
+ include, but may not be limited to, the PostScript
+ operators "deletefile", "renamefile", "filenameforall",
+ and "file". "File" is only dangerous when applied to
+ something other than standard input or output.
+ Implementations may also define additional nonstandard
+ file operators; these may also pose a threat to
+ security. "Filenameforall", the wildcard file search
+ operator, may appear at first glance to be harmless.
+
+
+
+Freed & Borenstein Standards Track [Page 14]
+
+RFC 2046 Media Types November 1996
+
+
+ Note, however, that this operator has the potential to
+ reveal information about what files the recipient has
+ access to, and this information may itself be
+ sensitive. Message senders should avoid the use of
+ potentially dangerous file operators, since these
+ operators are quite likely to be unavailable in secure
+ PostScript implementations. Message receiving and
+ displaying software should either completely disable
+ all potentially dangerous file operators or take
+ special care not to delegate any special authority to
+ their operation. These operators should be viewed as
+ being done by an outside agency when interpreting
+ PostScript documents. Such disabling and/or checking
+ should be done completely outside of the reach of the
+ PostScript language itself; care should be taken to
+ insure that no method exists for re-enabling full-
+ function versions of these operators.
+
+ (2) The PostScript language provides facilities for exiting
+ the normal interpreter, or server, loop. Changes made
+ in this "outer" environment are customarily retained
+ across documents, and may in some cases be retained
+ semipermanently in nonvolatile memory. The operators
+ associated with exiting the interpreter loop have the
+ potential to interfere with subsequent document
+ processing. As such, their unrestrained use
+ constitutes a threat of service denial. PostScript
+ operators that exit the interpreter loop include, but
+ may not be limited to, the exitserver and startjob
+ operators. Message sending software should not
+ generate PostScript that depends on exiting the
+ interpreter loop to operate, since the ability to exit
+ will probably be unavailable in secure PostScript
+ implementations. Message receiving and displaying
+ software should completely disable the ability to make
+ retained changes to the PostScript environment by
+ eliminating or disabling the "startjob" and
+ "exitserver" operations. If these operations cannot be
+ eliminated or completely disabled the password
+ associated with them should at least be set to a hard-
+ to-guess value.
+
+ (3) PostScript provides operators for setting system-wide
+ and device-specific parameters. These parameter
+ settings may be retained across jobs and may
+ potentially pose a threat to the correct operation of
+ the interpreter. The PostScript operators that set
+ system and device parameters include, but may not be
+
+
+
+Freed & Borenstein Standards Track [Page 15]
+
+RFC 2046 Media Types November 1996
+
+
+ limited to, the "setsystemparams" and "setdevparams"
+ operators. Message sending software should not
+ generate PostScript that depends on the setting of
+ system or device parameters to operate correctly. The
+ ability to set these parameters will probably be
+ unavailable in secure PostScript implementations.
+ Message receiving and displaying software should
+ disable the ability to change system and device
+ parameters. If these operators cannot be completely
+ disabled the password associated with them should at
+ least be set to a hard-to-guess value.
+
+ (4) Some PostScript implementations provide nonstandard
+ facilities for the direct loading and execution of
+ machine code. Such facilities are quite obviously open
+ to substantial abuse. Message sending software should
+ not make use of such features. Besides being totally
+ hardware-specific, they are also likely to be
+ unavailable in secure implementations of PostScript.
+ Message receiving and displaying software should not
+ allow such operators to be used if they exist.
+
+ (5) PostScript is an extensible language, and many, if not
+ most, implementations of it provide a number of their
+ own extensions. This document does not deal with such
+ extensions explicitly since they constitute an unknown
+ factor. Message sending software should not make use
+ of nonstandard extensions; they are likely to be
+ missing from some implementations. Message receiving
+ and displaying software should make sure that any
+ nonstandard PostScript operators are secure and don't
+ present any kind of threat.
+
+ (6) It is possible to write PostScript that consumes huge
+ amounts of various system resources. It is also
+ possible to write PostScript programs that loop
+ indefinitely. Both types of programs have the
+ potential to cause damage if sent to unsuspecting
+ recipients. Message-sending software should avoid the
+ construction and dissemination of such programs, which
+ is antisocial. Message receiving and displaying
+ software should provide appropriate mechanisms to abort
+ processing after a reasonable amount of time has
+ elapsed. In addition, PostScript interpreters should be
+ limited to the consumption of only a reasonable amount
+ of any given system resource.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 16]
+
+RFC 2046 Media Types November 1996
+
+
+ (7) It is possible to include raw binary information inside
+ PostScript in various forms. This is not recommended
+ for use in Internet mail, both because it is not
+ supported by all PostScript interpreters and because it
+ significantly complicates the use of a MIME Content-
+ Transfer-Encoding. (Without such binary, PostScript
+ may typically be viewed as line-oriented data. The
+ treatment of CRLF sequences becomes extremely
+ problematic if binary and line-oriented data are mixed
+ in a single Postscript data stream.)
+
+ (8) Finally, bugs may exist in some PostScript interpreters
+ which could possibly be exploited to gain unauthorized
+ access to a recipient's system. Apart from noting this
+ possibility, there is no specific action to take to
+ prevent this, apart from the timely correction of such
+ bugs if any are found.
+
+4.5.3. Other Application Subtypes
+
+ It is expected that many other subtypes of "application" will be
+ defined in the future. MIME implementations must at a minimum treat
+ any unrecognized subtypes as being equivalent to "application/octet-
+ stream".
+
+5. Composite Media Type Values
+
+ The remaining two of the seven initial Content-Type values refer to
+ composite entities. Composite entities are handled using MIME
+ mechanisms -- a MIME processor typically handles the body directly.
+
+5.1. Multipart Media Type
+
+ In the case of multipart entities, in which one or more different
+ sets of data are combined in a single body, a "multipart" media type
+ field must appear in the entity's header. The body must then contain
+ one or more body parts, each preceded by a boundary delimiter line,
+ and the last one followed by a closing boundary delimiter line.
+ After its boundary delimiter line, each body part then consists of a
+ header area, a blank line, and a body area. Thus a body part is
+ similar to an RFC 822 message in syntax, but different in meaning.
+
+ A body part is an entity and hence is NOT to be interpreted as
+ actually being an RFC 822 message. To begin with, NO header fields
+ are actually required in body parts. A body part that starts with a
+ blank line, therefore, is allowed and is a body part for which all
+ default values are to be assumed. In such a case, the absence of a
+ Content-Type header usually indicates that the corresponding body has
+
+
+
+Freed & Borenstein Standards Track [Page 17]
+
+RFC 2046 Media Types November 1996
+
+
+ a content-type of "text/plain; charset=US-ASCII".
+
+ The only header fields that have defined meaning for body parts are
+ those the names of which begin with "Content-". All other header
+ fields may be ignored in body parts. Although they should generally
+ be retained if at all possible, they may be discarded by gateways if
+ necessary. Such other fields are permitted to appear in body parts
+ but must not be depended on. "X-" fields may be created for
+ experimental or private purposes, with the recognition that the
+ information they contain may be lost at some gateways.
+
+ NOTE: The distinction between an RFC 822 message and a body part is
+ subtle, but important. A gateway between Internet and X.400 mail,
+ for example, must be able to tell the difference between a body part
+ that contains an image and a body part that contains an encapsulated
+ message, the body of which is a JPEG image. In order to represent
+ the latter, the body part must have "Content-Type: message/rfc822",
+ and its body (after the blank line) must be the encapsulated message,
+ with its own "Content-Type: image/jpeg" header field. The use of
+ similar syntax facilitates the conversion of messages to body parts,
+ and vice versa, but the distinction between the two must be
+ understood by implementors. (For the special case in which parts
+ actually are messages, a "digest" subtype is also defined.)
+
+ As stated previously, each body part is preceded by a boundary
+ delimiter line that contains the boundary delimiter. The boundary
+ delimiter MUST NOT appear inside any of the encapsulated parts, on a
+ line by itself or as the prefix of any line. This implies that it is
+ crucial that the composing agent be able to choose and specify a
+ unique boundary parameter value that does not contain the boundary
+ parameter value of an enclosing multipart as a prefix.
+
+ All present and future subtypes of the "multipart" type must use an
+ identical syntax. Subtypes may differ in their semantics, and may
+ impose additional restrictions on syntax, but must conform to the
+ required syntax for the "multipart" type. This requirement ensures
+ that all conformant user agents will at least be able to recognize
+ and separate the parts of any multipart entity, even those of an
+ unrecognized subtype.
+
+ As stated in the definition of the Content-Transfer-Encoding field
+ [RFC 2045], no encoding other than "7bit", "8bit", or "binary" is
+ permitted for entities of type "multipart". The "multipart" boundary
+ delimiters and header fields are always represented as 7bit US-ASCII
+ in any case (though the header fields may encode non-US-ASCII header
+ text as per RFC 2047) and data within the body parts can be encoded
+ on a part-by-part basis, with Content-Transfer-Encoding fields for
+ each appropriate body part.
+
+
+
+Freed & Borenstein Standards Track [Page 18]
+
+RFC 2046 Media Types November 1996
+
+
+5.1.1. Common Syntax
+
+ This section defines a common syntax for subtypes of "multipart".
+ All subtypes of "multipart" must use this syntax. A simple example
+ of a multipart message also appears in this section. An example of a
+ more complex multipart message is given in RFC 2049.
+
+ The Content-Type field for multipart entities requires one parameter,
+ "boundary". The boundary delimiter line is then defined as a line
+ consisting entirely of two hyphen characters ("-", decimal value 45)
+ followed by the boundary parameter value from the Content-Type header
+ field, optional linear whitespace, and a terminating CRLF.
+
+ NOTE: The hyphens are for rough compatibility with the earlier RFC
+ 934 method of message encapsulation, and for ease of searching for
+ the boundaries in some implementations. However, it should be noted
+ that multipart messages are NOT completely compatible with RFC 934
+ encapsulations; in particular, they do not obey RFC 934 quoting
+ conventions for embedded lines that begin with hyphens. This
+ mechanism was chosen over the RFC 934 mechanism because the latter
+ causes lines to grow with each level of quoting. The combination of
+ this growth with the fact that SMTP implementations sometimes wrap
+ long lines made the RFC 934 mechanism unsuitable for use in the event
+ that deeply-nested multipart structuring is ever desired.
+
+ WARNING TO IMPLEMENTORS: The grammar for parameters on the Content-
+ type field is such that it is often necessary to enclose the boundary
+ parameter values in quotes on the Content-type line. This is not
+ always necessary, but never hurts. Implementors should be sure to
+ study the grammar carefully in order to avoid producing invalid
+ Content-type fields. Thus, a typical "multipart" Content-Type header
+ field might look like this:
+
+ Content-Type: multipart/mixed; boundary=gc0p4Jq0M2Yt08j34c0p
+
+ But the following is not valid:
+
+ Content-Type: multipart/mixed; boundary=gc0pJq0M:08jU534c0p
+
+ (because of the colon) and must instead be represented as
+
+ Content-Type: multipart/mixed; boundary="gc0pJq0M:08jU534c0p"
+
+ This Content-Type value indicates that the content consists of one or
+ more parts, each with a structure that is syntactically identical to
+ an RFC 822 message, except that the header area is allowed to be
+ completely empty, and that the parts are each preceded by the line
+
+
+
+
+Freed & Borenstein Standards Track [Page 19]
+
+RFC 2046 Media Types November 1996
+
+
+ --gc0pJq0M:08jU534c0p
+
+ The boundary delimiter MUST occur at the beginning of a line, i.e.,
+ following a CRLF, and the initial CRLF is considered to be attached
+ to the boundary delimiter line rather than part of the preceding
+ part. The boundary may be followed by zero or more characters of
+ linear whitespace. It is then terminated by either another CRLF and
+ the header fields for the next part, or by two CRLFs, in which case
+ there are no header fields for the next part. If no Content-Type
+ field is present it is assumed to be "message/rfc822" in a
+ "multipart/digest" and "text/plain" otherwise.
+
+ NOTE: The CRLF preceding the boundary delimiter line is conceptually
+ attached to the boundary so that it is possible to have a part that
+ does not end with a CRLF (line break). Body parts that must be
+ considered to end with line breaks, therefore, must have two CRLFs
+ preceding the boundary delimiter line, the first of which is part of
+ the preceding body part, and the second of which is part of the
+ encapsulation boundary.
+
+ Boundary delimiters must not appear within the encapsulated material,
+ and must be no longer than 70 characters, not counting the two
+ leading hyphens.
+
+ The boundary delimiter line following the last body part is a
+ distinguished delimiter that indicates that no further body parts
+ will follow. Such a delimiter line is identical to the previous
+ delimiter lines, with the addition of two more hyphens after the
+ boundary parameter value.
+
+ --gc0pJq0M:08jU534c0p--
+
+ NOTE TO IMPLEMENTORS: Boundary string comparisons must compare the
+ boundary value with the beginning of each candidate line. An exact
+ match of the entire candidate line is not required; it is sufficient
+ that the boundary appear in its entirety following the CRLF.
+
+ There appears to be room for additional information prior to the
+ first boundary delimiter line and following the final boundary
+ delimiter line. These areas should generally be left blank, and
+ implementations must ignore anything that appears before the first
+ boundary delimiter line or after the last one.
+
+ NOTE: These "preamble" and "epilogue" areas are generally not used
+ because of the lack of proper typing of these parts and the lack of
+ clear semantics for handling these areas at gateways, particularly
+ X.400 gateways. However, rather than leaving the preamble area
+ blank, many MIME implementations have found this to be a convenient
+
+
+
+Freed & Borenstein Standards Track [Page 20]
+
+RFC 2046 Media Types November 1996
+
+
+ place to insert an explanatory note for recipients who read the
+ message with pre-MIME software, since such notes will be ignored by
+ MIME-compliant software.
+
+ NOTE: Because boundary delimiters must not appear in the body parts
+ being encapsulated, a user agent must exercise care to choose a
+ unique boundary parameter value. The boundary parameter value in the
+ example above could have been the result of an algorithm designed to
+ produce boundary delimiters with a very low probability of already
+ existing in the data to be encapsulated without having to prescan the
+ data. Alternate algorithms might result in more "readable" boundary
+ delimiters for a recipient with an old user agent, but would require
+ more attention to the possibility that the boundary delimiter might
+ appear at the beginning of some line in the encapsulated part. The
+ simplest boundary delimiter line possible is something like "---",
+ with a closing boundary delimiter line of "-----".
+
+ As a very simple example, the following multipart message has two
+ parts, both of them plain text, one of them explicitly typed and one
+ of them implicitly typed:
+
+ From: Nathaniel Borenstein <nsb@bellcore.com>
+ To: Ned Freed <ned@innosoft.com>
+ Date: Sun, 21 Mar 1993 23:56:48 -0800 (PST)
+ Subject: Sample message
+ MIME-Version: 1.0
+ Content-type: multipart/mixed; boundary="simple boundary"
+
+ This is the preamble. It is to be ignored, though it
+ is a handy place for composition agents to include an
+ explanatory note to non-MIME conformant readers.
+
+ --simple boundary
+
+ This is implicitly typed plain US-ASCII text.
+ It does NOT end with a linebreak.
+ --simple boundary
+ Content-type: text/plain; charset=us-ascii
+
+ This is explicitly typed plain US-ASCII text.
+ It DOES end with a linebreak.
+
+ --simple boundary--
+
+ This is the epilogue. It is also to be ignored.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 21]
+
+RFC 2046 Media Types November 1996
+
+
+ The use of a media type of "multipart" in a body part within another
+ "multipart" entity is explicitly allowed. In such cases, for obvious
+ reasons, care must be taken to ensure that each nested "multipart"
+ entity uses a different boundary delimiter. See RFC 2049 for an
+ example of nested "multipart" entities.
+
+ The use of the "multipart" media type with only a single body part
+ may be useful in certain contexts, and is explicitly permitted.
+
+ NOTE: Experience has shown that a "multipart" media type with a
+ single body part is useful for sending non-text media types. It has
+ the advantage of providing the preamble as a place to include
+ decoding instructions. In addition, a number of SMTP gateways move
+ or remove the MIME headers, and a clever MIME decoder can take a good
+ guess at multipart boundaries even in the absence of the Content-Type
+ header and thereby successfully decode the message.
+
+ The only mandatory global parameter for the "multipart" media type is
+ the boundary parameter, which consists of 1 to 70 characters from a
+ set of characters known to be very robust through mail gateways, and
+ NOT ending with white space. (If a boundary delimiter line appears to
+ end with white space, the white space must be presumed to have been
+ added by a gateway, and must be deleted.) It is formally specified
+ by the following BNF:
+
+ boundary := 0*69<bchars> bcharsnospace
+
+ bchars := bcharsnospace / " "
+
+ bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" /
+ "+" / "_" / "," / "-" / "." /
+ "/" / ":" / "=" / "?"
+
+ Overall, the body of a "multipart" entity may be specified as
+ follows:
+
+ dash-boundary := "--" boundary
+ ; boundary taken from the value of
+ ; boundary parameter of the
+ ; Content-Type field.
+
+ multipart-body := [preamble CRLF]
+ dash-boundary transport-padding CRLF
+ body-part *encapsulation
+ close-delimiter transport-padding
+ [CRLF epilogue]
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 22]
+
+RFC 2046 Media Types November 1996
+
+
+ transport-padding := *LWSP-char
+ ; Composers MUST NOT generate
+ ; non-zero length transport
+ ; padding, but receivers MUST
+ ; be able to handle padding
+ ; added by message transports.
+
+ encapsulation := delimiter transport-padding
+ CRLF body-part
+
+ delimiter := CRLF dash-boundary
+
+ close-delimiter := delimiter "--"
+
+ preamble := discard-text
+
+ epilogue := discard-text
+
+ discard-text := *(*text CRLF) *text
+ ; May be ignored or discarded.
+
+ body-part := MIME-part-headers [CRLF *OCTET]
+ ; Lines in a body-part must not start
+ ; with the specified dash-boundary and
+ ; the delimiter must not appear anywhere
+ ; in the body part. Note that the
+ ; semantics of a body-part differ from
+ ; the semantics of a message, as
+ ; described in the text.
+
+ OCTET := <any 0-255 octet value>
+
+ IMPORTANT: The free insertion of linear-white-space and RFC 822
+ comments between the elements shown in this BNF is NOT allowed since
+ this BNF does not specify a structured header field.
+
+ NOTE: In certain transport enclaves, RFC 822 restrictions such as
+ the one that limits bodies to printable US-ASCII characters may not
+ be in force. (That is, the transport domains may exist that resemble
+ standard Internet mail transport as specified in RFC 821 and assumed
+ by RFC 822, but without certain restrictions.) The relaxation of
+ these restrictions should be construed as locally extending the
+ definition of bodies, for example to include octets outside of the
+ US-ASCII range, as long as these extensions are supported by the
+ transport and adequately documented in the Content- Transfer-Encoding
+ header field. However, in no event are headers (either message
+ headers or body part headers) allowed to contain anything other than
+ US-ASCII characters.
+
+
+
+Freed & Borenstein Standards Track [Page 23]
+
+RFC 2046 Media Types November 1996
+
+
+ NOTE: Conspicuously missing from the "multipart" type is a notion of
+ structured, related body parts. It is recommended that those wishing
+ to provide more structured or integrated multipart messaging
+ facilities should define subtypes of multipart that are syntactically
+ identical but define relationships between the various parts. For
+ example, subtypes of multipart could be defined that include a
+ distinguished part which in turn is used to specify the relationships
+ between the other parts, probably referring to them by their
+ Content-ID field. Old implementations will not recognize the new
+ subtype if this approach is used, but will treat it as
+ multipart/mixed and will thus be able to show the user the parts that
+ are recognized.
+
+5.1.2. Handling Nested Messages and Multiparts
+
+ The "message/rfc822" subtype defined in a subsequent section of this
+ document has no terminating condition other than running out of data.
+ Similarly, an improperly truncated "multipart" entity may not have
+ any terminating boundary marker, and can turn up operationally due to
+ mail system malfunctions.
+
+ It is essential that such entities be handled correctly when they are
+ themselves imbedded inside of another "multipart" structure. MIME
+ implementations are therefore required to recognize outer level
+ boundary markers at ANY level of inner nesting. It is not sufficient
+ to only check for the next expected marker or other terminating
+ condition.
+
+5.1.3. Mixed Subtype
+
+ The "mixed" subtype of "multipart" is intended for use when the body
+ parts are independent and need to be bundled in a particular order.
+ Any "multipart" subtypes that an implementation does not recognize
+ must be treated as being of subtype "mixed".
+
+5.1.4. Alternative Subtype
+
+ The "multipart/alternative" type is syntactically identical to
+ "multipart/mixed", but the semantics are different. In particular,
+ each of the body parts is an "alternative" version of the same
+ information.
+
+ Systems should recognize that the content of the various parts are
+ interchangeable. Systems should choose the "best" type based on the
+ local environment and references, in some cases even through user
+ interaction. As with "multipart/mixed", the order of body parts is
+ significant. In this case, the alternatives appear in an order of
+ increasing faithfulness to the original content. In general, the
+
+
+
+Freed & Borenstein Standards Track [Page 24]
+
+RFC 2046 Media Types November 1996
+
+
+ best choice is the LAST part of a type supported by the recipient
+ system's local environment.
+
+ "Multipart/alternative" may be used, for example, to send a message
+ in a fancy text format in such a way that it can easily be displayed
+ anywhere:
+
+ From: Nathaniel Borenstein <nsb@bellcore.com>
+ To: Ned Freed <ned@innosoft.com>
+ Date: Mon, 22 Mar 1993 09:41:09 -0800 (PST)
+ Subject: Formatted text mail
+ MIME-Version: 1.0
+ Content-Type: multipart/alternative; boundary=boundary42
+
+ --boundary42
+ Content-Type: text/plain; charset=us-ascii
+
+ ... plain text version of message goes here ...
+
+ --boundary42
+ Content-Type: text/enriched
+
+ ... RFC 1896 text/enriched version of same message
+ goes here ...
+
+ --boundary42
+ Content-Type: application/x-whatever
+
+ ... fanciest version of same message goes here ...
+
+ --boundary42--
+
+ In this example, users whose mail systems understood the
+ "application/x-whatever" format would see only the fancy version,
+ while other users would see only the enriched or plain text version,
+ depending on the capabilities of their system.
+
+ In general, user agents that compose "multipart/alternative" entities
+ must place the body parts in increasing order of preference, that is,
+ with the preferred format last. For fancy text, the sending user
+ agent should put the plainest format first and the richest format
+ last. Receiving user agents should pick and display the last format
+ they are capable of displaying. In the case where one of the
+ alternatives is itself of type "multipart" and contains unrecognized
+ sub-parts, the user agent may choose either to show that alternative,
+ an earlier alternative, or both.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 25]
+
+RFC 2046 Media Types November 1996
+
+
+ NOTE: From an implementor's perspective, it might seem more sensible
+ to reverse this ordering, and have the plainest alternative last.
+ However, placing the plainest alternative first is the friendliest
+ possible option when "multipart/alternative" entities are viewed
+ using a non-MIME-conformant viewer. While this approach does impose
+ some burden on conformant MIME viewers, interoperability with older
+ mail readers was deemed to be more important in this case.
+
+ It may be the case that some user agents, if they can recognize more
+ than one of the formats, will prefer to offer the user the choice of
+ which format to view. This makes sense, for example, if a message
+ includes both a nicely- formatted image version and an easily-edited
+ text version. What is most critical, however, is that the user not
+ automatically be shown multiple versions of the same data. Either
+ the user should be shown the last recognized version or should be
+ given the choice.
+
+ THE SEMANTICS OF CONTENT-ID IN MULTIPART/ALTERNATIVE: Each part of a
+ "multipart/alternative" entity represents the same data, but the
+ mappings between the two are not necessarily without information
+ loss. For example, information is lost when translating ODA to
+ PostScript or plain text. It is recommended that each part should
+ have a different Content-ID value in the case where the information
+ content of the two parts is not identical. And when the information
+ content is identical -- for example, where several parts of type
+ "message/external-body" specify alternate ways to access the
+ identical data -- the same Content-ID field value should be used, to
+ optimize any caching mechanisms that might be present on the
+ recipient's end. However, the Content-ID values used by the parts
+ should NOT be the same Content-ID value that describes the
+ "multipart/alternative" as a whole, if there is any such Content-ID
+ field. That is, one Content-ID value will refer to the
+ "multipart/alternative" entity, while one or more other Content-ID
+ values will refer to the parts inside it.
+
+5.1.5. Digest Subtype
+
+ This document defines a "digest" subtype of the "multipart" Content-
+ Type. This type is syntactically identical to "multipart/mixed", but
+ the semantics are different. In particular, in a digest, the default
+ Content-Type value for a body part is changed from "text/plain" to
+ "message/rfc822". This is done to allow a more readable digest
+ format that is largely compatible (except for the quoting convention)
+ with RFC 934.
+
+ Note: Though it is possible to specify a Content-Type value for a
+ body part in a digest which is other than "message/rfc822", such as a
+ "text/plain" part containing a description of the material in the
+
+
+
+Freed & Borenstein Standards Track [Page 26]
+
+RFC 2046 Media Types November 1996
+
+
+ digest, actually doing so is undesireble. The "multipart/digest"
+ Content-Type is intended to be used to send collections of messages.
+ If a "text/plain" part is needed, it should be included as a seperate
+ part of a "multipart/mixed" message.
+
+ A digest in this format might, then, look something like this:
+
+ From: Moderator-Address
+ To: Recipient-List
+ Date: Mon, 22 Mar 1994 13:34:51 +0000
+ Subject: Internet Digest, volume 42
+ MIME-Version: 1.0
+ Content-Type: multipart/mixed;
+ boundary="---- main boundary ----"
+
+ ------ main boundary ----
+
+ ...Introductory text or table of contents...
+
+ ------ main boundary ----
+ Content-Type: multipart/digest;
+ boundary="---- next message ----"
+
+ ------ next message ----
+
+ From: someone-else
+ Date: Fri, 26 Mar 1993 11:13:32 +0200
+ Subject: my opinion
+
+ ...body goes here ...
+
+ ------ next message ----
+
+ From: someone-else-again
+ Date: Fri, 26 Mar 1993 10:07:13 -0500
+ Subject: my different opinion
+
+ ... another body goes here ...
+
+ ------ next message ------
+
+ ------ main boundary ------
+
+5.1.6. Parallel Subtype
+
+ This document defines a "parallel" subtype of the "multipart"
+ Content-Type. This type is syntactically identical to
+ "multipart/mixed", but the semantics are different. In particular,
+
+
+
+Freed & Borenstein Standards Track [Page 27]
+
+RFC 2046 Media Types November 1996
+
+
+ in a parallel entity, the order of body parts is not significant.
+
+ A common presentation of this type is to display all of the parts
+ simultaneously on hardware and software that are capable of doing so.
+ However, composing agents should be aware that many mail readers will
+ lack this capability and will show the parts serially in any event.
+
+5.1.7. Other Multipart Subtypes
+
+ Other "multipart" subtypes are expected in the future. MIME
+ implementations must in general treat unrecognized subtypes of
+ "multipart" as being equivalent to "multipart/mixed".
+
+5.2. Message Media Type
+
+ It is frequently desirable, in sending mail, to encapsulate another
+ mail message. A special media type, "message", is defined to
+ facilitate this. In particular, the "rfc822" subtype of "message" is
+ used to encapsulate RFC 822 messages.
+
+ NOTE: It has been suggested that subtypes of "message" might be
+ defined for forwarded or rejected messages. However, forwarded and
+ rejected messages can be handled as multipart messages in which the
+ first part contains any control or descriptive information, and a
+ second part, of type "message/rfc822", is the forwarded or rejected
+ message. Composing rejection and forwarding messages in this manner
+ will preserve the type information on the original message and allow
+ it to be correctly presented to the recipient, and hence is strongly
+ encouraged.
+
+ Subtypes of "message" often impose restrictions on what encodings are
+ allowed. These restrictions are described in conjunction with each
+ specific subtype.
+
+ Mail gateways, relays, and other mail handling agents are commonly
+ known to alter the top-level header of an RFC 822 message. In
+ particular, they frequently add, remove, or reorder header fields.
+ These operations are explicitly forbidden for the encapsulated
+ headers embedded in the bodies of messages of type "message."
+
+5.2.1. RFC822 Subtype
+
+ A media type of "message/rfc822" indicates that the body contains an
+ encapsulated message, with the syntax of an RFC 822 message.
+ However, unlike top-level RFC 822 messages, the restriction that each
+ "message/rfc822" body must include a "From", "Date", and at least one
+ destination header is removed and replaced with the requirement that
+ at least one of "From", "Subject", or "Date" must be present.
+
+
+
+Freed & Borenstein Standards Track [Page 28]
+
+RFC 2046 Media Types November 1996
+
+
+ It should be noted that, despite the use of the numbers "822", a
+ "message/rfc822" entity isn't restricted to material in strict
+ conformance to RFC822, nor are the semantics of "message/rfc822"
+ objects restricted to the semantics defined in RFC822. More
+ specifically, a "message/rfc822" message could well be a News article
+ or a MIME message.
+
+ No encoding other than "7bit", "8bit", or "binary" is permitted for
+ the body of a "message/rfc822" entity. The message header fields are
+ always US-ASCII in any case, and data within the body can still be
+ encoded, in which case the Content-Transfer-Encoding header field in
+ the encapsulated message will reflect this. Non-US-ASCII text in the
+ headers of an encapsulated message can be specified using the
+ mechanisms described in RFC 2047.
+
+5.2.2. Partial Subtype
+
+ The "partial" subtype is defined to allow large entities to be
+ delivered as several separate pieces of mail and automatically
+ reassembled by a receiving user agent. (The concept is similar to IP
+ fragmentation and reassembly in the basic Internet Protocols.) This
+ mechanism can be used when intermediate transport agents limit the
+ size of individual messages that can be sent. The media type
+ "message/partial" thus indicates that the body contains a fragment of
+ a larger entity.
+
+ Because data of type "message" may never be encoded in base64 or
+ quoted-printable, a problem might arise if "message/partial" entities
+ are constructed in an environment that supports binary or 8bit
+ transport. The problem is that the binary data would be split into
+ multiple "message/partial" messages, each of them requiring binary
+ transport. If such messages were encountered at a gateway into a
+ 7bit transport environment, there would be no way to properly encode
+ them for the 7bit world, aside from waiting for all of the fragments,
+ reassembling the inner message, and then encoding the reassembled
+ data in base64 or quoted-printable. Since it is possible that
+ different fragments might go through different gateways, even this is
+ not an acceptable solution. For this reason, it is specified that
+ entities of type "message/partial" must always have a content-
+ transfer-encoding of 7bit (the default). In particular, even in
+ environments that support binary or 8bit transport, the use of a
+ content- transfer-encoding of "8bit" or "binary" is explicitly
+ prohibited for MIME entities of type "message/partial". This in turn
+ implies that the inner message must not use "8bit" or "binary"
+ encoding.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 29]
+
+RFC 2046 Media Types November 1996
+
+
+ Because some message transfer agents may choose to automatically
+ fragment large messages, and because such agents may use very
+ different fragmentation thresholds, it is possible that the pieces of
+ a partial message, upon reassembly, may prove themselves to comprise
+ a partial message. This is explicitly permitted.
+
+ Three parameters must be specified in the Content-Type field of type
+ "message/partial": The first, "id", is a unique identifier, as close
+ to a world-unique identifier as possible, to be used to match the
+ fragments together. (In general, the identifier is essentially a
+ message-id; if placed in double quotes, it can be ANY message-id, in
+ accordance with the BNF for "parameter" given in RFC 2045.) The
+ second, "number", an integer, is the fragment number, which indicates
+ where this fragment fits into the sequence of fragments. The third,
+ "total", another integer, is the total number of fragments. This
+ third subfield is required on the final fragment, and is optional
+ (though encouraged) on the earlier fragments. Note also that these
+ parameters may be given in any order.
+
+ Thus, the second piece of a 3-piece message may have either of the
+ following header fields:
+
+ Content-Type: Message/Partial; number=2; total=3;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com"
+
+ Content-Type: Message/Partial;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com";
+ number=2
+
+ But the third piece MUST specify the total number of fragments:
+
+ Content-Type: Message/Partial; number=3; total=3;
+ id="oc=jpbe0M2Yt4s@thumper.bellcore.com"
+
+ Note that fragment numbering begins with 1, not 0.
+
+ When the fragments of an entity broken up in this manner are put
+ together, the result is always a complete MIME entity, which may have
+ its own Content-Type header field, and thus may contain any other
+ data type.
+
+5.2.2.1. Message Fragmentation and Reassembly
+
+ The semantics of a reassembled partial message must be those of the
+ "inner" message, rather than of a message containing the inner
+ message. This makes it possible, for example, to send a large audio
+ message as several partial messages, and still have it appear to the
+ recipient as a simple audio message rather than as an encapsulated
+
+
+
+Freed & Borenstein Standards Track [Page 30]
+
+RFC 2046 Media Types November 1996
+
+
+ message containing an audio message. That is, the encapsulation of
+ the message is considered to be "transparent".
+
+ When generating and reassembling the pieces of a "message/partial"
+ message, the headers of the encapsulated message must be merged with
+ the headers of the enclosing entities. In this process the following
+ rules must be observed:
+
+ (1) Fragmentation agents must split messages at line
+ boundaries only. This restriction is imposed because
+ splits at points other than the ends of lines in turn
+ depends on message transports being able to preserve
+ the semantics of messages that don't end with a CRLF
+ sequence. Many transports are incapable of preserving
+ such semantics.
+
+ (2) All of the header fields from the initial enclosing
+ message, except those that start with "Content-" and
+ the specific header fields "Subject", "Message-ID",
+ "Encrypted", and "MIME-Version", must be copied, in
+ order, to the new message.
+
+ (3) The header fields in the enclosed message which start
+ with "Content-", plus the "Subject", "Message-ID",
+ "Encrypted", and "MIME-Version" fields, must be
+ appended, in order, to the header fields of the new
+ message. Any header fields in the enclosed message
+ which do not start with "Content-" (except for the
+ "Subject", "Message-ID", "Encrypted", and "MIME-
+ Version" fields) will be ignored and dropped.
+
+ (4) All of the header fields from the second and any
+ subsequent enclosing messages are discarded by the
+ reassembly process.
+
+5.2.2.2. Fragmentation and Reassembly Example
+
+ If an audio message is broken into two pieces, the first piece might
+ look something like this:
+
+ X-Weird-Header-1: Foo
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
+ Subject: Audio mail (part 1 of 2)
+ Message-ID: <id1@host.com>
+ MIME-Version: 1.0
+ Content-type: message/partial; id="ABC@host.com";
+
+
+
+Freed & Borenstein Standards Track [Page 31]
+
+RFC 2046 Media Types November 1996
+
+
+ number=1; total=2
+
+ X-Weird-Header-1: Bar
+ X-Weird-Header-2: Hello
+ Message-ID: <anotherid@foo.com>
+ Subject: Audio mail
+ MIME-Version: 1.0
+ Content-type: audio/basic
+ Content-transfer-encoding: base64
+
+ ... first half of encoded audio data goes here ...
+
+ and the second half might look something like this:
+
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
+ Subject: Audio mail (part 2 of 2)
+ MIME-Version: 1.0
+ Message-ID: <id2@host.com>
+ Content-type: message/partial;
+ id="ABC@host.com"; number=2; total=2
+
+ ... second half of encoded audio data goes here ...
+
+ Then, when the fragmented message is reassembled, the resulting
+ message to be displayed to the user should look something like this:
+
+ X-Weird-Header-1: Foo
+ From: Bill@host.com
+ To: joe@otherhost.com
+ Date: Fri, 26 Mar 1993 12:59:38 -0500 (EST)
+ Subject: Audio mail
+ Message-ID: <anotherid@foo.com>
+ MIME-Version: 1.0
+ Content-type: audio/basic
+ Content-transfer-encoding: base64
+
+ ... first half of encoded audio data goes here ...
+ ... second half of encoded audio data goes here ...
+
+ The inclusion of a "References" field in the headers of the second
+ and subsequent pieces of a fragmented message that references the
+ Message-Id on the previous piece may be of benefit to mail readers
+ that understand and track references. However, the generation of
+ such "References" fields is entirely optional.
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 32]
+
+RFC 2046 Media Types November 1996
+
+
+ Finally, it should be noted that the "Encrypted" header field has
+ been made obsolete by Privacy Enhanced Messaging (PEM) [RFC-1421,
+ RFC-1422, RFC-1423, RFC-1424], but the rules above are nevertheless
+ believed to describe the correct way to treat it if it is encountered
+ in the context of conversion to and from "message/partial" fragments.
+
+5.2.3. External-Body Subtype
+
+ The external-body subtype indicates that the actual body data are not
+ included, but merely referenced. In this case, the parameters
+ describe a mechanism for accessing the external data.
+
+ When a MIME entity is of type "message/external-body", it consists of
+ a header, two consecutive CRLFs, and the message header for the
+ encapsulated message. If another pair of consecutive CRLFs appears,
+ this of course ends the message header for the encapsulated message.
+ However, since the encapsulated message's body is itself external, it
+ does NOT appear in the area that follows. For example, consider the
+ following message:
+
+ Content-type: message/external-body;
+ access-type=local-file;
+ name="/u/nsb/Me.jpeg"
+
+ Content-type: image/jpeg
+ Content-ID: <id42@guppylake.bellcore.com>
+ Content-Transfer-Encoding: binary
+
+ THIS IS NOT REALLY THE BODY!
+
+ The area at the end, which might be called the "phantom body", is
+ ignored for most external-body messages. However, it may be used to
+ contain auxiliary information for some such messages, as indeed it is
+ when the access-type is "mail- server". The only access-type defined
+ in this document that uses the phantom body is "mail-server", but
+ other access-types may be defined in the future in other
+ specifications that use this area.
+
+ The encapsulated headers in ALL "message/external-body" entities MUST
+ include a Content-ID header field to give a unique identifier by
+ which to reference the data. This identifier may be used for caching
+ mechanisms, and for recognizing the receipt of the data when the
+ access-type is "mail-server".
+
+ Note that, as specified here, the tokens that describe external-body
+ data, such as file names and mail server commands, are required to be
+ in the US-ASCII character set.
+
+
+
+
+Freed & Borenstein Standards Track [Page 33]
+
+RFC 2046 Media Types November 1996
+
+
+ If this proves problematic in practice, a new mechanism may be
+ required as a future extension to MIME, either as newly defined
+ access-types for "message/external-body" or by some other mechanism.
+
+ As with "message/partial", MIME entities of type "message/external-
+ body" MUST have a content-transfer-encoding of 7bit (the default).
+ In particular, even in environments that support binary or 8bit
+ transport, the use of a content- transfer-encoding of "8bit" or
+ "binary" is explicitly prohibited for entities of type
+ "message/external-body".
+
+5.2.3.1. General External-Body Parameters
+
+ The parameters that may be used with any "message/external- body"
+ are:
+
+ (1) ACCESS-TYPE -- A word indicating the supported access
+ mechanism by which the file or data may be obtained.
+ This word is not case sensitive. Values include, but
+ are not limited to, "FTP", "ANON-FTP", "TFTP", "LOCAL-
+ FILE", and "MAIL-SERVER". Future values, except for
+ experimental values beginning with "X-", must be
+ registered with IANA, as described in RFC 2048.
+ This parameter is unconditionally mandatory and MUST be
+ present on EVERY "message/external-body".
+
+ (2) EXPIRATION -- The date (in the RFC 822 "date-time"
+ syntax, as extended by RFC 1123 to permit 4 digits in
+ the year field) after which the existence of the
+ external data is not guaranteed. This parameter may be
+ used with ANY access-type and is ALWAYS optional.
+
+ (3) SIZE -- The size (in octets) of the data. The intent
+ of this parameter is to help the recipient decide
+ whether or not to expend the necessary resources to
+ retrieve the external data. Note that this describes
+ the size of the data in its canonical form, that is,
+ before any Content-Transfer-Encoding has been applied
+ or after the data have been decoded. This parameter
+ may be used with ANY access-type and is ALWAYS
+ optional.
+
+ (4) PERMISSION -- A case-insensitive field that indicates
+ whether or not it is expected that clients might also
+ attempt to overwrite the data. By default, or if
+ permission is "read", the assumption is that they are
+ not, and that if the data is retrieved once, it is
+ never needed again. If PERMISSION is "read-write",
+
+
+
+Freed & Borenstein Standards Track [Page 34]
+
+RFC 2046 Media Types November 1996
+
+
+ this assumption is invalid, and any local copy must be
+ considered no more than a cache. "Read" and "Read-
+ write" are the only defined values of permission. This
+ parameter may be used with ANY access-type and is
+ ALWAYS optional.
+
+ The precise semantics of the access-types defined here are described
+ in the sections that follow.
+
+5.2.3.2. The 'ftp' and 'tftp' Access-Types
+
+ An access-type of FTP or TFTP indicates that the message body is
+ accessible as a file using the FTP [RFC-959] or TFTP [RFC- 783]
+ protocols, respectively. For these access-types, the following
+ additional parameters are mandatory:
+
+ (1) NAME -- The name of the file that contains the actual
+ body data.
+
+ (2) SITE -- A machine from which the file may be obtained,
+ using the given protocol. This must be a fully
+ qualified domain name, not a nickname.
+
+ (3) Before any data are retrieved, using FTP, the user will
+ generally need to be asked to provide a login id and a
+ password for the machine named by the site parameter.
+ For security reasons, such an id and password are not
+ specified as content-type parameters, but must be
+ obtained from the user.
+
+ In addition, the following parameters are optional:
+
+ (1) DIRECTORY -- A directory from which the data named by
+ NAME should be retrieved.
+
+ (2) MODE -- A case-insensitive string indicating the mode
+ to be used when retrieving the information. The valid
+ values for access-type "TFTP" are "NETASCII", "OCTET",
+ and "MAIL", as specified by the TFTP protocol [RFC-
+ 783]. The valid values for access-type "FTP" are
+ "ASCII", "EBCDIC", "IMAGE", and "LOCALn" where "n" is a
+ decimal integer, typically 8. These correspond to the
+ representation types "A" "E" "I" and "L n" as specified
+ by the FTP protocol [RFC-959]. Note that "BINARY" and
+ "TENEX" are not valid values for MODE and that "OCTET"
+ or "IMAGE" or "LOCAL8" should be used instead. IF MODE
+ is not specified, the default value is "NETASCII" for
+ TFTP and "ASCII" otherwise.
+
+
+
+Freed & Borenstein Standards Track [Page 35]
+
+RFC 2046 Media Types November 1996
+
+
+5.2.3.3. The 'anon-ftp' Access-Type
+
+ The "anon-ftp" access-type is identical to the "ftp" access type,
+ except that the user need not be asked to provide a name and password
+ for the specified site. Instead, the ftp protocol will be used with
+ login "anonymous" and a password that corresponds to the user's mail
+ address.
+
+5.2.3.4. The 'local-file' Access-Type
+
+ An access-type of "local-file" indicates that the actual body is
+ accessible as a file on the local machine. Two additional parameters
+ are defined for this access type:
+
+ (1) NAME -- The name of the file that contains the actual
+ body data. This parameter is mandatory for the
+ "local-file" access-type.
+
+ (2) SITE -- A domain specifier for a machine or set of
+ machines that are known to have access to the data
+ file. This optional parameter is used to describe the
+ locality of reference for the data, that is, the site
+ or sites at which the file is expected to be visible.
+ Asterisks may be used for wildcard matching to a part
+ of a domain name, such as "*.bellcore.com", to indicate
+ a set of machines on which the data should be directly
+ visible, while a single asterisk may be used to
+ indicate a file that is expected to be universally
+ available, e.g., via a global file system.
+
+5.2.3.5. The 'mail-server' Access-Type
+
+ The "mail-server" access-type indicates that the actual body is
+ available from a mail server. Two additional parameters are defined
+ for this access-type:
+
+ (1) SERVER -- The addr-spec of the mail server from which
+ the actual body data can be obtained. This parameter
+ is mandatory for the "mail-server" access-type.
+
+ (2) SUBJECT -- The subject that is to be used in the mail
+ that is sent to obtain the data. Note that keying mail
+ servers on Subject lines is NOT recommended, but such
+ mail servers are known to exist. This is an optional
+ parameter.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 36]
+
+RFC 2046 Media Types November 1996
+
+
+ Because mail servers accept a variety of syntaxes, some of which is
+ multiline, the full command to be sent to a mail server is not
+ included as a parameter in the content-type header field. Instead,
+ it is provided as the "phantom body" when the media type is
+ "message/external-body" and the access-type is mail-server.
+
+ Note that MIME does not define a mail server syntax. Rather, it
+ allows the inclusion of arbitrary mail server commands in the phantom
+ body. Implementations must include the phantom body in the body of
+ the message it sends to the mail server address to retrieve the
+ relevant data.
+
+ Unlike other access-types, mail-server access is asynchronous and
+ will happen at an unpredictable time in the future. For this reason,
+ it is important that there be a mechanism by which the returned data
+ can be matched up with the original "message/external-body" entity.
+ MIME mail servers must use the same Content-ID field on the returned
+ message that was used in the original "message/external-body"
+ entities, to facilitate such matching.
+
+5.2.3.6. External-Body Security Issues
+
+ "Message/external-body" entities give rise to two important security
+ issues:
+
+ (1) Accessing data via a "message/external-body" reference
+ effectively results in the message recipient performing
+ an operation that was specified by the message
+ originator. It is therefore possible for the message
+ originator to trick a recipient into doing something
+ they would not have done otherwise. For example, an
+ originator could specify a action that attempts
+ retrieval of material that the recipient is not
+ authorized to obtain, causing the recipient to
+ unwittingly violate some security policy. For this
+ reason, user agents capable of resolving external
+ references must always take steps to describe the
+ action they are to take to the recipient and ask for
+ explicit permisssion prior to performing it.
+
+ The 'mail-server' access-type is particularly
+ vulnerable, in that it causes the recipient to send a
+ new message whose contents are specified by the
+ original message's originator. Given the potential for
+ abuse, any such request messages that are constructed
+ should contain a clear indication that they were
+ generated automatically (e.g. in a Comments: header
+ field) in an attempt to resolve a MIME
+
+
+
+Freed & Borenstein Standards Track [Page 37]
+
+RFC 2046 Media Types November 1996
+
+
+ "message/external-body" reference.
+
+ (2) MIME will sometimes be used in environments that
+ provide some guarantee of message integrity and
+ authenticity. If present, such guarantees may apply
+ only to the actual direct content of messages -- they
+ may or may not apply to data accessed through MIME's
+ "message/external-body" mechanism. In particular, it
+ may be possible to subvert certain access mechanisms
+ even when the messaging system itself is secure.
+
+ It should be noted that this problem exists either with
+ or without the availabilty of MIME mechanisms. A
+ casual reference to an FTP site containing a document
+ in the text of a secure message brings up similar
+ issues -- the only difference is that MIME provides for
+ automatic retrieval of such material, and users may
+ place unwarranted trust is such automatic retrieval
+ mechanisms.
+
+5.2.3.7. Examples and Further Explanations
+
+ When the external-body mechanism is used in conjunction with the
+ "multipart/alternative" media type it extends the functionality of
+ "multipart/alternative" to include the case where the same entity is
+ provided in the same format but via different accces mechanisms.
+ When this is done the originator of the message must order the parts
+ first in terms of preferred formats and then by preferred access
+ mechanisms. The recipient's viewer should then evaluate the list
+ both in terms of format and access mechanisms.
+
+ With the emerging possibility of very wide-area file systems, it
+ becomes very hard to know in advance the set of machines where a file
+ will and will not be accessible directly from the file system.
+ Therefore it may make sense to provide both a file name, to be tried
+ directly, and the name of one or more sites from which the file is
+ known to be accessible. An implementation can try to retrieve remote
+ files using FTP or any other protocol, using anonymous file retrieval
+ or prompting the user for the necessary name and password. If an
+ external body is accessible via multiple mechanisms, the sender may
+ include multiple entities of type "message/external-body" within the
+ body parts of an enclosing "multipart/alternative" entity.
+
+ However, the external-body mechanism is not intended to be limited to
+ file retrieval, as shown by the mail-server access-type. Beyond
+ this, one can imagine, for example, using a video server for external
+ references to video clips.
+
+
+
+
+Freed & Borenstein Standards Track [Page 38]
+
+RFC 2046 Media Types November 1996
+
+
+ The embedded message header fields which appear in the body of the
+ "message/external-body" data must be used to declare the media type
+ of the external body if it is anything other than plain US-ASCII
+ text, since the external body does not have a header section to
+ declare its type. Similarly, any Content-transfer-encoding other
+ than "7bit" must also be declared here. Thus a complete
+ "message/external-body" message, referring to an object in PostScript
+ format, might look like this:
+
+ From: Whomever
+ To: Someone
+ Date: Whenever
+ Subject: whatever
+ MIME-Version: 1.0
+ Message-ID: <id1@host.com>
+ Content-Type: multipart/alternative; boundary=42
+ Content-ID: <id001@guppylake.bellcore.com>
+
+ --42
+ Content-Type: message/external-body; name="BodyFormats.ps";
+ site="thumper.bellcore.com"; mode="image";
+ access-type=ANON-FTP; directory="pub";
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+ Content-ID: <id42@guppylake.bellcore.com>
+
+ --42
+ Content-Type: message/external-body; access-type=local-file;
+ name="/u/nsb/writing/rfcs/RFC-MIME.ps";
+ site="thumper.bellcore.com";
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+ Content-ID: <id42@guppylake.bellcore.com>
+
+ --42
+ Content-Type: message/external-body;
+ access-type=mail-server
+ server="listserv@bogus.bitnet";
+ expiration="Fri, 14 Jun 1991 19:13:14 -0400 (EDT)"
+
+ Content-type: application/postscript
+ Content-ID: <id42@guppylake.bellcore.com>
+
+ get RFC-MIME.DOC
+
+ --42--
+
+
+
+Freed & Borenstein Standards Track [Page 39]
+
+RFC 2046 Media Types November 1996
+
+
+ Note that in the above examples, the default Content-transfer-
+ encoding of "7bit" is assumed for the external postscript data.
+
+ Like the "message/partial" type, the "message/external-body" media
+ type is intended to be transparent, that is, to convey the data type
+ in the external body rather than to convey a message with a body of
+ that type. Thus the headers on the outer and inner parts must be
+ merged using the same rules as for "message/partial". In particular,
+ this means that the Content-type and Subject fields are overridden,
+ but the From field is preserved.
+
+ Note that since the external bodies are not transported along with
+ the external body reference, they need not conform to transport
+ limitations that apply to the reference itself. In particular,
+ Internet mail transports may impose 7bit and line length limits, but
+ these do not automatically apply to binary external body references.
+ Thus a Content-Transfer-Encoding is not generally necessary, though
+ it is permitted.
+
+ Note that the body of a message of type "message/external-body" is
+ governed by the basic syntax for an RFC 822 message. In particular,
+ anything before the first consecutive pair of CRLFs is header
+ information, while anything after it is body information, which is
+ ignored for most access-types.
+
+5.2.4. Other Message Subtypes
+
+ MIME implementations must in general treat unrecognized subtypes of
+ "message" as being equivalent to "application/octet-stream".
+
+ Future subtypes of "message" intended for use with email should be
+ restricted to "7bit" encoding. A type other than "message" should be
+ used if restriction to "7bit" is not possible.
+
+6. Experimental Media Type Values
+
+ A media type value beginning with the characters "X-" is a private
+ value, to be used by consenting systems by mutual agreement. Any
+ format without a rigorous and public definition must be named with an
+ "X-" prefix, and publicly specified values shall never begin with
+ "X-". (Older versions of the widely used Andrew system use the "X-
+ BE2" name, so new systems should probably choose a different name.)
+
+ In general, the use of "X-" top-level types is strongly discouraged.
+ Implementors should invent subtypes of the existing types whenever
+ possible. In many cases, a subtype of "application" will be more
+ appropriate than a new top-level type.
+
+
+
+
+Freed & Borenstein Standards Track [Page 40]
+
+RFC 2046 Media Types November 1996
+
+
+7. Summary
+
+ The five discrete media types provide provide a standardized
+ mechanism for tagging entities as "audio", "image", or several other
+ kinds of data. The composite "multipart" and "message" media types
+ allow mixing and hierarchical structuring of entities of different
+ types in a single message. A distinguished parameter syntax allows
+ further specification of data format details, particularly the
+ specification of alternate character sets. Additional optional
+ header fields provide mechanisms for certain extensions deemed
+ desirable by many implementors. Finally, a number of useful media
+ types are defined for general use by consenting user agents, notably
+ "message/partial" and "message/external-body".
+
+9. Security Considerations
+
+ Security issues are discussed in the context of the
+ "application/postscript" type, the "message/external-body" type, and
+ in RFC 2048. Implementors should pay special attention to the
+ security implications of any media types that can cause the remote
+ execution of any actions in the recipient's environment. In such
+ cases, the discussion of the "application/postscript" type may serve
+ as a model for considering other media types with remote execution
+ capabilities.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 41]
+
+RFC 2046 Media Types November 1996
+
+
+9. Authors' Addresses
+
+ For more information, the authors of this document are best contacted
+ via Internet mail:
+
+ Ned Freed
+ Innosoft International, Inc.
+ 1050 East Garvey Avenue South
+ West Covina, CA 91790
+ USA
+
+ Phone: +1 818 919 3600
+ Fax: +1 818 919 3614
+ EMail: ned@innosoft.com
+
+
+ Nathaniel S. Borenstein
+ First Virtual Holdings
+ 25 Washington Avenue
+ Morristown, NJ 07960
+ USA
+
+ Phone: +1 201 540 8967
+ Fax: +1 201 993 3032
+ EMail: nsb@nsb.fv.com
+
+
+ MIME is a result of the work of the Internet Engineering Task Force
+ Working Group on RFC 822 Extensions. The chairman of that group,
+ Greg Vaudreuil, may be reached at:
+
+ Gregory M. Vaudreuil
+ Octel Network Services
+ 17080 Dallas Parkway
+ Dallas, TX 75248-1905
+ USA
+
+ EMail: Greg.Vaudreuil@Octel.Com
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 42]
+
+RFC 2046 Media Types November 1996
+
+
+Appendix A -- Collected Grammar
+
+ This appendix contains the complete BNF grammar for all the syntax
+ specified by this document.
+
+ By itself, however, this grammar is incomplete. It refers by name to
+ several syntax rules that are defined by RFC 822. Rather than
+ reproduce those definitions here, and risk unintentional differences
+ between the two, this document simply refers the reader to RFC 822
+ for the remaining definitions. Wherever a term is undefined, it
+ refers to the RFC 822 definition.
+
+ boundary := 0*69<bchars> bcharsnospace
+
+ bchars := bcharsnospace / " "
+
+ bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" /
+ "+" / "_" / "," / "-" / "." /
+ "/" / ":" / "=" / "?"
+
+ body-part := <"message" as defined in RFC 822, with all
+ header fields optional, not starting with the
+ specified dash-boundary, and with the
+ delimiter not occurring anywhere in the
+ body part. Note that the semantics of a
+ part differ from the semantics of a message,
+ as described in the text.>
+
+ close-delimiter := delimiter "--"
+
+ dash-boundary := "--" boundary
+ ; boundary taken from the value of
+ ; boundary parameter of the
+ ; Content-Type field.
+
+ delimiter := CRLF dash-boundary
+
+ discard-text := *(*text CRLF)
+ ; May be ignored or discarded.
+
+ encapsulation := delimiter transport-padding
+ CRLF body-part
+
+ epilogue := discard-text
+
+ multipart-body := [preamble CRLF]
+ dash-boundary transport-padding CRLF
+ body-part *encapsulation
+
+
+
+Freed & Borenstein Standards Track [Page 43]
+
+RFC 2046 Media Types November 1996
+
+
+ close-delimiter transport-padding
+ [CRLF epilogue]
+
+ preamble := discard-text
+
+ transport-padding := *LWSP-char
+ ; Composers MUST NOT generate
+ ; non-zero length transport
+ ; padding, but receivers MUST
+ ; be able to handle padding
+ ; added by message transports.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 44]
+
diff --git a/rfc/rfc2047.txt b/rfc/rfc2047.txt
@@ -0,0 +1,843 @@
+
+
+
+
+
+
+Network Working Group K. Moore
+Request for Comments: 2047 University of Tennessee
+Obsoletes: 1521, 1522, 1590 November 1996
+Category: Standards Track
+
+
+ MIME (Multipurpose Internet Mail Extensions) Part Three:
+ Message Header Extensions for Non-ASCII Text
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ STD 11, RFC 822, defines a message representation protocol specifying
+ considerable detail about US-ASCII message headers, and leaves the
+ message content, or message body, as flat US-ASCII text. This set of
+ documents, collectively called the Multipurpose Internet Mail
+ Extensions, or MIME, redefines the format of messages to allow for
+
+ (1) textual message bodies in character sets other than US-ASCII,
+
+ (2) an extensible set of different formats for non-textual message
+ bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than US-ASCII.
+
+ These documents are based on earlier work documented in RFC 934, STD
+ 11, and RFC 1049, but extends and revises them. Because RFC 822 said
+ so little about message bodies, these documents are largely
+ orthogonal to (rather than a revision of) RFC 822.
+
+ This particular document is the third document in the series. It
+ describes extensions to RFC 822 to allow non-US-ASCII text data in
+ Internet mail header fields.
+
+
+
+
+
+
+
+
+
+Moore Standards Track [Page 1]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ Other documents in this series include:
+
+ + RFC 2045, which specifies the various headers used to describe
+ the structure of MIME messages.
+
+ + RFC 2046, which defines the general structure of the MIME media
+ typing system and defines an initial set of media types,
+
+ + RFC 2048, which specifies various IANA registration procedures
+ for MIME-related facilities, and
+
+ + RFC 2049, which describes MIME conformance criteria and
+ provides some illustrative examples of MIME message formats,
+ acknowledgements, and the bibliography.
+
+ These documents are revisions of RFCs 1521, 1522, and 1590, which
+ themselves were revisions of RFCs 1341 and 1342. An appendix in RFC
+ 2049 describes differences and changes from previous versions.
+
+1. Introduction
+
+ RFC 2045 describes a mechanism for denoting textual body parts which
+ are coded in various character sets, as well as methods for encoding
+ such body parts as sequences of printable US-ASCII characters. This
+ memo describes similar techniques to allow the encoding of non-ASCII
+ text in various portions of a RFC 822 [2] message header, in a manner
+ which is unlikely to confuse existing message handling software.
+
+ Like the encoding techniques described in RFC 2045, the techniques
+ outlined here were designed to allow the use of non-ASCII characters
+ in message headers in a way which is unlikely to be disturbed by the
+ quirks of existing Internet mail handling programs. In particular,
+ some mail relaying programs are known to (a) delete some message
+ header fields while retaining others, (b) rearrange the order of
+ addresses in To or Cc fields, (c) rearrange the (vertical) order of
+ header fields, and/or (d) "wrap" message headers at different places
+ than those in the original message. In addition, some mail reading
+ programs are known to have difficulty correctly parsing message
+ headers which, while legal according to RFC 822, make use of
+ backslash-quoting to "hide" special characters such as "<", ",", or
+ ":", or which exploit other infrequently-used features of that
+ specification.
+
+ While it is unfortunate that these programs do not correctly
+ interpret RFC 822 headers, to "break" these programs would cause
+ severe operational problems for the Internet mail system. The
+ extensions described in this memo therefore do not rely on little-
+ used features of RFC 822.
+
+
+
+Moore Standards Track [Page 2]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ Instead, certain sequences of "ordinary" printable ASCII characters
+ (known as "encoded-words") are reserved for use as encoded data. The
+ syntax of encoded-words is such that they are unlikely to
+ "accidentally" appear as normal text in message headers.
+ Furthermore, the characters used in encoded-words are restricted to
+ those which do not have special meanings in the context in which the
+ encoded-word appears.
+
+ Generally, an "encoded-word" is a sequence of printable ASCII
+ characters that begins with "=?", ends with "?=", and has two "?"s in
+ between. It specifies a character set and an encoding method, and
+ also includes the original text encoded as graphic ASCII characters,
+ according to the rules for that encoding method.
+
+ A mail composer that implements this specification will provide a
+ means of inputting non-ASCII text in header fields, but will
+ translate these fields (or appropriate portions of these fields) into
+ encoded-words before inserting them into the message header.
+
+ A mail reader that implements this specification will recognize
+ encoded-words when they appear in certain portions of the message
+ header. Instead of displaying the encoded-word "as is", it will
+ reverse the encoding and display the original text in the designated
+ character set.
+
+NOTES
+
+ This memo relies heavily on notation and terms defined RFC 822 and
+ RFC 2045. In particular, the syntax for the ABNF used in this memo
+ is defined in RFC 822, as well as many of the terminal or nonterminal
+ symbols from RFC 822 are used in the grammar for the header
+ extensions defined here. Among the symbols defined in RFC 822 and
+ referenced in this memo are: 'addr-spec', 'atom', 'CHAR', 'comment',
+ 'CTLs', 'ctext', 'linear-white-space', 'phrase', 'quoted-pair'.
+ 'quoted-string', 'SPACE', and 'word'. Successful implementation of
+ this protocol extension requires careful attention to the RFC 822
+ definitions of these terms.
+
+ When the term "ASCII" appears in this memo, it refers to the "7-Bit
+ American Standard Code for Information Interchange", ANSI X3.4-1986.
+ The MIME charset name for this character set is "US-ASCII". When not
+ specifically referring to the MIME charset name, this document uses
+ the term "ASCII", both for brevity and for consistency with RFC 822.
+ However, implementors are warned that the character set name must be
+ spelled "US-ASCII" in MIME message and body part headers.
+
+
+
+
+
+
+Moore Standards Track [Page 3]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ This memo specifies a protocol for the representation of non-ASCII
+ text in message headers. It specifically DOES NOT define any
+ translation between "8-bit headers" and pure ASCII headers, nor is
+ any such translation assumed to be possible.
+
+2. Syntax of encoded-words
+
+ An 'encoded-word' is defined by the following ABNF grammar. The
+ notation of RFC 822 is used, with the exception that white space
+ characters MUST NOT appear between components of an 'encoded-word'.
+
+ encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
+
+ charset = token ; see section 3
+
+ encoding = token ; see section 4
+
+ token = 1*<Any CHAR except SPACE, CTLs, and especials>
+
+ especials = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "
+ <"> / "/" / "[" / "]" / "?" / "." / "="
+
+ encoded-text = 1*<Any printable ASCII character other than "?"
+ or SPACE>
+ ; (but see "Use of encoded-words in message
+ ; headers", section 5)
+
+ Both 'encoding' and 'charset' names are case-independent. Thus the
+ charset name "ISO-8859-1" is equivalent to "iso-8859-1", and the
+ encoding named "Q" may be spelled either "Q" or "q".
+
+ An 'encoded-word' may not be more than 75 characters long, including
+ 'charset', 'encoding', 'encoded-text', and delimiters. If it is
+ desirable to encode more text than will fit in an 'encoded-word' of
+ 75 characters, multiple 'encoded-word's (separated by CRLF SPACE) may
+ be used.
+
+ While there is no limit to the length of a multiple-line header
+ field, each line of a header field that contains one or more
+ 'encoded-word's is limited to 76 characters.
+
+ The length restrictions are included both to ease interoperability
+ through internetwork mail gateways, and to impose a limit on the
+ amount of lookahead a header parser must employ (while looking for a
+ final ?= delimiter) before it can decide whether a token is an
+ "encoded-word" or something else.
+
+
+
+
+
+Moore Standards Track [Page 4]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ IMPORTANT: 'encoded-word's are designed to be recognized as 'atom's
+ by an RFC 822 parser. As a consequence, unencoded white space
+ characters (such as SPACE and HTAB) are FORBIDDEN within an
+ 'encoded-word'. For example, the character sequence
+
+ =?iso-8859-1?q?this is some text?=
+
+ would be parsed as four 'atom's, rather than as a single 'atom' (by
+ an RFC 822 parser) or 'encoded-word' (by a parser which understands
+ 'encoded-words'). The correct way to encode the string "this is some
+ text" is to encode the SPACE characters as well, e.g.
+
+ =?iso-8859-1?q?this=20is=20some=20text?=
+
+ The characters which may appear in 'encoded-text' are further
+ restricted by the rules in section 5.
+
+3. Character sets
+
+ The 'charset' portion of an 'encoded-word' specifies the character
+ set associated with the unencoded text. A 'charset' can be any of
+ the character set names allowed in an MIME "charset" parameter of a
+ "text/plain" body part, or any character set name registered with
+ IANA for use with the MIME text/plain content-type.
+
+ Some character sets use code-switching techniques to switch between
+ "ASCII mode" and other modes. If unencoded text in an 'encoded-word'
+ contains a sequence which causes the charset interpreter to switch
+ out of ASCII mode, it MUST contain additional control codes such that
+ ASCII mode is again selected at the end of the 'encoded-word'. (This
+ rule applies separately to each 'encoded-word', including adjacent
+ 'encoded-word's within a single header field.)
+
+ When there is a possibility of using more than one character set to
+ represent the text in an 'encoded-word', and in the absence of
+ private agreements between sender and recipients of a message, it is
+ recommended that members of the ISO-8859-* series be used in
+ preference to other character sets.
+
+4. Encodings
+
+ Initially, the legal values for "encoding" are "Q" and "B". These
+ encodings are described below. The "Q" encoding is recommended for
+ use when most of the characters to be encoded are in the ASCII
+ character set; otherwise, the "B" encoding should be used.
+ Nevertheless, a mail reader which claims to recognize 'encoded-word's
+ MUST be able to accept either encoding for any character set which it
+ supports.
+
+
+
+Moore Standards Track [Page 5]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ Only a subset of the printable ASCII characters may be used in
+ 'encoded-text'. Space and tab characters are not allowed, so that
+ the beginning and end of an 'encoded-word' are obvious. The "?"
+ character is used within an 'encoded-word' to separate the various
+ portions of the 'encoded-word' from one another, and thus cannot
+ appear in the 'encoded-text' portion. Other characters are also
+ illegal in certain contexts. For example, an 'encoded-word' in a
+ 'phrase' preceding an address in a From header field may not contain
+ any of the "specials" defined in RFC 822. Finally, certain other
+ characters are disallowed in some contexts, to ensure reliability for
+ messages that pass through internetwork mail gateways.
+
+ The "B" encoding automatically meets these requirements. The "Q"
+ encoding allows a wide range of printable characters to be used in
+ non-critical locations in the message header (e.g., Subject), with
+ fewer characters available for use in other locations.
+
+4.1. The "B" encoding
+
+ The "B" encoding is identical to the "BASE64" encoding defined by RFC
+ 2045.
+
+4.2. The "Q" encoding
+
+ The "Q" encoding is similar to the "Quoted-Printable" content-
+ transfer-encoding defined in RFC 2045. It is designed to allow text
+ containing mostly ASCII characters to be decipherable on an ASCII
+ terminal without decoding.
+
+ (1) Any 8-bit value may be represented by a "=" followed by two
+ hexadecimal digits. For example, if the character set in use
+ were ISO-8859-1, the "=" character would thus be encoded as
+ "=3D", and a SPACE by "=20". (Upper case should be used for
+ hexadecimal digits "A" through "F".)
+
+ (2) The 8-bit hexadecimal value 20 (e.g., ISO-8859-1 SPACE) may be
+ represented as "_" (underscore, ASCII 95.). (This character may
+ not pass through some internetwork mail gateways, but its use
+ will greatly enhance readability of "Q" encoded data with mail
+ readers that do not support this encoding.) Note that the "_"
+ always represents hexadecimal 20, even if the SPACE character
+ occupies a different code position in the character set in use.
+
+ (3) 8-bit values which correspond to printable ASCII characters other
+ than "=", "?", and "_" (underscore), MAY be represented as those
+ characters. (But see section 5 for restrictions.) In
+ particular, SPACE and TAB MUST NOT be represented as themselves
+ within encoded words.
+
+
+
+Moore Standards Track [Page 6]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+5. Use of encoded-words in message headers
+
+ An 'encoded-word' may appear in a message header or body part header
+ according to the following rules:
+
+(1) An 'encoded-word' may replace a 'text' token (as defined by RFC 822)
+ in any Subject or Comments header field, any extension message
+ header field, or any MIME body part field for which the field body
+ is defined as '*text'. An 'encoded-word' may also appear in any
+ user-defined ("X-") message or body part header field.
+
+ Ordinary ASCII text and 'encoded-word's may appear together in the
+ same header field. However, an 'encoded-word' that appears in a
+ header field defined as '*text' MUST be separated from any adjacent
+ 'encoded-word' or 'text' by 'linear-white-space'.
+
+(2) An 'encoded-word' may appear within a 'comment' delimited by "(" and
+ ")", i.e., wherever a 'ctext' is allowed. More precisely, the RFC
+ 822 ABNF definition for 'comment' is amended as follows:
+
+ comment = "(" *(ctext / quoted-pair / comment / encoded-word) ")"
+
+ A "Q"-encoded 'encoded-word' which appears in a 'comment' MUST NOT
+ contain the characters "(", ")" or "
+ 'encoded-word' that appears in a 'comment' MUST be separated from
+ any adjacent 'encoded-word' or 'ctext' by 'linear-white-space'.
+
+ It is important to note that 'comment's are only recognized inside
+ "structured" field bodies. In fields whose bodies are defined as
+ '*text', "(" and ")" are treated as ordinary characters rather than
+ comment delimiters, and rule (1) of this section applies. (See RFC
+ 822, sections 3.1.2 and 3.1.3)
+
+(3) As a replacement for a 'word' entity within a 'phrase', for example,
+ one that precedes an address in a From, To, or Cc header. The ABNF
+ definition for 'phrase' from RFC 822 thus becomes:
+
+ phrase = 1*( encoded-word / word )
+
+ In this case the set of characters that may be used in a "Q"-encoded
+ 'encoded-word' is restricted to: <upper and lower case ASCII
+ letters, decimal digits, "!", "*", "+", "-", "/", "=", and "_"
+ (underscore, ASCII 95.)>. An 'encoded-word' that appears within a
+ 'phrase' MUST be separated from any adjacent 'word', 'text' or
+ 'special' by 'linear-white-space'.
+
+
+
+
+
+
+Moore Standards Track [Page 7]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ These are the ONLY locations where an 'encoded-word' may appear. In
+ particular:
+
+ + An 'encoded-word' MUST NOT appear in any portion of an 'addr-spec'.
+
+ + An 'encoded-word' MUST NOT appear within a 'quoted-string'.
+
+ + An 'encoded-word' MUST NOT be used in a Received header field.
+
+ + An 'encoded-word' MUST NOT be used in parameter of a MIME
+ Content-Type or Content-Disposition field, or in any structured
+ field body except within a 'comment' or 'phrase'.
+
+ The 'encoded-text' in an 'encoded-word' must be self-contained;
+ 'encoded-text' MUST NOT be continued from one 'encoded-word' to
+ another. This implies that the 'encoded-text' portion of a "B"
+ 'encoded-word' will be a multiple of 4 characters long; for a "Q"
+ 'encoded-word', any "=" character that appears in the 'encoded-text'
+ portion will be followed by two hexadecimal characters.
+
+ Each 'encoded-word' MUST encode an integral number of octets. The
+ 'encoded-text' in each 'encoded-word' must be well-formed according
+ to the encoding specified; the 'encoded-text' may not be continued in
+ the next 'encoded-word'. (For example, "=?charset?Q?=?=
+ =?charset?Q?AB?=" would be illegal, because the two hex digits "AB"
+ must follow the "=" in the same 'encoded-word'.)
+
+ Each 'encoded-word' MUST represent an integral number of characters.
+ A multi-octet character may not be split across adjacent 'encoded-
+ word's.
+
+ Only printable and white space character data should be encoded using
+ this scheme. However, since these encoding schemes allow the
+ encoding of arbitrary octet values, mail readers that implement this
+ decoding should also ensure that display of the decoded data on the
+ recipient's terminal will not cause unwanted side-effects.
+
+ Use of these methods to encode non-textual data (e.g., pictures or
+ sounds) is not defined by this memo. Use of 'encoded-word's to
+ represent strings of purely ASCII characters is allowed, but
+ discouraged. In rare cases it may be necessary to encode ordinary
+ text that looks like an 'encoded-word'.
+
+
+
+
+
+
+
+
+
+Moore Standards Track [Page 8]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+6. Support of 'encoded-word's by mail readers
+
+6.1. Recognition of 'encoded-word's in message headers
+
+ A mail reader must parse the message and body part headers according
+ to the rules in RFC 822 to correctly recognize 'encoded-word's.
+
+ 'encoded-word's are to be recognized as follows:
+
+ (1) Any message or body part header field defined as '*text', or any
+ user-defined header field, should be parsed as follows: Beginning
+ at the start of the field-body and immediately following each
+ occurrence of 'linear-white-space', each sequence of up to 75
+ printable characters (not containing any 'linear-white-space')
+ should be examined to see if it is an 'encoded-word' according to
+ the syntax rules in section 2. Any other sequence of printable
+ characters should be treated as ordinary ASCII text.
+
+ (2) Any header field not defined as '*text' should be parsed
+ according to the syntax rules for that header field. However,
+ any 'word' that appears within a 'phrase' should be treated as an
+ 'encoded-word' if it meets the syntax rules in section 2.
+ Otherwise it should be treated as an ordinary 'word'.
+
+ (3) Within a 'comment', any sequence of up to 75 printable characters
+ (not containing 'linear-white-space'), that meets the syntax
+ rules in section 2, should be treated as an 'encoded-word'.
+ Otherwise it should be treated as normal comment text.
+
+ (4) A MIME-Version header field is NOT required to be present for
+ 'encoded-word's to be interpreted according to this
+ specification. One reason for this is that the mail reader is
+ not expected to parse the entire message header before displaying
+ lines that may contain 'encoded-word's.
+
+6.2. Display of 'encoded-word's
+
+ Any 'encoded-word's so recognized are decoded, and if possible, the
+ resulting unencoded text is displayed in the original character set.
+
+ NOTE: Decoding and display of encoded-words occurs *after* a
+ structured field body is parsed into tokens. It is therefore
+ possible to hide 'special' characters in encoded-words which, when
+ displayed, will be indistinguishable from 'special' characters in the
+ surrounding text. For this and other reasons, it is NOT generally
+ possible to translate a message header containing 'encoded-word's to
+ an unencoded form which can be parsed by an RFC 822 mail reader.
+
+
+
+
+Moore Standards Track [Page 9]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ When displaying a particular header field that contains multiple
+ 'encoded-word's, any 'linear-white-space' that separates a pair of
+ adjacent 'encoded-word's is ignored. (This is to allow the use of
+ multiple 'encoded-word's to represent long strings of unencoded text,
+ without having to separate 'encoded-word's where spaces occur in the
+ unencoded text.)
+
+ In the event other encodings are defined in the future, and the mail
+ reader does not support the encoding used, it may either (a) display
+ the 'encoded-word' as ordinary text, or (b) substitute an appropriate
+ message indicating that the text could not be decoded.
+
+ If the mail reader does not support the character set used, it may
+ (a) display the 'encoded-word' as ordinary text (i.e., as it appears
+ in the header), (b) make a "best effort" to display using such
+ characters as are available, or (c) substitute an appropriate message
+ indicating that the decoded text could not be displayed.
+
+ If the character set being used employs code-switching techniques,
+ display of the encoded text implicitly begins in "ASCII mode". In
+ addition, the mail reader must ensure that the output device is once
+ again in "ASCII mode" after the 'encoded-word' is displayed.
+
+6.3. Mail reader handling of incorrectly formed 'encoded-word's
+
+ It is possible that an 'encoded-word' that is legal according to the
+ syntax defined in section 2, is incorrectly formed according to the
+ rules for the encoding being used. For example:
+
+ (1) An 'encoded-word' which contains characters which are not legal
+ for a particular encoding (for example, a "-" in the "B"
+ encoding, or a SPACE or HTAB in either the "B" or "Q" encoding),
+ is incorrectly formed.
+
+ (2) Any 'encoded-word' which encodes a non-integral number of
+ characters or octets is incorrectly formed.
+
+ A mail reader need not attempt to display the text associated with an
+ 'encoded-word' that is incorrectly formed. However, a mail reader
+ MUST NOT prevent the display or handling of a message because an
+ 'encoded-word' is incorrectly formed.
+
+7. Conformance
+
+ A mail composing program claiming compliance with this specification
+ MUST ensure that any string of non-white-space printable ASCII
+ characters within a '*text' or '*ctext' that begins with "=?" and
+ ends with "?=" be a valid 'encoded-word'. ("begins" means: at the
+
+
+
+Moore Standards Track [Page 10]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ start of the field-body, immediately following 'linear-white-space',
+ or immediately following a "(" for an 'encoded-word' within '*ctext';
+ "ends" means: at the end of the field-body, immediately preceding
+ 'linear-white-space', or immediately preceding a ")" for an
+ 'encoded-word' within '*ctext'.) In addition, any 'word' within a
+ 'phrase' that begins with "=?" and ends with "?=" must be a valid
+ 'encoded-word'.
+
+ A mail reading program claiming compliance with this specification
+ must be able to distinguish 'encoded-word's from 'text', 'ctext', or
+ 'word's, according to the rules in section 6, anytime they appear in
+ appropriate places in message headers. It must support both the "B"
+ and "Q" encodings for any character set which it supports. The
+ program must be able to display the unencoded text if the character
+ set is "US-ASCII". For the ISO-8859-* character sets, the mail
+ reading program must at least be able to display the characters which
+ are also in the ASCII set.
+
+8. Examples
+
+ The following are examples of message headers containing 'encoded-
+ word's:
+
+ From: =?US-ASCII?Q?Keith_Moore?= <moore@cs.utk.edu>
+ To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld@dkuug.dk>
+ CC: =?ISO-8859-1?Q?Andr=E9?= Pirard <PIRARD@vm1.ulg.ac.be>
+ Subject: =?ISO-8859-1?B?SWYgeW91IGNhbiByZWFkIHRoaXMgeW8=?=
+ =?ISO-8859-2?B?dSB1bmRlcnN0YW5kIHRoZSBleGFtcGxlLg==?=
+
+ Note: In the first 'encoded-word' of the Subject field above, the
+ last "=" at the end of the 'encoded-text' is necessary because each
+ 'encoded-word' must be self-contained (the "=" character completes a
+ group of 4 base64 characters representing 2 octets). An additional
+ octet could have been encoded in the first 'encoded-word' (so that
+ the encoded-word would contain an exact multiple of 3 encoded
+ octets), except that the second 'encoded-word' uses a different
+ 'charset' than the first one.
+
+ From: =?ISO-8859-1?Q?Olle_J=E4rnefors?= <ojarnef@admin.kth.se>
+ To: ietf-822@dimacs.rutgers.edu, ojarnef@admin.kth.se
+ Subject: Time for ISO 10646?
+
+ To: Dave Crocker <dcrocker@mordor.stanford.edu>
+ Cc: ietf-822@dimacs.rutgers.edu, paf@comsol.se
+ From: =?ISO-8859-1?Q?Patrik_F=E4ltstr=F6m?= <paf@nada.kth.se>
+ Subject: Re: RFC-HDR care and feeding
+
+
+
+
+
+Moore Standards Track [Page 11]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ From: Nathaniel Borenstein <nsb@thumper.bellcore.com>
+ (=?iso-8859-8?b?7eXs+SDv4SDp7Oj08A==?=)
+ To: Greg Vaudreuil <gvaudre@NRI.Reston.VA.US>, Ned Freed
+ <ned@innosoft.com>, Keith Moore <moore@cs.utk.edu>
+ Subject: Test of new header generator
+ MIME-Version: 1.0
+ Content-type: text/plain; charset=ISO-8859-1
+
+ The following examples illustrate how text containing 'encoded-word's
+ which appear in a structured field body. The rules are slightly
+ different for fields defined as '*text' because "(" and ")" are not
+ recognized as 'comment' delimiters. [Section 5, paragraph (1)].
+
+ In each of the following examples, if the same sequence were to occur
+ in a '*text' field, the "displayed as" form would NOT be treated as
+ encoded words, but be identical to the "encoded form". This is
+ because each of the encoded-words in the following examples is
+ adjacent to a "(" or ")" character.
+
+ encoded form displayed as
+ ---------------------------------------------------------------------
+ (=?ISO-8859-1?Q?a?=) (a)
+
+ (=?ISO-8859-1?Q?a?= b) (a b)
+
+ Within a 'comment', white space MUST appear between an
+ 'encoded-word' and surrounding text. [Section 5,
+ paragraph (2)]. However, white space is not needed between
+ the initial "(" that begins the 'comment', and the
+ 'encoded-word'.
+
+
+ (=?ISO-8859-1?Q?a?= =?ISO-8859-1?Q?b?=) (ab)
+
+ White space between adjacent 'encoded-word's is not
+ displayed.
+
+ (=?ISO-8859-1?Q?a?= =?ISO-8859-1?Q?b?=) (ab)
+
+ Even multiple SPACEs between 'encoded-word's are ignored
+ for the purpose of display.
+
+ (=?ISO-8859-1?Q?a?= (ab)
+ =?ISO-8859-1?Q?b?=)
+
+ Any amount of linear-space-white between 'encoded-word's,
+ even if it includes a CRLF followed by one or more SPACEs,
+ is ignored for the purposes of display.
+
+
+
+Moore Standards Track [Page 12]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+ (=?ISO-8859-1?Q?a_b?=) (a b)
+
+ In order to cause a SPACE to be displayed within a portion
+ of encoded text, the SPACE MUST be encoded as part of the
+ 'encoded-word'.
+
+ (=?ISO-8859-1?Q?a?= =?ISO-8859-2?Q?_b?=) (a b)
+
+ In order to cause a SPACE to be displayed between two strings
+ of encoded text, the SPACE MAY be encoded as part of one of
+ the 'encoded-word's.
+
+9. References
+
+ [RFC 822] Crocker, D., "Standard for the Format of ARPA Internet Text
+ Messages", STD 11, RFC 822, UDEL, August 1982.
+
+ [RFC 2049] Borenstein, N., and N. Freed, "Multipurpose Internet Mail
+ Extensions (MIME) Part Five: Conformance Criteria and Examples",
+ RFC 2049, November 1996.
+
+ [RFC 2045] Borenstein, N., and N. Freed, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message Bodies",
+ RFC 2045, November 1996.
+
+ [RFC 2046] Borenstein N., and N. Freed, "Multipurpose Internet Mail
+ Extensions (MIME) Part Two: Media Types", RFC 2046,
+ November 1996.
+
+ [RFC 2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) Part Four: Registration
+ Procedures", RFC 2048, November 1996.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Moore Standards Track [Page 13]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+10. Security Considerations
+
+ Security issues are not discussed in this memo.
+
+11. Acknowledgements
+
+ The author wishes to thank Nathaniel Borenstein, Issac Chan, Lutz
+ Donnerhacke, Paul Eggert, Ned Freed, Andreas M. Kirchwitz, Olle
+ Jarnefors, Mike Rosin, Yutaka Sato, Bart Schaefer, and Kazuhiko
+ Yamamoto, for their helpful advice, insightful comments, and
+ illuminating questions in response to earlier versions of this
+ specification.
+
+12. Author's Address
+
+ Keith Moore
+ University of Tennessee
+ 107 Ayres Hall
+ Knoxville TN 37996-1301
+
+ EMail: moore@cs.utk.edu
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Moore Standards Track [Page 14]
+
+RFC 2047 Message Header Extensions November 1996
+
+
+Appendix - changes since RFC 1522 (in no particular order)
+
+ + explicitly state that the MIME-Version is not requried to use
+ 'encoded-word's.
+
+ + add explicit note that SPACEs and TABs are not allowed within
+ 'encoded-word's, explaining that an 'encoded-word' must look like an
+ 'atom' to an RFC822 parser.values, to be precise).
+
+ + add examples from Olle Jarnefors (thanks!) which illustrate how
+ encoded-words with adjacent linear-white-space are displayed.
+
+ + explicitly list terms defined in RFC822 and referenced in this memo
+
+ + fix transcription typos that caused one or two lines and a couple of
+ characters to disappear in the resulting text, due to nroff quirks.
+
+ + clarify that encoded-words are allowed in '*text' fields in both
+ RFC822 headers and MIME body part headers, but NOT as parameter
+ values.
+
+ + clarify the requirement to switch back to ASCII within the encoded
+ portion of an 'encoded-word', for any charset that uses code switching
+ sequences.
+
+ + add a note about 'encoded-word's being delimited by "(" and ")"
+ within a comment, but not in a *text (how bizarre!).
+
+ + fix the Andre Pirard example to get rid of the trailing "_" after
+ the =E9. (no longer needed post-1342).
+
+ + clarification: an 'encoded-word' may appear immediately following
+ the initial "(" or immediately before the final ")" that delimits a
+ comment, not just adjacent to "(" and ")" *within* *ctext.
+
+ + add a note to explain that a "B" 'encoded-word' will always have a
+ multiple of 4 characters in the 'encoded-text' portion.
+
+ + add note about the "=" in the examples
+
+ + note that processing of 'encoded-word's occurs *after* parsing, and
+ some of the implications thereof.
+
+ + explicitly state that you can't expect to translate between
+ 1522 and either vanilla 822 or so-called "8-bit headers".
+
+ + explicitly state that 'encoded-word's are not valid within a
+ 'quoted-string'.
+
+
+
+Moore Standards Track [Page 15]
+
diff --git a/rfc/rfc2048.txt b/rfc/rfc2048.txt
@@ -0,0 +1,1180 @@
+
+
+
+
+
+
+Network Working Group N. Freed
+Request for Comments: 2048 Innosoft
+BCP: 13 J. Klensin
+Obsoletes: 1521, 1522, 1590 MCI
+Category: Best Current Practice J. Postel
+ ISI
+ November 1996
+
+
+ Multipurpose Internet Mail Extensions
+ (MIME) Part Four:
+ Registration Procedures
+
+Status of this Memo
+
+ This document specifies an Internet Best Current Practices for the
+ Internet Community, and requests discussion and suggestions for
+ improvements. Distribution of this memo is unlimited.
+
+Abstract
+
+ STD 11, RFC 822, defines a message representation protocol specifying
+ considerable detail about US-ASCII message headers, and leaves the
+ message content, or message body, as flat US-ASCII text. This set of
+ documents, collectively called the Multipurpose Internet Mail
+ Extensions, or MIME, redefines the format of messages to allow for
+
+ (1) textual message bodies in character sets other than
+ US-ASCII,
+
+ (2) an extensible set of different formats for non-textual
+ message bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than
+ US-ASCII.
+
+ These documents are based on earlier work documented in RFC 934, STD
+ 11, and RFC 1049, but extends and revises them. Because RFC 822 said
+ so little about message bodies, these documents are largely
+ orthogonal to (rather than a revision of) RFC 822.
+
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 1]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ This fourth document, RFC 2048, specifies various IANA registration
+ procedures for the following MIME facilities:
+
+ (1) media types,
+
+ (2) external body access types,
+
+ (3) content-transfer-encodings.
+
+ Registration of character sets for use in MIME is covered elsewhere
+ and is no longer addressed by this document.
+
+ These documents are revisions of RFCs 1521 and 1522, which themselves
+ were revisions of RFCs 1341 and 1342. An appendix in RFC 2049
+ describes differences and changes from previous versions.
+
+Table of Contents
+
+ 1. Introduction ......................................... 3
+ 2. Media Type Registration .............................. 4
+ 2.1 Registration Trees and Subtype Names ................ 4
+ 2.1.1 IETF Tree ......................................... 4
+ 2.1.2 Vendor Tree ....................................... 4
+ 2.1.3 Personal or Vanity Tree ........................... 5
+ 2.1.4 Special `x.' Tree ................................. 5
+ 2.1.5 Additional Registration Trees ..................... 6
+ 2.2 Registration Requirements ........................... 6
+ 2.2.1 Functionality Requirement ......................... 6
+ 2.2.2 Naming Requirements ............................... 6
+ 2.2.3 Parameter Requirements ............................ 7
+ 2.2.4 Canonicalization and Format Requirements .......... 7
+ 2.2.5 Interchange Recommendations ....................... 8
+ 2.2.6 Security Requirements ............................. 8
+ 2.2.7 Usage and Implementation Non-requirements ......... 9
+ 2.2.8 Publication Requirements .......................... 10
+ 2.2.9 Additional Information ............................ 10
+ 2.3 Registration Procedure .............................. 11
+ 2.3.1 Present the Media Type to the Community for Review 11
+ 2.3.2 IESG Approval ..................................... 12
+ 2.3.3 IANA Registration ................................. 12
+ 2.4 Comments on Media Type Registrations ................ 12
+ 2.5 Location of Registered Media Type List .............. 12
+ 2.6 IANA Procedures for Registering Media Types ......... 12
+ 2.7 Change Control ...................................... 13
+ 2.8 Registration Template ............................... 14
+ 3. External Body Access Types ........................... 14
+ 3.1 Registration Requirements ........................... 15
+ 3.1.1 Naming Requirements ............................... 15
+
+
+
+Freed, et. al. Best Current Practice [Page 2]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ 3.1.2 Mechanism Specification Requirements .............. 15
+ 3.1.3 Publication Requirements .......................... 15
+ 3.1.4 Security Requirements ............................. 15
+ 3.2 Registration Procedure .............................. 15
+ 3.2.1 Present the Access Type to the Community .......... 16
+ 3.2.2 Access Type Reviewer .............................. 16
+ 3.2.3 IANA Registration ................................. 16
+ 3.3 Location of Registered Access Type List ............. 16
+ 3.4 IANA Procedures for Registering Access Types ........ 16
+ 4. Transfer Encodings ................................... 17
+ 4.1 Transfer Encoding Requirements ...................... 17
+ 4.1.1 Naming Requirements ............................... 17
+ 4.1.2 Algorithm Specification Requirements .............. 18
+ 4.1.3 Input Domain Requirements ......................... 18
+ 4.1.4 Output Range Requirements ......................... 18
+ 4.1.5 Data Integrity and Generality Requirements ........ 18
+ 4.1.6 New Functionality Requirements .................... 18
+ 4.2 Transfer Encoding Definition Procedure .............. 19
+ 4.3 IANA Procedures for Transfer Encoding Registration... 19
+ 4.4 Location of Registered Transfer Encodings List ...... 19
+ 5. Authors' Addresses ................................... 20
+ A. Grandfathered Media Types ............................ 21
+
+1. Introduction
+
+ Recent Internet protocols have been carefully designed to be easily
+ extensible in certain areas. In particular, MIME [RFC 2045] is an
+ open-ended framework and can accommodate additional object types,
+ character sets, and access methods without any changes to the basic
+ protocol. A registration process is needed, however, to ensure that
+ the set of such values is developed in an orderly, well-specified,
+ and public manner.
+
+ This document defines registration procedures which use the Internet
+ Assigned Numbers Authority (IANA) as a central registry for such
+ values.
+
+ Historical Note: The registration process for media types was
+ initially defined in the context of the asynchronous Internet mail
+ environment. In this mail environment there is a need to limit the
+ number of possible media types to increase the likelihood of
+ interoperability when the capabilities of the remote mail system are
+ not known. As media types are used in new environments, where the
+ proliferation of media types is not a hindrance to interoperability,
+ the original procedure was excessively restrictive and had to be
+ generalized.
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 3]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+2. Media Type Registration
+
+ Registration of a new media type or types starts with the
+ construction of a registration proposal. Registration may occur in
+ several different registration trees, which have different
+ requirements as discussed below. In general, the new registration
+ proposal is circulated and reviewed in a fashion appropriate to the
+ tree involved. The media type is then registered if the proposal is
+ acceptable. The following sections describe the requirements and
+ procedures used for each of the different registration trees.
+
+2.1. Registration Trees and Subtype Names
+
+ In order to increase the efficiency and flexibility of the
+ registration process, different structures of subtype names may be
+ registered to accomodate the different natural requirements for,
+ e.g., a subtype that will be recommended for wide support and
+ implementation by the Internet Community or a subtype that is used to
+ move files associated with proprietary software. The following
+ subsections define registration "trees", distinguished by the use of
+ faceted names (e.g., names of the form "tree.subtree...type"). Note
+ that some media types defined prior to this document do not conform
+ to the naming conventions described below. See Appendix A for a
+ discussion of them.
+
+2.1.1. IETF Tree
+
+ The IETF tree is intended for types of general interest to the
+ Internet Community. Registration in the IETF tree requires approval
+ by the IESG and publication of the media type registration as some
+ form of RFC.
+
+ Media types in the IETF tree are normally denoted by names that are
+ not explicitly faceted, i.e., do not contain period (".", full stop)
+ characters.
+
+ The "owner" of a media type registration in the IETF tree is assumed
+ to be the IETF itself. Modification or alteration of the
+ specification requires the same level of processing (e.g. standards
+ track) required for the initial registration.
+
+2.1.2. Vendor Tree
+
+ The vendor tree is used for media types associated with commercially
+ available products. "Vendor" or "producer" are construed as
+ equivalent and very broadly in this context.
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 4]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ A registration may be placed in the vendor tree by anyone who has
+ need to interchange files associated with the particular product.
+ However, the registration formally belongs to the vendor or
+ organization producing the software or file format. Changes to the
+ specification will be made at their request, as discussed in
+ subsequent sections.
+
+ Registrations in the vendor tree will be distinguished by the leading
+ facet "vnd.". That may be followed, at the discretion of the
+ registration, by either a media type name from a well-known producer
+ (e.g., "vnd.mudpie") or by an IANA-approved designation of the
+ producer's name which is then followed by a media type or product
+ designation (e.g., vnd.bigcompany.funnypictures).
+
+ While public exposure and review of media types to be registered in
+ the vendor tree is not required, using the ietf-types list for review
+ is strongly encouraged to improve the quality of those
+ specifications. Registrations in the vendor tree may be submitted
+ directly to the IANA.
+
+2.1.3. Personal or Vanity Tree
+
+ Registrations for media types created experimentally or as part of
+ products that are not distributed commercially may be registered in
+ the personal or vanity tree. The registrations are distinguished by
+ the leading facet "prs.".
+
+ The owner of "personal" registrations and associated specifications
+ is the person or entity making the registration, or one to whom
+ responsibility has been transferred as described below.
+
+ While public exposure and review of media types to be registered in
+ the personal tree is not required, using the ietf-types list for
+ review is strongly encouraged to improve the quality of those
+ specifications. Registrations in the personl tree may be submitted
+ directly to the IANA.
+
+2.1.4. Special `x.' Tree
+
+ For convenience and symmetry with this registration scheme, media
+ type names with "x." as the first facet may be used for the same
+ purposes for which names starting in "x-" are normally used. These
+ types are unregistered, experimental, and should be used only with
+ the active agreement of the parties exchanging them.
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 5]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ However, with the simplified registration procedures described above
+ for vendor and personal trees, it should rarely, if ever, be
+ necessary to use unregistered experimental types, and as such use of
+ both "x-" and "x." forms is discouraged.
+
+2.1.5. Additional Registration Trees
+
+ From time to time and as required by the community, the IANA may,
+ with the advice and consent of the IESG, create new top-level
+ registration trees. It is explicitly assumed that these trees may be
+ created for external registration and management by well-known
+ permanent bodies, such as scientific societies for media types
+ specific to the sciences they cover. In general, the quality of
+ review of specifications for one of these additional registration
+ trees is expected to be equivalent to that which IETF would give to
+ registrations in its own tree. Establishment of these new trees will
+ be announced through RFC publication approved by the IESG.
+
+2.2. Registration Requirements
+
+ Media type registration proposals are all expected to conform to
+ various requirements laid out in the following sections. Note that
+ requirement specifics sometimes vary depending on the registration
+ tree, again as detailed in the following sections.
+
+2.2.1. Functionality Requirement
+
+ Media types must function as an actual media format: Registration of
+ things that are better thought of as a transfer encoding, as a
+ character set, or as a collection of separate entities of another
+ type, is not allowed. For example, although applications exist to
+ decode the base64 transfer encoding [RFC 2045], base64 cannot be
+ registered as a media type.
+
+ This requirement applies regardless of the registration tree
+ involved.
+
+2.2.2. Naming Requirements
+
+ All registered media types must be assigned MIME type and subtype
+ names. The combination of these names then serves to uniquely
+ identify the media type and the format of the subtype name identifies
+ the registration tree.
+
+ The choice of top-level type name must take the nature of media type
+ involved into account. For example, media normally used for
+ representing still images should be a subtype of the image content
+ type, whereas media capable of representing audio information belongs
+
+
+
+Freed, et. al. Best Current Practice [Page 6]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ under the audio content type. See RFC 2046 for additional information
+ on the basic set of top-level types and their characteristics.
+
+ New subtypes of top-level types must conform to the restrictions of
+ the top-level type, if any. For example, all subtypes of the
+ multipart content type must use the same encapsulation syntax.
+
+ In some cases a new media type may not "fit" under any currently
+ defined top-level content type. Such cases are expected to be quite
+ rare. However, if such a case arises a new top-level type can be
+ defined to accommodate it. Such a definition must be done via
+ standards-track RFC; no other mechanism can be used to define
+ additional top-level content types.
+
+ These requirements apply regardless of the registration tree
+ involved.
+
+2.2.3. Parameter Requirements
+
+ Media types may elect to use one or more MIME content type
+ parameters, or some parameters may be automatically made available to
+ the media type by virtue of being a subtype of a content type that
+ defines a set of parameters applicable to any of its subtypes. In
+ either case, the names, values, and meanings of any parameters must
+ be fully specified when a media type is registered in the IETF tree,
+ and should be specified as completely as possible when media types
+ are registered in the vendor or personal trees.
+
+ New parameters must not be defined as a way to introduce new
+ functionality in types registered in the IETF tree, although new
+ parameters may be added to convey additional information that does
+ not otherwise change existing functionality. An example of this
+ would be a "revision" parameter to indicate a revision level of an
+ external specification such as JPEG. Similar behavior is encouraged
+ for media types registered in the vendor or personal trees but is not
+ required.
+
+2.2.4. Canonicalization and Format Requirements
+
+ All registered media types must employ a single, canonical data
+ format, regardless of registration tree.
+
+ A precise and openly available specification of the format of each
+ media type is required for all types registered in the IETF tree and
+ must at a minimum be referenced by, if it isn't actually included in,
+ the media type registration proposal itself.
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 7]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ The specifications of format and processing particulars may or may
+ not be publically available for media types registered in the vendor
+ tree, and such registration proposals are explicitly permitted to
+ include only a specification of which software and version produce or
+ process such media types. References to or inclusion of format
+ specifications in registration proposals is encouraged but not
+ required.
+
+ Format specifications are still required for registration in the
+ personal tree, but may be either published as RFCs or otherwise
+ deposited with IANA. The deposited specifications will meet the same
+ criteria as those required to register a well-known TCP port and, in
+ particular, need not be made public.
+
+ Some media types involve the use of patented technology. The
+ registration of media types involving patented technology is
+ specifically permitted. However, the restrictions set forth in RFC
+ 1602 on the use of patented technology in standards-track protocols
+ must be respected when the specification of a media type is part of a
+ standards-track protocol.
+
+2.2.5. Interchange Recommendations
+
+ Media types should, whenever possible, interoperate across as many
+ systems and applications as possible. However, some media types will
+ inevitably have problems interoperating across different platforms.
+ Problems with different versions, byte ordering, and specifics of
+ gateway handling can and will arise.
+
+ Universal interoperability of media types is not required, but known
+ interoperability issues should be identified whenever possible.
+ Publication of a media type does not require an exhaustive review of
+ interoperability, and the interoperability considerations section is
+ subject to continuing evaluation.
+
+ These recommendations apply regardless of the registration tree
+ involved.
+
+2.2.6. Security Requirements
+
+ An analysis of security issues is required for for all types
+ registered in the IETF Tree. (This is in accordance with the basic
+ requirements for all IETF protocols.) A similar analysis for media
+ types registered in the vendor or personal trees is encouraged but
+ not required. However, regardless of what security analysis has or
+ has not been done, all descriptions of security issues must be as
+ accurate as possible regardless of registration tree. In particular,
+ a statement that there are "no security issues associated with this
+
+
+
+Freed, et. al. Best Current Practice [Page 8]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ type" must not be confused with "the security issues associates with
+ this type have not been assessed".
+
+ There is absolutely no requirement that media types registered in any
+ tree be secure or completely free from risks. Nevertheless, all
+ known security risks must be identified in the registration of a
+ media type, again regardless of registration tree.
+
+ The security considerations section of all registrations is subject
+ to continuing evaluation and modification, and in particular may be
+ extended by use of the "comments on media types" mechanism described
+ in subsequent sections.
+
+ Some of the issues that should be looked at in a security analysis of
+ a media type are:
+
+ (1) Complex media types may include provisions for
+ directives that institute actions on a recipient's
+ files or other resources. In many cases provision is
+ made for originators to specify arbitrary actions in an
+ unrestricted fashion which may then have devastating
+ effects. See the registration of the
+ application/postscript media type in RFC 2046 for
+ an example of such directives and how to handle them.
+
+ (2) Complex media types may include provisions for
+ directives that institute actions which, while not
+ directly harmful to the recipient, may result in
+ disclosure of information that either facilitates a
+ subsequent attack or else violates a recipient's
+ privacy in some way. Again, the registration of the
+ application/postscript media type illustrates how such
+ directives can be handled.
+
+ (3) A media type might be targeted for applications that
+ require some sort of security assurance but not provide
+ the necessary security mechanisms themselves. For
+ example, a media type could be defined for storage of
+ confidential medical information which in turn requires
+ an external confidentiality service.
+
+2.2.7. Usage and Implementation Non-requirements
+
+ In the asynchronous mail environment, where information on the
+ capabilities of the remote mail agent is frequently not available to
+ the sender, maximum interoperability is attained by restricting the
+ number of media types used to those "common" formats expected to be
+ widely implemented. This was asserted in the past as a reason to
+
+
+
+Freed, et. al. Best Current Practice [Page 9]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ limit the number of possible media types and resulted in a
+ registration process with a significant hurdle and delay for those
+ registering media types.
+
+ However, the need for "common" media types does not require limiting
+ the registration of new media types. If a limited set of media types
+ is recommended for a particular application, that should be asserted
+ by a separate applicability statement specific for the application
+ and/or environment.
+
+ As such, universal support and implementation of a media type is NOT
+ a requirement for registration. If, however, a media type is
+ explicitly intended for limited use, this should be noted in its
+ registration.
+
+2.2.8. Publication Requirements
+
+ Proposals for media types registered in the IETF tree must be
+ published as RFCs. RFC publication of vendor and personal media type
+ proposals is encouraged but not required. In all cases IANA will
+ retain copies of all media type proposals and "publish" them as part
+ of the media types registration tree itself.
+
+ Other than in the IETF tree, the registration of a data type does not
+ imply endorsement, approval, or recommendation by IANA or IETF or
+ even certification that the specification is adequate. To become
+ Internet Standards, protocol, data objects, or whatever must go
+ through the IETF standards process. This is too difficult and too
+ lengthy a process for the convenient registration of media types.
+
+ The IETF tree exists for media types that do require require a
+ substantive review and approval process with the vendor and personal
+ trees exist for those that do not. It is expected that applicability
+ statements for particular applications will be published from time to
+ time that recommend implementation of, and support for, media types
+ that have proven particularly useful in those contexts.
+
+ As discussed above, registration of a top-level type requires
+ standards-track processing and, hence, RFC publication.
+
+2.2.9. Additional Information
+
+ Various sorts of optional information may be included in the
+ specification of a media type if it is available:
+
+ (1) Magic number(s) (length, octet values). Magic numbers
+ are byte sequences that are always present and thus can
+ be used to identify entities as being of a given media
+
+
+
+Freed, et. al. Best Current Practice [Page 10]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ type.
+
+ (2) File extension(s) commonly used on one or more
+ platforms to indicate that some file containing a given
+ type of media.
+
+ (3) Macintosh File Type code(s) (4 octets) used to label
+ files containing a given type of media.
+
+ Such information is often quite useful to implementors and if
+ available should be provided.
+
+2.3. Registration Procedure
+
+ The following procedure has been implemented by the IANA for review
+ and approval of new media types. This is not a formal standards
+ process, but rather an administrative procedure intended to allow
+ community comment and sanity checking without excessive time delay.
+ For registration in the IETF tree, the normal IETF processes should
+ be followed, treating posting of an internet-draft and announcement
+ on the ietf-types list (as described in the next subsection) as a
+ first step. For registrations in the vendor or personal tree, the
+ initial review step described below may be omitted and the type
+ registered directly by submitting the template and an explanation
+ directly to IANA (at iana@iana.org). However, authors of vendor or
+ personal media type specifications are encouraged to seek community
+ review and comment whenever that is feasible.
+
+2.3.1. Present the Media Type to the Community for Review
+
+ Send a proposed media type registration to the "ietf-types@iana.org"
+ mailing list for a two week review period. This mailing list has
+ been established for the purpose of reviewing proposed media and
+ access types. Proposed media types are not formally registered and
+ must not be used; the "x-" prefix specified in RFC 2045 can be used
+ until registration is complete.
+
+ The intent of the public posting is to solicit comments and feedback
+ on the choice of type/subtype name, the unambiguity of the references
+ with respect to versions and external profiling information, and a
+ review of any interoperability or security considerations. The
+ submitter may submit a revised registration, or withdraw the
+ registration completely, at any time.
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 11]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+2.3.2. IESG Approval
+
+ Media types registered in the IETF tree must be submitted to the IESG
+ for approval.
+
+2.3.3. IANA Registration
+
+ Provided that the media type meets the requirements for media types
+ and has obtained approval that is necessary, the author may submit
+ the registration request to the IANA, which will register the media
+ type and make the media type registration available to the community.
+
+2.4. Comments on Media Type Registrations
+
+ Comments on registered media types may be submitted by members of the
+ community to IANA. These comments will be passed on to the "owner"
+ of the media type if possible. Submitters of comments may request
+ that their comment be attached to the media type registration itself,
+ and if IANA approves of this the comment will be made accessible in
+ conjunction with the type registration itself.
+
+2.5. Location of Registered Media Type List
+
+ Media type registrations will be posted in the anonymous FTP
+ directory "ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/"
+ and all registered media types will be listed in the periodically
+ issued "Assigned Numbers" RFC [currently STD 2, RFC 1700]. The media
+ type description and other supporting material may also be published
+ as an Informational RFC by sending it to "rfc-editor@isi.edu" (please
+ follow the instructions to RFC authors [RFC-1543]).
+
+2.6. IANA Procedures for Registering Media Types
+
+ The IANA will only register media types in the IETF tree in response
+ to a communication from the IESG stating that a given registration
+ has been approved. Vendor and personal types will be registered by
+ the IANA automatically and without any formal review as long as the
+ following minimal conditions are met:
+
+ (1) Media types must function as an actual media format.
+ In particular, character sets and transfer encodings
+ may not be registered as media types.
+
+ (2) All media types must have properly formed type and
+ subtype names. All type names must be defined by a
+ standards-track RFC. All subtype names must be unique,
+ must conform to the MIME grammar for such names, and
+ must contain the proper tree prefix.
+
+
+
+Freed, et. al. Best Current Practice [Page 12]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ (3) Types registered in the personal tree must either
+ provide a format specification or a pointer to one.
+
+ (4) Any security considerations given must not be obviously
+ bogus. (It is neither possible nor necessary for the
+ IANA to conduct a comprehensive security review of
+ media type registrations. Nevertheless, IANA has the
+ authority to identify obviously incompetent material
+ and exclude it.)
+
+2.7. Change Control
+
+ Once a media type has been published by IANA, the author may request
+ a change to its definition. The descriptions of the different
+ registration trees above designate the "owners" of each type of
+ registration. The change request follows the same procedure as the
+ registration request:
+
+ (1) Publish the revised template on the ietf-types list.
+
+ (2) Leave at least two weeks for comments.
+
+ (3) Publish using IANA after formal review if required.
+
+ Changes should be requested only when there are serious omission or
+ errors in the published specification. When review is required, a
+ change request may be denied if it renders entities that were valid
+ under the previous definition invalid under the new definition.
+
+ The owner of a content type may pass responsibility for the content
+ type to another person or agency by informing IANA and the ietf-types
+ list; this can be done without discussion or review.
+
+ The IESG may reassign responsibility for a media type. The most
+ common case of this will be to enable changes to be made to types
+ where the author of the registration has died, moved out of contact
+ or is otherwise unable to make changes that are important to the
+ community.
+
+ Media type registrations may not be deleted; media types which are no
+ longer believed appropriate for use can be declared OBSOLETE by a
+ change to their "intended use" field; such media types will be
+ clearly marked in the lists published by IANA.
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 13]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+2.8. Registration Template
+
+ To: ietf-types@iana.org
+ Subject: Registration of MIME media type XXX/YYY
+
+ MIME media type name:
+
+ MIME subtype name:
+
+ Required parameters:
+
+ Optional parameters:
+
+ Encoding considerations:
+
+ Security considerations:
+
+ Interoperability considerations:
+
+ Published specification:
+
+ Applications which use this media type:
+
+ Additional information:
+
+ Magic number(s):
+ File extension(s):
+ Macintosh File Type Code(s):
+
+ Person & email address to contact for further information:
+
+ Intended usage:
+
+ (One of COMMON, LIMITED USE or OBSOLETE)
+
+ Author/Change controller:
+
+ (Any other information that the author deems interesting may be
+ added below this line.)
+
+3. External Body Access Types
+
+ RFC 2046 defines the message/external-body media type, whereby a MIME
+ entity can act as pointer to the actual body data in lieu of
+ including the data directly in the entity body. Each
+ message/external-body reference specifies an access type, which
+ determines the mechanism used to retrieve the actual body data. RFC
+ 2046 defines an initial set of access types, but allows for the
+
+
+
+Freed, et. al. Best Current Practice [Page 14]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+ registration of additional access types to accommodate new retrieval
+ mechanisms.
+
+3.1. Registration Requirements
+
+ New access type specifications must conform to a number of
+ requirements as described below.
+
+3.1.1. Naming Requirements
+
+ Each access type must have a unique name. This name appears in the
+ access-type parameter in the message/external-body content-type
+ header field, and must conform to MIME content type parameter syntax.
+
+3.1.2. Mechanism Specification Requirements
+
+ All of the protocols, transports, and procedures used by a given
+ access type must be described, either in the specification of the
+ access type itself or in some other publicly available specification,
+ in sufficient detail for the access type to be implemented by any
+ competent implementor. Use of secret and/or proprietary methods in
+ access types are expressly prohibited. The restrictions imposed by
+ RFC 1602 on the standardization of patented algorithms must be
+ respected as well.
+
+3.1.3. Publication Requirements
+
+ All access types must be described by an RFC. The RFC may be
+ informational rather than standards-track, although standard-track
+ review and approval are encouraged for all access types.
+
+3.1.4. Security Requirements
+
+ Any known security issues that arise from the use of the access type
+ must be completely and fully described. It is not required that the
+ access type be secure or that it be free from risks, but that the
+ known risks be identified. Publication of a new access type does not
+ require an exhaustive security review, and the security
+ considerations section is subject to continuing evaluation.
+ Additional security considerations should be addressed by publishing
+ revised versions of the access type specification.
+
+3.2. Registration Procedure
+
+ Registration of a new access type starts with the construction of a
+ draft of an RFC.
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 15]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+3.2.1. Present the Access Type to the Community
+
+ Send a proposed access type specification to the "ietf-
+ types@iana.org" mailing list for a two week review period. This
+ mailing list has been established for the purpose of reviewing
+ proposed access and media types. Proposed access types are not
+ formally registered and must not be used.
+
+ The intent of the public posting is to solicit comments and feedback
+ on the access type specification and a review of any security
+ considerations.
+
+3.2.2. Access Type Reviewer
+
+ When the two week period has passed, the access type reviewer, who is
+ appointed by the IETF Applications Area Director, either forwards the
+ request to iana@isi.edu, or rejects it because of significant
+ objections raised on the list.
+
+ Decisions made by the reviewer must be posted to the ietf-types
+ mailing list within 14 days. Decisions made by the reviewer may be
+ appealed to the IESG.
+
+3.2.3. IANA Registration
+
+ Provided that the access type has either passed review or has been
+ successfully appealed to the IESG, the IANA will register the access
+ type and make the registration available to the community. The
+ specification of the access type must also be published as an RFC.
+ Informational RFCs are published by sending them to "rfc-
+ editor@isi.edu" (please follow the instructions to RFC authors [RFC-
+ 1543]).
+
+3.3. Location of Registered Access Type List
+
+ Access type registrations will be posted in the anonymous FTP
+ directory "ftp://ftp.isi.edu/in-notes/iana/assignments/access-types/"
+ and all registered access types will be listed in the periodically
+ issued "Assigned Numbers" RFC [currently RFC-1700].
+
+3.4. IANA Procedures for Registering Access Types
+
+ The identity of the access type reviewer is communicated to the IANA
+ by the IESG. The IANA then only acts in response to access type
+ definitions that either are approved by the access type reviewer and
+ forwarded by the reviewer to the IANA for registration, or in
+ response to a communication from the IESG that an access type
+ definition appeal has overturned the access type reviewer's ruling.
+
+
+
+Freed, et. al. Best Current Practice [Page 16]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+4. Transfer Encodings
+
+ Transfer encodings are tranformations applied to MIME media types
+ after conversion to the media type's canonical form. Transfer
+ encodings are used for several purposes:
+
+ (1) Many transports, especially message transports, can
+ only handle data consisting of relatively short lines
+ of text. There can also be severe restrictions on what
+ characters can be used in these lines of text -- some
+ transports are restricted to a small subset of US-ASCII
+ and others cannot handle certain character sequences.
+ Transfer encodings are used to transform binary data
+ into textual form that can survive such transports.
+ Examples of this sort of transfer encoding include the
+ base64 and quoted-printable transfer encodings defined
+ in RFC 2045.
+
+ (2) Image, audio, video, and even application entities are
+ sometimes quite large. Compression algorithms are often
+ quite effective in reducing the size of large entities.
+ Transfer encodings can be used to apply general-purpose
+ non-lossy compression algorithms to MIME entities.
+
+ (3) Transport encodings can be defined as a means of
+ representing existing encoding formats in a MIME
+ context.
+
+ IMPORTANT: The standardization of a large numbers of different
+ transfer encodings is seen as a significant barrier to widespread
+ interoperability and is expressely discouraged. Nevertheless, the
+ following procedure has been defined to provide a means of defining
+ additional transfer encodings, should standardization actually be
+ justified.
+
+4.1. Transfer Encoding Requirements
+
+ Transfer encoding specifications must conform to a number of
+ requirements as described below.
+
+4.1.1. Naming Requirements
+
+ Each transfer encoding must have a unique name. This name appears in
+ the Content-Transfer-Encoding header field and must conform to the
+ syntax of that field.
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 17]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+4.1.2. Algorithm Specification Requirements
+
+ All of the algorithms used in a transfer encoding (e.g. conversion
+ to printable form, compression) must be described in their entirety
+ in the transfer encoding specification. Use of secret and/or
+ proprietary algorithms in standardized transfer encodings are
+ expressly prohibited. The restrictions imposed by RFC 1602 on the
+ standardization of patented algorithms must be respected as well.
+
+4.1.3. Input Domain Requirements
+
+ All transfer encodings must be applicable to an arbitrary sequence of
+ octets of any length. Dependence on particular input forms is not
+ allowed.
+
+ It should be noted that the 7bit and 8bit encodings do not conform to
+ this requirement. Aside from the undesireability of having
+ specialized encodings, the intent here is to forbid the addition of
+ additional encodings along the lines of 7bit and 8bit.
+
+4.1.4. Output Range Requirements
+
+ There is no requirement that a particular tranfer encoding produce a
+ particular form of encoded output. However, the output format for
+ each transfer encoding must be fully and completely documented. In
+ particular, each specification must clearly state whether the output
+ format always lies within the confines of 7bit data, 8bit data, or is
+ simply pure binary data.
+
+4.1.5. Data Integrity and Generality Requirements
+
+ All transfer encodings must be fully invertible on any platform; it
+ must be possible for anyone to recover the original data by
+ performing the corresponding decoding operation. Note that this
+ requirement effectively excludes all forms of lossy compression as
+ well as all forms of encryption from use as a transfer encoding.
+
+4.1.6. New Functionality Requirements
+
+ All transfer encodings must provide some sort of new functionality.
+ Some degree of functionality overlap with previously defined transfer
+ encodings is acceptable, but any new transfer encoding must also
+ offer something no other transfer encoding provides.
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 18]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+4.2. Transfer Encoding Definition Procedure
+
+ Definition of a new transfer encoding starts with the construction of
+ a draft of a standards-track RFC. The RFC must define the transfer
+ encoding precisely and completely, and must also provide substantial
+ justification for defining and standardizing a new transfer encoding.
+ This specification must then be presented to the IESG for
+ consideration. The IESG can
+
+ (1) reject the specification outright as being
+ inappropriate for standardization,
+
+ (2) approve the formation of an IETF working group to work
+ on the specification in accordance with IETF
+ procedures, or,
+
+ (3) accept the specification as-is and put it directly on
+ the standards track.
+
+ Transfer encoding specifications on the standards track follow normal
+ IETF rules for standards track documents. A transfer encoding is
+ considered to be defined and available for use once it is on the
+ standards track.
+
+4.3. IANA Procedures for Transfer Encoding Registration
+
+ There is no need for a special procedure for registering Transfer
+ Encodings with the IANA. All legitimate transfer encoding
+ registrations must appear as a standards-track RFC, so it is the
+ IESG's responsibility to notify the IANA when a new transfer encoding
+ has been approved.
+
+4.4. Location of Registered Transfer Encodings List
+
+ Transfer encoding registrations will be posted in the anonymous FTP
+ directory "ftp://ftp.isi.edu/in-notes/iana/assignments/transfer-
+ encodings/" and all registered transfer encodings will be listed in
+ the periodically issued "Assigned Numbers" RFC [currently RFC-1700].
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 19]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+5. Authors' Addresses
+
+ For more information, the authors of this document are best
+ contacted via Internet mail:
+
+ Ned Freed
+ Innosoft International, Inc.
+ 1050 East Garvey Avenue South
+ West Covina, CA 91790
+ USA
+
+ Phone: +1 818 919 3600
+ Fax: +1 818 919 3614
+ EMail: ned@innosoft.com
+
+
+ John Klensin
+ MCI
+ 2100 Reston Parkway
+ Reston, VA 22091
+
+ Phone: +1 703 715-7361
+ Fax: +1 703 715-7436
+ EMail: klensin@mci.net
+
+
+ Jon Postel
+ USC/Information Sciences Institute
+ 4676 Admiralty Way
+ Marina del Rey, CA 90292
+ USA
+
+
+ Phone: +1 310 822 1511
+ Fax: +1 310 823 6714
+ EMail: Postel@ISI.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 20]
+
+RFC 2048 MIME Registration Procedures November 1996
+
+
+Appendix A -- Grandfathered Media Types
+
+ A number of media types, registered prior to 1996, would, if
+ registered under the guidelines in this document, be placed into
+ either the vendor or personal trees. Reregistration of those types
+ to reflect the appropriate trees is encouraged, but not required.
+ Ownership and change control principles outlined in this document
+ apply to those types as if they had been registered in the trees
+ described above.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed, et. al. Best Current Practice [Page 21]
+
diff --git a/rfc/rfc2049.txt b/rfc/rfc2049.txt
@@ -0,0 +1,1347 @@
+
+
+
+
+
+
+Network Working Group N. Freed
+Request for Comments: 2049 Innosoft
+Obsoletes: 1521, 1522, 1590 N. Borenstein
+Category: Standards Track First Virtual
+ November 1996
+
+
+ Multipurpose Internet Mail Extensions
+ (MIME) Part Five:
+ Conformance Criteria and Examples
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ STD 11, RFC 822, defines a message representation protocol specifying
+ considerable detail about US-ASCII message headers, and leaves the
+ message content, or message body, as flat US-ASCII text. This set of
+ documents, collectively called the Multipurpose Internet Mail
+ Extensions, or MIME, redefines the format of messages to allow for
+
+ (1) textual message bodies in character sets other than
+ US-ASCII,
+
+ (2) an extensible set of different formats for non-textual
+ message bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than
+ US-ASCII.
+
+ These documents are based on earlier work documented in RFC 934, STD
+ 11, and RFC 1049, but extends and revises them. Because RFC 822 said
+ so little about message bodies, these documents are largely
+ orthogonal to (rather than a revision of) RFC 822.
+
+ The initial document in this set, RFC 2045, specifies the various
+ headers used to describe the structure of MIME messages. The second
+ document defines the general structure of the MIME media typing
+ system and defines an initial set of media types. The third
+ document, RFC 2047, describes extensions to RFC 822 to allow non-US-
+
+
+
+Freed & Borenstein Standards Track [Page 1]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ ASCII text data in Internet mail header fields. The fourth document,
+ RFC 2048, specifies various IANA registration procedures for MIME-
+ related facilities. This fifth and final document describes MIME
+ conformance criteria as well as providing some illustrative examples
+ of MIME message formats, acknowledgements, and the bibliography.
+
+ These documents are revisions of RFCs 1521, 1522, and 1590, which
+ themselves were revisions of RFCs 1341 and 1342. Appendix B of this
+ document describes differences and changes from previous versions.
+
+Table of Contents
+
+ 1. Introduction .......................................... 2
+ 2. MIME Conformance ...................................... 2
+ 3. Guidelines for Sending Email Data ..................... 6
+ 4. Canonical Encoding Model .............................. 9
+ 5. Summary ............................................... 12
+ 6. Security Considerations ............................... 12
+ 7. Authors' Addresses .................................... 12
+ 8. Acknowledgements ...................................... 13
+ A. A Complex Multipart Example ........................... 15
+ B. Changes from RFC 1521, 1522, and 1590 ................. 16
+ C. References ............................................ 20
+
+1. Introduction
+
+ The first and second documents in this set define MIME header fields
+ and the initial set of MIME media types. The third document
+ describes extensions to RFC822 formats to allow for character sets
+ other than US-ASCII. This document describes what portions of MIME
+ must be supported by a conformant MIME implementation. It also
+ describes various pitfalls of contemporary messaging systems as well
+ as the canonical encoding model MIME is based on.
+
+2. MIME Conformance
+
+ The mechanisms described in these documents are open-ended. It is
+ definitely not expected that all implementations will support all
+ available media types, nor that they will all share the same
+ extensions. In order to promote interoperability, however, it is
+ useful to define the concept of "MIME-conformance" to define a
+ certain level of implementation that allows the useful interworking
+ of messages with content that differs from US-ASCII text. In this
+ section, we specify the requirements for such conformance.
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 2]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ A mail user agent that is MIME-conformant MUST:
+
+ (1) Always generate a "MIME-Version: 1.0" header field in
+ any message it creates.
+
+ (2) Recognize the Content-Transfer-Encoding header field
+ and decode all received data encoded by either quoted-
+ printable or base64 implementations. The identity
+ transformations 7bit, 8bit, and binary must also be
+ recognized.
+
+ Any non-7bit data that is sent without encoding must be
+ properly labelled with a content-transfer-encoding of
+ 8bit or binary, as appropriate. If the underlying
+ transport does not support 8bit or binary (as SMTP
+ [RFC-821] does not), the sender is required to both
+ encode and label data using an appropriate Content-
+ Transfer-Encoding such as quoted-printable or base64.
+
+ (3) Must treat any unrecognized Content-Transfer-Encoding
+ as if it had a Content-Type of "application/octet-
+ stream", regardless of whether or not the actual
+ Content-Type is recognized.
+
+ (4) Recognize and interpret the Content-Type header field,
+ and avoid showing users raw data with a Content-Type
+ field other than text. Implementations must be able
+ to send at least text/plain messages, with the
+ character set specified with the charset parameter if
+ it is not US-ASCII.
+
+ (5) Ignore any content type parameters whose names they do
+ not recognize.
+
+ (6) Explicitly handle the following media type values, to
+ at least the following extents:
+
+ Text:
+
+ -- Recognize and display "text" mail with the
+ character set "US-ASCII."
+
+ -- Recognize other character sets at least to the
+ extent of being able to inform the user about what
+ character set the message uses.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 3]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ -- Recognize the "ISO-8859-*" character sets to the
+ extent of being able to display those characters that
+ are common to ISO-8859-* and US-ASCII, namely all
+ characters represented by octet values 1-127.
+
+ -- For unrecognized subtypes in a known character
+ set, show or offer to show the user the "raw" version
+ of the data after conversion of the content from
+ canonical form to local form.
+
+ -- Treat material in an unknown character set as if
+ it were "application/octet-stream".
+
+ Image, audio, and video:
+
+ -- At a minumum provide facilities to treat any
+ unrecognized subtypes as if they were
+ "application/octet-stream".
+
+ Application:
+
+ -- Offer the ability to remove either of the quoted-
+ printable or base64 encodings defined in this
+ document if they were used and put the resulting
+ information in a user file.
+
+ Multipart:
+
+ -- Recognize the mixed subtype. Display all relevant
+ information on the message level and the body part
+ header level and then display or offer to display
+ each of the body parts individually.
+
+ -- Recognize the "alternative" subtype, and avoid
+ showing the user redundant parts of
+ multipart/alternative mail.
+
+ -- Recognize the "multipart/digest" subtype,
+ specifically using "message/rfc822" rather than
+ "text/plain" as the default media type for body parts
+ inside "multipart/digest" entities.
+
+ -- Treat any unrecognized subtypes as if they were
+ "mixed".
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 4]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ Message:
+
+ -- Recognize and display at least the RFC822 message
+ encapsulation (message/rfc822) in such a way as to
+ preserve any recursive structure, that is, displaying
+ or offering to display the encapsulated data in
+ accordance with its media type.
+
+ -- Treat any unrecognized subtypes as if they were
+ "application/octet-stream".
+
+ (7) Upon encountering any unrecognized Content-Type field,
+ an implementation must treat it as if it had a media
+ type of "application/octet-stream" with no parameter
+ sub-arguments. How such data are handled is up to an
+ implementation, but likely options for handling such
+ unrecognized data include offering the user to write it
+ into a file (decoded from its mail transport format) or
+ offering the user to name a program to which the
+ decoded data should be passed as input.
+
+ (8) Conformant user agents are required, if they provide
+ non-standard support for non-MIME messages employing
+ character sets other than US-ASCII, to do so on
+ received messages only. Conforming user agents must not
+ send non-MIME messages containing anything other than
+ US-ASCII text.
+
+ In particular, the use of non-US-ASCII text in mail
+ messages without a MIME-Version field is strongly
+ discouraged as it impedes interoperability when sending
+ messages between regions with different localization
+ conventions. Conforming user agents MUST include proper
+ MIME labelling when sending anything other than plain
+ text in the US-ASCII character set.
+
+ In addition, non-MIME user agents should be upgraded if
+ at all possible to include appropriate MIME header
+ information in the messages they send even if nothing
+ else in MIME is supported. This upgrade will have
+ little, if any, effect on non-MIME recipients and will
+ aid MIME in correctly displaying such messages. It
+ also provides a smooth transition path to eventual
+ adoption of other MIME capabilities.
+
+ (9) Conforming user agents must ensure that any string of
+ non-white-space printable US-ASCII characters within a
+ "*text" or "*ctext" that begins with "=?" and ends with
+
+
+
+Freed & Borenstein Standards Track [Page 5]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ "?=" be a valid encoded-word. ("begins" means: At the
+ start of the field-body or immediately following
+ linear-white-space; "ends" means: At the end of the
+ field-body or immediately preceding linear-white-
+ space.) In addition, any "word" within a "phrase" that
+ begins with "=?" and ends with "?=" must be a valid
+ encoded-word.
+
+ (10) Conforming user agents must be able to distinguish
+ encoded-words from "text", "ctext", or "word"s,
+ according to the rules in section 4, anytime they
+ appear in appropriate places in message headers. It
+ must support both the "B" and "Q" encodings for any
+ character set which it supports. The program must be
+ able to display the unencoded text if the character set
+ is "US-ASCII". For the ISO-8859-* character sets, the
+ mail reading program must at least be able to display
+ the characters which are also in the US-ASCII set.
+
+ A user agent that meets the above conditions is said to be MIME-
+ conformant. The meaning of this phrase is that it is assumed to be
+ "safe" to send virtually any kind of properly-marked data to users of
+ such mail systems, because such systems will at least be able to
+ treat the data as undifferentiated binary, and will not simply splash
+ it onto the screen of unsuspecting users.
+
+ There is another sense in which it is always "safe" to send data in a
+ format that is MIME-conformant, which is that such data will not
+ break or be broken by any known systems that are conformant with RFC
+ 821 and RFC 822. User agents that are MIME-conformant have the
+ additional guarantee that the user will not be shown data that were
+ never intended to be viewed as text.
+
+3. Guidelines for Sending Email Data
+
+ Internet email is not a perfect, homogeneous system. Mail may become
+ corrupted at several stages in its travel to a final destination.
+ Specifically, email sent throughout the Internet may travel across
+ many networking technologies. Many networking and mail technologies
+ do not support the full functionality possible in the SMTP transport
+ environment. Mail traversing these systems is likely to be modified
+ in order that it can be transported.
+
+ There exist many widely-deployed non-conformant MTAs in the Internet.
+ These MTAs, speaking the SMTP protocol, alter messages on the fly to
+ take advantage of the internal data structure of the hosts they are
+ implemented on, or are just plain broken.
+
+
+
+
+Freed & Borenstein Standards Track [Page 6]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ The following guidelines may be useful to anyone devising a data
+ format (media type) that is supposed to survive the widest range of
+ networking technologies and known broken MTAs unscathed. Note that
+ anything encoded in the base64 encoding will satisfy these rules, but
+ that some well-known mechanisms, notably the UNIX uuencode facility,
+ will not. Note also that anything encoded in the Quoted-Printable
+ encoding will survive most gateways intact, but possibly not some
+ gateways to systems that use the EBCDIC character set.
+
+ (1) Under some circumstances the encoding used for data may
+ change as part of normal gateway or user agent
+ operation. In particular, conversion from base64 to
+ quoted-printable and vice versa may be necessary. This
+ may result in the confusion of CRLF sequences with line
+ breaks in text bodies. As such, the persistence of
+ CRLF as something other than a line break must not be
+ relied on.
+
+ (2) Many systems may elect to represent and store text data
+ using local newline conventions. Local newline
+ conventions may not match the RFC822 CRLF convention --
+ systems are known that use plain CR, plain LF, CRLF, or
+ counted records. The result is that isolated CR and LF
+ characters are not well tolerated in general; they may
+ be lost or converted to delimiters on some systems, and
+ hence must not be relied on.
+
+ (3) The transmission of NULs (US-ASCII value 0) is
+ problematic in Internet mail. (This is largely the
+ result of NULs being used as a termination character by
+ many of the standard runtime library routines in the C
+ programming language.) The practice of using NULs as
+ termination characters is so entrenched now that
+ messages should not rely on them being preserved.
+
+ (4) TAB (HT) characters may be misinterpreted or may be
+ automatically converted to variable numbers of spaces.
+ This is unavoidable in some environments, notably those
+ not based on the US-ASCII character set. Such
+ conversion is STRONGLY DISCOURAGED, but it may occur,
+ and mail formats must not rely on the persistence of
+ TAB (HT) characters.
+
+ (5) Lines longer than 76 characters may be wrapped or
+ truncated in some environments. Line wrapping or line
+ truncation imposed by mail transports is STRONGLY
+ DISCOURAGED, but unavoidable in some cases.
+ Applications which require long lines must somehow
+
+
+
+Freed & Borenstein Standards Track [Page 7]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ differentiate between soft and hard line breaks. (A
+ simple way to do this is to use the quoted-printable
+ encoding.)
+
+ (6) Trailing "white space" characters (SPACE, TAB (HT)) on
+ a line may be discarded by some transport agents, while
+ other transport agents may pad lines with these
+ characters so that all lines in a mail file are of
+ equal length. The persistence of trailing white space,
+ therefore, must not be relied on.
+
+ (7) Many mail domains use variations on the US-ASCII
+ character set, or use character sets such as EBCDIC
+ which contain most but not all of the US-ASCII
+ characters. The correct translation of characters not
+ in the "invariant" set cannot be depended on across
+ character converting gateways. For example, this
+ situation is a problem when sending uuencoded
+ information across BITNET, an EBCDIC system. Similar
+ problems can occur without crossing a gateway, since
+ many Internet hosts use character sets other than US-
+ ASCII internally. The definition of Printable Strings
+ in X.400 adds further restrictions in certain special
+ cases. In particular, the only characters that are
+ known to be consistent across all gateways are the 73
+ characters that correspond to the upper and lower case
+ letters A-Z and a-z, the 10 digits 0-9, and the
+ following eleven special characters:
+
+ "'" (US-ASCII decimal value 39)
+ "(" (US-ASCII decimal value 40)
+ ")" (US-ASCII decimal value 41)
+ "+" (US-ASCII decimal value 43)
+ "," (US-ASCII decimal value 44)
+ "-" (US-ASCII decimal value 45)
+ "." (US-ASCII decimal value 46)
+ "/" (US-ASCII decimal value 47)
+ ":" (US-ASCII decimal value 58)
+ "=" (US-ASCII decimal value 61)
+ "?" (US-ASCII decimal value 63)
+
+ A maximally portable mail representation will confine
+ itself to relatively short lines of text in which the
+ only meaningful characters are taken from this set of
+ 73 characters. The base64 encoding follows this rule.
+
+ (8) Some mail transport agents will corrupt data that
+ includes certain literal strings. In particular, a
+
+
+
+Freed & Borenstein Standards Track [Page 8]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ period (".") alone on a line is known to be corrupted
+ by some (incorrect) SMTP implementations, and a line
+ that starts with the five characters "From " (the fifth
+ character is a SPACE) are commonly corrupted as well.
+ A careful composition agent can prevent these
+ corruptions by encoding the data (e.g., in the quoted-
+ printable encoding using "=46rom " in place of "From "
+ at the start of a line, and "=2E" in place of "." alone
+ on a line).
+
+ Please note that the above list is NOT a list of recommended
+ practices for MTAs. RFC 821 MTAs are prohibited from altering the
+ character of white space or wrapping long lines. These BAD and
+ invalid practices are known to occur on established networks, and
+ implementations should be robust in dealing with the bad effects they
+ can cause.
+
+4. Canonical Encoding Model
+
+ There was some confusion, in earlier versions of these documents,
+ regarding the model for when email data was to be converted to
+ canonical form and encoded, and in particular how this process would
+ affect the treatment of CRLFs, given that the representation of
+ newlines varies greatly from system to system. For this reason, a
+ canonical model for encoding is presented below.
+
+ The process of composing a MIME entity can be modeled as being done
+ in a number of steps. Note that these steps are roughly similar to
+ those steps used in PEM [RFC-1421] and are performed for each
+ "innermost level" body:
+
+ (1) Creation of local form.
+
+ The body to be transmitted is created in the system's
+ native format. The native character set is used and,
+ where appropriate, local end of line conventions are
+ used as well. The body may be a UNIX-style text file,
+ or a Sun raster image, or a VMS indexed file, or audio
+ data in a system-dependent format stored only in
+ memory, or anything else that corresponds to the local
+ model for the representation of some form of
+ information. Fundamentally, the data is created in the
+ "native" form that corresponds to the type specified by
+ the media type.
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 9]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ (2) Conversion to canonical form.
+
+ The entire body, including "out-of-band" information
+ such as record lengths and possibly file attribute
+ information, is converted to a universal canonical
+ form. The specific media type of the body as well as
+ its associated attributes dictate the nature of the
+ canonical form that is used. Conversion to the proper
+ canonical form may involve character set conversion,
+ transformation of audio data, compression, or various
+ other operations specific to the various media types.
+ If character set conversion is involved, however, care
+ must be taken to understand the semantics of the media
+ type, which may have strong implications for any
+ character set conversion, e.g. with regard to
+ syntactically meaningful characters in a text subtype
+ other than "plain".
+
+ For example, in the case of text/plain data, the text
+ must be converted to a supported character set and
+ lines must be delimited with CRLF delimiters in
+ accordance with RFC 822. Note that the restriction on
+ line lengths implied by RFC 822 is eliminated if the
+ next step employs either quoted-printable or base64
+ encoding.
+
+ (3) Apply transfer encoding.
+
+ A Content-Transfer-Encoding appropriate for this body
+ is applied. Note that there is no fixed relationship
+ between the media type and the transfer encoding. In
+ particular, it may be appropriate to base the choice of
+ base64 or quoted-printable on character frequency
+ counts which are specific to a given instance of a
+ body.
+
+ (4) Insertion into entity.
+
+ The encoded body is inserted into a MIME entity with
+ appropriate headers. The entity is then inserted into
+ the body of a higher-level entity (message or
+ multipart) as needed.
+
+ Conversion from entity form to local form is accomplished by
+ reversing these steps. Note that reversal of these steps may produce
+ differing results since there is no guarantee that the original and
+ final local forms are the same.
+
+
+
+
+Freed & Borenstein Standards Track [Page 10]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ It is vital to note that these steps are only a model; they are
+ specifically NOT a blueprint for how an actual system would be built.
+ In particular, the model fails to account for two common designs:
+
+ (1) In many cases the conversion to a canonical form prior
+ to encoding will be subsumed into the encoder itself,
+ which understands local formats directly. For example,
+ the local newline convention for text bodies might be
+ carried through to the encoder itself along with
+ knowledge of what that format is.
+
+ (2) The output of the encoders may have to pass through one
+ or more additional steps prior to being transmitted as
+ a message. As such, the output of the encoder may not
+ be conformant with the formats specified by RFC 822.
+ In particular, once again it may be appropriate for the
+ converter's output to be expressed using local newline
+ conventions rather than using the standard RFC 822 CRLF
+ delimiters.
+
+ Other implementation variations are conceivable as well. The vital
+ aspect of this discussion is that, in spite of any optimizations,
+ collapsings of required steps, or insertion of additional processing,
+ the resulting messages must be consistent with those produced by the
+ model described here. For example, a message with the following
+ header fields:
+
+ Content-type: text/foo; charset=bar
+ Content-Transfer-Encoding: base64
+
+ must be first represented in the text/foo form, then (if necessary)
+ represented in the "bar" character set, and finally transformed via
+ the base64 algorithm into a mail-safe form.
+
+ NOTE: Some confusion has been caused by systems that represent
+ messages in a format which uses local newline conventions which
+ differ from the RFC822 CRLF convention. It is important to note that
+ these formats are not canonical RFC822/MIME. These formats are
+ instead *encodings* of RFC822, where CRLF sequences in the canonical
+ representation of the message are encoded as the local newline
+ convention. Note that formats which encode CRLF sequences as, for
+ example, LF are not capable of representing MIME messages containing
+ binary data which contains LF octets not part of CRLF line separation
+ sequences.
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 11]
+
+RFC 2049 MIME Conformance November 1996
+
+
+5. Summary
+
+ This document defines what is meant by MIME Conformance. It also
+ details various problems known to exist in the Internet email system
+ and how to use MIME to overcome them. Finally, it describes MIME's
+ canonical encoding model.
+
+6. Security Considerations
+
+ Security issues are discussed in the second document in this set, RFC
+ 2046.
+
+7. Authors' Addresses
+
+ For more information, the authors of this document are best contacted
+ via Internet mail:
+
+ Ned Freed
+ Innosoft International, Inc.
+ 1050 East Garvey Avenue South
+ West Covina, CA 91790
+ USA
+
+ Phone: +1 818 919 3600
+ Fax: +1 818 919 3614
+ EMail: ned@innosoft.com
+
+ Nathaniel S. Borenstein
+ First Virtual Holdings
+ 25 Washington Avenue
+ Morristown, NJ 07960
+ USA
+
+ Phone: +1 201 540 8967
+ Fax: +1 201 993 3032
+ EMail: nsb@nsb.fv.com
+
+ MIME is a result of the work of the Internet Engineering Task Force
+ Working Group on RFC 822 Extensions. The chairman of that group,
+ Greg Vaudreuil, may be reached at:
+
+ Gregory M. Vaudreuil
+ Octel Network Services
+ 17080 Dallas Parkway
+ Dallas, TX 75248-1905
+ USA
+
+ EMail: Greg.Vaudreuil@Octel.Com
+
+
+
+Freed & Borenstein Standards Track [Page 12]
+
+RFC 2049 MIME Conformance November 1996
+
+
+8. Acknowledgements
+
+ This document is the result of the collective effort of a large
+ number of people, at several IETF meetings, on the IETF-SMTP and
+ IETF-822 mailing lists, and elsewhere. Although any enumeration
+ seems doomed to suffer from egregious omissions, the following are
+ among the many contributors to this effort:
+
+ Harald Tveit Alvestrand Marc Andreessen
+ Randall Atkinson Bob Braden
+ Philippe Brandon Brian Capouch
+ Kevin Carosso Uhhyung Choi
+ Peter Clitherow Dave Collier-Brown
+ Cristian Constantinof John Coonrod
+ Mark Crispin Dave Crocker
+ Stephen Crocker Terry Crowley
+ Walt Daniels Jim Davis
+ Frank Dawson Axel Deininger
+ Hitoshi Doi Kevin Donnelly
+ Steve Dorner Keith Edwards
+ Chris Eich Dana S. Emery
+ Johnny Eriksson Craig Everhart
+ Patrik Faltstrom Erik E. Fair
+ Roger Fajman Alain Fontaine
+ Martin Forssen James M. Galvin
+ Stephen Gildea Philip Gladstone
+ Thomas Gordon Keld Simonsen
+ Terry Gray Phill Gross
+ James Hamilton David Herron
+ Mark Horton Bruce Howard
+ Bill Janssen Olle Jarnefors
+ Risto Kankkunen Phil Karn
+ Alan Katz Tim Kehres
+ Neil Katin Steve Kille
+ Kyuho Kim Anders Klemets
+ John Klensin Valdis Kletniek
+ Jim Knowles Stev Knowles
+ Bob Kummerfeld Pekka Kytolaakso
+ Stellan Lagerstrom Vincent Lau
+ Timo Lehtinen Donald Lindsay
+ Warner Losh Carlyn Lowery
+ Laurence Lundblade Charles Lynn
+ John R. MacMillan Larry Masinter
+ Rick McGowan Michael J. McInerny
+ Leo Mclaughlin Goli Montaser-Kohsari
+ Tom Moore John Gardiner Myers
+ Erik Naggum Mark Needleman
+ Chris Newman John Noerenberg
+
+
+
+Freed & Borenstein Standards Track [Page 13]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ Mats Ohrman Julian Onions
+ Michael Patton David J. Pepper
+ Erik van der Poel Blake C. Ramsdell
+ Christer Romson Luc Rooijakkers
+ Marshall T. Rose Jonathan Rosenberg
+ Guido van Rossum Jan Rynning
+ Harri Salminen Michael Sanderson
+ Yutaka Sato Markku Savela
+ Richard Alan Schafer Masahiro Sekiguchi
+ Mark Sherman Bob Smart
+ Peter Speck Henry Spencer
+ Einar Stefferud Michael Stein
+ Klaus Steinberger Peter Svanberg
+ James Thompson Steve Uhler
+ Stuart Vance Peter Vanderbilt
+ Greg Vaudreuil Ed Vielmetti
+ Larry W. Virden Ryan Waldron
+ Rhys Weatherly Jay Weber
+ Dave Wecker Wally Wedel
+ Sven-Ove Westberg Brian Wideen
+ John Wobus Glenn Wright
+ Rayan Zachariassen David Zimmerman
+
+ The authors apologize for any omissions from this list, which are
+ certainly unintentional.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 14]
+
+RFC 2049 MIME Conformance November 1996
+
+
+Appendix A -- A Complex Multipart Example
+
+ What follows is the outline of a complex multipart message. This
+ message contains five parts that are to be displayed serially: two
+ introductory plain text objects, an embedded multipart message, a
+ text/enriched object, and a closing encapsulated text message in a
+ non-ASCII character set. The embedded multipart message itself
+ contains two objects to be displayed in parallel, a picture and an
+ audio fragment.
+
+ MIME-Version: 1.0
+ From: Nathaniel Borenstein <nsb@nsb.fv.com>
+ To: Ned Freed <ned@innosoft.com>
+ Date: Fri, 07 Oct 1994 16:15:05 -0700 (PDT)
+ Subject: A multipart example
+ Content-Type: multipart/mixed;
+ boundary=unique-boundary-1
+
+ This is the preamble area of a multipart message.
+ Mail readers that understand multipart format
+ should ignore this preamble.
+
+ If you are reading this text, you might want to
+ consider changing to a mail reader that understands
+ how to properly display multipart messages.
+
+ --unique-boundary-1
+
+ ... Some text appears here ...
+
+ [Note that the blank between the boundary and the start
+ of the text in this part means no header fields were
+ given and this is text in the US-ASCII character set.
+ It could have been done with explicit typing as in the
+ next part.]
+
+ --unique-boundary-1
+ Content-type: text/plain; charset=US-ASCII
+
+ This could have been part of the previous part, but
+ illustrates explicit versus implicit typing of body
+ parts.
+
+ --unique-boundary-1
+ Content-Type: multipart/parallel; boundary=unique-boundary-2
+
+ --unique-boundary-2
+ Content-Type: audio/basic
+
+
+
+Freed & Borenstein Standards Track [Page 15]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ Content-Transfer-Encoding: base64
+
+ ... base64-encoded 8000 Hz single-channel
+ mu-law-format audio data goes here ...
+
+ --unique-boundary-2
+ Content-Type: image/jpeg
+ Content-Transfer-Encoding: base64
+
+ ... base64-encoded image data goes here ...
+
+ --unique-boundary-2--
+
+ --unique-boundary-1
+ Content-type: text/enriched
+
+ This is <bold><italic>enriched.</italic></bold>
+ <smaller>as defined in RFC 1896</smaller>
+
+ Isn't it
+ <bigger><bigger>cool?</bigger></bigger>
+
+ --unique-boundary-1
+ Content-Type: message/rfc822
+
+ From: (mailbox in US-ASCII)
+ To: (address in US-ASCII)
+ Subject: (subject in US-ASCII)
+ Content-Type: Text/plain; charset=ISO-8859-1
+ Content-Transfer-Encoding: Quoted-printable
+
+ ... Additional text in ISO-8859-1 goes here ...
+
+ --unique-boundary-1--
+
+Appendix B -- Changes from RFC 1521, 1522, and 1590
+
+ These documents are a revision of RFC 1521, 1522, and 1590. For the
+ convenience of those familiar with the earlier documents, the changes
+ from those documents are summarized in this appendix. For further
+ history, note that Appendix H in RFC 1521 specified how that document
+ differed from its predecessor, RFC 1341.
+
+ (1) This document has been completely reformatted and split
+ into multiple documents. This was done to improve the
+ quality of the plain text version of this document,
+ which is required to be the reference copy.
+
+
+
+
+Freed & Borenstein Standards Track [Page 16]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ (2) BNF describing the overall structure of MIME object
+ headers has been added. This is a documentation change
+ only -- the underlying syntax has not changed in any
+ way.
+
+ (3) The specific BNF for the seven media types in MIME has
+ been removed. This BNF was incorrect, incomplete, amd
+ inconsistent with the type-indendependent BNF. And
+ since the type-independent BNF already fully specifies
+ the syntax of the various MIME headers, the type-
+ specific BNF was, in the final analysis, completely
+ unnecessary and caused more problems than it solved.
+
+ (4) The more specific "US-ASCII" character set name has
+ replaced the use of the informal term ASCII in many
+ parts of these documents.
+
+ (5) The informal concept of a primary subtype has been
+ removed.
+
+ (6) The term "object" was being used inconsistently. The
+ definition of this term has been clarified, along with
+ the related terms "body", "body part", and "entity",
+ and usage has been corrected where appropriate.
+
+ (7) The BNF for the multipart media type has been
+ rearranged to make it clear that the CRLF preceeding
+ the boundary marker is actually part of the marker
+ itself rather than the preceeding body part.
+
+ (8) The prose and BNF describing the multipart media type
+ have been changed to make it clear that the body parts
+ within a multipart object MUST NOT contain any lines
+ beginning with the boundary parameter string.
+
+ (9) In the rules on reassembling "message/partial" MIME
+ entities, "Subject" is added to the list of headers to
+ take from the inner message, and the example is
+ modified to clarify this point.
+
+ (10) "Message/partial" fragmenters are restricted to
+ splitting MIME objects only at line boundaries.
+
+ (11) In the discussion of the application/postscript type,
+ an additional paragraph has been added warning about
+ possible interoperability problems caused by embedding
+ of binary data inside a PostScript MIME entity.
+
+
+
+
+Freed & Borenstein Standards Track [Page 17]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ (12) Added a clarifying note to the basic syntax rules for
+ the Content-Type header field to make it clear that the
+ following two forms:
+
+ Content-type: text/plain; charset=us-ascii (comment)
+
+ Content-type: text/plain; charset="us-ascii"
+
+ are completely equivalent.
+
+ (13) The following sentence has been removed from the
+ discussion of the MIME-Version header: "However,
+ conformant software is encouraged to check the version
+ number and at least warn the user if an unrecognized
+ MIME-version is encountered."
+
+ (14) A typo was fixed that said "application/external-body"
+ instead of "message/external-body".
+
+ (15) The definition of a character set has been reorganized
+ to make the requirements clearer.
+
+ (16) The definition of the "image/gif" media type has been
+ moved to a separate document. This change was made
+ because of potential conflicts with IETF rules
+ governing the standardization of patented technology.
+
+ (17) The definitions of "7bit" and "8bit" have been
+ tightened so that use of bare CR, LF can only be used
+ as end-of-line sequences. The document also no longer
+ requires that NUL characters be preserved, which brings
+ MIME into alignment with real-world implementations.
+
+ (18) The definition of canonical text in MIME has been
+ tightened so that line breaks must be represented by a
+ CRLF sequence. CR and LF characters are not allowed
+ outside of this usage. The definition of quoted-
+ printable encoding has been altered accordingly.
+
+ (19) The definition of the quoted-printable encoding now
+ includes a number of suggestions for how quoted-
+ printable encoders might best handle improperly encoded
+ material.
+
+ (20) Prose was added to clarify the use of the "7bit",
+ "8bit", and "binary" transfer-encodings on multipart or
+ message entities encapsulating "8bit" or "binary" data.
+
+
+
+
+Freed & Borenstein Standards Track [Page 18]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ (21) In the section on MIME Conformance, "multipart/digest"
+ support was added to the list of requirements for
+ minimal MIME conformance. Also, the requirement for
+ "message/rfc822" support were strengthened to clarify
+ the importance of recognizing recursive structure.
+
+ (22) The various restrictions on subtypes of "message" are
+ now specified entirely on a subtype by subtype basis.
+
+ (23) The definition of "message/rfc822" was changed to
+ indicate that at least one of the "From", "Subject", or
+ "Date" headers must be present.
+
+ (24) The required handling of unrecognized subtypes as
+ "application/octet-stream" has been made more explicit
+ in both the type definitions sections and the
+ conformance guidelines.
+
+ (25) Examples using text/richtext were changed to
+ text/enriched.
+
+ (26) The BNF definition of subtype has been changed to make
+ it clear that either an IANA registered subtype or a
+ nonstandard "X-" subtype must be used in a Content-Type
+ header field.
+
+ (27) MIME media types that are simply registered for use and
+ those that are standardized by the IETF are now
+ distinguished in the MIME BNF.
+
+ (28) All of the various MIME registration procedures have
+ been extensively revised. IANA registration procedures
+ for character sets have been moved to a separate
+ document that is no included in this set of documents.
+
+ (29) The use of escape and shift mechanisms in the US-ASCII
+ and ISO-8859-X character sets these documents define
+ have been clarified: Such mechanisms should never be
+ used in conjunction with these character sets and their
+ effect if they are used is undefined.
+
+ (30) The definition of the AFS access-type for
+ message/external-body has been removed.
+
+ (31) The handling of the combination of
+ multipart/alternative and message/external-body is now
+ specifically addressed.
+
+
+
+
+Freed & Borenstein Standards Track [Page 19]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ (32) Security issues specific to message/external-body are
+ now discussed in some detail.
+
+Appendix C -- References
+
+ [ATK]
+ Borenstein, Nathaniel S., Multimedia Applications
+ Development with the Andrew Toolkit, Prentice-Hall, 1990.
+
+ [ISO-2022]
+ International Standard -- Information Processing --
+ Character Code Structure and Extension Techniques,
+ ISO/IEC 2022:1994, 4th ed.
+
+ [ISO-8859]
+ International Standard -- Information Processing -- 8-bit
+ Single-Byte Coded Graphic Character Sets
+ - Part 1: Latin Alphabet No. 1, ISO 8859-1:1987, 1st ed.
+ - Part 2: Latin Alphabet No. 2, ISO 8859-2:1987, 1st ed.
+ - Part 3: Latin Alphabet No. 3, ISO 8859-3:1988, 1st ed.
+ - Part 4: Latin Alphabet No. 4, ISO 8859-4:1988, 1st ed.
+ - Part 5: Latin/Cyrillic Alphabet, ISO 8859-5:1988, 1st
+ ed.
+ - Part 6: Latin/Arabic Alphabet, ISO 8859-6:1987, 1st ed.
+ - Part 7: Latin/Greek Alphabet, ISO 8859-7:1987, 1st ed.
+ - Part 8: Latin/Hebrew Alphabet, ISO 8859-8:1988, 1st ed.
+ - Part 9: Latin Alphabet No. 5, ISO/IEC 8859-9:1989, 1st
+ ed.
+ International Standard -- Information Technology -- 8-bit
+ Single-Byte Coded Graphic Character Sets
+ - Part 10: Latin Alphabet No. 6, ISO/IEC 8859-10:1992,
+ 1st ed.
+
+ [ISO-646]
+ International Standard -- Information Technology -- ISO
+ 7-bit Coded Character Set for Information Interchange,
+ ISO 646:1991, 3rd ed..
+
+ [JPEG]
+ JPEG Draft Standard ISO 10918-1 CD.
+
+ [MPEG]
+ Video Coding Draft Standard ISO 11172 CD, ISO
+ IEC/JTC1/SC2/WG11 (Motion Picture Experts Group), May,
+ 1991.
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 20]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ [PCM]
+ CCITT, Fascicle III.4 - Recommendation G.711, "Pulse Code
+ Modulation (PCM) of Voice Frequencies", Geneva, 1972.
+
+ [POSTSCRIPT]
+ Adobe Systems, Inc., PostScript Language Reference
+ Manual, Addison-Wesley, 1985.
+
+ [POSTSCRIPT2]
+ Adobe Systems, Inc., PostScript Language Reference
+ Manual, Addison-Wesley, Second Ed., 1990.
+
+ [RFC-783]
+ Sollins, K.R., "TFTP Protocol (revision 2)", RFC-783,
+ MIT, June 1981.
+
+ [RFC-821]
+ Postel, J.B., "Simple Mail Transfer Protocol", STD 10,
+ RFC 821, USC/Information Sciences Institute, August 1982.
+
+ [RFC-822]
+ Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822, UDEL, August 1982.
+
+ [RFC-934]
+ Rose, M. and E. Stefferud, "Proposed Standard for Message
+ Encapsulation", RFC 934, Delaware and NMA, January 1985.
+
+ [RFC-959]
+ Postel, J. and J. Reynolds, "File Transfer Protocol", STD
+ 9, RFC 959, USC/Information Sciences Institute, October
+ 1985.
+
+ [RFC-1049]
+ Sirbu, M., "Content-Type Header Field for Internet
+ Messages", RFC 1049, CMU, March 1988.
+
+ [RFC-1154]
+ Robinson, D., and R. Ullmann, "Encoding Header Field for
+ Internet Messages", RFC 1154, Prime Computer, Inc., April
+ 1990.
+
+ [RFC-1341]
+ Borenstein, N., and N. Freed, "MIME (Multipurpose
+ Internet Mail Extensions): Mechanisms for Specifying and
+ Describing the Format of Internet Message Bodies", RFC
+ 1341, Bellcore, Innosoft, June 1992.
+
+
+
+
+Freed & Borenstein Standards Track [Page 21]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ [RFC-1342]
+ Moore, K., "Representation of Non-Ascii Text in Internet
+ Message Headers", RFC 1342, University of Tennessee, June
+ 1992.
+
+ [RFC-1344]
+ Borenstein, N., "Implications of MIME for Internet Mail
+ Gateways", RFC 1344, Bellcore, June 1992.
+
+ [RFC-1345]
+ Simonsen, K., "Character Mnemonics & Character Sets", RFC
+ 1345, Rationel Almen Planlaegning, June 1992.
+
+ [RFC-1421]
+ Linn, J., "Privacy Enhancement for Internet Electronic
+ Mail: Part I -- Message Encryption and Authentication
+ Procedures", RFC 1421, IAB IRTF PSRG, IETF PEM WG,
+ February 1993.
+
+ [RFC-1422]
+ Kent, S., "Privacy Enhancement for Internet Electronic
+ Mail: Part II -- Certificate-Based Key Management", RFC
+ 1422, IAB IRTF PSRG, IETF PEM WG, February 1993.
+
+ [RFC-1423]
+ Balenson, D., "Privacy Enhancement for Internet
+ Electronic Mail: Part III -- Algorithms, Modes, and
+ Identifiers", IAB IRTF PSRG, IETF PEM WG, February 1993.
+
+ [RFC-1424]
+ Kaliski, B., "Privacy Enhancement for Internet Electronic
+ Mail: Part IV -- Key Certification and Related
+ Services", IAB IRTF PSRG, IETF PEM WG, February 1993.
+
+ [RFC-1521]
+ Borenstein, N., and Freed, N., "MIME (Multipurpose
+ Internet Mail Extensions): Mechanisms for Specifying and
+ Describing the Format of Internet Message Bodies", RFC
+ 1521, Bellcore, Innosoft, September, 1993.
+
+ [RFC-1522]
+ Moore, K., "Representation of Non-ASCII Text in Internet
+ Message Headers", RFC 1522, University of Tennessee,
+ September 1993.
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 22]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ [RFC-1524]
+ Borenstein, N., "A User Agent Configuration Mechanism for
+ Multimedia Mail Format Information", RFC 1524, Bellcore,
+ September 1993.
+
+ [RFC-1543]
+ Postel, J., "Instructions to RFC Authors", RFC 1543,
+ USC/Information Sciences Institute, October 1993.
+
+ [RFC-1556]
+ Nussbacher, H., "Handling of Bi-directional Texts in
+ MIME", RFC 1556, Israeli Inter-University Computer
+ Center, December 1993.
+
+ [RFC-1590]
+ Postel, J., "Media Type Registration Procedure", RFC
+ 1590, USC/Information Sciences Institute, March 1994.
+
+ [RFC-1602]
+ Internet Architecture Board, Internet Engineering
+ Steering Group, Huitema, C., Gross, P., "The Internet
+ Standards Process -- Revision 2", March 1994.
+
+ [RFC-1652]
+ Klensin, J., (WG Chair), Freed, N., (Editor), Rose, M.,
+ Stefferud, E., and Crocker, D., "SMTP Service Extension
+ for 8bit-MIME transport", RFC 1652, United Nations
+ University, Innosoft, Dover Beach Consulting, Inc.,
+ Network Management Associates, Inc., The Branch Office,
+ March 1994.
+
+ [RFC-1700]
+ Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,
+ RFC 1700, USC/Information Sciences Institute, October
+ 1994.
+
+ [RFC-1741]
+ Faltstrom, P., Crocker, D., and Fair, E., "MIME Content
+ Type for BinHex Encoded Files", December 1994.
+
+ [RFC-1896]
+ Resnick, P., and A. Walker, "The text/enriched MIME
+ Content-type", RFC 1896, February, 1996.
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 23]
+
+RFC 2049 MIME Conformance November 1996
+
+
+ [RFC-2045]
+ Freed, N., and and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, Innosoft, First Virtual Holdings,
+ November 1996.
+
+ [RFC-2046]
+ Freed, N., and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Two: Media Types", RFC 2046,
+ Innosoft, First Virtual Holdings, November 1996.
+
+ [RFC-2047]
+ Moore, K., "Multipurpose Internet Mail Extensions (MIME)
+ Part Three: Representation of Non-ASCII Text in Internet
+ Message Headers", RFC 2047, University of
+ Tennessee, November 1996.
+
+ [RFC-2048]
+ Freed, N., Klensin, J., and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) Part Four: MIME
+ Registration Procedures", RFC 2048, Innosoft, MCI,
+ ISI, November 1996.
+
+ [RFC-2049]
+ Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Five: Conformance Criteria and
+ Examples", RFC 2049 (this document), Innosoft, First
+ Virtual Holdings, November 1996.
+
+ [US-ASCII]
+ Coded Character Set -- 7-Bit American Standard Code for
+ Information Interchange, ANSI X3.4-1986.
+
+ [X400]
+ Schicker, Pietro, "Message Handling Systems, X.400",
+ Message Handling Systems and Distributed Applications, E.
+ Stefferud, O-j. Jacobsen, and P. Schicker, eds., North-
+ Holland, 1989, pp. 3-41.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Borenstein Standards Track [Page 24]
+
diff --git a/rfc/rfc2183.txt b/rfc/rfc2183.txt
@@ -0,0 +1,675 @@
+
+
+
+
+
+
+Network Working Group R. Troost
+Request for Comments: 2183 New Century Systems
+Updates: 1806 S. Dorner
+Category: Standards Track QUALCOMM Incorporated
+ K. Moore, Editor
+ University of Tennessee
+ August 1997
+
+
+ Communicating Presentation Information in
+ Internet Messages:
+ The Content-Disposition Header Field
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This memo provides a mechanism whereby messages conforming to the
+ MIME specifications [RFC 2045, RFC 2046, RFC 2047, RFC 2048, RFC
+ 2049] can convey presentational information. It specifies the
+ "Content-Disposition" header field, which is optional and valid for
+ any MIME entity ("message" or "body part"). Two values for this
+ header field are described in this memo; one for the ordinary linear
+ presentation of the body part, and another to facilitate the use of
+ mail to transfer files. It is expected that more values will be
+ defined in the future, and procedures are defined for extending this
+ set of values.
+
+ This document is intended as an extension to MIME. As such, the
+ reader is assumed to be familiar with the MIME specifications, and
+ [RFC 822]. The information presented herein supplements but does not
+ replace that found in those documents.
+
+ This document is a revision to the Experimental protocol defined in
+ RFC 1806. As compared to RFC 1806, this document contains minor
+ editorial updates, adds new parameters needed to support the File
+ Transfer Body Part, and references a separate specification for the
+ handling of non-ASCII and/or very long parameter values.
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 1]
+
+RFC 2183 Content-Disposition August 1997
+
+
+1. Introduction
+
+ MIME specifies a standard format for encapsulating multiple pieces of
+ data into a single Internet message. That document does not address
+ the issue of presentation styles; it provides a framework for the
+ interchange of message content, but leaves presentation issues solely
+ in the hands of mail user agent (MUA) implementors.
+
+ Two common ways of presenting multipart electronic messages are as a
+ main document with a list of separate attachments, and as a single
+ document with the various parts expanded (displayed) inline. The
+ display of an attachment is generally construed to require positive
+ action on the part of the recipient, while inline message components
+ are displayed automatically when the message is viewed. A mechanism
+ is needed to allow the sender to transmit this sort of presentational
+ information to the recipient; the Content-Disposition header provides
+ this mechanism, allowing each component of a message to be tagged
+ with an indication of its desired presentation semantics.
+
+ Tagging messages in this manner will often be sufficient for basic
+ message formatting. However, in many cases a more powerful and
+ flexible approach will be necessary. The definition of such
+ approaches is beyond the scope of this memo; however, such approaches
+ can benefit from additional Content-Disposition values and
+ parameters, to be defined at a later date.
+
+ In addition to allowing the sender to specify the presentational
+ disposition of a message component, it is desirable to allow her to
+ indicate a default archival disposition; a filename. The optional
+ "filename" parameter provides for this. Further, the creation-date,
+ modification-date, and read-date parameters allow preservation of
+ those file attributes when the file is transmitted over MIME email.
+
+ NB: The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
+ SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
+ document, are to be interpreted as described in [RFC 2119].
+
+2. The Content-Disposition Header Field
+
+ Content-Disposition is an optional header field. In its absence, the
+ MUA may use whatever presentation method it deems suitable.
+
+ It is desirable to keep the set of possible disposition types small
+ and well defined, to avoid needless complexity. Even so, evolving
+ usage will likely require the definition of additional disposition
+ types or parameters, so the set of disposition values is extensible;
+ see below.
+
+
+
+
+Troost, et. al. Standards Track [Page 2]
+
+RFC 2183 Content-Disposition August 1997
+
+
+ In the extended BNF notation of [RFC 822], the Content-Disposition
+ header field is defined as follows:
+
+ disposition := "Content-Disposition" ":"
+ disposition-type
+ *(";" disposition-parm)
+
+ disposition-type := "inline"
+ / "attachment"
+ / extension-token
+ ; values are not case-sensitive
+
+ disposition-parm := filename-parm
+ / creation-date-parm
+ / modification-date-parm
+ / read-date-parm
+ / size-parm
+ / parameter
+
+ filename-parm := "filename" "=" value
+
+ creation-date-parm := "creation-date" "=" quoted-date-time
+
+ modification-date-parm := "modification-date" "=" quoted-date-time
+
+ read-date-parm := "read-date" "=" quoted-date-time
+
+ size-parm := "size" "=" 1*DIGIT
+
+ quoted-date-time := quoted-string
+ ; contents MUST be an RFC 822 `date-time'
+ ; numeric timezones (+HHMM or -HHMM) MUST be used
+
+
+
+ NOTE ON PARAMETER VALUE LENGHTS: A short (length <= 78 characters)
+ parameter value containing only non-`tspecials' characters SHOULD be
+ represented as a single `token'. A short parameter value containing
+ only ASCII characters, but including `tspecials' characters, SHOULD
+ be represented as `quoted-string'. Parameter values longer than 78
+ characters, or which contain non-ASCII characters, MUST be encoded as
+ specified in [RFC 2184].
+
+ `Extension-token', `parameter', `tspecials' and `value' are defined
+ according to [RFC 2045] (which references [RFC 822] in the definition
+ of some of these tokens). `quoted-string' and `DIGIT' are defined in
+ [RFC 822].
+
+
+
+
+Troost, et. al. Standards Track [Page 3]
+
+RFC 2183 Content-Disposition August 1997
+
+
+2.1 The Inline Disposition Type
+
+ A bodypart should be marked `inline' if it is intended to be
+ displayed automatically upon display of the message. Inline
+ bodyparts should be presented in the order in which they occur,
+ subject to the normal semantics of multipart messages.
+
+2.2 The Attachment Disposition Type
+
+ Bodyparts can be designated `attachment' to indicate that they are
+ separate from the main body of the mail message, and that their
+ display should not be automatic, but contingent upon some further
+ action of the user. The MUA might instead present the user of a
+ bitmap terminal with an iconic representation of the attachments, or,
+ on character terminals, with a list of attachments from which the
+ user could select for viewing or storage.
+
+2.3 The Filename Parameter
+
+ The sender may want to suggest a filename to be used if the entity is
+ detached and stored in a separate file. If the receiving MUA writes
+ the entity to a file, the suggested filename should be used as a
+ basis for the actual filename, where possible.
+
+ It is important that the receiving MUA not blindly use the suggested
+ filename. The suggested filename SHOULD be checked (and possibly
+ changed) to see that it conforms to local filesystem conventions,
+ does not overwrite an existing file, and does not present a security
+ problem (see Security Considerations below).
+
+ The receiving MUA SHOULD NOT respect any directory path information
+ that may seem to be present in the filename parameter. The filename
+ should be treated as a terminal component only. Portable
+ specification of directory paths might possibly be done in the future
+ via a separate Content-Disposition parameter, but no provision is
+ made for it in this draft.
+
+ Current [RFC 2045] grammar restricts parameter values (and hence
+ Content-Disposition filenames) to US-ASCII. We recognize the great
+ desirability of allowing arbitrary character sets in filenames, but
+ it is beyond the scope of this document to define the necessary
+ mechanisms. We expect that the basic [RFC 1521] `value'
+ specification will someday be amended to allow use of non-US-ASCII
+ characters, at which time the same mechanism should be used in the
+ Content-Disposition filename parameter.
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 4]
+
+RFC 2183 Content-Disposition August 1997
+
+
+ Beyond the limitation to US-ASCII, the sending MUA may wish to bear
+ in mind the limitations of common filesystems. Many have severe
+ length and character set restrictions. Short alphanumeric filenames
+ are least likely to require modification by the receiving system.
+
+ The presence of the filename parameter does not force an
+ implementation to write the entity to a separate file. It is
+ perfectly acceptable for implementations to leave the entity as part
+ of the normal mail stream unless the user requests otherwise. As a
+ consequence, the parameter may be used on any MIME entity, even
+ `inline' ones. These will not normally be written to files, but the
+ parameter could be used to provide a filename if the receiving user
+ should choose to write the part to a file.
+
+2.4 The Creation-Date parameter
+
+ The creation-date parameter MAY be used to indicate the date at which
+ the file was created. If this parameter is included, the paramter
+ value MUST be a quoted-string which contains a representation of the
+ creation date of the file in [RFC 822] `date-time' format.
+
+ UNIX and POSIX implementors are cautioned that the `st_ctime' file
+ attribute of the `stat' structure is not the creation time of the
+ file; it is thus not appropriate as a source for the creation-date
+ parameter value.
+
+2.5 The Modification-Date parameter
+
+ The modification-date parameter MAY be used to indicate the date at
+ which the file was last modified. If the modification-date parameter
+ is included, the paramter value MUST be a quoted-string which
+ contains a representation of the last modification date of the file
+ in [RFC 822] `date-time' format.
+
+2.6 The Read-Date parameter
+
+ The read-date parameter MAY be used to indicate the date at which the
+ file was last read. If the read-date parameter is included, the
+ parameter value MUST be a quoted-string which contains a
+ representation of the last-read date of the file in [RFC 822] `date-
+ time' format.
+
+2.7 The Size parameter
+
+ The size parameter indicates an approximate size of the file in
+ octets. It can be used, for example, to pre-allocate space before
+ attempting to store the file, or to determine whether enough space
+ exists.
+
+
+
+Troost, et. al. Standards Track [Page 5]
+
+RFC 2183 Content-Disposition August 1997
+
+
+2.8 Future Extensions and Unrecognized Disposition Types
+
+ In the likely event that new parameters or disposition types are
+ needed, they should be registered with the Internet Assigned Numbers
+ Authority (IANA), in the manner specified in Section 9 of this memo.
+
+ Once new disposition types and parameters are defined, there is of
+ course the likelihood that implementations will see disposition types
+ and parameters they do not understand. Furthermore, since x-tokens
+ are allowed, implementations may also see entirely unregistered
+ disposition types and parameters.
+
+ Unrecognized parameters should be ignored. Unrecognized disposition
+ types should be treated as `attachment'. The choice of `attachment'
+ for unrecognized types is made because a sender who goes to the
+ trouble of producing a Content-Disposition header with a new
+ disposition type is more likely aiming for something more elaborate
+ than inline presentation.
+
+ Unless noted otherwise in the definition of a parameter, Content-
+ Disposition parameters are valid for all dispositions. (In contrast
+ to MIME content-type parameters, which are defined on a per-content-
+ type basis.) Thus, for example, the `filename' parameter still means
+ the name of the file to which the part should be written, even if the
+ disposition itself is unrecognized.
+
+2.9 Content-Disposition and Multipart
+
+ If a Content-Disposition header is used on a multipart body part, it
+ applies to the multipart as a whole, not the individual subparts.
+ The disposition types of the subparts do not need to be consulted
+ until the multipart itself is presented. When the multipart is
+ displayed, then the dispositions of the subparts should be respected.
+
+ If the `inline' disposition is used, the multipart should be
+ displayed as normal; however, an `attachment' subpart should require
+ action from the user to display.
+
+ If the `attachment' disposition is used, presentation of the
+ multipart should not proceed without explicit user action. Once the
+ user has chosen to display the multipart, the individual subpart
+ dispositions should be consulted to determine how to present the
+ subparts.
+
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 6]
+
+RFC 2183 Content-Disposition August 1997
+
+
+2.10 Content-Disposition and the Main Message
+
+ It is permissible to use Content-Disposition on the main body of an
+ [RFC 822] message.
+
+3. Examples
+
+ Here is a an example of a body part containing a JPEG image that is
+ intended to be viewed by the user immediately:
+
+ Content-Type: image/jpeg
+ Content-Disposition: inline
+ Content-Description: just a small picture of me
+
+ <jpeg data>
+
+ The following body part contains a JPEG image that should be
+ displayed to the user only if the user requests it. If the JPEG is
+ written to a file, the file should be named "genome.jpg". The
+ recipient's user might also choose to set the last-modified date of
+ the stored file to date in the modification-date parameter:
+
+ Content-Type: image/jpeg
+ Content-Disposition: attachment; filename=genome.jpeg;
+ modification-date="Wed, 12 Feb 1997 16:29:51 -0500";
+ Content-Description: a complete map of the human genome
+
+ <jpeg data>
+
+ The following is an example of the use of the `attachment'
+ disposition with a multipart body part. The user should see text-
+ part-1 immediately, then take some action to view multipart-2. After
+ taking action to view multipart-2, the user will see text-part-2
+ right away, and be required to take action to view jpeg-1. Subparts
+ are indented for clarity; they would not be so indented in a real
+ message.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 7]
+
+RFC 2183 Content-Disposition August 1997
+
+
+ Content-Type: multipart/mixed; boundary=outer
+ Content-Description: multipart-1
+
+ --outer
+ Content-Type: text/plain
+ Content-Disposition: inline
+ Content-Description: text-part-1
+
+ Some text goes here
+
+ --outer
+ Content-Type: multipart/mixed; boundary=inner
+ Content-Disposition: attachment
+ Content-Description: multipart-2
+
+ --inner
+ Content-Type: text/plain
+ Content-Disposition: inline
+ Content-Description: text-part-2
+
+ Some more text here.
+
+ --inner
+ Content-Type: image/jpeg
+ Content-Disposition: attachment
+ Content-Description: jpeg-1
+
+ <jpeg data>
+ --inner--
+ --outer--
+
+4. Summary
+
+ Content-Disposition takes one of two values, `inline' and
+ `attachment'. `Inline' indicates that the entity should be
+ immediately displayed to the user, whereas `attachment' means that
+ the user should take additional action to view the entity.
+
+ The `filename' parameter can be used to suggest a filename for
+ storing the bodypart, if the user wishes to store it in an external
+ file.
+
+
+
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 8]
+
+RFC 2183 Content-Disposition August 1997
+
+
+5. Security Considerations
+
+ There are security issues involved any time users exchange data.
+ While these are not to be minimized, neither does this memo change
+ the status quo in that regard, except in one instance.
+
+ Since this memo provides a way for the sender to suggest a filename,
+ a receiving MUA must take care that the sender's suggested filename
+ does not represent a hazard. Using UNIX as an example, some hazards
+ would be:
+
+ + Creating startup files (e.g., ".login").
+
+ + Creating or overwriting system files (e.g., "/etc/passwd").
+
+ + Overwriting any existing file.
+
+ + Placing executable files into any command search path
+ (e.g., "~/bin/more").
+
+ + Sending the file to a pipe (e.g., "| sh").
+
+ In general, the receiving MUA should not name or place the file such
+ that it will get interpreted or executed without the user explicitly
+ initiating the action.
+
+ It is very important to note that this is not an exhaustive list; it
+ is intended as a small set of examples only. Implementors must be
+ alert to the potential hazards on their target systems.
+
+6. References
+
+ [RFC 2119]
+ Bradner, S., "Key words for use in RFCs to Indicate Requirement
+ Levels", RFC 2119, March 1997.
+
+ [RFC 2184]
+ Freed, N. and K. Moore, "MIME Parameter value and Encoded Words:
+ Character Sets, Lanaguage, and Continuations", RFC 2184, August
+ 1997.
+
+ [RFC 2045]
+ Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
+ Extensions) Part One: Format of Internet Message Bodies", RFC
+ 2045, December 1996.
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 9]
+
+RFC 2183 Content-Disposition August 1997
+
+
+ [RFC 2046]
+ Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
+ Extensions) Part Two: Media Types", RFC 2046, December 1996.
+
+ [RFC 2047]
+ Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
+ Three: Message Header Extensions for non-ASCII Text", RFC 2047,
+ December 1996.
+
+ [RFC 2048]
+ Freed, N., Klensin, J. and J. Postel, "MIME (Multipurpose
+ Internet Mail Extensions) Part Four: Registration Procedures",
+ RFC 2048, December 1996.
+
+ [RFC 2049]
+ Freed, N. and N. Borenstein, "MIME (Multipurpose Internet Mail
+ Extensions) Part Five: Conformance Criteria and Examples", RFC
+ 2049, December 1996.
+
+ [RFC 822]
+ Crocker, D., "Standard for the Format of ARPA Internet Text
+ Messages", STD 11, RFC 822, UDEL, August 1982.
+
+7. Acknowledgements
+
+ We gratefully acknowledge the help these people provided during the
+ preparation of this draft:
+
+ Nathaniel Borenstein
+ Ned Freed
+ Keith Moore
+ Dave Crocker
+ Dan Pritchett
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 10]
+
+RFC 2183 Content-Disposition August 1997
+
+
+8. Authors' Addresses
+
+ You should blame the editor of this version of the document for any
+ changes since RFC 1806:
+
+ Keith Moore
+ Department of Computer Science
+ University of Tennessee, Knoxville
+ 107 Ayres Hall
+ Knoxville TN 37996-1301
+ USA
+
+ Phone: +1 (423) 974-5067
+ Fax: +1 (423) 974-8296
+ Email: moore@cs.utk.edu
+
+
+ The authors of RFC 1806 are:
+
+ Rens Troost
+ New Century Systems
+ 324 East 41st Street #804
+ New York, NY, 10017 USA
+
+ Phone: +1 (212) 557-2050
+ Fax: +1 (212) 557-2049
+ EMail: rens@century.com
+
+
+ Steve Dorner
+ QUALCOMM Incorporated
+ 6455 Lusk Boulevard
+ San Diego, CA 92121
+ USA
+
+ EMail: sdorner@qualcomm.com
+
+
+9. Registration of New Content-Disposition Values and Parameters
+
+ New Content-Disposition values (besides "inline" and "attachment")
+ may be defined only by Internet standards-track documents, or in
+ Experimental documents approved by the Internet Engineering Steering
+ Group.
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 11]
+
+RFC 2183 Content-Disposition August 1997
+
+
+ New content-disposition parameters may be registered by supplying the
+ information in the following template and sending it via electronic
+ mail to IANA@IANA.ORG:
+
+ To: IANA@IANA.ORG
+ Subject: Registration of new Content-Disposition parameter
+
+ Content-Disposition parameter name:
+
+ Allowable values for this parameter:
+ (If the parameter can only assume a small number of values,
+ list each of those values. Otherwise, describe the values
+ that the parameter can assume.)
+ Description:
+ (What is the purpose of this parameter and how is it used?)
+
+10. Changes since RFC 1806
+
+ The following changes have been made since the earlier version of
+ this document, published in RFC 1806 as an Experimental protocol:
+
+ + Updated references to MIME documents. In some cases this
+ involved substituting a reference to one of the current MIME
+ RFCs for a reference to RFC 1521; in other cases, a reference to
+ RFC 1521 was simply replaced with the word "MIME".
+
+ + Added a section on registration procedures, since none of the
+ procedures in RFC 2048 seemed to be appropriate.
+
+ + Added new parameter types: creation-date, modification-date,
+ read-date, and size.
+
+
+ + Incorporated a reference to draft-freed-pvcsc-* for encoding
+ long or non-ASCII parameter values.
+
+ + Added reference to RFC 2119 to define MUST, SHOULD, etc.
+ keywords.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Troost, et. al. Standards Track [Page 12]
+
diff --git a/rfc/rfc2231.txt b/rfc/rfc2231.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group N. Freed
+Request for Comments: 2231 Innosoft
+Updates: 2045, 2047, 2183 K. Moore
+Obsoletes: 2184 University of Tennessee
+Category: Standards Track November 1997
+
+
+ MIME Parameter Value and Encoded Word Extensions:
+ Character Sets, Languages, and Continuations
+
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1997). All Rights Reserved.
+
+1. Abstract
+
+ This memo defines extensions to the RFC 2045 media type and RFC 2183
+ disposition parameter value mechanisms to provide
+
+ (1) a means to specify parameter values in character sets
+ other than US-ASCII,
+
+ (2) to specify the language to be used should the value be
+ displayed, and
+
+ (3) a continuation mechanism for long parameter values to
+ avoid problems with header line wrapping.
+
+ This memo also defines an extension to the encoded words defined in
+ RFC 2047 to allow the specification of the language to be used for
+ display as well as the character set.
+
+2. Introduction
+
+ The Multipurpose Internet Mail Extensions, or MIME [RFC-2045, RFC-
+ 2046, RFC-2047, RFC-2048, RFC-2049], define a message format that
+ allows for:
+
+
+
+
+
+Freed & Moore Standards Track [Page 1]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ (1) textual message bodies in character sets other than
+ US-ASCII,
+
+ (2) non-textual message bodies,
+
+ (3) multi-part message bodies, and
+
+ (4) textual header information in character sets other than
+ US-ASCII.
+
+ MIME is now widely deployed and is used by a variety of Internet
+ protocols, including, of course, Internet email. However, MIME's
+ success has resulted in the need for additional mechanisms that were
+ not provided in the original protocol specification.
+
+ In particular, existing MIME mechanisms provide for named media type
+ (content-type field) parameters as well as named disposition
+ (content-disposition field). A MIME media type may specify any
+ number of parameters associated with all of its subtypes, and any
+ specific subtype may specify additional parameters for its own use. A
+ MIME disposition value may specify any number of associated
+ parameters, the most important of which is probably the attachment
+ disposition's filename parameter.
+
+ These parameter names and values end up appearing in the content-type
+ and content-disposition header fields in Internet email. This
+ inherently imposes three crucial limitations:
+
+ (1) Lines in Internet email header fields are folded
+ according to RFC 822 folding rules. This makes long
+ parameter values problematic.
+
+ (2) MIME headers, like the RFC 822 headers they often
+ appear in, are limited to 7bit US-ASCII, and the
+ encoded-word mechanisms of RFC 2047 are not available
+ to parameter values. This makes it impossible to have
+ parameter values in character sets other than US-ASCII
+ without specifying some sort of private per-parameter
+ encoding.
+
+ (3) It has recently become clear that character set
+ information is not sufficient to properly display some
+ sorts of information -- language information is also
+ needed [RFC-2130]. For example, support for
+ handicapped users may require reading text string
+
+
+
+
+
+
+Freed & Moore Standards Track [Page 2]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ aloud. The language the text is written in is needed
+ for this to be done correctly. Some parameter values
+ may need to be displayed, hence there is a need to
+ allow for the inclusion of language information.
+
+ The last problem on this list is also an issue for the encoded words
+ defined by RFC 2047, as encoded words are intended primarily for
+ display purposes.
+
+ This document defines extensions that address all of these
+ limitations. All of these extensions are implemented in a fashion
+ that is completely compatible at a syntactic level with existing MIME
+ implementations. In addition, the extensions are designed to have as
+ little impact as possible on existing uses of MIME.
+
+ IMPORTANT NOTE: These mechanisms end up being somewhat gibbous when
+ they actually are used. As such, these mechanisms should not be used
+ lightly; they should be reserved for situations where a real need for
+ them exists.
+
+2.1. Requirements notation
+
+ This document occasionally uses terms that appear in capital letters.
+ When the terms "MUST", "SHOULD", "MUST NOT", "SHOULD NOT", and "MAY"
+ appear capitalized, they are being used to indicate particular
+ requirements of this specification. A discussion of the meanings of
+ these terms appears in [RFC- 2119].
+
+3. Parameter Value Continuations
+
+ Long MIME media type or disposition parameter values do not interact
+ well with header line wrapping conventions. In particular, proper
+ header line wrapping depends on there being places where linear
+ whitespace (LWSP) is allowed, which may or may not be present in a
+ parameter value, and even if present may not be recognizable as such
+ since specific knowledge of parameter value syntax may not be
+ available to the agent doing the line wrapping. The result is that
+ long parameter values may end up getting truncated or otherwise
+ damaged by incorrect line wrapping implementations.
+
+ A mechanism is therefore needed to break up parameter values into
+ smaller units that are amenable to line wrapping. Any such mechanism
+ MUST be compatible with existing MIME processors. This means that
+
+ (1) the mechanism MUST NOT change the syntax of MIME media
+ type and disposition lines, and
+
+
+
+
+
+Freed & Moore Standards Track [Page 3]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ (2) the mechanism MUST NOT depend on parameter ordering
+ since MIME states that parameters are not order
+ sensitive. Note that while MIME does prohibit
+ modification of MIME headers during transport, it is
+ still possible that parameters will be reordered when
+ user agent level processing is done.
+
+ The obvious solution, then, is to use multiple parameters to contain
+ a single parameter value and to use some kind of distinguished name
+ to indicate when this is being done. And this obvious solution is
+ exactly what is specified here: The asterisk character ("*") followed
+ by a decimal count is employed to indicate that multiple parameters
+ are being used to encapsulate a single parameter value. The count
+ starts at 0 and increments by 1 for each subsequent section of the
+ parameter value. Decimal values are used and neither leading zeroes
+ nor gaps in the sequence are allowed.
+
+ The original parameter value is recovered by concatenating the
+ various sections of the parameter, in order. For example, the
+ content-type field
+
+ Content-Type: message/external-body; access-type=URL;
+ URL*0="ftp://";
+ URL*1="cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"
+
+ is semantically identical to
+
+ Content-Type: message/external-body; access-type=URL;
+ URL="ftp://cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"
+
+ Note that quotes around parameter values are part of the value
+ syntax; they are NOT part of the value itself. Furthermore, it is
+ explicitly permitted to have a mixture of quoted and unquoted
+ continuation fields.
+
+4. Parameter Value Character Set and Language Information
+
+ Some parameter values may need to be qualified with character set or
+ language information. It is clear that a distinguished parameter
+ name is needed to identify when this information is present along
+ with a specific syntax for the information in the value itself. In
+ addition, a lightweight encoding mechanism is needed to accommodate 8
+ bit information in parameter values.
+
+
+
+
+
+
+
+
+Freed & Moore Standards Track [Page 4]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ Asterisks ("*") are reused to provide the indicator that language and
+ character set information is present and encoding is being used. A
+ single quote ("'") is used to delimit the character set and language
+ information at the beginning of the parameter value. Percent signs
+ ("%") are used as the encoding flag, which agrees with RFC 2047.
+
+ Specifically, an asterisk at the end of a parameter name acts as an
+ indicator that character set and language information may appear at
+ the beginning of the parameter value. A single quote is used to
+ separate the character set, language, and actual value information in
+ the parameter value string, and an percent sign is used to flag
+ octets encoded in hexadecimal. For example:
+
+ Content-Type: application/x-stuff;
+ title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A
+
+ Note that it is perfectly permissible to leave either the character
+ set or language field blank. Note also that the single quote
+ delimiters MUST be present even when one of the field values is
+ omitted. This is done when either character set, language, or both
+ are not relevant to the parameter value at hand. This MUST NOT be
+ done in order to indicate a default character set or language --
+ parameter field definitions MUST NOT assign a default character set
+ or language.
+
+4.1. Combining Character Set, Language, and Parameter Continuations
+
+ Character set and language information may be combined with the
+ parameter continuation mechanism. For example:
+
+ Content-Type: application/x-stuff
+ title*0*=us-ascii'en'This%20is%20even%20more%20
+ title*1*=%2A%2A%2Afun%2A%2A%2A%20
+ title*2="isn't it!"
+
+ Note that:
+
+ (1) Language and character set information only appear at
+ the beginning of a given parameter value.
+
+ (2) Continuations do not provide a facility for using more
+ than one character set or language in the same
+ parameter value.
+
+ (3) A value presented using multiple continuations may
+ contain a mixture of encoded and unencoded segments.
+
+
+
+
+
+Freed & Moore Standards Track [Page 5]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ (4) The first segment of a continuation MUST be encoded if
+ language and character set information are given.
+
+ (5) If the first segment of a continued parameter value is
+ encoded the language and character set field delimiters
+ MUST be present even when the fields are left blank.
+
+5. Language specification in Encoded Words
+
+ RFC 2047 provides support for non-US-ASCII character sets in RFC 822
+ message header comments, phrases, and any unstructured text field.
+ This is done by defining an encoded word construct which can appear
+ in any of these places. Given that these are fields intended for
+ display, it is sometimes necessary to associate language information
+ with encoded words as well as just the character set. This
+ specification extends the definition of an encoded word to allow the
+ inclusion of such information. This is simply done by suffixing the
+ character set specification with an asterisk followed by the language
+ tag. For example:
+
+ From: =?US-ASCII*EN?Q?Keith_Moore?= <moore@cs.utk.edu>
+
+6. IMAP4 Handling of Parameter Values
+
+ IMAP4 [RFC-2060] servers SHOULD decode parameter value continuations
+ when generating the BODY and BODYSTRUCTURE fetch attributes.
+
+7. Modifications to MIME ABNF
+
+ The ABNF for MIME parameter values given in RFC 2045 is:
+
+ parameter := attribute "=" value
+
+ attribute := token
+ ; Matching of attributes
+ ; is ALWAYS case-insensitive.
+
+ This specification changes this ABNF to:
+
+ parameter := regular-parameter / extended-parameter
+
+ regular-parameter := regular-parameter-name "=" value
+
+ regular-parameter-name := attribute [section]
+
+ attribute := 1*attribute-char
+
+
+
+
+
+Freed & Moore Standards Track [Page 6]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ attribute-char := <any (US-ASCII) CHAR except SPACE, CTLs,
+ "*", "'", "%", or tspecials>
+
+ section := initial-section / other-sections
+
+ initial-section := "*0"
+
+ other-sections := "*" ("1" / "2" / "3" / "4" / "5" /
+ "6" / "7" / "8" / "9") *DIGIT)
+
+ extended-parameter := (extended-initial-name "="
+ extended-value) /
+ (extended-other-names "="
+ extended-other-values)
+
+ extended-initial-name := attribute [initial-section] "*"
+
+ extended-other-names := attribute other-sections "*"
+
+ extended-initial-value := [charset] "'" [language] "'"
+ extended-other-values
+
+ extended-other-values := *(ext-octet / attribute-char)
+
+ ext-octet := "%" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")
+
+ charset := <registered character set name>
+
+ language := <registered language tag [RFC-1766]>
+
+ The ABNF given in RFC 2047 for encoded-words is:
+
+ encoded-word := "=?" charset "?" encoding "?" encoded-text "?="
+
+ This specification changes this ABNF to:
+
+ encoded-word := "=?" charset ["*" language] "?" encoded-text "?="
+
+8. Character sets which allow specification of language
+
+ In the future it is likely that some character sets will provide
+ facilities for inline language labeling. Such facilities are
+ inherently more flexible than those defined here as they allow for
+ language switching in the middle of a string.
+
+
+
+
+
+
+
+Freed & Moore Standards Track [Page 7]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ If and when such facilities are developed they SHOULD be used in
+ preference to the language labeling facilities specified here. Note
+ that all the mechanisms defined here allow for the omission of
+ language labels so as to be able to accommodate this possible future
+ usage.
+
+9. Security Considerations
+
+ This RFC does not discuss security issues and is not believed to
+ raise any security issues not already endemic in electronic mail and
+ present in fully conforming implementations of MIME.
+
+10. References
+
+ [RFC-822]
+ Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822 August 1982.
+
+ [RFC-1766]
+ Alvestrand, H., "Tags for the Identification of
+ Languages", RFC 1766, March 1995.
+
+ [RFC-2045]
+ Freed, N., and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, December 1996.
+
+ [RFC-2046]
+ Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Two: Media Types", RFC 2046,
+ December 1996.
+
+ [RFC-2047]
+ Moore, K., "Multipurpose Internet Mail Extensions (MIME)
+ Part Three: Representation of Non-ASCII Text in Internet
+ Message Headers", RFC 2047, December 1996.
+
+ [RFC-2048]
+ Freed, N., Klensin, J. and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) Part Four: MIME
+ Registration Procedures", RFC 2048, December 1996.
+
+ [RFC-2049]
+ Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Five: Conformance Criteria and
+ Examples", RFC 2049, December 1996.
+
+
+
+
+
+Freed & Moore Standards Track [Page 8]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+ [RFC-2060]
+ Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+ [RFC-2119]
+ Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, March 1997.
+
+ [RFC-2130]
+ Weider, C., Preston, C., Simonsen, K., Alvestrand, H.,
+ Atkinson, R., Crispin, M., and P. Svanberg, "Report from the
+ IAB Character Set Workshop", RFC 2130, April 1997.
+
+ [RFC-2183]
+ Troost, R., Dorner, S. and K. Moore, "Communicating
+ Presentation Information in Internet Messages: The
+ Content-Disposition Header", RFC 2183, August 1997.
+
+11. Authors' Addresses
+
+ Ned Freed
+ Innosoft International, Inc.
+ 1050 Lakes Drive
+ West Covina, CA 91790
+ USA
+
+ Phone: +1 626 919 3600
+ Fax: +1 626 919 3614
+ EMail: ned.freed@innosoft.com
+
+
+ Keith Moore
+ Computer Science Dept.
+ University of Tennessee
+ 107 Ayres Hall
+ Knoxville, TN 37996-1301
+ USA
+
+ EMail: moore@cs.utk.edu
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Moore Standards Track [Page 9]
+
+RFC 2231 MIME Value and Encoded Word Extensions November 1997
+
+
+12. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1997). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Freed & Moore Standards Track [Page 10]
+
diff --git a/rfc/rfc2387.txt b/rfc/rfc2387.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group E. Levinson
+Request for Comments: 2387 August 1998
+Obsoletes: 2112
+Category: Standards Track
+
+
+ The MIME Multipart/Related Content-type
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+Abstract
+
+ The Multipart/Related content-type provides a common mechanism for
+ representing objects that are aggregates of related MIME body parts.
+ This document defines the Multipart/Related content-type and provides
+ examples of its use.
+
+1. Introduction
+
+ Several applications of MIME, including MIME-PEM, and MIME-Macintosh
+ and other proposals, require multiple body parts that make sense only
+ in the aggregate. The present approach to these compound objects has
+ been to define specific multipart subtypes for each new object. In
+ keeping with the MIME philosophy of having one mechanism to achieve
+ the same goal for different purposes, this document describes a
+ single mechanism for such aggregate or compound objects.
+
+ The Multipart/Related content-type addresses the MIME representation
+ of compound objects. The object is categorized by a "type"
+ parameter. Additional parameters are provided to indicate a specific
+ starting body part or root and auxiliary information which may be
+ required when unpacking or processing the object.
+
+ Multipart/Related MIME entities may contain Content-Disposition
+ headers that provide suggestions for the storage and display of a
+ body part. Multipart/Related processing takes precedence over
+ Content-Disposition; the interaction between them is discussed in
+ section 4.
+
+
+
+Levinson Standards Track [Page 1]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ Responsibility for the display or processing of a Multipart/Related's
+ constituent entities rests with the application that handles the
+ compound object.
+
+2. Multipart/Related Registration Information
+
+ The following form is copied from RFC 1590, Appendix A.
+
+ To: IANA@isi.edu
+ Subject: Registration of new Media Type content-type/subtype
+
+ Media Type name: Multipart
+
+ Media subtype name: Related
+
+ Required parameters: Type, a media type/subtype.
+
+ Optional parameters: Start
+ Start-info
+
+ Encoding considerations: Multipart content-types cannot have
+ encodings.
+
+ Security considerations: Depends solely on the referenced type.
+
+ Published specification: RFC-REL (this document).
+
+ Person & email address to contact for further information:
+ Edward Levinson
+ 47 Clive Street
+ Metuchen, NJ 08840-1060
+ +1 908 494 1606
+ XIson@cnj.digex.net
+
+3. Intended usage
+
+ The Multipart/Related media type is intended for compound objects
+ consisting of several inter-related body parts. For a
+ Multipart/Related object, proper display cannot be achieved by
+ individually displaying the constituent body parts. The content-type
+ of the Multipart/Related object is specified by the type parameter.
+ The "start" parameter, if given, points, via a content-ID, to the
+ body part that contains the object root. The default root is the
+ first body part within the Multipart/Related body.
+
+ The relationships among the body parts of a compound object
+ distinguishes it from other object types. These relationships are
+ often represented by links internal to the object's components that
+
+
+
+Levinson Standards Track [Page 2]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ reference the other components. Within a single operating
+ environment the links are often file names, such links may be
+ represented within a MIME message using content-IDs or the value of
+ some other "Content-" headers.
+
+3.1. The Type Parameter
+
+ The type parameter must be specified and its value is the MIME media
+ type of the "root" body part. It permits a MIME user agent to
+ determine the content-type without reference to the enclosed body
+ part. If the value of the type parameter and the root body part's
+ content-type differ then the User Agent's behavior is undefined.
+
+3.2. The Start Parameter
+
+ The start parameter, if given, is the content-ID of the compound
+ object's "root". If not present the "root" is the first body part in
+ the Multipart/Related entity. The "root" is the element the
+ applications processes first.
+
+3.3. The Start-Info Parameter
+
+ Additional information can be provided to an application by the
+ start-info parameter. It contains either a string or points, via a
+ content-ID, to another MIME entity in the message. A typical use
+ might be to provide additional command line parameters or a MIME
+ entity giving auxiliary information for processing the compound
+ object.
+
+ Applications that use Multipart/Related must specify the
+ interpretation of start-info. User Agents shall provide the
+ parameter's value to the processing application. Processes can
+ distinguish a start-info reference from a token or quoted-string by
+ examining the first non-white-space character, "<" indicates a
+ reference.
+
+3.4. Syntax
+
+ related-param := [ ";" "start" "=" cid ]
+ [ ";" "start-info" "="
+ ( cid-list / value ) ]
+ [ ";" "type" "=" type "/" subtype ]
+ ; order independent
+
+ cid-list := cid cid-list
+
+ cid := msg-id ; c.f. [822]
+
+
+
+
+Levinson Standards Track [Page 3]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ value := token / quoted-string ; c.f. [MIME]
+ ; value cannot begin with "<"
+
+ Note that the parameter values will usually require quoting. Msg-id
+ contains the special characters "<", ">", "@", and perhaps other
+ special characters. If msg-id contains quoted-strings, those quote
+ marks must be escaped. Similarly, the type parameter contains the
+ special character "/".
+
+4. Handling Content-Disposition Headers
+
+ Content-Disposition Headers [DISP] suggest presentation styles for
+ MIME body parts. [DISP] describes two presentation styles, called
+ the disposition type, INLINE and ATTACHMENT. These, used within a
+ multipart entity, allow the sender to suggest presentation
+ information. [DISP] also provides for an optional storage (file)
+ name. Content-Disposition headers could appear in one or more body
+ parts contained within a Multipart/Related entity.
+
+ Using Content-Disposition headers in addition to Multipart/Related
+ provides presentation information to User Agents that do not
+ recognize Multipart/Related. They will treat the multipart as
+ Multipart/Mixed and they may find the Content-Disposition information
+ useful.
+
+ With Multipart/Related however, the application processing the
+ compound object determines the presentation style for all the
+ contained parts. In that context the Content-Disposition header
+ information is redundant or even misleading. Hence, User Agents that
+ understand Multipart/Related shall ignore the disposition type within
+ a Multipart/Related body part.
+
+ It may be possible for a User Agent capable of handling both
+ Multipart/Related and Content-Disposition headers to provide the
+ invoked application the Content-Disposition header's optional
+ filename parameter to the Multipart/Related. The use of that
+ information will depend on the specific application and should be
+ specified when describing the handling of the corresponding compound
+ object. Such descriptions would be appropriate in an RFC registering
+ that object's media type.
+
+5. Examples
+
+5.1 Application/X-FixedRecord
+
+ The X-FixedRecord content-type consists of one or more octet-streams
+ and a list of the lengths of each record. The root, which lists the
+ record lengths of each record within the streams. The record length
+
+
+
+Levinson Standards Track [Page 4]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ list, type Application/X-FixedRecord, consists of a set of INTEGERs
+ in ASCII format, one per line. Each INTEGER gives the number of
+ octets from the octet-stream body part that constitute the next
+ "record".
+
+ The example below, uses a single data block.
+
+ Content-Type: Multipart/Related; boundary=example-1
+ start="<950120.aaCC@XIson.com>";
+ type="Application/X-FixedRecord"
+ start-info="-o ps"
+
+ --example-1
+ Content-Type: Application/X-FixedRecord
+ Content-ID: <950120.aaCC@XIson.com>
+
+ 25
+ 10
+ 34
+ 10
+ 25
+ 21
+ 26
+ 10
+ --example-1
+ Content-Type: Application/octet-stream
+ Content-Description: The fixed length records
+ Content-Transfer-Encoding: base64
+ Content-ID: <950120.aaCB@XIson.com>
+
+ T2xkIE1hY0RvbmFsZCBoYWQgYSBmYXJtCkUgSS
+ BFIEkgTwpBbmQgb24gaGlzIGZhcm0gaGUgaGFk
+ IHNvbWUgZHVja3MKRSBJIEUgSSBPCldpdGggYS
+ BxdWFjayBxdWFjayBoZXJlLAphIHF1YWNrIHF1
+ YWNrIHRoZXJlLApldmVyeSB3aGVyZSBhIHF1YW
+ NrIHF1YWNrCkUgSSBFIEkgTwo=
+
+ --example-1--
+
+
+
+
+
+
+
+
+
+
+
+
+
+Levinson Standards Track [Page 5]
+
+RFC 2387 Multipart/Related August 1998
+
+
+5.2 Text/X-Okie
+
+ The Text/X-Okie is an invented markup language permitting the
+ inclusion of images with text. A feature of this example is the
+ inclusion of two additional body parts, both picture. They are
+ referred to internally by the encapsulated document via each
+ picture's body part content-ID. Usage of "cid:", as in this example,
+ may be useful for a variety of compound objects. It is not, however,
+ a part of the Multipart/Related specification.
+
+ Content-Type: Multipart/Related; boundary=example-2;
+ start="<950118.AEBH@XIson.com>"
+ type="Text/x-Okie"
+
+ --example-2
+ Content-Type: Text/x-Okie; charset=iso-8859-1;
+ declaration="<950118.AEB0@XIson.com>"
+ Content-ID: <950118.AEBH@XIson.com>
+ Content-Description: Document
+
+ {doc}
+ This picture was taken by an automatic camera mounted ...
+ {image file=cid:950118.AECB@XIson.com}
+ {para}
+ Now this is an enlargement of the area ...
+ {image file=cid:950118:AFDH@XIson.com}
+ {/doc}
+ --example-2
+ Content-Type: image/jpeg
+ Content-ID: <950118.AFDH@XIson.com>
+ Content-Transfer-Encoding: BASE64
+ Content-Description: Picture A
+
+ [encoded jpeg image]
+ --example-2
+ Content-Type: image/jpeg
+ Content-ID: <950118.AECB@XIson.com>
+ Content-Transfer-Encoding: BASE64
+ Content-Description: Picture B
+
+ [encoded jpeg image]
+ --example-2--
+
+5.3 Content-Disposition
+
+ In the above example each image body part could also have a Content-
+ Disposition header. For example,
+
+
+
+
+Levinson Standards Track [Page 6]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ --example-2
+ Content-Type: image/jpeg
+ Content-ID: <950118.AECB@XIson.com>
+ Content-Transfer-Encoding: BASE64
+ Content-Description: Picture B
+ Content-Disposition: INLINE
+
+ [encoded jpeg image]
+ --example-2--
+
+ User Agents that recognize Multipart/Related will ignore the
+ Content-Disposition header's disposition type. Other User Agents
+ will process the Multipart/Related as Multipart/Mixed and may make
+ use of that header's information.
+
+6. User Agent Requirements
+
+ User agents that do not recognize Multipart/Related shall, in
+ accordance with [MIME], treat the entire entity as Multipart/Mixed.
+ MIME User Agents that do recognize Multipart/Related entities but are
+ unable to process the given type should give the user the option of
+ suppressing the entire Multipart/Related body part shall be.
+
+ Existing MIME-capable mail user agents (MUAs) handle the existing
+ media types in a straightforward manner. For discrete media types
+ (e.g. text, image, etc.) the body of the entity can be directly
+ passed to a display process. Similarly the existing composite
+ subtypes can be reduced to handing one or more discrete types.
+ Handling Multipart/Related differs in that processing cannot be
+ reduced to handling the individual entities.
+
+ The following sections discuss what information the processing
+ application requires.
+
+ It is possible that an application specific "receiving agent" will
+ manipulate the entities for display prior to invoking actual
+ application process. Okie, above, is an example of this; it may need
+ a receiving agent to parse the document and substitute local file
+ names for the originator's file names. Other applications may just
+ require a table showing the correspondence between the local file
+ names and the originator's. The receiving agent takes responsibility
+ for such processing.
+
+6.1 Data Requirements
+
+ MIME-capable mail user agents (MUAs) are required to provide the
+ application:
+
+
+
+
+Levinson Standards Track [Page 7]
+
+RFC 2387 Multipart/Related August 1998
+
+
+ (a) the bodies of the MIME entities and the entity Content-* headers,
+
+ (b) the parameters of the Multipart/Related Content-type header, and
+
+ (c) the correspondence between each body's local file name, that
+ body's header data, and, if present, the body part's content-ID.
+
+6.2 Storing Multipart/Related Entities
+
+ The Multipart/Related media type will be used for objects that have
+ internal linkages between the body parts. When the objects are
+ stored the linkages may require processing by the application or its
+ receiving agent.
+
+6.3 Recursion
+
+ MIME is a recursive structure. Hence one must expect a
+ Multipart/Related entity to contain other Multipart/Related entities.
+ When a Multipart/Related entity is being processed for display or
+ storage, any enclosed Multipart/Related entities shall be processed
+ as though they were being stored.
+
+6.4 Configuration Considerations
+
+ It is suggested that MUAs that use configuration mechanisms, see
+ [CFG] for an example, refer to Multipart/Related as Multi-
+ part/Related/<type>, were <type> is the value of the "type"
+ parameter.
+
+7. Security Considerations
+
+ Security considerations relevant to Multipart/Related are identical
+ to those of the underlying content-type.
+
+8. Acknowledgments
+
+ This proposal is the result of conversations the author has had with
+ many people. In particular, Harald A. Alvestrand, James Clark,
+ Charles Goldfarb, Gary Houston, Ned Freed, Ray Moody, and Don
+ Stinchfield, provided both encouragement and invaluable help. The
+ author, however, take full responsibility for all errors contained in
+ this document.
+
+
+
+
+
+
+
+
+
+Levinson Standards Track [Page 8]
+
+RFC 2387 Multipart/Related August 1998
+
+
+9. References
+
+ [822] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822, August 1982.
+
+ [CID] Levinson, E., and J. Clark, "Message/External-Body
+ Content-ID Access Type", RFC 1873, December 1995,
+ Levinson, E., "Message/External-Body Content-ID Access
+ Type", Work in Progress.
+
+ [CFG] Borenstein, N., "A User Agent Configuration Mechanism For
+ Multimedia Mail Format Information", RFC 1524, September
+ 1993.
+
+ [DISP] Troost, R., and S. Dorner, "Communicating Presentation
+ Information in Internet Messages: The Content-
+ Disposition Header", RFC 1806, June 1995.
+
+ [MIME] Borenstein, N., and Freed, N., "Multipurpose Internet
+ Mail Extensions (MIME) Part One: Format of Internet
+ Message Bodies", RFC 2045, November 1996.
+
+9. Author's Address
+
+ Edward Levinson
+ 47 Clive Street
+ Metuchen, NJ 08840-1060
+ USA
+
+ Phone: +1 908 494 1606
+ EMail: XIson@cnj.digex.com
+
+10. Changes from previous draft (RFC 2112)
+
+ Corrected cid urls to conform to RFC 2111; the angle brackets were
+ removed.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Levinson Standards Track [Page 9]
+
+RFC 2387 Multipart/Related August 1998
+
+
+11. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Levinson Standards Track [Page 10]
+
diff --git a/rfc/rfc2425.txt b/rfc/rfc2425.txt
@@ -0,0 +1,1851 @@
+
+
+
+
+
+
+Network Working Group T. Howes
+Request for Comments: 2425 M. Smith
+Category: Standards Track Netscape Communications Corp.
+ F. Dawson
+ Lotus Development Corporation
+ September 1998
+
+
+ A MIME Content-Type for Directory Information
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+1. Abstract
+
+ This document defines a MIME Content-Type for holding directory
+ information. The definition is independent of any particular
+ directory service or protocol. The text/directory Content-Type is
+ defined for holding a variety of directory information, for example,
+ name, or email address, or logo. The text/directory Content-Type can
+ also be used as the root body part in a multipart/related Content-
+ Type for handling more complicated situations, especially those in
+ which non-textual information that already has a natural MIME
+ representation, for example, a photograph or sound, is to be
+ represented.
+
+ The text/directory Content-Type defines a general framework and
+ format for holding directory information in a simple "type:value"
+ form. We refer to "type" in this context meaning a property or
+ attribute with which the value is associated. Mechanisms are defined
+ to specify alternate languages, encodings and other meta-information.
+ This document also defines the procedure by which particular formats,
+ called profiles, for carrying application-specific information within
+ a text/directory Content-Type can be defined and registered, and the
+ conventions such formats must follow. It is expected that other
+ documents will be produced that define such formats for various
+ applications (e.g., white pages).
+
+
+
+
+
+Howes, et. al. Standards Track [Page 1]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+2. Table of Contents
+
+ Status of the Memo................................................ 1
+ Copyright Notice.................................................. 1
+ 1. Abstract...................................................... 1
+ 2. Table of Contents............................................. 2
+ 3. Need for a MIME Directory Type................................ 3
+ 4. Overview...................................................... 4
+ 5. The text/directory Content-Type............................... 4
+ 5.1. MIME media type name........................................ 4
+ 5.2. MIME subtype name........................................... 5
+ 5.3. Required parameters......................................... 5
+ 5.4. Optional parameters......................................... 5
+ 5.5. Encoding considerations..................................... 5
+ 5.6. Security considerations..................................... 6
+ 5.7. Interoperability considerations............................. 6
+ 5.8. Published specification..................................... 6
+ 5.8.1. Line delimiting and folding............................... 6
+ 5.8.2. ABNF content-type definition.............................. 7
+ 5.8.3. Pre-defined Parameters.................................... 9
+ 5.8.4. Pre-defined Value Types...................................11
+ 5.9. Applications which use this media type......................14
+ 5.10. Additional information.....................................14
+ 5.11. Person & email address to contact for further information..14
+ 5.12. Intended usage.............................................14
+ 5.13. Author/Change controller...................................15
+ 6. Predefined Types..............................................15
+ 6.1. SOURCE Type Definition......................................15
+ 6.2. NAME Type Definition........................................16
+ 6.3. PROFILE Type Definition.....................................16
+ 6.4. BEGIN Type Definition.......................................17
+ 6.5. END Type Definition.........................................17
+ 7. Use of the multipart/related Content-Type.....................18
+ 8. Examples.......................................................18
+ 8.1. Example 1...................................................19
+ 8.2. Example 2...................................................19
+ 8.3. Example 3...................................................20
+ 8.4. Example 4...................................................21
+ 9. Registration of new profiles..................................22
+ 9.1. Define the profile..........................................22
+ 9.2. Post the profile definition.................................23
+ 9.3. Allow a comment period......................................23
+ 9.4. Submit the profile for approval.............................23
+ 10. Profile Change Control.......................................23
+
+
+
+Howes, et. al. Standards Track [Page 2]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ 11. Registration of new types....................................24
+ 11.1. Define the type............................................24
+ 11.2. Post the type definition...................................25
+ 11.3. Allow a comment period.....................................25
+ 11.4. Submit the type for approval...............................25
+ 12. Type Change Control..........................................25
+ 13. Registration of new parameters...............................26
+ 13.1. Define the parameter.......................................26
+ 13.2. Post the parameter definition..............................27
+ 13.3. Allow a comment period.....................................27
+ 13.4. Submit the parameter for approval..........................27
+ 14. Parameter Change Control.....................................28
+ 15. Registration of new value types..............................28
+ 15.1. Define the value type......................................28
+ 15.2. Post the value type definition.............................29
+ 15.3. Allow a comment period.....................................29
+ 15.4. Submit the value type for approval.........................29
+ 16. Security Considerations......................................30
+ 17. Acknowledgements..............................................30
+ 18. References....................................................30
+ 19. Authors' Addresses...........................................32
+ 20. Full Copyright Statement......................................33
+
+3. Need for a MIME Directory Type
+
+ For purposes of this document, a directory is a special-purpose
+ database that contains typed information. A directory usually
+ supports both read and search of the information it contains, and can
+ support creation and modification of the information as well.
+ Directory information is usually accessed far more often than it is
+ updated. Directories can be local or global in scope. They can be
+ distributed or centralized. The information they contain can be
+ replicated, with weak or strong consistency requirements.
+
+ There are several situations in which users of Internet mail might
+ wish to exchange directory information: the email analogy of a
+ "business card" exchange; the conveyance of directory information to
+ a user having only email access to the Internet; the provision of
+ machine-parseable address information when purchasing goods or
+ services over the Internet; etc. As MIME [RFC-2045, RFC-2046] is
+ used increasingly by other protocols, most notably HTTP, it can also
+ be useful for these protocols to carry directory information in MIME
+ format. Such a format, for example, could be used to represent URC
+ (uniform resource characteristics) information about resources on the
+ World Wide Web, or to provide a rudimentary directory service over
+ HTTP.
+
+
+
+
+
+Howes, et. al. Standards Track [Page 3]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+4. Overview
+
+ The scheme defined here for representing directory information in a
+ MIME Content-Type has two parts. First, the text/directory Content-
+ Type is defined for use in holding directory information within a
+ single body part, for example name, title, or email address. In its
+ simplest form, the format uses a "type:value" approach, which should
+ be easily parseable by existing MIME implementations and
+ understandable by users. More complicated situations can be
+ represented also. This document defines the general form the
+ information in the Content-Type should have, and the procedure by
+ which specific types and values (properties) for particular
+ applications can be defined. The framework is general enough to
+ handle information from any number of end directory services,
+ including LDAP [RFC-1777, RFC-1778], WHOIS++ [RFC-1835], and X.500
+ [X500].
+
+ Directory entries can include far more than just textual information.
+ Some such information (e.g., an image or sound) overlaps with
+ predefined MIME Content-Types. In these cases it can be desirable to
+ include the information in its well-known MIME format. This situation
+ is handled by using a multipart/related Content-Type as defined in
+ [RFC-2112]. The root component of this type is a text/directory body
+ part specifying any in-line information, and for information
+ contained in other Content-Types, the Content-IDs (in URI form) of
+ those parts.
+
+ In some applications, it can be useful to include a pointer (e.g, a
+ URI) to some directory information rather than the information
+ itself. This document defines a general mechanism for accomplishing
+ this.
+
+5. The text/directory Content-Type
+
+ The text/directory Content-Type is used to hold basic directory
+ information and URIs referencing other information, including other
+ MIME body parts holding supplementary or non-textual directory
+ information, such as an image or sound. It is defined as follows,
+ using the MIME media type registration template from [RFC-2048].
+
+ To: ietf-types@uninett.no
+ Subject: Registration of MIME media type text/directory
+
+5.1. MIME media type name
+
+ MIME media type name: text
+
+
+
+
+
+Howes, et. al. Standards Track [Page 4]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+5.2. MIME subtype name
+
+ MIME subtype name: directory
+
+5.3. Required parameters
+
+ Required parameters: charset
+
+ The "charset" parameter is as defined in [RFC-2046] for other body
+ parts. It is used to identify the default character set used within
+ the body part.
+
+5.4. Optional parameters
+
+ Optional parameters: profile
+
+ The "profile" parameter is used to convey the type(s) of entity(ies)
+ to which the directory information pertains and the likely set of
+ information associated with the entity(ies). It is intended only as a
+ guide to applications interpreting the information contained within
+ the body part. It SHOULD NOT be used to exclude or require particular
+ pieces of information unless a profile definition specifically calls
+ for this behavior. Unless specifically forbidden by a particular
+ profile definition, a text/directory content type can contain
+ arbitrary attribute/value pairs.
+
+ The value of the "profile" parameter is defined as follows. Profile
+ names are case insensitive (i.e., the profile name "vCard" is the
+ same as "VCARD" and "vcard" and "vcArD").
+
+ profile = x-name / iana-token
+
+ x-name = "x-" 1*(ALPHA / DIGIT / "-")
+ ; Names beginning with "x-" or "X-" are
+ ; reserved for experimental use not intended for released
+ ; products, or for use in bilateral agreements.
+
+ iana-token = <a publicly-defined extension token, registered
+ with IANA, as specified in Section 9 of this
+ document>
+
+5.5. Encoding considerations
+
+ The default encoding is 8bit. Otherwise, as specified by the
+ Content-Transfer-Encoding header field.
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 5]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+5.6. Security considerations
+
+ Directory information can be public or it can be protected from
+ unauthorized access by the directory service in which it resides.
+ Once the information leaves its native service, there can be no
+ guarantee that the same care will be taken by all services handling
+ the information. Furthermore, this specification defines no access
+ control mechanism by which information can be protected, or by which
+ access control information can be conveyed. Note that the integrity
+ and privacy of a text/directory body part can be protected by
+ enclosing it within an appropriate MIME-based security mechanism.
+
+5.7. Interoperability considerations
+
+ In order to make sense of directory information, applications must
+ share a common understanding of the types of information contained
+ within the Content-Type (the directory schema). This schema
+ information is not defined in this document, but rather in companion
+ documents (e.g., [MIME-VCARD]) that follow the requirements specified
+ in this document, or in bilateral agreements between communicating
+ parties.
+
+5.8. Published specification
+
+ The text/directory Content-Type contains directory information,
+ typically pertaining to a single directory entity or group of
+ entities. The content consists of one or more lines in the format
+ given below.
+
+5.8.1. Line delimiting and folding
+
+ Individual lines within the MIME text/directory Content Type body are
+ delimited by the [RFC-822] line break, which is a CRLF sequence
+ (ASCII decimal 13, followed by ASCII decimal 10). Long logical lines
+ of text can be split into a multiple-physical-line representation
+ using the following folding technique.
+
+ A logical line MAY be continued on the next physical line anywhere
+ between two characters by inserting a CRLF immediately followed by a
+ single white space character (space, ASCII decimal 32, or horizontal
+ tab, ASCII decimal 9). At least one character must be present on the
+ folded line. Any sequence of CRLF followed immediately by a single
+ white space character is ignored (removed) when processing the
+ content type. For example the line:
+
+ DESCRIPTION:This is a long description that exists on a long line.
+
+ Can be represented as:
+
+
+
+Howes, et. al. Standards Track [Page 6]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ DESCRIPTION:This is a long description
+ that exists on a long line.
+
+ It could also be represented as:
+
+ DESCRIPTION:This is a long descrip
+ tion that exists o
+ n a long line.
+
+ The process of moving from this folded multiple-line representation
+ of a type definition to its single line representation is called
+ unfolding. Unfolding is accomplished by regarding CRLF immediately
+ followed by a white space character (namely HTAB ASCII decimal 9 or
+ SPACE ASCII decimal 32) as equivalent to no characters at all (i.e.,
+ the CRLF and single white space character are removed).
+
+5.8.2. ABNF content-type definition
+
+ The following ABNF uses the notation of RFC 2234, which also defines
+ CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT. After the unfolding of
+ any folded lines as described above, the syntax for a line of this
+ content type is as follows:
+
+ contentline = [group "."] name *(";" param) ":" value CRLF
+ ; When parsing a content line, folded lines MUST first
+ ; be unfolded according to the unfolding procedure
+ ; described above.
+ ; When generating a content line, lines longer than 75
+ ; characters SHOULD be folded according to the folding
+ ; procedure described above.
+
+ group = 1*(ALPHA / DIGIT / "-")
+
+ name = x-name / iana-token
+
+ iana-token = 1*(ALPHA / DIGIT / "-")
+ ; identifier registered with IANA
+
+ x-name = "x-" 1*(ALPHA / DIGIT / "-")
+ ; Names that begin with "x-" or "X-" are
+ ; reserved for experimental use, not intended for released
+ ; products, or for use in bilateral agreements.
+
+ param = param-name "=" param-value *("," param-value)
+
+ param-name = x-name / iana-token
+
+ param-value = ptext / quoted-string
+
+
+
+Howes, et. al. Standards Track [Page 7]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ ptext = *SAFE-CHAR
+
+ value = *VALUE-CHAR
+ / valuespec ; valuespec defined in section 5.8.4
+
+ quoted-string = DQUOTE *QSAFE-CHAR DQUOTE
+
+ NON-ASCII = %x80-FF
+ ; use restricted by charset parameter
+ ; on outer MIME object (UTF-8 preferred)
+
+ QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-ASCII
+ ; Any character except CTLs, DQUOTE
+
+ SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-ASCII
+ ; Any character except CTLs, DQUOTE, ";", ":", ","
+
+ VALUE-CHAR = WSP / VCHAR / NON-ASCII
+ ; any textual character
+
+ A line that begins with a white space character is a continuation of
+ the previous line, as described above. The white space character and
+ immediately preceeding CRLF should be discarded when reconstructing
+ the original line. Note that this line-folding convention differs
+ from that found in RFC 822, in that the sequence <CRLF><WSP> found
+ anywhere in the content indicates a continued line and should be
+ removed.
+
+ Various type names and the format of the corresponding values are
+ defined as specified in Section 11. Specifications MAY impose
+ ordering on the type constructs within a body part, though none is
+ required by default. The various x-name constructs are used for
+ bilaterally-agreed upon type names, parameter names and parameter
+ values, or for use in experimental settings.
+
+ Type names and parameter names are case insensitive (e.g., the type
+ name "fn" is the same as "FN" and "Fn"). Parameter values MAY be case
+ sensitive or case insensitive, depending on their definition.
+
+ The group construct is used to group related attributes together.
+ The group name is a syntactic convention used to indicate that all
+ type names prefaced with the same group name SHOULD be grouped
+ together when displayed by an application. It has no other
+ significance. Implementations that do not understand or support
+ grouping MAY simply strip off any text before a "." to the left of
+ the type name and present the types and values as normal.
+
+
+
+
+
+Howes, et. al. Standards Track [Page 8]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Each attribute defined in the text/directory body MAY have multiple
+ values, if allowed in the definition of the profile in which the
+ attribute is used. The general rule for encoding multi-valued items
+ is to simply create a new content line for each value (including the
+ type name). However, it should be noted that some value types
+ support encoding multiple values in a single content line by
+ separating the values with a comma ",". This approach has been taken
+ for several of the content types defined below (date, time, integer,
+ float), for space-saving reasons.
+
+5.8.3. Pre-defined Parameters
+
+ The following parameters and value types are defined for general use.
+
+ predefined-param = encodingparm
+ / valuetypeparm
+ / languageparm
+ / contextparm
+
+ encodingparm = "encoding" "=" encodingtype
+
+ encodingtype = "b" ; from RFC 2047
+ / iana-token ; registered as described in
+ ; section 15 of this document
+
+ valuetypeparm = "value" "=" valuetype
+
+ valuetype = "uri" ; genericurl from secion 5 of RFC 1738
+ / "text"
+ / "date"
+ / "time"
+ / "date-time" ; date time
+ / "integer"
+ / "boolean"
+ / "float"
+ / x-name
+ / iana-token ; registered as described in
+ ; section 15 of this document
+
+ languageparm = "language" "=" Language-Tag
+ ; Language-Tag is defined in section 2 of RFC 1766
+
+ contextparm = "context" "=" context
+
+ context = x-name
+ / iana-token
+
+
+
+
+
+Howes, et. al. Standards Track [Page 9]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ The "language" type parameter is used to identify data in multiple
+ languages. There is no concept of "default" language, except as
+ specified by any "Content-Language" MIME header parameter that is
+ present. The value of the "language" type parameter is a language
+ tag as defined in Section 2 of [RFC-1766].
+
+ The "context" type parameter is used to identify a context (e.g., a
+ protocol) used in interpreting the value. This is used, for example,
+ in the "source" type, defined below.
+
+ The "encoding" type parameter is used to specify an alternate
+ encoding for a value. If the value contains a CRLF, it must be
+ encoded, since CRLF is used to separate lines in the content-type
+ itself. Currently, only the "b" encoding is supported.
+
+ The "b" encoding can also be useful for binary values that are mixed
+ with other text information in the body part (e.g., a certificate).
+ Using a per-value "b" encoding in this case leaves the other
+ information in a more readable form. The encoded base 64 value can be
+ split across multiple physical lines in the content type by using the
+ line folding technique described above.
+
+ The Content-Transfer-Encoding header field is used to specify the
+ encoding used for the body part as a whole. The "encoding" type
+ parameter is used to specify an encoding for a particular value
+ (e.g., a certificate). In this case, the Content-Transfer-Encoding
+ header might specify "8bit", while the one certificate value might
+ specify an encoding of "b" via an "encoding=b" type parameter.
+
+ The Content-Transfer-Encoding and the encodings of individual types
+ given by the "encoding" type parameter are independent of one
+ another. When encoding a text/directory body part for transmission,
+ individual type encodings are performed first, then the entire body
+ part is encoded according to the Content-Transfer-Encoding. When
+ decoding a text/directory body part, the Content-Transfer-Encoding is
+ decoded first, and then any individual types with an "encoding" type
+ parameter are decoded.
+
+ The "value" parameter is optional, and is used to identify the value
+ type (data type) and format of the value. The use of these
+ predefined formats is encouraged even if the value parameter is not
+ explicity used. By defining a standard set of value types and their
+ formats, existing parsing and processing code can be leveraged.
+
+ Including the value type explicitly as part of each property provides
+ an extra hint to keep parsing simple and support more generalized
+ applications. For example a search engine would not have to know the
+ particular value types for all of the items for which it is
+
+
+
+Howes, et. al. Standards Track [Page 10]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ searching. Because the value type is explicit in the definition, the
+ search engine could look for dates in any item type and provide
+ results that can still be interpreted.
+
+5.8.4. Pre-defined Value Types
+
+ The format for values corresponding to the predefined valuetype
+ specifications given above are defined.
+
+ valuespec = text-list
+ / genericurl ; from section 5 of RFC 1738
+ / date-list
+ / time-list
+ / date-time-list
+ / boolean
+ / integer-list
+ / float-list
+ / iana-valuespec
+
+ text-list = *TEXT-LIST-CHAR *("," *TEXT-LIST-CHAR)
+
+ TEXT-LIST-CHAR = "\\" / "\," / "\n"
+ / <any VALUE-CHAR except , or \ or newline>
+ ; Backslashes, newlines, and commas must be encoded.
+ ; \n or \N can be used to encode a newline.
+
+ date-list = date *("," date)
+
+ time-list = time *("," time)
+
+ date-time-list = date "T" time *("," date "T" time)
+
+ boolean = "TRUE" / "FALSE"
+
+ integer-list = integer *("," integer)
+
+ integer = [sign] 1*DIGIT
+
+ float-list = float *("," float)
+
+ float = [sign] 1*DIGIT ["." 1*DIGIT]
+
+ sign = "+" / "-"
+
+ date = date-fullyear ["-"] date-month ["-"] date-mday
+
+ date-fullyear = 4 DIGIT
+
+
+
+
+Howes, et. al. Standards Track [Page 11]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ date-month = 2 DIGIT ;01-12
+
+ date-mday = 2 DIGIT ;01-28, 01-29, 01-30, 01-31
+ ;based on month/year
+
+ time = time-hour [":"] time-minute [":"] time-second [time-secfrac]
+ [time-zone]
+
+ time-hour = 2 DIGIT ;00-23
+
+ time-minute = 2 DIGIT ;00-59
+
+ time-second = 2 DIGIT ;00-60 (leap second)
+
+ time-secfrac = "," 1*DIGIT
+
+ time-zone = "Z" / time-numzone
+
+ time-numzome = sign time-hour [":"] time-minute
+
+ iana-valuespec = <a publicly-defined valuetype format, registered
+ with IANA, as defined in section 15 of this
+ document>
+
+ Some specific notes on the value types and formats:
+
+ "text": The "text" value type should be used to identify values that
+ contain human-readable text. The character set and language in which
+ the text is represented is controlled by the charset content-header
+ and the language type parameter and content-header.
+
+ Examples for "text":
+ this is a text value
+ this is one value,this is another
+ this is a single value\, with a comma encoded
+
+ A formatted text line break in a text value type MUST be represented
+ as the character sequence backslash (ASCII decimal 92) followed by a
+ Latin small letter n (ASCII decimal 110) or a Latin capital letter N
+ (ASCII decimal 78), that is "\n" or "\N".
+
+ For example a multiple line DESCRIPTION value of:
+
+ Mythical Manager
+ Hyjinx Software Division
+ BabsCo, Inc.
+
+ could be represented as:
+
+
+
+Howes, et. al. Standards Track [Page 12]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ DESCRIPTION:Mythical Manager\nHyjinx Software Division\n
+ BabsCo\, Inc.\n
+
+ demonstrating the \n literal formatted line break technique, the
+ CRLF-followed-by-space line folding technique, and the backslash
+ escape technique.
+
+ "uri": The "uri" value type should be used to identify values that
+ are referenced by a URI (including a Content-ID URI), instead of
+ encoded in-line. These value references might be used if the value is
+ too large, or otherwise undesirable to include directly. The format
+ for the URI is as defined in RFC 1738.
+
+ Examples for "uri":
+ http://www.foobar.com/my/picture.jpg
+ ldap://ldap.foobar.com/cn=babs%20jensen
+
+ "date", "time", and "date-time": Each of these value types is based
+ on a subset of the definitions in ISO 8601 standard. Profiles MAY
+ place further restrictions on "date" and "time" values. Multiple
+ "date" and "time" values can be specified using the comma-separated
+ notation, unless restricted by a profile.
+
+ Examples for "date":
+ 1985-04-12
+ 1996-08-05,1996-11-11
+ 19850412
+
+ Examples for "time":
+ 10:22:00
+ 102200
+ 10:22:00.33
+ 10:22:00.33Z
+ 10:22:33,11:22:00
+ 10:22:00-08:00
+
+ Examples for "date-time":
+ 1996-10-22T14:00:00Z
+ 1996-08-11T12:34:56Z
+ 19960811T123456Z
+ 1996-10-22T14:00:00Z,1996-08-11T12:34:56Z
+
+ "boolean": The "boolean" value type is used to express boolen values.
+ These values are case insensitive.
+
+ Examples: TRUE
+ false
+ True
+
+
+
+Howes, et. al. Standards Track [Page 13]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ "integer": The "integer" value type is used to express signed
+ integers in decimal format. If sign is not specified, the value is
+ assumed positive "+". Multiple "integer" values can be specified
+ using the comma-separated notation, unless restricted by a profile.
+
+ Examples: 1234567890
+ -1234556790
+ +1234556790,432109876
+
+ "float": The "float" value type is used to express real numbers. If
+ sign is not specified, the value is assumed positive "+". Multiple
+ "float" values can be specified using the comma-separated notation,
+ unless restricted by a profile.
+
+ Examples: 20.30
+ 1000000.0000001
+ 1.333,3.14
+
+5.9. Applications which use this media type
+
+ Applications which use this media type: Various
+
+5.10. Additional information
+
+ Additional information: None
+
+5.11. Person & email address to contact for further information
+
+ Tim Howes
+ Netscape Communications Corp.
+ 501 East Middlefield Rd.
+ Mountain View, CA 94041
+ USA
+ howes@netscape.com
+ +1 415 937 3419
+
+5.12. Intended usage
+
+ Intended usage: COMMON
+
+
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 14]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+5.13. Author/Change controller
+
+ Tim Howes
+ Netscape Communications Corp.
+ 501 East Middlefield Rd.
+ Mountain View, CA 94041
+ USA
+ howes@netscape.com
+ +1 415 937 3419
+
+ Mark Smith
+ Netscape Communications Corp.
+ 501 East Middlefield Rd.
+ Mountain View, CA 94041
+ USA
+ mcs@netscape.com
+ +1 415 937 3477
+
+ Frank Dawson
+ Lotus Development Corporation
+ 6544 Battleford Drive
+ Raleigh, NC 27613-3502
+ USA
+ frank_dawson@lotus.com
+ +1-919-676-9515
+
+6. Predefined Types
+
+ The following types are generally useful regardless of the profile
+ being carried and are defined below using the text/directory MIME
+ type registration template defined in Section 11.1 of this document.
+ These types MAY be included in any profile, unless explicitly
+ forbidden in the profile definition.
+
+6.1. SOURCE Type Definition
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type SOURCE
+
+ Type name: SOURCE
+
+ Type purpose: To identify the source of directory information
+ contained in the content type.
+
+ Type encoding: 8bit
+
+ Type valuetype: uri
+
+
+
+
+Howes, et. al. Standards Track [Page 15]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Type special notes: The SOURCE type is used to provide the means by
+ which applications knowledgable in the given directory service
+ protocol can obtain additional or more up-to-date information from
+ the directory service. It contains a URI as defined in [RFC-1738]
+ and/or other information referencing the directory entity or entities
+ to which the information pertains. When directory information is
+ available from more than one source, the sending entity can pick what
+ it considers to be the best source, or multiple SOURCE types can be
+ included. The interpretation of the value for a SOURCE type can
+ depend on the setting of the CONTEXT type parameter. The value of the
+ CONTEXT type parameter MUST be compatible with the value of the uri
+ prefix.
+
+ Type example:
+ SOURCE;CONTEXT=LDAP:ldap://ldap.host/cn=Babs%20Jensen,
+ %20o=Babsco,%20c=US
+
+6.2. NAME Type Definition
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type NAME
+
+ Type name: NAME
+
+ Type purpose: To identify the displayable name of the directory
+ entity to which information in the content type pertains.
+
+ Type encoding: 8bit
+
+ Type valuetype: text
+
+ Type special notes: The NAME type is used to convey the display name
+ of the entity to which the directory information pertains.
+
+ Type example:
+ NAME:Babs Jensen's Contact Information
+
+6.3. PROFILE Type Definition
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type PROFILE
+
+ Type name: PROFILE
+
+ Type purpose: To identify the type of directory entity to which
+ information in the content type pertains.
+
+ Type encoding: 8bit
+
+
+
+Howes, et. al. Standards Track [Page 16]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Type valuetype: A profile name, registered as described in Section 9
+ of this document or bilaterally agreed upon as described in Section
+ 5.
+
+ Type special notes: The PROFILE type is used to convey the type of
+ the entity to which the directory information in the rest of the body
+ part pertains. It should be the same as the "profile" header
+ parameter, if present.
+
+ Type example:
+ PROFILE:vCard
+
+6.4. BEGIN Type Definition
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type BEGIN
+
+ Type name: BEGIN
+
+ Type purpose: To denote the beginning of a syntactic entity within a
+ text/directory content-type.
+
+ Type encoding: 8bit
+
+ Type valuetype: text, containing a profile name, registered as
+ described in Section 9 of this document or bilaterally-agreed upon as
+ described in Section 5.
+
+ Type special notes: The BEGIN type is used in conjunction with the
+ END type to delimit a profile containing a related set of properties
+ within an text/directory content-type. This construct can be used
+ instead of or in addition to wrapping separate sets of information
+ inside additional MIME headers. It is provided for applications that
+ wish to define content that can contain multiple entities within the
+ same text/directory content-type or to define content that can be
+ identifiable outside of a MIME environment.
+
+ Type example:
+ BEGIN:VCARD
+
+6.5. END Type Definition
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type END
+
+ Type name: END
+
+
+
+
+
+Howes, et. al. Standards Track [Page 17]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Type purpose: To denote the end of a syntactic entity within a
+ text/directory content-type.
+
+ Type encoding: 8bit
+
+ Type valuetype: text, containing a profile name, registered as
+ described in Section 9 of this document or bilaterally-agreed upon as
+ described in Section 5.
+
+ Type special notes: The END type is used in conjunction with the
+ BEGIN type to delimit a profile containing a related set of
+ properties within an text/directory content-type. This construct can
+ be used instead of or in addition to wrapping separate sets of
+ information inside additional MIME headers. It is provided for
+ applications that wish to define content that can contain multiple
+ entities within the same text/directory content-type or to define
+ content that can be identifiable outside of a MIME environment.
+
+ Type example:
+ END: VCARD
+
+7. Use of the multipart/related Content-Type
+
+ The multipart/related Content-Type can be used to hold directory
+ information comprised of both text and non-text information or
+ directory information that already has a natural MIME representation.
+ The root body part within the multipart/related body part is
+ specified as defined in [RFC-2112] by a "start" parameter, or it is
+ the first body part in the absence of such a parameter. The root
+ body part must have a Content-Type of "text/directory". This part
+ holds inline information and makes reference to subsequent body parts
+ holding additional text or non-text directory information via their
+ Content-ID URIs as explained in Section 5.
+
+ The body parts referred to do not have to be in any particular order,
+ except as noted above for the root body part.
+
+8. Examples
+
+ The following examples are for illustrative purposes only and are not
+ part of the definition.
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 18]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+8.1. Example 1
+
+ The first example illustrates simple use of the text/directory
+ Content-Type. Note that no "profile" parameter is given, so an
+ application may not know what kind of directory entity the
+ information applies to. Note also the use of both hypothetical
+ official and bilaterally agreed upon types.
+
+ From: Whomever@wherever.com
+ To: Someone@somewhere.com
+ Subject: whatever
+ MIME-Version: 1.0
+ Message-ID: <id1@host.net>
+ Content-Type: text/directory
+ Content-ID: <id2@host.com>
+
+ cn:Babs Jensen
+ cn:Barbara J Jensen
+ sn:Jensen
+ email:babs@umich.edu
+ phone:+1 313 747-4454
+ x-id:1234567890
+
+8.2. Example 2
+
+ The next example illustrates the use of the Quoted-Printable transfer
+ encoding defined in [RFC 2045] to include non-ASCII character in some
+ of the information returned, and the use of the optional "name" and
+ "source" types. It also illustrates the use of an "encoding" type
+ parameter to encode a certificate value in "b". A "vCard" profile
+ [MIME- VCARD] is used for the example.
+
+Content-Type: text/directory;
+ charset="iso-8859-1";
+ profile="vCard"
+Content-ID: <id3@host.com>
+Content-Transfer-Encoding: Quoted-Printable
+
+begin:VCARD
+source:ldap://cn=bjorn%20Jensen, o=university%20of%20Michigan, c=US
+name:Bjorn Jensen
+fn:Bj=F8rn Jensen
+n:Jensen;Bj=F8rn
+email;type=internet:bjorn@umich.edu
+tel;type=work,voice,msg:+1 313 747-4454
+key;type=x509;encoding=B:dGhpcyBjb3VsZCBiZSAKbXkgY2VydGlmaWNhdGUK
+end:VCARD
+
+
+
+
+Howes, et. al. Standards Track [Page 19]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+8.3. Example 3
+
+ The next example illustrates the use of multi-valued type parameters,
+ the "language" type parameter, the "value" type parameter, folding of
+ long lines, the \n encoding for formatted lines, attribute grouping,
+ and the inline "b" encoding. A "vCard" profile [MIME-VCARD] is used
+ for the example.
+
+Content-Type: text/directory; profile="vcard"; charset=iso-8859-1
+Content-ID: <id3@host.com>
+Content-Transfer-Encoding: Quoted-Printable
+
+begin:vcard
+source:ldap://cn=Meister%20Berger,o=Universitaet%20Goerlitz,c=DE
+name:Meister Berger
+fn:Meister Berger
+n:Berger;Meister
+bday;value=date:1963-09-21
+o:Universit=E6t G=F6rlitz
+title:Mayor
+title;language=de;value=text:Burgermeister
+note:The Mayor of the great city of
+ Goerlitz in the great country of Germany.
+email;internet:mb@goerlitz.de
+home.tel;type=fax,voice,msg:+49 3581 123456
+home.label:Hufenshlagel 1234\n
+ 02828 Goerlitz\n
+ Deutschland
+key;type=X509;encoding=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQ
+ AwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zI
+ ENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0ZW1zMRwwGgYDVQQD
+ ExNyb290Y2EubmV0c2NhcGUuY29tMB4XDTk3MDYwNjE5NDc1OVoXDTk3MTIwMzE5NDc
+ 1OVowgYkxCzAJBgNVBAYTAlVTMSYwJAYDVQQKEx1OZXRzY2FwZSBDb21tdW5pY2F0aW
+ 9ucyBDb3JwLjEYMBYGA1UEAxMPVGltb3RoeSBBIEhvd2VzMSEwHwYJKoZIhvcNAQkBF
+ hJob3dlc0BuZXRzY2FwZS5jb20xFTATBgoJkiaJk/IsZAEBEwVob3dlczBcMA0GCSqG
+ SIb3DQEBAQUAA0sAMEgCQQC0JZf6wkg8pLMXHHCUvMfL5H6zjSk4vTTXZpYyrdN2dXc
+ oX49LKiOmgeJSzoiFKHtLOIboyludF90CgqcxtwKnAgMBAAGjNjA0MBEGCWCGSAGG+E
+ IBAQQEAwIAoDAfBgNVHSMEGDAWgBT84FToB/GV3jr3mcau+hUMbsQukjANBgkqhkiG9
+ w0BAQQFAAOBgQBexv7o7mi3PLXadkmNP9LcIPmx93HGp0Kgyx1jIVMyNgsemeAwBM+M
+ SlhMfcpbTrONwNjZYW8vJDSoi//yrZlVt9bJbs7MNYZVsyF1unsqaln4/vy6Uawfg8V
+ UMk1U7jt8LYpo4YULU7UZHPYVUaSgVttImOHZIKi4hlPXBOhcUQ==
+end:vcard
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 20]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+8.4. Example 4
+
+ The final example illustrates the use of the multipart/related
+ Content-Type to include non-textual directory data via the "uri"
+ encoding to refer to other body parts within the same message, or to
+ external values. Note that no "profile" parameter is given, so an
+ application may not know what kind of directory entity the
+ information applies to. Note also the use of both hypothetical
+ official and bilaterally agreed upon types.
+
+Content-Type: multipart/related;
+ boundary=woof;
+ type="text/directory";
+ start="<id5@host.com>"
+Content-ID: <id4@host.com>
+
+--woof
+Content-Type: text/directory; charset="iso-8859-1"
+Content-ID: <id5@host.com>
+Content-Transfer-Encoding: Quoted-Printable
+
+source:ldap://cn=Bjorn%20Jensen,o=University%20of%20Michigan,c=US
+cn:Bj=F8rn Jensen
+sn:Jensen
+email:bjorn@umich.edu
+image;value=uri:cid:id6@host.com
+image;value=uri;format=jpeg:ftp://some.host/some/path.jpg
+sound;value=uri:cid:id7@host.com
+phone:+1 313 747-4454
+
+--woof
+Content-Type: image/jpeg
+Content-ID: <id6@host.com>
+
+<...image data...>
+
+--woof
+Content-Type: message/external-body;
+ name="myvoice.au";
+ site="myhost.com";
+ access-type=ANON-FTP;
+ directory="pub/myname";
+ mode="image"
+
+Content-Type: audio/basic
+Content-ID: <id7@host.com>
+
+--woof--
+
+
+
+Howes, et. al. Standards Track [Page 21]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+9. Registration of new profiles
+
+ This section defines procedures by which new profiles are registered
+ with the IANA and made available to the Internet community. Note that
+ non-IANA profiles can be used by bilateral agreement, provided the
+ associated profile names follow the "X-" convention defined above.
+
+ The procedures defined here are designed to allow public comment and
+ review of new profiles, while posing only a small impediment to the
+ definition of new profiles.
+
+ Registration of a new profile is accomplished by the following steps.
+
+9.1. Define the profile
+
+ A profile is defined by completing the following template.
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME profile XXX
+
+ Profile name:
+
+ Profile purpose:
+
+ Profile types:
+
+ Profile special notes (optional):
+
+ Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
+
+ The explanation of what goes in each field in the template follows.
+
+ Profile name: The name of the profile as it will appear in the
+ text/directory MIME Content-Type "profile" header parameter, or the
+ predefined "profile" type name.
+
+ Profile purpose: The purpose of the profile (e.g., to represent
+ information about people, printers, documents, etc.). Give a short
+ but clear description.
+
+ Profile types: The list of types associated with the profile. This
+ list of types is to be expected but not required in the profile,
+ unless otherwise noted in the profile definition. Other types not
+ mentioned in the profile definition MAY also be present. Note that
+ any new types referenced by the profile MUST be defined separately as
+ described in Section 10.
+
+
+
+
+
+Howes, et. al. Standards Track [Page 22]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Profile special notes: Any special notes about the profile, how it is
+ to be used, etc. This section of the template can also be used to
+ define an ordering on the types that appear in the Content-Type, if
+ such an ordering is required.
+
+9.2. Post the profile definition
+
+ The profile description must be posted to the new profile discussion
+ list, ietf-mime-direct@imc.org
+
+9.3. Allow a comment period
+
+ Discussion on the new profile must be allowed to take place on the
+ list for a minimum of two weeks. Consensus must be reached on the
+ profile before proceeding to step 4.
+
+9.4. Submit the profile for approval
+
+ Once the two-week comment period has elapsed, and the proposer is
+ convinced consensus has been reached on the profile, the registration
+ application should be submitted to the Profile Reviewer for approval.
+ The Profile Reviewer is appointed by the Application Area Directors
+ and can either accept or reject the profile registration. An accepted
+ registration is passed on by the Profile Reviewer to the IANA for
+ inclusion in the official IANA profile registry. The registration may
+ be rejected for any of the following reasons. 1) Insufficient comment
+ period; 2) Consensus not reached; 3) Technical deficiencies raised on
+ the list or elsewhere have not been addressed. The Profile Reviewer's
+ decision to reject a profile can be appealed by the proposer to the
+ IESG, or the objections raised can be addressed by the proposer and
+ the profile resubmitted.
+
+10. Profile Change Control
+
+ Existing profiles can be changed using the same process by which they
+ were registered.
+
+ Define the change
+
+ Post the change
+
+ Allow a comment period
+
+ Submit the changed profile for approval
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 23]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Note that the original author or any other interested party can
+ propose a change to an existing profile, but that such changes should
+ only be proposed when there are serious omissions or errors in the
+ published specification. The Profile Reviewer can object to a change
+ if it is not backwards compatible, but is not required to do so.
+
+ Profile definitions can never be deleted from the IANA registry, but
+ profiles which are no longer believed to be useful can be declared
+ OBSOLETE by a change to their "intended use" field.
+
+11. Registration of new types
+
+ This section defines procedures by which new types are registered
+ with the IANA. Note that non-IANA types can be used by bilateral
+ agreement, provided the associated types names follow the "X-"
+ convention defined above.
+
+ The procedures defined here are designed to allow public comment and
+ review of new types, while posing only a small impediment to the
+ definition of new types.
+
+ Registration of a new type is accomplished by the following steps.
+
+11.1. Define the type
+
+ A type is defined by completing the following template.
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type XXX
+
+ Type name:
+
+ Type purpose:
+
+ Type encoding:
+
+ Type valuetype:
+
+ Type special notes (optional):
+
+ Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
+
+ The meaning of each field in the template is as follows.
+
+ Type name: The name of the type, as it will appear in the body of an
+ text/directory MIME Content-Type "type: value" line to the left of
+ the colon ":".
+
+
+
+
+Howes, et. al. Standards Track [Page 24]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Type purpose: The purpose of the type (e.g., to represent a name,
+ postal address, IP address, etc.). Give a short but clear
+ description.
+
+ Type encoding: The default encoding a value of the type must have in
+ the body of a text/directory MIME Content-Type.
+
+ Type valuetype: The format a value of the type must have in the body
+ of a text/directory MIME Content-Type. This description must be
+ precise and must not violate the general encoding rules defined in
+ section 5 of this document.
+
+ Type special notes: Any special notes about the type, how it is to be
+ used, etc.
+
+11.2. Post the type definition
+
+ The type description must be posted to the new type discussion list,
+ ietf-mime-direct@imc.org
+
+11.3. Allow a comment period
+
+ Discussion on the new type must be allowed to take place on the list
+ for a minimum of two weeks. Consensus must be reached on the type
+ before proceeding to step 4.
+
+11.4. Submit the type for approval
+
+ Once the two-week comment period has elapsed, and the proposer is
+ convinced consensus has been reached on the type, the registration
+ application should be submitted to the Profile Reviewer for approval.
+ The Profile Reviewer is appointed by the Application Area Directors
+ and can either accept or reject the type registration. An accepted
+ registration is passed on by the Profile Reviewer to the IANA for
+ inclusion in the official IANA profile registry. The registration can
+ be rejected for any of the following reasons. 1) Insufficient comment
+ period; 2) Consensus not reached; 3) Technical deficiencies raised on
+ the list or elsewhere have not been addressed. The Profile
+ Reviewer's decision to reject a type can be appealed by the proposer
+ to the IESG, or the objections raised can be addressed by the
+ proposer and the type resubmitted.
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 25]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+12. Type Change Control
+
+ Existing types can be changed using the same process by which they
+ were registered.
+
+ Define the change
+
+ Post the change
+
+ Allow a comment period
+
+ Submit the type for approval
+
+ Note that the original author or any other interested party can
+ propose a change to an existing type, but that such changes should
+ only be proposed when there are serious omissions or errors in the
+ published specification. The Profile Reviewer can object to a change
+ if it is not backwards compatible, but is not required to do so.
+
+ Type definitions can never be deleted from the IANA registry, but
+ types which are nolonger believed to be useful can be declared
+ OBSOLETE by a change to their "intended use" field.
+
+13. Registration of new parameters
+
+ This section defines procedures by which new parameters are
+ registered with the IANA and made available to the Internet
+ community. Note that non-IANA parameters can be used by bilateral
+ agreement, provided the associated parameters names follow the "X-"
+ convention defined above.
+
+ The procedures defined here are designed to allow public comment and
+ review of new parameters, while posing only a small impediment to the
+ definition of new parameters.
+
+ Registration of a new parameter is accomplished by the following
+ steps.
+
+13.1. Define the parameter
+
+ A parameter is defined by completing the following template.
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME type parameter XXX
+
+ Parameter name:
+
+ Parameter purpose:
+
+
+
+Howes, et. al. Standards Track [Page 26]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ Parameter values:
+
+ Parameter special notes (optional):
+
+ Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
+
+ The explanation of what goes in each field in the template follows.
+
+ Parameter name: The name of the parameter as it will appear in the
+ text/directory MIME Content-Type.
+
+ Parameter purpose: The purpose of the parameter (e.g., to represent
+ the format of an image, type of a phone number, etc.). Give a short
+ but clear description. If defining a general paramemter like "format"
+ or "type" keep in mind that other applications might wish to extend
+ its use.
+
+ Parameter values: The list or description of values associated with
+ the parameter.
+
+ Parameter special notes: Any special notes about the parameter, how
+ it is to be used, etc.
+
+13.2. Post the parameter definition
+
+ The parameter description must be posted to the new parameter
+ discussion list, ietf-mime-direct@imc.org
+
+13.3. Allow a comment period
+
+ Discussion on the new parameter must be allowed to take place on the
+ list for a minimum of two weeks. Consensus must be reached on the
+ parameter before proceeding to step 4.
+
+13.4. Submit the parameter for approval
+
+ Once the two-week comment period has elapsed, and the proposer is
+ convinced consensus has been reached on the parameter, the
+ registration application should be submitted to the Profile Reviewer
+ for approval. The Profile Reviewer is appointed by the Application
+ Area Directors and can either accept or reject the parameter
+ registration. An accepted registration is passed on by the Profile
+ Reviewer to the IANA for inclusion in the official IANA parameter
+ registry. The registration can be rejected for any of the following
+ reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
+ Technical deficiencies raised on the list or elsewhere have not been
+ addressed. The Profile Reviewer's decision to reject a profile can be
+ appealed by the proposer to the IESG, or the objections raised can be
+
+
+
+Howes, et. al. Standards Track [Page 27]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ addressed by the proposer and the parameter registration resubmitted.
+
+14. Parameter Change Control
+
+ Existing parameters can be changed using the same process by which
+ they were registered.
+
+ Define the change
+
+ Post the change
+
+ Allow a comment period
+
+ Submit the parameter for approval
+
+ Note that the original author or any other interested party can
+ propose a change to an existing parameter, but that such changes
+ should only be proposed when there are serious omissions or errors in
+ the published specification. The Profile Reviewer can object to a
+ change if it is not backwards compatible, but is not required to do
+ so.
+
+ Parameter definitions can never be deleted from the IANA registry,
+ but parameters which are nolonger believed to be useful can be
+ declared OBSOLETE by a change to their "intended use" field.
+
+15. Registration of new value types
+
+ This section defines procedures by which new value types are
+ registered with the IANA and made available to the Internet
+ community. Note that non-IANA value types can be used by bilateral
+ agreement, provided the associated value types names follow the "X-"
+ convention defined above.
+
+ The procedures defined here are designed to allow public comment and
+ review of new value types, while posing only a small impediment to
+ the definition of new value types.
+
+ Registration of a new value types is accomplished by the following
+ steps.
+
+15.1. Define the value type
+
+ A value type is defined by completing the following template.
+
+ To: ietf-mime-direct@imc.org
+ Subject: Registration of text/directory MIME value type XXX
+
+
+
+
+Howes, et. al. Standards Track [Page 28]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ value type name:
+
+ value type purpose:
+
+ value type format:
+
+ value type special notes (optional):
+
+ Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
+
+ The explanation of what goes in each field in the template follows.
+
+ value type name: The name of the value type as it will appear in the
+ text/directory MIME Content-Type.
+
+ value type purpose: The purpose of the value type. Give a short but
+ clear description.
+
+ value type format: The definition of the format for the value,
+ usually using ABNF grammar.
+
+ value type special notes: Any special notes about the value type, how
+ it is to be used, etc.
+
+15.2. Post the value type definition
+
+ The value type description must be posted to the new value type
+ discussion list, ietf-mime-direct@imc.org
+
+15.3. Allow a comment period
+
+ Discussion on the new value type must be allowed to take place on the
+ list for a minimum of two weeks. Consensus must be reached before
+ proceeding to step 4.
+
+15.4. Submit the value type for approval
+
+ Once the two-week comment period has elapsed, and the proposer is
+ convinced consensus has been reached on the value type, the
+ registration application should be submitted to the Profile Reviewer
+ for approval. The Profile Reviewer is appointed by the Application
+ Area Directors and can either accept or reject the value type
+ registration. An accepted registration should be passed on by the
+ Profile Reviewer to the IANA for inclusion in the official IANA value
+ type registry. The registration can be rejected for any of the
+ following reasons. 1) Insufficient comment period; 2) Consensus not
+ reached; 3) Technical deficiencies raised on the list or elsewhere
+ have not been addressed. The Profile Reviewer's decision to reject a
+
+
+
+Howes, et. al. Standards Track [Page 29]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ profile can be appealed by the proposer to the IESG, or the
+ objections raised can be addressed by the proposer and the value type
+ registration resubmitted.
+
+16. Security Considerations
+
+ Internet mail is subject to many well known security attacks,
+ including monitoring, replay, and forgery. Care should be taken by
+ any directory service in allowing information to leave the scope of
+ the service itself, where any access controls can no longer be
+ guaranteed. Applications should also take care to display directory
+ data in a "safe" environment (e.g., PostScript-valued types).
+
+17. Acknowledgements
+
+ The registration procedures defined here were shamelessly lifted from
+ the MIME registration RFC.
+
+ The many valuable comments contributed by members of the IETF ASID
+ working group are gratefully acknowledged, as are the contributions
+ of the Versit Consortium. Chris Newman was especially helpful in
+ navigating the intricacies of ABNF lore.
+
+18. References
+
+ [RFC-1777] Yeong, W., Howes, T., and S. Kille, "Lightweight
+ Directory Access Protocol", RFC 1777, March 1995.
+
+ [RFC-1778] Howes, T., Kille, S., Yeong, W., and C. Robbins, "The
+ String Representation of Standard Attribute Syntaxes",
+ RFC 1778, March 1995.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822, August 1982.
+
+ [RFC-2045] Borenstein, N., and N. Freed, "Multipurpose Internet
+ Mail Extensions (MIME) Part One: Format of Internet
+ Message Bodies", RFC 2045, November 1996.
+
+ [RFC-2046] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
+ Part Two: Media Types", RFC 2046, November 1996.
+
+ [RFC-2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) Part Four: Registration
+ Procedures", RFC 2048, November 1996.
+
+ [RFC-1766] Alvestrand, H., "Tags for the Identification of
+ Languages", RFC 1766, March 1995.
+
+
+
+Howes, et. al. Standards Track [Page 30]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+ [RFC-2112] Levinson, E., "The MIME Multipart/Related Content-type",
+ RFC 2112, March 1997.
+
+ [X500] "Information Processing Systems - Open Systems
+ Interconnection - The Directory: Overview of Concepts,
+ Models and Services", ISO/IEC JTC 1/SC21, International
+ Standard 9594-1, 1988.
+
+ [RFC-1835] Deutsch, P., Schoultz, R., Faltstrom, P., and C. Weider,
+ "Architecture of the WHOIS++ service", RFC 1835, August
+ 1995.
+
+ [RFC-1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
+ Resource Locators (URL)", RFC 1738, December 1994.
+
+ [MIME-VCARD] Dawson, F., and T. Howes, "VCard MIME Directory
+ Profile", RFC 2426, September 1998.
+
+ [VCARD] Internet Mail Consortium, "vCard - The Electronic
+ Business Card", Version 2.1,
+ http://www.imc.com/pdi/vcard-21.txt, September, 1996.
+
+ [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC-2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 31]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+19. Authors' Addresses
+
+ Tim Howes
+ Netscape Communications Corp.
+ 501 East Middlefield Rd.
+ Mountain View, CA 94041
+ USA
+
+ Phone: +1.415.937.3419
+ EMail: howes@netscape.com
+
+
+ Mark Smith
+ Netscape Communications Corp.
+ 501 East Middlefield Rd.
+ Mountain View, CA 94041
+ USA
+
+ Phone: +1.415.937.3477
+ EMail: mcs@netscape.com
+
+
+ Frank Dawson
+ Lotus Development Corporation
+ 6544 Battleford Drive
+ Raleigh, NC 27613
+ USA
+
+ Phone: +1-919-676-9515
+ EMail: frank_dawson@lotus.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 32]
+
+RFC 2425 MIME Content-Type for Directory Information September 1998
+
+
+20. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Howes, et. al. Standards Track [Page 33]
+
diff --git a/rfc/rfc2426.txt b/rfc/rfc2426.txt
@@ -0,0 +1,2355 @@
+
+
+
+
+
+
+Network Working Group F. Dawson
+Request for Comments: 2426 Lotus Development Corporation
+Category: Standards Track T. Howes
+ Netscape Communications
+ September 1998
+
+
+ vCard MIME Directory Profile
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+Abstract
+
+ This memo defines the profile of the MIME Content-Type [MIME-DIR] for
+ directory information for a white-pages person object, based on a
+ vCard electronic business card. The profile definition is independent
+ of any particular directory service or protocol. The profile is
+ defined for representing and exchanging a variety of information
+ about an individual (e.g., formatted and structured name and delivery
+ addresses, email address, multiple telephone numbers, photograph,
+ logo, audio clips, etc.). The directory information used by this
+ profile is based on the attributes for the person object defined in
+ the X.520 and X.521 directory services recommendations. The profile
+ also provides the method for including a [VCARD] representation of a
+ white-pages directory entry within the MIME Content-Type defined by
+ the [MIME-DIR] document.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC 2119].
+
+
+
+
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 1]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+Table of Contents
+
+ Overview.........................................................3
+ 1. THE VCARD MIME DIRECTORY PROFILE REGISTRATION.................4
+ 2. MIME DIRECTORY FEATURES.......................................5
+ 2.1 PREDEFINED TYPE USAGE ......................................5
+ 2.1.1 BEGIN and END Type ......................................5
+ 2.1.2 NAME Type ...............................................5
+ 2.1.3 PROFILE Type ............................................5
+ 2.1.4 SOURCE Type .............................................5
+ 2.2 PREDEFINED TYPE PARAMETER USAGE ............................6
+ 2.3 PREDEFINED VALUE TYPE USAGE ................................6
+ 2.4 EXTENSIONS TO THE PREDEFINED VALUE TYPES ...................6
+ 2.4.1 BINARY ..................................................6
+ 2.4.2 VCARD ...................................................6
+ 2.4.3 PHONE-NUMBER ............................................7
+ 2.4.4 UTC-OFFSET ..............................................7
+ 2.5 STRUCTURED TYPE VALUES .....................................7
+ 2.6 LINE DELIMITING AND FOLDING ................................8
+ 3. VCARD PROFILE FEATURES........................................8
+ 3.1 IDENTIFICATION TYPES .......................................8
+ 3.1.1 FN Type Definition ......................................8
+ 3.1.2 N Type Definition .......................................9
+ 3.1.3 NICKNAME Type Definition ................................9
+ 3.1.4 PHOTO Type Definition ..................................10
+ 3.1.5 BDAY Type Definition ...................................11
+ 3.2 DELIVERY ADDRESSING TYPES .................................11
+ 3.2.1 ADR Type Definition ....................................11
+ 3.2.2 LABEL Type Definition ..................................13
+ 3.3 TELECOMMUNICATIONS ADDRESSING TYPES .......................13
+ 3.3.1 TEL Type Definition ....................................14
+ 3.3.2 EMAIL Type Definition ..................................15
+ 3.3.3 MAILER Type Definition .................................15
+ 3.4 GEOGRAPHICAL TYPES ........................................16
+ 3.4.1 TZ Type Definition .....................................16
+ 3.4.2 GEO Type Definition ....................................16
+ 3.5 ORGANIZATIONAL TYPES ......................................17
+ 3.5.1 TITLE Type Definition ..................................17
+ 3.5.2 ROLE Type Definition ...................................18
+ 3.5.3 LOGO Type Definition ...................................18
+ 3.5.4 AGENT Type Definition ..................................19
+ 3.5.5 ORG Type Definition ....................................20
+ 3.6 EXPLANATORY TYPES .........................................20
+ 3.6.1 CATEGORIES Type Definition .............................20
+ 3.6.2 NOTE Type Definition ...................................21
+ 3.6.3 PRODID Type Definition .................................21
+ 3.6.4 REV Type Definition ....................................22
+ 3.6.5 SORT-STRING Type Definition ............................22
+
+
+
+Dawson & Howes Standards Track [Page 2]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ 3.6.6 SOUND Type Definition ..................................23
+ 3.6.7 UID Type Definition ....................................24
+ 3.6.8 URL Type Definition ....................................25
+ 3.6.9 VERSION Type Definition ................................25
+ 3.7 SECURITY TYPES ............................................25
+ 3.7.1 CLASS Type Definition ..................................26
+ 3.7.2 KEY Type Definition ....................................26
+ 3.8 EXTENDED TYPES ............................................27
+ 4. FORMAL GRAMMAR...............................................27
+ 5. DIFFERENCES FROM VCARD V2.1..................................37
+ 6. ACKNOWLEDGEMENTS.............................................39
+ 7. AUTHORS' ADDRESSES...........................................39
+ 8. SECURITY CONSIDERATIONS......................................39
+ 9. REFERENCES...................................................40
+ 10. FULL COPYRIGHT STATEMENT....................................42
+
+Overview
+
+ The [MIME-DIR] document defines a MIME Content-Type for holding
+ different kinds of directory information. The directory information
+ can be based on any of a number of directory schemas. This document
+ defines a [MIME-DIR] usage profile for conveying directory
+ information based on one such schema; that of the white-pages type of
+ person object.
+
+ The schema is based on the attributes for the person object defined
+ in the X.520 and X.521 directory services recommendations. The schema
+ has augmented the basic attributes defined in the X.500 series
+ recommendation in order to provide for an electronic representation
+ of the information commonly found on a paper business card. This
+ schema was first defined in the [VCARD] document. Hence, this [MIME-
+ DIR] profile is referred to as the vCard MIME Directory Profile.
+
+ A directory entry based on this usage profile can include traditional
+ directory, white-pages information such as the distinguished name
+ used to uniquely identify the entry, a formatted representation of
+ the name used for user-interface or presentation purposes, both the
+ structured and presentation form of the delivery address, various
+ telephone numbers and organizational information associated with the
+ entry. In addition, traditional paper business card information such
+ as an image of an organizational logo or identify photograph can be
+ included in this person object.
+
+ The vCard MIME Directory Profile also provides support for
+ representing other important information about the person associated
+ with the directory entry. For instance, the date of birth of the
+ person; an audio clip describing the pronunciation of the name
+ associated with the directory entry, or some other application of the
+
+
+
+Dawson & Howes Standards Track [Page 3]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ digital sound; longitude and latitude geo-positioning information
+ related to the person associated with the directory entry; date and
+ time that the directory information was last updated; annotations
+ often written on a business card; Uniform Resource Locators (URL) for
+ a website; public key information. The profile also provides support
+ for non-standard extensions to the schema. This provides the
+ flexibility for implementations to augment the current capabilities
+ of the profile in a standardized way. More information about this
+ electronic business card format can be found in [VCARD].
+
+1. The vCard Mime Directory Profile Registration
+
+ This profile is identified by the following [MIME-DIR] registration
+ template information. Subsequent sections define the profile
+ definition.
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME profile VCARD
+
+ Profile name: VCARD
+
+ Profile purpose: To hold person object or white-pages type of
+ directory information. The person schema captured in the directory
+ entries is that commonly found in an electronic business card.
+
+ Predefined MIME Directory value specifications used: uri, date,
+ date-time, float
+
+ New value specifications: This profile places further constraints on
+ the [MIME-DIR] text value specification. In addition, it adds a
+ binary, phone-number, utc-offset and vcard value specifications.
+
+ Predefined MIME Directory types used: SOURCE, NAME, PROFILE, BEGIN,
+ END.
+
+ Predefined MIME Directory parameters used: ENCODING, VALUE, CHARSET,
+ LANGUAGE, CONTEXT.
+
+ New types: FN, N, NICKNAME, PHOTO, BDAY, ADR, LABEL, TEL, EMAIL,
+ MAILER, TZ, GEO, TITLE, ROLE, LOGO, AGENT, ORG, CATEGORIES, NOTE,
+ PRODID, REV, SORT-STRING, SOUND, URL, UID, VERSION, CLASS, KEY
+
+ New parameters: TYPE
+
+ Profile special notes: The vCard object MUST contain the FN, N and
+ VERSION types. The type-grouping feature of [MIME-DIR] is supported
+ by this profile to group related vCard properties about a directory
+
+
+
+Dawson & Howes Standards Track [Page 4]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ entry. For example, vCard properties describing WORK or HOME related
+ characteristics can be grouped with a unique group label.
+
+ The profile permits the use of non-standard types (i.e., those
+ identified with the prefix string "X-") as a flexible method for
+ implementations to extend the functionality currently defined within
+ this profile.
+
+2. MIME Directory Features
+
+ The vCard MIME Directory Profile makes use of many of the features
+ defined by [MIME-DIR]. The following sections either clarify or
+ extend the content-type definition of [MIME-DIR].
+
+2.1 Predefined Type Usage
+
+ The vCard MIME Directory Profile uses the following predefined types
+ from [MIME-DIR].
+
+2.1.1 BEGIN and END Type
+
+ The content entity MUST begin with the BEGIN type with a value of
+ "VCARD". The content entity MUST end with the END type with a value
+ of "VCARD".
+
+2.1.2 NAME Type
+
+ If the NAME type is present, then its value is the displayable,
+ presentation text associated with the source for the vCard, as
+ specified in the SOURCE type.
+
+2.1.3 PROFILE Type
+
+ If the PROFILE type is present, then its value MUST be "VCARD".
+
+2.1.4 SOURCE Type
+
+ If the SOURCE type is present, then its value provides information
+ how to find the source for the vCard.
+
+
+
+
+
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 5]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+2.2 Predefined Type Parameter Usage
+
+ The vCard MIME Directory Profile uses the following predefined type
+ parameters as defined by [MIME-DIR].
+
+ - LANGUAGE
+
+ - ENCODING
+
+ - VALUE
+
+2.3 Predefined VALUE Type Usage
+
+ The predefined data type values specified in [MIME-DIR] MUST NOT be
+ repeated in COMMA separated value lists except within the N,
+ NICKNAME, ADR and CATEGORIES value types.
+
+ The text value type defined in [MIME-DIR] is further restricted such
+ that any SEMI-COLON character (ASCII decimal 59) in the value MUST be
+ escaped with the BACKSLASH character (ASCII decimal 92).
+
+2.4 Extensions To The Predefined VALUE Types
+
+ The predefined data type values specified in [MIME-DIR] have been
+ extended by the vCard profile to include a number of value types that
+ are specific to this profile.
+
+2.4.1 BINARY
+
+ The "binary" value type specifies that the type value is inline,
+ encoded binary data. This value type can be specified in the PHOTO,
+ LOGO, SOUND, and KEY types.
+
+ If inline encoded binary data is specified, the ENCODING type
+ parameter MUST be used to specify the encoding format. The binary
+ data MUST be encoded using the "B" encoding format. Long lines of
+ encoded binary data SHOULD BE folded to 75 characters using the
+ folding method defined in [MIME-DIR].
+
+ The value type is defined by the following notation:
+
+ binary = <A "B" binary encoded string as defined by [RFC 2047].>
+
+2.4.2 VCARD
+
+ The "vcard" value type specifies that the type value is another
+ vCard. This value type can be specified in the AGENT type. The value
+ type is defined by this specification. Since each of the type
+
+
+
+Dawson & Howes Standards Track [Page 6]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ declarations with in the vcard value type are being specified within
+ a text value themselves, they MUST be terminated with the backslash
+ escape sequence "\n" or "\N", instead of the normal newline character
+ sequence CRLF. In addition, any COMMA character (ASCII decimal 44),
+ SEMI-COLON character (ASCII decimal 59) and COLON character (ASCII
+ decimal 58) MUST be escaped with the BACKSLASH character (ASCII
+ decimal 92). For example, with the AGENT type a value would be
+ specified as:
+
+ AGENT:BEGIN:VCARD\nFN:Joe Friday\nTEL:+1-919-555-7878\n
+ TITLE:Area Administrator\, Assistant\n EMAIL\;TYPE=INTERN\n
+ ET:jfriday@host.com\nEND:VCARD\n
+
+2.4.3 PHONE-NUMBER
+
+ The "phone-number" value type specifies that the type value is a
+ telephone number. This value type can be specified in the TEL type.
+ The value type is a text value that has the special semantics of a
+ telephone number as defined in [CCITT E.163] and [CCITT X.121].
+
+2.4.4 UTC-OFFSET
+
+ The "utc-offset" value type specifies that the type value is a signed
+ offset from UTC. This value type can be specified in the TZ type.
+
+ The value type is an offset from Coordinated Universal Time (UTC). It
+ is specified as a positive or negative difference in units of hours
+ and minutes (e.g., +hh:mm). The time is specified as a 24-hour clock.
+ Hour values are from 00 to 23, and minute values are from 00 to 59.
+ Hour and minutes are 2-digits with high order zeroes required to
+ maintain digit count. The extended format for ISO 8601 UTC offsets
+ MUST be used. The extended format makes use of a colon character as a
+ separator of the hour and minute text fields.
+
+ The value is defined by the following notation:
+
+ time-hour = 2DIGIT ;00-23
+ time-minute = 2DIGIT ;00-59
+ utc-offset = ("+" / "-") time-hour ":" time-minute
+
+2.5 Structured Type Values
+
+ Compound type values are delimited by a field delimiter, specified by
+ the SEMI-COLON character (ASCII decimal 59). A SEMI-COLON in a
+ component of a compound property value MUST be escaped with a
+ BACKSLASH character (ASCII decimal 92).
+
+
+
+
+
+Dawson & Howes Standards Track [Page 7]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Lists of values are delimited by a list delimiter, specified by the
+ COMMA character (ASCII decimal 44). A COMMA character in a value MUST
+ be escaped with a BACKSLASH character (ASCII decimal 92).
+
+ This profile supports the type grouping mechanism defined in [MIME-
+ DIR]. Grouping of related types is a useful technique to communicate
+ common semantics concerning the properties of a vCard.
+
+2.6 Line Delimiting and Folding
+
+ This profile supports the same line delimiting and folding methods
+ defined in [MIME-DIR]. Specifically, when parsing a content line,
+ folded lines must first be unfolded according to the unfolding
+ procedure described in [MIME-DIR]. After generating a content line,
+ lines longer than 75 characters SHOULD be folded according to the
+ folding procedure described in [MIME DIR].
+
+ Folding is done after any content encoding of a type value. Unfolding
+ is done before any decoding of a type value in a content line.
+
+3. vCard Profile Features
+
+ The vCard MIME Directory Profile Type contains directory information,
+ typically pertaining to a single directory entry. The information is
+ described using an attribute schema that is tailored for capturing
+ personal contact information. The vCard can include attributes that
+ describe identification, delivery addressing, telecommunications
+ addressing, geographical, organizational, general explanatory and
+ security and access information about the particular object
+ associated with the vCard.
+
+3.1 Identification Types
+
+ These types are used in the vCard profile to capture information
+ associated with the identification and naming of the person or
+ resource associated with the vCard.
+
+3.1.1 FN Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type FN
+
+ Type name:FN
+
+ Type purpose: To specify the formatted text corresponding to the name
+ of the object the vCard represents.
+
+
+
+
+Dawson & Howes Standards Track [Page 8]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: This type is based on the semantics of the X.520
+ Common Name attribute. The property MUST be present in the vCard
+ object.
+
+ Type example:
+
+ FN:Mr. John Q. Public\, Esq.
+
+3.1.2 N Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type N
+
+ Type name: N
+
+ Type purpose: To specify the components of the name of the object the
+ vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single structured text value. Each component can have
+ multiple values.
+
+ Type special note: The structured type value corresponds, in
+ sequence, to the Family Name, Given Name, Additional Names, Honorific
+ Prefixes, and Honorific Suffixes. The text components are separated
+ by the SEMI-COLON character (ASCII decimal 59). Individual text
+ components can include multiple text values (e.g., multiple
+ Additional Names) separated by the COMMA character (ASCII decimal
+ 44). This type is based on the semantics of the X.520 individual name
+ attributes. The property MUST be present in the vCard object.
+
+ Type example:
+
+ N:Public;John;Quinlan;Mr.;Esq.
+
+ N:Stevenson;John;Philip,Paul;Dr.;Jr.,M.D.,A.C.P.
+
+3.1.3 NICKNAME Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type NICKNAME
+
+
+
+Dawson & Howes Standards Track [Page 9]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type name: NICKNAME
+
+ Type purpose: To specify the text corresponding to the nickname of
+ the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: One or more text values separated by a COMMA character
+ (ASCII decimal 44).
+
+ Type special note: The nickname is the descriptive name given instead
+ of or in addition to the one belonging to a person, place, or thing.
+ It can also be used to specify a familiar form of a proper name
+ specified by the FN or N types.
+
+ Type example:
+
+ NICKNAME:Robbie
+
+ NICKNAME:Jim,Jimmie
+
+3.1.4 PHOTO Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type PHOTO
+
+ Type name: PHOTO
+
+ Type purpose: To specify an image or photograph information that
+ annotates some aspect of the object the vCard represents.
+
+ Type encoding: The encoding MUST be reset to "b" using the ENCODING
+ parameter in order to specify inline, encoded binary data. If the
+ value is referenced by a URI value, then the default encoding of 8bit
+ is used and no explicit ENCODING parameter is needed.
+
+ Type value: A single value. The default is binary value. It can also
+ be reset to uri value. The uri value can be used to specify a value
+ outside of this MIME entity.
+
+ Type special notes: The type can include the type parameter "TYPE" to
+ specify the graphic image format type. The TYPE parameter values MUST
+ be one of the IANA registered image formats or a non-standard image
+ format.
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 10]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type example:
+
+ PHOTO;VALUE=uri:http://www.abc.com/pub/photos
+ /jqpublic.gif
+
+
+ PHOTO;ENCODING=b;TYPE=JPEG:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
+ AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
+ ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
+ <...remainder of "B" encoded binary data...>
+
+3.1.5 BDAY Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type BDAY
+
+ Type name: BDAY
+
+ Type purpose: To specify the birth date of the object the vCard
+ represents.
+
+ Type encoding: 8bit
+
+ Type value: The default is a single date value. It can also be reset
+ to a single date-time value.
+
+ Type examples:
+
+ BDAY:1996-04-15
+
+ BDAY:1953-10-15T23:10:00Z
+
+ BDAY:1987-09-27T08:30:00-06:00
+
+3.2 Delivery Addressing Types
+
+ These types are concerned with information related to the delivery
+ addressing or label for the vCard object.
+
+3.2.1 ADR Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type ADR
+
+ Type name: ADR
+
+
+
+
+Dawson & Howes Standards Track [Page 11]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type purpose: To specify the components of the delivery address for
+ the vCard object.
+
+ Type encoding: 8bit
+
+ Type value: A single structured text value, separated by the
+ SEMI-COLON character (ASCII decimal 59).
+
+ Type special notes: The structured type value consists of a sequence
+ of address components. The component values MUST be specified in
+ their corresponding position. The structured type value corresponds,
+ in sequence, to the post office box; the extended address; the street
+ address; the locality (e.g., city); the region (e.g., state or
+ province); the postal code; the country name. When a component value
+ is missing, the associated component separator MUST still be
+ specified.
+
+ The text components are separated by the SEMI-COLON character (ASCII
+ decimal 59). Where it makes semantic sense, individual text
+ components can include multiple text values (e.g., a "street"
+ component with multiple lines) separated by the COMMA character
+ (ASCII decimal 44).
+
+ The type can include the type parameter "TYPE" to specify the
+ delivery address type. The TYPE parameter values can include "dom" to
+ indicate a domestic delivery address; "intl" to indicate an
+ international delivery address; "postal" to indicate a postal
+ delivery address; "parcel" to indicate a parcel delivery address;
+ "home" to indicate a delivery address for a residence; "work" to
+ indicate delivery address for a place of work; and "pref" to indicate
+ the preferred delivery address when more than one address is
+ specified. These type parameter values can be specified as a
+ parameter list (i.e., "TYPE=dom;TYPE=postal") or as a value list
+ (i.e., "TYPE=dom,postal"). This type is based on semantics of the
+ X.520 geographical and postal addressing attributes. The default is
+ "TYPE=intl,postal,parcel,work". The default can be overridden to some
+ other set of values by specifying one or more alternate values. For
+ example, the default can be reset to "TYPE=dom,postal,work,home" to
+ specify a domestic delivery address for postal delivery to a
+ residence that is also used for work.
+
+ Type example: In this example the post office box and the extended
+ address are absent.
+
+ ADR;TYPE=dom,home,postal,parcel:;;123 Main
+ Street;Any Town;CA;91921-1234
+
+
+
+
+
+Dawson & Howes Standards Track [Page 12]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+3.2.2 LABEL Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type LABEL
+
+ Type name: LABEL
+
+ Type purpose: To specify the formatted text corresponding to delivery
+ address of the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: The type value is formatted text that can be used
+ to present a delivery address label for the vCard object. The type
+ can include the type parameter "TYPE" to specify delivery label type.
+ The TYPE parameter values can include "dom" to indicate a domestic
+ delivery label; "intl" to indicate an international delivery label;
+ "postal" to indicate a postal delivery label; "parcel" to indicate a
+ parcel delivery label; "home" to indicate a delivery label for a
+ residence; "work" to indicate delivery label for a place of work; and
+ "pref" to indicate the preferred delivery label when more than one
+ label is specified. These type parameter values can be specified as a
+ parameter list (i.e., "TYPE=dom;TYPE=postal") or as a value list
+ (i.e., "TYPE=dom,postal"). This type is based on semantics of the
+ X.520 geographical and postal addressing attributes. The default is
+ "TYPE=intl,postal,parcel,work". The default can be overridden to some
+ other set of values by specifying one or more alternate values. For
+ example, the default can be reset to "TYPE=intl,post,parcel,home" to
+ specify an international delivery label for both postal and parcel
+ delivery to a residential location.
+
+ Type example: A multi-line address label.
+
+ LABEL;TYPE=dom,home,postal,parcel:Mr.John Q. Public\, Esq.\n
+ Mail Drop: TNE QB\n123 Main Street\nAny Town\, CA 91921-1234
+ \nU.S.A.
+
+3.3 Telecommunications Addressing Types
+
+ These types are concerned with information associated with the
+ telecommunications addressing of the object the vCard represents.
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 13]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+3.3.1 TEL Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type TEL
+
+ Type name: TEL
+
+ Type purpose: To specify the telephone number for telephony
+ communication with the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single phone-number value.
+
+ Type special notes: The value of this type is specified in a
+ canonical form in order to specify an unambiguous representation of
+ the globally unique telephone endpoint. This type is based on the
+ X.500 Telephone Number attribute.
+
+ The type can include the type parameter "TYPE" to specify intended
+ use for the telephone number. The TYPE parameter values can include:
+ "home" to indicate a telephone number associated with a residence,
+ "msg" to indicate the telephone number has voice messaging support,
+ "work" to indicate a telephone number associated with a place of
+ work, "pref" to indicate a preferred-use telephone number, "voice" to
+ indicate a voice telephone number, "fax" to indicate a facsimile
+ telephone number, "cell" to indicate a cellular telephone number,
+ "video" to indicate a video conferencing telephone number, "pager" to
+ indicate a paging device telephone number, "bbs" to indicate a
+ bulletin board system telephone number, "modem" to indicate a MODEM
+ connected telephone number, "car" to indicate a car-phone telephone
+ number, "isdn" to indicate an ISDN service telephone number, "pcs" to
+ indicate a personal communication services telephone number. The
+ default type is "voice". These type parameter values can be specified
+ as a parameter list (i.e., "TYPE=work;TYPE=voice") or as a value list
+ (i.e., "TYPE=work,voice"). The default can be overridden to another
+ set of values by specifying one or more alternate values. For
+ example, the default TYPE of "voice" can be reset to a WORK and HOME,
+ VOICE and FAX telephone number by the value list
+ "TYPE=work,home,voice,fax".
+
+ Type example:
+
+ TEL;TYPE=work,voice,pref,msg:+1-213-555-1234
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 14]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+3.3.2 EMAIL Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type EMAIL
+
+ Type name: EMAIL
+
+ Type purpose: To specify the electronic mail address for
+ communication with the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: The type can include the type parameter "TYPE" to
+ specify the format or preference of the electronic mail address. The
+ TYPE parameter values can include: "internet" to indicate an Internet
+ addressing type, "x400" to indicate a X.400 addressing type or "pref"
+ to indicate a preferred-use email address when more than one is
+ specified. Another IANA registered address type can also be
+ specified. The default email type is "internet". A non-standard value
+ can also be specified.
+
+ Type example:
+
+ EMAIL;TYPE=internet:jqpublic@xyz.dom1.com
+
+ EMAIL;TYPE=internet:jdoe@isp.net
+
+ EMAIL;TYPE=internet,pref:jane_doe@abc.com
+
+3.3.3 MAILER Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type MAILER
+
+ Type name: MAILER
+
+ Type purpose: To specify the type of electronic mail software that is
+ used by the individual associated with the vCard.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+
+
+
+
+Dawson & Howes Standards Track [Page 15]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type special notes: This information can provide assistance to a
+ correspondent regarding the type of data representation which can be
+ used, and how they can be packaged. This property is based on the
+ private MIME type X-Mailer that is generally implemented by MIME user
+ agent products.
+
+ Type example:
+
+ MAILER:PigeonMail 2.1
+
+3.4 Geographical Types
+
+ These types are concerned with information associated with
+ geographical positions or regions associated with the object the
+ vCard represents.
+
+3.4.1 TZ Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type TZ
+
+ Type name: TZ
+
+ Type purpose: To specify information related to the time zone of the
+ object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: The default is a single utc-offset value. It can also be
+ reset to a single text value.
+
+ Type special notes: The type value consists of a single value.
+
+ Type examples:
+
+ TZ:-05:00
+
+ TZ;VALUE=text:-05:00; EST; Raleigh/North America
+ ;This example has a single value, not a structure text value.
+
+3.4.2 GEO Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type GEO
+
+ Type name: GEO
+
+
+
+Dawson & Howes Standards Track [Page 16]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type purpose: To specify information related to the global
+ positioning of the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single structured value consisting of two float values
+ separated by the SEMI-COLON character (ASCII decimal 59).
+
+ Type special notes: This type specifies information related to the
+ global position of the object associated with the vCard. The value
+ specifies latitude and longitude, in that order (i.e., "LAT LON"
+ ordering). The longitude represents the location east and west of the
+ prime meridian as a positive or negative real number, respectively.
+ The latitude represents the location north and south of the equator
+ as a positive or negative real number, respectively. The longitude
+ and latitude values MUST be specified as decimal degrees and should
+ be specified to six decimal places. This will allow for granularity
+ within a meter of the geographical position. The text components are
+ separated by the SEMI-COLON character (ASCII decimal 59). The simple
+ formula for converting degrees-minutes-seconds into decimal degrees
+ is:
+
+ decimal = degrees + minutes/60 + seconds/3600.
+
+ Type example:
+
+ GEO:37.386013;-122.082932
+
+3.5 Organizational Types
+
+ These types are concerned with information associated with
+ characteristics of the organization or organizational units of the
+ object the vCard represents.
+
+3.5.1 TITLE Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type TITLE
+
+ Type name: TITLE
+
+ Type purpose: To specify the job title, functional position or
+ function of the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+
+
+Dawson & Howes Standards Track [Page 17]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type special notes: This type is based on the X.520 Title attribute.
+
+ Type example:
+
+ TITLE:Director\, Research and Development
+
+3.5.2 ROLE Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type ROLE
+
+ Type name: ROLE
+
+ Type purpose: To specify information concerning the role, occupation,
+ or business category of the object the vCard represents.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: This type is based on the X.520 Business Category
+ explanatory attribute. This property is included as an organizational
+ type to avoid confusion with the semantics of the TITLE type and
+ incorrect usage of that type when the semantics of this type is
+ intended.
+
+ Type example:
+
+ ROLE:Programmer
+
+3.5.3 LOGO Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type LOGO
+
+ Type name: LOGO
+
+ Type purpose: To specify a graphic image of a logo associated with
+ the object the vCard represents.
+
+ Type encoding: The encoding MUST be reset to "b" using the ENCODING
+ parameter in order to specify inline, encoded binary data. If the
+ value is referenced by a URI value, then the default encoding of 8bit
+ is used and no explicit ENCODING parameter is needed.
+
+
+
+
+
+Dawson & Howes Standards Track [Page 18]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type value: A single value. The default is binary value. It can also
+ be reset to uri value. The uri value can be used to specify a value
+ outside of this MIME entity.
+
+ Type special notes: The type can include the type parameter "TYPE" to
+ specify the graphic image format type. The TYPE parameter values MUST
+ be one of the IANA registered image formats or a non-standard image
+ format.
+
+ Type example:
+
+ LOGO;VALUE=uri:http://www.abc.com/pub/logos/abccorp.jpg
+
+ LOGO;ENCODING=b;TYPE=JPEG:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
+ AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
+ ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
+ <...the remainder of "B" encoded binary data...>
+
+3.5.4 AGENT Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type AGENT
+
+ Type name: AGENT
+
+ Type purpose: To specify information about another person who will
+ act on behalf of the individual or resource associated with the
+ vCard.
+
+ Type encoding: 8-bit
+
+ Type value: The default is a single vcard value. It can also be reset
+ to either a single text or uri value. The text value can be used to
+ specify textual information. The uri value can be used to specify
+ information outside of this MIME entity.
+
+ Type special notes: This type typically is used to specify an area
+ administrator, assistant, or secretary for the individual associated
+ with the vCard. A key characteristic of the Agent type is that it
+ represents somebody or something that is separately addressable.
+
+ Type example:
+
+ AGENT;VALUE=uri:
+ CID:JQPUBLIC.part3.960129T083020.xyzMail@host3.com
+
+
+
+
+
+Dawson & Howes Standards Track [Page 19]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ AGENT:BEGIN:VCARD\nFN:Susan Thomas\nTEL:+1-919-555-
+ 1234\nEMAIL\;INTERNET:sthomas@host.com\nEND:VCARD\n
+
+3.5.5 ORG Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type ORG
+
+ Type name: ORG
+
+ Type purpose: To specify the organizational name and units associated
+ with the vCard.
+
+ Type encoding: 8bit
+
+ Type value: A single structured text value consisting of components
+ separated the SEMI-COLON character (ASCII decimal 59).
+
+ Type special notes: The type is based on the X.520 Organization Name
+ and Organization Unit attributes. The type value is a structured type
+ consisting of the organization name, followed by one or more levels
+ of organizational unit names.
+
+ Type example: A type value consisting of an organizational name,
+ organizational unit #1 name and organizational unit #2 name.
+
+ ORG:ABC\, Inc.;North American Division;Marketing
+
+3.6 Explanatory Types
+
+ These types are concerned with additional explanations, such as that
+ related to informational notes or revisions specific to the vCard.
+
+3.6.1 CATEGORIES Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type CATEGORIES
+
+ Type name: CATEGORIES
+
+ Type purpose: To specify application category information about the
+ vCard.
+
+ Type encoding: 8bit
+
+
+
+
+
+Dawson & Howes Standards Track [Page 20]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type value: One or more text values separated by a COMMA character
+ (ASCII decimal 44).
+
+ Type example:
+
+ CATEGORIES:TRAVEL AGENT
+
+ CATEGORIES:INTERNET,IETF,INDUSTRY,INFORMATION TECHNOLOGY
+
+3.6.2 NOTE Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type NOTE
+
+ Type name: NOTE
+
+ Type purpose: To specify supplemental information or a comment that
+ is associated with the vCard.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: The type is based on the X.520 Description
+ attribute.
+
+ Type example:
+
+ NOTE:This fax number is operational 0800 to 1715
+ EST\, Mon-Fri.
+
+3.6.3 PRODID Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type PRODID
+
+ Type name: PRODID
+
+ Type purpose: To specify the identifier for the product that created
+ the vCard object.
+
+ Type encoding: 8-bit
+
+ Type value: A single text value.
+
+
+
+
+
+Dawson & Howes Standards Track [Page 21]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type special notes: Implementations SHOULD use a method such as that
+ specified for Formal Public Identifiers in ISO 9070 to assure that
+ the text value is unique.
+
+ Type example:
+
+ PRODID:-//ONLINE DIRECTORY//NONSGML Version 1//EN
+
+3.6.4 REV Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type REV
+
+ Type name: REV
+
+ Type purpose: To specify revision information about the current
+ vCard.
+
+ Type encoding: 8-bit
+
+ Type value: The default is a single date-time value. Can also be
+ reset to a single date value.
+
+ Type special notes: The value distinguishes the current revision of
+ the information in this vCard for other renditions of the
+ information.
+
+ Type example:
+
+ REV:1995-10-31T22:27:10Z
+
+ REV:1997-11-15
+
+3.6.5 SORT-STRING Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type SORT-STRING
+
+ Type Name: SORT-STRING
+
+ Type purpose: To specify the family name or given name text to be
+ used for national-language-specific sorting of the FN and N types.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+
+
+Dawson & Howes Standards Track [Page 22]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type special notes: The sort string is used to provide family name or
+ given name text that is to be used in locale- or national-language-
+ specific sorting of the formatted name and structured name types.
+ Without this information, sorting algorithms could incorrectly sort
+ this vCard within a sequence of sorted vCards. When this type is
+ present in a vCard, then this family name or given name value is used
+ for sorting the vCard.
+
+ Type examples: For the case of family name sorting, the following
+ examples define common sort string usage with the FN and N types.
+
+ FN:Rene van der Harten
+ N:van der Harten;Rene;J.;Sir;R.D.O.N.
+ SORT-STRING:Harten
+
+ FN:Robert Pau Shou Chang
+ N:Pau;Shou Chang;Robert
+ SORT-STRING:Pau
+
+ FN:Osamu Koura
+ N:Koura;Osamu
+ SORT-STRING:Koura
+
+ FN:Oscar del Pozo
+ N:del Pozo Triscon;Oscar
+ SORT-STRING:Pozo
+
+ FN:Chistine d'Aboville
+ N:d'Aboville;Christine
+ SORT-STRING:Aboville
+
+3.6.6 SOUND Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type SOUND
+
+ Type name: SOUND
+
+ Type purpose: To specify a digital sound content information that
+ annotates some aspect of the vCard. By default this type is used to
+ specify the proper pronunciation of the name type value of the vCard.
+
+ Type encoding: The encoding MUST be reset to "b" using the ENCODING
+ parameter in order to specify inline, encoded binary data. If the
+ value is referenced by a URI value, then the default encoding of 8bit
+ is used and no explicit ENCODING parameter is needed.
+
+
+
+
+Dawson & Howes Standards Track [Page 23]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type value: A single value. The default is binary value. It can also
+ be reset to uri value. The uri value can be used to specify a value
+ outside of this MIME entity.
+
+ Type special notes: The type can include the type parameter "TYPE" to
+ specify the audio format type. The TYPE parameter values MUST be one
+ of the IANA registered audio formats or a non-standard audio format.
+
+ Type example:
+
+ SOUND;TYPE=BASIC;VALUE=uri:CID:JOHNQPUBLIC.part8.
+ 19960229T080000.xyzMail@host1.com
+
+ SOUND;TYPE=BASIC;ENCODING=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcN
+ AQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bm
+ ljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
+ <...the remainder of "B" encoded binary data...>
+
+3.6.7 UID Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type UID
+
+ Type name: UID
+
+ Type purpose: To specify a value that represents a globally unique
+ identifier corresponding to the individual or resource associated
+ with the vCard.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: The type is used to uniquely identify the object
+ that the vCard represents.
+
+ The type can include the type parameter "TYPE" to specify the format
+ of the identifier. The TYPE parameter value should be an IANA
+ registered identifier format. The value can also be a non-standard
+ format.
+
+ Type example:
+
+ UID:19950401-080045-40000F192713-0052
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 24]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+3.6.8 URL Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type URL
+
+ Type name: URL
+
+ Type purpose: To specify a uniform resource locator associated with
+ the object that the vCard refers to.
+
+ Type encoding: 8bit
+
+ Type value: A single uri value.
+
+ Type example:
+
+ URL:http://www.swbyps.restaurant.french/~chezchic.html
+
+3.6.9 VERSION Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type VERSION
+
+ Type name: VERSION
+
+ Type purpose: To specify the version of the vCard specification used
+ to format this vCard.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: The property MUST be present in the vCard object.
+ The value MUST be "3.0" if the vCard corresponds to this
+ specification.
+
+ Type example:
+
+ VERSION:3.0
+
+3.7 Security Types
+
+ These types are concerned with the security of communication pathways
+ or access to the vCard.
+
+
+
+
+
+Dawson & Howes Standards Track [Page 25]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+3.7.1 CLASS Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type CLASS
+
+ Type name: CLASS
+
+ Type purpose: To specify the access classification for a vCard
+ object.
+
+ Type encoding: 8bit
+
+ Type value: A single text value.
+
+ Type special notes: An access classification is only one component of
+ the general security model for a directory service. The
+ classification attribute provides a method of capturing the intent of
+ the owner for general access to information described by the vCard
+ object.
+
+ Type examples:
+
+ CLASS:PUBLIC
+
+ CLASS:PRIVATE
+
+ CLASS:CONFIDENTIAL
+
+3.7.2 KEY Type Definition
+
+ To: ietf-mime-directory@imc.org
+
+ Subject: Registration of text/directory MIME type KEY
+
+ Type name: KEY
+
+ Type purpose: To specify a public key or authentication certificate
+ associated with the object that the vCard represents.
+
+ Type encoding: The encoding MUST be reset to "b" using the ENCODING
+ parameter in order to specify inline, encoded binary data. If the
+ value is a text value, then the default encoding of 8bit is used and
+ no explicit ENCODING parameter is needed.
+
+ Type value: A single value. The default is binary. It can also be
+ reset to text value. The text value can be used to specify a text
+ key.
+
+
+
+Dawson & Howes Standards Track [Page 26]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ Type special notes: The type can also include the type parameter TYPE
+ to specify the public key or authentication certificate format. The
+ parameter type should specify an IANA registered public key or
+ authentication certificate format. The parameter type can also
+ specify a non-standard format.
+
+ Type example:
+
+ KEY;ENCODING=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQA
+ wdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENbW11bmljYX
+ Rpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZvcm1hdGlvbiBTeXN0
+ ZW1zMRwwGgYDVQQDExNyb290Y2EubmV0c2NhcGUuY29tMB4XDTk3MDYwNj
+ E5NDc1OVoXDTk3MTIwMzE5NDc1OVowgYkxCzAJBgNVBAYTAlVTMSYwJAYD
+ VQQKEx1OZXRzY2FwZSBDb21tdW5pY2F0aW9ucyBDb3JwLjEYMBYGA1UEAx
+ MPVGltb3RoeSBBIEhvd2VzMSEwHwYJKoZIhvcNAQkBFhJob3dlc0BuZXRz
+ Y2FwZS5jb20xFTATBgoJkiaJk/IsZAEBEwVob3dlczBcMA0GCSqGSIb3DQ
+ EBAQUAA0sAMEgCQQC0JZf6wkg8pLMXHHCUvMfL5H6zjSk4vTTXZpYyrdN2
+ dXcoX49LKiOmgeJSzoiFKHtLOIboyludF90CgqcxtwKnAgMBAAGjNjA0MB
+ EGCWCGSAGG+EIBAQQEAwIAoDAfBgNVHSMEGDAWgBT84FToB/GV3jr3mcau
+ +hUMbsQukjANBgkqhkiG9w0BAQQFAAOBgQBexv7o7mi3PLXadkmNP9LcIP
+ mx93HGp0Kgyx1jIVMyNgsemeAwBM+MSlhMfcpbTrONwNjZYW8vJDSoi//y
+ rZlVt9bJbs7MNYZVsyF1unsqaln4/vy6Uawfg8VUMk1U7jt8LYpo4YULU7
+ UZHPYVUaSgVttImOHZIKi4hlPXBOhcUQ==
+
+3.8 Extended Types
+
+ The types defined by this document can be extended with private types
+ using the non-standard, private values mechanism defined in [RFC
+ 2045]. Non-standard, private types with a name starting with "X-" may
+ be defined bilaterally between two cooperating agents without outside
+ registration or standardization.
+
+4. Formal Grammar
+
+ The following formal grammar is provided to assist developers in
+ building parsers for the vCard.
+
+ This syntax is written according to the form described in RFC 2234,
+ but it references just this small subset of RFC 2234 literals:
+
+ ;*******************************************
+ ; Commonly Used Literal Definition
+ ;*******************************************
+
+ ALPHA = %x41-5A / %x61-7A
+ ; Latin Capital Letter A-Latin Capital Letter Z /
+ ; Latin Small Letter a-Latin Small Letter z
+
+
+
+
+Dawson & Howes Standards Track [Page 27]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ CHAR = %x01-7F
+ ; Any C0 Controls and Basic Latin, excluding NULL from
+ ; Code Charts, pages 7-6 through 7-9 in [UNICODE]
+
+ CR = %x0D
+ ; Carriage Return
+
+ LF = %0A
+ ; Line Feed
+
+ CRLF = CR LF
+ ; Internet standard newline
+
+ ;CTL = %x00-1F / %x7F
+ ; Controls. Not used, but referenced in comments.
+
+ DIGIT = %x30-39
+ ; Digit Zero-Digit Nine
+
+ DQUOTE = %x22
+ ; Quotation Mark
+
+ HTAB = %x09
+ ; Horizontal Tabulation
+
+ SP = %x20
+ ; space
+
+ VCHAR = %x21-7E
+ ; Visible (printing) characters
+
+ WSP = SP / HTAB
+ ; White Space
+
+ ;*******************************************
+ ; Basic vCard Definition
+ ;*******************************************
+
+ vcard_entity = 1*(vcard)
+
+ vcard = [group "."] "BEGIN" ":" "VCARD" 1*CRLF
+ 1*(contentline)
+ ;A vCard object MUST include the VERSION, FN and N types.
+ [group "."] "END" ":" "VCARD" 1*CRLF
+
+ contentline = [group "."] name *(";" param ) ":" value CRLF
+ ; When parsing a content line, folded lines must first
+ ; be unfolded according to the unfolding procedure
+
+
+
+Dawson & Howes Standards Track [Page 28]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ ; described above. When generating a content line, lines
+ ; longer than 75 characters SHOULD be folded according to
+ ; the folding procedure described in [MIME DIR].
+
+ group = 1*(ALPHA / DIGIT / "-")
+
+ name = iana-token / x-name
+ ; Parsing of the param and value is
+ ; based on the "name" or type identifier
+ ; as defined in ABNF sections below
+
+ iana-token = 1*(ALPHA / DIGIT / "-")
+ ; vCard type or parameter identifier registered with IANA
+
+ x-name = "X-" 1*(ALPHA / DIGIT / "-")
+ ; Reserved for non-standard use
+
+ param = param-name "=" param-value *("," param-value)
+
+ param-name = iana-token / x-name
+
+ param-value = ptext / quoted-string
+
+ ptext = *SAFE-CHAR
+
+ value = *VALUE-CHAR
+
+ quoted-string = DQUOTE QSAFE-CHAR DQUOTE
+
+ NON-ASCII = %x80-FF
+ ; Use is restricted by CHARSET parameter
+ ; on outer MIME object (UTF-8 preferred)
+
+ QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-ASCII
+ ; Any character except CTLs, DQUOTE
+
+ SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-ASCII
+ ; Any character except CTLs, DQUOTE, ";", ":", ","
+
+ VALUE-CHAR = WSP / VCHAR / NON-ASCII
+ ; Any textual character
+
+ ;*******************************************
+ ; vCard Type Definition
+ ;
+ ; Provides type-specific definitions for how the
+ ; "value" and "param" are defined.
+ ;*******************************************
+
+
+
+Dawson & Howes Standards Track [Page 29]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ ;For name="NAME"
+ param = ""
+ ; No parameters allowed
+
+ value = text-value
+
+ ;For name="PROFILE"
+ param = ""
+ ; No parameters allowed
+
+ value = text-value
+ ; Value MUST be the case insensitive value "VCARD
+
+ ;For name="SOURCE"
+ param = source-param
+ ; No parameters allowed
+
+ value = uri
+
+ source-param = ("VALUE" "=" "uri")
+ / ("CONTEXT" "=" "word")
+ ; Parameter value specifies the protocol context
+ ; for the uri value.
+ / (x-name "=" *SAFE-CHAR)
+
+ ;For name="FN"
+ ;This type MUST be included in a vCard object.
+ param = text-param
+ ; Text parameters allowed
+
+ value = text-value
+
+ ;For name="N"
+ ;This type MUST be included in a vCard object.
+
+ param = text-param
+ ; Text parameters allowed
+
+ value = n-value
+
+ n-value = 0*4(text-value *("," text-value) ";")
+ text-value *("," text-value)
+ ; Family; Given; Middle; Prefix; Suffix.
+ ; Example: Public;John;Quincy,Adams;Reverend Dr. III
+
+ ;For name="NICKNAME"
+ param = text-param
+ ; Text parameters allowed
+
+
+
+Dawson & Howes Standards Track [Page 30]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ value = text-list
+
+ ;For name="PHOTO"
+ param = img-inline-param
+ ; Only image parameters allowed
+
+ param =/ img-refer-param
+ ; Only image parameters allowed
+
+ value = img-inline-value
+ ; Value and parameter MUST match
+
+ value =/ img-refer-value
+ ; Value and parameter MUST match
+
+ ;For name="BDAY"
+ param = ("VALUE" "=" "date")
+ ; Only value parameter allowed
+
+ param =/ ("VALUE" "=" "date-time")
+ ; Only value parameter allowed
+
+ value = date-value
+ ; Value MUST match value type
+
+ value =/ date-time-value
+ ; Value MUST match value type
+
+ ;For name="ADR"
+ param = adr-param / text-param
+ ; Only adr and text parameters allowed
+
+ value = adr-value
+
+ ;For name="LABEL"
+ param = adr-param / text-param
+ ; Only adr and text parameters allowed
+
+ value = text-value
+
+ ;For name="TEL"
+ param = tel-param
+ ; Only tel parameters allowed
+
+ value = phone-number-value
+
+ tel-param = "TYPE" "=" tel-type *("," tel-type)
+
+
+
+
+Dawson & Howes Standards Track [Page 31]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ tel-type = "HOME" / "WORK" / "PREF" / "VOICE" / "FAX" / "MSG"
+ / "CELL" / "PAGER" / "BBS" / "MODEM" / "CAR" / "ISDN"
+ / "VIDEO" / "PCS" / iana-token / x-name
+ ; Values are case insensitive
+
+ ;For name="EMAIL"
+ param = email-param
+ ; Only email parameters allowed
+
+ value = text-value
+
+ email-param = "TYPE" "=" email-type ["," "PREF"]
+ ; Value is case insensitive
+
+ email-type = "INTERNET" / "X400" / iana-token / "X-" word
+ ; Values are case insensitive
+
+ ;For name="MAILER"
+ param = text-param
+ ; Only text parameters allowed
+
+ value = text-value
+
+ ;For name="TZ"
+ param = ""
+ ; No parameters allowed
+
+ value = utc-offset-value
+
+ ;For name="GEO"
+ param = ""
+ ; No parameters allowed
+
+ value = float-value ";" float-value
+
+ ;For name="TITLE"
+ param = text-param
+ ; Only text parameters allowed
+
+ value = text-value
+
+ ;For name="ROLE"
+ param = text-param
+ ; Only text parameters allowed
+
+ value = text-value
+
+ ;For name="LOGO"
+
+
+
+Dawson & Howes Standards Track [Page 32]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ param = img-inline-param / img-refer-param
+ ; Only image parameters allowed
+
+ value = img-inline-value / img-refer-value
+ ; Value and parameter MUST match
+
+ ;For name="AGENT"
+ param = agent-inline-param
+
+ param =/ agent-refer-param
+
+ value = agent-inline-value
+ ; Value and parameter MUST match
+
+ value =/ agent-refer-value
+ ; Value and parameter MUST match
+
+ agent-inline-param = ""
+ ; No parameters allowed
+
+ agent-refer-param = "VALUE" "=" "uri"
+ ; Only value parameter allowed
+
+ agent-inline-value = text-value
+ ; Value MUST be a valid vCard object
+
+ agent-refer-value = uri
+ ; URI MUST refer to image content of given type
+
+ ;For name="ORG"
+
+ param = text-param
+ ; Only text parameters allowed
+
+ value = org-value
+
+ org-value = *(text-value ";") text-value
+ ; First is Organization Name, remainder are Organization Units.
+
+ ;For name="CATEGORIES"
+ param = text-param
+ ; Only text parameters allowed
+
+ value = text-list
+
+ ;For name="NOTE"
+ param = text-param
+ ; Only text parameters allowed
+
+
+
+Dawson & Howes Standards Track [Page 33]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ value = text-value
+
+ ;For name="PRODID"
+ param = ""
+ ; No parameters allowed
+
+ value = text-value
+
+ ;For name="REV"
+ param = ["VALUE" =" "date-time"]
+ ; Only value parameters allowed. Values are case insensitive.
+
+ param =/ "VALUE" =" "date"
+ ; Only value parameters allowed. Values are case insensitive.
+
+ value = date-time-value
+
+ value =/ date-value
+
+ ;For name="SORT-STRING"
+ param = text-param
+ ; Only text parameters allowed
+
+ value = text-value
+
+ ;For name="SOUND"
+ param = snd-inline-param
+ ; Only sound parameters allowed
+
+ param =/ snd-refer-param
+ ; Only sound parameters allowed
+
+ value = snd-line-value
+ ; Value MUST match value type
+
+ value =/ snd-refer-value
+ ; Value MUST match value type
+
+ snd-inline-value = binary-value CRLF
+ ; Value MUST be "b" encoded audio content
+
+ snd-inline-param = ("VALUE" "=" "binary"])
+ / ("ENCODING" "=" "b")
+ / ("TYPE" "=" *SAFE-CHAR)
+ ; Value MUST be an IANA registered audio type
+
+ snd-refer-value = uri
+ ; URI MUST refer to audio content of given type
+
+
+
+Dawson & Howes Standards Track [Page 34]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ snd-refer-param = ("VALUE" "=" "uri")
+ / ("TYPE" "=" word)
+ ; Value MUST be an IANA registered audio type
+
+ ;For name="UID"
+ param = ""
+ ; No parameters allowed
+
+ value = text-value
+
+ ;For name="URL"
+ param = ""
+ ; No parameters allowed
+
+ value = uri
+
+ ;For name="VERSION"
+ ;This type MUST be included in a vCard object.
+ param = ""
+ ; No parameters allowed
+
+ value = text-value
+ ; Value MUST be "3.0"
+
+ ;For name="CLASS"
+ param = ""
+ ; No parameters allowed
+
+ value = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL"
+ / iana-token / x-name
+ ; Value are case insensitive
+
+ ;For name="KEY"
+ param = key-txt-param
+ ; Only value and type parameters allowed
+
+ param =/ key-bin-param
+ ; Only value and type parameters allowed
+
+ value = text-value
+
+ value =/ binary-value
+
+ key-txt-param = "TYPE" "=" keytype
+
+ key-bin-param = ("TYPE" "=" keytype)
+ / ("ENCODING" "=" "b")
+ ; Value MUST be a "b" encoded key or certificate
+
+
+
+Dawson & Howes Standards Track [Page 35]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ keytype = "X509" / "PGP" / iana-token / x-name
+ ; Values are case insensitive
+
+ ;For name="X-" non-standard type
+ param = text-param / (x-name "=" param-value)
+ ; Only text or non-standard parameters allowed
+
+ value = text-value
+
+ ;*******************************************
+ ; vCard Commonly Used Parameter Definition
+ ;*******************************************
+
+ text-param = ("VALUE" "=" "ptext")
+ / ("LANGUAGE" "=" langval)
+ / (x-name "=" param-value)
+
+ langval = <a language string as defined in RFC 1766>
+
+ img-inline-value = binary-value
+ ;Value MUST be "b" encoded image content
+
+ img-inline-param
+
+ img-inline-param = ("VALUE" "=" "binary")
+ / ("ENCODING" "=" "b")
+ / ("TYPE" "=" param-value
+ ;TYPE value MUST be an IANA registered image type
+
+ img-refer-value = uri
+ ;URI MUST refer to image content of given type
+
+ img-refer-param = ("VALUE" "=" "uri")
+ / ("TYPE" "=" param-value)
+ ;TYPE value MUST be an IANA registered image type
+
+ adr-param = ("TYPE" "=" adr-type *("," adr-type))
+ / (text-param)
+
+ adr-type = "dom" / "intl" / "postal" / "parcel" / "home"
+ / "work" / "pref" / iana-type / x-name
+
+ adr-value = 0*6(text-value ";") text-value
+ ; PO Box, Extended Address, Street, Locality, Region, Postal
+ ; Code, Country Name
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 36]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ ;*******************************************
+ ; vCard Type Value Definition
+ ;*******************************************
+
+ text-value-list = 1*text-value *("," 1*text-value)
+
+ text-value = *(SAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
+
+ ESCAPED-CHAR = "\\" / "\;" / "\," / "\n" / "\N")
+ ; \\ encodes \, \n or \N encodes newline
+ ; \; encodes ;, \, encodes ,
+
+ binary-value = <A "b" encoded text value as defined in [RFC 2047]>
+
+ date-value = <A single date value as defined in [MIME-DIR]>
+
+ time-value = <A single time value as defined in [MIME-DIR]>
+
+ date-time-value = <A single date-time value as defined in [MIME-DIR]
+
+ float-value = <A single float value as defined in [MIME-DIR]>
+
+ phone-number-value = <A single text value as defined in [CCITT
+ E.163] and [CCITT X.121]>
+
+ uri-value = <A uri value as defined in [MIME-DIR]>
+
+ utc-offset-value = ("+" / "-") time-hour ":" time-minute
+ time-hour = 2DIGIT ;00-23
+ time-minute = 2DIGIT ;00-59
+
+5. Differences From vCard v2.1
+
+ This specification has been reviewed by the IETF community. The
+ review process introduced a number of differences from the [VCARD]
+ version 2.1. These differences require that vCard objects conforming
+ to this specification have a different version number than a vCard
+ conforming to [VCARD]. The differences include the following:
+
+ . The QUOTED-PRINTABLE inline encoding has been eliminated.
+ Only the "B" encoding of [RFC 2047] is an allowed value for
+ the ENCODING parameter.
+
+ . The method for specifying CRLF character sequences in text
+ type values has been changed. The CRLF character sequence in
+ a text type value is specified with the backslash character
+ sequence "\n" or "\N".
+
+
+
+
+Dawson & Howes Standards Track [Page 37]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ . Any COMMA or SEMICOLON in a text type value must be backslash
+ escaped.
+
+ . VERSION value corresponding to this specification MUST be
+ "3.0".
+
+ . The [MIME-DIR] predefined types of SOURCE, NAME and PROFILE
+ are allowed.
+
+ . The [MIME-DIR] VALUE type parameter for value data typing is
+ allowed. In addition, there are extensions made to these type
+ values for additional value types used in this specification.
+
+ . The [VCARD] CHARSET type parameter has been eliminated.
+ Character set can only be specified on the CHARSET parameter
+ on the Content-Type MIME header field.
+
+ . The [VCARD] support for non-significant WSP character has
+ been eliminated.
+
+ . The "TYPE=" prefix to parameter values is required. In
+ [VCARD] this was optional.
+
+ . LOGO, PHOTO and SOUND multimedia formats MUST be either IANA
+ registered types or non-standard types.
+
+ . Inline binary content must be "B" encoded and folded. A blank
+ line after the encoded binary content is no longer required.
+
+ . TEL values can be identified as personal communication
+ services telephone numbers with the PCS type parameter value.
+
+ . The CATEGORIES, CLASS, NICKNAME, PRODID and SORT-STRING types
+ have been added.
+
+ . The VERSION, N and FN types MUST be specified in a vCard.
+ This identifies the version of the specification that the
+ object was formatted to. It also assures that every vCard
+ will include both a structured and formatted name that can be
+ used to identify the object.
+
+
+
+
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 38]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+6. Acknowledgements
+
+ The many valuable comments contributed by members of the IETF ASID
+ working group are gratefully acknowledged, as are the contributions
+ by Roland Alden, Stephen Bartlett, Alec Dun, Patrik Faltstrom, Daniel
+ Gurney, Bruce Johnston, Daniel Klaussen, Pete Miller, Keith Moore,
+ Vinod Seraphin, Michelle Watkins. Chris Newman was especially helpful
+ in navigating the intricacies of ABNF lore.
+
+7. Authors' Addresses
+
+ BEGIN:vCard
+ VERSION:3.0
+ FN:Frank Dawson
+ ORG:Lotus Development Corporation
+ ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive
+ ;Raleigh;NC;27613-3502;U.S.A.
+ TEL;TYPE=VOICE,MSG,WORK:+1-919-676-9515
+ TEL;TYPE=FAX,WORK:+1-919-676-9564
+ EMAIL;TYPE=INTERNET,PREF:Frank_Dawson@Lotus.com
+ EMAIL;TYPE=INTERNET:fdawson@earthlink.net
+ URL:http://home.earthlink.net/~fdawson
+ END:vCard
+
+
+ BEGIN:vCard
+ VERSION:3.0
+ FN:Tim Howes
+ ORG:Netscape Communications Corp.
+ ADR;TYPE=WORK:;;501 E. Middlefield Rd.;Mountain View;
+ CA; 94043;U.S.A.
+ TEL;TYPE=VOICE,MSG,WORK:+1-415-937-3419
+ TEL;TYPE=FAX,WORK:+1-415-528-4164
+ EMAIL;TYPE=INTERNET:howes@netscape.com
+ END:vCard
+
+8. Security Considerations
+
+ vCards can carry cryptographic keys or certificates, as described in
+ Section 3.7.2.
+
+ Section 3.7.1 specifies a desired security classification policy for
+ a particular vCard. That policy is not enforced in any way.
+
+ The vCard objects have no inherent authentication or privacy, but can
+ easily be carried by any security mechanism that transfers MIME
+ objects with authentication or privacy. In cases where threats of
+ "spoofed" vCard information is a concern, the vCard SHOULD BE
+
+
+
+Dawson & Howes Standards Track [Page 39]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ transported using one of these secure mechanisms.
+
+ The information in a vCard may become out of date. In cases where the
+ vitality of data is important to an originator of a vCard, the "URL"
+ type described in section 3.6.8 SHOULD BE specified. In addition, the
+ "REV" type described in section 3.6.4 can be specified to indicate
+ the last time that the vCard data was updated.
+
+9. References
+
+ [ISO 8601] ISO 8601:1988 - Data elements and interchange formats -
+ Information interchange - Representation of dates and
+ times - The International Organization for
+ Standardization, June, 1988.
+
+ [ISO 8601 TC] ISO 8601, Technical Corrigendum 1 - Data elements and
+ interchange formats - Information interchange -
+ Representation of dates and times - The International
+ Organization for Standardization, May, 1991.
+
+ [ISO 9070] ISO 9070, Information Processing - SGML support
+ facilities - Registration Procedures for Public Text
+ Owner Identifiers, April, 1991.
+
+ [CCITT E.163] Recommendation E.163 - Numbering Plan for The
+ International Telephone Service, CCITT Blue Book,
+ Fascicle II.2, pp. 128-134, November, 1988.
+
+ [CCITT X.121] Recommendation X.121 - International Numbering Plan for
+ Public Data Networks, CCITT Blue Book, Fascicle VIII.3,
+ pp. 317-332, November, 1988.
+
+ [CCITT X.520] Recommendation X.520 - The Directory - Selected
+ Attribute Types, November 1988.
+
+ [CCITT X.521] Recommendation X.521 - The Directory - Selected Object
+ Classes, November 1988.
+
+ [MIME-DIR] Howes, T., Smith, M., and F. Dawson, "A MIME Content-
+ Type for Directory Information", RFC 2425, September
+ 1998.
+
+ [RFC 1738] Berners-Lee, T., Masinter, L., and M. McCahill,
+ "Uniform Resource Locators (URL)", RFC 1738, December
+ 1994.
+
+ [RFC 1766] Alvestrand, H., "Tags for the Identification of
+ Languages", RFC 1766, March 1995.
+
+
+
+Dawson & Howes Standards Track [Page 40]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+ [RFC 1872] Levinson, E., "The MIME Multipart/Related Content-
+ type", RFC 1872, December 1995.
+
+ [RFC 2045] Freed, N., and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) - Part One: Format of Internet
+ Message Bodies", RFC 2045, November 1996.
+
+ [RFC 2046] Freed, N., and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) - Part Two: Media Types", RFC
+ 2046, November 1996.
+
+ [RFC 2047] Moore, K., "Multipurpose Internet Mail Extensions
+ (MIME) - Part Three: Message Header Extensions for
+ Non-ASCII Text", RFC 2047, November 1996.
+
+ [RFC 2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) - Part Four:
+ Registration Procedures", RFC 2048, January 1997.
+
+ [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC 2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+ [UNICODE] "The Unicode Standard - Version 2.0", The Unicode
+ Consortium, July 1996.
+
+ [VCARD] Internet Mail Consortium, "vCard - The Electronic
+ Business Card Version 2.1",
+ http://www.imc.org/pdi/vcard-21.txt, September 18,
+ 1996.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 41]
+
+RFC 2426 vCard MIME Directory Profile September 1998
+
+
+10. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dawson & Howes Standards Track [Page 42]
+
diff --git a/rfc/rfc2595.txt b/rfc/rfc2595.txt
@@ -0,0 +1,843 @@
+
+
+
+
+
+
+Network Working Group C. Newman
+Request for Comments: 2595 Innosoft
+Category: Standards Track June 1999
+
+
+ Using TLS with IMAP, POP3 and ACAP
+
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+1. Motivation
+
+ The TLS protocol (formerly known as SSL) provides a way to secure an
+ application protocol from tampering and eavesdropping. The option of
+ using such security is desirable for IMAP, POP and ACAP due to common
+ connection eavesdropping and hijacking attacks [AUTH]. Although
+ advanced SASL authentication mechanisms can provide a lightweight
+ version of this service, TLS is complimentary to simple
+ authentication-only SASL mechanisms or deployed clear-text password
+ login commands.
+
+ Many sites have a high investment in authentication infrastructure
+ (e.g., a large database of a one-way-function applied to user
+ passwords), so a privacy layer which is not tightly bound to user
+ authentication can protect against network eavesdropping attacks
+ without requiring a new authentication infrastructure and/or forcing
+ all users to change their password. Recognizing that such sites will
+ desire simple password authentication in combination with TLS
+ encryption, this specification defines the PLAIN SASL mechanism for
+ use with protocols which lack a simple password authentication
+ command such as ACAP and SMTP. (Note there is a separate RFC for the
+ STARTTLS command in SMTP [SMTPTLS].)
+
+ There is a strong desire in the IETF to eliminate the transmission of
+ clear-text passwords over unencrypted channels. While SASL can be
+ used for this purpose, TLS provides an additional tool with different
+ deployability characteristics. A server supporting both TLS with
+
+
+
+
+Newman Standards Track [Page 1]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ simple passwords and a challenge/response SASL mechanism is likely to
+ interoperate with a wide variety of clients without resorting to
+ unencrypted clear-text passwords.
+
+ The STARTTLS command rectifies a number of the problems with using a
+ separate port for a "secure" protocol variant. Some of these are
+ mentioned in section 7.
+
+1.1. Conventions Used in this Document
+
+ The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
+ "MAY", and "OPTIONAL" in this document are to be interpreted as
+ described in "Key words for use in RFCs to Indicate Requirement
+ Levels" [KEYWORDS].
+
+ Terms related to authentication are defined in "On Internet
+ Authentication" [AUTH].
+
+ Formal syntax is defined using ABNF [ABNF].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+2. Basic Interoperability and Security Requirements
+
+ The following requirements apply to all implementations of the
+ STARTTLS extension for IMAP, POP3 and ACAP.
+
+2.1. Cipher Suite Requirements
+
+ Implementation of the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher
+ suite is REQUIRED. This is important as it assures that any two
+ compliant implementations can be configured to interoperate.
+
+ All other cipher suites are OPTIONAL.
+
+2.2. Privacy Operational Mode Security Requirements
+
+ Both clients and servers SHOULD have a privacy operational mode which
+ refuses authentication unless successful activation of an encryption
+ layer (such as that provided by TLS) occurs prior to or at the time
+ of authentication and which will terminate the connection if that
+ encryption layer is deactivated. Implementations are encouraged to
+ have flexability with respect to the minimal encryption strength or
+ cipher suites permitted. A minimalist approach to this
+ recommendation would be an operational mode where the
+ TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite is mandatory prior to
+ permitting authentication.
+
+
+
+Newman Standards Track [Page 2]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ Clients MAY have an operational mode which uses encryption only when
+ it is advertised by the server, but authentication continues
+ regardless. For backwards compatibility, servers SHOULD have an
+ operational mode where only the authentication mechanisms required by
+ the relevant base protocol specification are needed to successfully
+ authenticate.
+
+2.3. Clear-Text Password Requirements
+
+ Clients and servers which implement STARTTLS MUST be configurable to
+ refuse all clear-text login commands or mechanisms (including both
+ standards-track and nonstandard mechanisms) unless an encryption
+ layer of adequate strength is active. Servers which allow
+ unencrypted clear-text logins SHOULD be configurable to refuse
+ clear-text logins both for the entire server, and on a per-user
+ basis.
+
+2.4. Server Identity Check
+
+ During the TLS negotiation, the client MUST check its understanding
+ of the server hostname against the server's identity as presented in
+ the server Certificate message, in order to prevent man-in-the-middle
+ attacks. Matching is performed according to these rules:
+
+ - The client MUST use the server hostname it used to open the
+ connection as the value to compare against the server name as
+ expressed in the server certificate. The client MUST NOT use any
+ form of the server hostname derived from an insecure remote source
+ (e.g., insecure DNS lookup). CNAME canonicalization is not done.
+
+ - If a subjectAltName extension of type dNSName is present in the
+ certificate, it SHOULD be used as the source of the server's
+ identity.
+
+ - Matching is case-insensitive.
+
+ - A "*" wildcard character MAY be used as the left-most name
+ component in the certificate. For example, *.example.com would
+ match a.example.com, foo.example.com, etc. but would not match
+ example.com.
+
+ - If the certificate contains multiple names (e.g. more than one
+ dNSName field), then a match with any one of the fields is
+ considered acceptable.
+
+ If the match fails, the client SHOULD either ask for explicit user
+ confirmation, or terminate the connection and indicate the server's
+ identity is suspect.
+
+
+
+Newman Standards Track [Page 3]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+2.5. TLS Security Policy Check
+
+ Both the client and server MUST check the result of the STARTTLS
+ command and subsequent TLS negotiation to see whether acceptable
+ authentication or privacy was achieved. Ignoring this step
+ completely invalidates using TLS for security. The decision about
+ whether acceptable authentication or privacy was achieved is made
+ locally, is implementation-dependent, and is beyond the scope of this
+ document.
+
+3. IMAP STARTTLS extension
+
+ When the TLS extension is present in IMAP, "STARTTLS" is listed as a
+ capability in response to the CAPABILITY command. This extension
+ adds a single command, "STARTTLS" to the IMAP protocol which is used
+ to begin a TLS negotiation.
+
+3.1. STARTTLS Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - begin TLS negotiation
+ BAD - command unknown or arguments invalid
+
+ A TLS negotiation begins immediately after the CRLF at the end of
+ the tagged OK response from the server. Once a client issues a
+ STARTTLS command, it MUST NOT issue further commands until a
+ server response is seen and the TLS negotiation is complete.
+
+ The STARTTLS command is only valid in non-authenticated state.
+ The server remains in non-authenticated state, even if client
+ credentials are supplied during the TLS negotiation. The SASL
+ [SASL] EXTERNAL mechanism MAY be used to authenticate once TLS
+ client credentials are successfully exchanged, but servers
+ supporting the STARTTLS command are not required to support the
+ EXTERNAL mechanism.
+
+ Once TLS has been started, the client MUST discard cached
+ information about server capabilities and SHOULD re-issue the
+ CAPABILITY command. This is necessary to protect against
+ man-in-the-middle attacks which alter the capabilities list prior
+ to STARTTLS. The server MAY advertise different capabilities
+ after STARTTLS.
+
+ The formal syntax for IMAP is amended as follows:
+
+
+
+
+Newman Standards Track [Page 4]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ command_any =/ "STARTTLS"
+
+ Example: C: a001 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
+ S: a001 OK CAPABILITY completed
+ C: a002 STARTTLS
+ S: a002 OK Begin TLS negotiation now
+ <TLS negotiation, further commands are under TLS layer>
+ C: a003 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=EXTERNAL
+ S: a003 OK CAPABILITY completed
+ C: a004 LOGIN joe password
+ S: a004 OK LOGIN completed
+
+3.2. IMAP LOGINDISABLED capability
+
+ The current IMAP protocol specification (RFC 2060) requires the
+ implementation of the LOGIN command which uses clear-text passwords.
+ Many sites may choose to disable this command unless encryption is
+ active for security reasons. An IMAP server MAY advertise that the
+ LOGIN command is disabled by including the LOGINDISABLED capability
+ in the capability response. Such a server will respond with a tagged
+ "NO" response to any attempt to use the LOGIN command.
+
+ An IMAP server which implements STARTTLS MUST implement support for
+ the LOGINDISABLED capability on unencrypted connections.
+
+ An IMAP client which complies with this specification MUST NOT issue
+ the LOGIN command if this capability is present.
+
+ This capability is useful to prevent clients compliant with this
+ specification from sending an unencrypted password in an environment
+ subject to passive attacks. It has no impact on an environment
+ subject to active attacks as a man-in-the-middle attacker can remove
+ this capability. Therefore this does not relieve clients of the need
+ to follow the privacy mode recommendation in section 2.2.
+
+ Servers advertising this capability will fail to interoperate with
+ many existing compliant IMAP clients and will be unable to prevent
+ those clients from disclosing the user's password.
+
+4. POP3 STARTTLS extension
+
+ The POP3 STARTTLS extension adds the STLS command to POP3 servers.
+ If this is implemented, the POP3 extension mechanism [POP3EXT] MUST
+ also be implemented to avoid the need for client probing of multiple
+ commands. The capability name "STLS" indicates this command is
+ present and permitted in the current state.
+
+
+
+Newman Standards Track [Page 5]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ STLS
+
+ Arguments: none
+
+ Restrictions:
+ Only permitted in AUTHORIZATION state.
+
+ Discussion:
+ A TLS negotiation begins immediately after the CRLF at the
+ end of the +OK response from the server. A -ERR response
+ MAY result if a security layer is already active. Once a
+ client issues a STLS command, it MUST NOT issue further
+ commands until a server response is seen and the TLS
+ negotiation is complete.
+
+ The STLS command is only permitted in AUTHORIZATION state
+ and the server remains in AUTHORIZATION state, even if
+ client credentials are supplied during the TLS negotiation.
+ The AUTH command [POP-AUTH] with the EXTERNAL mechanism
+ [SASL] MAY be used to authenticate once TLS client
+ credentials are successfully exchanged, but servers
+ supporting the STLS command are not required to support the
+ EXTERNAL mechanism.
+
+ Once TLS has been started, the client MUST discard cached
+ information about server capabilities and SHOULD re-issue
+ the CAPA command. This is necessary to protect against
+ man-in-the-middle attacks which alter the capabilities list
+ prior to STLS. The server MAY advertise different
+ capabilities after STLS.
+
+ Possible Responses:
+ +OK -ERR
+
+ Examples:
+ C: STLS
+ S: +OK Begin TLS negotiation
+ <TLS negotiation, further commands are under TLS layer>
+ ...
+ C: STLS
+ S: -ERR Command not permitted when TLS active
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 6]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+5. ACAP STARTTLS extension
+
+ When the TLS extension is present in ACAP, "STARTTLS" is listed as a
+ capability in the ACAP greeting. No arguments to this capability are
+ defined at this time. This extension adds a single command,
+ "STARTTLS" to the ACAP protocol which is used to begin a TLS
+ negotiation.
+
+5.1. STARTTLS Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - begin TLS negotiation
+ BAD - command unknown or arguments invalid
+
+ A TLS negotiation begins immediately after the CRLF at the end of
+ the tagged OK response from the server. Once a client issues a
+ STARTTLS command, it MUST NOT issue further commands until a
+ server response is seen and the TLS negotiation is complete.
+
+ The STARTTLS command is only valid in non-authenticated state.
+ The server remains in non-authenticated state, even if client
+ credentials are supplied during the TLS negotiation. The SASL
+ [SASL] EXTERNAL mechanism MAY be used to authenticate once TLS
+ client credentials are successfully exchanged, but servers
+ supporting the STARTTLS command are not required to support the
+ EXTERNAL mechanism.
+
+ After the TLS layer is established, the server MUST re-issue an
+ untagged ACAP greeting. This is necessary to protect against
+ man-in-the-middle attacks which alter the capabilities list prior
+ to STARTTLS. The client MUST discard cached capability
+ information and replace it with the information from the new ACAP
+ greeting. The server MAY advertise different capabilities after
+ STARTTLS.
+
+ The formal syntax for ACAP is amended as follows:
+
+ command_any =/ "STARTTLS"
+
+ Example: S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a002 STARTTLS
+ S: a002 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN" "EXTERNAL")
+
+
+
+
+Newman Standards Track [Page 7]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+6. PLAIN SASL mechanism
+
+ Clear-text passwords are simple, interoperate with almost all
+ existing operating system authentication databases, and are useful
+ for a smooth transition to a more secure password-based
+ authentication mechanism. The drawback is that they are unacceptable
+ for use over an unencrypted network connection.
+
+ This defines the "PLAIN" SASL mechanism for use with ACAP and other
+ protocols with no clear-text login command. The PLAIN SASL mechanism
+ MUST NOT be advertised or used unless a strong encryption layer (such
+ as the provided by TLS) is active or backwards compatibility dictates
+ otherwise.
+
+ The mechanism consists of a single message from the client to the
+ server. The client sends the authorization identity (identity to
+ login as), followed by a US-ASCII NUL character, followed by the
+ authentication identity (identity whose password will be used),
+ followed by a US-ASCII NUL character, followed by the clear-text
+ password. The client may leave the authorization identity empty to
+ indicate that it is the same as the authentication identity.
+
+ The server will verify the authentication identity and password with
+ the system authentication database and verify that the authentication
+ credentials permit the client to login as the authorization identity.
+ If both steps succeed, the user is logged in.
+
+ The server MAY also use the password to initialize any new
+ authentication database, such as one suitable for CRAM-MD5
+ [CRAM-MD5].
+
+ Non-US-ASCII characters are permitted as long as they are represented
+ in UTF-8 [UTF-8]. Use of non-visible characters or characters which
+ a user may be unable to enter on some keyboards is discouraged.
+
+ The formal grammar for the client message using Augmented BNF [ABNF]
+ follows.
+
+ message = [authorize-id] NUL authenticate-id NUL password
+ authenticate-id = 1*UTF8-SAFE ; MUST accept up to 255 octets
+ authorize-id = 1*UTF8-SAFE ; MUST accept up to 255 octets
+ password = 1*UTF8-SAFE ; MUST accept up to 255 octets
+ NUL = %x00
+ UTF8-SAFE = %x01-09 / %x0B-0C / %x0E-7F / UTF8-2 /
+ UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
+ UTF8-1 = %x80-BF
+ UTF8-2 = %xC0-DF UTF8-1
+ UTF8-3 = %xE0-EF 2UTF8-1
+
+
+
+Newman Standards Track [Page 8]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ UTF8-4 = %xF0-F7 3UTF8-1
+ UTF8-5 = %xF8-FB 4UTF8-1
+ UTF8-6 = %xFC-FD 5UTF8-1
+
+ Here is an example of how this might be used to initialize a CRAM-MD5
+ authentication database for ACAP:
+
+ Example: S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a001 AUTHENTICATE "CRAM-MD5"
+ S: + "<1896.697170952@postoffice.reston.mci.net>"
+ C: "tim b913a602c7eda7a495b4e6e7334d3890"
+ S: a001 NO (TRANSITION-NEEDED)
+ "Please change your password, or use TLS to login"
+ C: a002 STARTTLS
+ S: a002 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN" "EXTERNAL")
+ C: a003 AUTHENTICATE "PLAIN" {21+}
+ C: <NUL>tim<NUL>tanstaaftanstaaf
+ S: a003 OK CRAM-MD5 password initialized
+
+ Note: In this example, <NUL> represents a single ASCII NUL octet.
+
+7. imaps and pop3s ports
+
+ Separate "imaps" and "pop3s" ports were registered for use with SSL.
+ Use of these ports is discouraged in favor of the STARTTLS or STLS
+ commands.
+
+ A number of problems have been observed with separate ports for
+ "secure" variants of protocols. This is an attempt to enumerate some
+ of those problems.
+
+ - Separate ports lead to a separate URL scheme which intrudes into
+ the user interface in inappropriate ways. For example, many web
+ pages use language like "click here if your browser supports SSL."
+ This is a decision the browser is often more capable of making than
+ the user.
+
+ - Separate ports imply a model of either "secure" or "not secure."
+ This can be misleading in a number of ways. First, the "secure"
+ port may not in fact be acceptably secure as an export-crippled
+ cipher suite might be in use. This can mislead users into a false
+ sense of security. Second, the normal port might in fact be
+ secured by using a SASL mechanism which includes a security layer.
+ Thus the separate port distinction makes the complex topic of
+ security policy even more confusing. One common result of this
+ confusion is that firewall administrators are often misled into
+
+
+
+Newman Standards Track [Page 9]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ permitting the "secure" port and blocking the standard port. This
+ could be a poor choice given the common use of SSL with a 40-bit
+ key encryption layer and plain-text password authentication is less
+ secure than strong SASL mechanisms such as GSSAPI with Kerberos 5.
+
+ - Use of separate ports for SSL has caused clients to implement only
+ two security policies: use SSL or don't use SSL. The desirable
+ security policy "use TLS when available" would be cumbersome with
+ the separate port model, but is simple with STARTTLS.
+
+ - Port numbers are a limited resource. While they are not yet in
+ short supply, it is unwise to set a precedent that could double (or
+ worse) the speed of their consumption.
+
+
+8. IANA Considerations
+
+ This constitutes registration of the "STARTTLS" and "LOGINDISABLED"
+ IMAP capabilities as required by section 7.2.1 of RFC 2060 [IMAP].
+
+ The registration for the POP3 "STLS" capability follows:
+
+ CAPA tag: STLS
+ Arguments: none
+ Added commands: STLS
+ Standard commands affected: May enable USER/PASS as a side-effect.
+ CAPA command SHOULD be re-issued after successful completion.
+ Announced states/Valid states: AUTHORIZATION state only.
+ Specification reference: this memo
+
+ The registration for the ACAP "STARTTLS" capability follows:
+
+ Capability name: STARTTLS
+ Capability keyword: STARTTLS
+ Capability arguments: none
+ Published Specification(s): this memo
+ Person and email address for further information:
+ see author's address section below
+
+ The registration for the PLAIN SASL mechanism follows:
+
+ SASL mechanism name: PLAIN
+ Security Considerations: See section 9 of this memo
+ Published specification: this memo
+ Person & email address to contact for further information:
+ see author's address section below
+ Intended usage: COMMON
+ Author/Change controller: see author's address section below
+
+
+
+Newman Standards Track [Page 10]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+9. Security Considerations
+
+ TLS only provides protection for data sent over a network connection.
+ Messages transferred over IMAP or POP3 are still available to server
+ administrators and usually subject to eavesdropping, tampering and
+ forgery when transmitted through SMTP or NNTP. TLS is no substitute
+ for an end-to-end message security mechanism using MIME security
+ multiparts [MIME-SEC].
+
+ A man-in-the-middle attacker can remove STARTTLS from the capability
+ list or generate a failure response to the STARTTLS command. In
+ order to detect such an attack, clients SHOULD warn the user when
+ session privacy is not active and/or be configurable to refuse to
+ proceed without an acceptable level of security.
+
+ A man-in-the-middle attacker can always cause a down-negotiation to
+ the weakest authentication mechanism or cipher suite available. For
+ this reason, implementations SHOULD be configurable to refuse weak
+ mechanisms or cipher suites.
+
+ Any protocol interactions prior to the TLS handshake are performed in
+ the clear and can be modified by a man-in-the-middle attacker. For
+ this reason, clients MUST discard cached information about server
+ capabilities advertised prior to the start of the TLS handshake.
+
+ Clients are encouraged to clearly indicate when the level of
+ encryption active is known to be vulnerable to attack using modern
+ hardware (such as encryption keys with 56 bits of entropy or less).
+
+ The LOGINDISABLED IMAP capability (discussed in section 3.2) only
+ reduces the potential for passive attacks, it provides no protection
+ against active attacks. The responsibility remains with the client
+ to avoid sending a password over a vulnerable channel.
+
+ The PLAIN mechanism relies on the TLS encryption layer for security.
+ When used without TLS, it is vulnerable to a common network
+ eavesdropping attack. Therefore PLAIN MUST NOT be advertised or used
+ unless a suitable TLS encryption layer is active or backwards
+ compatibility dictates otherwise.
+
+ When the PLAIN mechanism is used, the server gains the ability to
+ impersonate the user to all services with the same password
+ regardless of any encryption provided by TLS or other network privacy
+ mechanisms. While many other authentication mechanisms have similar
+ weaknesses, stronger SASL mechanisms such as Kerberos address this
+ issue. Clients are encouraged to have an operational mode where all
+ mechanisms which are likely to reveal the user's password to the
+ server are disabled.
+
+
+
+Newman Standards Track [Page 11]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ The security considerations for TLS apply to STARTTLS and the
+ security considerations for SASL apply to the PLAIN mechanism.
+ Additional security requirements are discussed in section 2.
+
+10. References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November 1997.
+
+ [AUTH] Haller, N. and R. Atkinson, "On Internet Authentication",
+ RFC 1704, October 1994.
+
+ [CRAM-MD5] Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP
+ AUTHorize Extension for Simple Challenge/Response", RFC
+ 2195, September 1997.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [MIME-SEC] Galvin, J., Murphy, S., Crocker, S. and N. Freed,
+ "Security Multiparts for MIME: Multipart/Signed and
+ Multipart/Encrypted", RFC 1847, October 1995.
+
+ [POP3] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
+ STD 53, RFC 1939, May 1996.
+
+ [POP3EXT] Gellens, R., Newman, C. and L. Lundblade, "POP3 Extension
+ Mechanism", RFC 2449, November 1998.
+
+ [POP-AUTH] Myers, J., "POP3 AUTHentication command", RFC 1734,
+ December 1994.
+
+ [SASL] Myers, J., "Simple Authentication and Security Layer
+ (SASL)", RFC 2222, October 1997.
+
+ [SMTPTLS] Hoffman, P., "SMTP Service Extension for Secure SMTP over
+ TLS", RFC 2487, January 1999.
+
+ [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
+ RFC 2246, January 1999.
+
+
+
+
+
+Newman Standards Track [Page 12]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 2279, January 1998.
+
+
+11. Author's Address
+
+ Chris Newman
+ Innosoft International, Inc.
+ 1050 Lakes Drive
+ West Covina, CA 91790 USA
+
+ EMail: chris.newman@innosoft.com
+
+
+A. Appendix -- Compliance Checklist
+
+ An implementation is not compliant if it fails to satisfy one or more
+ of the MUST requirements for the protocols it implements. An
+ implementation that satisfies all the MUST and all the SHOULD
+ requirements for its protocols is said to be "unconditionally
+ compliant"; one that satisfies all the MUST requirements but not all
+ the SHOULD requirements for its protocols is said to be
+ "conditionally compliant".
+
+ Rules Section
+ ----- -------
+ Mandatory-to-implement Cipher Suite 2.1
+ SHOULD have mode where encryption required 2.2
+ server SHOULD have mode where TLS not required 2.2
+ MUST be configurable to refuse all clear-text login
+ commands or mechanisms 2.3
+ server SHOULD be configurable to refuse clear-text
+ login commands on entire server and on per-user basis 2.3
+ client MUST check server identity 2.4
+ client MUST use hostname used to open connection 2.4
+ client MUST NOT use hostname from insecure remote lookup 2.4
+ client SHOULD support subjectAltName of dNSName type 2.4
+ client SHOULD ask for confirmation or terminate on fail 2.4
+ MUST check result of STARTTLS for acceptable privacy 2.5
+ client MUST NOT issue commands after STARTTLS
+ until server response and negotiation done 3.1,4,5.1
+ client MUST discard cached information 3.1,4,5.1,9
+ client SHOULD re-issue CAPABILITY/CAPA command 3.1,4
+ IMAP server with STARTTLS MUST implement LOGINDISABLED 3.2
+ IMAP client MUST NOT issue LOGIN if LOGINDISABLED 3.2
+ POP server MUST implement POP3 extensions 4
+ ACAP server MUST re-issue ACAP greeting 5.1
+
+
+
+
+Newman Standards Track [Page 13]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+ client SHOULD warn when session privacy not active and/or
+ refuse to proceed without acceptable security level 9
+ SHOULD be configurable to refuse weak mechanisms or
+ cipher suites 9
+
+ The PLAIN mechanism is an optional part of this specification.
+ However if it is implemented the following rules apply:
+
+ Rules Section
+ ----- -------
+ MUST NOT use PLAIN unless strong encryption active
+ or backwards compatibility dictates otherwise 6,9
+ MUST use UTF-8 encoding for characters in PLAIN 6
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 14]
+
+RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 15]
+
diff --git a/rfc/rfc2646.txt b/rfc/rfc2646.txt
@@ -0,0 +1,787 @@
+
+
+
+
+
+
+Network Working Group R. Gellens, Editor
+Request for Comments: 2646 Qualcomm
+Updates: 2046 August 1999
+Category: Standards Track
+
+
+ The Text/Plain Format Parameter
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+Table of Contents
+
+ 1. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Conventions Used in this Document . . . . . . . . . . . . . 2
+ 3. The Problem . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 3.1. Paragraph Text . . . . . . . . . . . . . . . . . . . . 3
+ 3.2. Embarrassing Line Wrap . . . . . . . . . . . . . . . . . 3
+ 3.3. New Media Types . . . . . . . . . . . . . . . . . . . . 4
+ 4. The Format Parameter to the Text/Plain Media Type . . . . . 4
+ 4.1. Generating Format=Flowed . . . . . . . . . . . . . . . 5
+ 4.2. Interpreting Format=Flowed . . . . . . . . . . . . . . . 6
+ 4.3. Usenet Signature Convention . . . . . . . . . . . . . . 7
+ 4.4. Space-Stuffing . . . . . . . . . . . . . . . . . . . . . 7
+ 4.5. Quoting . . . . . . . . . . . . . . . . . . . . . . . . 8
+ 4.6. Digital Signatures and Encryption . . . . . . . . . . . 9
+ 4.7. Line Analysis Table . . . . . . . . . . . . . . . . . . 10
+ 4.8. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
+ 5. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
+ 6. Failure Modes . . . . . . . . . . . . . . . . . . . . . . . 11
+ 6.1. Trailing White Space Corruption . . . . . . . . . . . . 11
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . 12
+ 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 12
+ 9. Internationalization Considerations . . . . . . . . . . . . 12
+ 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12
+ 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
+ 12. Editor's Address . . . . . . . . . . . . . . . . . . . . . 13
+ 13. Full Copyright Statement . . . . . . . . . . . . . . . . . . 14
+
+
+
+
+Gellens Standards Track [Page 1]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+1. Abstract
+
+ Interoperability problems have been observed with erroneous labelling
+ of paragraph text as Text/Plain, and with various forms of
+ "embarrassing line wrap." (See section 3.)
+
+ Attempts to deploy new media types, such as Text/Enriched [RICH] and
+ Text/HTML [HTML] have suffered from a lack of backwards compatibility
+ and an often hostile user reaction at the receiving end.
+
+ What is required is a format which is in all significant ways
+ Text/Plain, and therefore is quite suitable for display as
+ Text/Plain, and yet allows the sender to express to the receiver
+ which lines can be considered a logical paragraph, and thus flowed
+ (wrapped and joined) as appropriate.
+
+ This memo proposes a new parameter to be used with Text/Plain, and,
+ in the presence of this parameter, the use of trailing whitespace to
+ indicate flowed lines. This results in an encoding which appears as
+ normal Text/Plain in older implementations, since it is in fact
+ normal Text/Plain.
+
+2. Conventions Used in this Document
+
+ The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
+ and "MAY" in this document are to be interpreted as described in "Key
+ words for use in RFCs to Indicate Requirement Levels" [KEYWORDS].
+
+3. The Problem
+
+ The Text/Plain media type is the lowest common denominator of
+ Internet email, with lines of no more than 997 characters (by
+ convention usually no more than 80), and where the CRLF sequence
+ represents a line break [MIME-IMT].
+
+ Text/Plain is usually displayed as preformatted text, often in a
+ fixed font. That is, the characters start at the left margin of the
+ display window, and advance to the right until a CRLF sequence is
+ seen, at which point a new line is started, again at the left margin.
+ When a line length exceeds the display window, some clients will wrap
+ the line, while others invoke a horizontal scroll bar.
+
+ Text which meets this description is defined by this memo as "fixed".
+
+ Some interoperability problems have been observed with this media
+ type:
+
+
+
+
+
+Gellens Standards Track [Page 2]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+3.1. Paragraph Text
+
+ Many modern programs use a proportional-spaced font and CRLF to
+ represent paragraph breaks. Line breaks are "soft", occurring as
+ needed on display. That is, characters are grouped into a paragraph
+ until a CRLF sequence is seen, at which point a new paragraph is
+ started. Each paragraph is displayed, starting at the left margin
+ (or paragraph indent), and continuing to the right until a word is
+ encountered which does not fit in the remaining display width. This
+ word is displayed at the left margin of the next line. This
+ continues until the paragraph ends (a CRLF is seen). Extra vertical
+ space is left between paragraphs.
+
+ Text which meets this description is defined by this memo as
+ "flowed".
+
+ Numerous software products erroneously label this media type as
+ Text/Plain, resulting in much user discomfort.
+
+3.2. Embarrassing Line Wrap
+
+ As Text/Plain messages get quoted in replies or forwarded messages,
+ the length of each line gradually increases, resulting in
+ "embarrassing line wrap." This results in text which is at best hard
+ to read, and often confuses attributions.
+
+ Example:
+
+ >>>>>>This is a comment from the first message to show a
+ >quoting example.
+ >>>>>This is a comment from the second message to show a
+ >quoting example.
+ >>>>This is a comment from the third message.
+ >>>This is a comment from the fourth message.
+
+ It can be confusing to assign attribution to lines 2 and 4 above.
+
+ In addition, as devices with display widths smaller than 80
+ characters become more popular, embarrassing line wrap has become
+ even more prevalent, even with unquoted text.
+
+
+
+
+
+
+
+
+
+
+
+Gellens Standards Track [Page 3]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ Example:
+
+ This is paragraph text that is
+ meant to be flowed across
+ several lines.
+ However, the sending mailer is
+ converting it to fixed text at
+ a width of 72
+ characters, which causes it to
+ look like this when shown on a
+ PDA with only
+ 30 character lines.
+
+3.3. New Media Types
+
+ Attempts to deploy new media types, such as Text/Enriched [RICH] and
+ Text/HTML [HTML] have suffered from a lack of backwards compatibility
+ and an often hostile user reaction at the receiving end.
+
+ In particular, Text/Enriched requires that open angle brackets ("<")
+ and hard line breaks be doubled, with resulting user unhappiness when
+ viewed as Text/Plain. Text/HTML requires even more alteration of
+ text, with a corresponding increase in user complaints.
+
+ A proposal to define a new media type to explicitly represent the
+ paragraph form suffered from a lack of interoperability with
+ currently deployed software. Some programs treat unknown subtypes of
+ Text as an attachment.
+
+ What is desired is a format which is in all significant ways
+ Text/Plain, and therefore is quite suitable for display as
+ Text/Plain, and yet allows the sender to express to the receiver
+ which lines can be considered a logical paragraph, and thus flowed
+ (wrapped and joined) as appropriate.
+
+4. The Format Parameter to the Text/Plain Media Type
+
+ This document defines a new MIME parameter for use with Text/Plain:
+
+ Name: Format
+ Value: Fixed, Flowed
+
+ (Neither the parameter name nor its value are case sensitive.)
+
+ If not specified, a value of Fixed is assumed. The semantics of the
+ Fixed value are the usual associated with Text/Plain [MIME-IMT].
+
+
+
+
+
+Gellens Standards Track [Page 4]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ A value of Flowed indicates that the definition of flowed text (as
+ specified in this memo) was used on generation, and MAY be used on
+ reception.
+
+ This section discusses flowed text; section 5 provides a formal
+ definition.
+
+ Because flowed lines are all-but-indistinguishable from fixed lines,
+ currently deployed software treats flowed lines as normal Text/Plain
+ (which is what they are). Thus, no interoperability problems are
+ expected.
+
+ Note that this memo describes an on-the-wire format. It does not
+ address formats for local file storage.
+
+4.1. Generating Format=Flowed
+
+ When generating Format=Flowed text, lines SHOULD be shorter than 80
+ characters. As suggested values, any paragraph longer than 79
+ characters in total length could be wrapped using lines of 72 or
+ fewer characters. While the specific line length used is a matter of
+ aesthetics and preference, longer lines are more likely to require
+ rewrapping and to encounter difficulties with older mailers. It has
+ been suggested that 66 character lines are the most readable.
+
+ (The reason for the restriction to 79 or fewer characters between
+ CRLFs on the wire is to ensure that all lines, even when displayed by
+ a non-flowed-aware program, will fit in a standard 80-column screen
+ without having to be wrapped. The limit is 79, not 80, because while
+ 80 fit on a line, the last column is often reserved for a line-wrap
+ indicator.)
+
+ When creating flowed text, the generating agent wraps, that is,
+ inserts 'soft' line breaks as needed. Soft line breaks are added
+ between words. Because a soft line break is a SP CRLF sequence, the
+ generating agent creates one by inserting a CRLF after the occurance
+ of a space.
+
+ A generating agent SHOULD NOT insert white space into a word (a
+ sequence of printable characters not containing spaces). If faced
+ with a word which exceeds 79 characters (but less than 998
+ characters, the [SMTP] limit on line length), the agent SHOULD send
+ the word as is and exceed the 79-character limit on line length.
+
+
+
+
+
+
+
+
+Gellens Standards Track [Page 5]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ A generating agent SHOULD:
+
+ 1. Ensure all lines (fixed and flowed) are 79 characters or
+ fewer in length, counting the trailing space but not
+ counting the CRLF, unless a word by itself exceeds 79
+ characters.
+ 2. Trim spaces before user-inserted hard line breaks.
+ 3. Space-stuff lines which start with a space, "From ", or
+ ">".
+
+ In order to create messages which do not require space-stuffing, and
+ are thus more aesthetically pleasing when viewed as Format=Fixed, a
+ generating agent MAY avoid wrapping immediately before ">", "From ",
+ or space.
+
+ (See sections 4.4 and 4.5 for more information on space-stuffing and
+ quoting, respectively.)
+
+ A Format=Flowed message consists of zero or more paragraphs, each
+ containing one or more flowed lines followed by one fixed line. The
+ usual case is a series of flowed text lines with blank (empty) fixed
+ lines between them.
+
+ Any number of fixed lines can appear between paragraphs.
+
+ [Quoted-Printable] encoding SHOULD NOT be used with Format=Flowed
+ unless absolutely necessary (for example, non-US-ASCII (8-bit)
+ characters over a strictly 7-bit transport such as unextended SMTP).
+ In particular, a message SHOULD NOT be encoded in Quoted-Printable
+ for the sole purpose of protecting the trailing space on flowed lines
+ unless the body part is cryptographically signed or encrypted (see
+ Section 4.6).
+
+ The intent of Format=Flowed is to allow user agents to generate
+ flowed text which is non-obnoxious when viewed as pure, raw
+ Text/Plain (without any decoding); use of Quoted-Printable hinders
+ this and may cause Format=Flowed to be rejected by end users.
+
+4.2. Interpreting Format=Flowed
+
+ If the first character of a line is a quote mark (">"), the line is
+ considered to be quoted (see section 4.5). Logically, all quote
+ marks are counted and deleted, resulting in a line with a non-zero
+ quote depth, and content. (The agent is of course free to display the
+ content with quote marks or excerpt bars or anything else.)
+ Logically, this test for quoted lines is done before any other tests
+ (that is, before checking for space-stuffed and flowed).
+
+
+
+
+Gellens Standards Track [Page 6]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ If the first character of a line is a space, the line has been
+ space-stuffed (see section 4.4). Logically, this leading space is
+ deleted before examining the line further (that is, before checking
+ for flowed).
+
+ If the line ends in one or more spaces, the line is flowed.
+ Otherwise it is fixed. Trailing spaces are part of the line's
+ content, but the CRLF of a soft line break is not.
+
+ A series of one or more flowed lines followed by one fixed line is
+ considered a paragraph, and MAY be flowed (wrapped and unwrapped) as
+ appropriate on display and in the construction of new messages (see
+ section 4.5).
+
+ A line consisting of one or more spaces (after deleting a stuffed
+ space) is considered a flowed line.
+
+4.3. Usenet Signature Convention
+
+ There is a convention in Usenet news of using "-- " as the separator
+ line between the body and the signature of a message. When
+ generating a Format=Flowed message containing a Usenet-style
+ separator before the signature, the separator line is sent as-is.
+ This is a special case; an (optionally quoted) line consisting of
+ DASH DASH SP is not considered flowed.
+
+4.4. Space-Stuffing
+
+ In order to allow for unquoted lines which start with ">", and to
+ protect against systems which "From-munge" in-transit messages
+ (modifying any line which starts with "From " to ">From "),
+ Format=Flowed provides for space-stuffing.
+
+ Space-stuffing adds a single space to the start of any line which
+ needs protection when the message is generated. On reception, if the
+ first character of a line is a space, it is logically deleted. This
+ occurs after the test for a quoted line, and before the test for a
+ flowed line.
+
+ On generation, any unquoted lines which start with ">", and any lines
+ which start with a space or "From " SHOULD be space-stuffed. Other
+ lines MAY be space-stuffed as desired.
+
+ (Note that space-stuffing is similar to dot-stuffing as specified in
+ [SMTP].)
+
+
+
+
+
+
+Gellens Standards Track [Page 7]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ If a space-stuffed message is received by an agent which handles
+ Format=Flowed, the space-stuffing is reversed and thus the message
+ appears unchanged. An agent which is not aware of Format=Flowed will
+ of course not undo any space-stuffing, thus Format=Flowed messages
+ may appear with a leading space on some lines (those which start with
+ a space, ">" which is not a quote indicator, or "From "). Since
+ lines which require space-stuffing rarely occur, and the aesthetic
+ consequences of unreversed space-stuffing are minimal, this is not
+ expected to be a significant problem.
+
+4.5. Quoting
+
+ In Format=Flowed, the canonical quote indicator (or quote mark) is
+ one or more close angle bracket (">") characters. Lines which start
+ with the quote indicator are considered quoted. The number of ">"
+ characters at the start of the line specifies the quote depth.
+ Flowed lines which are also quoted may require special handling on
+ display and when copied to new messages.
+
+ When creating quoted flowed lines, each such line starts with the
+ quote indicator.
+
+ Note that because of space-stuffing, the lines
+ >> Exit, Stage Left
+ and
+ >>Exit, Stage Left
+ are semantically identical; both have a quote-depth of two, and a
+ content of "Exit, Stage Left".
+
+ However, the line
+ > > Exit, Stage Left
+ is different. It has a quote-depth of one, and a content of
+ "> Exit, Stage Left".
+
+ When generating quoted flowed lines, an agent needs to pay attention
+ to changes in quote depth. A sequence of quoted lines of the same
+ quote depth SHOULD be encoded as a paragraph, with the last line
+ generated as fixed and prior lines generated as flowed.
+
+ If a receiving agent wishes to reformat flowed quoted lines (joining
+ and/or wrapping them) on display or when generating new messages, the
+ lines SHOULD be de-quoted, reformatted, and then re-quoted. To
+ de-quote, the number of close angle brackets in the quote indicator
+ at the start of each line is counted. Consecutive lines with the
+ same quoting depth are considered one paragraph and are reformatted
+ together. To re-quote after reformatting, a quote indicator
+ containing the same number of close angle brackets originally present
+ is prefixed to each line.
+
+
+
+Gellens Standards Track [Page 8]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ On reception, if a change in quoting depth occurs on a flowed line,
+ this is an improperly formatted message. The receiver SHOULD handle
+ this error by using the 'quote-depth-wins' rule, which is to ignore
+ the flowed indicator and treat the line as fixed. That is, the
+ change in quote depth ends the paragraph.
+
+ For example, consider the following sequence of lines (using '*' to
+ indicate a soft line break, i.e., SP CRLF, and '#' to indicate a hard
+ line break, i.e., CRLF):
+
+ > Thou villainous ill-breeding spongy dizzy-eyed*
+ > reeky elf-skinned pigeon-egg!* <--- problem ---<
+ >> Thou artless swag-bellied milk-livered*
+ >> dismal-dreaming idle-headed scut!#
+ >>> Thou errant folly-fallen spleeny reeling-ripe*
+ >>> unmuzzled ratsbane!#
+ >>>> Henceforth, the coding style is to be strictly*
+ >>>> enforced, including the use of only upper case.#
+ >>>>> I've noticed a lack of adherence to the coding*
+ >>>>> styles, of late.#
+ >>>>>> Any complaints?#
+
+ The second line ends in a soft line break, even though it is the last
+ line of the one-deep quote block. The question then arises as to how
+ this line should be interpreted, considering that the next line is
+ the first line of the two-deep quote block.
+
+ The example text above, when processed according to quote-depth wins,
+ results in the first two lines being considered as one quoted, flowed
+ section, with a quote depth of 1; the third and fourth lines become a
+ quoted, flowed section, with a quote depth of 2.
+
+ A generating agent SHOULD NOT create this situation; a receiving
+ agent SHOULD handle it using quote-depth wins.
+
+4.6. Digital Signatures and Encryption
+
+ If a message is digitally signed or encrypted it is important that
+ cryptographic processing use the on-the-wire Format=Flowed format.
+ That is, during generation the message SHOULD be prepared for
+ transmission, including addition of soft line breaks, space-stuffing,
+ and [Quoted-Printable] encoding (to protect soft line breaks) before
+ being digitally signed or encrypted; similarly, on receipt the
+ message SHOULD have the signature verified or be decrypted before
+ [Quoted-Printable] decoding and removal of stuffed spaces, soft line
+ breaks and quote marks, and reflowing.
+
+
+
+
+
+Gellens Standards Track [Page 9]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+4.7. Line Analysis Table
+
+ Lines contained in a Text/Plain body part with Format=Flowed can be
+ analyzed by examining the start and end of the line. If the line
+ starts with the quote indicator, it is quoted. If the line ends with
+ one or more space characters, it is flowed. This is summarized by
+ the following table:
+
+ Starts Ends in
+ with One or Line
+ Quote More Spaces Type
+ ------ ----------- ---------------
+ no no unquoted, fixed
+ yes no quoted, fixed
+ no yes unquoted, flowed
+ yes yes quoted, flowed
+
+4.8. Examples
+
+ The following example contains three paragraphs:
+
+ `Take some more tea,' the March Hare said to Alice, very
+ earnestly.
+
+ `I've had nothing yet,' Alice replied in an offended tone, `so I
+ can't take more.'
+
+ `You mean you can't take LESS,' said the Hatter: `it's very easy
+ to take MORE than nothing.'
+
+ This could be encoded as follows (using '*' to indicate a soft line
+ break, that is, SP CRLF sequence, and '#' to indicate a hard line
+ break, that is, CRLF):
+
+ `Take some more tea,' the March Hare said to Alice, very*
+ earnestly.*
+ #
+ `I've had nothing yet,' Alice replied in an offended tone, `so*
+ I can't take more.'*
+ #
+ `You mean you can't take LESS,' said the Hatter: `it's very*
+ easy to take MORE than nothing.'#
+
+
+
+
+
+
+
+
+
+Gellens Standards Track [Page 10]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ To show an example of quoting, here we have the same exchange,
+ presented as a series of direct quotes:
+
+ >>>Take some more tea.#
+ >>I've had nothing yet, so I can't take more.#
+ >You mean you can't take LESS, it's very easy to take*
+ >MORE than nothing.#
+
+5. ABNF
+
+ The constructs used in Text/Plain; Format=Flowed body parts are
+ described using [ABNF], including the Core Rules:
+
+ paragraph = 1*flowed-line fixed-line
+ fixed-line = fixed / sig-sep
+ fixed = [quote] [stuffing] *text-char non-sp CRLF
+ flowed-line = flow-qt / flow-unqt
+ flow-qt = quote [stuffing] *text-char 1*SP CRLF
+ flow-unqt = [stuffing] *text-char 1*SP CRLF
+ non-sp = %x01-09 / %x0B / %x0C / %x0E-1F / %x21-7F
+ ; any 7-bit US-ASCII character, excluding
+ ; NUL, CR, LF, and SP
+ quote = 1*">"
+ sig-sep = [quote] "--" SP CRLF
+ stuffing = [SP] ; space-stuffed, added on generation if
+ ; needed, deleted on reception
+ text-char = non-sp / SP
+
+6. Failure Modes
+
+6.1. Trailing White Space Corruption
+
+ There are systems in existence which alter trailing whitespace on
+ messages which pass through them. Such systems may strip, or in
+ rarer cases, add trailing whitespace, in violation of RFC 821 [SMTP]
+ section 4.5.2.
+
+ Stripping trailing whitespace has the effect of converting flowed
+ lines to fixed lines, which results in a message no worse than if
+ Format=Flowed had not been used.
+
+ Adding trailing whitespace to a Format=Flowed message may result in a
+ malformed display or reply.
+
+ Since most systems which add trailing white space do so to create a
+ line which fills an internal record format, the result is almost
+ always a line which contains an even number of characters (counting
+ the added trailing white space).
+
+
+
+Gellens Standards Track [Page 11]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ One possible avoidance, therefore, would be to define Format=Flowed
+ lines to use either one or two trailing space characters to indicate
+ a flowed line, such that the total line length is odd. However,
+ considering the scarcity of such systems today, it is not worth the
+ added complexity.
+
+7. Security Considerations
+
+ This parameter introduces no security considerations beyond those
+ which apply to Text/Plain.
+
+ Section 4.6 discusses the interaction between Format=Flowed and
+ digital signatures or encryption.
+
+8. IANA Considerations
+
+ IANA is requested to add a reference to this specification in the
+ Text/Plain Media Type registration.
+
+9. Internationalization Considerations
+
+ The line wrap and quoting specifications of Format=Flowed may not be
+ suitable for certain charsets, such as for Arabic and Hebrew
+ characters that read from right to left. Care should be taken in
+ applying format=flowed in these cases, as format=fixed combined with
+ quoted-printable encoding may be more suitable.
+
+10. Acknowledgments
+
+ This proposal evolved from a discussion of Chris Newman's
+ Text/Paragraph draft which took place on the IETF 822 mailing list.
+ Special thanks to Ian Bell, Steve Dorner, Brian Kelley, Dan Kohn,
+ Laurence Lundblade, and Dan Wing for their reviews, comments,
+ suggestions, and discussions.
+
+11. References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November
+ 1997.
+
+ [KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RICH] Resnick, P. and A. Walker, "The text/enriched MIME
+ Content-type", RFC 1896, February 1996.
+
+
+
+
+
+Gellens Standards Track [Page 12]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+ [MIME-IMT] Freed, N. and N. Borenstein, "Multipurpose
+ Internet Mail Extensions (MIME) Part Two: Media
+ Types", RFC 2046, November 1996.
+
+ [Quoted-Printable] Freed, N. and N. Borenstein, "Multipurpose
+ Internet Mail Extensions (MIME) Part One: Format
+ of Internet Message Bodies", RFC 2045, November
+ 1996.
+
+ [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD
+ 10, RFC 821, August 1982.
+
+ [HTML] Berners-Lee, T. and D. Connolly, "Hypertext Markup
+ Language -- 2.0", RFC 1866, November 1995.
+
+
+12. Editor's Address
+
+ Randall Gellens
+ QUALCOMM Incorporated
+ 5775 Morehouse Dr.
+ San Diego, CA 92121-2779
+ USA
+
+ Phone: +1 619 651 5115
+ EMail: randy@qualcomm.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gellens Standards Track [Page 13]
+
+RFC 2646 The Text/Plain Format Parameter August 1999
+
+
+13. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
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+Network Working Group J. Klensin, Editor
+Request for Comments: 2821 AT&T Laboratories
+Obsoletes: 821, 974, 1869 April 2001
+Updates: 1123
+Category: Standards Track
+
+
+ Simple Mail Transfer Protocol
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+Abstract
+
+ This document is a self-contained specification of the basic protocol
+ for the Internet electronic mail transport. It consolidates, updates
+ and clarifies, but doesn't add new or change existing functionality
+ of the following:
+
+ - the original SMTP (Simple Mail Transfer Protocol) specification of
+ RFC 821 [30],
+
+ - domain name system requirements and implications for mail
+ transport from RFC 1035 [22] and RFC 974 [27],
+
+ - the clarifications and applicability statements in RFC 1123 [2],
+ and
+
+ - material drawn from the SMTP Extension mechanisms [19].
+
+ It obsoletes RFC 821, RFC 974, and updates RFC 1123 (replaces the
+ mail transport materials of RFC 1123). However, RFC 821 specifies
+ some features that were not in significant use in the Internet by the
+ mid-1990s and (in appendices) some additional transport models.
+ Those sections are omitted here in the interest of clarity and
+ brevity; readers needing them should refer to RFC 821.
+
+
+
+
+
+
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+RFC 2821 Simple Mail Transfer Protocol April 2001
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+
+ It also includes some additional material from RFC 1123 that required
+ amplification. This material has been identified in multiple ways,
+ mostly by tracking flaming on various lists and newsgroups and
+ problems of unusual readings or interpretations that have appeared as
+ the SMTP extensions have been deployed. Where this specification
+ moves beyond consolidation and actually differs from earlier
+ documents, it supersedes them technically as well as textually.
+
+ Although SMTP was designed as a mail transport and delivery protocol,
+ this specification also contains information that is important to its
+ use as a 'mail submission' protocol, as recommended for POP [3, 26]
+ and IMAP [6]. Additional submission issues are discussed in RFC 2476
+ [15].
+
+ Section 2.3 provides definitions of terms specific to this document.
+ Except when the historical terminology is necessary for clarity, this
+ document uses the current 'client' and 'server' terminology to
+ identify the sending and receiving SMTP processes, respectively.
+
+ A companion document [32] discusses message headers, message bodies
+ and formats and structures for them, and their relationship.
+
+Table of Contents
+
+ 1. Introduction .................................................. 4
+ 2. The SMTP Model ................................................ 5
+ 2.1 Basic Structure .............................................. 5
+ 2.2 The Extension Model .......................................... 7
+ 2.2.1 Background ................................................. 7
+ 2.2.2 Definition and Registration of Extensions .................. 8
+ 2.3 Terminology .................................................. 9
+ 2.3.1 Mail Objects ............................................... 10
+ 2.3.2 Senders and Receivers ...................................... 10
+ 2.3.3 Mail Agents and Message Stores ............................. 10
+ 2.3.4 Host ....................................................... 11
+ 2.3.5 Domain ..................................................... 11
+ 2.3.6 Buffer and State Table ..................................... 11
+ 2.3.7 Lines ...................................................... 12
+ 2.3.8 Originator, Delivery, Relay, and Gateway Systems ........... 12
+ 2.3.9 Message Content and Mail Data .............................. 13
+ 2.3.10 Mailbox and Address ....................................... 13
+ 2.3.11 Reply ..................................................... 13
+ 2.4 General Syntax Principles and Transaction Model .............. 13
+ 3. The SMTP Procedures: An Overview .............................. 15
+ 3.1 Session Initiation ........................................... 15
+ 3.2 Client Initiation ............................................ 16
+ 3.3 Mail Transactions ............................................ 16
+ 3.4 Forwarding for Address Correction or Updating ................ 19
+
+
+
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+
+ 3.5 Commands for Debugging Addresses ............................. 20
+ 3.5.1 Overview ................................................... 20
+ 3.5.2 VRFY Normal Response ....................................... 22
+ 3.5.3 Meaning of VRFY or EXPN Success Response ................... 22
+ 3.5.4 Semantics and Applications of EXPN ......................... 23
+ 3.6 Domains ...................................................... 23
+ 3.7 Relaying ..................................................... 24
+ 3.8 Mail Gatewaying .............................................. 25
+ 3.8.1 Header Fields in Gatewaying ................................ 26
+ 3.8.2 Received Lines in Gatewaying ............................... 26
+ 3.8.3 Addresses in Gatewaying .................................... 26
+ 3.8.4 Other Header Fields in Gatewaying .......................... 27
+ 3.8.5 Envelopes in Gatewaying .................................... 27
+ 3.9 Terminating Sessions and Connections ......................... 27
+ 3.10 Mailing Lists and Aliases ................................... 28
+ 3.10.1 Alias ..................................................... 28
+ 3.10.2 List ...................................................... 28
+ 4. The SMTP Specifications ....................................... 29
+ 4.1 SMTP Commands ................................................ 29
+ 4.1.1 Command Semantics and Syntax ............................... 29
+ 4.1.1.1 Extended HELLO (EHLO) or HELLO (HELO) ................... 29
+ 4.1.1.2 MAIL (MAIL) .............................................. 31
+ 4.1.1.3 RECIPIENT (RCPT) ......................................... 31
+ 4.1.1.4 DATA (DATA) .............................................. 33
+ 4.1.1.5 RESET (RSET) ............................................. 34
+ 4.1.1.6 VERIFY (VRFY) ............................................ 35
+ 4.1.1.7 EXPAND (EXPN) ............................................ 35
+ 4.1.1.8 HELP (HELP) .............................................. 35
+ 4.1.1.9 NOOP (NOOP) .............................................. 35
+ 4.1.1.10 QUIT (QUIT) ............................................. 36
+ 4.1.2 Command Argument Syntax .................................... 36
+ 4.1.3 Address Literals ........................................... 38
+ 4.1.4 Order of Commands .......................................... 39
+ 4.1.5 Private-use Commands ....................................... 40
+ 4.2 SMTP Replies ................................................ 40
+ 4.2.1 Reply Code Severities and Theory ........................... 42
+ 4.2.2 Reply Codes by Function Groups ............................. 44
+ 4.2.3 Reply Codes in Numeric Order .............................. 45
+ 4.2.4 Reply Code 502 ............................................. 46
+ 4.2.5 Reply Codes After DATA and the Subsequent <CRLF>.<CRLF> .... 46
+ 4.3 Sequencing of Commands and Replies ........................... 47
+ 4.3.1 Sequencing Overview ........................................ 47
+ 4.3.2 Command-Reply Sequences .................................... 48
+ 4.4 Trace Information ............................................ 49
+ 4.5 Additional Implementation Issues ............................. 53
+ 4.5.1 Minimum Implementation ..................................... 53
+ 4.5.2 Transparency ............................................... 53
+ 4.5.3 Sizes and Timeouts ......................................... 54
+
+
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+ 4.5.3.1 Size limits and minimums ................................. 54
+ 4.5.3.2 Timeouts ................................................. 56
+ 4.5.4 Retry Strategies ........................................... 57
+ 4.5.4.1 Sending Strategy ......................................... 58
+ 4.5.4.2 Receiving Strategy ....................................... 59
+ 4.5.5 Messages with a null reverse-path .......................... 59
+ 5. Address Resolution and Mail Handling .......................... 60
+ 6. Problem Detection and Handling ................................ 62
+ 6.1 Reliable Delivery and Replies by Email ....................... 62
+ 6.2 Loop Detection ............................................... 63
+ 6.3 Compensating for Irregularities .............................. 63
+ 7. Security Considerations ....................................... 64
+ 7.1 Mail Security and Spoofing ................................... 64
+ 7.2 "Blind" Copies ............................................... 65
+ 7.3 VRFY, EXPN, and Security ..................................... 65
+ 7.4 Information Disclosure in Announcements ...................... 66
+ 7.5 Information Disclosure in Trace Fields ....................... 66
+ 7.6 Information Disclosure in Message Forwarding ................. 67
+ 7.7 Scope of Operation of SMTP Servers ........................... 67
+ 8. IANA Considerations ........................................... 67
+ 9. References .................................................... 68
+ 10. Editor's Address ............................................. 70
+ 11. Acknowledgments .............................................. 70
+ Appendices ....................................................... 71
+ A. TCP Transport Service ......................................... 71
+ B. Generating SMTP Commands from RFC 822 Headers ................. 71
+ C. Source Routes ................................................. 72
+ D. Scenarios ..................................................... 73
+ E. Other Gateway Issues .......................................... 76
+ F. Deprecated Features of RFC 821 ................................ 76
+ Full Copyright Statement ......................................... 79
+
+1. Introduction
+
+ The objective of the Simple Mail Transfer Protocol (SMTP) is to
+ transfer mail reliably and efficiently.
+
+ SMTP is independent of the particular transmission subsystem and
+ requires only a reliable ordered data stream channel. While this
+ document specifically discusses transport over TCP, other transports
+ are possible. Appendices to RFC 821 describe some of them.
+
+ An important feature of SMTP is its capability to transport mail
+ across networks, usually referred to as "SMTP mail relaying" (see
+ section 3.8). A network consists of the mutually-TCP-accessible
+ hosts on the public Internet, the mutually-TCP-accessible hosts on a
+ firewall-isolated TCP/IP Intranet, or hosts in some other LAN or WAN
+ environment utilizing a non-TCP transport-level protocol. Using
+
+
+
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+RFC 2821 Simple Mail Transfer Protocol April 2001
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+ SMTP, a process can transfer mail to another process on the same
+ network or to some other network via a relay or gateway process
+ accessible to both networks.
+
+ In this way, a mail message may pass through a number of intermediate
+ relay or gateway hosts on its path from sender to ultimate recipient.
+ The Mail eXchanger mechanisms of the domain name system [22, 27] (and
+ section 5 of this document) are used to identify the appropriate
+ next-hop destination for a message being transported.
+
+2. The SMTP Model
+
+2.1 Basic Structure
+
+ The SMTP design can be pictured as:
+
+ +----------+ +----------+
+ +------+ | | | |
+ | User |<-->| | SMTP | |
+ +------+ | Client- |Commands/Replies| Server- |
+ +------+ | SMTP |<-------------->| SMTP | +------+
+ | File |<-->| | and Mail | |<-->| File |
+ |System| | | | | |System|
+ +------+ +----------+ +----------+ +------+
+ SMTP client SMTP server
+
+ When an SMTP client has a message to transmit, it establishes a two-
+ way transmission channel to an SMTP server. The responsibility of an
+ SMTP client is to transfer mail messages to one or more SMTP servers,
+ or report its failure to do so.
+
+ The means by which a mail message is presented to an SMTP client, and
+ how that client determines the domain name(s) to which mail messages
+ are to be transferred is a local matter, and is not addressed by this
+ document. In some cases, the domain name(s) transferred to, or
+ determined by, an SMTP client will identify the final destination(s)
+ of the mail message. In other cases, common with SMTP clients
+ associated with implementations of the POP [3, 26] or IMAP [6]
+ protocols, or when the SMTP client is inside an isolated transport
+ service environment, the domain name determined will identify an
+ intermediate destination through which all mail messages are to be
+ relayed. SMTP clients that transfer all traffic, regardless of the
+ target domain names associated with the individual messages, or that
+ do not maintain queues for retrying message transmissions that
+ initially cannot be completed, may otherwise conform to this
+ specification but are not considered fully-capable. Fully-capable
+ SMTP implementations, including the relays used by these less capable
+
+
+
+
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+
+ ones, and their destinations, are expected to support all of the
+ queuing, retrying, and alternate address functions discussed in this
+ specification.
+
+ The means by which an SMTP client, once it has determined a target
+ domain name, determines the identity of an SMTP server to which a
+ copy of a message is to be transferred, and then performs that
+ transfer, is covered by this document. To effect a mail transfer to
+ an SMTP server, an SMTP client establishes a two-way transmission
+ channel to that SMTP server. An SMTP client determines the address
+ of an appropriate host running an SMTP server by resolving a
+ destination domain name to either an intermediate Mail eXchanger host
+ or a final target host.
+
+ An SMTP server may be either the ultimate destination or an
+ intermediate "relay" (that is, it may assume the role of an SMTP
+ client after receiving the message) or "gateway" (that is, it may
+ transport the message further using some protocol other than SMTP).
+ SMTP commands are generated by the SMTP client and sent to the SMTP
+ server. SMTP replies are sent from the SMTP server to the SMTP
+ client in response to the commands.
+
+ In other words, message transfer can occur in a single connection
+ between the original SMTP-sender and the final SMTP-recipient, or can
+ occur in a series of hops through intermediary systems. In either
+ case, a formal handoff of responsibility for the message occurs: the
+ protocol requires that a server accept responsibility for either
+ delivering a message or properly reporting the failure to do so.
+
+ Once the transmission channel is established and initial handshaking
+ completed, the SMTP client normally initiates a mail transaction.
+ Such a transaction consists of a series of commands to specify the
+ originator and destination of the mail and transmission of the
+ message content (including any headers or other structure) itself.
+ When the same message is sent to multiple recipients, this protocol
+ encourages the transmission of only one copy of the data for all
+ recipients at the same destination (or intermediate relay) host.
+
+ The server responds to each command with a reply; replies may
+ indicate that the command was accepted, that additional commands are
+ expected, or that a temporary or permanent error condition exists.
+ Commands specifying the sender or recipients may include server-
+ permitted SMTP service extension requests as discussed in section
+ 2.2. The dialog is purposely lock-step, one-at-a-time, although this
+ can be modified by mutually-agreed extension requests such as command
+ pipelining [13].
+
+
+
+
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+ Once a given mail message has been transmitted, the client may either
+ request that the connection be shut down or may initiate other mail
+ transactions. In addition, an SMTP client may use a connection to an
+ SMTP server for ancillary services such as verification of email
+ addresses or retrieval of mailing list subscriber addresses.
+
+ As suggested above, this protocol provides mechanisms for the
+ transmission of mail. This transmission normally occurs directly
+ from the sending user's host to the receiving user's host when the
+ two hosts are connected to the same transport service. When they are
+ not connected to the same transport service, transmission occurs via
+ one or more relay SMTP servers. An intermediate host that acts as
+ either an SMTP relay or as a gateway into some other transmission
+ environment is usually selected through the use of the domain name
+ service (DNS) Mail eXchanger mechanism.
+
+ Usually, intermediate hosts are determined via the DNS MX record, not
+ by explicit "source" routing (see section 5 and appendices C and
+ F.2).
+
+2.2 The Extension Model
+
+2.2.1 Background
+
+ In an effort that started in 1990, approximately a decade after RFC
+ 821 was completed, the protocol was modified with a "service
+ extensions" model that permits the client and server to agree to
+ utilize shared functionality beyond the original SMTP requirements.
+ The SMTP extension mechanism defines a means whereby an extended SMTP
+ client and server may recognize each other, and the server can inform
+ the client as to the service extensions that it supports.
+
+ Contemporary SMTP implementations MUST support the basic extension
+ mechanisms. For instance, servers MUST support the EHLO command even
+ if they do not implement any specific extensions and clients SHOULD
+ preferentially utilize EHLO rather than HELO. (However, for
+ compatibility with older conforming implementations, SMTP clients and
+ servers MUST support the original HELO mechanisms as a fallback.)
+ Unless the different characteristics of HELO must be identified for
+ interoperability purposes, this document discusses only EHLO.
+
+ SMTP is widely deployed and high-quality implementations have proven
+ to be very robust. However, the Internet community now considers
+ some services to be important that were not anticipated when the
+ protocol was first designed. If support for those services is to be
+ added, it must be done in a way that permits older implementations to
+ continue working acceptably. The extension framework consists of:
+
+
+
+
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+
+ - The SMTP command EHLO, superseding the earlier HELO,
+
+ - a registry of SMTP service extensions,
+
+ - additional parameters to the SMTP MAIL and RCPT commands, and
+
+ - optional replacements for commands defined in this protocol, such
+ as for DATA in non-ASCII transmissions [33].
+
+ SMTP's strength comes primarily from its simplicity. Experience with
+ many protocols has shown that protocols with few options tend towards
+ ubiquity, whereas protocols with many options tend towards obscurity.
+
+ Each and every extension, regardless of its benefits, must be
+ carefully scrutinized with respect to its implementation, deployment,
+ and interoperability costs. In many cases, the cost of extending the
+ SMTP service will likely outweigh the benefit.
+
+2.2.2 Definition and Registration of Extensions
+
+ The IANA maintains a registry of SMTP service extensions. A
+ corresponding EHLO keyword value is associated with each extension.
+ Each service extension registered with the IANA must be defined in a
+ formal standards-track or IESG-approved experimental protocol
+ document. The definition must include:
+
+ - the textual name of the SMTP service extension;
+
+ - the EHLO keyword value associated with the extension;
+
+ - the syntax and possible values of parameters associated with the
+ EHLO keyword value;
+
+ - any additional SMTP verbs associated with the extension
+ (additional verbs will usually be, but are not required to be, the
+ same as the EHLO keyword value);
+
+ - any new parameters the extension associates with the MAIL or RCPT
+ verbs;
+
+ - a description of how support for the extension affects the
+ behavior of a server and client SMTP; and,
+
+ - the increment by which the extension is increasing the maximum
+ length of the commands MAIL and/or RCPT, over that specified in
+ this standard.
+
+
+
+
+
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+
+ In addition, any EHLO keyword value starting with an upper or lower
+ case "X" refers to a local SMTP service extension used exclusively
+ through bilateral agreement. Keywords beginning with "X" MUST NOT be
+ used in a registered service extension. Conversely, keyword values
+ presented in the EHLO response that do not begin with "X" MUST
+ correspond to a standard, standards-track, or IESG-approved
+ experimental SMTP service extension registered with IANA. A
+ conforming server MUST NOT offer non-"X"-prefixed keyword values that
+ are not described in a registered extension.
+
+ Additional verbs and parameter names are bound by the same rules as
+ EHLO keywords; specifically, verbs beginning with "X" are local
+ extensions that may not be registered or standardized. Conversely,
+ verbs not beginning with "X" must always be registered.
+
+2.3 Terminology
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described below.
+
+ 1. MUST This word, or the terms "REQUIRED" or "SHALL", mean that
+ the definition is an absolute requirement of the specification.
+
+ 2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the
+ definition is an absolute prohibition of the specification.
+
+ 3. SHOULD This word, or the adjective "RECOMMENDED", mean that
+ there may exist valid reasons in particular circumstances to
+ ignore a particular item, but the full implications must be
+ understood and carefully weighed before choosing a different
+ course.
+
+ 4. SHOULD NOT This phrase, or the phrase "NOT RECOMMENDED" mean
+ that there may exist valid reasons in particular circumstances
+ when the particular behavior is acceptable or even useful, but the
+ full implications should be understood and the case carefully
+ weighed before implementing any behavior described with this
+ label.
+
+ 5. MAY This word, or the adjective "OPTIONAL", mean that an item is
+ truly optional. One vendor may choose to include the item because
+ a particular marketplace requires it or because the vendor feels
+ that it enhances the product while another vendor may omit the
+ same item. An implementation which does not include a particular
+ option MUST be prepared to interoperate with another
+ implementation which does include the option, though perhaps with
+ reduced functionality. In the same vein an implementation which
+
+
+
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+ does include a particular option MUST be prepared to interoperate
+ with another implementation which does not include the option
+ (except, of course, for the feature the option provides.)
+
+2.3.1 Mail Objects
+
+ SMTP transports a mail object. A mail object contains an envelope
+ and content.
+
+ The SMTP envelope is sent as a series of SMTP protocol units
+ (described in section 3). It consists of an originator address (to
+ which error reports should be directed); one or more recipient
+ addresses; and optional protocol extension material. Historically,
+ variations on the recipient address specification command (RCPT TO)
+ could be used to specify alternate delivery modes, such as immediate
+ display; those variations have now been deprecated (see appendix F,
+ section F.6).
+
+ The SMTP content is sent in the SMTP DATA protocol unit and has two
+ parts: the headers and the body. If the content conforms to other
+ contemporary standards, the headers form a collection of field/value
+ pairs structured as in the message format specification [32]; the
+ body, if structured, is defined according to MIME [12]. The content
+ is textual in nature, expressed using the US-ASCII repertoire [1].
+ Although SMTP extensions (such as "8BITMIME" [20]) may relax this
+ restriction for the content body, the content headers are always
+ encoded using the US-ASCII repertoire. A MIME extension [23] defines
+ an algorithm for representing header values outside the US-ASCII
+ repertoire, while still encoding them using the US-ASCII repertoire.
+
+2.3.2 Senders and Receivers
+
+ In RFC 821, the two hosts participating in an SMTP transaction were
+ described as the "SMTP-sender" and "SMTP-receiver". This document
+ has been changed to reflect current industry terminology and hence
+ refers to them as the "SMTP client" (or sometimes just "the client")
+ and "SMTP server" (or just "the server"), respectively. Since a
+ given host may act both as server and client in a relay situation,
+ "receiver" and "sender" terminology is still used where needed for
+ clarity.
+
+2.3.3 Mail Agents and Message Stores
+
+ Additional mail system terminology became common after RFC 821 was
+ published and, where convenient, is used in this specification. In
+ particular, SMTP servers and clients provide a mail transport service
+ and therefore act as "Mail Transfer Agents" (MTAs). "Mail User
+ Agents" (MUAs or UAs) are normally thought of as the sources and
+
+
+
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+ targets of mail. At the source, an MUA might collect mail to be
+ transmitted from a user and hand it off to an MTA; the final
+ ("delivery") MTA would be thought of as handing the mail off to an
+ MUA (or at least transferring responsibility to it, e.g., by
+ depositing the message in a "message store"). However, while these
+ terms are used with at least the appearance of great precision in
+ other environments, the implied boundaries between MUAs and MTAs
+ often do not accurately match common, and conforming, practices with
+ Internet mail. Hence, the reader should be cautious about inferring
+ the strong relationships and responsibilities that might be implied
+ if these terms were used elsewhere.
+
+2.3.4 Host
+
+ For the purposes of this specification, a host is a computer system
+ attached to the Internet (or, in some cases, to a private TCP/IP
+ network) and supporting the SMTP protocol. Hosts are known by names
+ (see "domain"); identifying them by numerical address is discouraged.
+
+2.3.5 Domain
+
+ A domain (or domain name) consists of one or more dot-separated
+ components. These components ("labels" in DNS terminology [22]) are
+ restricted for SMTP purposes to consist of a sequence of letters,
+ digits, and hyphens drawn from the ASCII character set [1]. Domain
+ names are used as names of hosts and of other entities in the domain
+ name hierarchy. For example, a domain may refer to an alias (label
+ of a CNAME RR) or the label of Mail eXchanger records to be used to
+ deliver mail instead of representing a host name. See [22] and
+ section 5 of this specification.
+
+ The domain name, as described in this document and in [22], is the
+ entire, fully-qualified name (often referred to as an "FQDN"). A
+ domain name that is not in FQDN form is no more than a local alias.
+ Local aliases MUST NOT appear in any SMTP transaction.
+
+2.3.6 Buffer and State Table
+
+ SMTP sessions are stateful, with both parties carefully maintaining a
+ common view of the current state. In this document we model this
+ state by a virtual "buffer" and a "state table" on the server which
+ may be used by the client to, for example, "clear the buffer" or
+ "reset the state table," causing the information in the buffer to be
+ discarded and the state to be returned to some previous state.
+
+
+
+
+
+
+
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+2.3.7 Lines
+
+ SMTP commands and, unless altered by a service extension, message
+ data, are transmitted in "lines". Lines consist of zero or more data
+ characters terminated by the sequence ASCII character "CR" (hex value
+ 0D) followed immediately by ASCII character "LF" (hex value 0A).
+ This termination sequence is denoted as <CRLF> in this document.
+ Conforming implementations MUST NOT recognize or generate any other
+ character or character sequence as a line terminator. Limits MAY be
+ imposed on line lengths by servers (see section 4.5.3).
+
+ In addition, the appearance of "bare" "CR" or "LF" characters in text
+ (i.e., either without the other) has a long history of causing
+ problems in mail implementations and applications that use the mail
+ system as a tool. SMTP client implementations MUST NOT transmit
+ these characters except when they are intended as line terminators
+ and then MUST, as indicated above, transmit them only as a <CRLF>
+ sequence.
+
+2.3.8 Originator, Delivery, Relay, and Gateway Systems
+
+ This specification makes a distinction among four types of SMTP
+ systems, based on the role those systems play in transmitting
+ electronic mail. An "originating" system (sometimes called an SMTP
+ originator) introduces mail into the Internet or, more generally,
+ into a transport service environment. A "delivery" SMTP system is
+ one that receives mail from a transport service environment and
+ passes it to a mail user agent or deposits it in a message store
+ which a mail user agent is expected to subsequently access. A
+ "relay" SMTP system (usually referred to just as a "relay") receives
+ mail from an SMTP client and transmits it, without modification to
+ the message data other than adding trace information, to another SMTP
+ server for further relaying or for delivery.
+
+ A "gateway" SMTP system (usually referred to just as a "gateway")
+ receives mail from a client system in one transport environment and
+ transmits it to a server system in another transport environment.
+ Differences in protocols or message semantics between the transport
+ environments on either side of a gateway may require that the gateway
+ system perform transformations to the message that are not permitted
+ to SMTP relay systems. For the purposes of this specification,
+ firewalls that rewrite addresses should be considered as gateways,
+ even if SMTP is used on both sides of them (see [11]).
+
+
+
+
+
+
+
+
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+
+
+2.3.9 Message Content and Mail Data
+
+ The terms "message content" and "mail data" are used interchangeably
+ in this document to describe the material transmitted after the DATA
+ command is accepted and before the end of data indication is
+ transmitted. Message content includes message headers and the
+ possibly-structured message body. The MIME specification [12]
+ provides the standard mechanisms for structured message bodies.
+
+2.3.10 Mailbox and Address
+
+ As used in this specification, an "address" is a character string
+ that identifies a user to whom mail will be sent or a location into
+ which mail will be deposited. The term "mailbox" refers to that
+ depository. The two terms are typically used interchangeably unless
+ the distinction between the location in which mail is placed (the
+ mailbox) and a reference to it (the address) is important. An
+ address normally consists of user and domain specifications. The
+ standard mailbox naming convention is defined to be "local-
+ part@domain": contemporary usage permits a much broader set of
+ applications than simple "user names". Consequently, and due to a
+ long history of problems when intermediate hosts have attempted to
+ optimize transport by modifying them, the local-part MUST be
+ interpreted and assigned semantics only by the host specified in the
+ domain part of the address.
+
+2.3.11 Reply
+
+ An SMTP reply is an acknowledgment (positive or negative) sent from
+ receiver to sender via the transmission channel in response to a
+ command. The general form of a reply is a numeric completion code
+ (indicating failure or success) usually followed by a text string.
+ The codes are for use by programs and the text is usually intended
+ for human users. Recent work [34] has specified further structuring
+ of the reply strings, including the use of supplemental and more
+ specific completion codes.
+
+2.4 General Syntax Principles and Transaction Model
+
+ SMTP commands and replies have a rigid syntax. All commands begin
+ with a command verb. All Replies begin with a three digit numeric
+ code. In some commands and replies, arguments MUST follow the verb
+ or reply code. Some commands do not accept arguments (after the
+ verb), and some reply codes are followed, sometimes optionally, by
+ free form text. In both cases, where text appears, it is separated
+ from the verb or reply code by a space character. Complete
+ definitions of commands and replies appear in section 4.
+
+
+
+
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+
+
+ Verbs and argument values (e.g., "TO:" or "to:" in the RCPT command
+ and extension name keywords) are not case sensitive, with the sole
+ exception in this specification of a mailbox local-part (SMTP
+ Extensions may explicitly specify case-sensitive elements). That is,
+ a command verb, an argument value other than a mailbox local-part,
+ and free form text MAY be encoded in upper case, lower case, or any
+ mixture of upper and lower case with no impact on its meaning. This
+ is NOT true of a mailbox local-part. The local-part of a mailbox
+ MUST BE treated as case sensitive. Therefore, SMTP implementations
+ MUST take care to preserve the case of mailbox local-parts. Mailbox
+ domains are not case sensitive. In particular, for some hosts the
+ user "smith" is different from the user "Smith". However, exploiting
+ the case sensitivity of mailbox local-parts impedes interoperability
+ and is discouraged.
+
+ A few SMTP servers, in violation of this specification (and RFC 821)
+ require that command verbs be encoded by clients in upper case.
+ Implementations MAY wish to employ this encoding to accommodate those
+ servers.
+
+ The argument field consists of a variable length character string
+ ending with the end of the line, i.e., with the character sequence
+ <CRLF>. The receiver will take no action until this sequence is
+ received.
+
+ The syntax for each command is shown with the discussion of that
+ command. Common elements and parameters are shown in section 4.1.2.
+
+ Commands and replies are composed of characters from the ASCII
+ character set [1]. When the transport service provides an 8-bit byte
+ (octet) transmission channel, each 7-bit character is transmitted
+ right justified in an octet with the high order bit cleared to zero.
+ More specifically, the unextended SMTP service provides seven bit
+ transport only. An originating SMTP client which has not
+ successfully negotiated an appropriate extension with a particular
+ server MUST NOT transmit messages with information in the high-order
+ bit of octets. If such messages are transmitted in violation of this
+ rule, receiving SMTP servers MAY clear the high-order bit or reject
+ the message as invalid. In general, a relay SMTP SHOULD assume that
+ the message content it has received is valid and, assuming that the
+ envelope permits doing so, relay it without inspecting that content.
+ Of course, if the content is mislabeled and the data path cannot
+ accept the actual content, this may result in ultimate delivery of a
+ severely garbled message to the recipient. Delivery SMTP systems MAY
+ reject ("bounce") such messages rather than deliver them. No sending
+ SMTP system is permitted to send envelope commands in any character
+
+
+
+
+
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+
+
+ set other than US-ASCII; receiving systems SHOULD reject such
+ commands, normally using "500 syntax error - invalid character"
+ replies.
+
+ Eight-bit message content transmission MAY be requested of the server
+ by a client using extended SMTP facilities, notably the "8BITMIME"
+ extension [20]. 8BITMIME SHOULD be supported by SMTP servers.
+ However, it MUST not be construed as authorization to transmit
+ unrestricted eight bit material. 8BITMIME MUST NOT be requested by
+ senders for material with the high bit on that is not in MIME format
+ with an appropriate content-transfer encoding; servers MAY reject
+ such messages.
+
+ The metalinguistic notation used in this document corresponds to the
+ "Augmented BNF" used in other Internet mail system documents. The
+ reader who is not familiar with that syntax should consult the ABNF
+ specification [8]. Metalanguage terms used in running text are
+ surrounded by pointed brackets (e.g., <CRLF>) for clarity.
+
+3. The SMTP Procedures: An Overview
+
+ This section contains descriptions of the procedures used in SMTP:
+ session initiation, the mail transaction, forwarding mail, verifying
+ mailbox names and expanding mailing lists, and the opening and
+ closing exchanges. Comments on relaying, a note on mail domains, and
+ a discussion of changing roles are included at the end of this
+ section. Several complete scenarios are presented in appendix D.
+
+3.1 Session Initiation
+
+ An SMTP session is initiated when a client opens a connection to a
+ server and the server responds with an opening message.
+
+ SMTP server implementations MAY include identification of their
+ software and version information in the connection greeting reply
+ after the 220 code, a practice that permits more efficient isolation
+ and repair of any problems. Implementations MAY make provision for
+ SMTP servers to disable the software and version announcement where
+ it causes security concerns. While some systems also identify their
+ contact point for mail problems, this is not a substitute for
+ maintaining the required "postmaster" address (see section 4.5.1).
+
+ The SMTP protocol allows a server to formally reject a transaction
+ while still allowing the initial connection as follows: a 554
+ response MAY be given in the initial connection opening message
+ instead of the 220. A server taking this approach MUST still wait
+ for the client to send a QUIT (see section 4.1.1.10) before closing
+ the connection and SHOULD respond to any intervening commands with
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ "503 bad sequence of commands". Since an attempt to make an SMTP
+ connection to such a system is probably in error, a server returning
+ a 554 response on connection opening SHOULD provide enough
+ information in the reply text to facilitate debugging of the sending
+ system.
+
+3.2 Client Initiation
+
+ Once the server has sent the welcoming message and the client has
+ received it, the client normally sends the EHLO command to the
+ server, indicating the client's identity. In addition to opening the
+ session, use of EHLO indicates that the client is able to process
+ service extensions and requests that the server provide a list of the
+ extensions it supports. Older SMTP systems which are unable to
+ support service extensions and contemporary clients which do not
+ require service extensions in the mail session being initiated, MAY
+ use HELO instead of EHLO. Servers MUST NOT return the extended
+ EHLO-style response to a HELO command. For a particular connection
+ attempt, if the server returns a "command not recognized" response to
+ EHLO, the client SHOULD be able to fall back and send HELO.
+
+ In the EHLO command the host sending the command identifies itself;
+ the command may be interpreted as saying "Hello, I am <domain>" (and,
+ in the case of EHLO, "and I support service extension requests").
+
+3.3 Mail Transactions
+
+ There are three steps to SMTP mail transactions. The transaction
+ starts with a MAIL command which gives the sender identification.
+ (In general, the MAIL command may be sent only when no mail
+ transaction is in progress; see section 4.1.4.) A series of one or
+ more RCPT commands follows giving the receiver information. Then a
+ DATA command initiates transfer of the mail data and is terminated by
+ the "end of mail" data indicator, which also confirms the
+ transaction.
+
+ The first step in the procedure is the MAIL command.
+
+ MAIL FROM:<reverse-path> [SP <mail-parameters> ] <CRLF>
+
+ This command tells the SMTP-receiver that a new mail transaction is
+ starting and to reset all its state tables and buffers, including any
+ recipients or mail data. The <reverse-path> portion of the first or
+ only argument contains the source mailbox (between "<" and ">"
+ brackets), which can be used to report errors (see section 4.2 for a
+ discussion of error reporting). If accepted, the SMTP server returns
+ a 250 OK reply. If the mailbox specification is not acceptable for
+ some reason, the server MUST return a reply indicating whether the
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ failure is permanent (i.e., will occur again if the client tries to
+ send the same address again) or temporary (i.e., the address might be
+ accepted if the client tries again later). Despite the apparent
+ scope of this requirement, there are circumstances in which the
+ acceptability of the reverse-path may not be determined until one or
+ more forward-paths (in RCPT commands) can be examined. In those
+ cases, the server MAY reasonably accept the reverse-path (with a 250
+ reply) and then report problems after the forward-paths are received
+ and examined. Normally, failures produce 550 or 553 replies.
+
+ Historically, the <reverse-path> can contain more than just a
+ mailbox, however, contemporary systems SHOULD NOT use source routing
+ (see appendix C).
+
+ The optional <mail-parameters> are associated with negotiated SMTP
+ service extensions (see section 2.2).
+
+ The second step in the procedure is the RCPT command.
+
+ RCPT TO:<forward-path> [ SP <rcpt-parameters> ] <CRLF>
+
+ The first or only argument to this command includes a forward-path
+ (normally a mailbox and domain, always surrounded by "<" and ">"
+ brackets) identifying one recipient. If accepted, the SMTP server
+ returns a 250 OK reply and stores the forward-path. If the recipient
+ is known not to be a deliverable address, the SMTP server returns a
+ 550 reply, typically with a string such as "no such user - " and the
+ mailbox name (other circumstances and reply codes are possible).
+ This step of the procedure can be repeated any number of times.
+
+ The <forward-path> can contain more than just a mailbox.
+ Historically, the <forward-path> can be a source routing list of
+ hosts and the destination mailbox, however, contemporary SMTP clients
+ SHOULD NOT utilize source routes (see appendix C). Servers MUST be
+ prepared to encounter a list of source routes in the forward path,
+ but SHOULD ignore the routes or MAY decline to support the relaying
+ they imply. Similarly, servers MAY decline to accept mail that is
+ destined for other hosts or systems. These restrictions make a
+ server useless as a relay for clients that do not support full SMTP
+ functionality. Consequently, restricted-capability clients MUST NOT
+ assume that any SMTP server on the Internet can be used as their mail
+ processing (relaying) site. If a RCPT command appears without a
+ previous MAIL command, the server MUST return a 503 "Bad sequence of
+ commands" response. The optional <rcpt-parameters> are associated
+ with negotiated SMTP service extensions (see section 2.2).
+
+ The third step in the procedure is the DATA command (or some
+ alternative specified in a service extension).
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ DATA <CRLF>
+
+ If accepted, the SMTP server returns a 354 Intermediate reply and
+ considers all succeeding lines up to but not including the end of
+ mail data indicator to be the message text. When the end of text is
+ successfully received and stored the SMTP-receiver sends a 250 OK
+ reply.
+
+ Since the mail data is sent on the transmission channel, the end of
+ mail data must be indicated so that the command and reply dialog can
+ be resumed. SMTP indicates the end of the mail data by sending a
+ line containing only a "." (period or full stop). A transparency
+ procedure is used to prevent this from interfering with the user's
+ text (see section 4.5.2).
+
+ The end of mail data indicator also confirms the mail transaction and
+ tells the SMTP server to now process the stored recipients and mail
+ data. If accepted, the SMTP server returns a 250 OK reply. The DATA
+ command can fail at only two points in the protocol exchange:
+
+ - If there was no MAIL, or no RCPT, command, or all such commands
+ were rejected, the server MAY return a "command out of sequence"
+ (503) or "no valid recipients" (554) reply in response to the DATA
+ command. If one of those replies (or any other 5yz reply) is
+ received, the client MUST NOT send the message data; more
+ generally, message data MUST NOT be sent unless a 354 reply is
+ received.
+
+ - If the verb is initially accepted and the 354 reply issued, the
+ DATA command should fail only if the mail transaction was
+ incomplete (for example, no recipients), or if resources were
+ unavailable (including, of course, the server unexpectedly
+ becoming unavailable), or if the server determines that the
+ message should be rejected for policy or other reasons.
+
+ However, in practice, some servers do not perform recipient
+ verification until after the message text is received. These servers
+ SHOULD treat a failure for one or more recipients as a "subsequent
+ failure" and return a mail message as discussed in section 6. Using
+ a "550 mailbox not found" (or equivalent) reply code after the data
+ are accepted makes it difficult or impossible for the client to
+ determine which recipients failed.
+
+ When RFC 822 format [7, 32] is being used, the mail data include the
+ memo header items such as Date, Subject, To, Cc, From. Server SMTP
+ systems SHOULD NOT reject messages based on perceived defects in the
+ RFC 822 or MIME [12] message header or message body. In particular,
+
+
+
+
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+
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+
+
+ they MUST NOT reject messages in which the numbers of Resent-fields
+ do not match or Resent-to appears without Resent-from and/or Resent-
+ date.
+
+ Mail transaction commands MUST be used in the order discussed above.
+
+3.4 Forwarding for Address Correction or Updating
+
+ Forwarding support is most often required to consolidate and simplify
+ addresses within, or relative to, some enterprise and less frequently
+ to establish addresses to link a person's prior address with current
+ one. Silent forwarding of messages (without server notification to
+ the sender), for security or non-disclosure purposes, is common in
+ the contemporary Internet.
+
+ In both the enterprise and the "new address" cases, information
+ hiding (and sometimes security) considerations argue against exposure
+ of the "final" address through the SMTP protocol as a side-effect of
+ the forwarding activity. This may be especially important when the
+ final address may not even be reachable by the sender. Consequently,
+ the "forwarding" mechanisms described in section 3.2 of RFC 821, and
+ especially the 251 (corrected destination) and 551 reply codes from
+ RCPT must be evaluated carefully by implementers and, when they are
+ available, by those configuring systems.
+
+ In particular:
+
+ * Servers MAY forward messages when they are aware of an address
+ change. When they do so, they MAY either provide address-updating
+ information with a 251 code, or may forward "silently" and return
+ a 250 code. But, if a 251 code is used, they MUST NOT assume that
+ the client will actually update address information or even return
+ that information to the user.
+
+ Alternately,
+
+ * Servers MAY reject or bounce messages when they are not
+ deliverable when addressed. When they do so, they MAY either
+ provide address-updating information with a 551 code, or may
+ reject the message as undeliverable with a 550 code and no
+ address-specific information. But, if a 551 code is used, they
+ MUST NOT assume that the client will actually update address
+ information or even return that information to the user.
+
+ SMTP server implementations that support the 251 and/or 551 reply
+ codes are strongly encouraged to provide configuration mechanisms so
+ that sites which conclude that they would undesirably disclose
+ information can disable or restrict their use.
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+3.5 Commands for Debugging Addresses
+
+3.5.1 Overview
+
+ SMTP provides commands to verify a user name or obtain the content of
+ a mailing list. This is done with the VRFY and EXPN commands, which
+ have character string arguments. Implementations SHOULD support VRFY
+ and EXPN (however, see section 3.5.2 and 7.3).
+
+ For the VRFY command, the string is a user name or a user name and
+ domain (see below). If a normal (i.e., 250) response is returned,
+ the response MAY include the full name of the user and MUST include
+ the mailbox of the user. It MUST be in either of the following
+ forms:
+
+ User Name <local-part@domain>
+ local-part@domain
+
+ When a name that is the argument to VRFY could identify more than one
+ mailbox, the server MAY either note the ambiguity or identify the
+ alternatives. In other words, any of the following are legitimate
+ response to VRFY:
+
+ 553 User ambiguous
+
+ or
+
+ 553- Ambiguous; Possibilities are
+ 553-Joe Smith <jsmith@foo.com>
+ 553-Harry Smith <hsmith@foo.com>
+ 553 Melvin Smith <dweep@foo.com>
+
+ or
+
+ 553-Ambiguous; Possibilities
+ 553- <jsmith@foo.com>
+ 553- <hsmith@foo.com>
+ 553 <dweep@foo.com>
+
+ Under normal circumstances, a client receiving a 553 reply would be
+ expected to expose the result to the user. Use of exactly the forms
+ given, and the "user ambiguous" or "ambiguous" keywords, possibly
+ supplemented by extended reply codes such as those described in [34],
+ will facilitate automated translation into other languages as needed.
+ Of course, a client that was highly automated or that was operating
+ in another language than English, might choose to try to translate
+ the response, to return some other indication to the user than the
+
+
+
+
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+
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+
+
+ literal text of the reply, or to take some automated action such as
+ consulting a directory service for additional information before
+ reporting to the user.
+
+ For the EXPN command, the string identifies a mailing list, and the
+ successful (i.e., 250) multiline response MAY include the full name
+ of the users and MUST give the mailboxes on the mailing list.
+
+ In some hosts the distinction between a mailing list and an alias for
+ a single mailbox is a bit fuzzy, since a common data structure may
+ hold both types of entries, and it is possible to have mailing lists
+ containing only one mailbox. If a request is made to apply VRFY to a
+ mailing list, a positive response MAY be given if a message so
+ addressed would be delivered to everyone on the list, otherwise an
+ error SHOULD be reported (e.g., "550 That is a mailing list, not a
+ user" or "252 Unable to verify members of mailing list"). If a
+ request is made to expand a user name, the server MAY return a
+ positive response consisting of a list containing one name, or an
+ error MAY be reported (e.g., "550 That is a user name, not a mailing
+ list").
+
+ In the case of a successful multiline reply (normal for EXPN) exactly
+ one mailbox is to be specified on each line of the reply. The case
+ of an ambiguous request is discussed above.
+
+ "User name" is a fuzzy term and has been used deliberately. An
+ implementation of the VRFY or EXPN commands MUST include at least
+ recognition of local mailboxes as "user names". However, since
+ current Internet practice often results in a single host handling
+ mail for multiple domains, hosts, especially hosts that provide this
+ functionality, SHOULD accept the "local-part@domain" form as a "user
+ name"; hosts MAY also choose to recognize other strings as "user
+ names".
+
+ The case of expanding a mailbox list requires a multiline reply, such
+ as:
+
+ C: EXPN Example-People
+ S: 250-Jon Postel <Postel@isi.edu>
+ S: 250-Fred Fonebone <Fonebone@physics.foo-u.edu>
+ S: 250 Sam Q. Smith <SQSmith@specific.generic.com>
+
+ or
+
+ C: EXPN Executive-Washroom-List
+ S: 550 Access Denied to You.
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ The character string arguments of the VRFY and EXPN commands cannot
+ be further restricted due to the variety of implementations of the
+ user name and mailbox list concepts. On some systems it may be
+ appropriate for the argument of the EXPN command to be a file name
+ for a file containing a mailing list, but again there are a variety
+ of file naming conventions in the Internet. Similarly, historical
+ variations in what is returned by these commands are such that the
+ response SHOULD be interpreted very carefully, if at all, and SHOULD
+ generally only be used for diagnostic purposes.
+
+3.5.2 VRFY Normal Response
+
+ When normal (2yz or 551) responses are returned from a VRFY or EXPN
+ request, the reply normally includes the mailbox name, i.e.,
+ "<local-part@domain>", where "domain" is a fully qualified domain
+ name, MUST appear in the syntax. In circumstances exceptional enough
+ to justify violating the intent of this specification, free-form text
+ MAY be returned. In order to facilitate parsing by both computers
+ and people, addresses SHOULD appear in pointed brackets. When
+ addresses, rather than free-form debugging information, are returned,
+ EXPN and VRFY MUST return only valid domain addresses that are usable
+ in SMTP RCPT commands. Consequently, if an address implies delivery
+ to a program or other system, the mailbox name used to reach that
+ target MUST be given. Paths (explicit source routes) MUST NOT be
+ returned by VRFY or EXPN.
+
+ Server implementations SHOULD support both VRFY and EXPN. For
+ security reasons, implementations MAY provide local installations a
+ way to disable either or both of these commands through configuration
+ options or the equivalent. When these commands are supported, they
+ are not required to work across relays when relaying is supported.
+ Since they were both optional in RFC 821, they MUST be listed as
+ service extensions in an EHLO response, if they are supported.
+
+3.5.3 Meaning of VRFY or EXPN Success Response
+
+ A server MUST NOT return a 250 code in response to a VRFY or EXPN
+ command unless it has actually verified the address. In particular,
+ a server MUST NOT return 250 if all it has done is to verify that the
+ syntax given is valid. In that case, 502 (Command not implemented)
+ or 500 (Syntax error, command unrecognized) SHOULD be returned. As
+ stated elsewhere, implementation (in the sense of actually validating
+ addresses and returning information) of VRFY and EXPN are strongly
+ recommended. Hence, implementations that return 500 or 502 for VRFY
+ are not in full compliance with this specification.
+
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ There may be circumstances where an address appears to be valid but
+ cannot reasonably be verified in real time, particularly when a
+ server is acting as a mail exchanger for another server or domain.
+ "Apparent validity" in this case would normally involve at least
+ syntax checking and might involve verification that any domains
+ specified were ones to which the host expected to be able to relay
+ mail. In these situations, reply code 252 SHOULD be returned. These
+ cases parallel the discussion of RCPT verification discussed in
+ section 2.1. Similarly, the discussion in section 3.4 applies to the
+ use of reply codes 251 and 551 with VRFY (and EXPN) to indicate
+ addresses that are recognized but that would be forwarded or bounced
+ were mail received for them. Implementations generally SHOULD be
+ more aggressive about address verification in the case of VRFY than
+ in the case of RCPT, even if it takes a little longer to do so.
+
+3.5.4 Semantics and Applications of EXPN
+
+ EXPN is often very useful in debugging and understanding problems
+ with mailing lists and multiple-target-address aliases. Some systems
+ have attempted to use source expansion of mailing lists as a means of
+ eliminating duplicates. The propagation of aliasing systems with
+ mail on the Internet, for hosts (typically with MX and CNAME DNS
+ records), for mailboxes (various types of local host aliases), and in
+ various proxying arrangements, has made it nearly impossible for
+ these strategies to work consistently, and mail systems SHOULD NOT
+ attempt them.
+
+3.6 Domains
+
+ Only resolvable, fully-qualified, domain names (FQDNs) are permitted
+ when domain names are used in SMTP. In other words, names that can
+ be resolved to MX RRs or A RRs (as discussed in section 5) are
+ permitted, as are CNAME RRs whose targets can be resolved, in turn,
+ to MX or A RRs. Local nicknames or unqualified names MUST NOT be
+ used. There are two exceptions to the rule requiring FQDNs:
+
+ - The domain name given in the EHLO command MUST BE either a primary
+ host name (a domain name that resolves to an A RR) or, if the host
+ has no name, an address literal as described in section 4.1.1.1.
+
+ - The reserved mailbox name "postmaster" may be used in a RCPT
+ command without domain qualification (see section 4.1.1.3) and
+ MUST be accepted if so used.
+
+
+
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+3.7 Relaying
+
+ In general, the availability of Mail eXchanger records in the domain
+ name system [22, 27] makes the use of explicit source routes in the
+ Internet mail system unnecessary. Many historical problems with
+ their interpretation have made their use undesirable. SMTP clients
+ SHOULD NOT generate explicit source routes except under unusual
+ circumstances. SMTP servers MAY decline to act as mail relays or to
+ accept addresses that specify source routes. When route information
+ is encountered, SMTP servers are also permitted to ignore the route
+ information and simply send to the final destination specified as the
+ last element in the route and SHOULD do so. There has been an
+ invalid practice of using names that do not appear in the DNS as
+ destination names, with the senders counting on the intermediate
+ hosts specified in source routing to resolve any problems. If source
+ routes are stripped, this practice will cause failures. This is one
+ of several reasons why SMTP clients MUST NOT generate invalid source
+ routes or depend on serial resolution of names.
+
+ When source routes are not used, the process described in RFC 821 for
+ constructing a reverse-path from the forward-path is not applicable
+ and the reverse-path at the time of delivery will simply be the
+ address that appeared in the MAIL command.
+
+ A relay SMTP server is usually the target of a DNS MX record that
+ designates it, rather than the final delivery system. The relay
+ server may accept or reject the task of relaying the mail in the same
+ way it accepts or rejects mail for a local user. If it accepts the
+ task, it then becomes an SMTP client, establishes a transmission
+ channel to the next SMTP server specified in the DNS (according to
+ the rules in section 5), and sends it the mail. If it declines to
+ relay mail to a particular address for policy reasons, a 550 response
+ SHOULD be returned.
+
+ Many mail-sending clients exist, especially in conjunction with
+ facilities that receive mail via POP3 or IMAP, that have limited
+ capability to support some of the requirements of this specification,
+ such as the ability to queue messages for subsequent delivery
+ attempts. For these clients, it is common practice to make private
+ arrangements to send all messages to a single server for processing
+ and subsequent distribution. SMTP, as specified here, is not ideally
+ suited for this role, and work is underway on standardized mail
+ submission protocols that might eventually supercede the current
+ practices. In any event, because these arrangements are private and
+ fall outside the scope of this specification, they are not described
+ here.
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ It is important to note that MX records can point to SMTP servers
+ which act as gateways into other environments, not just SMTP relays
+ and final delivery systems; see sections 3.8 and 5.
+
+ If an SMTP server has accepted the task of relaying the mail and
+ later finds that the destination is incorrect or that the mail cannot
+ be delivered for some other reason, then it MUST construct an
+ "undeliverable mail" notification message and send it to the
+ originator of the undeliverable mail (as indicated by the reverse-
+ path). Formats specified for non-delivery reports by other standards
+ (see, for example, [24, 25]) SHOULD be used if possible.
+
+ This notification message must be from the SMTP server at the relay
+ host or the host that first determines that delivery cannot be
+ accomplished. Of course, SMTP servers MUST NOT send notification
+ messages about problems transporting notification messages. One way
+ to prevent loops in error reporting is to specify a null reverse-path
+ in the MAIL command of a notification message. When such a message
+ is transmitted the reverse-path MUST be set to null (see section
+ 4.5.5 for additional discussion). A MAIL command with a null
+ reverse-path appears as follows:
+
+ MAIL FROM:<>
+
+ As discussed in section 2.4.1, a relay SMTP has no need to inspect or
+ act upon the headers or body of the message data and MUST NOT do so
+ except to add its own "Received:" header (section 4.4) and,
+ optionally, to attempt to detect looping in the mail system (see
+ section 6.2).
+
+3.8 Mail Gatewaying
+
+ While the relay function discussed above operates within the Internet
+ SMTP transport service environment, MX records or various forms of
+ explicit routing may require that an intermediate SMTP server perform
+ a translation function between one transport service and another. As
+ discussed in section 2.3.8, when such a system is at the boundary
+ between two transport service environments, we refer to it as a
+ "gateway" or "gateway SMTP".
+
+ Gatewaying mail between different mail environments, such as
+ different mail formats and protocols, is complex and does not easily
+ yield to standardization. However, some general requirements may be
+ given for a gateway between the Internet and another mail
+ environment.
+
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+3.8.1 Header Fields in Gatewaying
+
+ Header fields MAY be rewritten when necessary as messages are
+ gatewayed across mail environment boundaries. This may involve
+ inspecting the message body or interpreting the local-part of the
+ destination address in spite of the prohibitions in section 2.4.1.
+
+ Other mail systems gatewayed to the Internet often use a subset of
+ RFC 822 headers or provide similar functionality with a different
+ syntax, but some of these mail systems do not have an equivalent to
+ the SMTP envelope. Therefore, when a message leaves the Internet
+ environment, it may be necessary to fold the SMTP envelope
+ information into the message header. A possible solution would be to
+ create new header fields to carry the envelope information (e.g.,
+ "X-SMTP-MAIL:" and "X-SMTP-RCPT:"); however, this would require
+ changes in mail programs in foreign environments and might risk
+ disclosure of private information (see section 7.2).
+
+3.8.2 Received Lines in Gatewaying
+
+ When forwarding a message into or out of the Internet environment, a
+ gateway MUST prepend a Received: line, but it MUST NOT alter in any
+ way a Received: line that is already in the header.
+
+ "Received:" fields of messages originating from other environments
+ may not conform exactly to this specification. However, the most
+ important use of Received: lines is for debugging mail faults, and
+ this debugging can be severely hampered by well-meaning gateways that
+ try to "fix" a Received: line. As another consequence of trace
+ fields arising in non-SMTP environments, receiving systems MUST NOT
+ reject mail based on the format of a trace field and SHOULD be
+ extremely robust in the light of unexpected information or formats in
+ those fields.
+
+ The gateway SHOULD indicate the environment and protocol in the "via"
+ clauses of Received field(s) that it supplies.
+
+3.8.3 Addresses in Gatewaying
+
+ From the Internet side, the gateway SHOULD accept all valid address
+ formats in SMTP commands and in RFC 822 headers, and all valid RFC
+ 822 messages. Addresses and headers generated by gateways MUST
+ conform to applicable Internet standards (including this one and RFC
+ 822). Gateways are, of course, subject to the same rules for
+ handling source routes as those described for other SMTP systems in
+ section 3.3.
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+3.8.4 Other Header Fields in Gatewaying
+
+ The gateway MUST ensure that all header fields of a message that it
+ forwards into the Internet mail environment meet the requirements for
+ Internet mail. In particular, all addresses in "From:", "To:",
+ "Cc:", etc., fields MUST be transformed (if necessary) to satisfy RFC
+ 822 syntax, MUST reference only fully-qualified domain names, and
+ MUST be effective and useful for sending replies. The translation
+ algorithm used to convert mail from the Internet protocols to another
+ environment's protocol SHOULD ensure that error messages from the
+ foreign mail environment are delivered to the return path from the
+ SMTP envelope, not to the sender listed in the "From:" field (or
+ other fields) of the RFC 822 message.
+
+3.8.5 Envelopes in Gatewaying
+
+ Similarly, when forwarding a message from another environment into
+ the Internet, the gateway SHOULD set the envelope return path in
+ accordance with an error message return address, if supplied by the
+ foreign environment. If the foreign environment has no equivalent
+ concept, the gateway must select and use a best approximation, with
+ the message originator's address as the default of last resort.
+
+3.9 Terminating Sessions and Connections
+
+ An SMTP connection is terminated when the client sends a QUIT
+ command. The server responds with a positive reply code, after which
+ it closes the connection.
+
+ An SMTP server MUST NOT intentionally close the connection except:
+
+ - After receiving a QUIT command and responding with a 221 reply.
+
+ - After detecting the need to shut down the SMTP service and
+ returning a 421 response code. This response code can be issued
+ after the server receives any command or, if necessary,
+ asynchronously from command receipt (on the assumption that the
+ client will receive it after the next command is issued).
+
+ In particular, a server that closes connections in response to
+ commands that are not understood is in violation of this
+ specification. Servers are expected to be tolerant of unknown
+ commands, issuing a 500 reply and awaiting further instructions from
+ the client.
+
+
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ An SMTP server which is forcibly shut down via external means SHOULD
+ attempt to send a line containing a 421 response code to the SMTP
+ client before exiting. The SMTP client will normally read the 421
+ response code after sending its next command.
+
+ SMTP clients that experience a connection close, reset, or other
+ communications failure due to circumstances not under their control
+ (in violation of the intent of this specification but sometimes
+ unavoidable) SHOULD, to maintain the robustness of the mail system,
+ treat the mail transaction as if a 451 response had been received and
+ act accordingly.
+
+3.10 Mailing Lists and Aliases
+
+ An SMTP-capable host SHOULD support both the alias and the list
+ models of address expansion for multiple delivery. When a message is
+ delivered or forwarded to each address of an expanded list form, the
+ return address in the envelope ("MAIL FROM:") MUST be changed to be
+ the address of a person or other entity who administers the list.
+ However, in this case, the message header [32] MUST be left
+ unchanged; in particular, the "From" field of the message header is
+ unaffected.
+
+ An important mail facility is a mechanism for multi-destination
+ delivery of a single message, by transforming (or "expanding" or
+ "exploding") a pseudo-mailbox address into a list of destination
+ mailbox addresses. When a message is sent to such a pseudo-mailbox
+ (sometimes called an "exploder"), copies are forwarded or
+ redistributed to each mailbox in the expanded list. Servers SHOULD
+ simply utilize the addresses on the list; application of heuristics
+ or other matching rules to eliminate some addresses, such as that of
+ the originator, is strongly discouraged. We classify such a pseudo-
+ mailbox as an "alias" or a "list", depending upon the expansion
+ rules.
+
+3.10.1 Alias
+
+ To expand an alias, the recipient mailer simply replaces the pseudo-
+ mailbox address in the envelope with each of the expanded addresses
+ in turn; the rest of the envelope and the message body are left
+ unchanged. The message is then delivered or forwarded to each
+ expanded address.
+
+3.10.2 List
+
+ A mailing list may be said to operate by "redistribution" rather than
+ by "forwarding". To expand a list, the recipient mailer replaces the
+ pseudo-mailbox address in the envelope with all of the expanded
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ addresses. The return address in the envelope is changed so that all
+ error messages generated by the final deliveries will be returned to
+ a list administrator, not to the message originator, who generally
+ has no control over the contents of the list and will typically find
+ error messages annoying.
+
+4. The SMTP Specifications
+
+4.1 SMTP Commands
+
+4.1.1 Command Semantics and Syntax
+
+ The SMTP commands define the mail transfer or the mail system
+ function requested by the user. SMTP commands are character strings
+ terminated by <CRLF>. The commands themselves are alphabetic
+ characters terminated by <SP> if parameters follow and <CRLF>
+ otherwise. (In the interest of improved interoperability, SMTP
+ receivers are encouraged to tolerate trailing white space before the
+ terminating <CRLF>.) The syntax of the local part of a mailbox must
+ conform to receiver site conventions and the syntax specified in
+ section 4.1.2. The SMTP commands are discussed below. The SMTP
+ replies are discussed in section 4.2.
+
+ A mail transaction involves several data objects which are
+ communicated as arguments to different commands. The reverse-path is
+ the argument of the MAIL command, the forward-path is the argument of
+ the RCPT command, and the mail data is the argument of the DATA
+ command. These arguments or data objects must be transmitted and
+ held pending the confirmation communicated by the end of mail data
+ indication which finalizes the transaction. The model for this is
+ that distinct buffers are provided to hold the types of data objects,
+ that is, there is a reverse-path buffer, a forward-path buffer, and a
+ mail data buffer. Specific commands cause information to be appended
+ to a specific buffer, or cause one or more buffers to be cleared.
+
+ Several commands (RSET, DATA, QUIT) are specified as not permitting
+ parameters. In the absence of specific extensions offered by the
+ server and accepted by the client, clients MUST NOT send such
+ parameters and servers SHOULD reject commands containing them as
+ having invalid syntax.
+
+4.1.1.1 Extended HELLO (EHLO) or HELLO (HELO)
+
+ These commands are used to identify the SMTP client to the SMTP
+ server. The argument field contains the fully-qualified domain name
+ of the SMTP client if one is available. In situations in which the
+ SMTP client system does not have a meaningful domain name (e.g., when
+ its address is dynamically allocated and no reverse mapping record is
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ available), the client SHOULD send an address literal (see section
+ 4.1.3), optionally followed by information that will help to identify
+ the client system. y The SMTP server identifies itself to the SMTP
+ client in the connection greeting reply and in the response to this
+ command.
+
+ A client SMTP SHOULD start an SMTP session by issuing the EHLO
+ command. If the SMTP server supports the SMTP service extensions it
+ will give a successful response, a failure response, or an error
+ response. If the SMTP server, in violation of this specification,
+ does not support any SMTP service extensions it will generate an
+ error response. Older client SMTP systems MAY, as discussed above,
+ use HELO (as specified in RFC 821) instead of EHLO, and servers MUST
+ support the HELO command and reply properly to it. In any event, a
+ client MUST issue HELO or EHLO before starting a mail transaction.
+
+ These commands, and a "250 OK" reply to one of them, confirm that
+ both the SMTP client and the SMTP server are in the initial state,
+ that is, there is no transaction in progress and all state tables and
+ buffers are cleared.
+
+ Syntax:
+
+ ehlo = "EHLO" SP Domain CRLF
+ helo = "HELO" SP Domain CRLF
+
+ Normally, the response to EHLO will be a multiline reply. Each line
+ of the response contains a keyword and, optionally, one or more
+ parameters. Following the normal syntax for multiline replies, these
+ keyworks follow the code (250) and a hyphen for all but the last
+ line, and the code and a space for the last line. The syntax for a
+ positive response, using the ABNF notation and terminal symbols of
+ [8], is:
+
+ ehlo-ok-rsp = ( "250" domain [ SP ehlo-greet ] CRLF )
+ / ( "250-" domain [ SP ehlo-greet ] CRLF
+ *( "250-" ehlo-line CRLF )
+ "250" SP ehlo-line CRLF )
+
+ ehlo-greet = 1*(%d0-9 / %d11-12 / %d14-127)
+ ; string of any characters other than CR or LF
+
+ ehlo-line = ehlo-keyword *( SP ehlo-param )
+
+ ehlo-keyword = (ALPHA / DIGIT) *(ALPHA / DIGIT / "-")
+ ; additional syntax of ehlo-params depends on
+ ; ehlo-keyword
+
+
+
+
+Klensin Standards Track [Page 30]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ ehlo-param = 1*(%d33-127)
+ ; any CHAR excluding <SP> and all
+ ; control characters (US-ASCII 0-31 inclusive)
+
+ Although EHLO keywords may be specified in upper, lower, or mixed
+ case, they MUST always be recognized and processed in a case-
+ insensitive manner. This is simply an extension of practices
+ specified in RFC 821 and section 2.4.1.
+
+4.1.1.2 MAIL (MAIL)
+
+ This command is used to initiate a mail transaction in which the mail
+ data is delivered to an SMTP server which may, in turn, deliver it to
+ one or more mailboxes or pass it on to another system (possibly using
+ SMTP). The argument field contains a reverse-path and may contain
+ optional parameters. In general, the MAIL command may be sent only
+ when no mail transaction is in progress, see section 4.1.4.
+
+ The reverse-path consists of the sender mailbox. Historically, that
+ mailbox might optionally have been preceded by a list of hosts, but
+ that behavior is now deprecated (see appendix C). In some types of
+ reporting messages for which a reply is likely to cause a mail loop
+ (for example, mail delivery and nondelivery notifications), the
+ reverse-path may be null (see section 3.7).
+
+ This command clears the reverse-path buffer, the forward-path buffer,
+ and the mail data buffer; and inserts the reverse-path information
+ from this command into the reverse-path buffer.
+
+ If service extensions were negotiated, the MAIL command may also
+ carry parameters associated with a particular service extension.
+
+ Syntax:
+
+ "MAIL FROM:" ("<>" / Reverse-Path)
+ [SP Mail-parameters] CRLF
+
+4.1.1.3 RECIPIENT (RCPT)
+
+ This command is used to identify an individual recipient of the mail
+ data; multiple recipients are specified by multiple use of this
+ command. The argument field contains a forward-path and may contain
+ optional parameters.
+
+ The forward-path normally consists of the required destination
+ mailbox. Sending systems SHOULD not generate the optional list of
+ hosts known as a source route. Receiving systems MUST recognize
+
+
+
+
+Klensin Standards Track [Page 31]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ source route syntax but SHOULD strip off the source route
+ specification and utilize the domain name associated with the mailbox
+ as if the source route had not been provided.
+
+ Similarly, relay hosts SHOULD strip or ignore source routes, and
+ names MUST NOT be copied into the reverse-path. When mail reaches
+ its ultimate destination (the forward-path contains only a
+ destination mailbox), the SMTP server inserts it into the destination
+ mailbox in accordance with its host mail conventions.
+
+ For example, mail received at relay host xyz.com with envelope
+ commands
+
+ MAIL FROM:<userx@y.foo.org>
+ RCPT TO:<@hosta.int,@jkl.org:userc@d.bar.org>
+
+ will normally be sent directly on to host d.bar.org with envelope
+ commands
+
+ MAIL FROM:<userx@y.foo.org>
+ RCPT TO:<userc@d.bar.org>
+
+ As provided in appendix C, xyz.com MAY also choose to relay the
+ message to hosta.int, using the envelope commands
+
+ MAIL FROM:<userx@y.foo.org>
+ RCPT TO:<@hosta.int,@jkl.org:userc@d.bar.org>
+
+ or to jkl.org, using the envelope commands
+
+ MAIL FROM:<userx@y.foo.org>
+ RCPT TO:<@jkl.org:userc@d.bar.org>
+
+ Of course, since hosts are not required to relay mail at all, xyz.com
+ may also reject the message entirely when the RCPT command is
+ received, using a 550 code (since this is a "policy reason").
+
+ If service extensions were negotiated, the RCPT command may also
+ carry parameters associated with a particular service extension
+ offered by the server. The client MUST NOT transmit parameters other
+ than those associated with a service extension offered by the server
+ in its EHLO response.
+
+Syntax:
+ "RCPT TO:" ("<Postmaster@" domain ">" / "<Postmaster>" / Forward-Path)
+ [SP Rcpt-parameters] CRLF
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+4.1.1.4 DATA (DATA)
+
+ The receiver normally sends a 354 response to DATA, and then treats
+ the lines (strings ending in <CRLF> sequences, as described in
+ section 2.3.7) following the command as mail data from the sender.
+ This command causes the mail data to be appended to the mail data
+ buffer. The mail data may contain any of the 128 ASCII character
+ codes, although experience has indicated that use of control
+ characters other than SP, HT, CR, and LF may cause problems and
+ SHOULD be avoided when possible.
+
+ The mail data is terminated by a line containing only a period, that
+ is, the character sequence "<CRLF>.<CRLF>" (see section 4.5.2). This
+ is the end of mail data indication. Note that the first <CRLF> of
+ this terminating sequence is also the <CRLF> that ends the final line
+ of the data (message text) or, if there was no data, ends the DATA
+ command itself. An extra <CRLF> MUST NOT be added, as that would
+ cause an empty line to be added to the message. The only exception
+ to this rule would arise if the message body were passed to the
+ originating SMTP-sender with a final "line" that did not end in
+ <CRLF>; in that case, the originating SMTP system MUST either reject
+ the message as invalid or add <CRLF> in order to have the receiving
+ SMTP server recognize the "end of data" condition.
+
+ The custom of accepting lines ending only in <LF>, as a concession to
+ non-conforming behavior on the part of some UNIX systems, has proven
+ to cause more interoperability problems than it solves, and SMTP
+ server systems MUST NOT do this, even in the name of improved
+ robustness. In particular, the sequence "<LF>.<LF>" (bare line
+ feeds, without carriage returns) MUST NOT be treated as equivalent to
+ <CRLF>.<CRLF> as the end of mail data indication.
+
+ Receipt of the end of mail data indication requires the server to
+ process the stored mail transaction information. This processing
+ consumes the information in the reverse-path buffer, the forward-path
+ buffer, and the mail data buffer, and on the completion of this
+ command these buffers are cleared. If the processing is successful,
+ the receiver MUST send an OK reply. If the processing fails the
+ receiver MUST send a failure reply. The SMTP model does not allow
+ for partial failures at this point: either the message is accepted by
+ the server for delivery and a positive response is returned or it is
+ not accepted and a failure reply is returned. In sending a positive
+ completion reply to the end of data indication, the receiver takes
+ full responsibility for the message (see section 6.1). Errors that
+ are diagnosed subsequently MUST be reported in a mail message, as
+ discussed in section 4.4.
+
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ When the SMTP server accepts a message either for relaying or for
+ final delivery, it inserts a trace record (also referred to
+ interchangeably as a "time stamp line" or "Received" line) at the top
+ of the mail data. This trace record indicates the identity of the
+ host that sent the message, the identity of the host that received
+ the message (and is inserting this time stamp), and the date and time
+ the message was received. Relayed messages will have multiple time
+ stamp lines. Details for formation of these lines, including their
+ syntax, is specified in section 4.4.
+
+ Additional discussion about the operation of the DATA command appears
+ in section 3.3.
+
+ Syntax:
+ "DATA" CRLF
+
+4.1.1.5 RESET (RSET)
+
+ This command specifies that the current mail transaction will be
+ aborted. Any stored sender, recipients, and mail data MUST be
+ discarded, and all buffers and state tables cleared. The receiver
+ MUST send a "250 OK" reply to a RSET command with no arguments. A
+ reset command may be issued by the client at any time. It is
+ effectively equivalent to a NOOP (i.e., if has no effect) if issued
+ immediately after EHLO, before EHLO is issued in the session, after
+ an end-of-data indicator has been sent and acknowledged, or
+ immediately before a QUIT. An SMTP server MUST NOT close the
+ connection as the result of receiving a RSET; that action is reserved
+ for QUIT (see section 4.1.1.10).
+
+ Since EHLO implies some additional processing and response by the
+ server, RSET will normally be more efficient than reissuing that
+ command, even though the formal semantics are the same.
+
+ There are circumstances, contrary to the intent of this
+ specification, in which an SMTP server may receive an indication that
+ the underlying TCP connection has been closed or reset. To preserve
+ the robustness of the mail system, SMTP servers SHOULD be prepared
+ for this condition and SHOULD treat it as if a QUIT had been received
+ before the connection disappeared.
+
+ Syntax:
+ "RSET" CRLF
+
+
+
+
+
+
+
+
+Klensin Standards Track [Page 34]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+4.1.1.6 VERIFY (VRFY)
+
+ This command asks the receiver to confirm that the argument
+ identifies a user or mailbox. If it is a user name, information is
+ returned as specified in section 3.5.
+
+ This command has no effect on the reverse-path buffer, the forward-
+ path buffer, or the mail data buffer.
+
+ Syntax:
+ "VRFY" SP String CRLF
+
+4.1.1.7 EXPAND (EXPN)
+
+ This command asks the receiver to confirm that the argument
+ identifies a mailing list, and if so, to return the membership of
+ that list. If the command is successful, a reply is returned
+ containing information as described in section 3.5. This reply will
+ have multiple lines except in the trivial case of a one-member list.
+
+ This command has no effect on the reverse-path buffer, the forward-
+ path buffer, or the mail data buffer and may be issued at any time.
+
+ Syntax:
+ "EXPN" SP String CRLF
+
+4.1.1.8 HELP (HELP)
+
+ This command causes the server to send helpful information to the
+ client. The command MAY take an argument (e.g., any command name)
+ and return more specific information as a response.
+
+ This command has no effect on the reverse-path buffer, the forward-
+ path buffer, or the mail data buffer and may be issued at any time.
+
+ SMTP servers SHOULD support HELP without arguments and MAY support it
+ with arguments.
+
+ Syntax:
+ "HELP" [ SP String ] CRLF
+
+4.1.1.9 NOOP (NOOP)
+
+ This command does not affect any parameters or previously entered
+ commands. It specifies no action other than that the receiver send
+ an OK reply.
+
+
+
+
+
+Klensin Standards Track [Page 35]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ This command has no effect on the reverse-path buffer, the forward-
+ path buffer, or the mail data buffer and may be issued at any time.
+ If a parameter string is specified, servers SHOULD ignore it.
+
+ Syntax:
+ "NOOP" [ SP String ] CRLF
+
+4.1.1.10 QUIT (QUIT)
+
+ This command specifies that the receiver MUST send an OK reply, and
+ then close the transmission channel.
+
+ The receiver MUST NOT intentionally close the transmission channel
+ until it receives and replies to a QUIT command (even if there was an
+ error). The sender MUST NOT intentionally close the transmission
+ channel until it sends a QUIT command and SHOULD wait until it
+ receives the reply (even if there was an error response to a previous
+ command). If the connection is closed prematurely due to violations
+ of the above or system or network failure, the server MUST cancel any
+ pending transaction, but not undo any previously completed
+ transaction, and generally MUST act as if the command or transaction
+ in progress had received a temporary error (i.e., a 4yz response).
+
+ The QUIT command may be issued at any time.
+
+ Syntax:
+ "QUIT" CRLF
+
+4.1.2 Command Argument Syntax
+
+ The syntax of the argument fields of the above commands (using the
+ syntax specified in [8] where applicable) is given below. Some of
+ the productions given below are used only in conjunction with source
+ routes as described in appendix C. Terminals not defined in this
+ document, such as ALPHA, DIGIT, SP, CR, LF, CRLF, are as defined in
+ the "core" syntax [8 (section 6)] or in the message format syntax
+ [32].
+
+ Reverse-path = Path
+ Forward-path = Path
+ Path = "<" [ A-d-l ":" ] Mailbox ">"
+ A-d-l = At-domain *( "," A-d-l )
+ ; Note that this form, the so-called "source route",
+ ; MUST BE accepted, SHOULD NOT be generated, and SHOULD be
+ ; ignored.
+ At-domain = "@" domain
+ Mail-parameters = esmtp-param *(SP esmtp-param)
+ Rcpt-parameters = esmtp-param *(SP esmtp-param)
+
+
+
+Klensin Standards Track [Page 36]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ esmtp-param = esmtp-keyword ["=" esmtp-value]
+ esmtp-keyword = (ALPHA / DIGIT) *(ALPHA / DIGIT / "-")
+ esmtp-value = 1*(%d33-60 / %d62-127)
+ ; any CHAR excluding "=", SP, and control characters
+ Keyword = Ldh-str
+ Argument = Atom
+ Domain = (sub-domain 1*("." sub-domain)) / address-literal
+ sub-domain = Let-dig [Ldh-str]
+
+ address-literal = "[" IPv4-address-literal /
+ IPv6-address-literal /
+ General-address-literal "]"
+ ; See section 4.1.3
+
+ Mailbox = Local-part "@" Domain
+
+ Local-part = Dot-string / Quoted-string
+ ; MAY be case-sensitive
+
+ Dot-string = Atom *("." Atom)
+
+ Atom = 1*atext
+
+ Quoted-string = DQUOTE *qcontent DQUOTE
+
+ String = Atom / Quoted-string
+
+ While the above definition for Local-part is relatively permissive,
+ for maximum interoperability, a host that expects to receive mail
+ SHOULD avoid defining mailboxes where the Local-part requires (or
+ uses) the Quoted-string form or where the Local-part is case-
+ sensitive. For any purposes that require generating or comparing
+ Local-parts (e.g., to specific mailbox names), all quoted forms MUST
+ be treated as equivalent and the sending system SHOULD transmit the
+ form that uses the minimum quoting possible.
+
+ Systems MUST NOT define mailboxes in such a way as to require the use
+ in SMTP of non-ASCII characters (octets with the high order bit set
+ to one) or ASCII "control characters" (decimal value 0-31 and 127).
+ These characters MUST NOT be used in MAIL or RCPT commands or other
+ commands that require mailbox names.
+
+ Note that the backslash, "\", is a quote character, which is used to
+ indicate that the next character is to be used literally (instead of
+ its normal interpretation). For example, "Joe\,Smith" indicates a
+ single nine character user field with the comma being the fourth
+ character of the field.
+
+
+
+
+Klensin Standards Track [Page 37]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ To promote interoperability and consistent with long-standing
+ guidance about conservative use of the DNS in naming and applications
+ (e.g., see section 2.3.1 of the base DNS document, RFC1035 [22]),
+ characters outside the set of alphas, digits, and hyphen MUST NOT
+ appear in domain name labels for SMTP clients or servers. In
+ particular, the underscore character is not permitted. SMTP servers
+ that receive a command in which invalid character codes have been
+ employed, and for which there are no other reasons for rejection,
+ MUST reject that command with a 501 response.
+
+4.1.3 Address Literals
+
+ Sometimes a host is not known to the domain name system and
+ communication (and, in particular, communication to report and repair
+ the error) is blocked. To bypass this barrier a special literal form
+ of the address is allowed as an alternative to a domain name. For
+ IPv4 addresses, this form uses four small decimal integers separated
+ by dots and enclosed by brackets such as [123.255.37.2], which
+ indicates an (IPv4) Internet Address in sequence-of-octets form. For
+ IPv6 and other forms of addressing that might eventually be
+ standardized, the form consists of a standardized "tag" that
+ identifies the address syntax, a colon, and the address itself, in a
+ format specified as part of the IPv6 standards [17].
+
+ Specifically:
+
+ IPv4-address-literal = Snum 3("." Snum)
+ IPv6-address-literal = "IPv6:" IPv6-addr
+ General-address-literal = Standardized-tag ":" 1*dcontent
+ Standardized-tag = Ldh-str
+ ; MUST be specified in a standards-track RFC
+ ; and registered with IANA
+
+ Snum = 1*3DIGIT ; representing a decimal integer
+ ; value in the range 0 through 255
+ Let-dig = ALPHA / DIGIT
+ Ldh-str = *( ALPHA / DIGIT / "-" ) Let-dig
+
+ IPv6-addr = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp
+ IPv6-hex = 1*4HEXDIG
+ IPv6-full = IPv6-hex 7(":" IPv6-hex)
+ IPv6-comp = [IPv6-hex *5(":" IPv6-hex)] "::" [IPv6-hex *5(":"
+ IPv6-hex)]
+ ; The "::" represents at least 2 16-bit groups of zeros
+ ; No more than 6 groups in addition to the "::" may be
+ ; present
+ IPv6v4-full = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal
+ IPv6v4-comp = [IPv6-hex *3(":" IPv6-hex)] "::"
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ [IPv6-hex *3(":" IPv6-hex) ":"] IPv4-address-literal
+ ; The "::" represents at least 2 16-bit groups of zeros
+ ; No more than 4 groups in addition to the "::" and
+ ; IPv4-address-literal may be present
+
+4.1.4 Order of Commands
+
+ There are restrictions on the order in which these commands may be
+ used.
+
+ A session that will contain mail transactions MUST first be
+ initialized by the use of the EHLO command. An SMTP server SHOULD
+ accept commands for non-mail transactions (e.g., VRFY or EXPN)
+ without this initialization.
+
+ An EHLO command MAY be issued by a client later in the session. If
+ it is issued after the session begins, the SMTP server MUST clear all
+ buffers and reset the state exactly as if a RSET command had been
+ issued. In other words, the sequence of RSET followed immediately by
+ EHLO is redundant, but not harmful other than in the performance cost
+ of executing unnecessary commands.
+
+ If the EHLO command is not acceptable to the SMTP server, 501, 500,
+ or 502 failure replies MUST be returned as appropriate. The SMTP
+ server MUST stay in the same state after transmitting these replies
+ that it was in before the EHLO was received.
+
+ The SMTP client MUST, if possible, ensure that the domain parameter
+ to the EHLO command is a valid principal host name (not a CNAME or MX
+ name) for its host. If this is not possible (e.g., when the client's
+ address is dynamically assigned and the client does not have an
+ obvious name), an address literal SHOULD be substituted for the
+ domain name and supplemental information provided that will assist in
+ identifying the client.
+
+ An SMTP server MAY verify that the domain name parameter in the EHLO
+ command actually corresponds to the IP address of the client.
+ However, the server MUST NOT refuse to accept a message for this
+ reason if the verification fails: the information about verification
+ failure is for logging and tracing only.
+
+ The NOOP, HELP, EXPN, VRFY, and RSET commands can be used at any time
+ during a session, or without previously initializing a session. SMTP
+ servers SHOULD process these normally (that is, not return a 503
+ code) even if no EHLO command has yet been received; clients SHOULD
+ open a session with EHLO before sending these commands.
+
+
+
+
+
+Klensin Standards Track [Page 39]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ If these rules are followed, the example in RFC 821 that shows "550
+ access denied to you" in response to an EXPN command is incorrect
+ unless an EHLO command precedes the EXPN or the denial of access is
+ based on the client's IP address or other authentication or
+ authorization-determining mechanisms.
+
+ The MAIL command (or the obsolete SEND, SOML, or SAML commands)
+ begins a mail transaction. Once started, a mail transaction consists
+ of a transaction beginning command, one or more RCPT commands, and a
+ DATA command, in that order. A mail transaction may be aborted by
+ the RSET (or a new EHLO) command. There may be zero or more
+ transactions in a session. MAIL (or SEND, SOML, or SAML) MUST NOT be
+ sent if a mail transaction is already open, i.e., it should be sent
+ only if no mail transaction had been started in the session, or it
+ the previous one successfully concluded with a successful DATA
+ command, or if the previous one was aborted with a RSET.
+
+ If the transaction beginning command argument is not acceptable, a
+ 501 failure reply MUST be returned and the SMTP server MUST stay in
+ the same state. If the commands in a transaction are out of order to
+ the degree that they cannot be processed by the server, a 503 failure
+ reply MUST be returned and the SMTP server MUST stay in the same
+ state.
+
+ The last command in a session MUST be the QUIT command. The QUIT
+ command cannot be used at any other time in a session, but SHOULD be
+ used by the client SMTP to request connection closure, even when no
+ session opening command was sent and accepted.
+
+4.1.5 Private-use Commands
+
+ As specified in section 2.2.2, commands starting in "X" may be used
+ by bilateral agreement between the client (sending) and server
+ (receiving) SMTP agents. An SMTP server that does not recognize such
+ a command is expected to reply with "500 Command not recognized". An
+ extended SMTP server MAY list the feature names associated with these
+ private commands in the response to the EHLO command.
+
+ Commands sent or accepted by SMTP systems that do not start with "X"
+ MUST conform to the requirements of section 2.2.2.
+
+4.2 SMTP Replies
+
+ Replies to SMTP commands serve to ensure the synchronization of
+ requests and actions in the process of mail transfer and to guarantee
+ that the SMTP client always knows the state of the SMTP server.
+ Every command MUST generate exactly one reply.
+
+
+
+
+Klensin Standards Track [Page 40]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ The details of the command-reply sequence are described in section
+ 4.3.
+
+ An SMTP reply consists of a three digit number (transmitted as three
+ numeric characters) followed by some text unless specified otherwise
+ in this document. The number is for use by automata to determine
+ what state to enter next; the text is for the human user. The three
+ digits contain enough encoded information that the SMTP client need
+ not examine the text and may either discard it or pass it on to the
+ user, as appropriate. Exceptions are as noted elsewhere in this
+ document. In particular, the 220, 221, 251, 421, and 551 reply codes
+ are associated with message text that must be parsed and interpreted
+ by machines. In the general case, the text may be receiver dependent
+ and context dependent, so there are likely to be varying texts for
+ each reply code. A discussion of the theory of reply codes is given
+ in section 4.2.1. Formally, a reply is defined to be the sequence: a
+ three-digit code, <SP>, one line of text, and <CRLF>, or a multiline
+ reply (as defined in section 4.2.1). Since, in violation of this
+ specification, the text is sometimes not sent, clients which do not
+ receive it SHOULD be prepared to process the code alone (with or
+ without a trailing space character). Only the EHLO, EXPN, and HELP
+ commands are expected to result in multiline replies in normal
+ circumstances, however, multiline replies are allowed for any
+ command.
+
+ In ABNF, server responses are:
+
+ Greeting = "220 " Domain [ SP text ] CRLF
+ Reply-line = Reply-code [ SP text ] CRLF
+
+ where "Greeting" appears only in the 220 response that announces that
+ the server is opening its part of the connection.
+
+ An SMTP server SHOULD send only the reply codes listed in this
+ document. An SMTP server SHOULD use the text shown in the examples
+ whenever appropriate.
+
+ An SMTP client MUST determine its actions only by the reply code, not
+ by the text (except for the "change of address" 251 and 551 and, if
+ necessary, 220, 221, and 421 replies); in the general case, any text,
+ including no text at all (although senders SHOULD NOT send bare
+ codes), MUST be acceptable. The space (blank) following the reply
+ code is considered part of the text. Whenever possible, a receiver-
+ SMTP SHOULD test the first digit (severity indication) of the reply
+ code.
+
+
+
+
+
+
+Klensin Standards Track [Page 41]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ The list of codes that appears below MUST NOT be construed as
+ permanent. While the addition of new codes should be a rare and
+ significant activity, with supplemental information in the textual
+ part of the response being preferred, new codes may be added as the
+ result of new Standards or Standards-track specifications.
+ Consequently, a sender-SMTP MUST be prepared to handle codes not
+ specified in this document and MUST do so by interpreting the first
+ digit only.
+
+4.2.1 Reply Code Severities and Theory
+
+ The three digits of the reply each have a special significance. The
+ first digit denotes whether the response is good, bad or incomplete.
+ An unsophisticated SMTP client, or one that receives an unexpected
+ code, will be able to determine its next action (proceed as planned,
+ redo, retrench, etc.) by examining this first digit. An SMTP client
+ that wants to know approximately what kind of error occurred (e.g.,
+ mail system error, command syntax error) may examine the second
+ digit. The third digit and any supplemental information that may be
+ present is reserved for the finest gradation of information.
+
+ There are five values for the first digit of the reply code:
+
+ 1yz Positive Preliminary reply
+ The command has been accepted, but the requested action is being
+ held in abeyance, pending confirmation of the information in this
+ reply. The SMTP client should send another command specifying
+ whether to continue or abort the action. Note: unextended SMTP
+ does not have any commands that allow this type of reply, and so
+ does not have continue or abort commands.
+
+ 2yz Positive Completion reply
+ The requested action has been successfully completed. A new
+ request may be initiated.
+
+ 3yz Positive Intermediate reply
+ The command has been accepted, but the requested action is being
+ held in abeyance, pending receipt of further information. The
+ SMTP client should send another command specifying this
+ information. This reply is used in command sequence groups (i.e.,
+ in DATA).
+
+ 4yz Transient Negative Completion reply
+ The command was not accepted, and the requested action did not
+ occur. However, the error condition is temporary and the action
+ may be requested again. The sender should return to the beginning
+ of the command sequence (if any). It is difficult to assign a
+ meaning to "transient" when two different sites (receiver- and
+
+
+
+Klensin Standards Track [Page 42]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ sender-SMTP agents) must agree on the interpretation. Each reply
+ in this category might have a different time value, but the SMTP
+ client is encouraged to try again. A rule of thumb to determine
+ whether a reply fits into the 4yz or the 5yz category (see below)
+ is that replies are 4yz if they can be successful if repeated
+ without any change in command form or in properties of the sender
+ or receiver (that is, the command is repeated identically and the
+ receiver does not put up a new implementation.)
+
+ 5yz Permanent Negative Completion reply
+ The command was not accepted and the requested action did not
+ occur. The SMTP client is discouraged from repeating the exact
+ request (in the same sequence). Even some "permanent" error
+ conditions can be corrected, so the human user may want to direct
+ the SMTP client to reinitiate the command sequence by direct
+ action at some point in the future (e.g., after the spelling has
+ been changed, or the user has altered the account status).
+
+ The second digit encodes responses in specific categories:
+
+ x0z Syntax: These replies refer to syntax errors, syntactically
+ correct commands that do not fit any functional category, and
+ unimplemented or superfluous commands.
+
+ x1z Information: These are replies to requests for information,
+ such as status or help.
+
+ x2z Connections: These are replies referring to the transmission
+ channel.
+
+ x3z Unspecified.
+
+ x4z Unspecified.
+
+ x5z Mail system: These replies indicate the status of the receiver
+ mail system vis-a-vis the requested transfer or other mail system
+ action.
+
+ The third digit gives a finer gradation of meaning in each category
+ specified by the second digit. The list of replies illustrates this.
+ Each reply text is recommended rather than mandatory, and may even
+ change according to the command with which it is associated. On the
+ other hand, the reply codes must strictly follow the specifications
+ in this section. Receiver implementations should not invent new
+ codes for slightly different situations from the ones described here,
+ but rather adapt codes already defined.
+
+
+
+
+
+Klensin Standards Track [Page 43]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ For example, a command such as NOOP, whose successful execution does
+ not offer the SMTP client any new information, will return a 250
+ reply. The reply is 502 when the command requests an unimplemented
+ non-site-specific action. A refinement of that is the 504 reply for
+ a command that is implemented, but that requests an unimplemented
+ parameter.
+
+ The reply text may be longer than a single line; in these cases the
+ complete text must be marked so the SMTP client knows when it can
+ stop reading the reply. This requires a special format to indicate a
+ multiple line reply.
+
+ The format for multiline replies requires that every line, except the
+ last, begin with the reply code, followed immediately by a hyphen,
+ "-" (also known as minus), followed by text. The last line will
+ begin with the reply code, followed immediately by <SP>, optionally
+ some text, and <CRLF>. As noted above, servers SHOULD send the <SP>
+ if subsequent text is not sent, but clients MUST be prepared for it
+ to be omitted.
+
+ For example:
+
+ 123-First line
+ 123-Second line
+ 123-234 text beginning with numbers
+ 123 The last line
+
+ In many cases the SMTP client then simply needs to search for a line
+ beginning with the reply code followed by <SP> or <CRLF> and ignore
+ all preceding lines. In a few cases, there is important data for the
+ client in the reply "text". The client will be able to identify
+ these cases from the current context.
+
+4.2.2 Reply Codes by Function Groups
+
+ 500 Syntax error, command unrecognized
+ (This may include errors such as command line too long)
+ 501 Syntax error in parameters or arguments
+ 502 Command not implemented (see section 4.2.4)
+ 503 Bad sequence of commands
+ 504 Command parameter not implemented
+
+ 211 System status, or system help reply
+ 214 Help message
+ (Information on how to use the receiver or the meaning of a
+ particular non-standard command; this reply is useful only
+ to the human user)
+
+
+
+
+Klensin Standards Track [Page 44]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ 220 <domain> Service ready
+ 221 <domain> Service closing transmission channel
+ 421 <domain> Service not available, closing transmission channel
+ (This may be a reply to any command if the service knows it
+ must shut down)
+
+ 250 Requested mail action okay, completed
+ 251 User not local; will forward to <forward-path>
+ (See section 3.4)
+ 252 Cannot VRFY user, but will accept message and attempt
+ delivery
+ (See section 3.5.3)
+ 450 Requested mail action not taken: mailbox unavailable
+ (e.g., mailbox busy)
+ 550 Requested action not taken: mailbox unavailable
+ (e.g., mailbox not found, no access, or command rejected
+ for policy reasons)
+ 451 Requested action aborted: error in processing
+ 551 User not local; please try <forward-path>
+ (See section 3.4)
+ 452 Requested action not taken: insufficient system storage
+ 552 Requested mail action aborted: exceeded storage allocation
+ 553 Requested action not taken: mailbox name not allowed
+ (e.g., mailbox syntax incorrect)
+ 354 Start mail input; end with <CRLF>.<CRLF>
+ 554 Transaction failed (Or, in the case of a connection-opening
+ response, "No SMTP service here")
+
+4.2.3 Reply Codes in Numeric Order
+
+ 211 System status, or system help reply
+ 214 Help message
+ (Information on how to use the receiver or the meaning of a
+ particular non-standard command; this reply is useful only
+ to the human user)
+ 220 <domain> Service ready
+ 221 <domain> Service closing transmission channel
+ 250 Requested mail action okay, completed
+ 251 User not local; will forward to <forward-path>
+ (See section 3.4)
+ 252 Cannot VRFY user, but will accept message and attempt
+ delivery
+ (See section 3.5.3)
+
+ 354 Start mail input; end with <CRLF>.<CRLF>
+
+
+
+
+
+
+Klensin Standards Track [Page 45]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ 421 <domain> Service not available, closing transmission channel
+ (This may be a reply to any command if the service knows it
+ must shut down)
+ 450 Requested mail action not taken: mailbox unavailable
+ (e.g., mailbox busy)
+ 451 Requested action aborted: local error in processing
+ 452 Requested action not taken: insufficient system storage
+ 500 Syntax error, command unrecognized
+ (This may include errors such as command line too long)
+ 501 Syntax error in parameters or arguments
+ 502 Command not implemented (see section 4.2.4)
+ 503 Bad sequence of commands
+ 504 Command parameter not implemented
+ 550 Requested action not taken: mailbox unavailable
+ (e.g., mailbox not found, no access, or command rejected
+ for policy reasons)
+ 551 User not local; please try <forward-path>
+ (See section 3.4)
+ 552 Requested mail action aborted: exceeded storage allocation
+ 553 Requested action not taken: mailbox name not allowed
+ (e.g., mailbox syntax incorrect)
+ 554 Transaction failed (Or, in the case of a connection-opening
+ response, "No SMTP service here")
+
+4.2.4 Reply Code 502
+
+ Questions have been raised as to when reply code 502 (Command not
+ implemented) SHOULD be returned in preference to other codes. 502
+ SHOULD be used when the command is actually recognized by the SMTP
+ server, but not implemented. If the command is not recognized, code
+ 500 SHOULD be returned. Extended SMTP systems MUST NOT list
+ capabilities in response to EHLO for which they will return 502 (or
+ 500) replies.
+
+4.2.5 Reply Codes After DATA and the Subsequent <CRLF>.<CRLF>
+
+ When an SMTP server returns a positive completion status (2yz code)
+ after the DATA command is completed with <CRLF>.<CRLF>, it accepts
+ responsibility for:
+
+ - delivering the message (if the recipient mailbox exists), or
+
+ - if attempts to deliver the message fail due to transient
+ conditions, retrying delivery some reasonable number of times at
+ intervals as specified in section 4.5.4.
+
+
+
+
+
+
+Klensin Standards Track [Page 46]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ - if attempts to deliver the message fail due to permanent
+ conditions, or if repeated attempts to deliver the message fail
+ due to transient conditions, returning appropriate notification to
+ the sender of the original message (using the address in the SMTP
+ MAIL command).
+
+ When an SMTP server returns a permanent error status (5yz) code after
+ the DATA command is completed with <CRLF>.<CRLF>, it MUST NOT make
+ any subsequent attempt to deliver that message. The SMTP client
+ retains responsibility for delivery of that message and may either
+ return it to the user or requeue it for a subsequent attempt (see
+ section 4.5.4.1).
+
+ The user who originated the message SHOULD be able to interpret the
+ return of a transient failure status (by mail message or otherwise)
+ as a non-delivery indication, just as a permanent failure would be
+ interpreted. I.e., if the client SMTP successfully handles these
+ conditions, the user will not receive such a reply.
+
+ When an SMTP server returns a permanent error status (5yz) code after
+ the DATA command is completely with <CRLF>.<CRLF>, it MUST NOT make
+ any subsequent attempt to deliver the message. As with temporary
+ error status codes, the SMTP client retains responsibility for the
+ message, but SHOULD not again attempt delivery to the same server
+ without user review and intervention of the message.
+
+4.3 Sequencing of Commands and Replies
+
+4.3.1 Sequencing Overview
+
+ The communication between the sender and receiver is an alternating
+ dialogue, controlled by the sender. As such, the sender issues a
+ command and the receiver responds with a reply. Unless other
+ arrangements are negotiated through service extensions, the sender
+ MUST wait for this response before sending further commands.
+
+ One important reply is the connection greeting. Normally, a receiver
+ will send a 220 "Service ready" reply when the connection is
+ completed. The sender SHOULD wait for this greeting message before
+ sending any commands.
+
+ Note: all the greeting-type replies have the official name (the
+ fully-qualified primary domain name) of the server host as the first
+ word following the reply code. Sometimes the host will have no
+ meaningful name. See 4.1.3 for a discussion of alternatives in these
+ situations.
+
+
+
+
+
+Klensin Standards Track [Page 47]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ For example,
+
+ 220 ISIF.USC.EDU Service ready
+ or
+ 220 mail.foo.com SuperSMTP v 6.1.2 Service ready
+ or
+ 220 [10.0.0.1] Clueless host service ready
+
+ The table below lists alternative success and failure replies for
+ each command. These SHOULD be strictly adhered to: a receiver may
+ substitute text in the replies, but the meaning and action implied by
+ the code numbers and by the specific command reply sequence cannot be
+ altered.
+
+4.3.2 Command-Reply Sequences
+
+ Each command is listed with its usual possible replies. The prefixes
+ used before the possible replies are "I" for intermediate, "S" for
+ success, and "E" for error. Since some servers may generate other
+ replies under special circumstances, and to allow for future
+ extension, SMTP clients SHOULD, when possible, interpret only the
+ first digit of the reply and MUST be prepared to deal with
+ unrecognized reply codes by interpreting the first digit only.
+ Unless extended using the mechanisms described in section 2.2, SMTP
+ servers MUST NOT transmit reply codes to an SMTP client that are
+ other than three digits or that do not start in a digit between 2 and
+ 5 inclusive.
+
+ These sequencing rules and, in principle, the codes themselves, can
+ be extended or modified by SMTP extensions offered by the server and
+ accepted (requested) by the client.
+
+ In addition to the codes listed below, any SMTP command can return
+ any of the following codes if the corresponding unusual circumstances
+ are encountered:
+
+ 500 For the "command line too long" case or if the command name was
+ not recognized. Note that producing a "command not recognized"
+ error in response to the required subset of these commands is a
+ violation of this specification.
+
+ 501 Syntax error in command or arguments. In order to provide for
+ future extensions, commands that are specified in this document as
+ not accepting arguments (DATA, RSET, QUIT) SHOULD return a 501
+ message if arguments are supplied in the absence of EHLO-
+ advertised extensions.
+
+ 421 Service shutting down and closing transmission channel
+
+
+
+Klensin Standards Track [Page 48]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ Specific sequences are:
+
+ CONNECTION ESTABLISHMENT
+ S: 220
+ E: 554
+ EHLO or HELO
+ S: 250
+ E: 504, 550
+ MAIL
+ S: 250
+ E: 552, 451, 452, 550, 553, 503
+ RCPT
+ S: 250, 251 (but see section 3.4 for discussion of 251 and 551)
+ E: 550, 551, 552, 553, 450, 451, 452, 503, 550
+ DATA
+ I: 354 -> data -> S: 250
+ E: 552, 554, 451, 452
+ E: 451, 554, 503
+ RSET
+ S: 250
+ VRFY
+ S: 250, 251, 252
+ E: 550, 551, 553, 502, 504
+ EXPN
+ S: 250, 252
+ E: 550, 500, 502, 504
+ HELP
+ S: 211, 214
+ E: 502, 504
+ NOOP
+ S: 250
+ QUIT
+ S: 221
+
+4.4 Trace Information
+
+ When an SMTP server receives a message for delivery or further
+ processing, it MUST insert trace ("time stamp" or "Received")
+ information at the beginning of the message content, as discussed in
+ section 4.1.1.4.
+
+ This line MUST be structured as follows:
+
+ - The FROM field, which MUST be supplied in an SMTP environment,
+ SHOULD contain both (1) the name of the source host as presented
+ in the EHLO command and (2) an address literal containing the IP
+ address of the source, determined from the TCP connection.
+
+
+
+
+Klensin Standards Track [Page 49]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ - The ID field MAY contain an "@" as suggested in RFC 822, but this
+ is not required.
+
+ - The FOR field MAY contain a list of <path> entries when multiple
+ RCPT commands have been given. This may raise some security
+ issues and is usually not desirable; see section 7.2.
+
+ An Internet mail program MUST NOT change a Received: line that was
+ previously added to the message header. SMTP servers MUST prepend
+ Received lines to messages; they MUST NOT change the order of
+ existing lines or insert Received lines in any other location.
+
+ As the Internet grows, comparability of Received fields is important
+ for detecting problems, especially slow relays. SMTP servers that
+ create Received fields SHOULD use explicit offsets in the dates
+ (e.g., -0800), rather than time zone names of any type. Local time
+ (with an offset) is preferred to UT when feasible. This formulation
+ allows slightly more information about local circumstances to be
+ specified. If UT is needed, the receiver need merely do some simple
+ arithmetic to convert the values. Use of UT loses information about
+ the time zone-location of the server. If it is desired to supply a
+ time zone name, it SHOULD be included in a comment.
+
+ When the delivery SMTP server makes the "final delivery" of a
+ message, it inserts a return-path line at the beginning of the mail
+ data. This use of return-path is required; mail systems MUST support
+ it. The return-path line preserves the information in the <reverse-
+ path> from the MAIL command. Here, final delivery means the message
+ has left the SMTP environment. Normally, this would mean it had been
+ delivered to the destination user or an associated mail drop, but in
+ some cases it may be further processed and transmitted by another
+ mail system.
+
+ It is possible for the mailbox in the return path to be different
+ from the actual sender's mailbox, for example, if error responses are
+ to be delivered to a special error handling mailbox rather than to
+ the message sender. When mailing lists are involved, this
+ arrangement is common and useful as a means of directing errors to
+ the list maintainer rather than the message originator.
+
+ The text above implies that the final mail data will begin with a
+ return path line, followed by one or more time stamp lines. These
+ lines will be followed by the mail data headers and body [32].
+
+ It is sometimes difficult for an SMTP server to determine whether or
+ not it is making final delivery since forwarding or other operations
+ may occur after the message is accepted for delivery. Consequently,
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ any further (forwarding, gateway, or relay) systems MAY remove the
+ return path and rebuild the MAIL command as needed to ensure that
+ exactly one such line appears in a delivered message.
+
+ A message-originating SMTP system SHOULD NOT send a message that
+ already contains a Return-path header. SMTP servers performing a
+ relay function MUST NOT inspect the message data, and especially not
+ to the extent needed to determine if Return-path headers are present.
+ SMTP servers making final delivery MAY remove Return-path headers
+ before adding their own.
+
+ The primary purpose of the Return-path is to designate the address to
+ which messages indicating non-delivery or other mail system failures
+ are to be sent. For this to be unambiguous, exactly one return path
+ SHOULD be present when the message is delivered. Systems using RFC
+ 822 syntax with non-SMTP transports SHOULD designate an unambiguous
+ address, associated with the transport envelope, to which error
+ reports (e.g., non-delivery messages) should be sent.
+
+ Historical note: Text in RFC 822 that appears to contradict the use
+ of the Return-path header (or the envelope reverse path address from
+ the MAIL command) as the destination for error messages is not
+ applicable on the Internet. The reverse path address (as copied into
+ the Return-path) MUST be used as the target of any mail containing
+ delivery error messages.
+
+ In particular:
+
+ - a gateway from SMTP->elsewhere SHOULD insert a return-path header,
+ unless it is known that the "elsewhere" transport also uses
+ Internet domain addresses and maintains the envelope sender
+ address separately.
+
+ - a gateway from elsewhere->SMTP SHOULD delete any return-path
+ header present in the message, and either copy that information to
+ the SMTP envelope or combine it with information present in the
+ envelope of the other transport system to construct the reverse
+ path argument to the MAIL command in the SMTP envelope.
+
+ The server must give special treatment to cases in which the
+ processing following the end of mail data indication is only
+ partially successful. This could happen if, after accepting several
+ recipients and the mail data, the SMTP server finds that the mail
+ data could be successfully delivered to some, but not all, of the
+ recipients. In such cases, the response to the DATA command MUST be
+ an OK reply. However, the SMTP server MUST compose and send an
+ "undeliverable mail" notification message to the originator of the
+ message.
+
+
+
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+
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+
+
+ A single notification listing all of the failed recipients or
+ separate notification messages MUST be sent for each failed
+ recipient. For economy of processing by the sender, the former is
+ preferred when possible. All undeliverable mail notification
+ messages are sent using the MAIL command (even if they result from
+ processing the obsolete SEND, SOML, or SAML commands) and use a null
+ return path as discussed in section 3.7.
+
+ The time stamp line and the return path line are formally defined as
+ follows:
+
+Return-path-line = "Return-Path:" FWS Reverse-path <CRLF>
+
+Time-stamp-line = "Received:" FWS Stamp <CRLF>
+
+Stamp = From-domain By-domain Opt-info ";" FWS date-time
+
+ ; where "date-time" is as defined in [32]
+ ; but the "obs-" forms, especially two-digit
+ ; years, are prohibited in SMTP and MUST NOT be used.
+
+From-domain = "FROM" FWS Extended-Domain CFWS
+
+By-domain = "BY" FWS Extended-Domain CFWS
+
+Extended-Domain = Domain /
+ ( Domain FWS "(" TCP-info ")" ) /
+ ( Address-literal FWS "(" TCP-info ")" )
+
+TCP-info = Address-literal / ( Domain FWS Address-literal )
+ ; Information derived by server from TCP connection
+ ; not client EHLO.
+
+Opt-info = [Via] [With] [ID] [For]
+
+Via = "VIA" FWS Link CFWS
+
+With = "WITH" FWS Protocol CFWS
+
+ID = "ID" FWS String / msg-id CFWS
+
+For = "FOR" FWS 1*( Path / Mailbox ) CFWS
+
+Link = "TCP" / Addtl-Link
+Addtl-Link = Atom
+ ; Additional standard names for links are registered with the
+ ; Internet Assigned Numbers Authority (IANA). "Via" is
+ ; primarily of value with non-Internet transports. SMTP
+
+
+
+Klensin Standards Track [Page 52]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ ; servers SHOULD NOT use unregistered names.
+Protocol = "ESMTP" / "SMTP" / Attdl-Protocol
+Attdl-Protocol = Atom
+ ; Additional standard names for protocols are registered with the
+ ; Internet Assigned Numbers Authority (IANA). SMTP servers
+ ; SHOULD NOT use unregistered names.
+
+4.5 Additional Implementation Issues
+
+4.5.1 Minimum Implementation
+
+ In order to make SMTP workable, the following minimum implementation
+ is required for all receivers. The following commands MUST be
+ supported to conform to this specification:
+
+ EHLO
+ HELO
+ MAIL
+ RCPT
+ DATA
+ RSET
+ NOOP
+ QUIT
+ VRFY
+
+ Any system that includes an SMTP server supporting mail relaying or
+ delivery MUST support the reserved mailbox "postmaster" as a case-
+ insensitive local name. This postmaster address is not strictly
+ necessary if the server always returns 554 on connection opening (as
+ described in section 3.1). The requirement to accept mail for
+ postmaster implies that RCPT commands which specify a mailbox for
+ postmaster at any of the domains for which the SMTP server provides
+ mail service, as well as the special case of "RCPT TO:<Postmaster>"
+ (with no domain specification), MUST be supported.
+
+ SMTP systems are expected to make every reasonable effort to accept
+ mail directed to Postmaster from any other system on the Internet.
+ In extreme cases --such as to contain a denial of service attack or
+ other breach of security-- an SMTP server may block mail directed to
+ Postmaster. However, such arrangements SHOULD be narrowly tailored
+ so as to avoid blocking messages which are not part of such attacks.
+
+4.5.2 Transparency
+
+ Without some provision for data transparency, the character sequence
+ "<CRLF>.<CRLF>" ends the mail text and cannot be sent by the user.
+ In general, users are not aware of such "forbidden" sequences. To
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ allow all user composed text to be transmitted transparently, the
+ following procedures are used:
+
+ - Before sending a line of mail text, the SMTP client checks the
+ first character of the line. If it is a period, one additional
+ period is inserted at the beginning of the line.
+
+ - When a line of mail text is received by the SMTP server, it checks
+ the line. If the line is composed of a single period, it is
+ treated as the end of mail indicator. If the first character is a
+ period and there are other characters on the line, the first
+ character is deleted.
+
+ The mail data may contain any of the 128 ASCII characters. All
+ characters are to be delivered to the recipient's mailbox, including
+ spaces, vertical and horizontal tabs, and other control characters.
+ If the transmission channel provides an 8-bit byte (octet) data
+ stream, the 7-bit ASCII codes are transmitted right justified in the
+ octets, with the high order bits cleared to zero. See 3.7 for
+ special treatment of these conditions in SMTP systems serving a relay
+ function.
+
+ In some systems it may be necessary to transform the data as it is
+ received and stored. This may be necessary for hosts that use a
+ different character set than ASCII as their local character set, that
+ store data in records rather than strings, or which use special
+ character sequences as delimiters inside mailboxes. If such
+ transformations are necessary, they MUST be reversible, especially if
+ they are applied to mail being relayed.
+
+4.5.3 Sizes and Timeouts
+
+4.5.3.1 Size limits and minimums
+
+ There are several objects that have required minimum/maximum sizes.
+ Every implementation MUST be able to receive objects of at least
+ these sizes. Objects larger than these sizes SHOULD be avoided when
+ possible. However, some Internet mail constructs such as encoded
+ X.400 addresses [16] will often require larger objects: clients MAY
+ attempt to transmit these, but MUST be prepared for a server to
+ reject them if they cannot be handled by it. To the maximum extent
+ possible, implementation techniques which impose no limits on the
+ length of these objects should be used.
+
+ local-part
+ The maximum total length of a user name or other local-part is 64
+ characters.
+
+
+
+
+Klensin Standards Track [Page 54]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ domain
+ The maximum total length of a domain name or number is 255
+ characters.
+
+ path
+ The maximum total length of a reverse-path or forward-path is 256
+ characters (including the punctuation and element separators).
+
+ command line
+ The maximum total length of a command line including the command
+ word and the <CRLF> is 512 characters. SMTP extensions may be
+ used to increase this limit.
+
+ reply line
+ The maximum total length of a reply line including the reply code
+ and the <CRLF> is 512 characters. More information may be
+ conveyed through multiple-line replies.
+
+ text line
+ The maximum total length of a text line including the <CRLF> is
+ 1000 characters (not counting the leading dot duplicated for
+ transparency). This number may be increased by the use of SMTP
+ Service Extensions.
+
+ message content
+ The maximum total length of a message content (including any
+ message headers as well as the message body) MUST BE at least 64K
+ octets. Since the introduction of Internet standards for
+ multimedia mail [12], message lengths on the Internet have grown
+ dramatically, and message size restrictions should be avoided if
+ at all possible. SMTP server systems that must impose
+ restrictions SHOULD implement the "SIZE" service extension [18],
+ and SMTP client systems that will send large messages SHOULD
+ utilize it when possible.
+
+ recipients buffer
+ The minimum total number of recipients that must be buffered is
+ 100 recipients. Rejection of messages (for excessive recipients)
+ with fewer than 100 RCPT commands is a violation of this
+ specification. The general principle that relaying SMTP servers
+ MUST NOT, and delivery SMTP servers SHOULD NOT, perform validation
+ tests on message headers suggests that rejecting a message based
+ on the total number of recipients shown in header fields is to be
+ discouraged. A server which imposes a limit on the number of
+ recipients MUST behave in an orderly fashion, such as to reject
+ additional addresses over its limit rather than silently
+ discarding addresses previously accepted. A client that needs to
+
+
+
+
+Klensin Standards Track [Page 55]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ deliver a message containing over 100 RCPT commands SHOULD be
+ prepared to transmit in 100-recipient "chunks" if the server
+ declines to accept more than 100 recipients in a single message.
+
+ Errors due to exceeding these limits may be reported by using the
+ reply codes. Some examples of reply codes are:
+
+ 500 Line too long.
+ or
+ 501 Path too long
+ or
+ 452 Too many recipients (see below)
+ or
+ 552 Too much mail data.
+
+ RFC 821 [30] incorrectly listed the error where an SMTP server
+ exhausts its implementation limit on the number of RCPT commands
+ ("too many recipients") as having reply code 552. The correct reply
+ code for this condition is 452. Clients SHOULD treat a 552 code in
+ this case as a temporary, rather than permanent, failure so the logic
+ below works.
+
+ When a conforming SMTP server encounters this condition, it has at
+ least 100 successful RCPT commands in its recipients buffer. If the
+ server is able to accept the message, then at least these 100
+ addresses will be removed from the SMTP client's queue. When the
+ client attempts retransmission of those addresses which received 452
+ responses, at least 100 of these will be able to fit in the SMTP
+ server's recipients buffer. Each retransmission attempt which is
+ able to deliver anything will be able to dispose of at least 100 of
+ these recipients.
+
+ If an SMTP server has an implementation limit on the number of RCPT
+ commands and this limit is exhausted, it MUST use a response code of
+ 452 (but the client SHOULD also be prepared for a 552, as noted
+ above). If the server has a configured site-policy limitation on the
+ number of RCPT commands, it MAY instead use a 5XX response code.
+ This would be most appropriate if the policy limitation was intended
+ to apply if the total recipient count for a particular message body
+ were enforced even if that message body was sent in multiple mail
+ transactions.
+
+4.5.3.2 Timeouts
+
+ An SMTP client MUST provide a timeout mechanism. It MUST use per-
+ command timeouts rather than somehow trying to time the entire mail
+ transaction. Timeouts SHOULD be easily reconfigurable, preferably
+ without recompiling the SMTP code. To implement this, a timer is set
+
+
+
+Klensin Standards Track [Page 56]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ for each SMTP command and for each buffer of the data transfer. The
+ latter means that the overall timeout is inherently proportional to
+ the size of the message.
+
+ Based on extensive experience with busy mail-relay hosts, the minimum
+ per-command timeout values SHOULD be as follows:
+
+ Initial 220 Message: 5 minutes
+ An SMTP client process needs to distinguish between a failed TCP
+ connection and a delay in receiving the initial 220 greeting
+ message. Many SMTP servers accept a TCP connection but delay
+ delivery of the 220 message until their system load permits more
+ mail to be processed.
+
+ MAIL Command: 5 minutes
+
+ RCPT Command: 5 minutes
+ A longer timeout is required if processing of mailing lists and
+ aliases is not deferred until after the message was accepted.
+
+ DATA Initiation: 2 minutes
+ This is while awaiting the "354 Start Input" reply to a DATA
+ command.
+
+ Data Block: 3 minutes
+ This is while awaiting the completion of each TCP SEND call
+ transmitting a chunk of data.
+
+ DATA Termination: 10 minutes.
+ This is while awaiting the "250 OK" reply. When the receiver gets
+ the final period terminating the message data, it typically
+ performs processing to deliver the message to a user mailbox. A
+ spurious timeout at this point would be very wasteful and would
+ typically result in delivery of multiple copies of the message,
+ since it has been successfully sent and the server has accepted
+ responsibility for delivery. See section 6.1 for additional
+ discussion.
+
+ An SMTP server SHOULD have a timeout of at least 5 minutes while it
+ is awaiting the next command from the sender.
+
+4.5.4 Retry Strategies
+
+ The common structure of a host SMTP implementation includes user
+ mailboxes, one or more areas for queuing messages in transit, and one
+ or more daemon processes for sending and receiving mail. The exact
+ structure will vary depending on the needs of the users on the host
+
+
+
+
+Klensin Standards Track [Page 57]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ and the number and size of mailing lists supported by the host. We
+ describe several optimizations that have proved helpful, particularly
+ for mailers supporting high traffic levels.
+
+ Any queuing strategy MUST include timeouts on all activities on a
+ per-command basis. A queuing strategy MUST NOT send error messages
+ in response to error messages under any circumstances.
+
+4.5.4.1 Sending Strategy
+
+ The general model for an SMTP client is one or more processes that
+ periodically attempt to transmit outgoing mail. In a typical system,
+ the program that composes a message has some method for requesting
+ immediate attention for a new piece of outgoing mail, while mail that
+ cannot be transmitted immediately MUST be queued and periodically
+ retried by the sender. A mail queue entry will include not only the
+ message itself but also the envelope information.
+
+ The sender MUST delay retrying a particular destination after one
+ attempt has failed. In general, the retry interval SHOULD be at
+ least 30 minutes; however, more sophisticated and variable strategies
+ will be beneficial when the SMTP client can determine the reason for
+ non-delivery.
+
+ Retries continue until the message is transmitted or the sender gives
+ up; the give-up time generally needs to be at least 4-5 days. The
+ parameters to the retry algorithm MUST be configurable.
+
+ A client SHOULD keep a list of hosts it cannot reach and
+ corresponding connection timeouts, rather than just retrying queued
+ mail items.
+
+ Experience suggests that failures are typically transient (the target
+ system or its connection has crashed), favoring a policy of two
+ connection attempts in the first hour the message is in the queue,
+ and then backing off to one every two or three hours.
+
+ The SMTP client can shorten the queuing delay in cooperation with the
+ SMTP server. For example, if mail is received from a particular
+ address, it is likely that mail queued for that host can now be sent.
+ Application of this principle may, in many cases, eliminate the
+ requirement for an explicit "send queues now" function such as ETRN
+ [9].
+
+ The strategy may be further modified as a result of multiple
+ addresses per host (see below) to optimize delivery time vs. resource
+ usage.
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ An SMTP client may have a large queue of messages for each
+ unavailable destination host. If all of these messages were retried
+ in every retry cycle, there would be excessive Internet overhead and
+ the sending system would be blocked for a long period. Note that an
+ SMTP client can generally determine that a delivery attempt has
+ failed only after a timeout of several minutes and even a one-minute
+ timeout per connection will result in a very large delay if retries
+ are repeated for dozens, or even hundreds, of queued messages to the
+ same host.
+
+ At the same time, SMTP clients SHOULD use great care in caching
+ negative responses from servers. In an extreme case, if EHLO is
+ issued multiple times during the same SMTP connection, different
+ answers may be returned by the server. More significantly, 5yz
+ responses to the MAIL command MUST NOT be cached.
+
+ When a mail message is to be delivered to multiple recipients, and
+ the SMTP server to which a copy of the message is to be sent is the
+ same for multiple recipients, then only one copy of the message
+ SHOULD be transmitted. That is, the SMTP client SHOULD use the
+ command sequence: MAIL, RCPT, RCPT,... RCPT, DATA instead of the
+ sequence: MAIL, RCPT, DATA, ..., MAIL, RCPT, DATA. However, if there
+ are very many addresses, a limit on the number of RCPT commands per
+ MAIL command MAY be imposed. Implementation of this efficiency
+ feature is strongly encouraged.
+
+ Similarly, to achieve timely delivery, the SMTP client MAY support
+ multiple concurrent outgoing mail transactions. However, some limit
+ may be appropriate to protect the host from devoting all its
+ resources to mail.
+
+4.5.4.2 Receiving Strategy
+
+ The SMTP server SHOULD attempt to keep a pending listen on the SMTP
+ port at all times. This requires the support of multiple incoming
+ TCP connections for SMTP. Some limit MAY be imposed but servers that
+ cannot handle more than one SMTP transaction at a time are not in
+ conformance with the intent of this specification.
+
+ As discussed above, when the SMTP server receives mail from a
+ particular host address, it could activate its own SMTP queuing
+ mechanisms to retry any mail pending for that host address.
+
+4.5.5 Messages with a null reverse-path
+
+ There are several types of notification messages which are required
+ by existing and proposed standards to be sent with a null reverse
+ path, namely non-delivery notifications as discussed in section 3.7,
+
+
+
+Klensin Standards Track [Page 59]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ other kinds of Delivery Status Notifications (DSNs) [24], and also
+ Message Disposition Notifications (MDNs) [10]. All of these kinds of
+ messages are notifications about a previous message, and they are
+ sent to the reverse-path of the previous mail message. (If the
+ delivery of such a notification message fails, that usually indicates
+ a problem with the mail system of the host to which the notification
+ message is addressed. For this reason, at some hosts the MTA is set
+ up to forward such failed notification messages to someone who is
+ able to fix problems with the mail system, e.g., via the postmaster
+ alias.)
+
+ All other types of messages (i.e., any message which is not required
+ by a standards-track RFC to have a null reverse-path) SHOULD be sent
+ with with a valid, non-null reverse-path.
+
+ Implementors of automated email processors should be careful to make
+ sure that the various kinds of messages with null reverse-path are
+ handled correctly, in particular such systems SHOULD NOT reply to
+ messages with null reverse-path.
+
+5. Address Resolution and Mail Handling
+
+ Once an SMTP client lexically identifies a domain to which mail will
+ be delivered for processing (as described in sections 3.6 and 3.7), a
+ DNS lookup MUST be performed to resolve the domain name [22]. The
+ names are expected to be fully-qualified domain names (FQDNs):
+ mechanisms for inferring FQDNs from partial names or local aliases
+ are outside of this specification and, due to a history of problems,
+ are generally discouraged. The lookup first attempts to locate an MX
+ record associated with the name. If a CNAME record is found instead,
+ the resulting name is processed as if it were the initial name. If
+ no MX records are found, but an A RR is found, the A RR is treated as
+ if it was associated with an implicit MX RR, with a preference of 0,
+ pointing to that host. If one or more MX RRs are found for a given
+ name, SMTP systems MUST NOT utilize any A RRs associated with that
+ name unless they are located using the MX RRs; the "implicit MX" rule
+ above applies only if there are no MX records present. If MX records
+ are present, but none of them are usable, this situation MUST be
+ reported as an error.
+
+ When the lookup succeeds, the mapping can result in a list of
+ alternative delivery addresses rather than a single address, because
+ of multiple MX records, multihoming, or both. To provide reliable
+ mail transmission, the SMTP client MUST be able to try (and retry)
+ each of the relevant addresses in this list in order, until a
+ delivery attempt succeeds. However, there MAY also be a configurable
+ limit on the number of alternate addresses that can be tried. In any
+ case, the SMTP client SHOULD try at least two addresses.
+
+
+
+Klensin Standards Track [Page 60]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ Two types of information is used to rank the host addresses: multiple
+ MX records, and multihomed hosts.
+
+ Multiple MX records contain a preference indication that MUST be used
+ in sorting (see below). Lower numbers are more preferred than higher
+ ones. If there are multiple destinations with the same preference
+ and there is no clear reason to favor one (e.g., by recognition of an
+ easily-reached address), then the sender-SMTP MUST randomize them to
+ spread the load across multiple mail exchangers for a specific
+ organization.
+
+ The destination host (perhaps taken from the preferred MX record) may
+ be multihomed, in which case the domain name resolver will return a
+ list of alternative IP addresses. It is the responsibility of the
+ domain name resolver interface to have ordered this list by
+ decreasing preference if necessary, and SMTP MUST try them in the
+ order presented.
+
+ Although the capability to try multiple alternative addresses is
+ required, specific installations may want to limit or disable the use
+ of alternative addresses. The question of whether a sender should
+ attempt retries using the different addresses of a multihomed host
+ has been controversial. The main argument for using the multiple
+ addresses is that it maximizes the probability of timely delivery,
+ and indeed sometimes the probability of any delivery; the counter-
+ argument is that it may result in unnecessary resource use. Note
+ that resource use is also strongly determined by the sending strategy
+ discussed in section 4.5.4.1.
+
+ If an SMTP server receives a message with a destination for which it
+ is a designated Mail eXchanger, it MAY relay the message (potentially
+ after having rewritten the MAIL FROM and/or RCPT TO addresses), make
+ final delivery of the message, or hand it off using some mechanism
+ outside the SMTP-provided transport environment. Of course, neither
+ of the latter require that the list of MX records be examined
+ further.
+
+ If it determines that it should relay the message without rewriting
+ the address, it MUST sort the MX records to determine candidates for
+ delivery. The records are first ordered by preference, with the
+ lowest-numbered records being most preferred. The relay host MUST
+ then inspect the list for any of the names or addresses by which it
+ might be known in mail transactions. If a matching record is found,
+ all records at that preference level and higher-numbered ones MUST be
+ discarded from consideration. If there are no records left at that
+ point, it is an error condition, and the message MUST be returned as
+ undeliverable. If records do remain, they SHOULD be tried, best
+ preference first, as described above.
+
+
+
+Klensin Standards Track [Page 61]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+6. Problem Detection and Handling
+
+6.1 Reliable Delivery and Replies by Email
+
+ When the receiver-SMTP accepts a piece of mail (by sending a "250 OK"
+ message in response to DATA), it is accepting responsibility for
+ delivering or relaying the message. It must take this responsibility
+ seriously. It MUST NOT lose the message for frivolous reasons, such
+ as because the host later crashes or because of a predictable
+ resource shortage.
+
+ If there is a delivery failure after acceptance of a message, the
+ receiver-SMTP MUST formulate and mail a notification message. This
+ notification MUST be sent using a null ("<>") reverse path in the
+ envelope. The recipient of this notification MUST be the address
+ from the envelope return path (or the Return-Path: line). However,
+ if this address is null ("<>"), the receiver-SMTP MUST NOT send a
+ notification. Obviously, nothing in this section can or should
+ prohibit local decisions (i.e., as part of the same system
+ environment as the receiver-SMTP) to log or otherwise transmit
+ information about null address events locally if that is desired. If
+ the address is an explicit source route, it MUST be stripped down to
+ its final hop.
+
+ For example, suppose that an error notification must be sent for a
+ message that arrived with:
+
+ MAIL FROM:<@a,@b:user@d>
+
+ The notification message MUST be sent using:
+
+ RCPT TO:<user@d>
+
+ Some delivery failures after the message is accepted by SMTP will be
+ unavoidable. For example, it may be impossible for the receiving
+ SMTP server to validate all the delivery addresses in RCPT command(s)
+ due to a "soft" domain system error, because the target is a mailing
+ list (see earlier discussion of RCPT), or because the server is
+ acting as a relay and has no immediate access to the delivering
+ system.
+
+ To avoid receiving duplicate messages as the result of timeouts, a
+ receiver-SMTP MUST seek to minimize the time required to respond to
+ the final <CRLF>.<CRLF> end of data indicator. See RFC 1047 [28] for
+ a discussion of this problem.
+
+
+
+
+
+
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+
+
+6.2 Loop Detection
+
+ Simple counting of the number of "Received:" headers in a message has
+ proven to be an effective, although rarely optimal, method of
+ detecting loops in mail systems. SMTP servers using this technique
+ SHOULD use a large rejection threshold, normally at least 100
+ Received entries. Whatever mechanisms are used, servers MUST contain
+ provisions for detecting and stopping trivial loops.
+
+6.3 Compensating for Irregularities
+
+ Unfortunately, variations, creative interpretations, and outright
+ violations of Internet mail protocols do occur; some would suggest
+ that they occur quite frequently. The debate as to whether a well-
+ behaved SMTP receiver or relay should reject a malformed message,
+ attempt to pass it on unchanged, or attempt to repair it to increase
+ the odds of successful delivery (or subsequent reply) began almost
+ with the dawn of structured network mail and shows no signs of
+ abating. Advocates of rejection claim that attempted repairs are
+ rarely completely adequate and that rejection of bad messages is the
+ only way to get the offending software repaired. Advocates of
+ "repair" or "deliver no matter what" argue that users prefer that
+ mail go through it if at all possible and that there are significant
+ market pressures in that direction. In practice, these market
+ pressures may be more important to particular vendors than strict
+ conformance to the standards, regardless of the preference of the
+ actual developers.
+
+ The problems associated with ill-formed messages were exacerbated by
+ the introduction of the split-UA mail reading protocols [3, 26, 5,
+ 21]. These protocols have encouraged the use of SMTP as a posting
+ protocol, and SMTP servers as relay systems for these client hosts
+ (which are often only intermittently connected to the Internet).
+ Historically, many of those client machines lacked some of the
+ mechanisms and information assumed by SMTP (and indeed, by the mail
+ format protocol [7]). Some could not keep adequate track of time;
+ others had no concept of time zones; still others could not identify
+ their own names or addresses; and, of course, none could satisfy the
+ assumptions that underlay RFC 822's conception of authenticated
+ addresses.
+
+ In response to these weak SMTP clients, many SMTP systems now
+ complete messages that are delivered to them in incomplete or
+ incorrect form. This strategy is generally considered appropriate
+ when the server can identify or authenticate the client, and there
+ are prior agreements between them. By contrast, there is at best
+ great concern about fixes applied by a relay or delivery SMTP server
+ that has little or no knowledge of the user or client machine.
+
+
+
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+
+
+ The following changes to a message being processed MAY be applied
+ when necessary by an originating SMTP server, or one used as the
+ target of SMTP as an initial posting protocol:
+
+ - Addition of a message-id field when none appears
+
+ - Addition of a date, time or time zone when none appears
+
+ - Correction of addresses to proper FQDN format
+
+ The less information the server has about the client, the less likely
+ these changes are to be correct and the more caution and conservatism
+ should be applied when considering whether or not to perform fixes
+ and how. These changes MUST NOT be applied by an SMTP server that
+ provides an intermediate relay function.
+
+ In all cases, properly-operating clients supplying correct
+ information are preferred to corrections by the SMTP server. In all
+ cases, documentation of actions performed by the servers (in trace
+ fields and/or header comments) is strongly encouraged.
+
+7. Security Considerations
+
+7.1 Mail Security and Spoofing
+
+ SMTP mail is inherently insecure in that it is feasible for even
+ fairly casual users to negotiate directly with receiving and relaying
+ SMTP servers and create messages that will trick a naive recipient
+ into believing that they came from somewhere else. Constructing such
+ a message so that the "spoofed" behavior cannot be detected by an
+ expert is somewhat more difficult, but not sufficiently so as to be a
+ deterrent to someone who is determined and knowledgeable.
+ Consequently, as knowledge of Internet mail increases, so does the
+ knowledge that SMTP mail inherently cannot be authenticated, or
+ integrity checks provided, at the transport level. Real mail
+ security lies only in end-to-end methods involving the message
+ bodies, such as those which use digital signatures (see [14] and,
+ e.g., PGP [4] or S/MIME [31]).
+
+ Various protocol extensions and configuration options that provide
+ authentication at the transport level (e.g., from an SMTP client to
+ an SMTP server) improve somewhat on the traditional situation
+ described above. However, unless they are accompanied by careful
+ handoffs of responsibility in a carefully-designed trust environment,
+ they remain inherently weaker than end-to-end mechanisms which use
+ digitally signed messages rather than depending on the integrity of
+ the transport system.
+
+
+
+
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+
+
+ Efforts to make it more difficult for users to set envelope return
+ path and header "From" fields to point to valid addresses other than
+ their own are largely misguided: they frustrate legitimate
+ applications in which mail is sent by one user on behalf of another
+ or in which error (or normal) replies should be directed to a special
+ address. (Systems that provide convenient ways for users to alter
+ these fields on a per-message basis should attempt to establish a
+ primary and permanent mailbox address for the user so that Sender
+ fields within the message data can be generated sensibly.)
+
+ This specification does not further address the authentication issues
+ associated with SMTP other than to advocate that useful functionality
+ not be disabled in the hope of providing some small margin of
+ protection against an ignorant user who is trying to fake mail.
+
+7.2 "Blind" Copies
+
+ Addresses that do not appear in the message headers may appear in the
+ RCPT commands to an SMTP server for a number of reasons. The two
+ most common involve the use of a mailing address as a "list exploder"
+ (a single address that resolves into multiple addresses) and the
+ appearance of "blind copies". Especially when more than one RCPT
+ command is present, and in order to avoid defeating some of the
+ purpose of these mechanisms, SMTP clients and servers SHOULD NOT copy
+ the full set of RCPT command arguments into the headers, either as
+ part of trace headers or as informational or private-extension
+ headers. Since this rule is often violated in practice, and cannot
+ be enforced, sending SMTP systems that are aware of "bcc" use MAY
+ find it helpful to send each blind copy as a separate message
+ transaction containing only a single RCPT command.
+
+ There is no inherent relationship between either "reverse" (from
+ MAIL, SAML, etc., commands) or "forward" (RCPT) addresses in the SMTP
+ transaction ("envelope") and the addresses in the headers. Receiving
+ systems SHOULD NOT attempt to deduce such relationships and use them
+ to alter the headers of the message for delivery. The popular
+ "Apparently-to" header is a violation of this principle as well as a
+ common source of unintended information disclosure and SHOULD NOT be
+ used.
+
+7.3 VRFY, EXPN, and Security
+
+ As discussed in section 3.5, individual sites may want to disable
+ either or both of VRFY or EXPN for security reasons. As a corollary
+ to the above, implementations that permit this MUST NOT appear to
+ have verified addresses that are not, in fact, verified. If a site
+
+
+
+
+
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+
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+
+
+ disables these commands for security reasons, the SMTP server MUST
+ return a 252 response, rather than a code that could be confused with
+ successful or unsuccessful verification.
+
+ Returning a 250 reply code with the address listed in the VRFY
+ command after having checked it only for syntax violates this rule.
+ Of course, an implementation that "supports" VRFY by always returning
+ 550 whether or not the address is valid is equally not in
+ conformance.
+
+ Within the last few years, the contents of mailing lists have become
+ popular as an address information source for so-called "spammers."
+ The use of EXPN to "harvest" addresses has increased as list
+ administrators have installed protections against inappropriate uses
+ of the lists themselves. Implementations SHOULD still provide
+ support for EXPN, but sites SHOULD carefully evaluate the tradeoffs.
+ As authentication mechanisms are introduced into SMTP, some sites may
+ choose to make EXPN available only to authenticated requestors.
+
+7.4 Information Disclosure in Announcements
+
+ There has been an ongoing debate about the tradeoffs between the
+ debugging advantages of announcing server type and version (and,
+ sometimes, even server domain name) in the greeting response or in
+ response to the HELP command and the disadvantages of exposing
+ information that might be useful in a potential hostile attack. The
+ utility of the debugging information is beyond doubt. Those who
+ argue for making it available point out that it is far better to
+ actually secure an SMTP server rather than hope that trying to
+ conceal known vulnerabilities by hiding the server's precise identity
+ will provide more protection. Sites are encouraged to evaluate the
+ tradeoff with that issue in mind; implementations are strongly
+ encouraged to minimally provide for making type and version
+ information available in some way to other network hosts.
+
+7.5 Information Disclosure in Trace Fields
+
+ In some circumstances, such as when mail originates from within a LAN
+ whose hosts are not directly on the public Internet, trace
+ ("Received") fields produced in conformance with this specification
+ may disclose host names and similar information that would not
+ normally be available. This ordinarily does not pose a problem, but
+ sites with special concerns about name disclosure should be aware of
+ it. Also, the optional FOR clause should be supplied with caution or
+ not at all when multiple recipients are involved lest it
+ inadvertently disclose the identities of "blind copy" recipients to
+ others.
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+7.6 Information Disclosure in Message Forwarding
+
+ As discussed in section 3.4, use of the 251 or 551 reply codes to
+ identify the replacement address associated with a mailbox may
+ inadvertently disclose sensitive information. Sites that are
+ concerned about those issues should ensure that they select and
+ configure servers appropriately.
+
+7.7 Scope of Operation of SMTP Servers
+
+ It is a well-established principle that an SMTP server may refuse to
+ accept mail for any operational or technical reason that makes sense
+ to the site providing the server. However, cooperation among sites
+ and installations makes the Internet possible. If sites take
+ excessive advantage of the right to reject traffic, the ubiquity of
+ email availability (one of the strengths of the Internet) will be
+ threatened; considerable care should be taken and balance maintained
+ if a site decides to be selective about the traffic it will accept
+ and process.
+
+ In recent years, use of the relay function through arbitrary sites
+ has been used as part of hostile efforts to hide the actual origins
+ of mail. Some sites have decided to limit the use of the relay
+ function to known or identifiable sources, and implementations SHOULD
+ provide the capability to perform this type of filtering. When mail
+ is rejected for these or other policy reasons, a 550 code SHOULD be
+ used in response to EHLO, MAIL, or RCPT as appropriate.
+
+8. IANA Considerations
+
+ IANA will maintain three registries in support of this specification.
+ The first consists of SMTP service extensions with the associated
+ keywords, and, as needed, parameters and verbs. As specified in
+ section 2.2.2, no entry may be made in this registry that starts in
+ an "X". Entries may be made only for service extensions (and
+ associated keywords, parameters, or verbs) that are defined in
+ standards-track or experimental RFCs specifically approved by the
+ IESG for this purpose.
+
+ The second registry consists of "tags" that identify forms of domain
+ literals other than those for IPv4 addresses (specified in RFC 821
+ and in this document) and IPv6 addresses (specified in this
+ document). Additional literal types require standardization before
+ being used; none are anticipated at this time.
+
+ The third, established by RFC 821 and renewed by this specification,
+ is a registry of link and protocol identifiers to be used with the
+ "via" and "with" subclauses of the time stamp ("Received: header")
+
+
+
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+
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+
+
+ described in section 4.4. Link and protocol identifiers in addition
+ to those specified in this document may be registered only by
+ standardization or by way of an RFC-documented, IESG-approved,
+ Experimental protocol extension.
+
+9. References
+
+ [1] American National Standards Institute (formerly United States of
+ America Standards Institute), X3.4, 1968, "USA Code for
+ Information Interchange". ANSI X3.4-1968 has been replaced by
+ newer versions with slight modifications, but the 1968 version
+ remains definitive for the Internet.
+
+ [2] Braden, R., "Requirements for Internet hosts - application and
+ support", STD 3, RFC 1123, October 1989.
+
+ [3] Butler, M., Chase, D., Goldberger, J., Postel, J. and J.
+ Reynolds, "Post Office Protocol - version 2", RFC 937, February
+ 1985.
+
+ [4] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer, "OpenPGP
+ Message Format", RFC 2440, November 1998.
+
+ [5] Crispin, M., "Interactive Mail Access Protocol - Version 2", RFC
+ 1176, August 1990.
+
+ [6] Crispin, M., "Internet Message Access Protocol - Version 4", RFC
+ 2060, December 1996.
+
+ [7] Crocker, D., "Standard for the Format of ARPA Internet Text
+ Messages", RFC 822, August 1982.
+
+ [8] Crocker, D. and P. Overell, Eds., "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+ [9] De Winter, J., "SMTP Service Extension for Remote Message Queue
+ Starting", RFC 1985, August 1996.
+
+ [10] Fajman, R., "An Extensible Message Format for Message
+ Disposition Notifications", RFC 2298, March 1998.
+
+ [11] Freed, N, "Behavior of and Requirements for Internet Firewalls",
+ RFC 2979, October 2000.
+
+ [12] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message Bodies",
+ RFC 2045, December 1996.
+
+
+
+
+Klensin Standards Track [Page 68]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ [13] Freed, N., "SMTP Service Extension for Command Pipelining", RFC
+ 2920, September 2000.
+
+ [14] Galvin, J., Murphy, S., Crocker, S. and N. Freed, "Security
+ Multiparts for MIME: Multipart/Signed and Multipart/Encrypted",
+ RFC 1847, October 1995.
+
+ [15] Gellens, R. and J. Klensin, "Message Submission", RFC 2476,
+ December 1998.
+
+ [16] Kille, S., "Mapping between X.400 and RFC822/MIME", RFC 2156,
+ January 1998.
+
+ [17] Hinden, R and S. Deering, Eds. "IP Version 6 Addressing
+ Architecture", RFC 2373, July 1998.
+
+ [18] Klensin, J., Freed, N. and K. Moore, "SMTP Service Extension for
+ Message Size Declaration", STD 10, RFC 1870, November 1995.
+
+ [19] Klensin, J., Freed, N., Rose, M., Stefferud, E. and D. Crocker,
+ "SMTP Service Extensions", STD 10, RFC 1869, November 1995.
+
+ [20] Klensin, J., Freed, N., Rose, M., Stefferud, E. and D. Crocker,
+ "SMTP Service Extension for 8bit-MIMEtransport", RFC 1652, July
+ 1994.
+
+ [21] Lambert, M., "PCMAIL: A distributed mail system for personal
+ computers", RFC 1056, July 1988.
+
+ [22] Mockapetris, P., "Domain names - implementation and
+ specification", STD 13, RFC 1035, November 1987.
+
+ Mockapetris, P., "Domain names - concepts and facilities", STD
+ 13, RFC 1034, November 1987.
+
+ [23] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
+ Three: Message Header Extensions for Non-ASCII Text", RFC 2047,
+ December 1996.
+
+ [24] Moore, K., "SMTP Service Extension for Delivery Status
+ Notifications", RFC 1891, January 1996.
+
+ [25] Moore, K., and G. Vaudreuil, "An Extensible Message Format for
+ Delivery Status Notifications", RFC 1894, January 1996.
+
+ [26] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD
+ 53, RFC 1939, May 1996.
+
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ [27] Partridge, C., "Mail routing and the domain system", RFC 974,
+ January 1986.
+
+ [28] Partridge, C., "Duplicate messages and SMTP", RFC 1047, February
+ 1988.
+
+ [29] Postel, J., ed., "Transmission Control Protocol - DARPA Internet
+ Program Protocol Specification", STD 7, RFC 793, September 1981.
+
+ [30] Postel, J., "Simple Mail Transfer Protocol", RFC 821, August
+ 1982.
+
+ [31] Ramsdell, B., Ed., "S/MIME Version 3 Message Specification", RFC
+ 2633, June 1999.
+
+ [32] Resnick, P., Ed., "Internet Message Format", RFC 2822, April
+ 2001.
+
+ [33] Vaudreuil, G., "SMTP Service Extensions for Transmission of
+ Large and Binary MIME Messages", RFC 1830, August 1995.
+
+ [34] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC 1893,
+ January 1996.
+
+10. Editor's Address
+
+ John C. Klensin
+ AT&T Laboratories
+ 99 Bedford St
+ Boston, MA 02111 USA
+
+ Phone: 617-574-3076
+ EMail: klensin@research.att.com
+
+11. Acknowledgments
+
+ Many people worked long and hard on the many iterations of this
+ document. There was wide-ranging debate in the IETF DRUMS Working
+ Group, both on its mailing list and in face to face discussions,
+ about many technical issues and the role of a revised standard for
+ Internet mail transport, and many contributors helped form the
+ wording in this specification. The hundreds of participants in the
+ many discussions since RFC 821 was produced are too numerous to
+ mention, but they all helped this document become what it is.
+
+
+
+
+
+
+
+Klensin Standards Track [Page 70]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+APPENDICES
+
+A. TCP Transport Service
+
+ The TCP connection supports the transmission of 8-bit bytes. The
+ SMTP data is 7-bit ASCII characters. Each character is transmitted
+ as an 8-bit byte with the high-order bit cleared to zero. Service
+ extensions may modify this rule to permit transmission of full 8-bit
+ data bytes as part of the message body, but not in SMTP commands or
+ responses.
+
+B. Generating SMTP Commands from RFC 822 Headers
+
+ Some systems use RFC 822 headers (only) in a mail submission
+ protocol, or otherwise generate SMTP commands from RFC 822 headers
+ when such a message is handed to an MTA from a UA. While the MTA-UA
+ protocol is a private matter, not covered by any Internet Standard,
+ there are problems with this approach. For example, there have been
+ repeated problems with proper handling of "bcc" copies and
+ redistribution lists when information that conceptually belongs to a
+ mail envelopes is not separated early in processing from header
+ information (and kept separate).
+
+ It is recommended that the UA provide its initial ("submission
+ client") MTA with an envelope separate from the message itself.
+ However, if the envelope is not supplied, SMTP commands SHOULD be
+ generated as follows:
+
+ 1. Each recipient address from a TO, CC, or BCC header field SHOULD
+ be copied to a RCPT command (generating multiple message copies if
+ that is required for queuing or delivery). This includes any
+ addresses listed in a RFC 822 "group". Any BCC fields SHOULD then
+ be removed from the headers. Once this process is completed, the
+ remaining headers SHOULD be checked to verify that at least one
+ To:, Cc:, or Bcc: header remains. If none do, then a bcc: header
+ with no additional information SHOULD be inserted as specified in
+ [32].
+
+ 2. The return address in the MAIL command SHOULD, if possible, be
+ derived from the system's identity for the submitting (local)
+ user, and the "From:" header field otherwise. If there is a
+ system identity available, it SHOULD also be copied to the Sender
+ header field if it is different from the address in the From
+ header field. (Any Sender field that was already there SHOULD be
+ removed.) Systems may provide a way for submitters to override
+ the envelope return address, but may want to restrict its use to
+ privileged users. This will not prevent mail forgery, but may
+ lessen its incidence; see section 7.1.
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ When an MTA is being used in this way, it bears responsibility for
+ ensuring that the message being transmitted is valid. The mechanisms
+ for checking that validity, and for handling (or returning) messages
+ that are not valid at the time of arrival, are part of the MUA-MTA
+ interface and not covered by this specification.
+
+ A submission protocol based on Standard RFC 822 information alone
+ MUST NOT be used to gateway a message from a foreign (non-SMTP) mail
+ system into an SMTP environment. Additional information to construct
+ an envelope must come from some source in the other environment,
+ whether supplemental headers or the foreign system's envelope.
+
+ Attempts to gateway messages using only their header "to" and "cc"
+ fields have repeatedly caused mail loops and other behavior adverse
+ to the proper functioning of the Internet mail environment. These
+ problems have been especially common when the message originates from
+ an Internet mailing list and is distributed into the foreign
+ environment using envelope information. When these messages are then
+ processed by a header-only remailer, loops back to the Internet
+ environment (and the mailing list) are almost inevitable.
+
+C. Source Routes
+
+ Historically, the <reverse-path> was a reverse source routing list of
+ hosts and a source mailbox. The first host in the <reverse-path>
+ SHOULD be the host sending the MAIL command. Similarly, the
+ <forward-path> may be a source routing lists of hosts and a
+ destination mailbox. However, in general, the <forward-path> SHOULD
+ contain only a mailbox and domain name, relying on the domain name
+ system to supply routing information if required. The use of source
+ routes is deprecated; while servers MUST be prepared to receive and
+ handle them as discussed in section 3.3 and F.2, clients SHOULD NOT
+ transmit them and this section was included only to provide context.
+
+ For relay purposes, the forward-path may be a source route of the
+ form "@ONE,@TWO:JOE@THREE", where ONE, TWO, and THREE MUST BE fully-
+ qualified domain names. This form is used to emphasize the
+ distinction between an address and a route. The mailbox is an
+ absolute address, and the route is information about how to get
+ there. The two concepts should not be confused.
+
+ If source routes are used, RFC 821 and the text below should be
+ consulted for the mechanisms for constructing and updating the
+ forward- and reverse-paths.
+
+
+
+
+
+
+
+Klensin Standards Track [Page 72]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ The SMTP server transforms the command arguments by moving its own
+ identifier (its domain name or that of any domain for which it is
+ acting as a mail exchanger), if it appears, from the forward-path to
+ the beginning of the reverse-path.
+
+ Notice that the forward-path and reverse-path appear in the SMTP
+ commands and replies, but not necessarily in the message. That is,
+ there is no need for these paths and especially this syntax to appear
+ in the "To:" , "From:", "CC:", etc. fields of the message header.
+ Conversely, SMTP servers MUST NOT derive final message delivery
+ information from message header fields.
+
+ When the list of hosts is present, it is a "reverse" source route and
+ indicates that the mail was relayed through each host on the list
+ (the first host in the list was the most recent relay). This list is
+ used as a source route to return non-delivery notices to the sender.
+ As each relay host adds itself to the beginning of the list, it MUST
+ use its name as known in the transport environment to which it is
+ relaying the mail rather than that of the transport environment from
+ which the mail came (if they are different).
+
+D. Scenarios
+
+ This section presents complete scenarios of several types of SMTP
+ sessions. In the examples, "C:" indicates what is said by the SMTP
+ client, and "S:" indicates what is said by the SMTP server.
+
+D.1 A Typical SMTP Transaction Scenario
+
+ This SMTP example shows mail sent by Smith at host bar.com, to Jones,
+ Green, and Brown at host foo.com. Here we assume that host bar.com
+ contacts host foo.com directly. The mail is accepted for Jones and
+ Brown. Green does not have a mailbox at host foo.com.
+
+ S: 220 foo.com Simple Mail Transfer Service Ready
+ C: EHLO bar.com
+ S: 250-foo.com greets bar.com
+ S: 250-8BITMIME
+ S: 250-SIZE
+ S: 250-DSN
+ S: 250 HELP
+ C: MAIL FROM:<Smith@bar.com>
+ S: 250 OK
+ C: RCPT TO:<Jones@foo.com>
+ S: 250 OK
+ C: RCPT TO:<Green@foo.com>
+ S: 550 No such user here
+ C: RCPT TO:<Brown@foo.com>
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ S: 250 OK
+ C: DATA
+ S: 354 Start mail input; end with <CRLF>.<CRLF>
+ C: Blah blah blah...
+ C: ...etc. etc. etc.
+ C: .
+ S: 250 OK
+ C: QUIT
+ S: 221 foo.com Service closing transmission channel
+
+D.2 Aborted SMTP Transaction Scenario
+
+ S: 220 foo.com Simple Mail Transfer Service Ready
+ C: EHLO bar.com
+ S: 250-foo.com greets bar.com
+ S: 250-8BITMIME
+ S: 250-SIZE
+ S: 250-DSN
+ S: 250 HELP
+ C: MAIL FROM:<Smith@bar.com>
+ S: 250 OK
+ C: RCPT TO:<Jones@foo.com>
+ S: 250 OK
+ C: RCPT TO:<Green@foo.com>
+ S: 550 No such user here
+ C: RSET
+ S: 250 OK
+ C: QUIT
+ S: 221 foo.com Service closing transmission channel
+
+D.3 Relayed Mail Scenario
+
+ Step 1 -- Source Host to Relay Host
+
+ S: 220 foo.com Simple Mail Transfer Service Ready
+ C: EHLO bar.com
+ S: 250-foo.com greets bar.com
+ S: 250-8BITMIME
+ S: 250-SIZE
+ S: 250-DSN
+ S: 250 HELP
+ C: MAIL FROM:<JQP@bar.com>
+ S: 250 OK
+ C: RCPT TO:<@foo.com:Jones@XYZ.COM>
+ S: 250 OK
+ C: DATA
+ S: 354 Start mail input; end with <CRLF>.<CRLF>
+ C: Date: Thu, 21 May 1998 05:33:29 -0700
+
+
+
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+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ C: From: John Q. Public <JQP@bar.com>
+ C: Subject: The Next Meeting of the Board
+ C: To: Jones@xyz.com
+ C:
+ C: Bill:
+ C: The next meeting of the board of directors will be
+ C: on Tuesday.
+ C: John.
+ C: .
+ S: 250 OK
+ C: QUIT
+ S: 221 foo.com Service closing transmission channel
+
+ Step 2 -- Relay Host to Destination Host
+
+ S: 220 xyz.com Simple Mail Transfer Service Ready
+ C: EHLO foo.com
+ S: 250 xyz.com is on the air
+ C: MAIL FROM:<@foo.com:JQP@bar.com>
+ S: 250 OK
+ C: RCPT TO:<Jones@XYZ.COM>
+ S: 250 OK
+ C: DATA
+ S: 354 Start mail input; end with <CRLF>.<CRLF>
+ C: Received: from bar.com by foo.com ; Thu, 21 May 1998
+ C: 05:33:29 -0700
+ C: Date: Thu, 21 May 1998 05:33:22 -0700
+ C: From: John Q. Public <JQP@bar.com>
+ C: Subject: The Next Meeting of the Board
+ C: To: Jones@xyz.com
+ C:
+ C: Bill:
+ C: The next meeting of the board of directors will be
+ C: on Tuesday.
+ C: John.
+ C: .
+ S: 250 OK
+ C: QUIT
+ S: 221 foo.com Service closing transmission channel
+
+D.4 Verifying and Sending Scenario
+
+ S: 220 foo.com Simple Mail Transfer Service Ready
+ C: EHLO bar.com
+ S: 250-foo.com greets bar.com
+ S: 250-8BITMIME
+ S: 250-SIZE
+ S: 250-DSN
+
+
+
+Klensin Standards Track [Page 75]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+ S: 250-VRFY
+ S: 250 HELP
+ C: VRFY Crispin
+ S: 250 Mark Crispin <Admin.MRC@foo.com>
+ C: SEND FROM:<EAK@bar.com>
+ S: 250 OK
+ C: RCPT TO:<Admin.MRC@foo.com>
+ S: 250 OK
+ C: DATA
+ S: 354 Start mail input; end with <CRLF>.<CRLF>
+ C: Blah blah blah...
+ C: ...etc. etc. etc.
+ C: .
+ S: 250 OK
+ C: QUIT
+ S: 221 foo.com Service closing transmission channel
+
+E. Other Gateway Issues
+
+ In general, gateways between the Internet and other mail systems
+ SHOULD attempt to preserve any layering semantics across the
+ boundaries between the two mail systems involved. Gateway-
+ translation approaches that attempt to take shortcuts by mapping,
+ (such as envelope information from one system to the message headers
+ or body of another) have generally proven to be inadequate in
+ important ways. Systems translating between environments that do not
+ support both envelopes and headers and Internet mail must be written
+ with the understanding that some information loss is almost
+ inevitable.
+
+F. Deprecated Features of RFC 821
+
+ A few features of RFC 821 have proven to be problematic and SHOULD
+ NOT be used in Internet mail.
+
+F.1 TURN
+
+ This command, described in RFC 821, raises important security issues
+ since, in the absence of strong authentication of the host requesting
+ that the client and server switch roles, it can easily be used to
+ divert mail from its correct destination. Its use is deprecated;
+ SMTP systems SHOULD NOT use it unless the server can authenticate the
+ client.
+
+
+
+
+
+
+
+
+Klensin Standards Track [Page 76]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+F.2 Source Routing
+
+ RFC 821 utilized the concept of explicit source routing to get mail
+ from one host to another via a series of relays. The requirement to
+ utilize source routes in regular mail traffic was eliminated by the
+ introduction of the domain name system "MX" record and the last
+ significant justification for them was eliminated by the
+ introduction, in RFC 1123, of a clear requirement that addresses
+ following an "@" must all be fully-qualified domain names.
+ Consequently, the only remaining justifications for the use of source
+ routes are support for very old SMTP clients or MUAs and in mail
+ system debugging. They can, however, still be useful in the latter
+ circumstance and for routing mail around serious, but temporary,
+ problems such as problems with the relevant DNS records.
+
+ SMTP servers MUST continue to accept source route syntax as specified
+ in the main body of this document and in RFC 1123. They MAY, if
+ necessary, ignore the routes and utilize only the target domain in
+ the address. If they do utilize the source route, the message MUST
+ be sent to the first domain shown in the address. In particular, a
+ server MUST NOT guess at shortcuts within the source route.
+
+ Clients SHOULD NOT utilize explicit source routing except under
+ unusual circumstances, such as debugging or potentially relaying
+ around firewall or mail system configuration errors.
+
+F.3 HELO
+
+ As discussed in sections 3.1 and 4.1.1, EHLO is strongly preferred to
+ HELO when the server will accept the former. Servers must continue
+ to accept and process HELO in order to support older clients.
+
+F.4 #-literals
+
+ RFC 821 provided for specifying an Internet address as a decimal
+ integer host number prefixed by a pound sign, "#". In practice, that
+ form has been obsolete since the introduction of TCP/IP. It is
+ deprecated and MUST NOT be used.
+
+F.5 Dates and Years
+
+ When dates are inserted into messages by SMTP clients or servers
+ (e.g., in trace fields), four-digit years MUST BE used. Two-digit
+ years are deprecated; three-digit years were never permitted in the
+ Internet mail system.
+
+
+
+
+
+
+Klensin Standards Track [Page 77]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+F.6 Sending versus Mailing
+
+ In addition to specifying a mechanism for delivering messages to
+ user's mailboxes, RFC 821 provided additional, optional, commands to
+ deliver messages directly to the user's terminal screen. These
+ commands (SEND, SAML, SOML) were rarely implemented, and changes in
+ workstation technology and the introduction of other protocols may
+ have rendered them obsolete even where they are implemented.
+
+ Clients SHOULD NOT provide SEND, SAML, or SOML as services. Servers
+ MAY implement them. If they are implemented by servers, the
+ implementation model specified in RFC 821 MUST be used and the
+ command names MUST be published in the response to the EHLO command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Klensin Standards Track [Page 78]
+
+RFC 2821 Simple Mail Transfer Protocol April 2001
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Klensin Standards Track [Page 79]
+
diff --git a/rfc/rfc2822.txt b/rfc/rfc2822.txt
@@ -0,0 +1,2859 @@
+
+
+
+
+
+
+Network Working Group P. Resnick, Editor
+Request for Comments: 2822 QUALCOMM Incorporated
+Obsoletes: 822 April 2001
+Category: Standards Track
+
+
+ Internet Message Format
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+Abstract
+
+ This standard specifies a syntax for text messages that are sent
+ between computer users, within the framework of "electronic mail"
+ messages. This standard supersedes the one specified in Request For
+ Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
+ Messages", updating it to reflect current practice and incorporating
+ incremental changes that were specified in other RFCs.
+
+Table of Contents
+
+ 1. Introduction ............................................... 3
+ 1.1. Scope .................................................... 3
+ 1.2. Notational conventions ................................... 4
+ 1.2.1. Requirements notation .................................. 4
+ 1.2.2. Syntactic notation ..................................... 4
+ 1.3. Structure of this document ............................... 4
+ 2. Lexical Analysis of Messages ............................... 5
+ 2.1. General Description ...................................... 5
+ 2.1.1. Line Length Limits ..................................... 6
+ 2.2. Header Fields ............................................ 7
+ 2.2.1. Unstructured Header Field Bodies ....................... 7
+ 2.2.2. Structured Header Field Bodies ......................... 7
+ 2.2.3. Long Header Fields ..................................... 7
+ 2.3. Body ..................................................... 8
+ 3. Syntax ..................................................... 9
+ 3.1. Introduction ............................................. 9
+ 3.2. Lexical Tokens ........................................... 9
+
+
+
+Resnick Standards Track [Page 1]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ 3.2.1. Primitive Tokens ....................................... 9
+ 3.2.2. Quoted characters ......................................10
+ 3.2.3. Folding white space and comments .......................11
+ 3.2.4. Atom ...................................................12
+ 3.2.5. Quoted strings .........................................13
+ 3.2.6. Miscellaneous tokens ...................................13
+ 3.3. Date and Time Specification ..............................14
+ 3.4. Address Specification ....................................15
+ 3.4.1. Addr-spec specification ................................16
+ 3.5 Overall message syntax ....................................17
+ 3.6. Field definitions ........................................18
+ 3.6.1. The origination date field .............................20
+ 3.6.2. Originator fields ......................................21
+ 3.6.3. Destination address fields .............................22
+ 3.6.4. Identification fields ..................................23
+ 3.6.5. Informational fields ...................................26
+ 3.6.6. Resent fields ..........................................26
+ 3.6.7. Trace fields ...........................................28
+ 3.6.8. Optional fields ........................................29
+ 4. Obsolete Syntax ............................................29
+ 4.1. Miscellaneous obsolete tokens ............................30
+ 4.2. Obsolete folding white space .............................31
+ 4.3. Obsolete Date and Time ...................................31
+ 4.4. Obsolete Addressing ......................................33
+ 4.5. Obsolete header fields ...................................33
+ 4.5.1. Obsolete origination date field ........................34
+ 4.5.2. Obsolete originator fields .............................34
+ 4.5.3. Obsolete destination address fields ....................34
+ 4.5.4. Obsolete identification fields .........................35
+ 4.5.5. Obsolete informational fields ..........................35
+ 4.5.6. Obsolete resent fields .................................35
+ 4.5.7. Obsolete trace fields ..................................36
+ 4.5.8. Obsolete optional fields ...............................36
+ 5. Security Considerations ....................................36
+ 6. Bibliography ...............................................37
+ 7. Editor's Address ...........................................38
+ 8. Acknowledgements ...........................................39
+ Appendix A. Example messages ..................................41
+ A.1. Addressing examples ......................................41
+ A.1.1. A message from one person to another with simple
+ addressing .............................................41
+ A.1.2. Different types of mailboxes ...........................42
+ A.1.3. Group addresses ........................................43
+ A.2. Reply messages ...........................................43
+ A.3. Resent messages ..........................................44
+ A.4. Messages with trace fields ...............................46
+ A.5. White space, comments, and other oddities ................47
+ A.6. Obsoleted forms ..........................................47
+
+
+
+Resnick Standards Track [Page 2]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ A.6.1. Obsolete addressing ....................................48
+ A.6.2. Obsolete dates .........................................48
+ A.6.3. Obsolete white space and comments ......................48
+ Appendix B. Differences from earlier standards ................49
+ Appendix C. Notices ...........................................50
+ Full Copyright Statement ......................................51
+
+1. Introduction
+
+1.1. Scope
+
+ This standard specifies a syntax for text messages that are sent
+ between computer users, within the framework of "electronic mail"
+ messages. This standard supersedes the one specified in Request For
+ Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
+ Messages" [RFC822], updating it to reflect current practice and
+ incorporating incremental changes that were specified in other RFCs
+ [STD3].
+
+ This standard specifies a syntax only for text messages. In
+ particular, it makes no provision for the transmission of images,
+ audio, or other sorts of structured data in electronic mail messages.
+ There are several extensions published, such as the MIME document
+ series [RFC2045, RFC2046, RFC2049], which describe mechanisms for the
+ transmission of such data through electronic mail, either by
+ extending the syntax provided here or by structuring such messages to
+ conform to this syntax. Those mechanisms are outside of the scope of
+ this standard.
+
+ In the context of electronic mail, messages are viewed as having an
+ envelope and contents. The envelope contains whatever information is
+ needed to accomplish transmission and delivery. (See [RFC2821] for a
+ discussion of the envelope.) The contents comprise the object to be
+ delivered to the recipient. This standard applies only to the format
+ and some of the semantics of message contents. It contains no
+ specification of the information in the envelope.
+
+ However, some message systems may use information from the contents
+ to create the envelope. It is intended that this standard facilitate
+ the acquisition of such information by programs.
+
+ This specification is intended as a definition of what message
+ content format is to be passed between systems. Though some message
+ systems locally store messages in this format (which eliminates the
+ need for translation between formats) and others use formats that
+ differ from the one specified in this standard, local storage is
+ outside of the scope of this standard.
+
+
+
+
+Resnick Standards Track [Page 3]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Note: This standard is not intended to dictate the internal formats
+ used by sites, the specific message system features that they are
+ expected to support, or any of the characteristics of user interface
+ programs that create or read messages. In addition, this standard
+ does not specify an encoding of the characters for either transport
+ or storage; that is, it does not specify the number of bits used or
+ how those bits are specifically transferred over the wire or stored
+ on disk.
+
+1.2. Notational conventions
+
+1.2.1. Requirements notation
+
+ This document occasionally uses terms that appear in capital letters.
+ When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
+ NOT", and "MAY" appear capitalized, they are being used to indicate
+ particular requirements of this specification. A discussion of the
+ meanings of these terms appears in [RFC2119].
+
+1.2.2. Syntactic notation
+
+ This standard uses the Augmented Backus-Naur Form (ABNF) notation
+ specified in [RFC2234] for the formal definitions of the syntax of
+ messages. Characters will be specified either by a decimal value
+ (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
+ a case-insensitive literal value enclosed in quotation marks (e.g.,
+ "A" for either uppercase or lowercase A). See [RFC2234] for the full
+ description of the notation.
+
+1.3. Structure of this document
+
+ This document is divided into several sections.
+
+ This section, section 1, is a short introduction to the document.
+
+ Section 2 lays out the general description of a message and its
+ constituent parts. This is an overview to help the reader understand
+ some of the general principles used in the later portions of this
+ document. Any examples in this section MUST NOT be taken as
+ specification of the formal syntax of any part of a message.
+
+ Section 3 specifies formal ABNF rules for the structure of each part
+ of a message (the syntax) and describes the relationship between
+ those parts and their meaning in the context of a message (the
+ semantics). That is, it describes the actual rules for the structure
+ of each part of a message (the syntax) as well as a description of
+ the parts and instructions on how they ought to be interpreted (the
+ semantics). This includes analysis of the syntax and semantics of
+
+
+
+Resnick Standards Track [Page 4]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ subparts of messages that have specific structure. The syntax
+ included in section 3 represents messages as they MUST be created.
+ There are also notes in section 3 to indicate if any of the options
+ specified in the syntax SHOULD be used over any of the others.
+
+ Both sections 2 and 3 describe messages that are legal to generate
+ for purposes of this standard.
+
+ Section 4 of this document specifies an "obsolete" syntax. There are
+ references in section 3 to these obsolete syntactic elements. The
+ rules of the obsolete syntax are elements that have appeared in
+ earlier revisions of this standard or have previously been widely
+ used in Internet messages. As such, these elements MUST be
+ interpreted by parsers of messages in order to be conformant to this
+ standard. However, since items in this syntax have been determined
+ to be non-interoperable or to cause significant problems for
+ recipients of messages, they MUST NOT be generated by creators of
+ conformant messages.
+
+ Section 5 details security considerations to take into account when
+ implementing this standard.
+
+ Section 6 is a bibliography of references in this document.
+
+ Section 7 contains the editor's address.
+
+ Section 8 contains acknowledgements.
+
+ Appendix A lists examples of different sorts of messages. These
+ examples are not exhaustive of the types of messages that appear on
+ the Internet, but give a broad overview of certain syntactic forms.
+
+ Appendix B lists the differences between this standard and earlier
+ standards for Internet messages.
+
+ Appendix C has copyright and intellectual property notices.
+
+2. Lexical Analysis of Messages
+
+2.1. General Description
+
+ At the most basic level, a message is a series of characters. A
+ message that is conformant with this standard is comprised of
+ characters with values in the range 1 through 127 and interpreted as
+ US-ASCII characters [ASCII]. For brevity, this document sometimes
+ refers to this range of characters as simply "US-ASCII characters".
+
+
+
+
+
+Resnick Standards Track [Page 5]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Note: This standard specifies that messages are made up of characters
+ in the US-ASCII range of 1 through 127. There are other documents,
+ specifically the MIME document series [RFC2045, RFC2046, RFC2047,
+ RFC2048, RFC2049], that extend this standard to allow for values
+ outside of that range. Discussion of those mechanisms is not within
+ the scope of this standard.
+
+ Messages are divided into lines of characters. A line is a series of
+ characters that is delimited with the two characters carriage-return
+ and line-feed; that is, the carriage return (CR) character (ASCII
+ value 13) followed immediately by the line feed (LF) character (ASCII
+ value 10). (The carriage-return/line-feed pair is usually written in
+ this document as "CRLF".)
+
+ A message consists of header fields (collectively called "the header
+ of the message") followed, optionally, by a body. The header is a
+ sequence of lines of characters with special syntax as defined in
+ this standard. The body is simply a sequence of characters that
+ follows the header and is separated from the header by an empty line
+ (i.e., a line with nothing preceding the CRLF).
+
+2.1.1. Line Length Limits
+
+ There are two limits that this standard places on the number of
+ characters in a line. Each line of characters MUST be no more than
+ 998 characters, and SHOULD be no more than 78 characters, excluding
+ the CRLF.
+
+ The 998 character limit is due to limitations in many implementations
+ which send, receive, or store Internet Message Format messages that
+ simply cannot handle more than 998 characters on a line. Receiving
+ implementations would do well to handle an arbitrarily large number
+ of characters in a line for robustness sake. However, there are so
+ many implementations which (in compliance with the transport
+ requirements of [RFC2821]) do not accept messages containing more
+ than 1000 character including the CR and LF per line, it is important
+ for implementations not to create such messages.
+
+ The more conservative 78 character recommendation is to accommodate
+ the many implementations of user interfaces that display these
+ messages which may truncate, or disastrously wrap, the display of
+ more than 78 characters per line, in spite of the fact that such
+ implementations are non-conformant to the intent of this
+ specification (and that of [RFC2821] if they actually cause
+ information to be lost). Again, even though this limitation is put on
+ messages, it is encumbant upon implementations which display messages
+
+
+
+
+
+Resnick Standards Track [Page 6]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ to handle an arbitrarily large number of characters in a line
+ (certainly at least up to the 998 character limit) for the sake of
+ robustness.
+
+2.2. Header Fields
+
+ Header fields are lines composed of a field name, followed by a colon
+ (":"), followed by a field body, and terminated by CRLF. A field
+ name MUST be composed of printable US-ASCII characters (i.e.,
+ characters that have values between 33 and 126, inclusive), except
+ colon. A field body may be composed of any US-ASCII characters,
+ except for CR and LF. However, a field body may contain CRLF when
+ used in header "folding" and "unfolding" as described in section
+ 2.2.3. All field bodies MUST conform to the syntax described in
+ sections 3 and 4 of this standard.
+
+2.2.1. Unstructured Header Field Bodies
+
+ Some field bodies in this standard are defined simply as
+ "unstructured" (which is specified below as any US-ASCII characters,
+ except for CR and LF) with no further restrictions. These are
+ referred to as unstructured field bodies. Semantically, unstructured
+ field bodies are simply to be treated as a single line of characters
+ with no further processing (except for header "folding" and
+ "unfolding" as described in section 2.2.3).
+
+2.2.2. Structured Header Field Bodies
+
+ Some field bodies in this standard have specific syntactical
+ structure more restrictive than the unstructured field bodies
+ described above. These are referred to as "structured" field bodies.
+ Structured field bodies are sequences of specific lexical tokens as
+ described in sections 3 and 4 of this standard. Many of these tokens
+ are allowed (according to their syntax) to be introduced or end with
+ comments (as described in section 3.2.3) as well as the space (SP,
+ ASCII value 32) and horizontal tab (HTAB, ASCII value 9) characters
+ (together known as the white space characters, WSP), and those WSP
+ characters are subject to header "folding" and "unfolding" as
+ described in section 2.2.3. Semantic analysis of structured field
+ bodies is given along with their syntax.
+
+2.2.3. Long Header Fields
+
+ Each header field is logically a single line of characters comprising
+ the field name, the colon, and the field body. For convenience
+ however, and to deal with the 998/78 character limitations per line,
+ the field body portion of a header field can be split into a multiple
+ line representation; this is called "folding". The general rule is
+
+
+
+Resnick Standards Track [Page 7]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ that wherever this standard allows for folding white space (not
+ simply WSP characters), a CRLF may be inserted before any WSP. For
+ example, the header field:
+
+ Subject: This is a test
+
+ can be represented as:
+
+ Subject: This
+ is a test
+
+ Note: Though structured field bodies are defined in such a way that
+ folding can take place between many of the lexical tokens (and even
+ within some of the lexical tokens), folding SHOULD be limited to
+ placing the CRLF at higher-level syntactic breaks. For instance, if
+ a field body is defined as comma-separated values, it is recommended
+ that folding occur after the comma separating the structured items in
+ preference to other places where the field could be folded, even if
+ it is allowed elsewhere.
+
+ The process of moving from this folded multiple-line representation
+ of a header field to its single line representation is called
+ "unfolding". Unfolding is accomplished by simply removing any CRLF
+ that is immediately followed by WSP. Each header field should be
+ treated in its unfolded form for further syntactic and semantic
+ evaluation.
+
+2.3. Body
+
+ The body of a message is simply lines of US-ASCII characters. The
+ only two limitations on the body are as follows:
+
+ - CR and LF MUST only occur together as CRLF; they MUST NOT appear
+ independently in the body.
+
+ - Lines of characters in the body MUST be limited to 998 characters,
+ and SHOULD be limited to 78 characters, excluding the CRLF.
+
+ Note: As was stated earlier, there are other standards documents,
+ specifically the MIME documents [RFC2045, RFC2046, RFC2048, RFC2049]
+ that extend this standard to allow for different sorts of message
+ bodies. Again, these mechanisms are beyond the scope of this
+ document.
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 8]
+
+RFC 2822 Internet Message Format April 2001
+
+
+3. Syntax
+
+3.1. Introduction
+
+ The syntax as given in this section defines the legal syntax of
+ Internet messages. Messages that are conformant to this standard
+ MUST conform to the syntax in this section. If there are options in
+ this section where one option SHOULD be generated, that is indicated
+ either in the prose or in a comment next to the syntax.
+
+ For the defined expressions, a short description of the syntax and
+ use is given, followed by the syntax in ABNF, followed by a semantic
+ analysis. Primitive tokens that are used but otherwise unspecified
+ come from [RFC2234].
+
+ In some of the definitions, there will be nonterminals whose names
+ start with "obs-". These "obs-" elements refer to tokens defined in
+ the obsolete syntax in section 4. In all cases, these productions
+ are to be ignored for the purposes of generating legal Internet
+ messages and MUST NOT be used as part of such a message. However,
+ when interpreting messages, these tokens MUST be honored as part of
+ the legal syntax. In this sense, section 3 defines a grammar for
+ generation of messages, with "obs-" elements that are to be ignored,
+ while section 4 adds grammar for interpretation of messages.
+
+3.2. Lexical Tokens
+
+ The following rules are used to define an underlying lexical
+ analyzer, which feeds tokens to the higher-level parsers. This
+ section defines the tokens used in structured header field bodies.
+
+ Note: Readers of this standard need to pay special attention to how
+ these lexical tokens are used in both the lower-level and
+ higher-level syntax later in the document. Particularly, the white
+ space tokens and the comment tokens defined in section 3.2.3 get used
+ in the lower-level tokens defined here, and those lower-level tokens
+ are in turn used as parts of the higher-level tokens defined later.
+ Therefore, the white space and comments may be allowed in the
+ higher-level tokens even though they may not explicitly appear in a
+ particular definition.
+
+3.2.1. Primitive Tokens
+
+ The following are primitive tokens referred to elsewhere in this
+ standard, but not otherwise defined in [RFC2234]. Some of them will
+ not appear anywhere else in the syntax, but they are convenient to
+ refer to in other parts of this document.
+
+
+
+
+Resnick Standards Track [Page 9]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Note: The "specials" below are just such an example. Though the
+ specials token does not appear anywhere else in this standard, it is
+ useful for implementers who use tools that lexically analyze
+ messages. Each of the characters in specials can be used to indicate
+ a tokenization point in lexical analysis.
+
+NO-WS-CTL = %d1-8 / ; US-ASCII control characters
+ %d11 / ; that do not include the
+ %d12 / ; carriage return, line feed,
+ %d14-31 / ; and white space characters
+ %d127
+
+text = %d1-9 / ; Characters excluding CR and LF
+ %d11 /
+ %d12 /
+ %d14-127 /
+ obs-text
+
+specials = "(" / ")" / ; Special characters used in
+ "<" / ">" / ; other parts of the syntax
+ "[" / "]" /
+ ":" / ";" /
+ "@" / "\" /
+ "," / "." /
+ DQUOTE
+
+ No special semantics are attached to these tokens. They are simply
+ single characters.
+
+3.2.2. Quoted characters
+
+ Some characters are reserved for special interpretation, such as
+ delimiting lexical tokens. To permit use of these characters as
+ uninterpreted data, a quoting mechanism is provided.
+
+quoted-pair = ("\" text) / obs-qp
+
+ Where any quoted-pair appears, it is to be interpreted as the text
+ character alone. That is to say, the "\" character that appears as
+ part of a quoted-pair is semantically "invisible".
+
+ Note: The "\" character may appear in a message where it is not part
+ of a quoted-pair. A "\" character that does not appear in a
+ quoted-pair is not semantically invisible. The only places in this
+ standard where quoted-pair currently appears are ccontent, qcontent,
+ dcontent, no-fold-quote, and no-fold-literal.
+
+
+
+
+
+Resnick Standards Track [Page 10]
+
+RFC 2822 Internet Message Format April 2001
+
+
+3.2.3. Folding white space and comments
+
+ White space characters, including white space used in folding
+ (described in section 2.2.3), may appear between many elements in
+ header field bodies. Also, strings of characters that are treated as
+ comments may be included in structured field bodies as characters
+ enclosed in parentheses. The following defines the folding white
+ space (FWS) and comment constructs.
+
+ Strings of characters enclosed in parentheses are considered comments
+ so long as they do not appear within a "quoted-string", as defined in
+ section 3.2.5. Comments may nest.
+
+ There are several places in this standard where comments and FWS may
+ be freely inserted. To accommodate that syntax, an additional token
+ for "CFWS" is defined for places where comments and/or FWS can occur.
+ However, where CFWS occurs in this standard, it MUST NOT be inserted
+ in such a way that any line of a folded header field is made up
+ entirely of WSP characters and nothing else.
+
+FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
+ obs-FWS
+
+ctext = NO-WS-CTL / ; Non white space controls
+
+ %d33-39 / ; The rest of the US-ASCII
+ %d42-91 / ; characters not including "(",
+ %d93-126 ; ")", or "\"
+
+ccontent = ctext / quoted-pair / comment
+
+comment = "(" *([FWS] ccontent) [FWS] ")"
+
+CFWS = *([FWS] comment) (([FWS] comment) / FWS)
+
+ Throughout this standard, where FWS (the folding white space token)
+ appears, it indicates a place where header folding, as discussed in
+ section 2.2.3, may take place. Wherever header folding appears in a
+ message (that is, a header field body containing a CRLF followed by
+ any WSP), header unfolding (removal of the CRLF) is performed before
+ any further lexical analysis is performed on that header field
+ according to this standard. That is to say, any CRLF that appears in
+ FWS is semantically "invisible."
+
+ A comment is normally used in a structured field body to provide some
+ human readable informational text. Since a comment is allowed to
+ contain FWS, folding is permitted within the comment. Also note that
+ since quoted-pair is allowed in a comment, the parentheses and
+
+
+
+Resnick Standards Track [Page 11]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ backslash characters may appear in a comment so long as they appear
+ as a quoted-pair. Semantically, the enclosing parentheses are not
+ part of the comment; the comment is what is contained between the two
+ parentheses. As stated earlier, the "\" in any quoted-pair and the
+ CRLF in any FWS that appears within the comment are semantically
+ "invisible" and therefore not part of the comment either.
+
+ Runs of FWS, comment or CFWS that occur between lexical tokens in a
+ structured field header are semantically interpreted as a single
+ space character.
+
+3.2.4. Atom
+
+ Several productions in structured header field bodies are simply
+ strings of certain basic characters. Such productions are called
+ atoms.
+
+ Some of the structured header field bodies also allow the period
+ character (".", ASCII value 46) within runs of atext. An additional
+ "dot-atom" token is defined for those purposes.
+
+atext = ALPHA / DIGIT / ; Any character except controls,
+ "!" / "#" / ; SP, and specials.
+ "$" / "%" / ; Used for atoms
+ "&" / "'" /
+ "*" / "+" /
+ "-" / "/" /
+ "=" / "?" /
+ "^" / "_" /
+ "`" / "{" /
+ "|" / "}" /
+ "~"
+
+atom = [CFWS] 1*atext [CFWS]
+
+dot-atom = [CFWS] dot-atom-text [CFWS]
+
+dot-atom-text = 1*atext *("." 1*atext)
+
+ Both atom and dot-atom are interpreted as a single unit, comprised of
+ the string of characters that make it up. Semantically, the optional
+ comments and FWS surrounding the rest of the characters are not part
+ of the atom; the atom is only the run of atext characters in an atom,
+ or the atext and "." characters in a dot-atom.
+
+
+
+
+
+
+
+Resnick Standards Track [Page 12]
+
+RFC 2822 Internet Message Format April 2001
+
+
+3.2.5. Quoted strings
+
+ Strings of characters that include characters other than those
+ allowed in atoms may be represented in a quoted string format, where
+ the characters are surrounded by quote (DQUOTE, ASCII value 34)
+ characters.
+
+qtext = NO-WS-CTL / ; Non white space controls
+
+ %d33 / ; The rest of the US-ASCII
+ %d35-91 / ; characters not including "\"
+ %d93-126 ; or the quote character
+
+qcontent = qtext / quoted-pair
+
+quoted-string = [CFWS]
+ DQUOTE *([FWS] qcontent) [FWS] DQUOTE
+ [CFWS]
+
+ A quoted-string is treated as a unit. That is, quoted-string is
+ identical to atom, semantically. Since a quoted-string is allowed to
+ contain FWS, folding is permitted. Also note that since quoted-pair
+ is allowed in a quoted-string, the quote and backslash characters may
+ appear in a quoted-string so long as they appear as a quoted-pair.
+
+ Semantically, neither the optional CFWS outside of the quote
+ characters nor the quote characters themselves are part of the
+ quoted-string; the quoted-string is what is contained between the two
+ quote characters. As stated earlier, the "\" in any quoted-pair and
+ the CRLF in any FWS/CFWS that appears within the quoted-string are
+ semantically "invisible" and therefore not part of the quoted-string
+ either.
+
+3.2.6. Miscellaneous tokens
+
+ Three additional tokens are defined, word and phrase for combinations
+ of atoms and/or quoted-strings, and unstructured for use in
+ unstructured header fields and in some places within structured
+ header fields.
+
+word = atom / quoted-string
+
+phrase = 1*word / obs-phrase
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 13]
+
+RFC 2822 Internet Message Format April 2001
+
+
+utext = NO-WS-CTL / ; Non white space controls
+ %d33-126 / ; The rest of US-ASCII
+ obs-utext
+
+unstructured = *([FWS] utext) [FWS]
+
+3.3. Date and Time Specification
+
+ Date and time occur in several header fields. This section specifies
+ the syntax for a full date and time specification. Though folding
+ white space is permitted throughout the date-time specification, it
+ is RECOMMENDED that a single space be used in each place that FWS
+ appears (whether it is required or optional); some older
+ implementations may not interpret other occurrences of folding white
+ space correctly.
+
+date-time = [ day-of-week "," ] date FWS time [CFWS]
+
+day-of-week = ([FWS] day-name) / obs-day-of-week
+
+day-name = "Mon" / "Tue" / "Wed" / "Thu" /
+ "Fri" / "Sat" / "Sun"
+
+date = day month year
+
+year = 4*DIGIT / obs-year
+
+month = (FWS month-name FWS) / obs-month
+
+month-name = "Jan" / "Feb" / "Mar" / "Apr" /
+ "May" / "Jun" / "Jul" / "Aug" /
+ "Sep" / "Oct" / "Nov" / "Dec"
+
+day = ([FWS] 1*2DIGIT) / obs-day
+
+time = time-of-day FWS zone
+
+time-of-day = hour ":" minute [ ":" second ]
+
+hour = 2DIGIT / obs-hour
+
+minute = 2DIGIT / obs-minute
+
+second = 2DIGIT / obs-second
+
+zone = (( "+" / "-" ) 4DIGIT) / obs-zone
+
+
+
+
+
+Resnick Standards Track [Page 14]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ The day is the numeric day of the month. The year is any numeric
+ year 1900 or later.
+
+ The time-of-day specifies the number of hours, minutes, and
+ optionally seconds since midnight of the date indicated.
+
+ The date and time-of-day SHOULD express local time.
+
+ The zone specifies the offset from Coordinated Universal Time (UTC,
+ formerly referred to as "Greenwich Mean Time") that the date and
+ time-of-day represent. The "+" or "-" indicates whether the
+ time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
+ Universal Time. The first two digits indicate the number of hours
+ difference from Universal Time, and the last two digits indicate the
+ number of minutes difference from Universal Time. (Hence, +hhmm
+ means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
+ minutes). The form "+0000" SHOULD be used to indicate a time zone at
+ Universal Time. Though "-0000" also indicates Universal Time, it is
+ used to indicate that the time was generated on a system that may be
+ in a local time zone other than Universal Time and therefore
+ indicates that the date-time contains no information about the local
+ time zone.
+
+ A date-time specification MUST be semantically valid. That is, the
+ day-of-the-week (if included) MUST be the day implied by the date,
+ the numeric day-of-month MUST be between 1 and the number of days
+ allowed for the specified month (in the specified year), the
+ time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
+ number of seconds allowing for a leap second; see [STD12]), and the
+ zone MUST be within the range -9959 through +9959.
+
+3.4. Address Specification
+
+ Addresses occur in several message header fields to indicate senders
+ and recipients of messages. An address may either be an individual
+ mailbox, or a group of mailboxes.
+
+address = mailbox / group
+
+mailbox = name-addr / addr-spec
+
+name-addr = [display-name] angle-addr
+
+angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
+
+group = display-name ":" [mailbox-list / CFWS] ";"
+ [CFWS]
+
+
+
+
+Resnick Standards Track [Page 15]
+
+RFC 2822 Internet Message Format April 2001
+
+
+display-name = phrase
+
+mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
+
+address-list = (address *("," address)) / obs-addr-list
+
+ A mailbox receives mail. It is a conceptual entity which does not
+ necessarily pertain to file storage. For example, some sites may
+ choose to print mail on a printer and deliver the output to the
+ addressee's desk. Normally, a mailbox is comprised of two parts: (1)
+ an optional display name that indicates the name of the recipient
+ (which could be a person or a system) that could be displayed to the
+ user of a mail application, and (2) an addr-spec address enclosed in
+ angle brackets ("<" and ">"). There is also an alternate simple form
+ of a mailbox where the addr-spec address appears alone, without the
+ recipient's name or the angle brackets. The Internet addr-spec
+ address is described in section 3.4.1.
+
+ Note: Some legacy implementations used the simple form where the
+ addr-spec appears without the angle brackets, but included the name
+ of the recipient in parentheses as a comment following the addr-spec.
+ Since the meaning of the information in a comment is unspecified,
+ implementations SHOULD use the full name-addr form of the mailbox,
+ instead of the legacy form, to specify the display name associated
+ with a mailbox. Also, because some legacy implementations interpret
+ the comment, comments generally SHOULD NOT be used in address fields
+ to avoid confusing such implementations.
+
+ When it is desirable to treat several mailboxes as a single unit
+ (i.e., in a distribution list), the group construct can be used. The
+ group construct allows the sender to indicate a named group of
+ recipients. This is done by giving a display name for the group,
+ followed by a colon, followed by a comma separated list of any number
+ of mailboxes (including zero and one), and ending with a semicolon.
+ Because the list of mailboxes can be empty, using the group construct
+ is also a simple way to communicate to recipients that the message
+ was sent to one or more named sets of recipients, without actually
+ providing the individual mailbox address for each of those
+ recipients.
+
+3.4.1. Addr-spec specification
+
+ An addr-spec is a specific Internet identifier that contains a
+ locally interpreted string followed by the at-sign character ("@",
+ ASCII value 64) followed by an Internet domain. The locally
+ interpreted string is either a quoted-string or a dot-atom. If the
+ string can be represented as a dot-atom (that is, it contains no
+ characters other than atext characters or "." surrounded by atext
+
+
+
+Resnick Standards Track [Page 16]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ characters), then the dot-atom form SHOULD be used and the
+ quoted-string form SHOULD NOT be used. Comments and folding white
+ space SHOULD NOT be used around the "@" in the addr-spec.
+
+addr-spec = local-part "@" domain
+
+local-part = dot-atom / quoted-string / obs-local-part
+
+domain = dot-atom / domain-literal / obs-domain
+
+domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
+
+dcontent = dtext / quoted-pair
+
+dtext = NO-WS-CTL / ; Non white space controls
+
+ %d33-90 / ; The rest of the US-ASCII
+ %d94-126 ; characters not including "[",
+ ; "]", or "\"
+
+ The domain portion identifies the point to which the mail is
+ delivered. In the dot-atom form, this is interpreted as an Internet
+ domain name (either a host name or a mail exchanger name) as
+ described in [STD3, STD13, STD14]. In the domain-literal form, the
+ domain is interpreted as the literal Internet address of the
+ particular host. In both cases, how addressing is used and how
+ messages are transported to a particular host is covered in the mail
+ transport document [RFC2821]. These mechanisms are outside of the
+ scope of this document.
+
+ The local-part portion is a domain dependent string. In addresses,
+ it is simply interpreted on the particular host as a name of a
+ particular mailbox.
+
+3.5 Overall message syntax
+
+ A message consists of header fields, optionally followed by a message
+ body. Lines in a message MUST be a maximum of 998 characters
+ excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
+ characters excluding the CRLF. (See section 2.1.1 for explanation.)
+ In a message body, though all of the characters listed in the text
+ rule MAY be used, the use of US-ASCII control characters (values 1
+ through 8, 11, 12, and 14 through 31) is discouraged since their
+ interpretation by receivers for display is not guaranteed.
+
+
+
+
+
+
+
+Resnick Standards Track [Page 17]
+
+RFC 2822 Internet Message Format April 2001
+
+
+message = (fields / obs-fields)
+ [CRLF body]
+
+body = *(*998text CRLF) *998text
+
+ The header fields carry most of the semantic information and are
+ defined in section 3.6. The body is simply a series of lines of text
+ which are uninterpreted for the purposes of this standard.
+
+3.6. Field definitions
+
+ The header fields of a message are defined here. All header fields
+ have the same general syntactic structure: A field name, followed by
+ a colon, followed by the field body. The specific syntax for each
+ header field is defined in the subsequent sections.
+
+ Note: In the ABNF syntax for each field in subsequent sections, each
+ field name is followed by the required colon. However, for brevity
+ sometimes the colon is not referred to in the textual description of
+ the syntax. It is, nonetheless, required.
+
+ It is important to note that the header fields are not guaranteed to
+ be in a particular order. They may appear in any order, and they
+ have been known to be reordered occasionally when transported over
+ the Internet. However, for the purposes of this standard, header
+ fields SHOULD NOT be reordered when a message is transported or
+ transformed. More importantly, the trace header fields and resent
+ header fields MUST NOT be reordered, and SHOULD be kept in blocks
+ prepended to the message. See sections 3.6.6 and 3.6.7 for more
+ information.
+
+ The only required header fields are the origination date field and
+ the originator address field(s). All other header fields are
+ syntactically optional. More information is contained in the table
+ following this definition.
+
+fields = *(trace
+ *(resent-date /
+ resent-from /
+ resent-sender /
+ resent-to /
+ resent-cc /
+ resent-bcc /
+ resent-msg-id))
+ *(orig-date /
+ from /
+ sender /
+ reply-to /
+
+
+
+Resnick Standards Track [Page 18]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ to /
+ cc /
+ bcc /
+ message-id /
+ in-reply-to /
+ references /
+ subject /
+ comments /
+ keywords /
+ optional-field)
+
+ The following table indicates limits on the number of times each
+ field may occur in a message header as well as any special
+ limitations on the use of those fields. An asterisk next to a value
+ in the minimum or maximum column indicates that a special restriction
+ appears in the Notes column.
+
+Field Min number Max number Notes
+
+trace 0 unlimited Block prepended - see
+ 3.6.7
+
+resent-date 0* unlimited* One per block, required
+ if other resent fields
+ present - see 3.6.6
+
+resent-from 0 unlimited* One per block - see
+ 3.6.6
+
+resent-sender 0* unlimited* One per block, MUST
+ occur with multi-address
+ resent-from - see 3.6.6
+
+resent-to 0 unlimited* One per block - see
+ 3.6.6
+
+resent-cc 0 unlimited* One per block - see
+ 3.6.6
+
+resent-bcc 0 unlimited* One per block - see
+ 3.6.6
+
+resent-msg-id 0 unlimited* One per block - see
+ 3.6.6
+
+orig-date 1 1
+
+from 1 1 See sender and 3.6.2
+
+
+
+Resnick Standards Track [Page 19]
+
+RFC 2822 Internet Message Format April 2001
+
+
+sender 0* 1 MUST occur with multi-
+ address from - see 3.6.2
+
+reply-to 0 1
+
+to 0 1
+
+cc 0 1
+
+bcc 0 1
+
+message-id 0* 1 SHOULD be present - see
+ 3.6.4
+
+in-reply-to 0* 1 SHOULD occur in some
+ replies - see 3.6.4
+
+references 0* 1 SHOULD occur in some
+ replies - see 3.6.4
+
+subject 0 1
+
+comments 0 unlimited
+
+keywords 0 unlimited
+
+optional-field 0 unlimited
+
+ The exact interpretation of each field is described in subsequent
+ sections.
+
+3.6.1. The origination date field
+
+ The origination date field consists of the field name "Date" followed
+ by a date-time specification.
+
+orig-date = "Date:" date-time CRLF
+
+ The origination date specifies the date and time at which the creator
+ of the message indicated that the message was complete and ready to
+ enter the mail delivery system. For instance, this might be the time
+ that a user pushes the "send" or "submit" button in an application
+ program. In any case, it is specifically not intended to convey the
+ time that the message is actually transported, but rather the time at
+ which the human or other creator of the message has put the message
+ into its final form, ready for transport. (For example, a portable
+ computer user who is not connected to a network might queue a message
+
+
+
+
+Resnick Standards Track [Page 20]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ for delivery. The origination date is intended to contain the date
+ and time that the user queued the message, not the time when the user
+ connected to the network to send the message.)
+
+3.6.2. Originator fields
+
+ The originator fields of a message consist of the from field, the
+ sender field (when applicable), and optionally the reply-to field.
+ The from field consists of the field name "From" and a
+ comma-separated list of one or more mailbox specifications. If the
+ from field contains more than one mailbox specification in the
+ mailbox-list, then the sender field, containing the field name
+ "Sender" and a single mailbox specification, MUST appear in the
+ message. In either case, an optional reply-to field MAY also be
+ included, which contains the field name "Reply-To" and a
+ comma-separated list of one or more addresses.
+
+from = "From:" mailbox-list CRLF
+
+sender = "Sender:" mailbox CRLF
+
+reply-to = "Reply-To:" address-list CRLF
+
+ The originator fields indicate the mailbox(es) of the source of the
+ message. The "From:" field specifies the author(s) of the message,
+ that is, the mailbox(es) of the person(s) or system(s) responsible
+ for the writing of the message. The "Sender:" field specifies the
+ mailbox of the agent responsible for the actual transmission of the
+ message. For example, if a secretary were to send a message for
+ another person, the mailbox of the secretary would appear in the
+ "Sender:" field and the mailbox of the actual author would appear in
+ the "From:" field. If the originator of the message can be indicated
+ by a single mailbox and the author and transmitter are identical, the
+ "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
+ appear.
+
+ The originator fields also provide the information required when
+ replying to a message. When the "Reply-To:" field is present, it
+ indicates the mailbox(es) to which the author of the message suggests
+ that replies be sent. In the absence of the "Reply-To:" field,
+ replies SHOULD by default be sent to the mailbox(es) specified in the
+ "From:" field unless otherwise specified by the person composing the
+ reply.
+
+ In all cases, the "From:" field SHOULD NOT contain any mailbox that
+ does not belong to the author(s) of the message. See also section
+ 3.6.3 for more information on forming the destination addresses for a
+ reply.
+
+
+
+Resnick Standards Track [Page 21]
+
+RFC 2822 Internet Message Format April 2001
+
+
+3.6.3. Destination address fields
+
+ The destination fields of a message consist of three possible fields,
+ each of the same form: The field name, which is either "To", "Cc", or
+ "Bcc", followed by a comma-separated list of one or more addresses
+ (either mailbox or group syntax).
+
+to = "To:" address-list CRLF
+
+cc = "Cc:" address-list CRLF
+
+bcc = "Bcc:" (address-list / [CFWS]) CRLF
+
+ The destination fields specify the recipients of the message. Each
+ destination field may have one or more addresses, and each of the
+ addresses indicate the intended recipients of the message. The only
+ difference between the three fields is how each is used.
+
+ The "To:" field contains the address(es) of the primary recipient(s)
+ of the message.
+
+ The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
+ making a copy on a typewriter using carbon paper) contains the
+ addresses of others who are to receive the message, though the
+ content of the message may not be directed at them.
+
+ The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
+ addresses of recipients of the message whose addresses are not to be
+ revealed to other recipients of the message. There are three ways in
+ which the "Bcc:" field is used. In the first case, when a message
+ containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
+ removed even though all of the recipients (including those specified
+ in the "Bcc:" field) are sent a copy of the message. In the second
+ case, recipients specified in the "To:" and "Cc:" lines each are sent
+ a copy of the message with the "Bcc:" line removed as above, but the
+ recipients on the "Bcc:" line get a separate copy of the message
+ containing a "Bcc:" line. (When there are multiple recipient
+ addresses in the "Bcc:" field, some implementations actually send a
+ separate copy of the message to each recipient with a "Bcc:"
+ containing only the address of that particular recipient.) Finally,
+ since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
+ sent without any addresses indicating to the recipients that blind
+ copies were sent to someone. Which method to use with "Bcc:" fields
+ is implementation dependent, but refer to the "Security
+ Considerations" section of this document for a discussion of each.
+
+
+
+
+
+
+Resnick Standards Track [Page 22]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ When a message is a reply to another message, the mailboxes of the
+ authors of the original message (the mailboxes in the "From:" field)
+ or mailboxes specified in the "Reply-To:" field (if it exists) MAY
+ appear in the "To:" field of the reply since these would normally be
+ the primary recipients of the reply. If a reply is sent to a message
+ that has destination fields, it is often desirable to send a copy of
+ the reply to all of the recipients of the message, in addition to the
+ author. When such a reply is formed, addresses in the "To:" and
+ "Cc:" fields of the original message MAY appear in the "Cc:" field of
+ the reply, since these are normally secondary recipients of the
+ reply. If a "Bcc:" field is present in the original message,
+ addresses in that field MAY appear in the "Bcc:" field of the reply,
+ but SHOULD NOT appear in the "To:" or "Cc:" fields.
+
+ Note: Some mail applications have automatic reply commands that
+ include the destination addresses of the original message in the
+ destination addresses of the reply. How those reply commands behave
+ is implementation dependent and is beyond the scope of this document.
+ In particular, whether or not to include the original destination
+ addresses when the original message had a "Reply-To:" field is not
+ addressed here.
+
+3.6.4. Identification fields
+
+ Though optional, every message SHOULD have a "Message-ID:" field.
+ Furthermore, reply messages SHOULD have "In-Reply-To:" and
+ "References:" fields as appropriate, as described below.
+
+ The "Message-ID:" field contains a single unique message identifier.
+ The "References:" and "In-Reply-To:" field each contain one or more
+ unique message identifiers, optionally separated by CFWS.
+
+ The message identifier (msg-id) is similar in syntax to an angle-addr
+ construct without the internal CFWS.
+
+message-id = "Message-ID:" msg-id CRLF
+
+in-reply-to = "In-Reply-To:" 1*msg-id CRLF
+
+references = "References:" 1*msg-id CRLF
+
+msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
+
+id-left = dot-atom-text / no-fold-quote / obs-id-left
+
+id-right = dot-atom-text / no-fold-literal / obs-id-right
+
+no-fold-quote = DQUOTE *(qtext / quoted-pair) DQUOTE
+
+
+
+Resnick Standards Track [Page 23]
+
+RFC 2822 Internet Message Format April 2001
+
+
+no-fold-literal = "[" *(dtext / quoted-pair) "]"
+
+ The "Message-ID:" field provides a unique message identifier that
+ refers to a particular version of a particular message. The
+ uniqueness of the message identifier is guaranteed by the host that
+ generates it (see below). This message identifier is intended to be
+ machine readable and not necessarily meaningful to humans. A message
+ identifier pertains to exactly one instantiation of a particular
+ message; subsequent revisions to the message each receive new message
+ identifiers.
+
+ Note: There are many instances when messages are "changed", but those
+ changes do not constitute a new instantiation of that message, and
+ therefore the message would not get a new message identifier. For
+ example, when messages are introduced into the transport system, they
+ are often prepended with additional header fields such as trace
+ fields (described in section 3.6.7) and resent fields (described in
+ section 3.6.6). The addition of such header fields does not change
+ the identity of the message and therefore the original "Message-ID:"
+ field is retained. In all cases, it is the meaning that the sender
+ of the message wishes to convey (i.e., whether this is the same
+ message or a different message) that determines whether or not the
+ "Message-ID:" field changes, not any particular syntactic difference
+ that appears (or does not appear) in the message.
+
+ The "In-Reply-To:" and "References:" fields are used when creating a
+ reply to a message. They hold the message identifier of the original
+ message and the message identifiers of other messages (for example,
+ in the case of a reply to a message which was itself a reply). The
+ "In-Reply-To:" field may be used to identify the message (or
+ messages) to which the new message is a reply, while the
+ "References:" field may be used to identify a "thread" of
+ conversation.
+
+ When creating a reply to a message, the "In-Reply-To:" and
+ "References:" fields of the resultant message are constructed as
+ follows:
+
+ The "In-Reply-To:" field will contain the contents of the "Message-
+ ID:" field of the message to which this one is a reply (the "parent
+ message"). If there is more than one parent message, then the "In-
+ Reply-To:" field will contain the contents of all of the parents'
+ "Message-ID:" fields. If there is no "Message-ID:" field in any of
+ the parent messages, then the new message will have no "In-Reply-To:"
+ field.
+
+
+
+
+
+
+Resnick Standards Track [Page 24]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ The "References:" field will contain the contents of the parent's
+ "References:" field (if any) followed by the contents of the parent's
+ "Message-ID:" field (if any). If the parent message does not contain
+ a "References:" field but does have an "In-Reply-To:" field
+ containing a single message identifier, then the "References:" field
+ will contain the contents of the parent's "In-Reply-To:" field
+ followed by the contents of the parent's "Message-ID:" field (if
+ any). If the parent has none of the "References:", "In-Reply-To:",
+ or "Message-ID:" fields, then the new message will have no
+ "References:" field.
+
+ Note: Some implementations parse the "References:" field to display
+ the "thread of the discussion". These implementations assume that
+ each new message is a reply to a single parent and hence that they
+ can walk backwards through the "References:" field to find the parent
+ of each message listed there. Therefore, trying to form a
+ "References:" field for a reply that has multiple parents is
+ discouraged and how to do so is not defined in this document.
+
+ The message identifier (msg-id) itself MUST be a globally unique
+ identifier for a message. The generator of the message identifier
+ MUST guarantee that the msg-id is unique. There are several
+ algorithms that can be used to accomplish this. Since the msg-id has
+ a similar syntax to angle-addr (identical except that comments and
+ folding white space are not allowed), a good method is to put the
+ domain name (or a domain literal IP address) of the host on which the
+ message identifier was created on the right hand side of the "@", and
+ put a combination of the current absolute date and time along with
+ some other currently unique (perhaps sequential) identifier available
+ on the system (for example, a process id number) on the left hand
+ side. Using a date on the left hand side and a domain name or domain
+ literal on the right hand side makes it possible to guarantee
+ uniqueness since no two hosts use the same domain name or IP address
+ at the same time. Though other algorithms will work, it is
+ RECOMMENDED that the right hand side contain some domain identifier
+ (either of the host itself or otherwise) such that the generator of
+ the message identifier can guarantee the uniqueness of the left hand
+ side within the scope of that domain.
+
+ Semantically, the angle bracket characters are not part of the
+ msg-id; the msg-id is what is contained between the two angle bracket
+ characters.
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 25]
+
+RFC 2822 Internet Message Format April 2001
+
+
+3.6.5. Informational fields
+
+ The informational fields are all optional. The "Keywords:" field
+ contains a comma-separated list of one or more words or
+ quoted-strings. The "Subject:" and "Comments:" fields are
+ unstructured fields as defined in section 2.2.1, and therefore may
+ contain text or folding white space.
+
+subject = "Subject:" unstructured CRLF
+
+comments = "Comments:" unstructured CRLF
+
+keywords = "Keywords:" phrase *("," phrase) CRLF
+
+ These three fields are intended to have only human-readable content
+ with information about the message. The "Subject:" field is the most
+ common and contains a short string identifying the topic of the
+ message. When used in a reply, the field body MAY start with the
+ string "Re: " (from the Latin "res", in the matter of) followed by
+ the contents of the "Subject:" field body of the original message.
+ If this is done, only one instance of the literal string "Re: " ought
+ to be used since use of other strings or more than one instance can
+ lead to undesirable consequences. The "Comments:" field contains any
+ additional comments on the text of the body of the message. The
+ "Keywords:" field contains a comma-separated list of important words
+ and phrases that might be useful for the recipient.
+
+3.6.6. Resent fields
+
+ Resent fields SHOULD be added to any message that is reintroduced by
+ a user into the transport system. A separate set of resent fields
+ SHOULD be added each time this is done. All of the resent fields
+ corresponding to a particular resending of the message SHOULD be
+ together. Each new set of resent fields is prepended to the message;
+ that is, the most recent set of resent fields appear earlier in the
+ message. No other fields in the message are changed when resent
+ fields are added.
+
+ Each of the resent fields corresponds to a particular field elsewhere
+ in the syntax. For instance, the "Resent-Date:" field corresponds to
+ the "Date:" field and the "Resent-To:" field corresponds to the "To:"
+ field. In each case, the syntax for the field body is identical to
+ the syntax given previously for the corresponding field.
+
+ When resent fields are used, the "Resent-From:" and "Resent-Date:"
+ fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
+ "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
+ identical to "Resent-From:".
+
+
+
+Resnick Standards Track [Page 26]
+
+RFC 2822 Internet Message Format April 2001
+
+
+resent-date = "Resent-Date:" date-time CRLF
+
+resent-from = "Resent-From:" mailbox-list CRLF
+
+resent-sender = "Resent-Sender:" mailbox CRLF
+
+resent-to = "Resent-To:" address-list CRLF
+
+resent-cc = "Resent-Cc:" address-list CRLF
+
+resent-bcc = "Resent-Bcc:" (address-list / [CFWS]) CRLF
+
+resent-msg-id = "Resent-Message-ID:" msg-id CRLF
+
+ Resent fields are used to identify a message as having been
+ reintroduced into the transport system by a user. The purpose of
+ using resent fields is to have the message appear to the final
+ recipient as if it were sent directly by the original sender, with
+ all of the original fields remaining the same. Each set of resent
+ fields correspond to a particular resending event. That is, if a
+ message is resent multiple times, each set of resent fields gives
+ identifying information for each individual time. Resent fields are
+ strictly informational. They MUST NOT be used in the normal
+ processing of replies or other such automatic actions on messages.
+
+ Note: Reintroducing a message into the transport system and using
+ resent fields is a different operation from "forwarding".
+ "Forwarding" has two meanings: One sense of forwarding is that a mail
+ reading program can be told by a user to forward a copy of a message
+ to another person, making the forwarded message the body of the new
+ message. A forwarded message in this sense does not appear to have
+ come from the original sender, but is an entirely new message from
+ the forwarder of the message. On the other hand, forwarding is also
+ used to mean when a mail transport program gets a message and
+ forwards it on to a different destination for final delivery. Resent
+ header fields are not intended for use with either type of
+ forwarding.
+
+ The resent originator fields indicate the mailbox of the person(s) or
+ system(s) that resent the message. As with the regular originator
+ fields, there are two forms: a simple "Resent-From:" form which
+ contains the mailbox of the individual doing the resending, and the
+ more complex form, when one individual (identified in the
+ "Resent-Sender:" field) resends a message on behalf of one or more
+ others (identified in the "Resent-From:" field).
+
+ Note: When replying to a resent message, replies behave just as they
+ would with any other message, using the original "From:",
+
+
+
+Resnick Standards Track [Page 27]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ "Reply-To:", "Message-ID:", and other fields. The resent fields are
+ only informational and MUST NOT be used in the normal processing of
+ replies.
+
+ The "Resent-Date:" indicates the date and time at which the resent
+ message is dispatched by the resender of the message. Like the
+ "Date:" field, it is not the date and time that the message was
+ actually transported.
+
+ The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
+ identically to the "To:", "Cc:", and "Bcc:" fields respectively,
+ except that they indicate the recipients of the resent message, not
+ the recipients of the original message.
+
+ The "Resent-Message-ID:" field provides a unique identifier for the
+ resent message.
+
+3.6.7. Trace fields
+
+ The trace fields are a group of header fields consisting of an
+ optional "Return-Path:" field, and one or more "Received:" fields.
+ The "Return-Path:" header field contains a pair of angle brackets
+ that enclose an optional addr-spec. The "Received:" field contains a
+ (possibly empty) list of name/value pairs followed by a semicolon and
+ a date-time specification. The first item of the name/value pair is
+ defined by item-name, and the second item is either an addr-spec, an
+ atom, a domain, or a msg-id. Further restrictions may be applied to
+ the syntax of the trace fields by standards that provide for their
+ use, such as [RFC2821].
+
+trace = [return]
+ 1*received
+
+return = "Return-Path:" path CRLF
+
+path = ([CFWS] "<" ([CFWS] / addr-spec) ">" [CFWS]) /
+ obs-path
+
+received = "Received:" name-val-list ";" date-time CRLF
+
+name-val-list = [CFWS] [name-val-pair *(CFWS name-val-pair)]
+
+name-val-pair = item-name CFWS item-value
+
+item-name = ALPHA *(["-"] (ALPHA / DIGIT))
+
+item-value = 1*angle-addr / addr-spec /
+ atom / domain / msg-id
+
+
+
+Resnick Standards Track [Page 28]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ A full discussion of the Internet mail use of trace fields is
+ contained in [RFC2821]. For the purposes of this standard, the trace
+ fields are strictly informational, and any formal interpretation of
+ them is outside of the scope of this document.
+
+3.6.8. Optional fields
+
+ Fields may appear in messages that are otherwise unspecified in this
+ standard. They MUST conform to the syntax of an optional-field.
+ This is a field name, made up of the printable US-ASCII characters
+ except SP and colon, followed by a colon, followed by any text which
+ conforms to unstructured.
+
+ The field names of any optional-field MUST NOT be identical to any
+ field name specified elsewhere in this standard.
+
+optional-field = field-name ":" unstructured CRLF
+
+field-name = 1*ftext
+
+ftext = %d33-57 / ; Any character except
+ %d59-126 ; controls, SP, and
+ ; ":".
+
+ For the purposes of this standard, any optional field is
+ uninterpreted.
+
+4. Obsolete Syntax
+
+ Earlier versions of this standard allowed for different (usually more
+ liberal) syntax than is allowed in this version. Also, there have
+ been syntactic elements used in messages on the Internet whose
+ interpretation have never been documented. Though some of these
+ syntactic forms MUST NOT be generated according to the grammar in
+ section 3, they MUST be accepted and parsed by a conformant receiver.
+ This section documents many of these syntactic elements. Taking the
+ grammar in section 3 and adding the definitions presented in this
+ section will result in the grammar to use for interpretation of
+ messages.
+
+ Note: This section identifies syntactic forms that any implementation
+ MUST reasonably interpret. However, there are certainly Internet
+ messages which do not conform to even the additional syntax given in
+ this section. The fact that a particular form does not appear in any
+ section of this document is not justification for computer programs
+ to crash or for malformed data to be irretrievably lost by any
+ implementation. To repeat an example, though this document requires
+ lines in messages to be no longer than 998 characters, silently
+
+
+
+Resnick Standards Track [Page 29]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ discarding the 999th and subsequent characters in a line without
+ warning would still be bad behavior for an implementation. It is up
+ to the implementation to deal with messages robustly.
+
+ One important difference between the obsolete (interpreting) and the
+ current (generating) syntax is that in structured header field bodies
+ (i.e., between the colon and the CRLF of any structured header
+ field), white space characters, including folding white space, and
+ comments can be freely inserted between any syntactic tokens. This
+ allows many complex forms that have proven difficult for some
+ implementations to parse.
+
+ Another key difference between the obsolete and the current syntax is
+ that the rule in section 3.2.3 regarding lines composed entirely of
+ white space in comments and folding white space does not apply. See
+ the discussion of folding white space in section 4.2 below.
+
+ Finally, certain characters that were formerly allowed in messages
+ appear in this section. The NUL character (ASCII value 0) was once
+ allowed, but is no longer for compatibility reasons. CR and LF were
+ allowed to appear in messages other than as CRLF; this use is also
+ shown here.
+
+ Other differences in syntax and semantics are noted in the following
+ sections.
+
+4.1. Miscellaneous obsolete tokens
+
+ These syntactic elements are used elsewhere in the obsolete syntax or
+ in the main syntax. The obs-char and obs-qp elements each add ASCII
+ value 0. Bare CR and bare LF are added to obs-text and obs-utext.
+ The period character is added to obs-phrase. The obs-phrase-list
+ provides for "empty" elements in a comma-separated list of phrases.
+
+ Note: The "period" (or "full stop") character (".") in obs-phrase is
+ not a form that was allowed in earlier versions of this or any other
+ standard. Period (nor any other character from specials) was not
+ allowed in phrase because it introduced a parsing difficulty
+ distinguishing between phrases and portions of an addr-spec (see
+ section 4.4). It appears here because the period character is
+ currently used in many messages in the display-name portion of
+ addresses, especially for initials in names, and therefore must be
+ interpreted properly. In the future, period may appear in the
+ regular syntax of phrase.
+
+obs-qp = "\" (%d0-127)
+
+obs-text = *LF *CR *(obs-char *LF *CR)
+
+
+
+Resnick Standards Track [Page 30]
+
+RFC 2822 Internet Message Format April 2001
+
+
+obs-char = %d0-9 / %d11 / ; %d0-127 except CR and
+ %d12 / %d14-127 ; LF
+
+obs-utext = obs-text
+
+obs-phrase = word *(word / "." / CFWS)
+
+obs-phrase-list = phrase / 1*([phrase] [CFWS] "," [CFWS]) [phrase]
+
+ Bare CR and bare LF appear in messages with two different meanings.
+ In many cases, bare CR or bare LF are used improperly instead of CRLF
+ to indicate line separators. In other cases, bare CR and bare LF are
+ used simply as ASCII control characters with their traditional ASCII
+ meanings.
+
+4.2. Obsolete folding white space
+
+ In the obsolete syntax, any amount of folding white space MAY be
+ inserted where the obs-FWS rule is allowed. This creates the
+ possibility of having two consecutive "folds" in a line, and
+ therefore the possibility that a line which makes up a folded header
+ field could be composed entirely of white space.
+
+ obs-FWS = 1*WSP *(CRLF 1*WSP)
+
+4.3. Obsolete Date and Time
+
+ The syntax for the obsolete date format allows a 2 digit year in the
+ date field and allows for a list of alphabetic time zone
+ specifications that were used in earlier versions of this standard.
+ It also permits comments and folding white space between many of the
+ tokens.
+
+obs-day-of-week = [CFWS] day-name [CFWS]
+
+obs-year = [CFWS] 2*DIGIT [CFWS]
+
+obs-month = CFWS month-name CFWS
+
+obs-day = [CFWS] 1*2DIGIT [CFWS]
+
+obs-hour = [CFWS] 2DIGIT [CFWS]
+
+obs-minute = [CFWS] 2DIGIT [CFWS]
+
+obs-second = [CFWS] 2DIGIT [CFWS]
+
+obs-zone = "UT" / "GMT" / ; Universal Time
+
+
+
+Resnick Standards Track [Page 31]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ ; North American UT
+ ; offsets
+ "EST" / "EDT" / ; Eastern: - 5/ - 4
+ "CST" / "CDT" / ; Central: - 6/ - 5
+ "MST" / "MDT" / ; Mountain: - 7/ - 6
+ "PST" / "PDT" / ; Pacific: - 8/ - 7
+
+ %d65-73 / ; Military zones - "A"
+ %d75-90 / ; through "I" and "K"
+ %d97-105 / ; through "Z", both
+ %d107-122 ; upper and lower case
+
+ Where a two or three digit year occurs in a date, the year is to be
+ interpreted as follows: If a two digit year is encountered whose
+ value is between 00 and 49, the year is interpreted by adding 2000,
+ ending up with a value between 2000 and 2049. If a two digit year is
+ encountered with a value between 50 and 99, or any three digit year
+ is encountered, the year is interpreted by adding 1900.
+
+ In the obsolete time zone, "UT" and "GMT" are indications of
+ "Universal Time" and "Greenwich Mean Time" respectively and are both
+ semantically identical to "+0000".
+
+ The remaining three character zones are the US time zones. The first
+ letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
+ "Mountain" and "Pacific". The second letter is either "S" for
+ "Standard" time, or "D" for "Daylight" (or summer) time. Their
+ interpretations are as follows:
+
+ EDT is semantically equivalent to -0400
+ EST is semantically equivalent to -0500
+ CDT is semantically equivalent to -0500
+ CST is semantically equivalent to -0600
+ MDT is semantically equivalent to -0600
+ MST is semantically equivalent to -0700
+ PDT is semantically equivalent to -0700
+ PST is semantically equivalent to -0800
+
+ The 1 character military time zones were defined in a non-standard
+ way in [RFC822] and are therefore unpredictable in their meaning.
+ The original definitions of the military zones "A" through "I" are
+ equivalent to "+0100" through "+0900" respectively; "K", "L", and "M"
+ are equivalent to "+1000", "+1100", and "+1200" respectively; "N"
+ through "Y" are equivalent to "-0100" through "-1200" respectively;
+ and "Z" is equivalent to "+0000". However, because of the error in
+ [RFC822], they SHOULD all be considered equivalent to "-0000" unless
+ there is out-of-band information confirming their meaning.
+
+
+
+
+Resnick Standards Track [Page 32]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Other multi-character (usually between 3 and 5) alphabetic time zones
+ have been used in Internet messages. Any such time zone whose
+ meaning is not known SHOULD be considered equivalent to "-0000"
+ unless there is out-of-band information confirming their meaning.
+
+4.4. Obsolete Addressing
+
+ There are three primary differences in addressing. First, mailbox
+ addresses were allowed to have a route portion before the addr-spec
+ when enclosed in "<" and ">". The route is simply a comma-separated
+ list of domain names, each preceded by "@", and the list terminated
+ by a colon. Second, CFWS were allowed between the period-separated
+ elements of local-part and domain (i.e., dot-atom was not used). In
+ addition, local-part is allowed to contain quoted-string in addition
+ to just atom. Finally, mailbox-list and address-list were allowed to
+ have "null" members. That is, there could be two or more commas in
+ such a list with nothing in between them.
+
+obs-angle-addr = [CFWS] "<" [obs-route] addr-spec ">" [CFWS]
+
+obs-route = [CFWS] obs-domain-list ":" [CFWS]
+
+obs-domain-list = "@" domain *(*(CFWS / "," ) [CFWS] "@" domain)
+
+obs-local-part = word *("." word)
+
+obs-domain = atom *("." atom)
+
+obs-mbox-list = 1*([mailbox] [CFWS] "," [CFWS]) [mailbox]
+
+obs-addr-list = 1*([address] [CFWS] "," [CFWS]) [address]
+
+ When interpreting addresses, the route portion SHOULD be ignored.
+
+4.5. Obsolete header fields
+
+ Syntactically, the primary difference in the obsolete field syntax is
+ that it allows multiple occurrences of any of the fields and they may
+ occur in any order. Also, any amount of white space is allowed
+ before the ":" at the end of the field name.
+
+obs-fields = *(obs-return /
+ obs-received /
+ obs-orig-date /
+ obs-from /
+ obs-sender /
+ obs-reply-to /
+ obs-to /
+
+
+
+Resnick Standards Track [Page 33]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ obs-cc /
+ obs-bcc /
+ obs-message-id /
+ obs-in-reply-to /
+ obs-references /
+ obs-subject /
+ obs-comments /
+ obs-keywords /
+ obs-resent-date /
+ obs-resent-from /
+ obs-resent-send /
+ obs-resent-rply /
+ obs-resent-to /
+ obs-resent-cc /
+ obs-resent-bcc /
+ obs-resent-mid /
+ obs-optional)
+
+ Except for destination address fields (described in section 4.5.3),
+ the interpretation of multiple occurrences of fields is unspecified.
+ Also, the interpretation of trace fields and resent fields which do
+ not occur in blocks prepended to the message is unspecified as well.
+ Unless otherwise noted in the following sections, interpretation of
+ other fields is identical to the interpretation of their non-obsolete
+ counterparts in section 3.
+
+4.5.1. Obsolete origination date field
+
+obs-orig-date = "Date" *WSP ":" date-time CRLF
+
+4.5.2. Obsolete originator fields
+
+obs-from = "From" *WSP ":" mailbox-list CRLF
+
+obs-sender = "Sender" *WSP ":" mailbox CRLF
+
+obs-reply-to = "Reply-To" *WSP ":" mailbox-list CRLF
+
+4.5.3. Obsolete destination address fields
+
+obs-to = "To" *WSP ":" address-list CRLF
+
+obs-cc = "Cc" *WSP ":" address-list CRLF
+
+obs-bcc = "Bcc" *WSP ":" (address-list / [CFWS]) CRLF
+
+
+
+
+
+
+Resnick Standards Track [Page 34]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ When multiple occurrences of destination address fields occur in a
+ message, they SHOULD be treated as if the address-list in the first
+ occurrence of the field is combined with the address lists of the
+ subsequent occurrences by adding a comma and concatenating.
+
+4.5.4. Obsolete identification fields
+
+ The obsolete "In-Reply-To:" and "References:" fields differ from the
+ current syntax in that they allow phrase (words or quoted strings) to
+ appear. The obsolete forms of the left and right sides of msg-id
+ allow interspersed CFWS, making them syntactically identical to
+ local-part and domain respectively.
+
+obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
+
+obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
+
+obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
+
+obs-id-left = local-part
+
+obs-id-right = domain
+
+ For purposes of interpretation, the phrases in the "In-Reply-To:" and
+ "References:" fields are ignored.
+
+ Semantically, none of the optional CFWS surrounding the local-part
+ and the domain are part of the obs-id-left and obs-id-right
+ respectively.
+
+4.5.5. Obsolete informational fields
+
+obs-subject = "Subject" *WSP ":" unstructured CRLF
+
+obs-comments = "Comments" *WSP ":" unstructured CRLF
+
+obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
+
+4.5.6. Obsolete resent fields
+
+ The obsolete syntax adds a "Resent-Reply-To:" field, which consists
+ of the field name, the optional comments and folding white space, the
+ colon, and a comma separated list of addresses.
+
+obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
+
+obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
+
+
+
+
+Resnick Standards Track [Page 35]
+
+RFC 2822 Internet Message Format April 2001
+
+
+obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
+
+obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
+
+obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
+
+obs-resent-bcc = "Resent-Bcc" *WSP ":"
+ (address-list / [CFWS]) CRLF
+
+obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
+
+obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
+
+ As with other resent fields, the "Resent-Reply-To:" field is to be
+ treated as trace information only.
+
+4.5.7. Obsolete trace fields
+
+ The obs-return and obs-received are again given here as template
+ definitions, just as return and received are in section 3. Their
+ full syntax is given in [RFC2821].
+
+obs-return = "Return-Path" *WSP ":" path CRLF
+
+obs-received = "Received" *WSP ":" name-val-list CRLF
+
+obs-path = obs-angle-addr
+
+4.5.8. Obsolete optional fields
+
+obs-optional = field-name *WSP ":" unstructured CRLF
+
+5. Security Considerations
+
+ Care needs to be taken when displaying messages on a terminal or
+ terminal emulator. Powerful terminals may act on escape sequences
+ and other combinations of ASCII control characters with a variety of
+ consequences. They can remap the keyboard or permit other
+ modifications to the terminal which could lead to denial of service
+ or even damaged data. They can trigger (sometimes programmable)
+ answerback messages which can allow a message to cause commands to be
+ issued on the recipient's behalf. They can also effect the operation
+ of terminal attached devices such as printers. Message viewers may
+ wish to strip potentially dangerous terminal escape sequences from
+ the message prior to display. However, other escape sequences appear
+ in messages for useful purposes (cf. [RFC2045, RFC2046, RFC2047,
+ RFC2048, RFC2049, ISO2022]) and therefore should not be stripped
+ indiscriminately.
+
+
+
+Resnick Standards Track [Page 36]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Transmission of non-text objects in messages raises additional
+ security issues. These issues are discussed in [RFC2045, RFC2046,
+ RFC2047, RFC2048, RFC2049].
+
+ Many implementations use the "Bcc:" (blind carbon copy) field
+ described in section 3.6.3 to facilitate sending messages to
+ recipients without revealing the addresses of one or more of the
+ addressees to the other recipients. Mishandling this use of "Bcc:"
+ has implications for confidential information that might be revealed,
+ which could eventually lead to security problems through knowledge of
+ even the existence of a particular mail address. For example, if
+ using the first method described in section 3.6.3, where the "Bcc:"
+ line is removed from the message, blind recipients have no explicit
+ indication that they have been sent a blind copy, except insofar as
+ their address does not appear in the message header. Because of
+ this, one of the blind addressees could potentially send a reply to
+ all of the shown recipients and accidentally reveal that the message
+ went to the blind recipient. When the second method from section
+ 3.6.3 is used, the blind recipient's address appears in the "Bcc:"
+ field of a separate copy of the message. If the "Bcc:" field sent
+ contains all of the blind addressees, all of the "Bcc:" recipients
+ will be seen by each "Bcc:" recipient. Even if a separate message is
+ sent to each "Bcc:" recipient with only the individual's address,
+ implementations still need to be careful to process replies to the
+ message as per section 3.6.3 so as not to accidentally reveal the
+ blind recipient to other recipients.
+
+6. Bibliography
+
+ [ASCII] American National Standards Institute (ANSI), Coded
+ Character Set - 7-Bit American National Standard Code for
+ Information Interchange, ANSI X3.4, 1986.
+
+ [ISO2022] International Organization for Standardization (ISO),
+ Information processing - ISO 7-bit and 8-bit coded
+ character sets - Code extension techniques, Third edition
+ - 1986-05-01, ISO 2022, 1986.
+
+ [RFC822] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", RFC 822, August 1982.
+
+ [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Two: Media Types", RFC 2046,
+ November 1996.
+
+
+
+Resnick Standards Track [Page 37]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ [RFC2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
+ Part Three: Message Header Extensions for Non-ASCII Text",
+ RFC 2047, November 1996.
+
+ [RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
+ Internet Mail Extensions (MIME) Part Four: Format of
+ Internet Message Bodies", RFC 2048, November 1996.
+
+ [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part Five: Conformance Criteria and
+ Examples", RFC 2049, November 1996.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2234] Crocker, D., Editor, and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+ [RFC2821] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
+ 2821, March 2001.
+
+ [STD3] Braden, R., "Host Requirements", STD 3, RFC 1122 and RFC
+ 1123, October 1989.
+
+ [STD12] Mills, D., "Network Time Protocol", STD 12, RFC 1119,
+ September 1989.
+
+ [STD13] Mockapetris, P., "Domain Name System", STD 13, RFC 1034
+ and RFC 1035, November 1987.
+
+ [STD14] Partridge, C., "Mail Routing and the Domain System", STD
+ 14, RFC 974, January 1986.
+
+7. Editor's Address
+
+ Peter W. Resnick
+ QUALCOMM Incorporated
+ 5775 Morehouse Drive
+ San Diego, CA 92121-1714
+ USA
+
+ Phone: +1 858 651 4478
+ Fax: +1 858 651 1102
+ EMail: presnick@qualcomm.com
+
+
+
+
+
+
+
+Resnick Standards Track [Page 38]
+
+RFC 2822 Internet Message Format April 2001
+
+
+8. Acknowledgements
+
+ Many people contributed to this document. They included folks who
+ participated in the Detailed Revision and Update of Messaging
+ Standards (DRUMS) Working Group of the Internet Engineering Task
+ Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
+ people who simply sent their comments in via e-mail. The editor is
+ deeply indebted to them all and thanks them sincerely. The below
+ list includes everyone who sent e-mail concerning this document.
+ Hopefully, everyone who contributed is named here:
+
+ Matti Aarnio Barry Finkel Larry Masinter
+ Tanaka Akira Erik Forsberg Denis McKeon
+ Russ Allbery Chuck Foster William P McQuillan
+ Eric Allman Paul Fox Alexey Melnikov
+ Harald Tveit Alvestrand Klaus M. Frank Perry E. Metzger
+ Ran Atkinson Ned Freed Steven Miller
+ Jos Backus Jochen Friedrich Keith Moore
+ Bruce Balden Randall C. Gellens John Gardiner Myers
+ Dave Barr Sukvinder Singh Gill Chris Newman
+ Alan Barrett Tim Goodwin John W. Noerenberg
+ John Beck Philip Guenther Eric Norman
+ J. Robert von Behren Tony Hansen Mike O'Dell
+ Jos den Bekker John Hawkinson Larry Osterman
+ D. J. Bernstein Philip Hazel Paul Overell
+ James Berriman Kai Henningsen Jacob Palme
+ Norbert Bollow Robert Herriot Michael A. Patton
+ Raj Bose Paul Hethmon Uzi Paz
+ Antony Bowesman Jim Hill Michael A. Quinlan
+ Scott Bradner Paul E. Hoffman Eric S. Raymond
+ Randy Bush Steve Hole Sam Roberts
+ Tom Byrer Kari Hurtta Hugh Sasse
+ Bruce Campbell Marco S. Hyman Bart Schaefer
+ Larry Campbell Ofer Inbar Tom Scola
+ W. J. Carpenter Olle Jarnefors Wolfgang Segmuller
+ Michael Chapman Kevin Johnson Nick Shelness
+ Richard Clayton Sudish Joseph John Stanley
+ Maurizio Codogno Maynard Kang Einar Stefferud
+ Jim Conklin Prabhat Keni Jeff Stephenson
+ R. Kelley Cook John C. Klensin Bernard Stern
+ Steve Coya Graham Klyne Peter Sylvester
+ Mark Crispin Brad Knowles Mark Symons
+ Dave Crocker Shuhei Kobayashi Eric Thomas
+ Matt Curtin Peter Koch Lee Thompson
+ Michael D'Errico Dan Kohn Karel De Vriendt
+ Cyrus Daboo Christian Kuhtz Matthew Wall
+ Jutta Degener Anand Kumria Rolf Weber
+ Mark Delany Steen Larsen Brent B. Welch
+
+
+
+Resnick Standards Track [Page 39]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Steve Dorner Eliot Lear Dan Wing
+ Harold A. Driscoll Barry Leiba Jack De Winter
+ Michael Elkins Jay Levitt Gregory J. Woodhouse
+ Robert Elz Lars-Johan Liman Greg A. Woods
+ Johnny Eriksson Charles Lindsey Kazu Yamamoto
+ Erik E. Fair Pete Loshin Alain Zahm
+ Roger Fajman Simon Lyall Jamie Zawinski
+ Patrik Faltstrom Bill Manning Timothy S. Zurcher
+ Claus Andre Farber John Martin
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 40]
+
+RFC 2822 Internet Message Format April 2001
+
+
+Appendix A. Example messages
+
+ This section presents a selection of messages. These are intended to
+ assist in the implementation of this standard, but should not be
+ taken as normative; that is to say, although the examples in this
+ section were carefully reviewed, if there happens to be a conflict
+ between these examples and the syntax described in sections 3 and 4
+ of this document, the syntax in those sections is to be taken as
+ correct.
+
+ Messages are delimited in this section between lines of "----". The
+ "----" lines are not part of the message itself.
+
+A.1. Addressing examples
+
+ The following are examples of messages that might be sent between two
+ individuals.
+
+A.1.1. A message from one person to another with simple addressing
+
+ This could be called a canonical message. It has a single author,
+ John Doe, a single recipient, Mary Smith, a subject, the date, a
+ message identifier, and a textual message in the body.
+
+----
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 41]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ If John's secretary Michael actually sent the message, though John
+ was the author and replies to this message should go back to him, the
+ sender field would be used:
+
+----
+From: John Doe <jdoe@machine.example>
+Sender: Michael Jones <mjones@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+A.1.2. Different types of mailboxes
+
+ This message includes multiple addresses in the destination fields
+ and also uses several different forms of addresses.
+
+----
+From: "Joe Q. Public" <john.q.public@example.com>
+To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
+Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
+Date: Tue, 1 Jul 2003 10:52:37 +0200
+Message-ID: <5678.21-Nov-1997@example.com>
+
+Hi everyone.
+----
+
+ Note that the display names for Joe Q. Public and Giant; "Big" Box
+ needed to be enclosed in double-quotes because the former contains
+ the period and the latter contains both semicolon and double-quote
+ characters (the double-quote characters appearing as quoted-pair
+ construct). Conversely, the display name for Who? could appear
+ without them because the question mark is legal in an atom. Notice
+ also that jdoe@example.org and boss@nil.test have no display names
+ associated with them at all, and jdoe@example.org uses the simpler
+ address form without the angle brackets.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 42]
+
+RFC 2822 Internet Message Format April 2001
+
+
+A.1.3. Group addresses
+
+----
+From: Pete <pete@silly.example>
+To: A Group:Chris Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
+Cc: Undisclosed recipients:;
+Date: Thu, 13 Feb 1969 23:32:54 -0330
+Message-ID: <testabcd.1234@silly.example>
+
+Testing.
+----
+
+ In this message, the "To:" field has a single group recipient named A
+ Group which contains 3 addresses, and a "Cc:" field with an empty
+ group recipient named Undisclosed recipients.
+
+A.2. Reply messages
+
+ The following is a series of three messages that make up a
+ conversation thread between John and Mary. John firsts sends a
+ message to Mary, Mary then replies to John's message, and then John
+ replies to Mary's reply message.
+
+ Note especially the "Message-ID:", "References:", and "In-Reply-To:"
+ fields in each message.
+
+----
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 43]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ When sending replies, the Subject field is often retained, though
+ prepended with "Re: " as described in section 3.6.5.
+
+----
+From: Mary Smith <mary@example.net>
+To: John Doe <jdoe@machine.example>
+Reply-To: "Mary Smith: Personal Account" <smith@home.example>
+Subject: Re: Saying Hello
+Date: Fri, 21 Nov 1997 10:01:10 -0600
+Message-ID: <3456@example.net>
+In-Reply-To: <1234@local.machine.example>
+References: <1234@local.machine.example>
+
+This is a reply to your hello.
+----
+
+ Note the "Reply-To:" field in the above message. When John replies
+ to Mary's message above, the reply should go to the address in the
+ "Reply-To:" field instead of the address in the "From:" field.
+
+----
+To: "Mary Smith: Personal Account" <smith@home.example>
+From: John Doe <jdoe@machine.example>
+Subject: Re: Saying Hello
+Date: Fri, 21 Nov 1997 11:00:00 -0600
+Message-ID: <abcd.1234@local.machine.tld>
+In-Reply-To: <3456@example.net>
+References: <1234@local.machine.example> <3456@example.net>
+
+This is a reply to your reply.
+----
+
+A.3. Resent messages
+
+ Start with the message that has been used as an example several
+ times:
+
+----
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+
+
+
+Resnick Standards Track [Page 44]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ Say that Mary, upon receiving this message, wishes to send a copy of
+ the message to Jane such that (a) the message would appear to have
+ come straight from John; (b) if Jane replies to the message, the
+ reply should go back to John; and (c) all of the original
+ information, like the date the message was originally sent to Mary,
+ the message identifier, and the original addressee, is preserved. In
+ this case, resent fields are prepended to the message:
+
+----
+Resent-From: Mary Smith <mary@example.net>
+Resent-To: Jane Brown <j-brown@other.example>
+Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
+Resent-Message-ID: <78910@example.net>
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+ If Jane, in turn, wished to resend this message to another person,
+ she would prepend her own set of resent header fields to the above
+ and send that.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 45]
+
+RFC 2822 Internet Message Format April 2001
+
+
+A.4. Messages with trace fields
+
+ As messages are sent through the transport system as described in
+ [RFC2821], trace fields are prepended to the message. The following
+ is an example of what those trace fields might look like. Note that
+ there is some folding white space in the first one since these lines
+ can be long.
+
+----
+Received: from x.y.test
+ by example.net
+ via TCP
+ with ESMTP
+ id ABC12345
+ for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
+Received: from machine.example by x.y.test; 21 Nov 1997 10:01:22 -0600
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 46]
+
+RFC 2822 Internet Message Format April 2001
+
+
+A.5. White space, comments, and other oddities
+
+ White space, including folding white space, and comments can be
+ inserted between many of the tokens of fields. Taking the example
+ from A.1.3, white space and comments can be inserted into all of the
+ fields.
+
+----
+From: Pete(A wonderful \) chap) <pete(his account)@silly.test(his host)>
+To:A Group(Some people)
+ :Chris Jones <c@(Chris's host.)public.example>,
+ joe@example.org,
+ John <jdoe@one.test> (my dear friend); (the end of the group)
+Cc:(Empty list)(start)Undisclosed recipients :(nobody(that I know)) ;
+Date: Thu,
+ 13
+ Feb
+ 1969
+ 23:32
+ -0330 (Newfoundland Time)
+Message-ID: <testabcd.1234@silly.test>
+
+Testing.
+----
+
+ The above example is aesthetically displeasing, but perfectly legal.
+ Note particularly (1) the comments in the "From:" field (including
+ one that has a ")" character appearing as part of a quoted-pair); (2)
+ the white space absent after the ":" in the "To:" field as well as
+ the comment and folding white space after the group name, the special
+ character (".") in the comment in Chris Jones's address, and the
+ folding white space before and after "joe@example.org,"; (3) the
+ multiple and nested comments in the "Cc:" field as well as the
+ comment immediately following the ":" after "Cc"; (4) the folding
+ white space (but no comments except at the end) and the missing
+ seconds in the time of the date field; and (5) the white space before
+ (but not within) the identifier in the "Message-ID:" field.
+
+A.6. Obsoleted forms
+
+ The following are examples of obsolete (that is, the "MUST NOT
+ generate") syntactic elements described in section 4 of this
+ document.
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 47]
+
+RFC 2822 Internet Message Format April 2001
+
+
+A.6.1. Obsolete addressing
+
+ Note in the below example the lack of quotes around Joe Q. Public,
+ the route that appears in the address for Mary Smith, the two commas
+ that appear in the "To:" field, and the spaces that appear around the
+ "." in the jdoe address.
+
+----
+From: Joe Q. Public <john.q.public@example.com>
+To: Mary Smith <@machine.tld:mary@example.net>, , jdoe@test . example
+Date: Tue, 1 Jul 2003 10:52:37 +0200
+Message-ID: <5678.21-Nov-1997@example.com>
+
+Hi everyone.
+----
+
+A.6.2. Obsolete dates
+
+ The following message uses an obsolete date format, including a non-
+ numeric time zone and a two digit year. Note that although the
+ day-of-week is missing, that is not specific to the obsolete syntax;
+ it is optional in the current syntax as well.
+
+----
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: 21 Nov 97 09:55:06 GMT
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+A.6.3. Obsolete white space and comments
+
+ White space and comments can appear between many more elements than
+ in the current syntax. Also, folding lines that are made up entirely
+ of white space are legal.
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 48]
+
+RFC 2822 Internet Message Format April 2001
+
+
+----
+From : John Doe <jdoe@machine(comment). example>
+To : Mary Smith
+__
+ <mary@example.net>
+Subject : Saying Hello
+Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
+Message-ID : <1234 @ local(blah) .machine .example>
+
+This is a message just to say hello.
+So, "Hello".
+----
+
+ Note especially the second line of the "To:" field. It starts with
+ two space characters. (Note that "__" represent blank spaces.)
+ Therefore, it is considered part of the folding as described in
+ section 4.2. Also, the comments and white space throughout
+ addresses, dates, and message identifiers are all part of the
+ obsolete syntax.
+
+Appendix B. Differences from earlier standards
+
+ This appendix contains a list of changes that have been made in the
+ Internet Message Format from earlier standards, specifically [RFC822]
+ and [STD3]. Items marked with an asterisk (*) below are items which
+ appear in section 4 of this document and therefore can no longer be
+ generated.
+
+ 1. Period allowed in obsolete form of phrase.
+ 2. ABNF moved out of document to [RFC2234].
+ 3. Four or more digits allowed for year.
+ 4. Header field ordering (and lack thereof) made explicit.
+ 5. Encrypted header field removed.
+ 6. Received syntax loosened to allow any token/value pair.
+ 7. Specifically allow and give meaning to "-0000" time zone.
+ 8. Folding white space is not allowed between every token.
+ 9. Requirement for destinations removed.
+ 10. Forwarding and resending redefined.
+ 11. Extension header fields no longer specifically called out.
+ 12. ASCII 0 (null) removed.*
+ 13. Folding continuation lines cannot contain only white space.*
+ 14. Free insertion of comments not allowed in date.*
+ 15. Non-numeric time zones not allowed.*
+ 16. Two digit years not allowed.*
+ 17. Three digit years interpreted, but not allowed for generation.
+ 18. Routes in addresses not allowed.*
+ 19. CFWS within local-parts and domains not allowed.*
+ 20. Empty members of address lists not allowed.*
+
+
+
+Resnick Standards Track [Page 49]
+
+RFC 2822 Internet Message Format April 2001
+
+
+ 21. Folding white space between field name and colon not allowed.*
+ 22. Comments between field name and colon not allowed.
+ 23. Tightened syntax of in-reply-to and references.*
+ 24. CFWS within msg-id not allowed.*
+ 25. Tightened semantics of resent fields as informational only.
+ 26. Resent-Reply-To not allowed.*
+ 27. No multiple occurrences of fields (except resent and received).*
+ 28. Free CR and LF not allowed.*
+ 29. Routes in return path not allowed.*
+ 30. Line length limits specified.
+ 31. Bcc more clearly specified.
+
+Appendix C. Notices
+
+ Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ intellectual property or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; neither does it represent that it
+ has made any effort to identify any such rights. Information on the
+ IETF's procedures with respect to rights in standards-track and
+ standards-related documentation can be found in BCP-11. Copies of
+ claims of rights made available for publication and any assurances of
+ licenses to be made available, or the result of an attempt made to
+ obtain a general license or permission for the use of such
+ proprietary rights by implementors or users of this specification can
+ be obtained from the IETF Secretariat.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 50]
+
+RFC 2822 Internet Message Format April 2001
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 51]
+
diff --git a/rfc/rfc3501.txt b/rfc/rfc3501.txt
@@ -0,0 +1,6051 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 3501 University of Washington
+Obsoletes: 2060 March 2003
+Category: Standards Track
+
+
+ INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1)
+ allows a client to access and manipulate electronic mail messages on
+ a server. IMAP4rev1 permits manipulation of mailboxes (remote
+ message folders) in a way that is functionally equivalent to local
+ folders. IMAP4rev1 also provides the capability for an offline
+ client to resynchronize with the server.
+
+ IMAP4rev1 includes operations for creating, deleting, and renaming
+ mailboxes, checking for new messages, permanently removing messages,
+ setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching,
+ and selective fetching of message attributes, texts, and portions
+ thereof. Messages in IMAP4rev1 are accessed by the use of numbers.
+ These numbers are either message sequence numbers or unique
+ identifiers.
+
+ IMAP4rev1 supports a single server. A mechanism for accessing
+ configuration information to support multiple IMAP4rev1 servers is
+ discussed in RFC 2244.
+
+ IMAP4rev1 does not specify a means of posting mail; this function is
+ handled by a mail transfer protocol such as RFC 2821.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Table of Contents
+
+ IMAP4rev1 Protocol Specification ................................ 4
+ 1. How to Read This Document ............................... 4
+ 1.1. Organization of This Document ........................... 4
+ 1.2. Conventions Used in This Document ....................... 4
+ 1.3. Special Notes to Implementors ........................... 5
+ 2. Protocol Overview ....................................... 6
+ 2.1. Link Level .............................................. 6
+ 2.2. Commands and Responses .................................. 6
+ 2.2.1. Client Protocol Sender and Server Protocol Receiver ..... 6
+ 2.2.2. Server Protocol Sender and Client Protocol Receiver ..... 7
+ 2.3. Message Attributes ...................................... 8
+ 2.3.1. Message Numbers ......................................... 8
+ 2.3.1.1. Unique Identifier (UID) Message Attribute ....... 8
+ 2.3.1.2. Message Sequence Number Message Attribute ....... 10
+ 2.3.2. Flags Message Attribute ................................. 11
+ 2.3.3. Internal Date Message Attribute ......................... 12
+ 2.3.4. [RFC-2822] Size Message Attribute ....................... 12
+ 2.3.5. Envelope Structure Message Attribute .................... 12
+ 2.3.6. Body Structure Message Attribute ........................ 12
+ 2.4. Message Texts ........................................... 13
+ 3. State and Flow Diagram .................................. 13
+ 3.1. Not Authenticated State ................................. 13
+ 3.2. Authenticated State ..................................... 13
+ 3.3. Selected State .......................................... 13
+ 3.4. Logout State ............................................ 14
+ 4. Data Formats ............................................ 16
+ 4.1. Atom .................................................... 16
+ 4.2. Number .................................................. 16
+ 4.3. String .................................................. 16
+ 4.3.1. 8-bit and Binary Strings ................................ 17
+ 4.4. Parenthesized List ...................................... 17
+ 4.5. NIL ..................................................... 17
+ 5. Operational Considerations .............................. 18
+ 5.1. Mailbox Naming .......................................... 18
+ 5.1.1. Mailbox Hierarchy Naming ................................ 19
+ 5.1.2. Mailbox Namespace Naming Convention ..................... 19
+ 5.1.3. Mailbox International Naming Convention ................. 19
+ 5.2. Mailbox Size and Message Status Updates ................. 21
+ 5.3. Response when no Command in Progress .................... 21
+ 5.4. Autologout Timer ........................................ 22
+ 5.5. Multiple Commands in Progress ........................... 22
+ 6. Client Commands ........................................ 23
+ 6.1. Client Commands - Any State ............................ 24
+ 6.1.1. CAPABILITY Command ..................................... 24
+ 6.1.2. NOOP Command ........................................... 25
+ 6.1.3. LOGOUT Command ......................................... 26
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 6.2. Client Commands - Not Authenticated State .............. 26
+ 6.2.1. STARTTLS Command ....................................... 27
+ 6.2.2. AUTHENTICATE Command ................................... 28
+ 6.2.3. LOGIN Command .......................................... 30
+ 6.3. Client Commands - Authenticated State .................. 31
+ 6.3.1. SELECT Command ......................................... 32
+ 6.3.2. EXAMINE Command ........................................ 34
+ 6.3.3. CREATE Command ......................................... 34
+ 6.3.4. DELETE Command ......................................... 35
+ 6.3.5. RENAME Command ......................................... 37
+ 6.3.6. SUBSCRIBE Command ...................................... 39
+ 6.3.7. UNSUBSCRIBE Command .................................... 39
+ 6.3.8. LIST Command ........................................... 40
+ 6.3.9. LSUB Command ........................................... 43
+ 6.3.10. STATUS Command ......................................... 44
+ 6.3.11. APPEND Command ......................................... 46
+ 6.4. Client Commands - Selected State ....................... 47
+ 6.4.1. CHECK Command .......................................... 47
+ 6.4.2. CLOSE Command .......................................... 48
+ 6.4.3. EXPUNGE Command ........................................ 49
+ 6.4.4. SEARCH Command ......................................... 49
+ 6.4.5. FETCH Command .......................................... 54
+ 6.4.6. STORE Command .......................................... 58
+ 6.4.7. COPY Command ........................................... 59
+ 6.4.8. UID Command ............................................ 60
+ 6.5. Client Commands - Experimental/Expansion ............... 62
+ 6.5.1. X<atom> Command ........................................ 62
+ 7. Server Responses ....................................... 62
+ 7.1. Server Responses - Status Responses .................... 63
+ 7.1.1. OK Response ............................................ 65
+ 7.1.2. NO Response ............................................ 66
+ 7.1.3. BAD Response ........................................... 66
+ 7.1.4. PREAUTH Response ....................................... 67
+ 7.1.5. BYE Response ........................................... 67
+ 7.2. Server Responses - Server and Mailbox Status ........... 68
+ 7.2.1. CAPABILITY Response .................................... 68
+ 7.2.2. LIST Response .......................................... 69
+ 7.2.3. LSUB Response .......................................... 70
+ 7.2.4 STATUS Response ........................................ 70
+ 7.2.5. SEARCH Response ........................................ 71
+ 7.2.6. FLAGS Response ......................................... 71
+ 7.3. Server Responses - Mailbox Size ........................ 71
+ 7.3.1. EXISTS Response ........................................ 71
+ 7.3.2. RECENT Response ........................................ 72
+ 7.4. Server Responses - Message Status ...................... 72
+ 7.4.1. EXPUNGE Response ....................................... 72
+ 7.4.2. FETCH Response ......................................... 73
+ 7.5. Server Responses - Command Continuation Request ........ 79
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 8. Sample IMAP4rev1 connection ............................ 80
+ 9. Formal Syntax .......................................... 81
+ 10. Author's Note .......................................... 92
+ 11. Security Considerations ................................ 92
+ 11.1. STARTTLS Security Considerations ....................... 92
+ 11.2. Other Security Considerations .......................... 93
+ 12. IANA Considerations .................................... 94
+ Appendices ..................................................... 95
+ A. References ............................................. 95
+ B. Changes from RFC 2060 .................................. 97
+ C. Key Word Index ......................................... 103
+ Author's Address ............................................... 107
+ Full Copyright Statement ....................................... 108
+
+IMAP4rev1 Protocol Specification
+
+1. How to Read This Document
+
+1.1. Organization of This Document
+
+ This document is written from the point of view of the implementor of
+ an IMAP4rev1 client or server. Beyond the protocol overview in
+ section 2, it is not optimized for someone trying to understand the
+ operation of the protocol. The material in sections 3 through 5
+ provides the general context and definitions with which IMAP4rev1
+ operates.
+
+ Sections 6, 7, and 9 describe the IMAP commands, responses, and
+ syntax, respectively. The relationships among these are such that it
+ is almost impossible to understand any of them separately. In
+ particular, do not attempt to deduce command syntax from the command
+ section alone; instead refer to the Formal Syntax section.
+
+1.2. Conventions Used in This Document
+
+ "Conventions" are basic principles or procedures. Document
+ conventions are noted in this section.
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+ be interpreted as described in [KEYWORDS].
+
+ The word "can" (not "may") is used to refer to a possible
+ circumstance or situation, as opposed to an optional facility of the
+ protocol.
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ "User" is used to refer to a human user, whereas "client" refers to
+ the software being run by the user.
+
+ "Connection" refers to the entire sequence of client/server
+ interaction from the initial establishment of the network connection
+ until its termination.
+
+ "Session" refers to the sequence of client/server interaction from
+ the time that a mailbox is selected (SELECT or EXAMINE command) until
+ the time that selection ends (SELECT or EXAMINE of another mailbox,
+ CLOSE command, or connection termination).
+
+ Characters are 7-bit US-ASCII unless otherwise specified. Other
+ character sets are indicated using a "CHARSET", as described in
+ [MIME-IMT] and defined in [CHARSET]. CHARSETs have important
+ additional semantics in addition to defining character set; refer to
+ these documents for more detail.
+
+ There are several protocol conventions in IMAP. These refer to
+ aspects of the specification which are not strictly part of the IMAP
+ protocol, but reflect generally-accepted practice. Implementations
+ need to be aware of these conventions, and avoid conflicts whether or
+ not they implement the convention. For example, "&" may not be used
+ as a hierarchy delimiter since it conflicts with the Mailbox
+ International Naming Convention, and other uses of "&" in mailbox
+ names are impacted as well.
+
+1.3. Special Notes to Implementors
+
+ Implementors of the IMAP protocol are strongly encouraged to read the
+ IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
+ conjunction with this document, to help understand the intricacies of
+ this protocol and how best to build an interoperable product.
+
+ IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
+ unpublished IMAP2bis protocols. IMAP4rev1 is largely compatible with
+ the IMAP4 protocol described in RFC 1730; the exception being in
+ certain facilities added in RFC 1730 that proved problematic and were
+ subsequently removed. In the course of the evolution of IMAP4rev1,
+ some aspects in the earlier protocols have become obsolete. Obsolete
+ commands, responses, and data formats which an IMAP4rev1
+ implementation can encounter when used with an earlier implementation
+ are described in [IMAP-OBSOLETE].
+
+ Other compatibility issues with IMAP2bis, the most common variant of
+ the earlier protocol, are discussed in [IMAP-COMPAT]. A full
+ discussion of compatibility issues with rare (and presumed extinct)
+
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
+ primarily of historical interest.
+
+ IMAP was originally developed for the older [RFC-822] standard, and
+ as a consequence several fetch items in IMAP incorporate "RFC822" in
+ their name. With the exception of RFC822.SIZE, there are more modern
+ replacements; for example, the modern version of RFC822.HEADER is
+ BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a
+ reference to the updated [RFC-2822] standard.
+
+2. Protocol Overview
+
+2.1. Link Level
+
+ The IMAP4rev1 protocol assumes a reliable data stream such as that
+ provided by TCP. When TCP is used, an IMAP4rev1 server listens on
+ port 143.
+
+2.2. Commands and Responses
+
+ An IMAP4rev1 connection consists of the establishment of a
+ client/server network connection, an initial greeting from the
+ server, and client/server interactions. These client/server
+ interactions consist of a client command, server data, and a server
+ completion result response.
+
+ All interactions transmitted by client and server are in the form of
+ lines, that is, strings that end with a CRLF. The protocol receiver
+ of an IMAP4rev1 client or server is either reading a line, or is
+ reading a sequence of octets with a known count followed by a line.
+
+2.2.1. Client Protocol Sender and Server Protocol Receiver
+
+ The client command begins an operation. Each client command is
+ prefixed with an identifier (typically a short alphanumeric string,
+ e.g., A0001, A0002, etc.) called a "tag". A different tag is
+ generated by the client for each command.
+
+ Clients MUST follow the syntax outlined in this specification
+ strictly. It is a syntax error to send a command with missing or
+ extraneous spaces or arguments.
+
+ There are two cases in which a line from the client does not
+ represent a complete command. In one case, a command argument is
+ quoted with an octet count (see the description of literal in String
+ under Data Formats); in the other case, the command arguments require
+ server feedback (see the AUTHENTICATE command). In either case, the
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ server sends a command continuation request response if it is ready
+ for the octets (if appropriate) and the remainder of the command.
+ This response is prefixed with the token "+".
+
+ Note: If instead, the server detected an error in the
+ command, it sends a BAD completion response with a tag
+ matching the command (as described below) to reject the
+ command and prevent the client from sending any more of the
+ command.
+
+ It is also possible for the server to send a completion
+ response for some other command (if multiple commands are
+ in progress), or untagged data. In either case, the
+ command continuation request is still pending; the client
+ takes the appropriate action for the response, and reads
+ another response from the server. In all cases, the client
+ MUST send a complete command (including receiving all
+ command continuation request responses and command
+ continuations for the command) before initiating a new
+ command.
+
+ The protocol receiver of an IMAP4rev1 server reads a command line
+ from the client, parses the command and its arguments, and transmits
+ server data and a server command completion result response.
+
+2.2.2. Server Protocol Sender and Client Protocol Receiver
+
+ Data transmitted by the server to the client and status responses
+ that do not indicate command completion are prefixed with the token
+ "*", and are called untagged responses.
+
+ Server data MAY be sent as a result of a client command, or MAY be
+ sent unilaterally by the server. There is no syntactic difference
+ between server data that resulted from a specific command and server
+ data that were sent unilaterally.
+
+ The server completion result response indicates the success or
+ failure of the operation. It is tagged with the same tag as the
+ client command which began the operation. Thus, if more than one
+ command is in progress, the tag in a server completion response
+ identifies the command to which the response applies. There are
+ three possible server completion responses: OK (indicating success),
+ NO (indicating failure), or BAD (indicating a protocol error such as
+ unrecognized command or command syntax error).
+
+ Servers SHOULD enforce the syntax outlined in this specification
+ strictly. Any client command with a protocol syntax error, including
+ (but not limited to) missing or extraneous spaces or arguments,
+
+
+
+Crispin Standards Track [Page 7]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SHOULD be rejected, and the client given a BAD server completion
+ response.
+
+ The protocol receiver of an IMAP4rev1 client reads a response line
+ from the server. It then takes action on the response based upon the
+ first token of the response, which can be a tag, a "*", or a "+".
+
+ A client MUST be prepared to accept any server response at all times.
+ This includes server data that was not requested. Server data SHOULD
+ be recorded, so that the client can reference its recorded copy
+ rather than sending a command to the server to request the data. In
+ the case of certain server data, the data MUST be recorded.
+
+ This topic is discussed in greater detail in the Server Responses
+ section.
+
+2.3. Message Attributes
+
+ In addition to message text, each message has several attributes
+ associated with it. These attributes can be retrieved individually
+ or in conjunction with other attributes or message texts.
+
+2.3.1. Message Numbers
+
+ Messages in IMAP4rev1 are accessed by one of two numbers; the unique
+ identifier or the message sequence number.
+
+
+2.3.1.1. Unique Identifier (UID) Message Attribute
+
+ A 32-bit value assigned to each message, which when used with the
+ unique identifier validity value (see below) forms a 64-bit value
+ that MUST NOT refer to any other message in the mailbox or any
+ subsequent mailbox with the same name forever. Unique identifiers
+ are assigned in a strictly ascending fashion in the mailbox; as each
+ message is added to the mailbox it is assigned a higher UID than the
+ message(s) which were added previously. Unlike message sequence
+ numbers, unique identifiers are not necessarily contiguous.
+
+ The unique identifier of a message MUST NOT change during the
+ session, and SHOULD NOT change between sessions. Any change of
+ unique identifiers between sessions MUST be detectable using the
+ UIDVALIDITY mechanism discussed below. Persistent unique identifiers
+ are required for a client to resynchronize its state from a previous
+ session with the server (e.g., disconnected or offline access
+ clients); this is discussed further in [IMAP-DISC].
+
+
+
+
+
+Crispin Standards Track [Page 8]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Associated with every mailbox are two values which aid in unique
+ identifier handling: the next unique identifier value and the unique
+ identifier validity value.
+
+ The next unique identifier value is the predicted value that will be
+ assigned to a new message in the mailbox. Unless the unique
+ identifier validity also changes (see below), the next unique
+ identifier value MUST have the following two characteristics. First,
+ the next unique identifier value MUST NOT change unless new messages
+ are added to the mailbox; and second, the next unique identifier
+ value MUST change whenever new messages are added to the mailbox,
+ even if those new messages are subsequently expunged.
+
+ Note: The next unique identifier value is intended to
+ provide a means for a client to determine whether any
+ messages have been delivered to the mailbox since the
+ previous time it checked this value. It is not intended to
+ provide any guarantee that any message will have this
+ unique identifier. A client can only assume, at the time
+ that it obtains the next unique identifier value, that
+ messages arriving after that time will have a UID greater
+ than or equal to that value.
+
+ The unique identifier validity value is sent in a UIDVALIDITY
+ response code in an OK untagged response at mailbox selection time.
+ If unique identifiers from an earlier session fail to persist in this
+ session, the unique identifier validity value MUST be greater than
+ the one used in the earlier session.
+
+ Note: Ideally, unique identifiers SHOULD persist at all
+ times. Although this specification recognizes that failure
+ to persist can be unavoidable in certain server
+ environments, it STRONGLY ENCOURAGES message store
+ implementation techniques that avoid this problem. For
+ example:
+
+ 1) Unique identifiers MUST be strictly ascending in the
+ mailbox at all times. If the physical message store is
+ re-ordered by a non-IMAP agent, this requires that the
+ unique identifiers in the mailbox be regenerated, since
+ the former unique identifiers are no longer strictly
+ ascending as a result of the re-ordering.
+
+ 2) If the message store has no mechanism to store unique
+ identifiers, it must regenerate unique identifiers at
+ each session, and each session must have a unique
+ UIDVALIDITY value.
+
+
+
+
+Crispin Standards Track [Page 9]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 3) If the mailbox is deleted and a new mailbox with the
+ same name is created at a later date, the server must
+ either keep track of unique identifiers from the
+ previous instance of the mailbox, or it must assign a
+ new UIDVALIDITY value to the new instance of the
+ mailbox. A good UIDVALIDITY value to use in this case
+ is a 32-bit representation of the creation date/time of
+ the mailbox. It is alright to use a constant such as
+ 1, but only if it guaranteed that unique identifiers
+ will never be reused, even in the case of a mailbox
+ being deleted (or renamed) and a new mailbox by the
+ same name created at some future time.
+
+ 4) The combination of mailbox name, UIDVALIDITY, and UID
+ must refer to a single immutable message on that server
+ forever. In particular, the internal date, [RFC-2822]
+ size, envelope, body structure, and message texts
+ (RFC822, RFC822.HEADER, RFC822.TEXT, and all BODY[...]
+ fetch data items) must never change. This does not
+ include message numbers, nor does it include attributes
+ that can be set by a STORE command (e.g., FLAGS).
+
+
+2.3.1.2. Message Sequence Number Message Attribute
+
+ A relative position from 1 to the number of messages in the mailbox.
+ This position MUST be ordered by ascending unique identifier. As
+ each new message is added, it is assigned a message sequence number
+ that is 1 higher than the number of messages in the mailbox before
+ that new message was added.
+
+ Message sequence numbers can be reassigned during the session. For
+ example, when a message is permanently removed (expunged) from the
+ mailbox, the message sequence number for all subsequent messages is
+ decremented. The number of messages in the mailbox is also
+ decremented. Similarly, a new message can be assigned a message
+ sequence number that was once held by some other message prior to an
+ expunge.
+
+ In addition to accessing messages by relative position in the
+ mailbox, message sequence numbers can be used in mathematical
+ calculations. For example, if an untagged "11 EXISTS" is received,
+ and previously an untagged "8 EXISTS" was received, three new
+ messages have arrived with message sequence numbers of 9, 10, and 11.
+ Another example, if message 287 in a 523 message mailbox has UID
+ 12345, there are exactly 286 messages which have lesser UIDs and 236
+ messages which have greater UIDs.
+
+
+
+
+Crispin Standards Track [Page 10]
+
+RFC 3501 IMAPv4 March 2003
+
+
+2.3.2. Flags Message Attribute
+
+ A list of zero or more named tokens associated with the message. A
+ flag is set by its addition to this list, and is cleared by its
+ removal. There are two types of flags in IMAP4rev1. A flag of
+ either type can be permanent or session-only.
+
+ A system flag is a flag name that is pre-defined in this
+ specification. All system flags begin with "\". Certain system
+ flags (\Deleted and \Seen) have special semantics described
+ elsewhere. The currently-defined system flags are:
+
+ \Seen
+ Message has been read
+
+ \Answered
+ Message has been answered
+
+ \Flagged
+ Message is "flagged" for urgent/special attention
+
+ \Deleted
+ Message is "deleted" for removal by later EXPUNGE
+
+ \Draft
+ Message has not completed composition (marked as a draft).
+
+ \Recent
+ Message is "recently" arrived in this mailbox. This session
+ is the first session to have been notified about this
+ message; if the session is read-write, subsequent sessions
+ will not see \Recent set for this message. This flag can not
+ be altered by the client.
+
+ If it is not possible to determine whether or not this
+ session is the first session to be notified about a message,
+ then that message SHOULD be considered recent.
+
+ If multiple connections have the same mailbox selected
+ simultaneously, it is undefined which of these connections
+ will see newly-arrived messages with \Recent set and which
+ will see it without \Recent set.
+
+ A keyword is defined by the server implementation. Keywords do not
+ begin with "\". Servers MAY permit the client to define new keywords
+ in the mailbox (see the description of the PERMANENTFLAGS response
+ code for more information).
+
+
+
+
+Crispin Standards Track [Page 11]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A flag can be permanent or session-only on a per-flag basis.
+ Permanent flags are those which the client can add or remove from the
+ message flags permanently; that is, concurrent and subsequent
+ sessions will see any change in permanent flags. Changes to session
+ flags are valid only in that session.
+
+ Note: The \Recent system flag is a special case of a
+ session flag. \Recent can not be used as an argument in a
+ STORE or APPEND command, and thus can not be changed at
+ all.
+
+2.3.3. Internal Date Message Attribute
+
+ The internal date and time of the message on the server. This
+ is not the date and time in the [RFC-2822] header, but rather a
+ date and time which reflects when the message was received. In
+ the case of messages delivered via [SMTP], this SHOULD be the
+ date and time of final delivery of the message as defined by
+ [SMTP]. In the case of messages delivered by the IMAP4rev1 COPY
+ command, this SHOULD be the internal date and time of the source
+ message. In the case of messages delivered by the IMAP4rev1
+ APPEND command, this SHOULD be the date and time as specified in
+ the APPEND command description. All other cases are
+ implementation defined.
+
+2.3.4. [RFC-2822] Size Message Attribute
+
+ The number of octets in the message, as expressed in [RFC-2822]
+ format.
+
+2.3.5. Envelope Structure Message Attribute
+
+ A parsed representation of the [RFC-2822] header of the message.
+ Note that the IMAP Envelope structure is not the same as an
+ [SMTP] envelope.
+
+2.3.6. Body Structure Message Attribute
+
+ A parsed representation of the [MIME-IMB] body structure
+ information of the message.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 12]
+
+RFC 3501 IMAPv4 March 2003
+
+
+2.4. Message Texts
+
+ In addition to being able to fetch the full [RFC-2822] text of a
+ message, IMAP4rev1 permits the fetching of portions of the full
+ message text. Specifically, it is possible to fetch the
+ [RFC-2822] message header, [RFC-2822] message body, a [MIME-IMB]
+ body part, or a [MIME-IMB] header.
+
+3. State and Flow Diagram
+
+ Once the connection between client and server is established, an
+ IMAP4rev1 connection is in one of four states. The initial
+ state is identified in the server greeting. Most commands are
+ only valid in certain states. It is a protocol error for the
+ client to attempt a command while the connection is in an
+ inappropriate state, and the server will respond with a BAD or
+ NO (depending upon server implementation) command completion
+ result.
+
+3.1. Not Authenticated State
+
+ In the not authenticated state, the client MUST supply
+ authentication credentials before most commands will be
+ permitted. This state is entered when a connection starts
+ unless the connection has been pre-authenticated.
+
+3.2. Authenticated State
+
+ In the authenticated state, the client is authenticated and MUST
+ select a mailbox to access before commands that affect messages
+ will be permitted. This state is entered when a
+ pre-authenticated connection starts, when acceptable
+ authentication credentials have been provided, after an error in
+ selecting a mailbox, or after a successful CLOSE command.
+
+3.3. Selected State
+
+ In a selected state, a mailbox has been selected to access.
+ This state is entered when a mailbox has been successfully
+ selected.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 13]
+
+RFC 3501 IMAPv4 March 2003
+
+
+3.4. Logout State
+
+ In the logout state, the connection is being terminated. This
+ state can be entered as a result of a client request (via the
+ LOGOUT command) or by unilateral action on the part of either
+ the client or server.
+
+ If the client requests the logout state, the server MUST send an
+ untagged BYE response and a tagged OK response to the LOGOUT
+ command before the server closes the connection; and the client
+ MUST read the tagged OK response to the LOGOUT command before
+ the client closes the connection.
+
+ A server MUST NOT unilaterally close the connection without
+ sending an untagged BYE response that contains the reason for
+ having done so. A client SHOULD NOT unilaterally close the
+ connection, and instead SHOULD issue a LOGOUT command. If the
+ server detects that the client has unilaterally closed the
+ connection, the server MAY omit the untagged BYE response and
+ simply close its connection.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 14]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ +----------------------+
+ |connection established|
+ +----------------------+
+ ||
+ \/
+ +--------------------------------------+
+ | server greeting |
+ +--------------------------------------+
+ || (1) || (2) || (3)
+ \/ || ||
+ +-----------------+ || ||
+ |Not Authenticated| || ||
+ +-----------------+ || ||
+ || (7) || (4) || ||
+ || \/ \/ ||
+ || +----------------+ ||
+ || | Authenticated |<=++ ||
+ || +----------------+ || ||
+ || || (7) || (5) || (6) ||
+ || || \/ || ||
+ || || +--------+ || ||
+ || || |Selected|==++ ||
+ || || +--------+ ||
+ || || || (7) ||
+ \/ \/ \/ \/
+ +--------------------------------------+
+ | Logout |
+ +--------------------------------------+
+ ||
+ \/
+ +-------------------------------+
+ |both sides close the connection|
+ +-------------------------------+
+
+ (1) connection without pre-authentication (OK greeting)
+ (2) pre-authenticated connection (PREAUTH greeting)
+ (3) rejected connection (BYE greeting)
+ (4) successful LOGIN or AUTHENTICATE command
+ (5) successful SELECT or EXAMINE command
+ (6) CLOSE command, or failed SELECT or EXAMINE command
+ (7) LOGOUT command, server shutdown, or connection closed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 15]
+
+RFC 3501 IMAPv4 March 2003
+
+
+4. Data Formats
+
+ IMAP4rev1 uses textual commands and responses. Data in
+ IMAP4rev1 can be in one of several forms: atom, number, string,
+ parenthesized list, or NIL. Note that a particular data item
+ may take more than one form; for example, a data item defined as
+ using "astring" syntax may be either an atom or a string.
+
+4.1. Atom
+
+ An atom consists of one or more non-special characters.
+
+4.2. Number
+
+ A number consists of one or more digit characters, and
+ represents a numeric value.
+
+4.3. String
+
+ A string is in one of two forms: either literal or quoted
+ string. The literal form is the general form of string. The
+ quoted string form is an alternative that avoids the overhead of
+ processing a literal at the cost of limitations of characters
+ which may be used.
+
+ A literal is a sequence of zero or more octets (including CR and
+ LF), prefix-quoted with an octet count in the form of an open
+ brace ("{"), the number of octets, close brace ("}"), and CRLF.
+ In the case of literals transmitted from server to client, the
+ CRLF is immediately followed by the octet data. In the case of
+ literals transmitted from client to server, the client MUST wait
+ to receive a command continuation request (described later in
+ this document) before sending the octet data (and the remainder
+ of the command).
+
+ A quoted string is a sequence of zero or more 7-bit characters,
+ excluding CR and LF, with double quote (<">) characters at each
+ end.
+
+ The empty string is represented as either "" (a quoted string
+ with zero characters between double quotes) or as {0} followed
+ by CRLF (a literal with an octet count of 0).
+
+ Note: Even if the octet count is 0, a client transmitting a
+ literal MUST wait to receive a command continuation request.
+
+
+
+
+
+
+Crispin Standards Track [Page 16]
+
+RFC 3501 IMAPv4 March 2003
+
+
+4.3.1. 8-bit and Binary Strings
+
+ 8-bit textual and binary mail is supported through the use of a
+ [MIME-IMB] content transfer encoding. IMAP4rev1 implementations MAY
+ transmit 8-bit or multi-octet characters in literals, but SHOULD do
+ so only when the [CHARSET] is identified.
+
+ Although a BINARY body encoding is defined, unencoded binary strings
+ are not permitted. A "binary string" is any string with NUL
+ characters. Implementations MUST encode binary data into a textual
+ form, such as BASE64, before transmitting the data. A string with an
+ excessive amount of CTL characters MAY also be considered to be
+ binary.
+
+4.4. Parenthesized List
+
+ Data structures are represented as a "parenthesized list"; a sequence
+ of data items, delimited by space, and bounded at each end by
+ parentheses. A parenthesized list can contain other parenthesized
+ lists, using multiple levels of parentheses to indicate nesting.
+
+ The empty list is represented as () -- a parenthesized list with no
+ members.
+
+4.5. NIL
+
+ The special form "NIL" represents the non-existence of a particular
+ data item that is represented as a string or parenthesized list, as
+ distinct from the empty string "" or the empty parenthesized list ().
+
+ Note: NIL is never used for any data item which takes the
+ form of an atom. For example, a mailbox name of "NIL" is a
+ mailbox named NIL as opposed to a non-existent mailbox
+ name. This is because mailbox uses "astring" syntax which
+ is an atom or a string. Conversely, an addr-name of NIL is
+ a non-existent personal name, because addr-name uses
+ "nstring" syntax which is NIL or a string, but never an
+ atom.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 17]
+
+RFC 3501 IMAPv4 March 2003
+
+
+5. Operational Considerations
+
+ The following rules are listed here to ensure that all IMAP4rev1
+ implementations interoperate properly.
+
+5.1. Mailbox Naming
+
+ Mailbox names are 7-bit. Client implementations MUST NOT attempt to
+ create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
+ names returned by LIST or LSUB as UTF-8. Server implementations
+ SHOULD prohibit the creation of 8-bit mailbox names, and SHOULD NOT
+ return 8-bit mailbox names in LIST or LSUB. See section 5.1.3 for
+ more information on how to represent non-ASCII mailbox names.
+
+ Note: 8-bit mailbox names were undefined in earlier
+ versions of this protocol. Some sites used a local 8-bit
+ character set to represent non-ASCII mailbox names. Such
+ usage is not interoperable, and is now formally deprecated.
+
+ The case-insensitive mailbox name INBOX is a special name reserved to
+ mean "the primary mailbox for this user on this server". The
+ interpretation of all other names is implementation-dependent.
+
+ In particular, this specification takes no position on case
+ sensitivity in non-INBOX mailbox names. Some server implementations
+ are fully case-sensitive; others preserve case of a newly-created
+ name but otherwise are case-insensitive; and yet others coerce names
+ to a particular case. Client implementations MUST interact with any
+ of these. If a server implementation interprets non-INBOX mailbox
+ names as case-insensitive, it MUST treat names using the
+ international naming convention specially as described in section
+ 5.1.3.
+
+ There are certain client considerations when creating a new mailbox
+ name:
+
+ 1) Any character which is one of the atom-specials (see the Formal
+ Syntax) will require that the mailbox name be represented as a
+ quoted string or literal.
+
+ 2) CTL and other non-graphic characters are difficult to represent
+ in a user interface and are best avoided.
+
+ 3) Although the list-wildcard characters ("%" and "*") are valid
+ in a mailbox name, it is difficult to use such mailbox names
+ with the LIST and LSUB commands due to the conflict with
+ wildcard interpretation.
+
+
+
+
+Crispin Standards Track [Page 18]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 4) Usually, a character (determined by the server implementation)
+ is reserved to delimit levels of hierarchy.
+
+ 5) Two characters, "#" and "&", have meanings by convention, and
+ should be avoided except when used in that convention.
+
+5.1.1. Mailbox Hierarchy Naming
+
+ If it is desired to export hierarchical mailbox names, mailbox names
+ MUST be left-to-right hierarchical using a single character to
+ separate levels of hierarchy. The same hierarchy separator character
+ is used for all levels of hierarchy within a single name.
+
+5.1.2. Mailbox Namespace Naming Convention
+
+ By convention, the first hierarchical element of any mailbox name
+ which begins with "#" identifies the "namespace" of the remainder of
+ the name. This makes it possible to disambiguate between different
+ types of mailbox stores, each of which have their own namespaces.
+
+ For example, implementations which offer access to USENET
+ newsgroups MAY use the "#news" namespace to partition the
+ USENET newsgroup namespace from that of other mailboxes.
+ Thus, the comp.mail.misc newsgroup would have a mailbox
+ name of "#news.comp.mail.misc", and the name
+ "comp.mail.misc" can refer to a different object (e.g., a
+ user's private mailbox).
+
+5.1.3. Mailbox International Naming Convention
+
+ By convention, international mailbox names in IMAP4rev1 are specified
+ using a modified version of the UTF-7 encoding described in [UTF-7].
+ Modified UTF-7 may also be usable in servers that implement an
+ earlier version of this protocol.
+
+ In modified UTF-7, printable US-ASCII characters, except for "&",
+ represent themselves; that is, characters with octet values 0x20-0x25
+ and 0x27-0x7e. The character "&" (0x26) is represented by the
+ two-octet sequence "&-".
+
+ All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
+ represented in modified BASE64, with a further modification from
+ [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be
+ used to represent any printing US-ASCII character which can represent
+ itself.
+
+
+
+
+
+
+Crispin Standards Track [Page 19]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ "&" is used to shift to modified BASE64 and "-" to shift back to
+ US-ASCII. There is no implicit shift from BASE64 to US-ASCII, and
+ null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
+ means "&") are not permitted. However, all names start in US-ASCII,
+ and MUST end in US-ASCII; that is, a name that ends with a non-ASCII
+ ISO-10646 character MUST end with a "-").
+
+ The purpose of these modifications is to correct the following
+ problems with UTF-7:
+
+ 1) UTF-7 uses the "+" character for shifting; this conflicts with
+ the common use of "+" in mailbox names, in particular USENET
+ newsgroup names.
+
+ 2) UTF-7's encoding is BASE64 which uses the "/" character; this
+ conflicts with the use of "/" as a popular hierarchy delimiter.
+
+ 3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
+ the use of "\" as a popular hierarchy delimiter.
+
+ 4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
+ the use of "~" in some servers as a home directory indicator.
+
+ 5) UTF-7 permits multiple alternate forms to represent the same
+ string; in particular, printable US-ASCII characters can be
+ represented in encoded form.
+
+ Although modified UTF-7 is a convention, it establishes certain
+ requirements on server handling of any mailbox name with an
+ embedded "&" character. In particular, server implementations
+ MUST preserve the exact form of the modified BASE64 portion of a
+ modified UTF-7 name and treat that text as case-sensitive, even if
+ names are otherwise case-insensitive or case-folded.
+
+ Server implementations SHOULD verify that any mailbox name with an
+ embedded "&" character, used as an argument to CREATE, is: in the
+ correctly modified UTF-7 syntax, has no superfluous shifts, and
+ has no encoding in modified BASE64 of any printing US-ASCII
+ character which can represent itself. However, client
+ implementations MUST NOT depend upon the server doing this, and
+ SHOULD NOT attempt to create a mailbox name with an embedded "&"
+ character unless it complies with the modified UTF-7 syntax.
+
+ Server implementations which export a mail store that does not
+ follow the modified UTF-7 convention MUST convert to modified
+ UTF-7 any mailbox name that contains either non-ASCII characters
+ or the "&" character.
+
+
+
+
+Crispin Standards Track [Page 20]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, here is a mailbox name which mixes English,
+ Chinese, and Japanese text:
+ ~peter/mail/&U,BTFw-/&ZeVnLIqe-
+
+ For example, the string "&Jjo!" is not a valid mailbox
+ name because it does not contain a shift to US-ASCII
+ before the "!". The correct form is "&Jjo-!". The
+ string "&U,BTFw-&ZeVnLIqe-" is not permitted because it
+ contains a superfluous shift. The correct form is
+ "&U,BTF2XlZyyKng-".
+
+5.2. Mailbox Size and Message Status Updates
+
+ At any time, a server can send data that the client did not request.
+ Sometimes, such behavior is REQUIRED. For example, agents other than
+ the server MAY add messages to the mailbox (e.g., new message
+ delivery), change the flags of the messages in the mailbox (e.g.,
+ simultaneous access to the same mailbox by multiple agents), or even
+ remove messages from the mailbox. A server MUST send mailbox size
+ updates automatically if a mailbox size change is observed during the
+ processing of a command. A server SHOULD send message flag updates
+ automatically, without requiring the client to request such updates
+ explicitly.
+
+ Special rules exist for server notification of a client about the
+ removal of messages to prevent synchronization errors; see the
+ description of the EXPUNGE response for more detail. In particular,
+ it is NOT permitted to send an EXISTS response that would reduce the
+ number of messages in the mailbox; only the EXPUNGE response can do
+ this.
+
+ Regardless of what implementation decisions a client makes on
+ remembering data from the server, a client implementation MUST record
+ mailbox size updates. It MUST NOT assume that any command after the
+ initial mailbox selection will return the size of the mailbox.
+
+5.3. Response when no Command in Progress
+
+ Server implementations are permitted to send an untagged response
+ (except for EXPUNGE) while there is no command in progress. Server
+ implementations that send such responses MUST deal with flow control
+ considerations. Specifically, they MUST either (1) verify that the
+ size of the data does not exceed the underlying transport's available
+ window size, or (2) use non-blocking writes.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 21]
+
+RFC 3501 IMAPv4 March 2003
+
+
+5.4. Autologout Timer
+
+ If a server has an inactivity autologout timer, the duration of that
+ timer MUST be at least 30 minutes. The receipt of ANY command from
+ the client during that interval SHOULD suffice to reset the
+ autologout timer.
+
+5.5. Multiple Commands in Progress
+
+ The client MAY send another command without waiting for the
+ completion result response of a command, subject to ambiguity rules
+ (see below) and flow control constraints on the underlying data
+ stream. Similarly, a server MAY begin processing another command
+ before processing the current command to completion, subject to
+ ambiguity rules. However, any command continuation request responses
+ and command continuations MUST be negotiated before any subsequent
+ command is initiated.
+
+ The exception is if an ambiguity would result because of a command
+ that would affect the results of other commands. Clients MUST NOT
+ send multiple commands without waiting if an ambiguity would result.
+ If the server detects a possible ambiguity, it MUST execute commands
+ to completion in the order given by the client.
+
+ The most obvious example of ambiguity is when a command would affect
+ the results of another command, e.g., a FETCH of a message's flags
+ and a STORE of that same message's flags.
+
+ A non-obvious ambiguity occurs with commands that permit an untagged
+ EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
+ since an untagged EXPUNGE response can invalidate sequence numbers in
+ a subsequent command. This is not a problem for FETCH, STORE, or
+ SEARCH commands because servers are prohibited from sending EXPUNGE
+ responses while any of those commands are in progress. Therefore, if
+ the client sends any command other than FETCH, STORE, or SEARCH, it
+ MUST wait for the completion result response before sending a command
+ with message sequence numbers.
+
+ Note: UID FETCH, UID STORE, and UID SEARCH are different
+ commands from FETCH, STORE, and SEARCH. If the client
+ sends a UID command, it must wait for a completion result
+ response before sending a command with message sequence
+ numbers.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 22]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, the following non-waiting command sequences are invalid:
+
+ FETCH + NOOP + STORE
+ STORE + COPY + FETCH
+ COPY + COPY
+ CHECK + FETCH
+
+ The following are examples of valid non-waiting command sequences:
+
+ FETCH + STORE + SEARCH + CHECK
+ STORE + COPY + EXPUNGE
+
+ UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting
+ command sequence, depending upon whether or not the second UID
+ SEARCH contains message sequence numbers.
+
+6. Client Commands
+
+ IMAP4rev1 commands are described in this section. Commands are
+ organized by the state in which the command is permitted. Commands
+ which are permitted in multiple states are listed in the minimum
+ permitted state (for example, commands valid in authenticated and
+ selected state are listed in the authenticated state commands).
+
+ Command arguments, identified by "Arguments:" in the command
+ descriptions below, are described by function, not by syntax. The
+ precise syntax of command arguments is described in the Formal Syntax
+ section.
+
+ Some commands cause specific server responses to be returned; these
+ are identified by "Responses:" in the command descriptions below.
+ See the response descriptions in the Responses section for
+ information on these responses, and the Formal Syntax section for the
+ precise syntax of these responses. It is possible for server data to
+ be transmitted as a result of any command. Thus, commands that do
+ not specifically require server data specify "no specific responses
+ for this command" instead of "none".
+
+ The "Result:" in the command description refers to the possible
+ tagged status responses to a command, and any special interpretation
+ of these status responses.
+
+ The state of a connection is only changed by successful commands
+ which are documented as changing state. A rejected command (BAD
+ response) never changes the state of the connection or of the
+ selected mailbox. A failed command (NO response) generally does not
+ change the state of the connection or of the selected mailbox; the
+ exception being the SELECT and EXAMINE commands.
+
+
+
+Crispin Standards Track [Page 23]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.1. Client Commands - Any State
+
+ The following commands are valid in any state: CAPABILITY, NOOP, and
+ LOGOUT.
+
+6.1.1. CAPABILITY Command
+
+ Arguments: none
+
+ Responses: REQUIRED untagged response: CAPABILITY
+
+ Result: OK - capability completed
+ BAD - command unknown or arguments invalid
+
+ The CAPABILITY command requests a listing of capabilities that the
+ server supports. The server MUST send a single untagged
+ CAPABILITY response with "IMAP4rev1" as one of the listed
+ capabilities before the (tagged) OK response.
+
+ A capability name which begins with "AUTH=" indicates that the
+ server supports that particular authentication mechanism. All
+ such names are, by definition, part of this specification. For
+ example, the authorization capability for an experimental
+ "blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
+ "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
+
+ Other capability names refer to extensions, revisions, or
+ amendments to this specification. See the documentation of the
+ CAPABILITY response for additional information. No capabilities,
+ beyond the base IMAP4rev1 set defined in this specification, are
+ enabled without explicit client action to invoke the capability.
+
+ Client and server implementations MUST implement the STARTTLS,
+ LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+ capabilities. See the Security Considerations section for
+ important information.
+
+ See the section entitled "Client Commands -
+ Experimental/Expansion" for information about the form of site or
+ implementation-specific capabilities.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 24]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: abcd CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
+ LOGINDISABLED
+ S: abcd OK CAPABILITY completed
+ C: efgh STARTTLS
+ S: efgh OK STARTLS completed
+ <TLS negotiation, further commands are under [TLS] layer>
+ C: ijkl CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
+ S: ijkl OK CAPABILITY completed
+
+
+6.1.2. NOOP Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command (but see below)
+
+ Result: OK - noop completed
+ BAD - command unknown or arguments invalid
+
+ The NOOP command always succeeds. It does nothing.
+
+ Since any command can return a status update as untagged data, the
+ NOOP command can be used as a periodic poll for new messages or
+ message status updates during a period of inactivity (this is the
+ preferred method to do this). The NOOP command can also be used
+ to reset any inactivity autologout timer on the server.
+
+ Example: C: a002 NOOP
+ S: a002 OK NOOP completed
+ . . .
+ C: a047 NOOP
+ S: * 22 EXPUNGE
+ S: * 23 EXISTS
+ S: * 3 RECENT
+ S: * 14 FETCH (FLAGS (\Seen \Deleted))
+ S: a047 OK NOOP completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 25]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.1.3. LOGOUT Command
+
+ Arguments: none
+
+ Responses: REQUIRED untagged response: BYE
+
+ Result: OK - logout completed
+ BAD - command unknown or arguments invalid
+
+ The LOGOUT command informs the server that the client is done with
+ the connection. The server MUST send a BYE untagged response
+ before the (tagged) OK response, and then close the network
+ connection.
+
+ Example: C: A023 LOGOUT
+ S: * BYE IMAP4rev1 Server logging out
+ S: A023 OK LOGOUT completed
+ (Server and client then close the connection)
+
+6.2. Client Commands - Not Authenticated State
+
+ In the not authenticated state, the AUTHENTICATE or LOGIN command
+ establishes authentication and enters the authenticated state. The
+ AUTHENTICATE command provides a general mechanism for a variety of
+ authentication techniques, privacy protection, and integrity
+ checking; whereas the LOGIN command uses a traditional user name and
+ plaintext password pair and has no means of establishing privacy
+ protection or integrity checking.
+
+ The STARTTLS command is an alternate form of establishing session
+ privacy protection and integrity checking, but does not establish
+ authentication or enter the authenticated state.
+
+ Server implementations MAY allow access to certain mailboxes without
+ establishing authentication. This can be done by means of the
+ ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older
+ convention is a LOGIN command using the userid "anonymous"; in this
+ case, a password is required although the server may choose to accept
+ any password. The restrictions placed on anonymous users are
+ implementation-dependent.
+
+ Once authenticated (including as anonymous), it is not possible to
+ re-enter not authenticated state.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 26]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ the following commands are valid in the not authenticated state:
+ STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations
+ section for important information about these commands.
+
+6.2.1. STARTTLS Command
+
+ Arguments: none
+
+ Responses: no specific response for this command
+
+ Result: OK - starttls completed, begin TLS negotiation
+ BAD - command unknown or arguments invalid
+
+ A [TLS] negotiation begins immediately after the CRLF at the end
+ of the tagged OK response from the server. Once a client issues a
+ STARTTLS command, it MUST NOT issue further commands until a
+ server response is seen and the [TLS] negotiation is complete.
+
+ The server remains in the non-authenticated state, even if client
+ credentials are supplied during the [TLS] negotiation. This does
+ not preclude an authentication mechanism such as EXTERNAL (defined
+ in [SASL]) from using client identity determined by the [TLS]
+ negotiation.
+
+ Once [TLS] has been started, the client MUST discard cached
+ information about server capabilities and SHOULD re-issue the
+ CAPABILITY command. This is necessary to protect against man-in-
+ the-middle attacks which alter the capabilities list prior to
+ STARTTLS. The server MAY advertise different capabilities after
+ STARTTLS.
+
+ Example: C: a001 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
+ S: a001 OK CAPABILITY completed
+ C: a002 STARTTLS
+ S: a002 OK Begin TLS negotiation now
+ <TLS negotiation, further commands are under [TLS] layer>
+ C: a003 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
+ S: a003 OK CAPABILITY completed
+ C: a004 LOGIN joe password
+ S: a004 OK LOGIN completed
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 27]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.2.2. AUTHENTICATE Command
+
+ Arguments: authentication mechanism name
+
+ Responses: continuation data can be requested
+
+ Result: OK - authenticate completed, now in authenticated state
+ NO - authenticate failure: unsupported authentication
+ mechanism, credentials rejected
+ BAD - command unknown or arguments invalid,
+ authentication exchange cancelled
+
+ The AUTHENTICATE command indicates a [SASL] authentication
+ mechanism to the server. If the server supports the requested
+ authentication mechanism, it performs an authentication protocol
+ exchange to authenticate and identify the client. It MAY also
+ negotiate an OPTIONAL security layer for subsequent protocol
+ interactions. If the requested authentication mechanism is not
+ supported, the server SHOULD reject the AUTHENTICATE command by
+ sending a tagged NO response.
+
+ The AUTHENTICATE command does not support the optional "initial
+ response" feature of [SASL]. Section 5.1 of [SASL] specifies how
+ to handle an authentication mechanism which uses an initial
+ response.
+
+ The service name specified by this protocol's profile of [SASL] is
+ "imap".
+
+ The authentication protocol exchange consists of a series of
+ server challenges and client responses that are specific to the
+ authentication mechanism. A server challenge consists of a
+ command continuation request response with the "+" token followed
+ by a BASE64 encoded string. The client response consists of a
+ single line consisting of a BASE64 encoded string. If the client
+ wishes to cancel an authentication exchange, it issues a line
+ consisting of a single "*". If the server receives such a
+ response, it MUST reject the AUTHENTICATE command by sending a
+ tagged BAD response.
+
+ If a security layer is negotiated through the [SASL]
+ authentication exchange, it takes effect immediately following the
+ CRLF that concludes the authentication exchange for the client,
+ and the CRLF of the tagged OK response for the server.
+
+ While client and server implementations MUST implement the
+ AUTHENTICATE command itself, it is not required to implement any
+ authentication mechanisms other than the PLAIN mechanism described
+
+
+
+Crispin Standards Track [Page 28]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ in [IMAP-TLS]. Also, an authentication mechanism is not required
+ to support any security layers.
+
+ Note: a server implementation MUST implement a
+ configuration in which it does NOT permit any plaintext
+ password mechanisms, unless either the STARTTLS command
+ has been negotiated or some other mechanism that
+ protects the session from password snooping has been
+ provided. Server sites SHOULD NOT use any configuration
+ which permits a plaintext password mechanism without
+ such a protection mechanism against password snooping.
+ Client and server implementations SHOULD implement
+ additional [SASL] mechanisms that do not use plaintext
+ passwords, such the GSSAPI mechanism described in [SASL]
+ and/or the [DIGEST-MD5] mechanism.
+
+ Servers and clients can support multiple authentication
+ mechanisms. The server SHOULD list its supported authentication
+ mechanisms in the response to the CAPABILITY command so that the
+ client knows which authentication mechanisms to use.
+
+ A server MAY include a CAPABILITY response code in the tagged OK
+ response of a successful AUTHENTICATE command in order to send
+ capabilities automatically. It is unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes these
+ automatic capabilities. This should only be done if a security
+ layer was not negotiated by the AUTHENTICATE command, because the
+ tagged OK response as part of an AUTHENTICATE command is not
+ protected by encryption/integrity checking. [SASL] requires the
+ client to re-issue a CAPABILITY command in this case.
+
+ If an AUTHENTICATE command fails with a NO response, the client
+ MAY try another authentication mechanism by issuing another
+ AUTHENTICATE command. It MAY also attempt to authenticate by
+ using the LOGIN command (see section 6.2.3 for more detail). In
+ other words, the client MAY request authentication types in
+ decreasing order of preference, with the LOGIN command as a last
+ resort.
+
+ The authorization identity passed from the client to the server
+ during the authentication exchange is interpreted by the server as
+ the user name whose privileges the client is requesting.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 29]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: S: * OK IMAP4rev1 Server
+ C: A001 AUTHENTICATE GSSAPI
+ S: +
+ C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
+ MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
+ b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
+ Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
+ cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
+ AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
+ C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
+ I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
+ vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
+ pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
+ FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
+ NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
+ O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
+ vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
+ S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
+ AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
+ uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
+ C:
+ S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
+ ceP2CWY0SR0fAQAgAAQEBAQ=
+ C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
+ wkhbfa2QteAQAgAG1yYwE=
+ S: A001 OK GSSAPI authentication successful
+
+ Note: The line breaks within server challenges and client
+ responses are for editorial clarity and are not in real
+ authenticators.
+
+
+6.2.3. LOGIN Command
+
+ Arguments: user name
+ password
+
+ Responses: no specific responses for this command
+
+ Result: OK - login completed, now in authenticated state
+ NO - login failure: user name or password rejected
+ BAD - command unknown or arguments invalid
+
+ The LOGIN command identifies the client to the server and carries
+ the plaintext password authenticating this user.
+
+
+
+
+
+
+Crispin Standards Track [Page 30]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A server MAY include a CAPABILITY response code in the tagged OK
+ response to a successful LOGIN command in order to send
+ capabilities automatically. It is unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes these
+ automatic capabilities.
+
+ Example: C: a001 LOGIN SMITH SESAME
+ S: a001 OK LOGIN completed
+
+ Note: Use of the LOGIN command over an insecure network
+ (such as the Internet) is a security risk, because anyone
+ monitoring network traffic can obtain plaintext passwords.
+ The LOGIN command SHOULD NOT be used except as a last
+ resort, and it is recommended that client implementations
+ have a means to disable any automatic use of the LOGIN
+ command.
+
+ Unless either the STARTTLS command has been negotiated or
+ some other mechanism that protects the session from
+ password snooping has been provided, a server
+ implementation MUST implement a configuration in which it
+ advertises the LOGINDISABLED capability and does NOT permit
+ the LOGIN command. Server sites SHOULD NOT use any
+ configuration which permits the LOGIN command without such
+ a protection mechanism against password snooping. A client
+ implementation MUST NOT send a LOGIN command if the
+ LOGINDISABLED capability is advertised.
+
+6.3. Client Commands - Authenticated State
+
+ In the authenticated state, commands that manipulate mailboxes as
+ atomic entities are permitted. Of these commands, the SELECT and
+ EXAMINE commands will select a mailbox for access and enter the
+ selected state.
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ the following commands are valid in the authenticated state: SELECT,
+ EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
+ STATUS, and APPEND.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 31]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.1. SELECT Command
+
+ Arguments: mailbox name
+
+ Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+ REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
+ UIDNEXT, UIDVALIDITY
+
+ Result: OK - select completed, now in selected state
+ NO - select failure, now in authenticated state: no
+ such mailbox, can't access mailbox
+ BAD - command unknown or arguments invalid
+
+ The SELECT command selects a mailbox so that messages in the
+ mailbox can be accessed. Before returning an OK to the client,
+ the server MUST send the following untagged data to the client.
+ Note that earlier versions of this protocol only required the
+ FLAGS, EXISTS, and RECENT untagged data; consequently, client
+ implementations SHOULD implement default behavior for missing data
+ as discussed with the individual item.
+
+ FLAGS Defined flags in the mailbox. See the description
+ of the FLAGS response for more detail.
+
+ <n> EXISTS The number of messages in the mailbox. See the
+ description of the EXISTS response for more detail.
+
+ <n> RECENT The number of messages with the \Recent flag set.
+ See the description of the RECENT response for more
+ detail.
+
+ OK [UNSEEN <n>]
+ The message sequence number of the first unseen
+ message in the mailbox. If this is missing, the
+ client can not make any assumptions about the first
+ unseen message in the mailbox, and needs to issue a
+ SEARCH command if it wants to find it.
+
+ OK [PERMANENTFLAGS (<list of flags>)]
+ A list of message flags that the client can change
+ permanently. If this is missing, the client should
+ assume that all flags can be changed permanently.
+
+ OK [UIDNEXT <n>]
+ The next unique identifier value. Refer to section
+ 2.3.1.1 for more information. If this is missing,
+ the client can not make any assumptions about the
+ next unique identifier value.
+
+
+
+Crispin Standards Track [Page 32]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ OK [UIDVALIDITY <n>]
+ The unique identifier validity value. Refer to
+ section 2.3.1.1 for more information. If this is
+ missing, the server does not support unique
+ identifiers.
+
+ Only one mailbox can be selected at a time in a connection;
+ simultaneous access to multiple mailboxes requires multiple
+ connections. The SELECT command automatically deselects any
+ currently selected mailbox before attempting the new selection.
+ Consequently, if a mailbox is selected and a SELECT command that
+ fails is attempted, no mailbox is selected.
+
+ If the client is permitted to modify the mailbox, the server
+ SHOULD prefix the text of the tagged OK response with the
+ "[READ-WRITE]" response code.
+
+ If the client is not permitted to modify the mailbox but is
+ permitted read access, the mailbox is selected as read-only, and
+ the server MUST prefix the text of the tagged OK response to
+ SELECT with the "[READ-ONLY]" response code. Read-only access
+ through SELECT differs from the EXAMINE command in that certain
+ read-only mailboxes MAY permit the change of permanent state on a
+ per-user (as opposed to global) basis. Netnews messages marked in
+ a server-based .newsrc file are an example of such per-user
+ permanent state that can be modified with read-only mailboxes.
+
+ Example: C: A142 SELECT INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: A142 OK [READ-WRITE] SELECT completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 33]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.2. EXAMINE Command
+
+ Arguments: mailbox name
+
+ Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+ REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
+ UIDNEXT, UIDVALIDITY
+
+ Result: OK - examine completed, now in selected state
+ NO - examine failure, now in authenticated state: no
+ such mailbox, can't access mailbox
+ BAD - command unknown or arguments invalid
+
+ The EXAMINE command is identical to SELECT and returns the same
+ output; however, the selected mailbox is identified as read-only.
+ No changes to the permanent state of the mailbox, including
+ per-user state, are permitted; in particular, EXAMINE MUST NOT
+ cause messages to lose the \Recent flag.
+
+ The text of the tagged OK response to the EXAMINE command MUST
+ begin with the "[READ-ONLY]" response code.
+
+ Example: C: A932 EXAMINE blurdybloop
+ S: * 17 EXISTS
+ S: * 2 RECENT
+ S: * OK [UNSEEN 8] Message 8 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
+ S: A932 OK [READ-ONLY] EXAMINE completed
+
+
+6.3.3. CREATE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - create completed
+ NO - create failure: can't create mailbox with that name
+ BAD - command unknown or arguments invalid
+
+ The CREATE command creates a mailbox with the given name. An OK
+ response is returned only if a new mailbox with that name has been
+ created. It is an error to attempt to create INBOX or a mailbox
+ with a name that refers to an extant mailbox. Any error in
+ creation will return a tagged NO response.
+
+
+
+Crispin Standards Track [Page 34]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If the mailbox name is suffixed with the server's hierarchy
+ separator character (as returned from the server by a LIST
+ command), this is a declaration that the client intends to create
+ mailbox names under this name in the hierarchy. Server
+ implementations that do not require this declaration MUST ignore
+ the declaration. In any case, the name created is without the
+ trailing hierarchy delimiter.
+
+ If the server's hierarchy separator character appears elsewhere in
+ the name, the server SHOULD create any superior hierarchical names
+ that are needed for the CREATE command to be successfully
+ completed. In other words, an attempt to create "foo/bar/zap" on
+ a server in which "/" is the hierarchy separator character SHOULD
+ create foo/ and foo/bar/ if they do not already exist.
+
+ If a new mailbox is created with the same name as a mailbox which
+ was deleted, its unique identifiers MUST be greater than any
+ unique identifiers used in the previous incarnation of the mailbox
+ UNLESS the new incarnation has a different unique identifier
+ validity value. See the description of the UID command for more
+ detail.
+
+ Example: C: A003 CREATE owatagusiam/
+ S: A003 OK CREATE completed
+ C: A004 CREATE owatagusiam/blurdybloop
+ S: A004 OK CREATE completed
+
+ Note: The interpretation of this example depends on whether
+ "/" was returned as the hierarchy separator from LIST. If
+ "/" is the hierarchy separator, a new level of hierarchy
+ named "owatagusiam" with a member called "blurdybloop" is
+ created. Otherwise, two mailboxes at the same hierarchy
+ level are created.
+
+
+6.3.4. DELETE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - delete completed
+ NO - delete failure: can't delete mailbox with that name
+ BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin Standards Track [Page 35]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The DELETE command permanently removes the mailbox with the given
+ name. A tagged OK response is returned only if the mailbox has
+ been deleted. It is an error to attempt to delete INBOX or a
+ mailbox name that does not exist.
+
+ The DELETE command MUST NOT remove inferior hierarchical names.
+ For example, if a mailbox "foo" has an inferior "foo.bar"
+ (assuming "." is the hierarchy delimiter character), removing
+ "foo" MUST NOT remove "foo.bar". It is an error to attempt to
+ delete a name that has inferior hierarchical names and also has
+ the \Noselect mailbox name attribute (see the description of the
+ LIST response for more details).
+
+ It is permitted to delete a name that has inferior hierarchical
+ names and does not have the \Noselect mailbox name attribute. In
+ this case, all messages in that mailbox are removed, and the name
+ will acquire the \Noselect mailbox name attribute.
+
+ The value of the highest-used unique identifier of the deleted
+ mailbox MUST be preserved so that a new mailbox created with the
+ same name will not reuse the identifiers of the former
+ incarnation, UNLESS the new incarnation has a different unique
+ identifier validity value. See the description of the UID command
+ for more detail.
+
+ Examples: C: A682 LIST "" *
+ S: * LIST () "/" blurdybloop
+ S: * LIST (\Noselect) "/" foo
+ S: * LIST () "/" foo/bar
+ S: A682 OK LIST completed
+ C: A683 DELETE blurdybloop
+ S: A683 OK DELETE completed
+ C: A684 DELETE foo
+ S: A684 NO Name "foo" has inferior hierarchical names
+ C: A685 DELETE foo/bar
+ S: A685 OK DELETE Completed
+ C: A686 LIST "" *
+ S: * LIST (\Noselect) "/" foo
+ S: A686 OK LIST completed
+ C: A687 DELETE foo
+ S: A687 OK DELETE Completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 36]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ C: A82 LIST "" *
+ S: * LIST () "." blurdybloop
+ S: * LIST () "." foo
+ S: * LIST () "." foo.bar
+ S: A82 OK LIST completed
+ C: A83 DELETE blurdybloop
+ S: A83 OK DELETE completed
+ C: A84 DELETE foo
+ S: A84 OK DELETE Completed
+ C: A85 LIST "" *
+ S: * LIST () "." foo.bar
+ S: A85 OK LIST completed
+ C: A86 LIST "" %
+ S: * LIST (\Noselect) "." foo
+ S: A86 OK LIST completed
+
+
+6.3.5. RENAME Command
+
+ Arguments: existing mailbox name
+ new mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - rename completed
+ NO - rename failure: can't rename mailbox with that name,
+ can't rename to mailbox with that name
+ BAD - command unknown or arguments invalid
+
+ The RENAME command changes the name of a mailbox. A tagged OK
+ response is returned only if the mailbox has been renamed. It is
+ an error to attempt to rename from a mailbox name that does not
+ exist or to a mailbox name that already exists. Any error in
+ renaming will return a tagged NO response.
+
+ If the name has inferior hierarchical names, then the inferior
+ hierarchical names MUST also be renamed. For example, a rename of
+ "foo" to "zap" will rename "foo/bar" (assuming "/" is the
+ hierarchy delimiter character) to "zap/bar".
+
+ If the server's hierarchy separator character appears in the name,
+ the server SHOULD create any superior hierarchical names that are
+ needed for the RENAME command to complete successfully. In other
+ words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
+ server in which "/" is the hierarchy separator character SHOULD
+ create baz/ and baz/rag/ if they do not already exist.
+
+
+
+
+
+Crispin Standards Track [Page 37]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The value of the highest-used unique identifier of the old mailbox
+ name MUST be preserved so that a new mailbox created with the same
+ name will not reuse the identifiers of the former incarnation,
+ UNLESS the new incarnation has a different unique identifier
+ validity value. See the description of the UID command for more
+ detail.
+
+ Renaming INBOX is permitted, and has special behavior. It moves
+ all messages in INBOX to a new mailbox with the given name,
+ leaving INBOX empty. If the server implementation supports
+ inferior hierarchical names of INBOX, these are unaffected by a
+ rename of INBOX.
+
+ Examples: C: A682 LIST "" *
+ S: * LIST () "/" blurdybloop
+ S: * LIST (\Noselect) "/" foo
+ S: * LIST () "/" foo/bar
+ S: A682 OK LIST completed
+ C: A683 RENAME blurdybloop sarasoop
+ S: A683 OK RENAME completed
+ C: A684 RENAME foo zowie
+ S: A684 OK RENAME Completed
+ C: A685 LIST "" *
+ S: * LIST () "/" sarasoop
+ S: * LIST (\Noselect) "/" zowie
+ S: * LIST () "/" zowie/bar
+ S: A685 OK LIST completed
+
+ C: Z432 LIST "" *
+ S: * LIST () "." INBOX
+ S: * LIST () "." INBOX.bar
+ S: Z432 OK LIST completed
+ C: Z433 RENAME INBOX old-mail
+ S: Z433 OK RENAME completed
+ C: Z434 LIST "" *
+ S: * LIST () "." INBOX
+ S: * LIST () "." INBOX.bar
+ S: * LIST () "." old-mail
+ S: Z434 OK LIST completed
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 38]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.6. SUBSCRIBE Command
+
+ Arguments: mailbox
+
+ Responses: no specific responses for this command
+
+ Result: OK - subscribe completed
+ NO - subscribe failure: can't subscribe to that name
+ BAD - command unknown or arguments invalid
+
+ The SUBSCRIBE command adds the specified mailbox name to the
+ server's set of "active" or "subscribed" mailboxes as returned by
+ the LSUB command. This command returns a tagged OK response only
+ if the subscription is successful.
+
+ A server MAY validate the mailbox argument to SUBSCRIBE to verify
+ that it exists. However, it MUST NOT unilaterally remove an
+ existing mailbox name from the subscription list even if a mailbox
+ by that name no longer exists.
+
+ Note: This requirement is because a server site can
+ choose to routinely remove a mailbox with a well-known
+ name (e.g., "system-alerts") after its contents expire,
+ with the intention of recreating it when new contents
+ are appropriate.
+
+
+ Example: C: A002 SUBSCRIBE #news.comp.mail.mime
+ S: A002 OK SUBSCRIBE completed
+
+
+6.3.7. UNSUBSCRIBE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - unsubscribe completed
+ NO - unsubscribe failure: can't unsubscribe that name
+ BAD - command unknown or arguments invalid
+
+ The UNSUBSCRIBE command removes the specified mailbox name from
+ the server's set of "active" or "subscribed" mailboxes as returned
+ by the LSUB command. This command returns a tagged OK response
+ only if the unsubscription is successful.
+
+ Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime
+ S: A002 OK UNSUBSCRIBE completed
+
+
+
+Crispin Standards Track [Page 39]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.8. LIST Command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LIST
+
+ Result: OK - list completed
+ NO - list failure: can't list that reference or name
+ BAD - command unknown or arguments invalid
+
+ The LIST command returns a subset of names from the complete set
+ of all names available to the client. Zero or more untagged LIST
+ replies are returned, containing the name attributes, hierarchy
+ delimiter, and name; see the description of the LIST reply for
+ more detail.
+
+ The LIST command SHOULD return its data quickly, without undue
+ delay. For example, it SHOULD NOT go to excess trouble to
+ calculate the \Marked or \Unmarked status or perform other
+ processing; if each name requires 1 second of processing, then a
+ list of 1200 names would take 20 minutes!
+
+ An empty ("" string) reference name argument indicates that the
+ mailbox name is interpreted as by SELECT. The returned mailbox
+ names MUST match the supplied mailbox name pattern. A non-empty
+ reference name argument is the name of a mailbox or a level of
+ mailbox hierarchy, and indicates the context in which the mailbox
+ name is interpreted.
+
+ An empty ("" string) mailbox name argument is a special request to
+ return the hierarchy delimiter and the root name of the name given
+ in the reference. The value returned as the root MAY be the empty
+ string if the reference is non-rooted or is an empty string. In
+ all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
+ is returned. This permits a client to get the hierarchy delimiter
+ (or find out that the mailbox names are flat) even when no
+ mailboxes by that name currently exist.
+
+ The reference and mailbox name arguments are interpreted into a
+ canonical form that represents an unambiguous left-to-right
+ hierarchy. The returned mailbox names will be in the interpreted
+ form.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 40]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Note: The interpretation of the reference argument is
+ implementation-defined. It depends upon whether the
+ server implementation has a concept of the "current
+ working directory" and leading "break out characters",
+ which override the current working directory.
+
+ For example, on a server which exports a UNIX or NT
+ filesystem, the reference argument contains the current
+ working directory, and the mailbox name argument would
+ contain the name as interpreted in the current working
+ directory.
+
+ If a server implementation has no concept of break out
+ characters, the canonical form is normally the reference
+ name appended with the mailbox name. Note that if the
+ server implements the namespace convention (section
+ 5.1.2), "#" is a break out character and must be treated
+ as such.
+
+ If the reference argument is not a level of mailbox
+ hierarchy (that is, it is a \NoInferiors name), and/or
+ the reference argument does not end with the hierarchy
+ delimiter, it is implementation-dependent how this is
+ interpreted. For example, a reference of "foo/bar" and
+ mailbox name of "rag/baz" could be interpreted as
+ "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
+ A client SHOULD NOT use such a reference argument except
+ at the explicit request of the user. A hierarchical
+ browser MUST NOT make any assumptions about server
+ interpretation of the reference unless the reference is
+ a level of mailbox hierarchy AND ends with the hierarchy
+ delimiter.
+
+ Any part of the reference argument that is included in the
+ interpreted form SHOULD prefix the interpreted form. It SHOULD
+ also be in the same form as the reference name argument. This
+ rule permits the client to determine if the returned mailbox name
+ is in the context of the reference argument, or if something about
+ the mailbox argument overrode the reference argument. Without
+ this rule, the client would have to have knowledge of the server's
+ naming semantics including what characters are "breakouts" that
+ override a naming context.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 41]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, here are some examples of how references
+ and mailbox names might be interpreted on a UNIX-based
+ server:
+
+ Reference Mailbox Name Interpretation
+ ------------ ------------ --------------
+ ~smith/Mail/ foo.* ~smith/Mail/foo.*
+ archive/ % archive/%
+ #news. comp.mail.* #news.comp.mail.*
+ ~smith/Mail/ /usr/doc/foo /usr/doc/foo
+ archive/ ~fred/Mail/* ~fred/Mail/*
+
+ The first three examples demonstrate interpretations in
+ the context of the reference argument. Note that
+ "~smith/Mail" SHOULD NOT be transformed into something
+ like "/u2/users/smith/Mail", or it would be impossible
+ for the client to determine that the interpretation was
+ in the context of the reference.
+
+ The character "*" is a wildcard, and matches zero or more
+ characters at this position. The character "%" is similar to "*",
+ but it does not match a hierarchy delimiter. If the "%" wildcard
+ is the last character of a mailbox name argument, matching levels
+ of hierarchy are also returned. If these levels of hierarchy are
+ not also selectable mailboxes, they are returned with the
+ \Noselect mailbox name attribute (see the description of the LIST
+ response for more details).
+
+ Server implementations are permitted to "hide" otherwise
+ accessible mailboxes from the wildcard characters, by preventing
+ certain characters or names from matching a wildcard in certain
+ situations. For example, a UNIX-based server might restrict the
+ interpretation of "*" so that an initial "/" character does not
+ match.
+
+ The special name INBOX is included in the output from LIST, if
+ INBOX is supported by this server for this user and if the
+ uppercase string "INBOX" matches the interpreted reference and
+ mailbox name arguments with wildcards as described above. The
+ criteria for omitting INBOX is whether SELECT INBOX will return
+ failure; it is not relevant whether the user's real INBOX resides
+ on this or some other server.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 42]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A101 LIST "" ""
+ S: * LIST (\Noselect) "/" ""
+ S: A101 OK LIST Completed
+ C: A102 LIST #news.comp.mail.misc ""
+ S: * LIST (\Noselect) "." #news.
+ S: A102 OK LIST Completed
+ C: A103 LIST /usr/staff/jones ""
+ S: * LIST (\Noselect) "/" /
+ S: A103 OK LIST Completed
+ C: A202 LIST ~/Mail/ %
+ S: * LIST (\Noselect) "/" ~/Mail/foo
+ S: * LIST () "/" ~/Mail/meetings
+ S: A202 OK LIST completed
+
+
+6.3.9. LSUB Command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LSUB
+
+ Result: OK - lsub completed
+ NO - lsub failure: can't list that reference or name
+ BAD - command unknown or arguments invalid
+
+ The LSUB command returns a subset of names from the set of names
+ that the user has declared as being "active" or "subscribed".
+ Zero or more untagged LSUB replies are returned. The arguments to
+ LSUB are in the same form as those for LIST.
+
+ The returned untagged LSUB response MAY contain different mailbox
+ flags from a LIST untagged response. If this should happen, the
+ flags in the untagged LIST are considered more authoritative.
+
+ A special situation occurs when using LSUB with the % wildcard.
+ Consider what happens if "foo/bar" (with a hierarchy delimiter of
+ "/") is subscribed but "foo" is not. A "%" wildcard to LSUB must
+ return foo, not foo/bar, in the LSUB response, and it MUST be
+ flagged with the \Noselect attribute.
+
+ The server MUST NOT unilaterally remove an existing mailbox name
+ from the subscription list even if a mailbox by that name no
+ longer exists.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 43]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A002 LSUB "#news." "comp.mail.*"
+ S: * LSUB () "." #news.comp.mail.mime
+ S: * LSUB () "." #news.comp.mail.misc
+ S: A002 OK LSUB completed
+ C: A003 LSUB "#news." "comp.%"
+ S: * LSUB (\NoSelect) "." #news.comp.mail
+ S: A003 OK LSUB completed
+
+
+6.3.10. STATUS Command
+
+ Arguments: mailbox name
+ status data item names
+
+ Responses: untagged responses: STATUS
+
+ Result: OK - status completed
+ NO - status failure: no status for that name
+ BAD - command unknown or arguments invalid
+
+ The STATUS command requests the status of the indicated mailbox.
+ It does not change the currently selected mailbox, nor does it
+ affect the state of any messages in the queried mailbox (in
+ particular, STATUS MUST NOT cause messages to lose the \Recent
+ flag).
+
+ The STATUS command provides an alternative to opening a second
+ IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
+ query that mailbox's status without deselecting the current
+ mailbox in the first IMAP4rev1 connection.
+
+ Unlike the LIST command, the STATUS command is not guaranteed to
+ be fast in its response. Under certain circumstances, it can be
+ quite slow. In some implementations, the server is obliged to
+ open the mailbox read-only internally to obtain certain status
+ information. Also unlike the LIST command, the STATUS command
+ does not accept wildcards.
+
+ Note: The STATUS command is intended to access the
+ status of mailboxes other than the currently selected
+ mailbox. Because the STATUS command can cause the
+ mailbox to be opened internally, and because this
+ information is available by other means on the selected
+ mailbox, the STATUS command SHOULD NOT be used on the
+ currently selected mailbox.
+
+
+
+
+
+
+Crispin Standards Track [Page 44]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The STATUS command MUST NOT be used as a "check for new
+ messages in the selected mailbox" operation (refer to
+ sections 7, 7.3.1, and 7.3.2 for more information about
+ the proper method for new message checking).
+
+ Because the STATUS command is not guaranteed to be fast
+ in its results, clients SHOULD NOT expect to be able to
+ issue many consecutive STATUS commands and obtain
+ reasonable performance.
+
+ The currently defined status data items that can be requested are:
+
+ MESSAGES
+ The number of messages in the mailbox.
+
+ RECENT
+ The number of messages with the \Recent flag set.
+
+ UIDNEXT
+ The next unique identifier value of the mailbox. Refer to
+ section 2.3.1.1 for more information.
+
+ UIDVALIDITY
+ The unique identifier validity value of the mailbox. Refer to
+ section 2.3.1.1 for more information.
+
+ UNSEEN
+ The number of messages which do not have the \Seen flag set.
+
+
+ Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
+ S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+ S: A042 OK STATUS completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 45]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.11. APPEND Command
+
+ Arguments: mailbox name
+ OPTIONAL flag parenthesized list
+ OPTIONAL date/time string
+ message literal
+
+ Responses: no specific responses for this command
+
+ Result: OK - append completed
+ NO - append error: can't append to that mailbox, error
+ in flags or date/time or message text
+ BAD - command unknown or arguments invalid
+
+ The APPEND command appends the literal argument as a new message
+ to the end of the specified destination mailbox. This argument
+ SHOULD be in the format of an [RFC-2822] message. 8-bit
+ characters are permitted in the message. A server implementation
+ that is unable to preserve 8-bit data properly MUST be able to
+ reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
+ content transfer encoding.
+
+ Note: There MAY be exceptions, e.g., draft messages, in
+ which required [RFC-2822] header lines are omitted in
+ the message literal argument to APPEND. The full
+ implications of doing so MUST be understood and
+ carefully weighed.
+
+ If a flag parenthesized list is specified, the flags SHOULD be set
+ in the resulting message; otherwise, the flag list of the
+ resulting message is set to empty by default. In either case, the
+ Recent flag is also set.
+
+ If a date-time is specified, the internal date SHOULD be set in
+ the resulting message; otherwise, the internal date of the
+ resulting message is set to the current date and time by default.
+
+ If the append is unsuccessful for any reason, the mailbox MUST be
+ restored to its state before the APPEND attempt; no partial
+ appending is permitted.
+
+ If the destination mailbox does not exist, a server MUST return an
+ error, and MUST NOT automatically create the mailbox. Unless it
+ is certain that the destination mailbox can not be created, the
+ server MUST send the response code "[TRYCREATE]" as the prefix of
+ the text of the tagged NO response. This gives a hint to the
+ client that it can attempt a CREATE command and retry the APPEND
+ if the CREATE is successful.
+
+
+
+Crispin Standards Track [Page 46]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If the mailbox is currently selected, the normal new message
+ actions SHOULD occur. Specifically, the server SHOULD notify the
+ client immediately via an untagged EXISTS response. If the server
+ does not do so, the client MAY issue a NOOP command (or failing
+ that, a CHECK command) after one or more APPEND commands.
+
+ Example: C: A003 APPEND saved-messages (\Seen) {310}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@Blurdybloop.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@Blurdybloop.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK APPEND completed
+
+ Note: The APPEND command is not used for message delivery,
+ because it does not provide a mechanism to transfer [SMTP]
+ envelope information.
+
+6.4. Client Commands - Selected State
+
+ In the selected state, commands that manipulate messages in a mailbox
+ are permitted.
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ and the authenticated state commands (SELECT, EXAMINE, CREATE,
+ DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
+ APPEND), the following commands are valid in the selected state:
+ CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
+
+6.4.1. CHECK Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - check completed
+ BAD - command unknown or arguments invalid
+
+ The CHECK command requests a checkpoint of the currently selected
+ mailbox. A checkpoint refers to any implementation-dependent
+ housekeeping associated with the mailbox (e.g., resolving the
+ server's in-memory state of the mailbox with the state on its
+
+
+
+Crispin Standards Track [Page 47]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ disk) that is not normally executed as part of each command. A
+ checkpoint MAY take a non-instantaneous amount of real time to
+ complete. If a server implementation has no such housekeeping
+ considerations, CHECK is equivalent to NOOP.
+
+ There is no guarantee that an EXISTS untagged response will happen
+ as a result of CHECK. NOOP, not CHECK, SHOULD be used for new
+ message polling.
+
+ Example: C: FXXZ CHECK
+ S: FXXZ OK CHECK Completed
+
+
+6.4.2. CLOSE Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - close completed, now in authenticated state
+ BAD - command unknown or arguments invalid
+
+ The CLOSE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox, and returns
+ to the authenticated state from the selected state. No untagged
+ EXPUNGE responses are sent.
+
+ No messages are removed, and no error is given, if the mailbox is
+ selected by an EXAMINE command or is otherwise selected read-only.
+
+ Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT
+ command MAY be issued without previously issuing a CLOSE command.
+ The SELECT, EXAMINE, and LOGOUT commands implicitly close the
+ currently selected mailbox without doing an expunge. However,
+ when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
+ sequence is considerably faster than an EXPUNGE-LOGOUT or
+ EXPUNGE-SELECT because no untagged EXPUNGE responses (which the
+ client would probably ignore) are sent.
+
+ Example: C: A341 CLOSE
+ S: A341 OK CLOSE completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 48]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.4.3. EXPUNGE Command
+
+ Arguments: none
+
+ Responses: untagged responses: EXPUNGE
+
+ Result: OK - expunge completed
+ NO - expunge failure: can't expunge (e.g., permission
+ denied)
+ BAD - command unknown or arguments invalid
+
+ The EXPUNGE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox. Before
+ returning an OK to the client, an untagged EXPUNGE response is
+ sent for each message that is removed.
+
+ Example: C: A202 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 5 EXPUNGE
+ S: * 8 EXPUNGE
+ S: A202 OK EXPUNGE completed
+
+ Note: In this example, messages 3, 4, 7, and 11 had the
+ \Deleted flag set. See the description of the EXPUNGE
+ response for further explanation.
+
+
+6.4.4. SEARCH Command
+
+ Arguments: OPTIONAL [CHARSET] specification
+ searching criteria (one or more)
+
+ Responses: REQUIRED untagged response: SEARCH
+
+ Result: OK - search completed
+ NO - search error: can't search that [CHARSET] or
+ criteria
+ BAD - command unknown or arguments invalid
+
+ The SEARCH command searches the mailbox for messages that match
+ the given searching criteria. Searching criteria consist of one
+ or more search keys. The untagged SEARCH response from the server
+ contains a listing of message sequence numbers corresponding to
+ those messages that match the searching criteria.
+
+
+
+
+
+
+Crispin Standards Track [Page 49]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ When multiple keys are specified, the result is the intersection
+ (AND function) of all the messages that match those keys. For
+ example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
+ to all deleted messages from Smith that were placed in the mailbox
+ since February 1, 1994. A search key can also be a parenthesized
+ list of one or more search keys (e.g., for use with the OR and NOT
+ keys).
+
+ Server implementations MAY exclude [MIME-IMB] body parts with
+ terminal content media types other than TEXT and MESSAGE from
+ consideration in SEARCH matching.
+
+ The OPTIONAL [CHARSET] specification consists of the word
+ "CHARSET" followed by a registered [CHARSET]. It indicates the
+ [CHARSET] of the strings that appear in the search criteria.
+ [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
+ [RFC-2822]/[MIME-IMB] headers, MUST be decoded before comparing
+ text in a [CHARSET] other than US-ASCII. US-ASCII MUST be
+ supported; other [CHARSET]s MAY be supported.
+
+ If the server does not support the specified [CHARSET], it MUST
+ return a tagged NO response (not a BAD). This response SHOULD
+ contain the BADCHARSET response code, which MAY list the
+ [CHARSET]s supported by the server.
+
+ In all search keys that use strings, a message matches the key if
+ the string is a substring of the field. The matching is
+ case-insensitive.
+
+ The defined search keys are as follows. Refer to the Formal
+ Syntax section for the precise syntactic definitions of the
+ arguments.
+
+ <sequence set>
+ Messages with message sequence numbers corresponding to the
+ specified message sequence number set.
+
+ ALL
+ All messages in the mailbox; the default initial key for
+ ANDing.
+
+ ANSWERED
+ Messages with the \Answered flag set.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 50]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BCC <string>
+ Messages that contain the specified string in the envelope
+ structure's BCC field.
+
+ BEFORE <date>
+ Messages whose internal date (disregarding time and timezone)
+ is earlier than the specified date.
+
+ BODY <string>
+ Messages that contain the specified string in the body of the
+ message.
+
+ CC <string>
+ Messages that contain the specified string in the envelope
+ structure's CC field.
+
+ DELETED
+ Messages with the \Deleted flag set.
+
+ DRAFT
+ Messages with the \Draft flag set.
+
+ FLAGGED
+ Messages with the \Flagged flag set.
+
+ FROM <string>
+ Messages that contain the specified string in the envelope
+ structure's FROM field.
+
+ HEADER <field-name> <string>
+ Messages that have a header with the specified field-name (as
+ defined in [RFC-2822]) and that contains the specified string
+ in the text of the header (what comes after the colon). If the
+ string to search is zero-length, this matches all messages that
+ have a header line with the specified field-name regardless of
+ the contents.
+
+ KEYWORD <flag>
+ Messages with the specified keyword flag set.
+
+ LARGER <n>
+ Messages with an [RFC-2822] size larger than the specified
+ number of octets.
+
+ NEW
+ Messages that have the \Recent flag set but not the \Seen flag.
+ This is functionally equivalent to "(RECENT UNSEEN)".
+
+
+
+
+Crispin Standards Track [Page 51]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ NOT <search-key>
+ Messages that do not match the specified search key.
+
+ OLD
+ Messages that do not have the \Recent flag set. This is
+ functionally equivalent to "NOT RECENT" (as opposed to "NOT
+ NEW").
+
+ ON <date>
+ Messages whose internal date (disregarding time and timezone)
+ is within the specified date.
+
+ OR <search-key1> <search-key2>
+ Messages that match either search key.
+
+ RECENT
+ Messages that have the \Recent flag set.
+
+ SEEN
+ Messages that have the \Seen flag set.
+
+ SENTBEFORE <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is earlier than the specified date.
+
+ SENTON <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is within the specified date.
+
+ SENTSINCE <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is within or later than the specified date.
+
+ SINCE <date>
+ Messages whose internal date (disregarding time and timezone)
+ is within or later than the specified date.
+
+ SMALLER <n>
+ Messages with an [RFC-2822] size smaller than the specified
+ number of octets.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 52]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SUBJECT <string>
+ Messages that contain the specified string in the envelope
+ structure's SUBJECT field.
+
+ TEXT <string>
+ Messages that contain the specified string in the header or
+ body of the message.
+
+ TO <string>
+ Messages that contain the specified string in the envelope
+ structure's TO field.
+
+ UID <sequence set>
+ Messages with unique identifiers corresponding to the specified
+ unique identifier set. Sequence set ranges are permitted.
+
+ UNANSWERED
+ Messages that do not have the \Answered flag set.
+
+ UNDELETED
+ Messages that do not have the \Deleted flag set.
+
+ UNDRAFT
+ Messages that do not have the \Draft flag set.
+
+ UNFLAGGED
+ Messages that do not have the \Flagged flag set.
+
+ UNKEYWORD <flag>
+ Messages that do not have the specified keyword flag set.
+
+ UNSEEN
+ Messages that do not have the \Seen flag set.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 53]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
+ S: * SEARCH 2 84 882
+ S: A282 OK SEARCH completed
+ C: A283 SEARCH TEXT "string not in mailbox"
+ S: * SEARCH
+ S: A283 OK SEARCH completed
+ C: A284 SEARCH CHARSET UTF-8 TEXT {6}
+ C: XXXXXX
+ S: * SEARCH 43
+ S: A284 OK SEARCH completed
+
+ Note: Since this document is restricted to 7-bit ASCII
+ text, it is not possible to show actual UTF-8 data. The
+ "XXXXXX" is a placeholder for what would be 6 octets of
+ 8-bit data in an actual transaction.
+
+
+6.4.5. FETCH Command
+
+ Arguments: sequence set
+ message data item names or macro
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - fetch completed
+ NO - fetch error: can't fetch that data
+ BAD - command unknown or arguments invalid
+
+ The FETCH command retrieves data associated with a message in the
+ mailbox. The data items to be fetched can be either a single atom
+ or a parenthesized list.
+
+ Most data items, identified in the formal syntax under the
+ msg-att-static rule, are static and MUST NOT change for any
+ particular message. Other data items, identified in the formal
+ syntax under the msg-att-dynamic rule, MAY change, either as a
+ result of a STORE command or due to external events.
+
+ For example, if a client receives an ENVELOPE for a
+ message when it already knows the envelope, it can
+ safely ignore the newly transmitted envelope.
+
+ There are three macros which specify commonly-used sets of data
+ items, and can be used instead of data items. A macro must be
+ used by itself, and not in conjunction with other macros or data
+ items.
+
+
+
+
+
+Crispin Standards Track [Page 54]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ ALL
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)
+
+ FAST
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)
+
+ FULL
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
+ BODY)
+
+ The currently defined data items that can be fetched are:
+
+ BODY
+ Non-extensible form of BODYSTRUCTURE.
+
+ BODY[<section>]<<partial>>
+ The text of a particular body section. The section
+ specification is a set of zero or more part specifiers
+ delimited by periods. A part specifier is either a part number
+ or one of the following: HEADER, HEADER.FIELDS,
+ HEADER.FIELDS.NOT, MIME, and TEXT. An empty section
+ specification refers to the entire message, including the
+ header.
+
+ Every message has at least one part number. Non-[MIME-IMB]
+ messages, and non-multipart [MIME-IMB] messages with no
+ encapsulated message, only have a part 1.
+
+ Multipart messages are assigned consecutive part numbers, as
+ they occur in the message. If a particular part is of type
+ message or multipart, its parts MUST be indicated by a period
+ followed by the part number within that nested multipart part.
+
+ A part of type MESSAGE/RFC822 also has nested part numbers,
+ referring to parts of the MESSAGE part's body.
+
+ The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part
+ specifiers can be the sole part specifier or can be prefixed by
+ one or more numeric part specifiers, provided that the numeric
+ part specifier refers to a part of type MESSAGE/RFC822. The
+ MIME part specifier MUST be prefixed by one or more numeric
+ part specifiers.
+
+ The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
+ specifiers refer to the [RFC-2822] header of the message or of
+ an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
+ HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
+ field-name (as defined in [RFC-2822]) names, and return a
+
+
+
+Crispin Standards Track [Page 55]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ subset of the header. The subset returned by HEADER.FIELDS
+ contains only those header fields with a field-name that
+ matches one of the names in the list; similarly, the subset
+ returned by HEADER.FIELDS.NOT contains only the header fields
+ with a non-matching field-name. The field-matching is
+ case-insensitive but otherwise exact. Subsetting does not
+ exclude the [RFC-2822] delimiting blank line between the header
+ and the body; the blank line is included in all header fetches,
+ except in the case of a message which has no body and no blank
+ line.
+
+ The MIME part specifier refers to the [MIME-IMB] header for
+ this part.
+
+ The TEXT part specifier refers to the text body of the message,
+ omitting the [RFC-2822] header.
+
+ Here is an example of a complex message with some of its
+ part specifiers:
+
+ HEADER ([RFC-2822] header of the message)
+ TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 1 TEXT/PLAIN
+ 2 APPLICATION/OCTET-STREAM
+ 3 MESSAGE/RFC822
+ 3.HEADER ([RFC-2822] header of the message)
+ 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 3.1 TEXT/PLAIN
+ 3.2 APPLICATION/OCTET-STREAM
+ 4 MULTIPART/MIXED
+ 4.1 IMAGE/GIF
+ 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
+ 4.2 MESSAGE/RFC822
+ 4.2.HEADER ([RFC-2822] header of the message)
+ 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 4.2.1 TEXT/PLAIN
+ 4.2.2 MULTIPART/ALTERNATIVE
+ 4.2.2.1 TEXT/PLAIN
+ 4.2.2.2 TEXT/RICHTEXT
+
+
+ It is possible to fetch a substring of the designated text.
+ This is done by appending an open angle bracket ("<"), the
+ octet position of the first desired octet, a period, the
+ maximum number of octets desired, and a close angle bracket
+ (">") to the part specifier. If the starting octet is beyond
+ the end of the text, an empty string is returned.
+
+
+
+
+Crispin Standards Track [Page 56]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Any partial fetch that attempts to read beyond the end of the
+ text is truncated as appropriate. A partial fetch that starts
+ at octet 0 is returned as a partial fetch, even if this
+ truncation happened.
+
+ Note: This means that BODY[]<0.2048> of a 1500-octet message
+ will return BODY[]<0> with a literal of size 1500, not
+ BODY[].
+
+ Note: A substring fetch of a HEADER.FIELDS or
+ HEADER.FIELDS.NOT part specifier is calculated after
+ subsetting the header.
+
+ The \Seen flag is implicitly set; if this causes the flags to
+ change, they SHOULD be included as part of the FETCH responses.
+
+ BODY.PEEK[<section>]<<partial>>
+ An alternate form of BODY[<section>] that does not implicitly
+ set the \Seen flag.
+
+ BODYSTRUCTURE
+ The [MIME-IMB] body structure of the message. This is computed
+ by the server by parsing the [MIME-IMB] header fields in the
+ [RFC-2822] header and [MIME-IMB] headers.
+
+ ENVELOPE
+ The envelope structure of the message. This is computed by the
+ server by parsing the [RFC-2822] header into the component
+ parts, defaulting various fields as necessary.
+
+ FLAGS
+ The flags that are set for this message.
+
+ INTERNALDATE
+ The internal date of the message.
+
+ RFC822
+ Functionally equivalent to BODY[], differing in the syntax of
+ the resulting untagged FETCH data (RFC822 is returned).
+
+ RFC822.HEADER
+ Functionally equivalent to BODY.PEEK[HEADER], differing in the
+ syntax of the resulting untagged FETCH data (RFC822.HEADER is
+ returned).
+
+ RFC822.SIZE
+ The [RFC-2822] size of the message.
+
+
+
+
+Crispin Standards Track [Page 57]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ RFC822.TEXT
+ Functionally equivalent to BODY[TEXT], differing in the syntax
+ of the resulting untagged FETCH data (RFC822.TEXT is returned).
+
+ UID
+ The unique identifier for the message.
+
+
+ Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
+ S: * 2 FETCH ....
+ S: * 3 FETCH ....
+ S: * 4 FETCH ....
+ S: A654 OK FETCH completed
+
+
+6.4.6. STORE Command
+
+ Arguments: sequence set
+ message data item name
+ value for message data item
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - store completed
+ NO - store error: can't store that data
+ BAD - command unknown or arguments invalid
+
+ The STORE command alters data associated with a message in the
+ mailbox. Normally, STORE will return the updated value of the
+ data with an untagged FETCH response. A suffix of ".SILENT" in
+ the data item name prevents the untagged FETCH, and the server
+ SHOULD assume that the client has determined the updated value
+ itself or does not care about the updated value.
+
+ Note: Regardless of whether or not the ".SILENT" suffix
+ was used, the server SHOULD send an untagged FETCH
+ response if a change to a message's flags from an
+ external source is observed. The intent is that the
+ status of the flags is determinate without a race
+ condition.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 58]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The currently defined data items that can be stored are:
+
+ FLAGS <flag list>
+ Replace the flags for the message (other than \Recent) with the
+ argument. The new value of the flags is returned as if a FETCH
+ of those flags was done.
+
+ FLAGS.SILENT <flag list>
+ Equivalent to FLAGS, but without returning a new value.
+
+ +FLAGS <flag list>
+ Add the argument to the flags for the message. The new value
+ of the flags is returned as if a FETCH of those flags was done.
+
+ +FLAGS.SILENT <flag list>
+ Equivalent to +FLAGS, but without returning a new value.
+
+ -FLAGS <flag list>
+ Remove the argument from the flags for the message. The new
+ value of the flags is returned as if a FETCH of those flags was
+ done.
+
+ -FLAGS.SILENT <flag list>
+ Equivalent to -FLAGS, but without returning a new value.
+
+
+ Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
+ S: * 2 FETCH (FLAGS (\Deleted \Seen))
+ S: * 3 FETCH (FLAGS (\Deleted))
+ S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
+ S: A003 OK STORE completed
+
+
+6.4.7. COPY Command
+
+ Arguments: sequence set
+ mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - copy completed
+ NO - copy error: can't copy those messages or to that
+ name
+ BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin Standards Track [Page 59]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The COPY command copies the specified message(s) to the end of the
+ specified destination mailbox. The flags and internal date of the
+ message(s) SHOULD be preserved, and the Recent flag SHOULD be set,
+ in the copy.
+
+ If the destination mailbox does not exist, a server SHOULD return
+ an error. It SHOULD NOT automatically create the mailbox. Unless
+ it is certain that the destination mailbox can not be created, the
+ server MUST send the response code "[TRYCREATE]" as the prefix of
+ the text of the tagged NO response. This gives a hint to the
+ client that it can attempt a CREATE command and retry the COPY if
+ the CREATE is successful.
+
+ If the COPY command is unsuccessful for any reason, server
+ implementations MUST restore the destination mailbox to its state
+ before the COPY attempt.
+
+ Example: C: A003 COPY 2:4 MEETING
+ S: A003 OK COPY completed
+
+
+6.4.8. UID Command
+
+ Arguments: command name
+ command arguments
+
+ Responses: untagged responses: FETCH, SEARCH
+
+ Result: OK - UID command completed
+ NO - UID command error
+ BAD - command unknown or arguments invalid
+
+ The UID command has two forms. In the first form, it takes as its
+ arguments a COPY, FETCH, or STORE command with arguments
+ appropriate for the associated command. However, the numbers in
+ the sequence set argument are unique identifiers instead of
+ message sequence numbers. Sequence set ranges are permitted, but
+ there is no guarantee that unique identifiers will be contiguous.
+
+ A non-existent unique identifier is ignored without any error
+ message generated. Thus, it is possible for a UID FETCH command
+ to return an OK without any data or a UID COPY or UID STORE to
+ return an OK without performing any operations.
+
+ In the second form, the UID command takes a SEARCH command with
+ SEARCH command arguments. The interpretation of the arguments is
+ the same as with SEARCH; however, the numbers returned in a SEARCH
+ response for a UID SEARCH command are unique identifiers instead
+
+
+
+Crispin Standards Track [Page 60]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ of message sequence numbers. For example, the command UID SEARCH
+ 1:100 UID 443:557 returns the unique identifiers corresponding to
+ the intersection of two sequence sets, the message sequence number
+ range 1:100 and the UID range 443:557.
+
+ Note: in the above example, the UID range 443:557
+ appears. The same comment about a non-existent unique
+ identifier being ignored without any error message also
+ applies here. Hence, even if neither UID 443 or 557
+ exist, this range is valid and would include an existing
+ UID 495.
+
+ Also note that a UID range of 559:* always includes the
+ UID of the last message in the mailbox, even if 559 is
+ higher than any assigned UID value. This is because the
+ contents of a range are independent of the order of the
+ range endpoints. Thus, any UID range with * as one of
+ the endpoints indicates at least one message (the
+ message with the highest numbered UID), unless the
+ mailbox is empty.
+
+ The number after the "*" in an untagged FETCH response is always a
+ message sequence number, not a unique identifier, even for a UID
+ command response. However, server implementations MUST implicitly
+ include the UID message data item as part of any FETCH response
+ caused by a UID command, regardless of whether a UID was specified
+ as a message data item to the FETCH.
+
+
+ Note: The rule about including the UID message data item as part
+ of a FETCH response primarily applies to the UID FETCH and UID
+ STORE commands, including a UID FETCH command that does not
+ include UID as a message data item. Although it is unlikely that
+ the other UID commands will cause an untagged FETCH, this rule
+ applies to these commands as well.
+
+ Example: C: A999 UID FETCH 4827313:4828442 FLAGS
+ S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
+ S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
+ S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
+ S: A999 OK UID FETCH completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 61]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.5. Client Commands - Experimental/Expansion
+
+
+6.5.1. X<atom> Command
+
+ Arguments: implementation defined
+
+ Responses: implementation defined
+
+ Result: OK - command completed
+ NO - failure
+ BAD - command unknown or arguments invalid
+
+ Any command prefixed with an X is an experimental command.
+ Commands which are not part of this specification, a standard or
+ standards-track revision of this specification, or an
+ IESG-approved experimental protocol, MUST use the X prefix.
+
+ Any added untagged responses issued by an experimental command
+ MUST also be prefixed with an X. Server implementations MUST NOT
+ send any such untagged responses, unless the client requested it
+ by issuing the associated experimental command.
+
+ Example: C: a441 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 XPIG-LATIN
+ S: a441 OK CAPABILITY completed
+ C: A442 XPIG-LATIN
+ S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
+ S: A442 OK XPIG-LATIN ompleted-cay
+
+7. Server Responses
+
+ Server responses are in three forms: status responses, server data,
+ and command continuation request. The information contained in a
+ server response, identified by "Contents:" in the response
+ descriptions below, is described by function, not by syntax. The
+ precise syntax of server responses is described in the Formal Syntax
+ section.
+
+ The client MUST be prepared to accept any response at all times.
+
+ Status responses can be tagged or untagged. Tagged status responses
+ indicate the completion result (OK, NO, or BAD status) of a client
+ command, and have a tag matching the command.
+
+ Some status responses, and all server data, are untagged. An
+ untagged response is indicated by the token "*" instead of a tag.
+ Untagged status responses indicate server greeting, or server status
+
+
+
+Crispin Standards Track [Page 62]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ that does not indicate the completion of a command (for example, an
+ impending system shutdown alert). For historical reasons, untagged
+ server data responses are also called "unsolicited data", although
+ strictly speaking, only unilateral server data is truly
+ "unsolicited".
+
+ Certain server data MUST be recorded by the client when it is
+ received; this is noted in the description of that data. Such data
+ conveys critical information which affects the interpretation of all
+ subsequent commands and responses (e.g., updates reflecting the
+ creation or destruction of messages).
+
+ Other server data SHOULD be recorded for later reference; if the
+ client does not need to record the data, or if recording the data has
+ no obvious purpose (e.g., a SEARCH response when no SEARCH command is
+ in progress), the data SHOULD be ignored.
+
+ An example of unilateral untagged server data occurs when the IMAP
+ connection is in the selected state. In the selected state, the
+ server checks the mailbox for new messages as part of command
+ execution. Normally, this is part of the execution of every command;
+ hence, a NOOP command suffices to check for new messages. If new
+ messages are found, the server sends untagged EXISTS and RECENT
+ responses reflecting the new size of the mailbox. Server
+ implementations that offer multiple simultaneous access to the same
+ mailbox SHOULD also send appropriate unilateral untagged FETCH and
+ EXPUNGE responses if another agent changes the state of any message
+ flags or expunges any messages.
+
+ Command continuation request responses use the token "+" instead of a
+ tag. These responses are sent by the server to indicate acceptance
+ of an incomplete client command and readiness for the remainder of
+ the command.
+
+7.1. Server Responses - Status Responses
+
+ Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD
+ can be tagged or untagged. PREAUTH and BYE are always untagged.
+
+ Status responses MAY include an OPTIONAL "response code". A response
+ code consists of data inside square brackets in the form of an atom,
+ possibly followed by a space and arguments. The response code
+ contains additional information or status codes for client software
+ beyond the OK/NO/BAD condition, and are defined when there is a
+ specific action that a client can take based upon the additional
+ information.
+
+
+
+
+
+Crispin Standards Track [Page 63]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The currently defined response codes are:
+
+ ALERT
+
+ The human-readable text contains a special alert that MUST be
+ presented to the user in a fashion that calls the user's
+ attention to the message.
+
+ BADCHARSET
+
+ Optionally followed by a parenthesized list of charsets. A
+ SEARCH failed because the given charset is not supported by
+ this implementation. If the optional list of charsets is
+ given, this lists the charsets that are supported by this
+ implementation.
+
+ CAPABILITY
+
+ Followed by a list of capabilities. This can appear in the
+ initial OK or PREAUTH response to transmit an initial
+ capabilities list. This makes it unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes this
+ response.
+
+ PARSE
+
+ The human-readable text represents an error in parsing the
+ [RFC-2822] header or [MIME-IMB] headers of a message in the
+ mailbox.
+
+ PERMANENTFLAGS
+
+ Followed by a parenthesized list of flags, indicates which of
+ the known flags the client can change permanently. Any flags
+ that are in the FLAGS untagged response, but not the
+ PERMANENTFLAGS list, can not be set permanently. If the client
+ attempts to STORE a flag that is not in the PERMANENTFLAGS
+ list, the server will either ignore the change or store the
+ state change for the remainder of the current session only.
+ The PERMANENTFLAGS list can also include the special flag \*,
+ which indicates that it is possible to create new keywords by
+ attempting to store those flags in the mailbox.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 64]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ READ-ONLY
+
+ The mailbox is selected read-only, or its access while selected
+ has changed from read-write to read-only.
+
+ READ-WRITE
+
+ The mailbox is selected read-write, or its access while
+ selected has changed from read-only to read-write.
+
+ TRYCREATE
+
+ An APPEND or COPY attempt is failing because the target mailbox
+ does not exist (as opposed to some other reason). This is a
+ hint to the client that the operation can succeed if the
+ mailbox is first created by the CREATE command.
+
+ UIDNEXT
+
+ Followed by a decimal number, indicates the next unique
+ identifier value. Refer to section 2.3.1.1 for more
+ information.
+
+ UIDVALIDITY
+
+ Followed by a decimal number, indicates the unique identifier
+ validity value. Refer to section 2.3.1.1 for more information.
+
+ UNSEEN
+
+ Followed by a decimal number, indicates the number of the first
+ message without the \Seen flag set.
+
+ Additional response codes defined by particular client or server
+ implementations SHOULD be prefixed with an "X" until they are
+ added to a revision of this protocol. Client implementations
+ SHOULD ignore response codes that they do not recognize.
+
+7.1.1. OK Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The OK response indicates an information message from the server.
+ When tagged, it indicates successful completion of the associated
+ command. The human-readable text MAY be presented to the user as
+ an information message. The untagged form indicates an
+
+
+
+
+Crispin Standards Track [Page 65]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ information-only message; the nature of the information MAY be
+ indicated by a response code.
+
+ The untagged form is also used as one of three possible greetings
+ at connection startup. It indicates that the connection is not
+ yet authenticated and that a LOGIN command is needed.
+
+ Example: S: * OK IMAP4rev1 server ready
+ C: A001 LOGIN fred blurdybloop
+ S: * OK [ALERT] System shutdown in 10 minutes
+ S: A001 OK LOGIN Completed
+
+
+7.1.2. NO Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The NO response indicates an operational error message from the
+ server. When tagged, it indicates unsuccessful completion of the
+ associated command. The untagged form indicates a warning; the
+ command can still complete successfully. The human-readable text
+ describes the condition.
+
+ Example: C: A222 COPY 1:2 owatagusiam
+ S: * NO Disk is 98% full, please delete unnecessary data
+ S: A222 OK COPY completed
+ C: A223 COPY 3:200 blurdybloop
+ S: * NO Disk is 98% full, please delete unnecessary data
+ S: * NO Disk is 99% full, please delete unnecessary data
+ S: A223 NO COPY failed: disk is full
+
+
+7.1.3. BAD Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The BAD response indicates an error message from the server. When
+ tagged, it reports a protocol-level error in the client's command;
+ the tag indicates the command that caused the error. The untagged
+ form indicates a protocol-level error for which the associated
+ command can not be determined; it can also indicate an internal
+ server failure. The human-readable text describes the condition.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 66]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: ...very long command line...
+ S: * BAD Command line too long
+ C: ...empty line...
+ S: * BAD Empty command line
+ C: A443 EXPUNGE
+ S: * BAD Disk crash, attempting salvage to a new disk!
+ S: * OK Salvage successful, no data lost
+ S: A443 OK Expunge completed
+
+
+7.1.4. PREAUTH Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The PREAUTH response is always untagged, and is one of three
+ possible greetings at connection startup. It indicates that the
+ connection has already been authenticated by external means; thus
+ no LOGIN command is needed.
+
+ Example: S: * PREAUTH IMAP4rev1 server logged in as Smith
+
+
+7.1.5. BYE Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The BYE response is always untagged, and indicates that the server
+ is about to close the connection. The human-readable text MAY be
+ displayed to the user in a status report by the client. The BYE
+ response is sent under one of four conditions:
+
+ 1) as part of a normal logout sequence. The server will close
+ the connection after sending the tagged OK response to the
+ LOGOUT command.
+
+ 2) as a panic shutdown announcement. The server closes the
+ connection immediately.
+
+ 3) as an announcement of an inactivity autologout. The server
+ closes the connection immediately.
+
+ 4) as one of three possible greetings at connection startup,
+ indicating that the server is not willing to accept a
+ connection from this client. The server closes the
+ connection immediately.
+
+
+
+
+Crispin Standards Track [Page 67]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The difference between a BYE that occurs as part of a normal
+ LOGOUT sequence (the first case) and a BYE that occurs because of
+ a failure (the other three cases) is that the connection closes
+ immediately in the failure case. In all cases the client SHOULD
+ continue to read response data from the server until the
+ connection is closed; this will ensure that any pending untagged
+ or completion responses are read and processed.
+
+ Example: S: * BYE Autologout; idle for too long
+
+7.2. Server Responses - Server and Mailbox Status
+
+ These responses are always untagged. This is how server and mailbox
+ status data are transmitted from the server to the client. Many of
+ these responses typically result from a command with the same name.
+
+7.2.1. CAPABILITY Response
+
+ Contents: capability listing
+
+ The CAPABILITY response occurs as a result of a CAPABILITY
+ command. The capability listing contains a space-separated
+ listing of capability names that the server supports. The
+ capability listing MUST include the atom "IMAP4rev1".
+
+ In addition, client and server implementations MUST implement the
+ STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+ capabilities. See the Security Considerations section for
+ important information.
+
+ A capability name which begins with "AUTH=" indicates that the
+ server supports that particular authentication mechanism.
+
+ The LOGINDISABLED capability indicates that the LOGIN command is
+ disabled, and that the server will respond with a tagged NO
+ response to any attempt to use the LOGIN command even if the user
+ name and password are valid. An IMAP client MUST NOT issue the
+ LOGIN command if the server advertises the LOGINDISABLED
+ capability.
+
+ Other capability names indicate that the server supports an
+ extension, revision, or amendment to the IMAP4rev1 protocol.
+ Server responses MUST conform to this document until the client
+ issues a command that uses the associated capability.
+
+ Capability names MUST either begin with "X" or be standard or
+ standards-track IMAP4rev1 extensions, revisions, or amendments
+ registered with IANA. A server MUST NOT offer unregistered or
+
+
+
+Crispin Standards Track [Page 68]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ non-standard capability names, unless such names are prefixed with
+ an "X".
+
+ Client implementations SHOULD NOT require any capability name
+ other than "IMAP4rev1", and MUST ignore any unknown capability
+ names.
+
+ A server MAY send capabilities automatically, by using the
+ CAPABILITY response code in the initial PREAUTH or OK responses,
+ and by sending an updated CAPABILITY response code in the tagged
+ OK response as part of a successful authentication. It is
+ unnecessary for a client to send a separate CAPABILITY command if
+ it recognizes these automatic capabilities.
+
+ Example: S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI XPIG-LATIN
+
+
+7.2.2. LIST Response
+
+ Contents: name attributes
+ hierarchy delimiter
+ name
+
+ The LIST response occurs as a result of a LIST command. It
+ returns a single name that matches the LIST specification. There
+ can be multiple LIST responses for a single LIST command.
+
+ Four name attributes are defined:
+
+ \Noinferiors
+ It is not possible for any child levels of hierarchy to exist
+ under this name; no child levels exist now and none can be
+ created in the future.
+
+ \Noselect
+ It is not possible to use this name as a selectable mailbox.
+
+ \Marked
+ The mailbox has been marked "interesting" by the server; the
+ mailbox probably contains messages that have been added since
+ the last time the mailbox was selected.
+
+ \Unmarked
+ The mailbox does not contain any additional messages since the
+ last time the mailbox was selected.
+
+
+
+
+
+
+Crispin Standards Track [Page 69]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If it is not feasible for the server to determine whether or not
+ the mailbox is "interesting", or if the name is a \Noselect name,
+ the server SHOULD NOT send either \Marked or \Unmarked.
+
+ The hierarchy delimiter is a character used to delimit levels of
+ hierarchy in a mailbox name. A client can use it to create child
+ mailboxes, and to search higher or lower levels of naming
+ hierarchy. All children of a top-level hierarchy node MUST use
+ the same separator character. A NIL hierarchy delimiter means
+ that no hierarchy exists; the name is a "flat" name.
+
+ The name represents an unambiguous left-to-right hierarchy, and
+ MUST be valid for use as a reference in LIST and LSUB commands.
+ Unless \Noselect is indicated, the name MUST also be valid as an
+ argument for commands, such as SELECT, that accept mailbox names.
+
+ Example: S: * LIST (\Noselect) "/" ~/Mail/foo
+
+
+7.2.3. LSUB Response
+
+ Contents: name attributes
+ hierarchy delimiter
+ name
+
+ The LSUB response occurs as a result of an LSUB command. It
+ returns a single name that matches the LSUB specification. There
+ can be multiple LSUB responses for a single LSUB command. The
+ data is identical in format to the LIST response.
+
+ Example: S: * LSUB () "." #news.comp.mail.misc
+
+
+7.2.4 STATUS Response
+
+ Contents: name
+ status parenthesized list
+
+ The STATUS response occurs as a result of an STATUS command. It
+ returns the mailbox name that matches the STATUS specification and
+ the requested mailbox status information.
+
+ Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 70]
+
+RFC 3501 IMAPv4 March 2003
+
+
+7.2.5. SEARCH Response
+
+ Contents: zero or more numbers
+
+ The SEARCH response occurs as a result of a SEARCH or UID SEARCH
+ command. The number(s) refer to those messages that match the
+ search criteria. For SEARCH, these are message sequence numbers;
+ for UID SEARCH, these are unique identifiers. Each number is
+ delimited by a space.
+
+ Example: S: * SEARCH 2 3 6
+
+
+7.2.6. FLAGS Response
+
+ Contents: flag parenthesized list
+
+ The FLAGS response occurs as a result of a SELECT or EXAMINE
+ command. The flag parenthesized list identifies the flags (at a
+ minimum, the system-defined flags) that are applicable for this
+ mailbox. Flags other than the system flags can also exist,
+ depending on server implementation.
+
+ The update from the FLAGS response MUST be recorded by the client.
+
+ Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+
+
+7.3. Server Responses - Mailbox Size
+
+ These responses are always untagged. This is how changes in the size
+ of the mailbox are transmitted from the server to the client.
+ Immediately following the "*" token is a number that represents a
+ message count.
+
+7.3.1. EXISTS Response
+
+ Contents: none
+
+ The EXISTS response reports the number of messages in the mailbox.
+ This response occurs as a result of a SELECT or EXAMINE command,
+ and if the size of the mailbox changes (e.g., new messages).
+
+ The update from the EXISTS response MUST be recorded by the
+ client.
+
+ Example: S: * 23 EXISTS
+
+
+
+
+Crispin Standards Track [Page 71]
+
+RFC 3501 IMAPv4 March 2003
+
+
+7.3.2. RECENT Response
+
+ Contents: none
+
+ The RECENT response reports the number of messages with the
+ \Recent flag set. This response occurs as a result of a SELECT or
+ EXAMINE command, and if the size of the mailbox changes (e.g., new
+ messages).
+
+ Note: It is not guaranteed that the message sequence
+ numbers of recent messages will be a contiguous range of
+ the highest n messages in the mailbox (where n is the
+ value reported by the RECENT response). Examples of
+ situations in which this is not the case are: multiple
+ clients having the same mailbox open (the first session
+ to be notified will see it as recent, others will
+ probably see it as non-recent), and when the mailbox is
+ re-ordered by a non-IMAP agent.
+
+ The only reliable way to identify recent messages is to
+ look at message flags to see which have the \Recent flag
+ set, or to do a SEARCH RECENT.
+
+ The update from the RECENT response MUST be recorded by the
+ client.
+
+ Example: S: * 5 RECENT
+
+
+7.4. Server Responses - Message Status
+
+ These responses are always untagged. This is how message data are
+ transmitted from the server to the client, often as a result of a
+ command with the same name. Immediately following the "*" token is a
+ number that represents a message sequence number.
+
+7.4.1. EXPUNGE Response
+
+ Contents: none
+
+ The EXPUNGE response reports that the specified message sequence
+ number has been permanently removed from the mailbox. The message
+ sequence number for each successive message in the mailbox is
+ immediately decremented by 1, and this decrement is reflected in
+ message sequence numbers in subsequent responses (including other
+ untagged EXPUNGE responses).
+
+
+
+
+
+Crispin Standards Track [Page 72]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The EXPUNGE response also decrements the number of messages in the
+ mailbox; it is not necessary to send an EXISTS response with the
+ new value.
+
+ As a result of the immediate decrement rule, message sequence
+ numbers that appear in a set of successive EXPUNGE responses
+ depend upon whether the messages are removed starting from lower
+ numbers to higher numbers, or from higher numbers to lower
+ numbers. For example, if the last 5 messages in a 9-message
+ mailbox are expunged, a "lower to higher" server will send five
+ untagged EXPUNGE responses for message sequence number 5, whereas
+ a "higher to lower server" will send successive untagged EXPUNGE
+ responses for message sequence numbers 9, 8, 7, 6, and 5.
+
+ An EXPUNGE response MUST NOT be sent when no command is in
+ progress, nor while responding to a FETCH, STORE, or SEARCH
+ command. This rule is necessary to prevent a loss of
+ synchronization of message sequence numbers between client and
+ server. A command is not "in progress" until the complete command
+ has been received; in particular, a command is not "in progress"
+ during the negotiation of command continuation.
+
+ Note: UID FETCH, UID STORE, and UID SEARCH are different
+ commands from FETCH, STORE, and SEARCH. An EXPUNGE
+ response MAY be sent during a UID command.
+
+ The update from the EXPUNGE response MUST be recorded by the
+ client.
+
+ Example: S: * 44 EXPUNGE
+
+
+7.4.2. FETCH Response
+
+ Contents: message data
+
+ The FETCH response returns data about a message to the client.
+ The data are pairs of data item names and their values in
+ parentheses. This response occurs as the result of a FETCH or
+ STORE command, as well as by unilateral server decision (e.g.,
+ flag updates).
+
+ The current data items are:
+
+ BODY
+ A form of BODYSTRUCTURE without extension data.
+
+
+
+
+
+Crispin Standards Track [Page 73]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BODY[<section>]<<origin octet>>
+ A string expressing the body contents of the specified section.
+ The string SHOULD be interpreted by the client according to the
+ content transfer encoding, body type, and subtype.
+
+ If the origin octet is specified, this string is a substring of
+ the entire body contents, starting at that origin octet. This
+ means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
+ truncated.
+
+ Note: The origin octet facility MUST NOT be used by a server
+ in a FETCH response unless the client specifically requested
+ it by means of a FETCH of a BODY[<section>]<<partial>> data
+ item.
+
+ 8-bit textual data is permitted if a [CHARSET] identifier is
+ part of the body parameter parenthesized list for this section.
+ Note that headers (part specifiers HEADER or MIME, or the
+ header portion of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
+ characters are not permitted in headers. Note also that the
+ [RFC-2822] delimiting blank line between the header and the
+ body is not affected by header line subsetting; the blank line
+ is always included as part of header data, except in the case
+ of a message which has no body and no blank line.
+
+ Non-textual data such as binary data MUST be transfer encoded
+ into a textual form, such as BASE64, prior to being sent to the
+ client. To derive the original binary data, the client MUST
+ decode the transfer encoded string.
+
+ BODYSTRUCTURE
+ A parenthesized list that describes the [MIME-IMB] body
+ structure of a message. This is computed by the server by
+ parsing the [MIME-IMB] header fields, defaulting various fields
+ as necessary.
+
+ For example, a simple text message of 48 lines and 2279 octets
+ can have a body structure of: ("TEXT" "PLAIN" ("CHARSET"
+ "US-ASCII") NIL NIL "7BIT" 2279 48)
+
+ Multiple parts are indicated by parenthesis nesting. Instead
+ of a body type as the first element of the parenthesized list,
+ there is a sequence of one or more nested body structures. The
+ second element of the parenthesized list is the multipart
+ subtype (mixed, digest, parallel, alternative, etc.).
+
+
+
+
+
+
+Crispin Standards Track [Page 74]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, a two part message consisting of a text and a
+ BASE64-encoded text attachment can have a body structure of:
+ (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
+ 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
+ "<960723163407.20117h@cac.washington.edu>" "Compiler diff"
+ "BASE64" 4554 73) "MIXED")
+
+ Extension data follows the multipart subtype. Extension data
+ is never returned with the BODY fetch, but can be returned with
+ a BODYSTRUCTURE fetch. Extension data, if present, MUST be in
+ the defined order. The extension data of a multipart body part
+ are in the following order:
+
+ body parameter parenthesized list
+ A parenthesized list of attribute/value pairs [e.g., ("foo"
+ "bar" "baz" "rag") where "bar" is the value of "foo", and
+ "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+ body disposition
+ A parenthesized list, consisting of a disposition type
+ string, followed by a parenthesized list of disposition
+ attribute/value pairs as defined in [DISPOSITION].
+
+ body language
+ A string or parenthesized list giving the body language
+ value as defined in [LANGUAGE-TAGS].
+
+ body location
+ A string list giving the body content URI as defined in
+ [LOCATION].
+
+ Any following extension data are not yet defined in this
+ version of the protocol. Such extension data can consist of
+ zero or more NILs, strings, numbers, or potentially nested
+ parenthesized lists of such data. Client implementations that
+ do a BODYSTRUCTURE fetch MUST be prepared to accept such
+ extension data. Server implementations MUST NOT send such
+ extension data until it has been defined by a revision of this
+ protocol.
+
+ The basic fields of a non-multipart body part are in the
+ following order:
+
+ body type
+ A string giving the content media type name as defined in
+ [MIME-IMB].
+
+
+
+
+
+Crispin Standards Track [Page 75]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ body subtype
+ A string giving the content subtype name as defined in
+ [MIME-IMB].
+
+ body parameter parenthesized list
+ A parenthesized list of attribute/value pairs [e.g., ("foo"
+ "bar" "baz" "rag") where "bar" is the value of "foo" and
+ "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+ body id
+ A string giving the content id as defined in [MIME-IMB].
+
+ body description
+ A string giving the content description as defined in
+ [MIME-IMB].
+
+ body encoding
+ A string giving the content transfer encoding as defined in
+ [MIME-IMB].
+
+ body size
+ A number giving the size of the body in octets. Note that
+ this size is the size in its transfer encoding and not the
+ resulting size after any decoding.
+
+ A body type of type MESSAGE and subtype RFC822 contains,
+ immediately after the basic fields, the envelope structure,
+ body structure, and size in text lines of the encapsulated
+ message.
+
+ A body type of type TEXT contains, immediately after the basic
+ fields, the size of the body in text lines. Note that this
+ size is the size in its content transfer encoding and not the
+ resulting size after any decoding.
+
+ Extension data follows the basic fields and the type-specific
+ fields listed above. Extension data is never returned with the
+ BODY fetch, but can be returned with a BODYSTRUCTURE fetch.
+ Extension data, if present, MUST be in the defined order.
+
+ The extension data of a non-multipart body part are in the
+ following order:
+
+ body MD5
+ A string giving the body MD5 value as defined in [MD5].
+
+
+
+
+
+
+Crispin Standards Track [Page 76]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ body disposition
+ A parenthesized list with the same content and function as
+ the body disposition for a multipart body part.
+
+ body language
+ A string or parenthesized list giving the body language
+ value as defined in [LANGUAGE-TAGS].
+
+ body location
+ A string list giving the body content URI as defined in
+ [LOCATION].
+
+ Any following extension data are not yet defined in this
+ version of the protocol, and would be as described above under
+ multipart extension data.
+
+ ENVELOPE
+ A parenthesized list that describes the envelope structure of a
+ message. This is computed by the server by parsing the
+ [RFC-2822] header into the component parts, defaulting various
+ fields as necessary.
+
+ The fields of the envelope structure are in the following
+ order: date, subject, from, sender, reply-to, to, cc, bcc,
+ in-reply-to, and message-id. The date, subject, in-reply-to,
+ and message-id fields are strings. The from, sender, reply-to,
+ to, cc, and bcc fields are parenthesized lists of address
+ structures.
+
+ An address structure is a parenthesized list that describes an
+ electronic mail address. The fields of an address structure
+ are in the following order: personal name, [SMTP]
+ at-domain-list (source route), mailbox name, and host name.
+
+ [RFC-2822] group syntax is indicated by a special form of
+ address structure in which the host name field is NIL. If the
+ mailbox name field is also NIL, this is an end of group marker
+ (semi-colon in RFC 822 syntax). If the mailbox name field is
+ non-NIL, this is a start of group marker, and the mailbox name
+ field holds the group name phrase.
+
+ If the Date, Subject, In-Reply-To, and Message-ID header lines
+ are absent in the [RFC-2822] header, the corresponding member
+ of the envelope is NIL; if these header lines are present but
+ empty the corresponding member of the envelope is the empty
+ string.
+
+
+
+
+
+Crispin Standards Track [Page 77]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Note: some servers may return a NIL envelope member in the
+ "present but empty" case. Clients SHOULD treat NIL and
+ empty string as identical.
+
+ Note: [RFC-2822] requires that all messages have a valid
+ Date header. Therefore, the date member in the envelope can
+ not be NIL or the empty string.
+
+ Note: [RFC-2822] requires that the In-Reply-To and
+ Message-ID headers, if present, have non-empty content.
+ Therefore, the in-reply-to and message-id members in the
+ envelope can not be the empty string.
+
+ If the From, To, cc, and bcc header lines are absent in the
+ [RFC-2822] header, or are present but empty, the corresponding
+ member of the envelope is NIL.
+
+ If the Sender or Reply-To lines are absent in the [RFC-2822]
+ header, or are present but empty, the server sets the
+ corresponding member of the envelope to be the same value as
+ the from member (the client is not expected to know to do
+ this).
+
+ Note: [RFC-2822] requires that all messages have a valid
+ From header. Therefore, the from, sender, and reply-to
+ members in the envelope can not be NIL.
+
+ FLAGS
+ A parenthesized list of flags that are set for this message.
+
+ INTERNALDATE
+ A string representing the internal date of the message.
+
+ RFC822
+ Equivalent to BODY[].
+
+ RFC822.HEADER
+ Equivalent to BODY[HEADER]. Note that this did not result in
+ \Seen being set, because RFC822.HEADER response data occurs as
+ a result of a FETCH of RFC822.HEADER. BODY[HEADER] response
+ data occurs as a result of a FETCH of BODY[HEADER] (which sets
+ \Seen) or BODY.PEEK[HEADER] (which does not set \Seen).
+
+ RFC822.SIZE
+ A number expressing the [RFC-2822] size of the message.
+
+
+
+
+
+
+Crispin Standards Track [Page 78]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ RFC822.TEXT
+ Equivalent to BODY[TEXT].
+
+ UID
+ A number expressing the unique identifier of the message.
+
+
+ Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
+
+
+7.5. Server Responses - Command Continuation Request
+
+ The command continuation request response is indicated by a "+" token
+ instead of a tag. This form of response indicates that the server is
+ ready to accept the continuation of a command from the client. The
+ remainder of this response is a line of text.
+
+ This response is used in the AUTHENTICATE command to transmit server
+ data to the client, and request additional client data. This
+ response is also used if an argument to any command is a literal.
+
+ The client is not permitted to send the octets of the literal unless
+ the server indicates that it is expected. This permits the server to
+ process commands and reject errors on a line-by-line basis. The
+ remainder of the command, including the CRLF that terminates a
+ command, follows the octets of the literal. If there are any
+ additional command arguments, the literal octets are followed by a
+ space and those arguments.
+
+ Example: C: A001 LOGIN {11}
+ S: + Ready for additional command text
+ C: FRED FOOBAR {7}
+ S: + Ready for additional command text
+ C: fat man
+ S: A001 OK LOGIN completed
+ C: A044 BLURDYBLOOP {102856}
+ S: A044 BAD No such command as "BLURDYBLOOP"
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 79]
+
+RFC 3501 IMAPv4 March 2003
+
+
+8. Sample IMAP4rev1 connection
+
+ The following is a transcript of an IMAP4rev1 connection. A long
+ line in this sample is broken for editorial clarity.
+
+S: * OK IMAP4rev1 Service Ready
+C: a001 login mrc secret
+S: a001 OK LOGIN completed
+C: a002 select inbox
+S: * 18 EXISTS
+S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+S: * 2 RECENT
+S: * OK [UNSEEN 17] Message 17 is the first unseen message
+S: * OK [UIDVALIDITY 3857529045] UIDs valid
+S: a002 OK [READ-WRITE] SELECT completed
+C: a003 fetch 12 full
+S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
+ RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
+ "IMAP4rev1 WG mtg summary and minutes"
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ ((NIL NIL "imap" "cac.washington.edu"))
+ ((NIL NIL "minutes" "CNRI.Reston.VA.US")
+ ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL
+ "<B27397-0100000@cac.washington.edu>")
+ BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028
+ 92))
+S: a003 OK FETCH completed
+C: a004 fetch 12 body[header]
+S: * 12 FETCH (BODY[HEADER] {342}
+S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
+S: From: Terry Gray <gray@cac.washington.edu>
+S: Subject: IMAP4rev1 WG mtg summary and minutes
+S: To: imap@cac.washington.edu
+S: cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@MIT.EDU>
+S: Message-Id: <B27397-0100000@cac.washington.edu>
+S: MIME-Version: 1.0
+S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+S:
+S: )
+S: a004 OK FETCH completed
+C: a005 store 12 +flags \deleted
+S: * 12 FETCH (FLAGS (\Seen \Deleted))
+S: a005 OK +FLAGS completed
+C: a006 logout
+S: * BYE IMAP4rev1 server terminating connection
+S: a006 OK LOGOUT completed
+
+
+
+Crispin Standards Track [Page 80]
+
+RFC 3501 IMAPv4 March 2003
+
+
+9. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ In the case of alternative or optional rules in which a later rule
+ overlaps an earlier rule, the rule which is listed earlier MUST take
+ priority. For example, "\Seen" when parsed as a flag is the \Seen
+ flag name and not a flag-extension, even though "\Seen" can be parsed
+ as a flag-extension. Some, but not all, instances of this rule are
+ noted below.
+
+ Note: [ABNF] rules MUST be followed strictly; in
+ particular:
+
+ (1) Except as noted otherwise, all alphabetic characters
+ are case-insensitive. The use of upper or lower case
+ characters to define token strings is for editorial clarity
+ only. Implementations MUST accept these strings in a
+ case-insensitive fashion.
+
+ (2) In all cases, SP refers to exactly one space. It is
+ NOT permitted to substitute TAB, insert additional spaces,
+ or otherwise treat SP as being equivalent to LWSP.
+
+ (3) The ASCII NUL character, %x00, MUST NOT be used at any
+ time.
+
+address = "(" addr-name SP addr-adl SP addr-mailbox SP
+ addr-host ")"
+
+addr-adl = nstring
+ ; Holds route from [RFC-2822] route-addr if
+ ; non-NIL
+
+addr-host = nstring
+ ; NIL indicates [RFC-2822] group syntax.
+ ; Otherwise, holds [RFC-2822] domain name
+
+addr-mailbox = nstring
+ ; NIL indicates end of [RFC-2822] group; if
+ ; non-NIL and addr-host is NIL, holds
+ ; [RFC-2822] group name.
+ ; Otherwise, holds [RFC-2822] local-part
+ ; after removing [RFC-2822] quoting
+
+
+
+
+
+
+Crispin Standards Track [Page 81]
+
+RFC 3501 IMAPv4 March 2003
+
+
+addr-name = nstring
+ ; If non-NIL, holds phrase from [RFC-2822]
+ ; mailbox after removing [RFC-2822] quoting
+
+append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
+ literal
+
+astring = 1*ASTRING-CHAR / string
+
+ASTRING-CHAR = ATOM-CHAR / resp-specials
+
+atom = 1*ATOM-CHAR
+
+ATOM-CHAR = <any CHAR except atom-specials>
+
+atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards /
+ quoted-specials / resp-specials
+
+authenticate = "AUTHENTICATE" SP auth-type *(CRLF base64)
+
+auth-type = atom
+ ; Defined by [SASL]
+
+base64 = *(4base64-char) [base64-terminal]
+
+base64-char = ALPHA / DIGIT / "+" / "/"
+ ; Case-sensitive
+
+base64-terminal = (2base64-char "==") / (3base64-char "=")
+
+body = "(" (body-type-1part / body-type-mpart) ")"
+
+body-extension = nstring / number /
+ "(" body-extension *(SP body-extension) ")"
+ ; Future expansion. Client implementations
+ ; MUST accept body-extension fields. Server
+ ; implementations MUST NOT generate
+ ; body-extension fields except as defined by
+ ; future standard or standards-track
+ ; revisions of this specification.
+
+body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
+ [SP body-fld-loc *(SP body-extension)]]]
+ ; MUST NOT be returned on non-extensible
+ ; "BODY" fetch
+
+
+
+
+
+
+Crispin Standards Track [Page 82]
+
+RFC 3501 IMAPv4 March 2003
+
+
+body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang
+ [SP body-fld-loc *(SP body-extension)]]]
+ ; MUST NOT be returned on non-extensible
+ ; "BODY" fetch
+
+body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP
+ body-fld-enc SP body-fld-octets
+
+body-fld-desc = nstring
+
+body-fld-dsp = "(" string SP body-fld-param ")" / nil
+
+body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
+ "QUOTED-PRINTABLE") DQUOTE) / string
+
+body-fld-id = nstring
+
+body-fld-lang = nstring / "(" string *(SP string) ")"
+
+body-fld-loc = nstring
+
+body-fld-lines = number
+
+body-fld-md5 = nstring
+
+body-fld-octets = number
+
+body-fld-param = "(" string SP string *(SP string SP string) ")" / nil
+
+body-type-1part = (body-type-basic / body-type-msg / body-type-text)
+ [SP body-ext-1part]
+
+body-type-basic = media-basic SP body-fields
+ ; MESSAGE subtype MUST NOT be "RFC822"
+
+body-type-mpart = 1*body SP media-subtype
+ [SP body-ext-mpart]
+
+body-type-msg = media-message SP body-fields SP envelope
+ SP body SP body-fld-lines
+
+body-type-text = media-text SP body-fields SP body-fld-lines
+
+capability = ("AUTH=" auth-type) / atom
+ ; New capabilities MUST begin with "X" or be
+ ; registered with IANA as standard or
+ ; standards-track
+
+
+
+
+Crispin Standards Track [Page 83]
+
+RFC 3501 IMAPv4 March 2003
+
+
+capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev1"
+ *(SP capability)
+ ; Servers MUST implement the STARTTLS, AUTH=PLAIN,
+ ; and LOGINDISABLED capabilities
+ ; Servers which offer RFC 1730 compatibility MUST
+ ; list "IMAP4" as the first capability.
+
+CHAR8 = %x01-ff
+ ; any OCTET except NUL, %x00
+
+command = tag SP (command-any / command-auth / command-nonauth /
+ command-select) CRLF
+ ; Modal based on state
+
+command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command
+ ; Valid in all states
+
+command-auth = append / create / delete / examine / list / lsub /
+ rename / select / status / subscribe / unsubscribe
+ ; Valid only in Authenticated or Selected state
+
+command-nonauth = login / authenticate / "STARTTLS"
+ ; Valid only when in Not Authenticated state
+
+command-select = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
+ uid / search
+ ; Valid only when in Selected state
+
+continue-req = "+" SP (resp-text / base64) CRLF
+
+copy = "COPY" SP sequence-set SP mailbox
+
+create = "CREATE" SP mailbox
+ ; Use of INBOX gives a NO error
+
+date = date-text / DQUOTE date-text DQUOTE
+
+date-day = 1*2DIGIT
+ ; Day of month
+
+date-day-fixed = (SP DIGIT) / 2DIGIT
+ ; Fixed-format version of date-day
+
+date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
+ "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
+
+date-text = date-day "-" date-month "-" date-year
+
+
+
+
+Crispin Standards Track [Page 84]
+
+RFC 3501 IMAPv4 March 2003
+
+
+date-year = 4DIGIT
+
+date-time = DQUOTE date-day-fixed "-" date-month "-" date-year
+ SP time SP zone DQUOTE
+
+delete = "DELETE" SP mailbox
+ ; Use of INBOX gives a NO error
+
+digit-nz = %x31-39
+ ; 1-9
+
+envelope = "(" env-date SP env-subject SP env-from SP
+ env-sender SP env-reply-to SP env-to SP env-cc SP
+ env-bcc SP env-in-reply-to SP env-message-id ")"
+
+env-bcc = "(" 1*address ")" / nil
+
+env-cc = "(" 1*address ")" / nil
+
+env-date = nstring
+
+env-from = "(" 1*address ")" / nil
+
+env-in-reply-to = nstring
+
+env-message-id = nstring
+
+env-reply-to = "(" 1*address ")" / nil
+
+env-sender = "(" 1*address ")" / nil
+
+env-subject = nstring
+
+env-to = "(" 1*address ")" / nil
+
+examine = "EXAMINE" SP mailbox
+
+fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
+ fetch-att / "(" fetch-att *(SP fetch-att) ")")
+
+fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
+ "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
+ "BODY" ["STRUCTURE"] / "UID" /
+ "BODY" section ["<" number "." nz-number ">"] /
+ "BODY.PEEK" section ["<" number "." nz-number ">"]
+
+
+
+
+
+
+Crispin Standards Track [Page 85]
+
+RFC 3501 IMAPv4 March 2003
+
+
+flag = "\Answered" / "\Flagged" / "\Deleted" /
+ "\Seen" / "\Draft" / flag-keyword / flag-extension
+ ; Does not include "\Recent"
+
+flag-extension = "\" atom
+ ; Future expansion. Client implementations
+ ; MUST accept flag-extension flags. Server
+ ; implementations MUST NOT generate
+ ; flag-extension flags except as defined by
+ ; future standard or standards-track
+ ; revisions of this specification.
+
+flag-fetch = flag / "\Recent"
+
+flag-keyword = atom
+
+flag-list = "(" [flag *(SP flag)] ")"
+
+flag-perm = flag / "\*"
+
+greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF
+
+header-fld-name = astring
+
+header-list = "(" header-fld-name *(SP header-fld-name) ")"
+
+list = "LIST" SP mailbox SP list-mailbox
+
+list-mailbox = 1*list-char / string
+
+list-char = ATOM-CHAR / list-wildcards / resp-specials
+
+list-wildcards = "%" / "*"
+
+literal = "{" number "}" CRLF *CHAR8
+ ; Number represents the number of CHAR8s
+
+login = "LOGIN" SP userid SP password
+
+lsub = "LSUB" SP mailbox SP list-mailbox
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 86]
+
+RFC 3501 IMAPv4 March 2003
+
+
+mailbox = "INBOX" / astring
+ ; INBOX is case-insensitive. All case variants of
+ ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX
+ ; not as an astring. An astring which consists of
+ ; the case-insensitive sequence "I" "N" "B" "O" "X"
+ ; is considered to be INBOX and not an astring.
+ ; Refer to section 5.1 for further
+ ; semantic details of mailbox names.
+
+mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list /
+ "LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
+ "STATUS" SP mailbox SP "(" [status-att-list] ")" /
+ number SP "EXISTS" / number SP "RECENT"
+
+mailbox-list = "(" [mbx-list-flags] ")" SP
+ (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
+
+mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag
+ *(SP mbx-list-oflag) /
+ mbx-list-oflag *(SP mbx-list-oflag)
+
+mbx-list-oflag = "\Noinferiors" / flag-extension
+ ; Other flags; multiple possible per LIST response
+
+mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked"
+ ; Selectability flags; only one per LIST response
+
+media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" /
+ "MESSAGE" / "VIDEO") DQUOTE) / string) SP
+ media-subtype
+ ; Defined in [MIME-IMT]
+
+media-message = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
+ ; Defined in [MIME-IMT]
+
+media-subtype = string
+ ; Defined in [MIME-IMT]
+
+media-text = DQUOTE "TEXT" DQUOTE SP media-subtype
+ ; Defined in [MIME-IMT]
+
+message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))
+
+msg-att = "(" (msg-att-dynamic / msg-att-static)
+ *(SP (msg-att-dynamic / msg-att-static)) ")"
+
+msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
+ ; MAY change for a message
+
+
+
+Crispin Standards Track [Page 87]
+
+RFC 3501 IMAPv4 March 2003
+
+
+msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
+ "RFC822" [".HEADER" / ".TEXT"] SP nstring /
+ "RFC822.SIZE" SP number /
+ "BODY" ["STRUCTURE"] SP body /
+ "BODY" section ["<" number ">"] SP nstring /
+ "UID" SP uniqueid
+ ; MUST NOT change for a message
+
+nil = "NIL"
+
+nstring = string / nil
+
+number = 1*DIGIT
+ ; Unsigned 32-bit integer
+ ; (0 <= n < 4,294,967,296)
+
+nz-number = digit-nz *DIGIT
+ ; Non-zero unsigned 32-bit integer
+ ; (0 < n < 4,294,967,296)
+
+password = astring
+
+quoted = DQUOTE *QUOTED-CHAR DQUOTE
+
+QUOTED-CHAR = <any TEXT-CHAR except quoted-specials> /
+ "\" quoted-specials
+
+quoted-specials = DQUOTE / "\"
+
+rename = "RENAME" SP mailbox SP mailbox
+ ; Use of INBOX as a destination gives a NO error
+
+response = *(continue-req / response-data) response-done
+
+response-data = "*" SP (resp-cond-state / resp-cond-bye /
+ mailbox-data / message-data / capability-data) CRLF
+
+response-done = response-tagged / response-fatal
+
+response-fatal = "*" SP resp-cond-bye CRLF
+ ; Server closes connection immediately
+
+response-tagged = tag SP resp-cond-state CRLF
+
+resp-cond-auth = ("OK" / "PREAUTH") SP resp-text
+ ; Authentication condition
+
+
+
+
+
+Crispin Standards Track [Page 88]
+
+RFC 3501 IMAPv4 March 2003
+
+
+resp-cond-bye = "BYE" SP resp-text
+
+resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
+ ; Status condition
+
+resp-specials = "]"
+
+resp-text = ["[" resp-text-code "]" SP] text
+
+resp-text-code = "ALERT" /
+ "BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
+ capability-data / "PARSE" /
+ "PERMANENTFLAGS" SP "("
+ [flag-perm *(SP flag-perm)] ")" /
+ "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
+ "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
+ "UNSEEN" SP nz-number /
+ atom [SP 1*<any TEXT-CHAR except "]">]
+
+search = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
+ ; CHARSET argument to MUST be registered with IANA
+
+search-key = "ALL" / "ANSWERED" / "BCC" SP astring /
+ "BEFORE" SP date / "BODY" SP astring /
+ "CC" SP astring / "DELETED" / "FLAGGED" /
+ "FROM" SP astring / "KEYWORD" SP flag-keyword /
+ "NEW" / "OLD" / "ON" SP date / "RECENT" / "SEEN" /
+ "SINCE" SP date / "SUBJECT" SP astring /
+ "TEXT" SP astring / "TO" SP astring /
+ "UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
+ "UNKEYWORD" SP flag-keyword / "UNSEEN" /
+ ; Above this line were in [IMAP2]
+ "DRAFT" / "HEADER" SP header-fld-name SP astring /
+ "LARGER" SP number / "NOT" SP search-key /
+ "OR" SP search-key SP search-key /
+ "SENTBEFORE" SP date / "SENTON" SP date /
+ "SENTSINCE" SP date / "SMALLER" SP number /
+ "UID" SP sequence-set / "UNDRAFT" / sequence-set /
+ "(" search-key *(SP search-key) ")"
+
+section = "[" [section-spec] "]"
+
+section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
+ "TEXT"
+ ; top-level or MESSAGE/RFC822 part
+
+section-part = nz-number *("." nz-number)
+ ; body part nesting
+
+
+
+Crispin Standards Track [Page 89]
+
+RFC 3501 IMAPv4 March 2003
+
+
+section-spec = section-msgtext / (section-part ["." section-text])
+
+section-text = section-msgtext / "MIME"
+ ; text other than actual body part (headers, etc.)
+
+select = "SELECT" SP mailbox
+
+seq-number = nz-number / "*"
+ ; message sequence number (COPY, FETCH, STORE
+ ; commands) or unique identifier (UID COPY,
+ ; UID FETCH, UID STORE commands).
+ ; * represents the largest number in use. In
+ ; the case of message sequence numbers, it is
+ ; the number of messages in a non-empty mailbox.
+ ; In the case of unique identifiers, it is the
+ ; unique identifier of the last message in the
+ ; mailbox or, if the mailbox is empty, the
+ ; mailbox's current UIDNEXT value.
+ ; The server should respond with a tagged BAD
+ ; response to a command that uses a message
+ ; sequence number greater than the number of
+ ; messages in the selected mailbox. This
+ ; includes "*" if the selected mailbox is empty.
+
+seq-range = seq-number ":" seq-number
+ ; two seq-number values and all values between
+ ; these two regardless of order.
+ ; Example: 2:4 and 4:2 are equivalent and indicate
+ ; values 2, 3, and 4.
+ ; Example: a unique identifier sequence range of
+ ; 3291:* includes the UID of the last message in
+ ; the mailbox, even if that value is less than 3291.
+
+sequence-set = (seq-number / seq-range) *("," sequence-set)
+ ; set of seq-number values, regardless of order.
+ ; Servers MAY coalesce overlaps and/or execute the
+ ; sequence in any order.
+ ; Example: a message sequence number set of
+ ; 2,4:7,9,12:* for a mailbox with 15 messages is
+ ; equivalent to 2,4,5,6,7,9,12,13,14,15
+ ; Example: a message sequence number set of *:4,5:7
+ ; for a mailbox with 10 messages is equivalent to
+ ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
+ ; overlap coalesced to be 4,5,6,7,8,9,10.
+
+status = "STATUS" SP mailbox SP
+ "(" status-att *(SP status-att) ")"
+
+
+
+
+Crispin Standards Track [Page 90]
+
+RFC 3501 IMAPv4 March 2003
+
+
+status-att = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
+ "UNSEEN"
+
+status-att-list = status-att SP number *(SP status-att SP number)
+
+store = "STORE" SP sequence-set SP store-att-flags
+
+store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
+ (flag-list / (flag *(SP flag)))
+
+string = quoted / literal
+
+subscribe = "SUBSCRIBE" SP mailbox
+
+tag = 1*<any ASTRING-CHAR except "+">
+
+text = 1*TEXT-CHAR
+
+TEXT-CHAR = <any CHAR except CR and LF>
+
+time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
+ ; Hours minutes seconds
+
+uid = "UID" SP (copy / fetch / search / store)
+ ; Unique identifiers used instead of message
+ ; sequence numbers
+
+uniqueid = nz-number
+ ; Strictly ascending
+
+unsubscribe = "UNSUBSCRIBE" SP mailbox
+
+userid = astring
+
+x-command = "X" atom <experimental command arguments>
+
+zone = ("+" / "-") 4DIGIT
+ ; Signed four-digit value of hhmm representing
+ ; hours and minutes east of Greenwich (that is,
+ ; the amount that the given time differs from
+ ; Universal Time). Subtracting the timezone
+ ; from the given time will give the UT form.
+ ; The Universal Time zone is "+0000".
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 91]
+
+RFC 3501 IMAPv4 March 2003
+
+
+10. Author's Note
+
+ This document is a revision or rewrite of earlier documents, and
+ supercedes the protocol specification in those documents: RFC 2060,
+ RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.
+
+11. Security Considerations
+
+ IMAP4rev1 protocol transactions, including electronic mail data, are
+ sent in the clear over the network unless protection from snooping is
+ negotiated. This can be accomplished either by the use of STARTTLS,
+ negotiated privacy protection in the AUTHENTICATE command, or some
+ other protection mechanism.
+
+11.1. STARTTLS Security Considerations
+
+ The specification of the STARTTLS command and LOGINDISABLED
+ capability in this document replaces that in [IMAP-TLS]. [IMAP-TLS]
+ remains normative for the PLAIN [SASL] authenticator.
+
+ IMAP client and server implementations MUST implement the
+ TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite, and SHOULD implement the
+ TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
+ important as it assures that any two compliant implementations can be
+ configured to interoperate. All other cipher suites are OPTIONAL.
+ Note that this is a change from section 2.1 of [IMAP-TLS].
+
+ During the [TLS] negotiation, the client MUST check its understanding
+ of the server hostname against the server's identity as presented in
+ the server Certificate message, in order to prevent man-in-the-middle
+ attacks. If the match fails, the client SHOULD either ask for
+ explicit user confirmation, or terminate the connection and indicate
+ that the server's identity is suspect. Matching is performed
+ according to these rules:
+
+ The client MUST use the server hostname it used to open the
+ connection as the value to compare against the server name
+ as expressed in the server certificate. The client MUST
+ NOT use any form of the server hostname derived from an
+ insecure remote source (e.g., insecure DNS lookup). CNAME
+ canonicalization is not done.
+
+ If a subjectAltName extension of type dNSName is present in
+ the certificate, it SHOULD be used as the source of the
+ server's identity.
+
+ Matching is case-insensitive.
+
+
+
+
+Crispin Standards Track [Page 92]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A "*" wildcard character MAY be used as the left-most name
+ component in the certificate. For example, *.example.com
+ would match a.example.com, foo.example.com, etc. but would
+ not match example.com.
+
+ If the certificate contains multiple names (e.g., more than
+ one dNSName field), then a match with any one of the fields
+ is considered acceptable.
+
+ Both the client and server MUST check the result of the STARTTLS
+ command and subsequent [TLS] negotiation to see whether acceptable
+ authentication or privacy was achieved.
+
+11.2. Other Security Considerations
+
+ A server error message for an AUTHENTICATE command which fails due to
+ invalid credentials SHOULD NOT detail why the credentials are
+ invalid.
+
+ Use of the LOGIN command sends passwords in the clear. This can be
+ avoided by using the AUTHENTICATE command with a [SASL] mechanism
+ that does not use plaintext passwords, by first negotiating
+ encryption via STARTTLS or some other protection mechanism.
+
+ A server implementation MUST implement a configuration that, at the
+ time of authentication, requires:
+ (1) The STARTTLS command has been negotiated.
+ OR
+ (2) Some other mechanism that protects the session from password
+ snooping has been provided.
+ OR
+ (3) The following measures are in place:
+ (a) The LOGINDISABLED capability is advertised, and [SASL]
+ mechanisms (such as PLAIN) using plaintext passwords are NOT
+ advertised in the CAPABILITY list.
+ AND
+ (b) The LOGIN command returns an error even if the password is
+ correct.
+ AND
+ (c) The AUTHENTICATE command returns an error with all [SASL]
+ mechanisms that use plaintext passwords, even if the password
+ is correct.
+
+ A server error message for a failing LOGIN command SHOULD NOT specify
+ that the user name, as opposed to the password, is invalid.
+
+ A server SHOULD have mechanisms in place to limit or delay failed
+ AUTHENTICATE/LOGIN attempts.
+
+
+
+Crispin Standards Track [Page 93]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Additional security considerations are discussed in the section
+ discussing the AUTHENTICATE and LOGIN commands.
+
+12. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ As this specification revises the STARTTLS and LOGINDISABLED
+ extensions previously defined in [IMAP-TLS], the registry will be
+ updated accordingly.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 94]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Appendices
+
+A. Normative References
+
+ The following documents contain definitions or specifications that
+ are necessary to understand this document properly:
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234,
+ November 1997.
+
+ [ANONYMOUS] Newman, C., "Anonymous SASL Mechanism", RFC
+ 2245, November 1997.
+
+ [CHARSET] Freed, N. and J. Postel, "IANA Character Set
+ Registration Procedures", RFC 2978, October
+ 2000.
+
+ [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest
+ Authentication as a SASL Mechanism", RFC 2831,
+ May 2000.
+
+ [DISPOSITION] Troost, R., Dorner, S. and K. Moore,
+ "Communicating Presentation Information in
+ Internet Messages: The Content-Disposition
+ Header", RFC 2183, August 1997.
+
+ [IMAP-TLS] Newman, C., "Using TLS with IMAP, POP3 and
+ ACAP", RFC 2595, June 1999.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to
+ Indicate Requirement Levels", BCP 14, RFC 2119,
+ March 1997.
+
+ [LANGUAGE-TAGS] Alvestrand, H., "Tags for the Identification of
+ Languages", BCP 47, RFC 3066, January 2001.
+
+ [LOCATION] Palme, J., Hopmann, A. and N. Shelness, "MIME
+ Encapsulation of Aggregate Documents, such as
+ HTML (MHTML)", RFC 2557, March 1999.
+
+ [MD5] Myers, J. and M. Rose, "The Content-MD5 Header
+ Field", RFC 1864, October 1995.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 95]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ [MIME-HDRS] Moore, K., "MIME (Multipurpose Internet Mail
+ Extensions) Part Three: Message Header
+ Extensions for Non-ASCII Text", RFC 2047,
+ November 1996.
+
+ [MIME-IMB] Freed, N. and N. Borenstein, "MIME
+ (Multipurpose Internet Mail Extensions) Part
+ One: Format of Internet Message Bodies", RFC
+ 2045, November 1996.
+
+ [MIME-IMT] Freed, N. and N. Borenstein, "MIME
+ (Multipurpose Internet Mail Extensions) Part
+ Two: Media Types", RFC 2046, November 1996.
+
+ [RFC-2822] Resnick, P., "Internet Message Format", RFC
+ 2822, April 2001.
+
+ [SASL] Myers, J., "Simple Authentication and Security
+ Layer (SASL)", RFC 2222, October 1997.
+
+ [TLS] Dierks, T. and C. Allen, "The TLS Protocol
+ Version 1.0", RFC 2246, January 1999.
+
+ [UTF-7] Goldsmith, D. and M. Davis, "UTF-7: A Mail-Safe
+ Transformation Format of Unicode", RFC 2152,
+ May 1997.
+
+ The following documents describe quality-of-implementation issues
+ that should be carefully considered when implementing this protocol:
+
+ [IMAP-IMPLEMENTATION] Leiba, B., "IMAP Implementation
+ Recommendations", RFC 2683, September 1999.
+
+ [IMAP-MULTIACCESS] Gahrns, M., "IMAP4 Multi-Accessed Mailbox
+ Practice", RFC 2180, July 1997.
+
+A.1 Informative References
+
+ The following documents describe related protocols:
+
+ [IMAP-DISC] Austein, R., "Synchronization Operations for
+ Disconnected IMAP4 Clients", Work in Progress.
+
+ [IMAP-MODEL] Crispin, M., "Distributed Electronic Mail
+ Models in IMAP4", RFC 1733, December 1994.
+
+
+
+
+
+
+Crispin Standards Track [Page 96]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244,
+ November 1997.
+
+ [SMTP] Klensin, J., "Simple Mail Transfer Protocol",
+ STD 10, RFC 2821, April 2001.
+
+ The following documents are historical or describe historical aspects
+ of this protocol:
+
+ [IMAP-COMPAT] Crispin, M., "IMAP4 Compatibility with
+ IMAP2bis", RFC 2061, December 1996.
+
+ [IMAP-HISTORICAL] Crispin, M., "IMAP4 Compatibility with IMAP2
+ and IMAP2bis", RFC 1732, December 1994.
+
+ [IMAP-OBSOLETE] Crispin, M., "Internet Message Access Protocol
+ - Obsolete Syntax", RFC 2062, December 1996.
+
+ [IMAP2] Crispin, M., "Interactive Mail Access Protocol
+ - Version 2", RFC 1176, August 1990.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA
+ Internet Text Messages", STD 11, RFC 822,
+ August 1982.
+
+ [RFC-821] Postel, J., "Simple Mail Transfer Protocol",
+ STD 10, RFC 821, August 1982.
+
+B. Changes from RFC 2060
+
+ 1) Clarify description of unique identifiers and their semantics.
+
+ 2) Fix the SELECT description to clarify that UIDVALIDITY is required
+ in the SELECT and EXAMINE responses.
+
+ 3) Added an example of a failing search.
+
+ 4) Correct store-att-flags: "#flag" should be "1#flag".
+
+ 5) Made search and section rules clearer.
+
+ 6) Correct the STORE example.
+
+ 7) Correct "BASE645" misspelling.
+
+ 8) Remove extraneous close parenthesis in example of two-part message
+ with text and BASE64 attachment.
+
+
+
+Crispin Standards Track [Page 97]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 9) Remove obsolete "MAILBOX" response from mailbox-data.
+
+ 10) A spurious "<" in the rule for mailbox-data was removed.
+
+ 11) Add CRLF to continue-req.
+
+ 12) Specifically exclude "]" from the atom in resp-text-code.
+
+ 13) Clarify that clients and servers should adhere strictly to the
+ protocol syntax.
+
+ 14) Emphasize in 5.2 that EXISTS can not be used to shrink a mailbox.
+
+ 15) Add NEWNAME to resp-text-code.
+
+ 16) Clarify that the empty string, not NIL, is used as arguments to
+ LIST.
+
+ 17) Clarify that NIL can be returned as a hierarchy delimiter for the
+ empty string mailbox name argument if the mailbox namespace is flat.
+
+ 18) Clarify that addr-mailbox and addr-name have RFC-2822 quoting
+ removed.
+
+ 19) Update UTF-7 reference.
+
+ 20) Fix example in 6.3.11.
+
+ 21) Clarify that non-existent UIDs are ignored.
+
+ 22) Update DISPOSITION reference.
+
+ 23) Expand state diagram.
+
+ 24) Clarify that partial fetch responses are only returned in
+ response to a partial fetch command.
+
+ 25) Add UIDNEXT response code. Correct UIDVALIDITY definition
+ reference.
+
+ 26) Further clarification of "can" vs. "MAY".
+
+ 27) Reference RFC-2119.
+
+ 28) Clarify that superfluous shifts are not permitted in modified
+ UTF-7.
+
+ 29) Clarify that there are no implicit shifts in modified UTF-7.
+
+
+
+Crispin Standards Track [Page 98]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 30) Clarify that "INBOX" in a mailbox name is always INBOX, even if
+ it is given as a string.
+
+ 31) Add missing open parenthesis in media-basic grammar rule.
+
+ 32) Correct attribute syntax in mailbox-data.
+
+ 33) Add UIDNEXT to EXAMINE responses.
+
+ 34) Clarify UNSEEN, PERMANENTFLAGS, UIDVALIDITY, and UIDNEXT
+ responses in SELECT and EXAMINE. They are required now, but weren't
+ in older versions.
+
+ 35) Update references with RFC numbers.
+
+ 36) Flush text-mime2.
+
+ 37) Clarify that modified UTF-7 names must be case-sensitive and that
+ violating the convention should be avoided.
+
+ 38) Correct UID FETCH example.
+
+ 39) Clarify UID FETCH, UID STORE, and UID SEARCH vs. untagged EXPUNGE
+ responses.
+
+ 40) Clarify the use of the word "convention".
+
+ 41) Clarify that a command is not "in progress" until it has been
+ fully received (specifically, that a command is not "in progress"
+ during command continuation negotiation).
+
+ 42) Clarify envelope defaulting.
+
+ 43) Clarify that SP means one and only one space character.
+
+ 44) Forbid silly states in LIST response.
+
+ 45) Clarify that the ENVELOPE, INTERNALDATE, RFC822*, BODY*, and UID
+ for a message is static.
+
+ 46) Add BADCHARSET response code.
+
+ 47) Update formal syntax to [ABNF] conventions.
+
+ 48) Clarify trailing hierarchy delimiter in CREATE semantics.
+
+ 49) Clarify that the "blank line" is the [RFC-2822] delimiting blank
+ line.
+
+
+
+Crispin Standards Track [Page 99]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 50) Clarify that RENAME should also create hierarchy as needed for
+ the command to complete.
+
+ 51) Fix body-ext-mpart to not require language if disposition
+ present.
+
+ 52) Clarify the RFC822.HEADER response.
+
+ 53) Correct missing space after charset astring in search.
+
+ 54) Correct missing quote for BADCHARSET in resp-text-code.
+
+ 55) Clarify that ALL, FAST, and FULL preclude any other data items
+ appearing.
+
+ 56) Clarify semantics of reference argument in LIST.
+
+ 57) Clarify that a null string for SEARCH HEADER X-FOO means any
+ message with a header line with a field-name of X-FOO regardless of
+ the text of the header.
+
+ 58) Specifically reserve 8-bit mailbox names for future use as UTF-8.
+
+ 59) It is not an error for the client to store a flag that is not in
+ the PERMANENTFLAGS list; however, the server will either ignore the
+ change or make the change in the session only.
+
+ 60) Correct/clarify the text regarding superfluous shifts.
+
+ 61) Correct typographic errors in the "Changes" section.
+
+ 62) Clarify that STATUS must not be used to check for new messages in
+ the selected mailbox
+
+ 63) Clarify LSUB behavior with "%" wildcard.
+
+ 64) Change AUTHORIZATION to AUTHENTICATE in section 7.5.
+
+ 65) Clarify description of multipart body type.
+
+ 66) Clarify that STORE FLAGS does not affect \Recent.
+
+ 67) Change "west" to "east" in description of timezone.
+
+ 68) Clarify that commands which break command pipelining must wait
+ for a completion result response.
+
+ 69) Clarify that EXAMINE does not affect \Recent.
+
+
+
+Crispin Standards Track [Page 100]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 70) Make description of MIME structure consistent.
+
+ 71) Clarify that date searches disregard the time and timezone of the
+ INTERNALDATE or Date: header. In other words, "ON 13-APR-2000" means
+ messages with an INTERNALDATE text which starts with "13-APR-2000",
+ even if timezone differential from the local timezone is sufficient
+ to move that INTERNALDATE into the previous or next day.
+
+ 72) Clarify that the header fetches don't add a blank line if one
+ isn't in the [RFC-2822] message.
+
+ 73) Clarify (in discussion of UIDs) that messages are immutable.
+
+ 74) Add an example of CHARSET searching.
+
+ 75) Clarify in SEARCH that keywords are a type of flag.
+
+ 76) Clarify the mandatory nature of the SELECT data responses.
+
+ 77) Add optional CAPABILITY response code in the initial OK or
+ PREAUTH.
+
+ 78) Add note that server can send an untagged CAPABILITY command as
+ part of the responses to AUTHENTICATE and LOGIN.
+
+ 79) Remove statement about it being unnecessary to issue a CAPABILITY
+ command more than once in a connection. That statement is no longer
+ true.
+
+ 80) Clarify that untagged EXPUNGE decrements the number of messages
+ in the mailbox.
+
+ 81) Fix definition of "body" (concatenation has tighter binding than
+ alternation).
+
+ 82) Add a new "Special Notes to Implementors" section with reference
+ to [IMAP-IMPLEMENTATION].
+
+ 83) Clarify that an untagged CAPABILITY response to an AUTHENTICATE
+ command should only be done if a security layer was not negotiated.
+
+ 84) Change the definition of atom to exclude "]". Update astring to
+ include "]" for compatibility with the past. Remove resp-text-atom.
+
+ 85) Remove NEWNAME. It can't work because mailbox names can be
+ literals and can include "]". Functionality can be addressed via
+ referrals.
+
+
+
+
+Crispin Standards Track [Page 101]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 86) Move modified UTF-7 rationale in order to have more logical
+ paragraph flow.
+
+ 87) Clarify UID uniqueness guarantees with the use of MUST.
+
+ 88) Note that clients should read response data until the connection
+ is closed instead of immediately closing on a BYE.
+
+ 89) Change RFC-822 references to RFC-2822.
+
+ 90) Clarify that RFC-2822 should be followed instead of RFC-822.
+
+ 91) Change recommendation of optional automatic capabilities in LOGIN
+ and AUTHENTICATE to use the CAPABILITY response code in the tagged
+ OK. This is more interoperable than an unsolicited untagged
+ CAPABILITY response.
+
+ 92) STARTTLS and AUTH=PLAIN are mandatory to implement; add
+ recommendations for other [SASL] mechanisms.
+
+ 93) Clarify that a "connection" (as opposed to "server" or "command")
+ is in one of the four states.
+
+ 94) Clarify that a failed or rejected command does not change state.
+
+ 95) Split references between normative and informative.
+
+ 96) Discuss authentication failure issues in security section.
+
+ 97) Clarify that a data item is not necessarily of only one data
+ type.
+
+ 98) Clarify that sequence ranges are independent of order.
+
+ 99) Change an example to clarify that superfluous shifts in
+ Modified-UTF7 can not be fixed just by omitting the shift. The
+ entire string must be recalculated.
+
+ 100) Change Envelope Structure definition since [RFC-2822] uses
+ "envelope" to refer to the [SMTP] envelope and not the envelope data
+ that appears in the [RFC-2822] header.
+
+ 101) Expand on RFC822.HEADER response data vs. BODY[HEADER].
+
+ 102) Clarify Logout state semantics, change ASCII art.
+
+ 103) Security changes to comply with IESG requirements.
+
+
+
+
+Crispin Standards Track [Page 102]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 104) Add definition for body URI.
+
+ 105) Break sequence range definition into three rules, with rewritten
+ descriptions for each.
+
+ 106) Move STARTTLS and LOGINDISABLED here from [IMAP-TLS].
+
+ 107) Add IANA Considerations section.
+
+ 108) Clarify valid client assumptions for new message UIDs vs.
+ UIDNEXT.
+
+ 109) Clarify that changes to permanentflags affect concurrent
+ sessions as well as subsequent sessions.
+
+ 110) Clarify that authenticated state can be entered by the CLOSE
+ command.
+
+ 111) Emphasize that SELECT and EXAMINE are the exceptions to the rule
+ that a failing command does not change state.
+
+ 112) Clarify that newly-appended messages have the Recent flag set.
+
+ 113) Clarify that newly-copied messages SHOULD have the Recent flag
+ set.
+
+ 114) Clarify that UID commands always return the UID in FETCH
+ responses.
+
+C. Key Word Index
+
+ +FLAGS <flag list> (store command data item) ............... 59
+ +FLAGS.SILENT <flag list> (store command data item) ........ 59
+ -FLAGS <flag list> (store command data item) ............... 59
+ -FLAGS.SILENT <flag list> (store command data item) ........ 59
+ ALERT (response code) ...................................... 64
+ ALL (fetch item) ........................................... 55
+ ALL (search key) ........................................... 50
+ ANSWERED (search key) ...................................... 50
+ APPEND (command) ........................................... 45
+ AUTHENTICATE (command) ..................................... 27
+ BAD (response) ............................................. 66
+ BADCHARSET (response code) ................................. 64
+ BCC <string> (search key) .................................. 51
+ BEFORE <date> (search key) ................................. 51
+ BODY (fetch item) .......................................... 55
+ BODY (fetch result) ........................................ 73
+ BODY <string> (search key) ................................. 51
+
+
+
+Crispin Standards Track [Page 103]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BODY.PEEK[<section>]<<partial>> (fetch item) ............... 57
+ BODYSTRUCTURE (fetch item) ................................. 57
+ BODYSTRUCTURE (fetch result) ............................... 74
+ BODY[<section>]<<origin octet>> (fetch result) ............. 74
+ BODY[<section>]<<partial>> (fetch item) .................... 55
+ BYE (response) ............................................. 67
+ Body Structure (message attribute) ......................... 12
+ CAPABILITY (command) ....................................... 24
+ CAPABILITY (response code) ................................. 64
+ CAPABILITY (response) ...................................... 68
+ CC <string> (search key) ................................... 51
+ CHECK (command) ............................................ 47
+ CLOSE (command) ............................................ 48
+ COPY (command) ............................................. 59
+ CREATE (command) ........................................... 34
+ DELETE (command) ........................................... 35
+ DELETED (search key) ....................................... 51
+ DRAFT (search key) ......................................... 51
+ ENVELOPE (fetch item) ...................................... 57
+ ENVELOPE (fetch result) .................................... 77
+ EXAMINE (command) .......................................... 33
+ EXISTS (response) .......................................... 71
+ EXPUNGE (command) .......................................... 48
+ EXPUNGE (response) ......................................... 72
+ Envelope Structure (message attribute) ..................... 12
+ FAST (fetch item) .......................................... 55
+ FETCH (command) ............................................ 54
+ FETCH (response) ........................................... 73
+ FLAGGED (search key) ....................................... 51
+ FLAGS (fetch item) ......................................... 57
+ FLAGS (fetch result) ....................................... 78
+ FLAGS (response) ........................................... 71
+ FLAGS <flag list> (store command data item) ................ 59
+ FLAGS.SILENT <flag list> (store command data item) ......... 59
+ FROM <string> (search key) ................................. 51
+ FULL (fetch item) .......................................... 55
+ Flags (message attribute) .................................. 11
+ HEADER (part specifier) .................................... 55
+ HEADER <field-name> <string> (search key) .................. 51
+ HEADER.FIELDS <header-list> (part specifier) ............... 55
+ HEADER.FIELDS.NOT <header-list> (part specifier) ........... 55
+ INTERNALDATE (fetch item) .................................. 57
+ INTERNALDATE (fetch result) ................................ 78
+ Internal Date (message attribute) .......................... 12
+ KEYWORD <flag> (search key) ................................ 51
+ Keyword (type of flag) ..................................... 11
+ LARGER <n> (search key) .................................... 51
+ LIST (command) ............................................. 40
+
+
+
+Crispin Standards Track [Page 104]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ LIST (response) ............................................ 69
+ LOGIN (command) ............................................ 30
+ LOGOUT (command) ........................................... 25
+ LSUB (command) ............................................. 43
+ LSUB (response) ............................................ 70
+ MAY (specification requirement term) ....................... 4
+ MESSAGES (status item) ..................................... 45
+ MIME (part specifier) ...................................... 56
+ MUST (specification requirement term) ...................... 4
+ MUST NOT (specification requirement term) .................. 4
+ Message Sequence Number (message attribute) ................ 10
+ NEW (search key) ........................................... 51
+ NO (response) .............................................. 66
+ NOOP (command) ............................................. 25
+ NOT <search-key> (search key) .............................. 52
+ OK (response) .............................................. 65
+ OLD (search key) ........................................... 52
+ ON <date> (search key) ..................................... 52
+ OPTIONAL (specification requirement term) .................. 4
+ OR <search-key1> <search-key2> (search key) ................ 52
+ PARSE (response code) ...................................... 64
+ PERMANENTFLAGS (response code) ............................. 64
+ PREAUTH (response) ......................................... 67
+ Permanent Flag (class of flag) ............................. 12
+ READ-ONLY (response code) .................................. 65
+ READ-WRITE (response code) ................................. 65
+ RECENT (response) .......................................... 72
+ RECENT (search key) ........................................ 52
+ RECENT (status item) ....................................... 45
+ RENAME (command) ........................................... 37
+ REQUIRED (specification requirement term) .................. 4
+ RFC822 (fetch item) ........................................ 57
+ RFC822 (fetch result) ...................................... 78
+ RFC822.HEADER (fetch item) ................................. 57
+ RFC822.HEADER (fetch result) ............................... 78
+ RFC822.SIZE (fetch item) ................................... 57
+ RFC822.SIZE (fetch result) ................................. 78
+ RFC822.TEXT (fetch item) ................................... 58
+ RFC822.TEXT (fetch result) ................................. 79
+ SEARCH (command) ........................................... 49
+ SEARCH (response) .......................................... 71
+ SEEN (search key) .......................................... 52
+ SELECT (command) ........................................... 31
+ SENTBEFORE <date> (search key) ............................. 52
+ SENTON <date> (search key) ................................. 52
+ SENTSINCE <date> (search key) .............................. 52
+ SHOULD (specification requirement term) .................... 4
+ SHOULD NOT (specification requirement term) ................ 4
+
+
+
+Crispin Standards Track [Page 105]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SINCE <date> (search key) .................................. 52
+ SMALLER <n> (search key) ................................... 52
+ STARTTLS (command) ......................................... 27
+ STATUS (command) ........................................... 44
+ STATUS (response) .......................................... 70
+ STORE (command) ............................................ 58
+ SUBJECT <string> (search key) .............................. 53
+ SUBSCRIBE (command) ........................................ 38
+ Session Flag (class of flag) ............................... 12
+ System Flag (type of flag) ................................. 11
+ TEXT (part specifier) ...................................... 56
+ TEXT <string> (search key) ................................. 53
+ TO <string> (search key) ................................... 53
+ TRYCREATE (response code) .................................. 65
+ UID (command) .............................................. 60
+ UID (fetch item) ........................................... 58
+ UID (fetch result) ......................................... 79
+ UID <sequence set> (search key) ............................ 53
+ UIDNEXT (response code) .................................... 65
+ UIDNEXT (status item) ...................................... 45
+ UIDVALIDITY (response code) ................................ 65
+ UIDVALIDITY (status item) .................................. 45
+ UNANSWERED (search key) .................................... 53
+ UNDELETED (search key) ..................................... 53
+ UNDRAFT (search key) ....................................... 53
+ UNFLAGGED (search key) ..................................... 53
+ UNKEYWORD <flag> (search key) .............................. 53
+ UNSEEN (response code) ..................................... 65
+ UNSEEN (search key) ........................................ 53
+ UNSEEN (status item) ....................................... 45
+ UNSUBSCRIBE (command) ...................................... 39
+ Unique Identifier (UID) (message attribute) ................ 8
+ X<atom> (command) .......................................... 62
+ [RFC-2822] Size (message attribute) ........................ 12
+ \Answered (system flag) .................................... 11
+ \Deleted (system flag) ..................................... 11
+ \Draft (system flag) ....................................... 11
+ \Flagged (system flag) ..................................... 11
+ \Marked (mailbox name attribute) ........................... 69
+ \Noinferiors (mailbox name attribute) ...................... 69
+ \Noselect (mailbox name attribute) ......................... 69
+ \Recent (system flag) ...................................... 11
+ \Seen (system flag) ........................................ 11
+ \Unmarked (mailbox name attribute) ......................... 69
+
+
+
+
+
+
+
+Crispin Standards Track [Page 106]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
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+
+
+
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+
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+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 107]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns. v This
+ document and the information contained herein is provided on an "AS
+ IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
+ FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+ LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
+ NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
+ OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 108]
+
diff --git a/rfc/rfc4616.txt b/rfc/rfc4616.txt
@@ -0,0 +1,619 @@
+
+
+
+
+
+
+Network Working Group K. Zeilenga, Ed.
+Request for Comments: 4616 OpenLDAP Foundation
+Updates: 2595 August 2006
+Category: Standards Track
+
+
+ The PLAIN Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ This document defines a simple clear-text user/password Simple
+ Authentication and Security Layer (SASL) mechanism called the PLAIN
+ mechanism. The PLAIN mechanism is intended to be used, in
+ combination with data confidentiality services provided by a lower
+ layer, in protocols that lack a simple password authentication
+ command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 1]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+1. Introduction
+
+ Clear-text, multiple-use passwords are simple, interoperate with
+ almost all existing operating system authentication databases, and
+ are useful for a smooth transition to a more secure password-based
+ authentication mechanism. The drawback is that they are unacceptable
+ for use over network connections where data confidentiality is not
+ ensured.
+
+ This document defines the PLAIN Simple Authentication and Security
+ Layer ([SASL]) mechanism for use in protocols with no clear-text
+ login command (e.g., [ACAP] or [SMTP-AUTH]). This document updates
+ RFC 2595, replacing Section 6. Changes since RFC 2595 are detailed
+ in Appendix A.
+
+ The name associated with this mechanism is "PLAIN".
+
+ The PLAIN SASL mechanism does not provide a security layer.
+
+ The PLAIN mechanism should not be used without adequate data security
+ protection as this mechanism affords no integrity or confidentiality
+ protections itself. The mechanism is intended to be used with data
+ security protections provided by application-layer protocol,
+ generally through its use of Transport Layer Security ([TLS])
+ services.
+
+ By default, implementations SHOULD advertise and make use of the
+ PLAIN mechanism only when adequate data security services are in
+ place. Specifications for IETF protocols that indicate that this
+ mechanism is an applicable authentication mechanism MUST mandate that
+ implementations support an strong data security service, such as TLS.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [Keywords].
+
+2. PLAIN SASL Mechanism
+
+ The mechanism consists of a single message, a string of [UTF-8]
+ encoded [Unicode] characters, from the client to the server. The
+ client presents the authorization identity (identity to act as),
+ followed by a NUL (U+0000) character, followed by the authentication
+ identity (identity whose password will be used), followed by a NUL
+ (U+0000) character, followed by the clear-text password. As with
+ other SASL mechanisms, the client does not provide an authorization
+ identity when it wishes the server to derive an identity from the
+ credentials and use that as the authorization identity.
+
+
+
+
+Zeilenga Standards Track [Page 2]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ The formal grammar for the client message using Augmented BNF [ABNF]
+ follows.
+
+ message = [authzid] UTF8NUL authcid UTF8NUL passwd
+ authcid = 1*SAFE ; MUST accept up to 255 octets
+ authzid = 1*SAFE ; MUST accept up to 255 octets
+ passwd = 1*SAFE ; MUST accept up to 255 octets
+ UTF8NUL = %x00 ; UTF-8 encoded NUL character
+
+ SAFE = UTF1 / UTF2 / UTF3 / UTF4
+ ;; any UTF-8 encoded Unicode character except NUL
+
+ UTF1 = %x01-7F ;; except NUL
+ UTF2 = %xC2-DF UTF0
+ UTF3 = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
+ %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
+ UTF4 = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
+ %xF4 %x80-8F 2(UTF0)
+ UTF0 = %x80-BF
+
+ The authorization identity (authzid), authentication identity
+ (authcid), password (passwd), and NUL character deliminators SHALL be
+ transferred as [UTF-8] encoded strings of [Unicode] characters. As
+ the NUL (U+0000) character is used as a deliminator, the NUL (U+0000)
+ character MUST NOT appear in authzid, authcid, or passwd productions.
+
+ The form of the authzid production is specific to the application-
+ level protocol's SASL profile [SASL]. The authcid and passwd
+ productions are form-free. Use of non-visible characters or
+ characters that a user may be unable to enter on some keyboards is
+ discouraged.
+
+ Servers MUST be capable of accepting authzid, authcid, and passwd
+ productions up to and including 255 octets. It is noted that the
+ UTF-8 encoding of a Unicode character may be as long as 4 octets.
+
+ Upon receipt of the message, the server will verify the presented (in
+ the message) authentication identity (authcid) and password (passwd)
+ with the system authentication database, and it will verify that the
+ authentication credentials permit the client to act as the (presented
+ or derived) authorization identity (authzid). If both steps succeed,
+ the user is authenticated.
+
+ The presented authentication identity and password strings, as well
+ as the database authentication identity and password strings, are to
+ be prepared before being used in the verification process. The
+ [SASLPrep] profile of the [StringPrep] algorithm is the RECOMMENDED
+ preparation algorithm. The SASLprep preparation algorithm is
+
+
+
+Zeilenga Standards Track [Page 3]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ recommended to improve the likelihood that comparisons behave in an
+ expected manner. The SASLprep preparation algorithm is not mandatory
+ so as to allow the server to employ other preparation algorithms
+ (including none) when appropriate. For instance, use of a different
+ preparation algorithm may be necessary for the server to interoperate
+ with an external system.
+
+ When preparing the presented strings using [SASLPrep], the presented
+ strings are to be treated as "query" strings (Section 7 of
+ [StringPrep]) and hence unassigned code points are allowed to appear
+ in their prepared output. When preparing the database strings using
+ [SASLPrep], the database strings are to be treated as "stored"
+ strings (Section 7 of [StringPrep]) and hence unassigned code points
+ are prohibited from appearing in their prepared output.
+
+ Regardless of the preparation algorithm used, if the output of a
+ non-invertible function (e.g., hash) of the expected string is
+ stored, the string MUST be prepared before input to that function.
+
+ Regardless of the preparation algorithm used, if preparation fails or
+ results in an empty string, verification SHALL fail.
+
+ When no authorization identity is provided, the server derives an
+ authorization identity from the prepared representation of the
+ provided authentication identity string. This ensures that the
+ derivation of different representations of the authentication
+ identity produces the same authorization identity.
+
+ The server MAY use the credentials to initialize any new
+ authentication database, such as one suitable for [CRAM-MD5] or
+ [DIGEST-MD5].
+
+3. Pseudo-Code
+
+ This section provides pseudo-code illustrating the verification
+ process (using hashed passwords and the SASLprep preparation
+ function) discussed above. This section is not definitive.
+
+ boolean Verify(string authzid, string authcid, string passwd) {
+ string pAuthcid = SASLprep(authcid, true); # prepare authcid
+ string pPasswd = SASLprep(passwd, true); # prepare passwd
+ if (pAuthcid == NULL || pPasswd == NULL) {
+ return false; # preparation failed
+ }
+ if (pAuthcid == "" || pPasswd == "") {
+ return false; # empty prepared string
+ }
+
+
+
+
+Zeilenga Standards Track [Page 4]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ storedHash = FetchPasswordHash(pAuthcid);
+ if (storedHash == NULL || storedHash == "") {
+ return false; # error or unknown authcid
+ }
+
+ if (!Compare(storedHash, Hash(pPasswd))) {
+ return false; # incorrect password
+ }
+
+ if (authzid == NULL ) {
+ authzid = DeriveAuthzid(pAuthcid);
+ if (authzid == NULL || authzid == "") {
+ return false; # could not derive authzid
+ }
+ }
+
+ if (!Authorize(pAuthcid, authzid)) {
+ return false; # not authorized
+ }
+
+ return true;
+ }
+
+ The second parameter of the SASLprep function, when true, indicates
+ that unassigned code points are allowed in the input. When the
+ SASLprep function is called to prepare the password prior to
+ computing the stored hash, the second parameter would be false.
+
+ The second parameter provided to the Authorize function is not
+ prepared by this code. The application-level SASL profile should be
+ consulted to determine what, if any, preparation is necessary.
+
+ Note that the DeriveAuthzid and Authorize functions (whether
+ implemented as one function or two, whether designed in a manner in
+ which these functions or whether the mechanism implementation can be
+ reused elsewhere) require knowledge and understanding of mechanism
+ and the application-level protocol specification and/or
+ implementation details to implement.
+
+ Note that the Authorize function outcome is clearly dependent on
+ details of the local authorization model and policy. Both functions
+ may be dependent on other factors as well.
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 5]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+4. Examples
+
+ This section provides examples of PLAIN authentication exchanges.
+ The examples are intended to help the readers understand the above
+ text. The examples are not definitive.
+
+ "C:" and "S:" indicate lines sent by the client and server,
+ respectively. "<NUL>" represents a single NUL (U+0000) character.
+ The Application Configuration Access Protocol ([ACAP]) is used in the
+ examples.
+
+ The first example shows how the PLAIN mechanism might be used for
+ user authentication.
+
+ S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+ C: a002 AUTHENTICATE "PLAIN"
+ S: + ""
+ C: {21}
+ C: <NUL>tim<NUL>tanstaaftanstaaf
+ S: a002 OK "Authenticated"
+
+ The second example shows how the PLAIN mechanism might be used to
+ attempt to assume the identity of another user. In this example, the
+ server rejects the request. Also, this example makes use of the
+ protocol optional initial response capability to eliminate a round-
+ trip.
+
+ S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+ C: a002 AUTHENTICATE "PLAIN" {20+}
+ C: Ursel<NUL>Kurt<NUL>xipj3plmq
+ S: a002 NO "Not authorized to requested authorization identity"
+
+5. Security Considerations
+
+ As the PLAIN mechanism itself provided no integrity or
+ confidentiality protections, it should not be used without adequate
+ external data security protection, such as TLS services provided by
+ many application-layer protocols. By default, implementations SHOULD
+ NOT advertise and SHOULD NOT make use of the PLAIN mechanism unless
+ adequate data security services are in place.
+
+
+
+Zeilenga Standards Track [Page 6]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ When the PLAIN mechanism is used, the server gains the ability to
+ impersonate the user to all services with the same password
+ regardless of any encryption provided by TLS or other confidentiality
+ protection mechanisms. Whereas many other authentication mechanisms
+ have similar weaknesses, stronger SASL mechanisms address this issue.
+ Clients are encouraged to have an operational mode where all
+ mechanisms that are likely to reveal the user's password to the
+ server are disabled.
+
+ General [SASL] security considerations apply to this mechanism.
+
+ Unicode, [UTF-8], and [StringPrep] security considerations also
+ apply.
+
+6. IANA Considerations
+
+ The SASL Mechanism registry [IANA-SASL] entry for the PLAIN mechanism
+ has been updated by the IANA to reflect that this document now
+ provides its technical specification.
+
+ To: iana@iana.org
+ Subject: Updated Registration of SASL mechanism PLAIN
+
+ SASL mechanism name: PLAIN
+ Security considerations: See RFC 4616.
+ Published specification (optional, recommended): RFC 4616
+ Person & email address to contact for further information:
+ Kurt Zeilenga <kurt@openldap.org>
+ IETF SASL WG <ietf-sasl@imc.org>
+ Intended usage: COMMON
+ Author/Change controller: IESG <iesg@ietf.org>
+ Note: Updates existing entry for PLAIN
+
+7. Acknowledgements
+
+ This document is a revision of RFC 2595 by Chris Newman. Portions of
+ the grammar defined in Section 2 were borrowed from [UTF-8] by
+ Francois Yergeau.
+
+ This document is a product of the IETF Simple Authentication and
+ Security Layer (SASL) Working Group.
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 7]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+8. Normative References
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+ [Keywords] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [SASL] Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
+ Authentication and Security Layer (SASL)", RFC 4422,
+ June 2006.
+
+ [SASLPrep] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+ [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [Unicode] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0" is defined by "The Unicode Standard, Version
+ 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+ 61633-5), as amended by the "Unicode Standard Annex
+ #27: Unicode 3.1"
+ (http://www.unicode.org/reports/tr27/) and by the
+ "Unicode Standard Annex #28: Unicode 3.2"
+ (http://www.unicode.org/reports/tr28/).
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
+ Security (TLS) Protocol Version 1.1", RFC 4346, April
+ 2006.
+
+9. Informative References
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November
+ 1997.
+
+ [CRAM-MD5] Nerenberg, L., Ed., "The CRAM-MD5 SASL Mechanism", Work
+ in Progress, June 2006.
+
+ [DIGEST-MD5] Melnikov, A., Ed., "Using Digest Authentication as a
+ SASL Mechanism", Work in Progress, June 2006.
+
+
+
+
+
+Zeilenga Standards Track [Page 8]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ [IANA-SASL] IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
+ MECHANISMS",
+ <http://www.iana.org/assignments/sasl-mechanisms>.
+
+ [SMTP-AUTH] Myers, J., "SMTP Service Extension for Authentication",
+ RFC 2554, March 1999.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 9]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+Appendix A. Changes since RFC 2595
+
+ This appendix is non-normative.
+
+ This document replaces Section 6 of RFC 2595.
+
+ The specification details how the server is to compare client-
+ provided character strings with stored character strings.
+
+ The ABNF grammar was updated. In particular, the grammar now allows
+ LINE FEED (U+000A) and CARRIAGE RETURN (U+000D) characters in the
+ authzid, authcid, passwd productions. However, whether these control
+ characters may be used depends on the string preparation rules
+ applicable to the production. For passwd and authcid productions,
+ control characters are prohibited. For authzid, one must consult the
+ application-level SASL profile. This change allows PLAIN to carry
+ all possible authorization identity strings allowed in SASL.
+
+ Pseudo-code was added.
+
+ The example section was expanded to illustrate more features of the
+ PLAIN mechanism.
+
+Editor's Address
+
+ Kurt D. Zeilenga
+ OpenLDAP Foundation
+
+ EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 10]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 11]
+
diff --git a/rfc/rfc5256.txt b/rfc/rfc5256.txt
@@ -0,0 +1,1067 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 5256 Panda Programming
+Category: Standards Track K. Murchison
+ Carnegie Mellon University
+ June 2008
+
+
+ Internet Message Access Protocol - SORT and THREAD Extensions
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document describes the base-level server-based sorting and
+ threading extensions to the IMAP protocol. These extensions provide
+ substantial performance improvements for IMAP clients that offer
+ sorted and threaded views.
+
+1. Introduction
+
+ The SORT and THREAD extensions to the [IMAP] protocol provide a means
+ of server-based sorting and threading of messages, without requiring
+ that the client download the necessary data to do so itself. This is
+ particularly useful for online clients as described in [IMAP-MODELS].
+
+ A server that supports the base-level SORT extension indicates this
+ with a capability name which starts with "SORT". Future, upwards-
+ compatible extensions to the SORT extension will all start with
+ "SORT", indicating support for this base level.
+
+ A server that supports the THREAD extension indicates this with one
+ or more capability names consisting of "THREAD=" followed by a
+ supported threading algorithm name as described in this document.
+ This provides for future upwards-compatible extensions.
+
+ A server that implements the SORT and/or THREAD extensions MUST
+ collate strings in accordance with the requirements of I18NLEVEL=1,
+ as described in [IMAP-I18N], and SHOULD implement and advertise the
+ I18NLEVEL=1 extension. Alternatively, a server MAY implement
+ I18NLEVEL=2 (or higher) and comply with the rules of that level.
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 1]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ Discussion: The SORT and THREAD extensions predate [IMAP-I18N] by
+ several years. At the time of this writing, all known server
+ implementations of SORT and THREAD comply with the rules of
+ I18NLEVEL=1, but do not necessarily advertise it. As discussed in
+ [IMAP-I18N] section 4.5, all server implementations should
+ eventually be updated to comply with the I18NLEVEL=2 extension.
+
+ Historical note: The REFERENCES threading algorithm is based on the
+ [THREADING] algorithm written and used in "Netscape Mail and News"
+ versions 2.0 through 3.0.
+
+2. Terminology
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [KEYWORDS].
+
+ The word "can" (not "may") is used to refer to a possible
+ circumstance or situation, as opposed to an optional facility of the
+ protocol.
+
+ "User" is used to refer to a human user, whereas "client" refers to
+ the software being run by the user.
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+2.1. Base Subject
+
+ Subject sorting and threading use the "base subject", which has
+ specific subject artifacts removed. Due to the complexity of these
+ artifacts, the formal syntax for the subject extraction rules is
+ ambiguous. The following procedure is followed to determine the
+ "base subject", using the [ABNF] formal syntax rules described in
+ section 5:
+
+ (1) Convert any RFC 2047 encoded-words in the subject to [UTF-8]
+ as described in "Internationalization Considerations".
+ Convert all tabs and continuations to space. Convert all
+ multiple spaces to a single space.
+
+ (2) Remove all trailing text of the subject that matches the
+ subj-trailer ABNF; repeat until no more matches are possible.
+
+ (3) Remove all prefix text of the subject that matches the subj-
+ leader ABNF.
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 2]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ (4) If there is prefix text of the subject that matches the subj-
+ blob ABNF, and removing that prefix leaves a non-empty subj-
+ base, then remove the prefix text.
+
+ (5) Repeat (3) and (4) until no matches remain.
+
+ Note: It is possible to defer step (2) until step (6), but this
+ requires checking for subj-trailer in step (4).
+
+ (6) If the resulting text begins with the subj-fwd-hdr ABNF and
+ ends with the subj-fwd-trl ABNF, remove the subj-fwd-hdr and
+ subj-fwd-trl and repeat from step (2).
+
+ (7) The resulting text is the "base subject" used in the SORT.
+
+ All servers and disconnected (as described in [IMAP-MODELS]) clients
+ MUST use exactly this algorithm to determine the "base subject".
+ Otherwise, there is potential for a user to get inconsistent results
+ based on whether they are running in connected or disconnected mode.
+
+2.2. Sent Date
+
+ As used in this document, the term "sent date" refers to the date and
+ time from the Date: header, adjusted by time zone to normalize to
+ UTC. For example, "31 Dec 2000 16:01:33 -0800" is equivalent to the
+ UTC date and time of "1 Jan 2001 00:01:33 +0000".
+
+ If the time zone is invalid, the date and time SHOULD be treated as
+ UTC. If the time is also invalid, the time SHOULD be treated as
+ 00:00:00. If there is no valid date or time, the date and time
+ SHOULD be treated as 00:00:00 on the earliest possible date.
+
+ This differs from the date-related criteria in the SEARCH command
+ (described in [IMAP] section 6.4.4), which use just the date and not
+ the time, and are not adjusted by time zone.
+
+ If the sent date cannot be determined (a Date: header is missing or
+ cannot be parsed), the INTERNALDATE for that message is used as the
+ sent date.
+
+ When comparing two sent dates that match exactly, the order in which
+ the two messages appear in the mailbox (that is, by sequence number)
+ is used as a tie-breaker to determine the order.
+
+
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 3]
+
+RFC 5256 IMAP Sort June 2008
+
+
+3. Additional Commands
+
+ These commands are extensions to the [IMAP] base protocol.
+
+ The section headings are intended to correspond with where they would
+ be located in the main document if they were part of the base
+ specification.
+
+BASE.6.4.SORT. SORT Command
+
+ Arguments: sort program
+ charset specification
+ searching criteria (one or more)
+
+ Data: untagged responses: SORT
+
+ Result: OK - sort completed
+ NO - sort error: can't sort that charset or
+ criteria
+ BAD - command unknown or arguments invalid
+
+ The SORT command is a variant of SEARCH with sorting semantics for
+ the results. There are two arguments before the searching
+ criteria argument: a parenthesized list of sort criteria, and the
+ searching charset.
+
+ The charset argument is mandatory (unlike SEARCH) and indicates
+ the [CHARSET] of the strings that appear in the searching
+ criteria. The US-ASCII and [UTF-8] charsets MUST be implemented.
+ All other charsets are optional.
+
+ There is also a UID SORT command that returns unique identifiers
+ instead of message sequence numbers. Note that there are separate
+ searching criteria for message sequence numbers and UIDs; thus,
+ the arguments to UID SORT are interpreted the same as in SORT.
+ This is analogous to the behavior of UID SEARCH, as opposed to UID
+ COPY, UID FETCH, or UID STORE.
+
+ The SORT command first searches the mailbox for messages that
+ match the given searching criteria using the charset argument for
+ the interpretation of strings in the searching criteria. It then
+ returns the matching messages in an untagged SORT response, sorted
+ according to one or more sort criteria.
+
+ Sorting is in ascending order. Earlier dates sort before later
+ dates; smaller sizes sort before larger sizes; and strings are
+ sorted according to ascending values established by their
+ collation algorithm (see "Internationalization Considerations").
+
+
+
+Crispin & Murchison Standards Track [Page 4]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ If two or more messages exactly match according to the sorting
+ criteria, these messages are sorted according to the order in
+ which they appear in the mailbox. In other words, there is an
+ implicit sort criterion of "sequence number".
+
+ When multiple sort criteria are specified, the result is sorted in
+ the priority order that the criteria appear. For example,
+ (SUBJECT DATE) will sort messages in order by their base subject
+ text; and for messages with the same base subject text, it will
+ sort by their sent date.
+
+ Untagged EXPUNGE responses are not permitted while the server is
+ responding to a SORT command, but are permitted during a UID SORT
+ command.
+
+ The defined sort criteria are as follows. Refer to the Formal
+ Syntax section for the precise syntactic definitions of the
+ arguments. If the associated RFC-822 header for a particular
+ criterion is absent, it is treated as the empty string. The empty
+ string always collates before non-empty strings.
+
+ ARRIVAL
+ Internal date and time of the message. This differs from the
+ ON criteria in SEARCH, which uses just the internal date.
+
+ CC
+ [IMAP] addr-mailbox of the first "cc" address.
+
+ DATE
+ Sent date and time, as described in section 2.2.
+
+ FROM
+ [IMAP] addr-mailbox of the first "From" address.
+
+ REVERSE
+ Followed by another sort criterion, has the effect of that
+ criterion but in reverse (descending) order.
+ Note: REVERSE only reverses a single criterion, and does not
+ affect the implicit "sequence number" sort criterion if all
+ other criteria are identical. Consequently, a sort of
+ REVERSE SUBJECT is not the same as a reverse ordering of a
+ SUBJECT sort. This can be avoided by use of additional
+ criteria, e.g., SUBJECT DATE vs. REVERSE SUBJECT REVERSE
+ DATE. In general, however, it's better (and faster, if the
+ client has a "reverse current ordering" command) to reverse
+ the results in the client instead of issuing a new SORT.
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 5]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ SIZE
+ Size of the message in octets.
+
+ SUBJECT
+ Base subject text.
+
+ TO
+ [IMAP] addr-mailbox of the first "To" address.
+
+ Example: C: A282 SORT (SUBJECT) UTF-8 SINCE 1-Feb-1994
+ S: * SORT 2 84 882
+ S: A282 OK SORT completed
+ C: A283 SORT (SUBJECT REVERSE DATE) UTF-8 ALL
+ S: * SORT 5 3 4 1 2
+ S: A283 OK SORT completed
+ C: A284 SORT (SUBJECT) US-ASCII TEXT "not in mailbox"
+ S: * SORT
+ S: A284 OK SORT completed
+
+BASE.6.4.THREAD. THREAD Command
+
+Arguments: threading algorithm
+ charset specification
+ searching criteria (one or more)
+
+Data: untagged responses: THREAD
+
+Result: OK - thread completed
+ NO - thread error: can't thread that charset or
+ criteria
+ BAD - command unknown or arguments invalid
+
+ The THREAD command is a variant of SEARCH with threading semantics
+ for the results. Thread has two arguments before the searching
+ criteria argument: a threading algorithm and the searching
+ charset.
+
+ The charset argument is mandatory (unlike SEARCH) and indicates
+ the [CHARSET] of the strings that appear in the searching
+ criteria. The US-ASCII and [UTF-8] charsets MUST be implemented.
+ All other charsets are optional.
+
+ There is also a UID THREAD command that returns unique identifiers
+ instead of message sequence numbers. Note that there are separate
+ searching criteria for message sequence numbers and UIDs; thus the
+ arguments to UID THREAD are interpreted the same as in THREAD.
+ This is analogous to the behavior of UID SEARCH, as opposed to UID
+ COPY, UID FETCH, or UID STORE.
+
+
+
+Crispin & Murchison Standards Track [Page 6]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ The THREAD command first searches the mailbox for messages that
+ match the given searching criteria using the charset argument for
+ the interpretation of strings in the searching criteria. It then
+ returns the matching messages in an untagged THREAD response,
+ threaded according to the specified threading algorithm.
+
+ All collation is in ascending order. Earlier dates collate before
+ later dates and strings are collated according to ascending values
+ established by their collation algorithm (see
+ "Internationalization Considerations").
+
+ Untagged EXPUNGE responses are not permitted while the server is
+ responding to a THREAD command, but are permitted during a UID
+ THREAD command.
+
+ The defined threading algorithms are as follows:
+
+ ORDEREDSUBJECT
+
+ The ORDEREDSUBJECT threading algorithm is also referred to as
+ "poor man's threading". The searched messages are sorted by
+ base subject and then by the sent date. The messages are then
+ split into separate threads, with each thread containing
+ messages with the same base subject text. Finally, the threads
+ are sorted by the sent date of the first message in the thread.
+
+ The top level or "root" in ORDEREDSUBJECT threading contains
+ the first message of every thread. All messages in the root
+ are siblings of each other. The second message of a thread is
+ the child of the first message, and subsequent messages of the
+ thread are siblings of the second message and hence children of
+ the message at the root. Hence, there are no grandchildren in
+ ORDEREDSUBJECT threading.
+
+ Children in ORDEREDSUBJECT threading do not have descendents.
+ Client implementations SHOULD treat descendents of a child in a
+ server response as being siblings of that child.
+
+ REFERENCES
+
+ The REFERENCES threading algorithm threads the searched
+ messages by grouping them together in parent/child
+ relationships based on which messages are replies to others.
+ The parent/child relationships are built using two methods:
+ reconstructing a message's ancestry using the references
+ contained within it; and checking the original (not base)
+ subject of a message to see if it is a reply to (or forward of)
+ another message.
+
+
+
+Crispin & Murchison Standards Track [Page 7]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ Note: "Message ID" in the following description refers to a
+ normalized form of the msg-id in [RFC2822]. The actual text
+ in RFC 2822 may use quoting, resulting in multiple ways of
+ expressing the same Message ID. Implementations of the
+ REFERENCES threading algorithm MUST normalize any msg-id in
+ order to avoid false non-matches due to differences in
+ quoting.
+
+ For example, the msg-id
+ <"01KF8JCEOCBS0045PS"@xxx.yyy.com>
+ and the msg-id
+ <01KF8JCEOCBS0045PS@xxx.yyy.com>
+ MUST be interpreted as being the same Message ID.
+
+ The references used for reconstructing a message's ancestry are
+ found using the following rules:
+
+ If a message contains a References header line, then use the
+ Message IDs in the References header line as the references.
+
+ If a message does not contain a References header line, or
+ the References header line does not contain any valid
+ Message IDs, then use the first (if any) valid Message ID
+ found in the In-Reply-To header line as the only reference
+ (parent) for this message.
+
+ Note: Although [RFC2822] permits multiple Message IDs in
+ the In-Reply-To header, in actual practice this
+ discipline has not been followed. For example,
+ In-Reply-To headers have been observed with message
+ addresses after the Message ID, and there are no good
+ heuristics for software to determine the difference.
+ This is not a problem with the References header,
+ however.
+
+ If a message does not contain an In-Reply-To header line, or
+ the In-Reply-To header line does not contain a valid Message
+ ID, then the message does not have any references (NIL).
+
+ A message is considered to be a reply or forward if the base
+ subject extraction rules, applied to the original subject,
+ remove any of the following: a subj-refwd, a "(fwd)" subj-
+ trailer, or a subj-fwd-hdr and subj-fwd-trl.
+
+ The REFERENCES algorithm is significantly more complex than
+ ORDEREDSUBJECT and consists of six main steps. These steps are
+ outlined in detail below.
+
+
+
+
+Crispin & Murchison Standards Track [Page 8]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ (1) For each searched message:
+
+ (A) Using the Message IDs in the message's references, link
+ the corresponding messages (those whose Message-ID
+ header line contains the given reference Message ID)
+ together as parent/child. Make the first reference the
+ parent of the second (and the second a child of the
+ first), the second the parent of the third (and the
+ third a child of the second), etc. The following rules
+ govern the creation of these links:
+
+ If a message does not contain a Message-ID header
+ line, or the Message-ID header line does not
+ contain a valid Message ID, then assign a unique
+ Message ID to this message.
+
+ If two or more messages have the same Message ID,
+ then only use that Message ID in the first (lowest
+ sequence number) message, and assign a unique
+ Message ID to each of the subsequent messages with
+ a duplicate of that Message ID.
+
+ If no message can be found with a given Message ID,
+ create a dummy message with this ID. Use this
+ dummy message for all subsequent references to this
+ ID.
+
+ If a message already has a parent, don't change the
+ existing link. This is done because the References
+ header line may have been truncated by a Mail User
+ Agent (MUA). As a result, there is no guarantee
+ that the messages corresponding to adjacent Message
+ IDs in the References header line are parent and
+ child.
+
+ Do not create a parent/child link if creating that
+ link would introduce a loop. For example, before
+ making message A the parent of B, make sure that A
+ is not a descendent of B.
+
+ Note: Message ID comparisons are case-sensitive.
+
+ (B) Create a parent/child link between the last reference
+ (or NIL if there are no references) and the current
+ message. If the current message already has a parent,
+ it is probably the result of a truncated References
+ header line, so break the current parent/child link
+ before creating the new correct one. As in step 1.A,
+
+
+
+Crispin & Murchison Standards Track [Page 9]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ do not create the parent/child link if creating that
+ link would introduce a loop. Note that if this message
+ has no references, it will now have no parent.
+
+ Note: The parent/child links created in steps 1.A
+ and 1.B MUST be kept consistent with one another at
+ ALL times.
+
+ (2) Gather together all of the messages that have no parents
+ and make them all children (siblings of one another) of a
+ dummy parent (the "root"). These messages constitute the
+ first (head) message of the threads created thus far.
+
+ (3) Prune dummy messages from the thread tree. Traverse each
+ thread under the root, and for each message:
+
+ If it is a dummy message with NO children, delete it.
+
+ If it is a dummy message with children, delete it, but
+ promote its children to the current level. In other
+ words, splice them in with the dummy's siblings.
+
+ Do not promote the children if doing so would make them
+ children of the root, unless there is only one child.
+
+ (4) Sort the messages under the root (top-level siblings only)
+ by sent date as described in section 2.2. In the case of a
+ dummy message, sort its children by sent date and then use
+ the first child for the top-level sort.
+
+ (5) Gather together messages under the root that have the same
+ base subject text.
+
+ (A) Create a table for associating base subjects with
+ messages, called the subject table.
+
+ (B) Populate the subject table with one message per each
+ base subject. For each child of the root:
+
+ (i) Find the subject of this thread, by using the
+ base subject from either the current message or
+ its first child if the current message is a
+ dummy. This is the thread subject.
+
+ (ii) If the thread subject is empty, skip this
+ message.
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 10]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ (iii) Look up the message associated with the thread
+ subject in the subject table.
+
+ (iv) If there is no message in the subject table with
+ the thread subject, add the current message and
+ the thread subject to the subject table.
+
+ Otherwise, if the message in the subject table is
+ not a dummy, AND either of the following criteria
+ are true:
+
+ The current message is a dummy, OR
+
+ The message in the subject table is a reply
+ or forward and the current message is not.
+
+ then replace the message in the subject table
+ with the current message.
+
+ (C) Merge threads with the same thread subject. For each
+ child of the root:
+
+ (i) Find the message's thread subject as in step
+ 5.B.i above.
+
+ (ii) If the thread subject is empty, skip this
+ message.
+
+ (iii) Lookup the message associated with this thread
+ subject in the subject table.
+
+ (iv) If the message in the subject table is the
+ current message, skip this message.
+
+ Otherwise, merge the current message with the one in
+ the subject table using the following rules:
+
+ If both messages are dummies, append the current
+ message's children to the children of the message
+ in the subject table (the children of both messages
+ become siblings), and then delete the current
+ message.
+
+ If the message in the subject table is a dummy and
+ the current message is not, make the current
+ message a child of the message in the subject table
+ (a sibling of its children).
+
+
+
+
+Crispin & Murchison Standards Track [Page 11]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ If the current message is a reply or forward and
+ the message in the subject table is not, make the
+ current message a child of the message in the
+ subject table (a sibling of its children).
+
+ Otherwise, create a new dummy message and make both
+ the current message and the message in the subject
+ table children of the dummy. Then replace the
+ message in the subject table with the dummy
+ message.
+
+ Note: Subject comparisons are case-insensitive,
+ as described under "Internationalization
+ Considerations".
+
+ (6) Traverse the messages under the root and sort each set of
+ siblings by sent date as described in section 2.2.
+ Traverse the messages in such a way that the "youngest" set
+ of siblings are sorted first, and the "oldest" set of
+ siblings are sorted last (grandchildren are sorted before
+ children, etc). In the case of a dummy message (which can
+ only occur with top-level siblings), use its first child
+ for sorting.
+
+ Example: C: A283 THREAD ORDEREDSUBJECT UTF-8 SINCE 5-MAR-2000
+ S: * THREAD (166)(167)(168)(169)(172)(170)(171)
+ (173)(174 (175)(176)(178)(181)(180))(179)(177
+ (183)(182)(188)(184)(185)(186)(187)(189))(190)
+ (191)(192)(193)(194 195)(196 (197)(198))(199)
+ (200 202)(201)(203)(204)(205)(206 207)(208)
+ S: A283 OK THREAD completed
+ C: A284 THREAD ORDEREDSUBJECT US-ASCII TEXT "gewp"
+ S: * THREAD
+ S: A284 OK THREAD completed
+ C: A285 THREAD REFERENCES UTF-8 SINCE 5-MAR-2000
+ S: * THREAD (166)(167)(168)(169)(172)((170)(179))
+ (171)(173)((174)(175)(176)(178)(181)(180))
+ ((177)(183)(182)(188 (184)(189))(185 186)(187))
+ (190)(191)(192)(193)((194)(195 196))(197 198)
+ (199)(200 202)(201)(203)(204)(205 206 207)(208)
+ S: A285 OK THREAD completed
+
+ Note: The line breaks in the first and third server
+ responses are for editorial clarity and do not appear in
+ real THREAD responses.
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 12]
+
+RFC 5256 IMAP Sort June 2008
+
+
+4. Additional Responses
+
+ These responses are extensions to the [IMAP] base protocol.
+
+ The section headings of these responses are intended to correspond
+ with where they would be located in the main document.
+
+BASE.7.2.SORT. SORT Response
+
+ Data: zero or more numbers
+
+ The SORT response occurs as a result of a SORT or UID SORT
+ command. The number(s) refer to those messages that match the
+ search criteria. For SORT, these are message sequence numbers;
+ for UID SORT, these are unique identifiers. Each number is
+ delimited by a space.
+
+ Example: S: * SORT 2 3 6
+
+BASE.7.2.THREAD. THREAD Response
+
+ Data: zero or more threads
+
+ The THREAD response occurs as a result of a THREAD or UID THREAD
+ command. It contains zero or more threads. A thread consists of
+ a parenthesized list of thread members.
+
+ Thread members consist of zero or more message numbers, delimited
+ by spaces, indicating successive parent and child. This continues
+ until the thread splits into multiple sub-threads, at which point,
+ the thread nests into multiple sub-threads with the first member
+ of each sub-thread being siblings at this level. There is no
+ limit to the nesting of threads.
+
+ The messages numbers refer to those messages that match the search
+ criteria. For THREAD, these are message sequence numbers; for UID
+ THREAD, these are unique identifiers.
+
+ Example: S: * THREAD (2)(3 6 (4 23)(44 7 96))
+
+ The first thread consists only of message 2. The second thread
+ consists of the messages 3 (parent) and 6 (child), after which it
+ splits into two sub-threads; the first of which contains messages
+ 4 (child of 6, sibling of 44) and 23 (child of 4), and the second
+ of which contains messages 44 (child of 6, sibling of 4), 7 (child
+ of 44), and 96 (child of 7). Since some later messages are
+ parents of earlier messages, the messages were probably moved from
+ some other mailbox at different times.
+
+
+
+Crispin & Murchison Standards Track [Page 13]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ -- 2
+
+ -- 3
+ \-- 6
+ |-- 4
+ | \-- 23
+ |
+ \-- 44
+ \-- 7
+ \-- 96
+
+ Example: S: * THREAD ((3)(5))
+
+ In this example, 3 and 5 are siblings of a parent that does not
+ match the search criteria (and/or does not exist in the mailbox);
+ however they are members of the same thread.
+
+5. Formal Syntax of SORT and THREAD Commands and Responses
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF]. It also uses [ABNF]
+ rules defined in [IMAP].
+
+sort = ["UID" SP] "SORT" SP sort-criteria SP search-criteria
+
+sort-criteria = "(" sort-criterion *(SP sort-criterion) ")"
+
+sort-criterion = ["REVERSE" SP] sort-key
+
+sort-key = "ARRIVAL" / "CC" / "DATE" / "FROM" / "SIZE" /
+ "SUBJECT" / "TO"
+
+thread = ["UID" SP] "THREAD" SP thread-alg SP search-criteria
+
+thread-alg = "ORDEREDSUBJECT" / "REFERENCES" / thread-alg-ext
+
+thread-alg-ext = atom
+ ; New algorithms MUST be registered with IANA
+
+search-criteria = charset 1*(SP search-key)
+
+charset = atom / quoted
+ ; CHARSET values MUST be registered with IANA
+
+sort-data = "SORT" *(SP nz-number)
+
+thread-data = "THREAD" [SP 1*thread-list]
+
+
+
+
+Crispin & Murchison Standards Track [Page 14]
+
+RFC 5256 IMAP Sort June 2008
+
+
+thread-list = "(" (thread-members / thread-nested) ")"
+
+thread-members = nz-number *(SP nz-number) [SP thread-nested]
+
+thread-nested = 2*thread-list
+
+ The following syntax describes base subject extraction rules (2)-(6):
+
+subject = *subj-leader [subj-middle] *subj-trailer
+
+subj-refwd = ("re" / ("fw" ["d"])) *WSP [subj-blob] ":"
+
+subj-blob = "[" *BLOBCHAR "]" *WSP
+
+subj-fwd = subj-fwd-hdr subject subj-fwd-trl
+
+subj-fwd-hdr = "[fwd:"
+
+subj-fwd-trl = "]"
+
+subj-leader = (*subj-blob subj-refwd) / WSP
+
+subj-middle = *subj-blob (subj-base / subj-fwd)
+ ; last subj-blob is subj-base if subj-base would
+ ; otherwise be empty
+
+subj-trailer = "(fwd)" / WSP
+
+subj-base = NONWSP *(*WSP NONWSP)
+ ; can be a subj-blob
+
+BLOBCHAR = %x01-5a / %x5c / %x5e-ff
+ ; any CHAR8 except '[' and ']'.
+ ; SHOULD comply with [UTF-8]
+
+NONWSP = %x01-08 / %x0a-1f / %x21-ff
+ ; any CHAR8 other than WSP.
+ ; SHOULD comply with [UTF-8]
+
+6. Security Considerations
+
+ The SORT and THREAD extensions do not raise any security
+ considerations that are not present in the base [IMAP] protocol, and
+ these issues are discussed in [IMAP]. Nevertheless, it is important
+ to remember that [IMAP] protocol transactions, including message
+ data, are sent in the clear over the network unless protection from
+ snooping is negotiated, either by the use of STARTTLS, privacy
+ protection in AUTHENTICATE, or some other protection mechanism.
+
+
+
+Crispin & Murchison Standards Track [Page 15]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ Although not a security consideration, it is important to recognize
+ that sorting by REFERENCES can lead to misleading threading trees.
+ For example, a message with false References: header data will cause
+ a thread to be incorporated into another thread.
+
+ The process of extracting the base subject may lead to incorrect
+ collation if the extracted data was significant text as opposed to a
+ subject artifact.
+
+7. Internationalization Considerations
+
+ As stated in the introduction, the rules of I18NLEVEL=1 as described
+ in [IMAP-I18N] MUST be followed; that is, the SORT and THREAD
+ extensions MUST collate strings according to the i;unicode-casemap
+ collation described in [UNICASEMAP]. Servers SHOULD also advertise
+ the I18NLEVEL=1 extension. Alternatively, a server MAY implement
+ I18NLEVEL=2 (or higher) and comply with the rules of that level.
+
+ As discussed in [IMAP-I18N] section 4.5, all server implementations
+ should eventually be updated to support the [IMAP-I18N] I18NLEVEL=2
+ extension.
+
+ Translations of the "re" or "fw"/"fwd" tokens are not specified for
+ removal in the base subject extraction process. An attempt to add
+ such translated tokens would result in a geometrically complex, and
+ ultimately unimplementable, task.
+
+ Instead, note that [RFC2822] section 3.6.5 recommends that "re:"
+ (from the Latin "res", meaning "in the matter of") be used to
+ identify a reply. Although it is evident that, from the multiple
+ forms of token to identify a forwarded message, there is considerable
+ variation found in the wild, the variations are (still) manageable.
+ Consequently, it is suggested that "re:" and one of the variations of
+ the tokens for a forward supported by the base subject extraction
+ rules be adopted for Internet mail messages, since doing so makes it
+ a simple display-time task to localize the token language for the
+ user.
+
+8. IANA Considerations
+
+ [IMAP] capabilities are registered by publishing a standards track or
+ IESG-approved experimental RFC. This document constitutes
+ registration of the SORT and THREAD capabilities in the [IMAP]
+ capabilities registry.
+
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 16]
+
+RFC 5256 IMAP Sort June 2008
+
+
+ This document creates a new [IMAP] threading algorithms registry,
+ which registers threading algorithms by publishing a standards track
+ or IESG-approved experimental RFC. This document constitutes
+ registration of the ORDEREDSUBJECT and REFERENCES algorithms in that
+ registry.
+
+9. Normative References
+
+ [ABNF] Crocker, D., Ed., and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", STD 68, RFC 5234, January
+ 2008.
+
+ [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration
+ Procedures", BCP 19, RFC 2978, October 2000.
+
+ [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [IMAP-I18N] Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet
+ Message Access Protocol Internationalization", RFC
+ 5255, June 2008.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2822] Resnick, P., Ed., "Internet Message Format", RFC 2822,
+ April 2001.
+
+ [UNICASEMAP] Crispin, M., "i;unicode-casemap - Simple Unicode
+ Collation Algorithm", RFC 5051, October 2007.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+10. Informative References
+
+ [IMAP-MODELS] Crispin, M., "Distributed Electronic Mail Models in
+ IMAP4", RFC 1733, December 1994.
+
+ [THREADING] Zawinski, J. "Message Threading",
+ http://www.jwz.org/doc/threading.html, 1997-2002.
+
+
+
+
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 17]
+
+RFC 5256 IMAP Sort June 2008
+
+
+Authors' Addresses
+
+ Mark R. Crispin
+ Panda Programming
+ 6158 NE Lariat Loop
+ Bainbridge Island, WA 98110-2098
+
+ Phone: +1 (206) 842-2385
+ EMail: IMAP+SORT+THREAD@Lingling.Panda.COM
+
+
+ Kenneth Murchison
+ Carnegie Mellon University
+ 5000 Forbes Avenue
+ Cyert Hall 285
+ Pittsburgh, PA 15213
+
+ Phone: +1 (412) 268-2638
+ EMail: murch@andrew.cmu.edu
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 18]
+
+RFC 5256 IMAP Sort June 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin & Murchison Standards Track [Page 19]
+
diff --git a/rfc/rfc5322.txt b/rfc/rfc5322.txt
@@ -0,0 +1,3195 @@
+
+
+
+
+
+
+Network Working Group P. Resnick, Ed.
+Request for Comments: 5322 Qualcomm Incorporated
+Obsoletes: 2822 October 2008
+Updates: 4021
+Category: Standards Track
+
+
+ Internet Message Format
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document specifies the Internet Message Format (IMF), a syntax
+ for text messages that are sent between computer users, within the
+ framework of "electronic mail" messages. This specification is a
+ revision of Request For Comments (RFC) 2822, which itself superseded
+ Request For Comments (RFC) 822, "Standard for the Format of ARPA
+ Internet Text Messages", updating it to reflect current practice and
+ incorporating incremental changes that were specified in other RFCs.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 1]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 5
+ 1.2.1. Requirements Notation . . . . . . . . . . . . . . . . 5
+ 1.2.2. Syntactic Notation . . . . . . . . . . . . . . . . . . 5
+ 1.2.3. Structure of This Document . . . . . . . . . . . . . . 5
+ 2. Lexical Analysis of Messages . . . . . . . . . . . . . . . . . 6
+ 2.1. General Description . . . . . . . . . . . . . . . . . . . 6
+ 2.1.1. Line Length Limits . . . . . . . . . . . . . . . . . . 7
+ 2.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 8
+ 2.2.1. Unstructured Header Field Bodies . . . . . . . . . . . 8
+ 2.2.2. Structured Header Field Bodies . . . . . . . . . . . . 8
+ 2.2.3. Long Header Fields . . . . . . . . . . . . . . . . . . 8
+ 2.3. Body . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
+ 3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.2. Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.2.1. Quoted characters . . . . . . . . . . . . . . . . . . 10
+ 3.2.2. Folding White Space and Comments . . . . . . . . . . . 11
+ 3.2.3. Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
+ 3.2.4. Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
+ 3.2.5. Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
+ 3.3. Date and Time Specification . . . . . . . . . . . . . . . 14
+ 3.4. Address Specification . . . . . . . . . . . . . . . . . . 16
+ 3.4.1. Addr-Spec Specification . . . . . . . . . . . . . . . 17
+ 3.5. Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
+ 3.6. Field Definitions . . . . . . . . . . . . . . . . . . . . 19
+ 3.6.1. The Origination Date Field . . . . . . . . . . . . . . 22
+ 3.6.2. Originator Fields . . . . . . . . . . . . . . . . . . 22
+ 3.6.3. Destination Address Fields . . . . . . . . . . . . . . 23
+ 3.6.4. Identification Fields . . . . . . . . . . . . . . . . 25
+ 3.6.5. Informational Fields . . . . . . . . . . . . . . . . . 27
+ 3.6.6. Resent Fields . . . . . . . . . . . . . . . . . . . . 28
+ 3.6.7. Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
+ 3.6.8. Optional Fields . . . . . . . . . . . . . . . . . . . 30
+ 4. Obsolete Syntax . . . . . . . . . . . . . . . . . . . . . . . 31
+ 4.1. Miscellaneous Obsolete Tokens . . . . . . . . . . . . . . 32
+ 4.2. Obsolete Folding White Space . . . . . . . . . . . . . . . 33
+ 4.3. Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
+ 4.4. Obsolete Addressing . . . . . . . . . . . . . . . . . . . 35
+ 4.5. Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
+ 4.5.1. Obsolete Origination Date Field . . . . . . . . . . . 36
+ 4.5.2. Obsolete Originator Fields . . . . . . . . . . . . . . 36
+ 4.5.3. Obsolete Destination Address Fields . . . . . . . . . 37
+ 4.5.4. Obsolete Identification Fields . . . . . . . . . . . . 37
+ 4.5.5. Obsolete Informational Fields . . . . . . . . . . . . 37
+
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+ 4.5.6. Obsolete Resent Fields . . . . . . . . . . . . . . . . 38
+ 4.5.7. Obsolete Trace Fields . . . . . . . . . . . . . . . . 38
+ 4.5.8. Obsolete optional fields . . . . . . . . . . . . . . . 38
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
+ Appendix A. Example Messages . . . . . . . . . . . . . . . . . 43
+ Appendix A.1. Addressing Examples . . . . . . . . . . . . . . . 44
+ Appendix A.1.1. A Message from One Person to Another with
+ Simple Addressing . . . . . . . . . . . . . . . . 44
+ Appendix A.1.2. Different Types of Mailboxes . . . . . . . . . . . 45
+ Appendix A.1.3. Group Addresses . . . . . . . . . . . . . . . . . 45
+ Appendix A.2. Reply Messages . . . . . . . . . . . . . . . . . . 46
+ Appendix A.3. Resent Messages . . . . . . . . . . . . . . . . . 47
+ Appendix A.4. Messages with Trace Fields . . . . . . . . . . . . 48
+ Appendix A.5. White Space, Comments, and Other Oddities . . . . 49
+ Appendix A.6. Obsoleted Forms . . . . . . . . . . . . . . . . . 50
+ Appendix A.6.1. Obsolete Addressing . . . . . . . . . . . . . . . 50
+ Appendix A.6.2. Obsolete Dates . . . . . . . . . . . . . . . . . . 50
+ Appendix A.6.3. Obsolete White Space and Comments . . . . . . . . 51
+ Appendix B. Differences from Earlier Specifications . . . . . 52
+ Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . 53
+ 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
+ 7.1. Normative References . . . . . . . . . . . . . . . . . . . 55
+ 7.2. Informative References . . . . . . . . . . . . . . . . . . 55
+
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+
+1. Introduction
+
+1.1. Scope
+
+ This document specifies the Internet Message Format (IMF), a syntax
+ for text messages that are sent between computer users, within the
+ framework of "electronic mail" messages. This specification is an
+ update to [RFC2822], which itself superseded [RFC0822], updating it
+ to reflect current practice and incorporating incremental changes
+ that were specified in other RFCs such as [RFC1123].
+
+ This document specifies a syntax only for text messages. In
+ particular, it makes no provision for the transmission of images,
+ audio, or other sorts of structured data in electronic mail messages.
+ There are several extensions published, such as the MIME document
+ series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
+ for the transmission of such data through electronic mail, either by
+ extending the syntax provided here or by structuring such messages to
+ conform to this syntax. Those mechanisms are outside of the scope of
+ this specification.
+
+ In the context of electronic mail, messages are viewed as having an
+ envelope and contents. The envelope contains whatever information is
+ needed to accomplish transmission and delivery. (See [RFC5321] for a
+ discussion of the envelope.) The contents comprise the object to be
+ delivered to the recipient. This specification applies only to the
+ format and some of the semantics of message contents. It contains no
+ specification of the information in the envelope.
+
+ However, some message systems may use information from the contents
+ to create the envelope. It is intended that this specification
+ facilitate the acquisition of such information by programs.
+
+ This specification is intended as a definition of what message
+ content format is to be passed between systems. Though some message
+ systems locally store messages in this format (which eliminates the
+ need for translation between formats) and others use formats that
+ differ from the one specified in this specification, local storage is
+ outside of the scope of this specification.
+
+ Note: This specification is not intended to dictate the internal
+ formats used by sites, the specific message system features that
+ they are expected to support, or any of the characteristics of
+ user interface programs that create or read messages. In
+ addition, this document does not specify an encoding of the
+ characters for either transport or storage; that is, it does not
+ specify the number of bits used or how those bits are specifically
+ transferred over the wire or stored on disk.
+
+
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+
+1.2. Notational Conventions
+
+1.2.1. Requirements Notation
+
+ This document occasionally uses terms that appear in capital letters.
+ When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
+ NOT", and "MAY" appear capitalized, they are being used to indicate
+ particular requirements of this specification. A discussion of the
+ meanings of these terms appears in [RFC2119].
+
+1.2.2. Syntactic Notation
+
+ This specification uses the Augmented Backus-Naur Form (ABNF)
+ [RFC5234] notation for the formal definitions of the syntax of
+ messages. Characters will be specified either by a decimal value
+ (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
+ a case-insensitive literal value enclosed in quotation marks (e.g.,
+ "A" for either uppercase or lowercase A).
+
+1.2.3. Structure of This Document
+
+ This document is divided into several sections.
+
+ This section, section 1, is a short introduction to the document.
+
+ Section 2 lays out the general description of a message and its
+ constituent parts. This is an overview to help the reader understand
+ some of the general principles used in the later portions of this
+ document. Any examples in this section MUST NOT be taken as
+ specification of the formal syntax of any part of a message.
+
+ Section 3 specifies formal ABNF rules for the structure of each part
+ of a message (the syntax) and describes the relationship between
+ those parts and their meaning in the context of a message (the
+ semantics). That is, it lays out the actual rules for the structure
+ of each part of a message (the syntax) as well as a description of
+ the parts and instructions for their interpretation (the semantics).
+ This includes analysis of the syntax and semantics of subparts of
+ messages that have specific structure. The syntax included in
+ section 3 represents messages as they MUST be created. There are
+ also notes in section 3 to indicate if any of the options specified
+ in the syntax SHOULD be used over any of the others.
+
+ Both sections 2 and 3 describe messages that are legal to generate
+ for purposes of this specification.
+
+
+
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+ Section 4 of this document specifies an "obsolete" syntax. There are
+ references in section 3 to these obsolete syntactic elements. The
+ rules of the obsolete syntax are elements that have appeared in
+ earlier versions of this specification or have previously been widely
+ used in Internet messages. As such, these elements MUST be
+ interpreted by parsers of messages in order to be conformant to this
+ specification. However, since items in this syntax have been
+ determined to be non-interoperable or to cause significant problems
+ for recipients of messages, they MUST NOT be generated by creators of
+ conformant messages.
+
+ Section 5 details security considerations to take into account when
+ implementing this specification.
+
+ Appendix A lists examples of different sorts of messages. These
+ examples are not exhaustive of the types of messages that appear on
+ the Internet, but give a broad overview of certain syntactic forms.
+
+ Appendix B lists the differences between this specification and
+ earlier specifications for Internet messages.
+
+ Appendix C contains acknowledgements.
+
+2. Lexical Analysis of Messages
+
+2.1. General Description
+
+ At the most basic level, a message is a series of characters. A
+ message that is conformant with this specification is composed of
+ characters with values in the range of 1 through 127 and interpreted
+ as US-ASCII [ANSI.X3-4.1986] characters. For brevity, this document
+ sometimes refers to this range of characters as simply "US-ASCII
+ characters".
+
+ Note: This document specifies that messages are made up of
+ characters in the US-ASCII range of 1 through 127. There are
+ other documents, specifically the MIME document series ([RFC2045],
+ [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]), that
+ extend this specification to allow for values outside of that
+ range. Discussion of those mechanisms is not within the scope of
+ this specification.
+
+ Messages are divided into lines of characters. A line is a series of
+ characters that is delimited with the two characters carriage-return
+ and line-feed; that is, the carriage return (CR) character (ASCII
+ value 13) followed immediately by the line feed (LF) character (ASCII
+ value 10). (The carriage return/line feed pair is usually written in
+ this document as "CRLF".)
+
+
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+ A message consists of header fields (collectively called "the header
+ section of the message") followed, optionally, by a body. The header
+ section is a sequence of lines of characters with special syntax as
+ defined in this specification. The body is simply a sequence of
+ characters that follows the header section and is separated from the
+ header section by an empty line (i.e., a line with nothing preceding
+ the CRLF).
+
+ Note: Common parlance and earlier versions of this specification
+ use the term "header" to either refer to the entire header section
+ or to refer to an individual header field. To avoid ambiguity,
+ this document does not use the terms "header" or "headers" in
+ isolation, but instead always uses "header field" to refer to the
+ individual field and "header section" to refer to the entire
+ collection.
+
+2.1.1. Line Length Limits
+
+ There are two limits that this specification places on the number of
+ characters in a line. Each line of characters MUST be no more than
+ 998 characters, and SHOULD be no more than 78 characters, excluding
+ the CRLF.
+
+ The 998 character limit is due to limitations in many implementations
+ that send, receive, or store IMF messages which simply cannot handle
+ more than 998 characters on a line. Receiving implementations would
+ do well to handle an arbitrarily large number of characters in a line
+ for robustness sake. However, there are so many implementations that
+ (in compliance with the transport requirements of [RFC5321]) do not
+ accept messages containing more than 1000 characters including the CR
+ and LF per line, it is important for implementations not to create
+ such messages.
+
+ The more conservative 78 character recommendation is to accommodate
+ the many implementations of user interfaces that display these
+ messages which may truncate, or disastrously wrap, the display of
+ more than 78 characters per line, in spite of the fact that such
+ implementations are non-conformant to the intent of this
+ specification (and that of [RFC5321] if they actually cause
+ information to be lost). Again, even though this limitation is put
+ on messages, it is incumbent upon implementations that display
+ messages to handle an arbitrarily large number of characters in a
+ line (certainly at least up to the 998 character limit) for the sake
+ of robustness.
+
+
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+2.2. Header Fields
+
+ Header fields are lines beginning with a field name, followed by a
+ colon (":"), followed by a field body, and terminated by CRLF. A
+ field name MUST be composed of printable US-ASCII characters (i.e.,
+ characters that have values between 33 and 126, inclusive), except
+ colon. A field body may be composed of printable US-ASCII characters
+ as well as the space (SP, ASCII value 32) and horizontal tab (HTAB,
+ ASCII value 9) characters (together known as the white space
+ characters, WSP). A field body MUST NOT include CR and LF except
+ when used in "folding" and "unfolding", as described in section
+ 2.2.3. All field bodies MUST conform to the syntax described in
+ sections 3 and 4 of this specification.
+
+2.2.1. Unstructured Header Field Bodies
+
+ Some field bodies in this specification are defined simply as
+ "unstructured" (which is specified in section 3.2.5 as any printable
+ US-ASCII characters plus white space characters) with no further
+ restrictions. These are referred to as unstructured field bodies.
+ Semantically, unstructured field bodies are simply to be treated as a
+ single line of characters with no further processing (except for
+ "folding" and "unfolding" as described in section 2.2.3).
+
+2.2.2. Structured Header Field Bodies
+
+ Some field bodies in this specification have a syntax that is more
+ restrictive than the unstructured field bodies described above.
+ These are referred to as "structured" field bodies. Structured field
+ bodies are sequences of specific lexical tokens as described in
+ sections 3 and 4 of this specification. Many of these tokens are
+ allowed (according to their syntax) to be introduced or end with
+ comments (as described in section 3.2.2) as well as the white space
+ characters, and those white space characters are subject to "folding"
+ and "unfolding" as described in section 2.2.3. Semantic analysis of
+ structured field bodies is given along with their syntax.
+
+2.2.3. Long Header Fields
+
+ Each header field is logically a single line of characters comprising
+ the field name, the colon, and the field body. For convenience
+ however, and to deal with the 998/78 character limitations per line,
+ the field body portion of a header field can be split into a
+ multiple-line representation; this is called "folding". The general
+ rule is that wherever this specification allows for folding white
+ space (not simply WSP characters), a CRLF may be inserted before any
+ WSP.
+
+
+
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+ For example, the header field:
+
+ Subject: This is a test
+
+ can be represented as:
+
+ Subject: This
+ is a test
+
+ Note: Though structured field bodies are defined in such a way
+ that folding can take place between many of the lexical tokens
+ (and even within some of the lexical tokens), folding SHOULD be
+ limited to placing the CRLF at higher-level syntactic breaks. For
+ instance, if a field body is defined as comma-separated values, it
+ is recommended that folding occur after the comma separating the
+ structured items in preference to other places where the field
+ could be folded, even if it is allowed elsewhere.
+
+ The process of moving from this folded multiple-line representation
+ of a header field to its single line representation is called
+ "unfolding". Unfolding is accomplished by simply removing any CRLF
+ that is immediately followed by WSP. Each header field should be
+ treated in its unfolded form for further syntactic and semantic
+ evaluation. An unfolded header field has no length restriction and
+ therefore may be indeterminately long.
+
+2.3. Body
+
+ The body of a message is simply lines of US-ASCII characters. The
+ only two limitations on the body are as follows:
+
+ o CR and LF MUST only occur together as CRLF; they MUST NOT appear
+ independently in the body.
+ o Lines of characters in the body MUST be limited to 998 characters,
+ and SHOULD be limited to 78 characters, excluding the CRLF.
+
+ Note: As was stated earlier, there are other documents,
+ specifically the MIME documents ([RFC2045], [RFC2046], [RFC2049],
+ [RFC4288], [RFC4289]), that extend (and limit) this specification
+ to allow for different sorts of message bodies. Again, these
+ mechanisms are beyond the scope of this document.
+
+
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+3. Syntax
+
+3.1. Introduction
+
+ The syntax as given in this section defines the legal syntax of
+ Internet messages. Messages that are conformant to this
+ specification MUST conform to the syntax in this section. If there
+ are options in this section where one option SHOULD be generated,
+ that is indicated either in the prose or in a comment next to the
+ syntax.
+
+ For the defined expressions, a short description of the syntax and
+ use is given, followed by the syntax in ABNF, followed by a semantic
+ analysis. The following primitive tokens that are used but otherwise
+ unspecified are taken from the "Core Rules" of [RFC5234], Appendix
+ B.1: CR, LF, CRLF, HTAB, SP, WSP, DQUOTE, DIGIT, ALPHA, and VCHAR.
+
+ In some of the definitions, there will be non-terminals whose names
+ start with "obs-". These "obs-" elements refer to tokens defined in
+ the obsolete syntax in section 4. In all cases, these productions
+ are to be ignored for the purposes of generating legal Internet
+ messages and MUST NOT be used as part of such a message. However,
+ when interpreting messages, these tokens MUST be honored as part of
+ the legal syntax. In this sense, section 3 defines a grammar for the
+ generation of messages, with "obs-" elements that are to be ignored,
+ while section 4 adds grammar for the interpretation of messages.
+
+3.2. Lexical Tokens
+
+ The following rules are used to define an underlying lexical
+ analyzer, which feeds tokens to the higher-level parsers. This
+ section defines the tokens used in structured header field bodies.
+
+ Note: Readers of this specification need to pay special attention
+ to how these lexical tokens are used in both the lower-level and
+ higher-level syntax later in the document. Particularly, the
+ white space tokens and the comment tokens defined in section 3.2.2
+ get used in the lower-level tokens defined here, and those lower-
+ level tokens are in turn used as parts of the higher-level tokens
+ defined later. Therefore, white space and comments may be allowed
+ in the higher-level tokens even though they may not explicitly
+ appear in a particular definition.
+
+3.2.1. Quoted characters
+
+ Some characters are reserved for special interpretation, such as
+ delimiting lexical tokens. To permit use of these characters as
+ uninterpreted data, a quoting mechanism is provided.
+
+
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+ quoted-pair = ("\" (VCHAR / WSP)) / obs-qp
+
+ Where any quoted-pair appears, it is to be interpreted as the
+ character alone. That is to say, the "\" character that appears as
+ part of a quoted-pair is semantically "invisible".
+
+ Note: The "\" character may appear in a message where it is not
+ part of a quoted-pair. A "\" character that does not appear in a
+ quoted-pair is not semantically invisible. The only places in
+ this specification where quoted-pair currently appears are
+ ccontent, qcontent, and in obs-dtext in section 4.
+
+3.2.2. Folding White Space and Comments
+
+ White space characters, including white space used in folding
+ (described in section 2.2.3), may appear between many elements in
+ header field bodies. Also, strings of characters that are treated as
+ comments may be included in structured field bodies as characters
+ enclosed in parentheses. The following defines the folding white
+ space (FWS) and comment constructs.
+
+ Strings of characters enclosed in parentheses are considered comments
+ so long as they do not appear within a "quoted-string", as defined in
+ section 3.2.4. Comments may nest.
+
+ There are several places in this specification where comments and FWS
+ may be freely inserted. To accommodate that syntax, an additional
+ token for "CFWS" is defined for places where comments and/or FWS can
+ occur. However, where CFWS occurs in this specification, it MUST NOT
+ be inserted in such a way that any line of a folded header field is
+ made up entirely of WSP characters and nothing else.
+
+ FWS = ([*WSP CRLF] 1*WSP) / obs-FWS
+ ; Folding white space
+
+ ctext = %d33-39 / ; Printable US-ASCII
+ %d42-91 / ; characters not including
+ %d93-126 / ; "(", ")", or "\"
+ obs-ctext
+
+ ccontent = ctext / quoted-pair / comment
+
+ comment = "(" *([FWS] ccontent) [FWS] ")"
+
+ CFWS = (1*([FWS] comment) [FWS]) / FWS
+
+
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+ Throughout this specification, where FWS (the folding white space
+ token) appears, it indicates a place where folding, as discussed in
+ section 2.2.3, may take place. Wherever folding appears in a message
+ (that is, a header field body containing a CRLF followed by any WSP),
+ unfolding (removal of the CRLF) is performed before any further
+ semantic analysis is performed on that header field according to this
+ specification. That is to say, any CRLF that appears in FWS is
+ semantically "invisible".
+
+ A comment is normally used in a structured field body to provide some
+ human-readable informational text. Since a comment is allowed to
+ contain FWS, folding is permitted within the comment. Also note that
+ since quoted-pair is allowed in a comment, the parentheses and
+ backslash characters may appear in a comment, so long as they appear
+ as a quoted-pair. Semantically, the enclosing parentheses are not
+ part of the comment; the comment is what is contained between the two
+ parentheses. As stated earlier, the "\" in any quoted-pair and the
+ CRLF in any FWS that appears within the comment are semantically
+ "invisible" and therefore not part of the comment either.
+
+ Runs of FWS, comment, or CFWS that occur between lexical tokens in a
+ structured header field are semantically interpreted as a single
+ space character.
+
+3.2.3. Atom
+
+ Several productions in structured header field bodies are simply
+ strings of certain basic characters. Such productions are called
+ atoms.
+
+ Some of the structured header field bodies also allow the period
+ character (".", ASCII value 46) within runs of atext. An additional
+ "dot-atom" token is defined for those purposes.
+
+ Note: The "specials" token does not appear anywhere else in this
+ specification. It is simply the visible (i.e., non-control, non-
+ white space) characters that do not appear in atext. It is
+ provided only because it is useful for implementers who use tools
+ that lexically analyze messages. Each of the characters in
+ specials can be used to indicate a tokenization point in lexical
+ analysis.
+
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+ atext = ALPHA / DIGIT / ; Printable US-ASCII
+ "!" / "#" / ; characters not including
+ "$" / "%" / ; specials. Used for atoms.
+ "&" / "'" /
+ "*" / "+" /
+ "-" / "/" /
+ "=" / "?" /
+ "^" / "_" /
+ "`" / "{" /
+ "|" / "}" /
+ "~"
+
+ atom = [CFWS] 1*atext [CFWS]
+
+ dot-atom-text = 1*atext *("." 1*atext)
+
+ dot-atom = [CFWS] dot-atom-text [CFWS]
+
+ specials = "(" / ")" / ; Special characters that do
+ "<" / ">" / ; not appear in atext
+ "[" / "]" /
+ ":" / ";" /
+ "@" / "\" /
+ "," / "." /
+ DQUOTE
+
+ Both atom and dot-atom are interpreted as a single unit, comprising
+ the string of characters that make it up. Semantically, the optional
+ comments and FWS surrounding the rest of the characters are not part
+ of the atom; the atom is only the run of atext characters in an atom,
+ or the atext and "." characters in a dot-atom.
+
+3.2.4. Quoted Strings
+
+ Strings of characters that include characters other than those
+ allowed in atoms can be represented in a quoted string format, where
+ the characters are surrounded by quote (DQUOTE, ASCII value 34)
+ characters.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 13]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ qtext = %d33 / ; Printable US-ASCII
+ %d35-91 / ; characters not including
+ %d93-126 / ; "\" or the quote character
+ obs-qtext
+
+ qcontent = qtext / quoted-pair
+
+ quoted-string = [CFWS]
+ DQUOTE *([FWS] qcontent) [FWS] DQUOTE
+ [CFWS]
+
+ A quoted-string is treated as a unit. That is, quoted-string is
+ identical to atom, semantically. Since a quoted-string is allowed to
+ contain FWS, folding is permitted. Also note that since quoted-pair
+ is allowed in a quoted-string, the quote and backslash characters may
+ appear in a quoted-string so long as they appear as a quoted-pair.
+
+ Semantically, neither the optional CFWS outside of the quote
+ characters nor the quote characters themselves are part of the
+ quoted-string; the quoted-string is what is contained between the two
+ quote characters. As stated earlier, the "\" in any quoted-pair and
+ the CRLF in any FWS/CFWS that appears within the quoted-string are
+ semantically "invisible" and therefore not part of the quoted-string
+ either.
+
+3.2.5. Miscellaneous Tokens
+
+ Three additional tokens are defined: word and phrase for combinations
+ of atoms and/or quoted-strings, and unstructured for use in
+ unstructured header fields and in some places within structured
+ header fields.
+
+ word = atom / quoted-string
+
+ phrase = 1*word / obs-phrase
+
+ unstructured = (*([FWS] VCHAR) *WSP) / obs-unstruct
+
+3.3. Date and Time Specification
+
+ Date and time values occur in several header fields. This section
+ specifies the syntax for a full date and time specification. Though
+ folding white space is permitted throughout the date-time
+ specification, it is RECOMMENDED that a single space be used in each
+ place that FWS appears (whether it is required or optional); some
+ older implementations will not interpret longer sequences of folding
+ white space correctly.
+
+
+
+
+Resnick Standards Track [Page 14]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ date-time = [ day-of-week "," ] date time [CFWS]
+
+ day-of-week = ([FWS] day-name) / obs-day-of-week
+
+ day-name = "Mon" / "Tue" / "Wed" / "Thu" /
+ "Fri" / "Sat" / "Sun"
+
+ date = day month year
+
+ day = ([FWS] 1*2DIGIT FWS) / obs-day
+
+ month = "Jan" / "Feb" / "Mar" / "Apr" /
+ "May" / "Jun" / "Jul" / "Aug" /
+ "Sep" / "Oct" / "Nov" / "Dec"
+
+ year = (FWS 4*DIGIT FWS) / obs-year
+
+ time = time-of-day zone
+
+ time-of-day = hour ":" minute [ ":" second ]
+
+ hour = 2DIGIT / obs-hour
+
+ minute = 2DIGIT / obs-minute
+
+ second = 2DIGIT / obs-second
+
+ zone = (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
+
+ The day is the numeric day of the month. The year is any numeric
+ year 1900 or later.
+
+ The time-of-day specifies the number of hours, minutes, and
+ optionally seconds since midnight of the date indicated.
+
+ The date and time-of-day SHOULD express local time.
+
+ The zone specifies the offset from Coordinated Universal Time (UTC,
+ formerly referred to as "Greenwich Mean Time") that the date and
+ time-of-day represent. The "+" or "-" indicates whether the time-of-
+ day is ahead of (i.e., east of) or behind (i.e., west of) Universal
+ Time. The first two digits indicate the number of hours difference
+ from Universal Time, and the last two digits indicate the number of
+ additional minutes difference from Universal Time. (Hence, +hhmm
+ means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
+ minutes). The form "+0000" SHOULD be used to indicate a time zone at
+ Universal Time. Though "-0000" also indicates Universal Time, it is
+
+
+
+
+Resnick Standards Track [Page 15]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ used to indicate that the time was generated on a system that may be
+ in a local time zone other than Universal Time and that the date-time
+ contains no information about the local time zone.
+
+ A date-time specification MUST be semantically valid. That is, the
+ day-of-week (if included) MUST be the day implied by the date, the
+ numeric day-of-month MUST be between 1 and the number of days allowed
+ for the specified month (in the specified year), the time-of-day MUST
+ be in the range 00:00:00 through 23:59:60 (the number of seconds
+ allowing for a leap second; see [RFC1305]), and the last two digits
+ of the zone MUST be within the range 00 through 59.
+
+3.4. Address Specification
+
+ Addresses occur in several message header fields to indicate senders
+ and recipients of messages. An address may either be an individual
+ mailbox, or a group of mailboxes.
+
+ address = mailbox / group
+
+ mailbox = name-addr / addr-spec
+
+ name-addr = [display-name] angle-addr
+
+ angle-addr = [CFWS] "<" addr-spec ">" [CFWS] /
+ obs-angle-addr
+
+ group = display-name ":" [group-list] ";" [CFWS]
+
+ display-name = phrase
+
+ mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
+
+ address-list = (address *("," address)) / obs-addr-list
+
+ group-list = mailbox-list / CFWS / obs-group-list
+
+ A mailbox receives mail. It is a conceptual entity that does not
+ necessarily pertain to file storage. For example, some sites may
+ choose to print mail on a printer and deliver the output to the
+ addressee's desk.
+
+ Normally, a mailbox is composed of two parts: (1) an optional display
+ name that indicates the name of the recipient (which can be a person
+ or a system) that could be displayed to the user of a mail
+ application, and (2) an addr-spec address enclosed in angle brackets
+
+
+
+
+
+Resnick Standards Track [Page 16]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ ("<" and ">"). There is an alternate simple form of a mailbox where
+ the addr-spec address appears alone, without the recipient's name or
+ the angle brackets. The Internet addr-spec address is described in
+ section 3.4.1.
+
+ Note: Some legacy implementations used the simple form where the
+ addr-spec appears without the angle brackets, but included the
+ name of the recipient in parentheses as a comment following the
+ addr-spec. Since the meaning of the information in a comment is
+ unspecified, implementations SHOULD use the full name-addr form of
+ the mailbox, instead of the legacy form, to specify the display
+ name associated with a mailbox. Also, because some legacy
+ implementations interpret the comment, comments generally SHOULD
+ NOT be used in address fields to avoid confusing such
+ implementations.
+
+ When it is desirable to treat several mailboxes as a single unit
+ (i.e., in a distribution list), the group construct can be used. The
+ group construct allows the sender to indicate a named group of
+ recipients. This is done by giving a display name for the group,
+ followed by a colon, followed by a comma-separated list of any number
+ of mailboxes (including zero and one), and ending with a semicolon.
+ Because the list of mailboxes can be empty, using the group construct
+ is also a simple way to communicate to recipients that the message
+ was sent to one or more named sets of recipients, without actually
+ providing the individual mailbox address for any of those recipients.
+
+3.4.1. Addr-Spec Specification
+
+ An addr-spec is a specific Internet identifier that contains a
+ locally interpreted string followed by the at-sign character ("@",
+ ASCII value 64) followed by an Internet domain. The locally
+ interpreted string is either a quoted-string or a dot-atom. If the
+ string can be represented as a dot-atom (that is, it contains no
+ characters other than atext characters or "." surrounded by atext
+ characters), then the dot-atom form SHOULD be used and the quoted-
+ string form SHOULD NOT be used. Comments and folding white space
+ SHOULD NOT be used around the "@" in the addr-spec.
+
+ Note: A liberal syntax for the domain portion of addr-spec is
+ given here. However, the domain portion contains addressing
+ information specified by and used in other protocols (e.g.,
+ [RFC1034], [RFC1035], [RFC1123], [RFC5321]). It is therefore
+ incumbent upon implementations to conform to the syntax of
+ addresses for the context in which they are used.
+
+
+
+
+
+
+Resnick Standards Track [Page 17]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ addr-spec = local-part "@" domain
+
+ local-part = dot-atom / quoted-string / obs-local-part
+
+ domain = dot-atom / domain-literal / obs-domain
+
+ domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
+
+ dtext = %d33-90 / ; Printable US-ASCII
+ %d94-126 / ; characters not including
+ obs-dtext ; "[", "]", or "\"
+
+ The domain portion identifies the point to which the mail is
+ delivered. In the dot-atom form, this is interpreted as an Internet
+ domain name (either a host name or a mail exchanger name) as
+ described in [RFC1034], [RFC1035], and [RFC1123]. In the domain-
+ literal form, the domain is interpreted as the literal Internet
+ address of the particular host. In both cases, how addressing is
+ used and how messages are transported to a particular host is covered
+ in separate documents, such as [RFC5321]. These mechanisms are
+ outside of the scope of this document.
+
+ The local-part portion is a domain-dependent string. In addresses,
+ it is simply interpreted on the particular host as a name of a
+ particular mailbox.
+
+3.5. Overall Message Syntax
+
+ A message consists of header fields, optionally followed by a message
+ body. Lines in a message MUST be a maximum of 998 characters
+ excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
+ characters excluding the CRLF. (See section 2.1.1 for explanation.)
+ In a message body, though all of the characters listed in the text
+ rule MAY be used, the use of US-ASCII control characters (values 1
+ through 8, 11, 12, and 14 through 31) is discouraged since their
+ interpretation by receivers for display is not guaranteed.
+
+ message = (fields / obs-fields)
+ [CRLF body]
+
+ body = (*(*998text CRLF) *998text) / obs-body
+
+ text = %d1-9 / ; Characters excluding CR
+ %d11 / ; and LF
+ %d12 /
+ %d14-127
+
+
+
+
+
+Resnick Standards Track [Page 18]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ The header fields carry most of the semantic information and are
+ defined in section 3.6. The body is simply a series of lines of text
+ that are uninterpreted for the purposes of this specification.
+
+3.6. Field Definitions
+
+ The header fields of a message are defined here. All header fields
+ have the same general syntactic structure: a field name, followed by
+ a colon, followed by the field body. The specific syntax for each
+ header field is defined in the subsequent sections.
+
+ Note: In the ABNF syntax for each field in subsequent sections,
+ each field name is followed by the required colon. However, for
+ brevity, sometimes the colon is not referred to in the textual
+ description of the syntax. It is, nonetheless, required.
+
+ It is important to note that the header fields are not guaranteed to
+ be in a particular order. They may appear in any order, and they
+ have been known to be reordered occasionally when transported over
+ the Internet. However, for the purposes of this specification,
+ header fields SHOULD NOT be reordered when a message is transported
+ or transformed. More importantly, the trace header fields and resent
+ header fields MUST NOT be reordered, and SHOULD be kept in blocks
+ prepended to the message. See sections 3.6.6 and 3.6.7 for more
+ information.
+
+ The only required header fields are the origination date field and
+ the originator address field(s). All other header fields are
+ syntactically optional. More information is contained in the table
+ following this definition.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 19]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ fields = *(trace
+ *optional-field /
+ *(resent-date /
+ resent-from /
+ resent-sender /
+ resent-to /
+ resent-cc /
+ resent-bcc /
+ resent-msg-id))
+ *(orig-date /
+ from /
+ sender /
+ reply-to /
+ to /
+ cc /
+ bcc /
+ message-id /
+ in-reply-to /
+ references /
+ subject /
+ comments /
+ keywords /
+ optional-field)
+
+ The following table indicates limits on the number of times each
+ field may occur in the header section of a message as well as any
+ special limitations on the use of those fields. An asterisk ("*")
+ next to a value in the minimum or maximum column indicates that a
+ special restriction appears in the Notes column.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 20]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ +----------------+--------+------------+----------------------------+
+ | Field | Min | Max number | Notes |
+ | | number | | |
+ +----------------+--------+------------+----------------------------+
+ | trace | 0 | unlimited | Block prepended - see |
+ | | | | 3.6.7 |
+ | resent-date | 0* | unlimited* | One per block, required if |
+ | | | | other resent fields are |
+ | | | | present - see 3.6.6 |
+ | resent-from | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-sender | 0* | unlimited* | One per block, MUST occur |
+ | | | | with multi-address |
+ | | | | resent-from - see 3.6.6 |
+ | resent-to | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-cc | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-bcc | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-msg-id | 0 | unlimited* | One per block - see 3.6.6 |
+ | orig-date | 1 | 1 | |
+ | from | 1 | 1 | See sender and 3.6.2 |
+ | sender | 0* | 1 | MUST occur with |
+ | | | | multi-address from - see |
+ | | | | 3.6.2 |
+ | reply-to | 0 | 1 | |
+ | to | 0 | 1 | |
+ | cc | 0 | 1 | |
+ | bcc | 0 | 1 | |
+ | message-id | 0* | 1 | SHOULD be present - see |
+ | | | | 3.6.4 |
+ | in-reply-to | 0* | 1 | SHOULD occur in some |
+ | | | | replies - see 3.6.4 |
+ | references | 0* | 1 | SHOULD occur in some |
+ | | | | replies - see 3.6.4 |
+ | subject | 0 | 1 | |
+ | comments | 0 | unlimited | |
+ | keywords | 0 | unlimited | |
+ | optional-field | 0 | unlimited | |
+ +----------------+--------+------------+----------------------------+
+
+ The exact interpretation of each field is described in subsequent
+ sections.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 21]
+
+RFC 5322 Internet Message Format October 2008
+
+
+3.6.1. The Origination Date Field
+
+ The origination date field consists of the field name "Date" followed
+ by a date-time specification.
+
+ orig-date = "Date:" date-time CRLF
+
+ The origination date specifies the date and time at which the creator
+ of the message indicated that the message was complete and ready to
+ enter the mail delivery system. For instance, this might be the time
+ that a user pushes the "send" or "submit" button in an application
+ program. In any case, it is specifically not intended to convey the
+ time that the message is actually transported, but rather the time at
+ which the human or other creator of the message has put the message
+ into its final form, ready for transport. (For example, a portable
+ computer user who is not connected to a network might queue a message
+ for delivery. The origination date is intended to contain the date
+ and time that the user queued the message, not the time when the user
+ connected to the network to send the message.)
+
+3.6.2. Originator Fields
+
+ The originator fields of a message consist of the from field, the
+ sender field (when applicable), and optionally the reply-to field.
+ The from field consists of the field name "From" and a comma-
+ separated list of one or more mailbox specifications. If the from
+ field contains more than one mailbox specification in the mailbox-
+ list, then the sender field, containing the field name "Sender" and a
+ single mailbox specification, MUST appear in the message. In either
+ case, an optional reply-to field MAY also be included, which contains
+ the field name "Reply-To" and a comma-separated list of one or more
+ addresses.
+
+ from = "From:" mailbox-list CRLF
+
+ sender = "Sender:" mailbox CRLF
+
+ reply-to = "Reply-To:" address-list CRLF
+
+ The originator fields indicate the mailbox(es) of the source of the
+ message. The "From:" field specifies the author(s) of the message,
+ that is, the mailbox(es) of the person(s) or system(s) responsible
+ for the writing of the message. The "Sender:" field specifies the
+ mailbox of the agent responsible for the actual transmission of the
+ message. For example, if a secretary were to send a message for
+ another person, the mailbox of the secretary would appear in the
+ "Sender:" field and the mailbox of the actual author would appear in
+ the "From:" field. If the originator of the message can be indicated
+
+
+
+Resnick Standards Track [Page 22]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ by a single mailbox and the author and transmitter are identical, the
+ "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
+ appear.
+
+ Note: The transmitter information is always present. The absence
+ of the "Sender:" field is sometimes mistakenly taken to mean that
+ the agent responsible for transmission of the message has not been
+ specified. This absence merely means that the transmitter is
+ identical to the author and is therefore not redundantly placed
+ into the "Sender:" field.
+
+ The originator fields also provide the information required when
+ replying to a message. When the "Reply-To:" field is present, it
+ indicates the address(es) to which the author of the message suggests
+ that replies be sent. In the absence of the "Reply-To:" field,
+ replies SHOULD by default be sent to the mailbox(es) specified in the
+ "From:" field unless otherwise specified by the person composing the
+ reply.
+
+ In all cases, the "From:" field SHOULD NOT contain any mailbox that
+ does not belong to the author(s) of the message. See also section
+ 3.6.3 for more information on forming the destination addresses for a
+ reply.
+
+3.6.3. Destination Address Fields
+
+ The destination fields of a message consist of three possible fields,
+ each of the same form: the field name, which is either "To", "Cc", or
+ "Bcc", followed by a comma-separated list of one or more addresses
+ (either mailbox or group syntax).
+
+ to = "To:" address-list CRLF
+
+ cc = "Cc:" address-list CRLF
+
+ bcc = "Bcc:" [address-list / CFWS] CRLF
+
+ The destination fields specify the recipients of the message. Each
+ destination field may have one or more addresses, and the addresses
+ indicate the intended recipients of the message. The only difference
+ between the three fields is how each is used.
+
+ The "To:" field contains the address(es) of the primary recipient(s)
+ of the message.
+
+
+
+
+
+
+
+Resnick Standards Track [Page 23]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
+ making a copy on a typewriter using carbon paper) contains the
+ addresses of others who are to receive the message, though the
+ content of the message may not be directed at them.
+
+ The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
+ addresses of recipients of the message whose addresses are not to be
+ revealed to other recipients of the message. There are three ways in
+ which the "Bcc:" field is used. In the first case, when a message
+ containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
+ removed even though all of the recipients (including those specified
+ in the "Bcc:" field) are sent a copy of the message. In the second
+ case, recipients specified in the "To:" and "Cc:" lines each are sent
+ a copy of the message with the "Bcc:" line removed as above, but the
+ recipients on the "Bcc:" line get a separate copy of the message
+ containing a "Bcc:" line. (When there are multiple recipient
+ addresses in the "Bcc:" field, some implementations actually send a
+ separate copy of the message to each recipient with a "Bcc:"
+ containing only the address of that particular recipient.) Finally,
+ since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
+ sent without any addresses indicating to the recipients that blind
+ copies were sent to someone. Which method to use with "Bcc:" fields
+ is implementation dependent, but refer to the "Security
+ Considerations" section of this document for a discussion of each.
+
+ When a message is a reply to another message, the mailboxes of the
+ authors of the original message (the mailboxes in the "From:" field)
+ or mailboxes specified in the "Reply-To:" field (if it exists) MAY
+ appear in the "To:" field of the reply since these would normally be
+ the primary recipients of the reply. If a reply is sent to a message
+ that has destination fields, it is often desirable to send a copy of
+ the reply to all of the recipients of the message, in addition to the
+ author. When such a reply is formed, addresses in the "To:" and
+ "Cc:" fields of the original message MAY appear in the "Cc:" field of
+ the reply, since these are normally secondary recipients of the
+ reply. If a "Bcc:" field is present in the original message,
+ addresses in that field MAY appear in the "Bcc:" field of the reply,
+ but they SHOULD NOT appear in the "To:" or "Cc:" fields.
+
+ Note: Some mail applications have automatic reply commands that
+ include the destination addresses of the original message in the
+ destination addresses of the reply. How those reply commands
+ behave is implementation dependent and is beyond the scope of this
+ document. In particular, whether or not to include the original
+ destination addresses when the original message had a "Reply-To:"
+ field is not addressed here.
+
+
+
+
+
+Resnick Standards Track [Page 24]
+
+RFC 5322 Internet Message Format October 2008
+
+
+3.6.4. Identification Fields
+
+ Though listed as optional in the table in section 3.6, every message
+ SHOULD have a "Message-ID:" field. Furthermore, reply messages
+ SHOULD have "In-Reply-To:" and "References:" fields as appropriate
+ and as described below.
+
+ The "Message-ID:" field contains a single unique message identifier.
+ The "References:" and "In-Reply-To:" fields each contain one or more
+ unique message identifiers, optionally separated by CFWS.
+
+ The message identifier (msg-id) syntax is a limited version of the
+ addr-spec construct enclosed in the angle bracket characters, "<" and
+ ">". Unlike addr-spec, this syntax only permits the dot-atom-text
+ form on the left-hand side of the "@" and does not have internal CFWS
+ anywhere in the message identifier.
+
+ Note: As with addr-spec, a liberal syntax is given for the right-
+ hand side of the "@" in a msg-id. However, later in this section,
+ the use of a domain for the right-hand side of the "@" is
+ RECOMMENDED. Again, the syntax of domain constructs is specified
+ by and used in other protocols (e.g., [RFC1034], [RFC1035],
+ [RFC1123], [RFC5321]). It is therefore incumbent upon
+ implementations to conform to the syntax of addresses for the
+ context in which they are used.
+
+ message-id = "Message-ID:" msg-id CRLF
+
+ in-reply-to = "In-Reply-To:" 1*msg-id CRLF
+
+ references = "References:" 1*msg-id CRLF
+
+ msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
+
+ id-left = dot-atom-text / obs-id-left
+
+ id-right = dot-atom-text / no-fold-literal / obs-id-right
+
+ no-fold-literal = "[" *dtext "]"
+
+ The "Message-ID:" field provides a unique message identifier that
+ refers to a particular version of a particular message. The
+ uniqueness of the message identifier is guaranteed by the host that
+ generates it (see below). This message identifier is intended to be
+ machine readable and not necessarily meaningful to humans. A message
+ identifier pertains to exactly one version of a particular message;
+ subsequent revisions to the message each receive new message
+ identifiers.
+
+
+
+Resnick Standards Track [Page 25]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ Note: There are many instances when messages are "changed", but
+ those changes do not constitute a new instantiation of that
+ message, and therefore the message would not get a new message
+ identifier. For example, when messages are introduced into the
+ transport system, they are often prepended with additional header
+ fields such as trace fields (described in section 3.6.7) and
+ resent fields (described in section 3.6.6). The addition of such
+ header fields does not change the identity of the message and
+ therefore the original "Message-ID:" field is retained. In all
+ cases, it is the meaning that the sender of the message wishes to
+ convey (i.e., whether this is the same message or a different
+ message) that determines whether or not the "Message-ID:" field
+ changes, not any particular syntactic difference that appears (or
+ does not appear) in the message.
+
+ The "In-Reply-To:" and "References:" fields are used when creating a
+ reply to a message. They hold the message identifier of the original
+ message and the message identifiers of other messages (for example,
+ in the case of a reply to a message that was itself a reply). The
+ "In-Reply-To:" field may be used to identify the message (or
+ messages) to which the new message is a reply, while the
+ "References:" field may be used to identify a "thread" of
+ conversation.
+
+ When creating a reply to a message, the "In-Reply-To:" and
+ "References:" fields of the resultant message are constructed as
+ follows:
+
+ The "In-Reply-To:" field will contain the contents of the
+ "Message-ID:" field of the message to which this one is a reply (the
+ "parent message"). If there is more than one parent message, then
+ the "In-Reply-To:" field will contain the contents of all of the
+ parents' "Message-ID:" fields. If there is no "Message-ID:" field in
+ any of the parent messages, then the new message will have no "In-
+ Reply-To:" field.
+
+ The "References:" field will contain the contents of the parent's
+ "References:" field (if any) followed by the contents of the parent's
+ "Message-ID:" field (if any). If the parent message does not contain
+ a "References:" field but does have an "In-Reply-To:" field
+ containing a single message identifier, then the "References:" field
+ will contain the contents of the parent's "In-Reply-To:" field
+ followed by the contents of the parent's "Message-ID:" field (if
+ any). If the parent has none of the "References:", "In-Reply-To:",
+ or "Message-ID:" fields, then the new message will have no
+ "References:" field.
+
+
+
+
+
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+
+RFC 5322 Internet Message Format October 2008
+
+
+ Note: Some implementations parse the "References:" field to
+ display the "thread of the discussion". These implementations
+ assume that each new message is a reply to a single parent and
+ hence that they can walk backwards through the "References:" field
+ to find the parent of each message listed there. Therefore,
+ trying to form a "References:" field for a reply that has multiple
+ parents is discouraged; how to do so is not defined in this
+ document.
+
+ The message identifier (msg-id) itself MUST be a globally unique
+ identifier for a message. The generator of the message identifier
+ MUST guarantee that the msg-id is unique. There are several
+ algorithms that can be used to accomplish this. Since the msg-id has
+ a similar syntax to addr-spec (identical except that quoted strings,
+ comments, and folding white space are not allowed), a good method is
+ to put the domain name (or a domain literal IP address) of the host
+ on which the message identifier was created on the right-hand side of
+ the "@" (since domain names and IP addresses are normally unique),
+ and put a combination of the current absolute date and time along
+ with some other currently unique (perhaps sequential) identifier
+ available on the system (for example, a process id number) on the
+ left-hand side. Though other algorithms will work, it is RECOMMENDED
+ that the right-hand side contain some domain identifier (either of
+ the host itself or otherwise) such that the generator of the message
+ identifier can guarantee the uniqueness of the left-hand side within
+ the scope of that domain.
+
+ Semantically, the angle bracket characters are not part of the
+ msg-id; the msg-id is what is contained between the two angle bracket
+ characters.
+
+3.6.5. Informational Fields
+
+ The informational fields are all optional. The "Subject:" and
+ "Comments:" fields are unstructured fields as defined in section
+ 2.2.1, and therefore may contain text or folding white space. The
+ "Keywords:" field contains a comma-separated list of one or more
+ words or quoted-strings.
+
+ subject = "Subject:" unstructured CRLF
+
+ comments = "Comments:" unstructured CRLF
+
+ keywords = "Keywords:" phrase *("," phrase) CRLF
+
+ These three fields are intended to have only human-readable content
+ with information about the message. The "Subject:" field is the most
+ common and contains a short string identifying the topic of the
+
+
+
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+
+RFC 5322 Internet Message Format October 2008
+
+
+ message. When used in a reply, the field body MAY start with the
+ string "Re: " (an abbreviation of the Latin "in re", meaning "in the
+ matter of") followed by the contents of the "Subject:" field body of
+ the original message. If this is done, only one instance of the
+ literal string "Re: " ought to be used since use of other strings or
+ more than one instance can lead to undesirable consequences. The
+ "Comments:" field contains any additional comments on the text of the
+ body of the message. The "Keywords:" field contains a comma-
+ separated list of important words and phrases that might be useful
+ for the recipient.
+
+3.6.6. Resent Fields
+
+ Resent fields SHOULD be added to any message that is reintroduced by
+ a user into the transport system. A separate set of resent fields
+ SHOULD be added each time this is done. All of the resent fields
+ corresponding to a particular resending of the message SHOULD be
+ grouped together. Each new set of resent fields is prepended to the
+ message; that is, the most recent set of resent fields appears
+ earlier in the message. No other fields in the message are changed
+ when resent fields are added.
+
+ Each of the resent fields corresponds to a particular field elsewhere
+ in the syntax. For instance, the "Resent-Date:" field corresponds to
+ the "Date:" field and the "Resent-To:" field corresponds to the "To:"
+ field. In each case, the syntax for the field body is identical to
+ the syntax given previously for the corresponding field.
+
+ When resent fields are used, the "Resent-From:" and "Resent-Date:"
+ fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
+ "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
+ identical to "Resent-From:".
+
+ resent-date = "Resent-Date:" date-time CRLF
+
+ resent-from = "Resent-From:" mailbox-list CRLF
+
+ resent-sender = "Resent-Sender:" mailbox CRLF
+
+ resent-to = "Resent-To:" address-list CRLF
+
+ resent-cc = "Resent-Cc:" address-list CRLF
+
+ resent-bcc = "Resent-Bcc:" [address-list / CFWS] CRLF
+
+ resent-msg-id = "Resent-Message-ID:" msg-id CRLF
+
+
+
+
+
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+
+RFC 5322 Internet Message Format October 2008
+
+
+ Resent fields are used to identify a message as having been
+ reintroduced into the transport system by a user. The purpose of
+ using resent fields is to have the message appear to the final
+ recipient as if it were sent directly by the original sender, with
+ all of the original fields remaining the same. Each set of resent
+ fields correspond to a particular resending event. That is, if a
+ message is resent multiple times, each set of resent fields gives
+ identifying information for each individual time. Resent fields are
+ strictly informational. They MUST NOT be used in the normal
+ processing of replies or other such automatic actions on messages.
+
+ Note: Reintroducing a message into the transport system and using
+ resent fields is a different operation from "forwarding".
+ "Forwarding" has two meanings: One sense of forwarding is that a
+ mail reading program can be told by a user to forward a copy of a
+ message to another person, making the forwarded message the body
+ of the new message. A forwarded message in this sense does not
+ appear to have come from the original sender, but is an entirely
+ new message from the forwarder of the message. Forwarding may
+ also mean that a mail transport program gets a message and
+ forwards it on to a different destination for final delivery.
+ Resent header fields are not intended for use with either type of
+ forwarding.
+
+ The resent originator fields indicate the mailbox of the person(s) or
+ system(s) that resent the message. As with the regular originator
+ fields, there are two forms: a simple "Resent-From:" form, which
+ contains the mailbox of the individual doing the resending, and the
+ more complex form, when one individual (identified in the "Resent-
+ Sender:" field) resends a message on behalf of one or more others
+ (identified in the "Resent-From:" field).
+
+ Note: When replying to a resent message, replies behave just as
+ they would with any other message, using the original "From:",
+ "Reply-To:", "Message-ID:", and other fields. The resent fields
+ are only informational and MUST NOT be used in the normal
+ processing of replies.
+
+ The "Resent-Date:" indicates the date and time at which the resent
+ message is dispatched by the resender of the message. Like the
+ "Date:" field, it is not the date and time that the message was
+ actually transported.
+
+ The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
+ identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
+ except that they indicate the recipients of the resent message, not
+ the recipients of the original message.
+
+
+
+
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+
+RFC 5322 Internet Message Format October 2008
+
+
+ The "Resent-Message-ID:" field provides a unique identifier for the
+ resent message.
+
+3.6.7. Trace Fields
+
+ The trace fields are a group of header fields consisting of an
+ optional "Return-Path:" field, and one or more "Received:" fields.
+ The "Return-Path:" header field contains a pair of angle brackets
+ that enclose an optional addr-spec. The "Received:" field contains a
+ (possibly empty) list of tokens followed by a semicolon and a date-
+ time specification. Each token must be a word, angle-addr, addr-
+ spec, or a domain. Further restrictions are applied to the syntax of
+ the trace fields by specifications that provide for their use, such
+ as [RFC5321].
+
+ trace = [return]
+ 1*received
+
+ return = "Return-Path:" path CRLF
+
+ path = angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
+
+ received = "Received:" *received-token ";" date-time CRLF
+
+ received-token = word / angle-addr / addr-spec / domain
+
+ A full discussion of the Internet mail use of trace fields is
+ contained in [RFC5321]. For the purposes of this specification, the
+ trace fields are strictly informational, and any formal
+ interpretation of them is outside of the scope of this document.
+
+3.6.8. Optional Fields
+
+ Fields may appear in messages that are otherwise unspecified in this
+ document. They MUST conform to the syntax of an optional-field.
+ This is a field name, made up of the printable US-ASCII characters
+ except SP and colon, followed by a colon, followed by any text that
+ conforms to the unstructured syntax.
+
+ The field names of any optional field MUST NOT be identical to any
+ field name specified elsewhere in this document.
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 30]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ optional-field = field-name ":" unstructured CRLF
+
+ field-name = 1*ftext
+
+ ftext = %d33-57 / ; Printable US-ASCII
+ %d59-126 ; characters not including
+ ; ":".
+
+ For the purposes of this specification, any optional field is
+ uninterpreted.
+
+4. Obsolete Syntax
+
+ Earlier versions of this specification allowed for different (usually
+ more liberal) syntax than is allowed in this version. Also, there
+ have been syntactic elements used in messages on the Internet whose
+ interpretations have never been documented. Though these syntactic
+ forms MUST NOT be generated according to the grammar in section 3,
+ they MUST be accepted and parsed by a conformant receiver. This
+ section documents many of these syntactic elements. Taking the
+ grammar in section 3 and adding the definitions presented in this
+ section will result in the grammar to use for the interpretation of
+ messages.
+
+ Note: This section identifies syntactic forms that any
+ implementation MUST reasonably interpret. However, there are
+ certainly Internet messages that do not conform to even the
+ additional syntax given in this section. The fact that a
+ particular form does not appear in any section of this document is
+ not justification for computer programs to crash or for malformed
+ data to be irretrievably lost by any implementation. It is up to
+ the implementation to deal with messages robustly.
+
+ One important difference between the obsolete (interpreting) and the
+ current (generating) syntax is that in structured header field bodies
+ (i.e., between the colon and the CRLF of any structured header
+ field), white space characters, including folding white space, and
+ comments could be freely inserted between any syntactic tokens. This
+ allowed many complex forms that have proven difficult for some
+ implementations to parse.
+
+ Another key difference between the obsolete and the current syntax is
+ that the rule in section 3.2.2 regarding lines composed entirely of
+ white space in comments and folding white space does not apply. See
+ the discussion of folding white space in section 4.2 below.
+
+ Finally, certain characters that were formerly allowed in messages
+ appear in this section. The NUL character (ASCII value 0) was once
+
+
+
+Resnick Standards Track [Page 31]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ allowed, but is no longer for compatibility reasons. Similarly, US-
+ ASCII control characters other than CR, LF, SP, and HTAB (ASCII
+ values 1 through 8, 11, 12, 14 through 31, and 127) were allowed to
+ appear in header field bodies. CR and LF were allowed to appear in
+ messages other than as CRLF; this use is also shown here.
+
+ Other differences in syntax and semantics are noted in the following
+ sections.
+
+4.1. Miscellaneous Obsolete Tokens
+
+ These syntactic elements are used elsewhere in the obsolete syntax or
+ in the main syntax. Bare CR, bare LF, and NUL are added to obs-qp,
+ obs-body, and obs-unstruct. US-ASCII control characters are added to
+ obs-qp, obs-unstruct, obs-ctext, and obs-qtext. The period character
+ is added to obs-phrase. The obs-phrase-list provides for a
+ (potentially empty) comma-separated list of phrases that may include
+ "null" elements. That is, there could be two or more commas in such
+ a list with nothing in between them, or commas at the beginning or
+ end of the list.
+
+ Note: The "period" (or "full stop") character (".") in obs-phrase
+ is not a form that was allowed in earlier versions of this or any
+ other specification. Period (nor any other character from
+ specials) was not allowed in phrase because it introduced a
+ parsing difficulty distinguishing between phrases and portions of
+ an addr-spec (see section 4.4). It appears here because the
+ period character is currently used in many messages in the
+ display-name portion of addresses, especially for initials in
+ names, and therefore must be interpreted properly.
+
+ obs-NO-WS-CTL = %d1-8 / ; US-ASCII control
+ %d11 / ; characters that do not
+ %d12 / ; include the carriage
+ %d14-31 / ; return, line feed, and
+ %d127 ; white space characters
+
+ obs-ctext = obs-NO-WS-CTL
+
+ obs-qtext = obs-NO-WS-CTL
+
+ obs-utext = %d0 / obs-NO-WS-CTL / VCHAR
+
+ obs-qp = "\" (%d0 / obs-NO-WS-CTL / LF / CR)
+
+ obs-body = *((*LF *CR *((%d0 / text) *LF *CR)) / CRLF)
+
+ obs-unstruct = *((*LF *CR *(obs-utext *LF *CR)) / FWS)
+
+
+
+Resnick Standards Track [Page 32]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ obs-phrase = word *(word / "." / CFWS)
+
+ obs-phrase-list = [phrase / CFWS] *("," [phrase / CFWS])
+
+ Bare CR and bare LF appear in messages with two different meanings.
+ In many cases, bare CR or bare LF are used improperly instead of CRLF
+ to indicate line separators. In other cases, bare CR and bare LF are
+ used simply as US-ASCII control characters with their traditional
+ ASCII meanings.
+
+4.2. Obsolete Folding White Space
+
+ In the obsolete syntax, any amount of folding white space MAY be
+ inserted where the obs-FWS rule is allowed. This creates the
+ possibility of having two consecutive "folds" in a line, and
+ therefore the possibility that a line which makes up a folded header
+ field could be composed entirely of white space.
+
+ obs-FWS = 1*WSP *(CRLF 1*WSP)
+
+4.3. Obsolete Date and Time
+
+ The syntax for the obsolete date format allows a 2 digit year in the
+ date field and allows for a list of alphabetic time zone specifiers
+ that were used in earlier versions of this specification. It also
+ permits comments and folding white space between many of the tokens.
+
+ obs-day-of-week = [CFWS] day-name [CFWS]
+
+ obs-day = [CFWS] 1*2DIGIT [CFWS]
+
+ obs-year = [CFWS] 2*DIGIT [CFWS]
+
+ obs-hour = [CFWS] 2DIGIT [CFWS]
+
+ obs-minute = [CFWS] 2DIGIT [CFWS]
+
+ obs-second = [CFWS] 2DIGIT [CFWS]
+
+ obs-zone = "UT" / "GMT" / ; Universal Time
+ ; North American UT
+ ; offsets
+ "EST" / "EDT" / ; Eastern: - 5/ - 4
+ "CST" / "CDT" / ; Central: - 6/ - 5
+ "MST" / "MDT" / ; Mountain: - 7/ - 6
+ "PST" / "PDT" / ; Pacific: - 8/ - 7
+ ;
+
+
+
+
+Resnick Standards Track [Page 33]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ %d65-73 / ; Military zones - "A"
+ %d75-90 / ; through "I" and "K"
+ %d97-105 / ; through "Z", both
+ %d107-122 ; upper and lower case
+
+ Where a two or three digit year occurs in a date, the year is to be
+ interpreted as follows: If a two digit year is encountered whose
+ value is between 00 and 49, the year is interpreted by adding 2000,
+ ending up with a value between 2000 and 2049. If a two digit year is
+ encountered with a value between 50 and 99, or any three digit year
+ is encountered, the year is interpreted by adding 1900.
+
+ In the obsolete time zone, "UT" and "GMT" are indications of
+ "Universal Time" and "Greenwich Mean Time", respectively, and are
+ both semantically identical to "+0000".
+
+ The remaining three character zones are the US time zones. The first
+ letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
+ "Mountain", and "Pacific". The second letter is either "S" for
+ "Standard" time, or "D" for "Daylight Savings" (or summer) time.
+ Their interpretations are as follows:
+
+ EDT is semantically equivalent to -0400
+ EST is semantically equivalent to -0500
+ CDT is semantically equivalent to -0500
+ CST is semantically equivalent to -0600
+ MDT is semantically equivalent to -0600
+ MST is semantically equivalent to -0700
+ PDT is semantically equivalent to -0700
+ PST is semantically equivalent to -0800
+
+ The 1 character military time zones were defined in a non-standard
+ way in [RFC0822] and are therefore unpredictable in their meaning.
+ The original definitions of the military zones "A" through "I" are
+ equivalent to "+0100" through "+0900", respectively; "K", "L", and
+ "M" are equivalent to "+1000", "+1100", and "+1200", respectively;
+ "N" through "Y" are equivalent to "-0100" through "-1200".
+ respectively; and "Z" is equivalent to "+0000". However, because of
+ the error in [RFC0822], they SHOULD all be considered equivalent to
+ "-0000" unless there is out-of-band information confirming their
+ meaning.
+
+ Other multi-character (usually between 3 and 5) alphabetic time zones
+ have been used in Internet messages. Any such time zone whose
+ meaning is not known SHOULD be considered equivalent to "-0000"
+ unless there is out-of-band information confirming their meaning.
+
+
+
+
+
+Resnick Standards Track [Page 34]
+
+RFC 5322 Internet Message Format October 2008
+
+
+4.4. Obsolete Addressing
+
+ There are four primary differences in addressing. First, mailbox
+ addresses were allowed to have a route portion before the addr-spec
+ when enclosed in "<" and ">". The route is simply a comma-separated
+ list of domain names, each preceded by "@", and the list terminated
+ by a colon. Second, CFWS were allowed between the period-separated
+ elements of local-part and domain (i.e., dot-atom was not used). In
+ addition, local-part is allowed to contain quoted-string in addition
+ to just atom. Third, mailbox-list and address-list were allowed to
+ have "null" members. That is, there could be two or more commas in
+ such a list with nothing in between them, or commas at the beginning
+ or end of the list. Finally, US-ASCII control characters and quoted-
+ pairs were allowed in domain literals and are added here.
+
+ obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
+
+ obs-route = obs-domain-list ":"
+
+ obs-domain-list = *(CFWS / ",") "@" domain
+ *("," [CFWS] ["@" domain])
+
+ obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
+
+ obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
+
+ obs-group-list = 1*([CFWS] ",") [CFWS]
+
+ obs-local-part = word *("." word)
+
+ obs-domain = atom *("." atom)
+
+ obs-dtext = obs-NO-WS-CTL / quoted-pair
+
+ When interpreting addresses, the route portion SHOULD be ignored.
+
+4.5. Obsolete Header Fields
+
+ Syntactically, the primary difference in the obsolete field syntax is
+ that it allows multiple occurrences of any of the fields and they may
+ occur in any order. Also, any amount of white space is allowed
+ before the ":" at the end of the field name.
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 35]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ obs-fields = *(obs-return /
+ obs-received /
+ obs-orig-date /
+ obs-from /
+ obs-sender /
+ obs-reply-to /
+ obs-to /
+ obs-cc /
+ obs-bcc /
+ obs-message-id /
+ obs-in-reply-to /
+ obs-references /
+ obs-subject /
+ obs-comments /
+ obs-keywords /
+ obs-resent-date /
+ obs-resent-from /
+ obs-resent-send /
+ obs-resent-rply /
+ obs-resent-to /
+ obs-resent-cc /
+ obs-resent-bcc /
+ obs-resent-mid /
+ obs-optional)
+
+ Except for destination address fields (described in section 4.5.3),
+ the interpretation of multiple occurrences of fields is unspecified.
+ Also, the interpretation of trace fields and resent fields that do
+ not occur in blocks prepended to the message is unspecified as well.
+ Unless otherwise noted in the following sections, interpretation of
+ other fields is identical to the interpretation of their non-obsolete
+ counterparts in section 3.
+
+4.5.1. Obsolete Origination Date Field
+
+ obs-orig-date = "Date" *WSP ":" date-time CRLF
+
+4.5.2. Obsolete Originator Fields
+
+ obs-from = "From" *WSP ":" mailbox-list CRLF
+
+ obs-sender = "Sender" *WSP ":" mailbox CRLF
+
+ obs-reply-to = "Reply-To" *WSP ":" address-list CRLF
+
+
+
+
+
+
+
+Resnick Standards Track [Page 36]
+
+RFC 5322 Internet Message Format October 2008
+
+
+4.5.3. Obsolete Destination Address Fields
+
+ obs-to = "To" *WSP ":" address-list CRLF
+
+ obs-cc = "Cc" *WSP ":" address-list CRLF
+
+ obs-bcc = "Bcc" *WSP ":"
+ (address-list / (*([CFWS] ",") [CFWS])) CRLF
+
+ When multiple occurrences of destination address fields occur in a
+ message, they SHOULD be treated as if the address list in the first
+ occurrence of the field is combined with the address lists of the
+ subsequent occurrences by adding a comma and concatenating.
+
+4.5.4. Obsolete Identification Fields
+
+ The obsolete "In-Reply-To:" and "References:" fields differ from the
+ current syntax in that they allow phrase (words or quoted strings) to
+ appear. The obsolete forms of the left and right sides of msg-id
+ allow interspersed CFWS, making them syntactically identical to
+ local-part and domain, respectively.
+
+ obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
+
+ obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
+
+ obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
+
+ obs-id-left = local-part
+
+ obs-id-right = domain
+
+ For purposes of interpretation, the phrases in the "In-Reply-To:" and
+ "References:" fields are ignored.
+
+ Semantically, none of the optional CFWS in the local-part and the
+ domain is part of the obs-id-left and obs-id-right, respectively.
+
+4.5.5. Obsolete Informational Fields
+
+ obs-subject = "Subject" *WSP ":" unstructured CRLF
+
+ obs-comments = "Comments" *WSP ":" unstructured CRLF
+
+ obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
+
+
+
+
+
+
+Resnick Standards Track [Page 37]
+
+RFC 5322 Internet Message Format October 2008
+
+
+4.5.6. Obsolete Resent Fields
+
+ The obsolete syntax adds a "Resent-Reply-To:" field, which consists
+ of the field name, the optional comments and folding white space, the
+ colon, and a comma separated list of addresses.
+
+ obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
+
+ obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
+
+ obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
+
+ obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
+
+ obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
+
+ obs-resent-bcc = "Resent-Bcc" *WSP ":"
+ (address-list / (*([CFWS] ",") [CFWS])) CRLF
+
+ obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
+
+ obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
+
+ As with other resent fields, the "Resent-Reply-To:" field is to be
+ treated as trace information only.
+
+4.5.7. Obsolete Trace Fields
+
+ The obs-return and obs-received are again given here as template
+ definitions, just as return and received are in section 3. Their
+ full syntax is given in [RFC5321].
+
+ obs-return = "Return-Path" *WSP ":" path CRLF
+
+ obs-received = "Received" *WSP ":" *received-token CRLF
+
+4.5.8. Obsolete optional fields
+
+ obs-optional = field-name *WSP ":" unstructured CRLF
+
+5. Security Considerations
+
+ Care needs to be taken when displaying messages on a terminal or
+ terminal emulator. Powerful terminals may act on escape sequences
+ and other combinations of US-ASCII control characters with a variety
+ of consequences. They can remap the keyboard or permit other
+ modifications to the terminal that could lead to denial of service or
+ even damaged data. They can trigger (sometimes programmable)
+
+
+
+Resnick Standards Track [Page 38]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ answerback messages that can allow a message to cause commands to be
+ issued on the recipient's behalf. They can also affect the operation
+ of terminal attached devices such as printers. Message viewers may
+ wish to strip potentially dangerous terminal escape sequences from
+ the message prior to display. However, other escape sequences appear
+ in messages for useful purposes (cf. [ISO.2022.1994], [RFC2045],
+ [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]) and therefore
+ should not be stripped indiscriminately.
+
+ Transmission of non-text objects in messages raises additional
+ security issues. These issues are discussed in [RFC2045], [RFC2046],
+ [RFC2047], [RFC2049], [RFC4288], and [RFC4289].
+
+ Many implementations use the "Bcc:" (blind carbon copy) field,
+ described in section 3.6.3, to facilitate sending messages to
+ recipients without revealing the addresses of one or more of the
+ addressees to the other recipients. Mishandling this use of "Bcc:"
+ may disclose confidential information that could eventually lead to
+ security problems through knowledge of even the existence of a
+ particular mail address. For example, if using the first method
+ described in section 3.6.3, where the "Bcc:" line is removed from the
+ message, blind recipients have no explicit indication that they have
+ been sent a blind copy, except insofar as their address does not
+ appear in the header section of a message. Because of this, one of
+ the blind addressees could potentially send a reply to all of the
+ shown recipients and accidentally reveal that the message went to the
+ blind recipient. When the second method from section 3.6.3 is used,
+ the blind recipient's address appears in the "Bcc:" field of a
+ separate copy of the message. If the "Bcc:" field sent contains all
+ of the blind addressees, all of the "Bcc:" recipients will be seen by
+ each "Bcc:" recipient. Even if a separate message is sent to each
+ "Bcc:" recipient with only the individual's address, implementations
+ still need to be careful to process replies to the message as per
+ section 3.6.3 so as not to accidentally reveal the blind recipient to
+ other recipients.
+
+6. IANA Considerations
+
+ This document updates the registrations that appeared in [RFC4021]
+ that referred to the definitions in [RFC2822]. IANA has updated the
+ Permanent Message Header Field Repository with the following header
+ fields, in accordance with the procedures set out in [RFC3864].
+
+ Header field name: Date
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.1)
+
+
+
+Resnick Standards Track [Page 39]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ Header field name: From
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.2)
+
+ Header field name: Sender
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.2)
+
+ Header field name: Reply-To
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.2)
+
+ Header field name: To
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.3)
+
+ Header field name: Cc
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.3)
+
+ Header field name: Bcc
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.3)
+
+ Header field name: Message-ID
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.4)
+
+ Header field name: In-Reply-To
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.4)
+
+
+
+
+Resnick Standards Track [Page 40]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ Header field name: References
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.4)
+
+ Header field name: Subject
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.5)
+
+ Header field name: Comments
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.5)
+
+ Header field name: Keywords
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.5)
+
+ Header field name: Resent-Date
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Resent-From
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Resent-Sender
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Resent-To
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+
+
+
+Resnick Standards Track [Page 41]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ Header field name: Resent-Cc
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Resent-Bcc
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Resent-Reply-To
+ Applicable protocol: Mail
+ Status: obsolete
+ Author/Change controller: IETF
+ Specification document(s): This document (section 4.5.6)
+
+ Header field name: Resent-Message-ID
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.6)
+
+ Header field name: Return-Path
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.7)
+
+ Header field name: Received
+ Applicable protocol: Mail
+ Status: standard
+ Author/Change controller: IETF
+ Specification document(s): This document (section 3.6.7)
+ Related information: [RFC5321]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 42]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A. Example Messages
+
+ This section presents a selection of messages. These are intended to
+ assist in the implementation of this specification, but should not be
+ taken as normative; that is to say, although the examples in this
+ section were carefully reviewed, if there happens to be a conflict
+ between these examples and the syntax described in sections 3 and 4
+ of this document, the syntax in those sections is to be taken as
+ correct.
+
+ In the text version of this document, messages in this section are
+ delimited between lines of "----". The "----" lines are not part of
+ the message itself.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 43]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.1. Addressing Examples
+
+ The following are examples of messages that might be sent between two
+ individuals.
+
+Appendix A.1.1. A Message from One Person to Another with Simple
+ Addressing
+
+ This could be called a canonical message. It has a single author,
+ John Doe, a single recipient, Mary Smith, a subject, the date, a
+ message identifier, and a textual message in the body.
+
+ ----
+ From: John Doe <jdoe@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+ If John's secretary Michael actually sent the message, even though
+ John was the author and replies to this message should go back to
+ him, the sender field would be used:
+
+ ----
+ From: John Doe <jdoe@machine.example>
+ Sender: Michael Jones <mjones@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 44]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.1.2. Different Types of Mailboxes
+
+ This message includes multiple addresses in the destination fields
+ and also uses several different forms of addresses.
+
+ ----
+ From: "Joe Q. Public" <john.q.public@example.com>
+ To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
+ Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
+ Date: Tue, 1 Jul 2003 10:52:37 +0200
+ Message-ID: <5678.21-Nov-1997@example.com>
+
+ Hi everyone.
+ ----
+
+ Note that the display names for Joe Q. Public and Giant; "Big" Box
+ needed to be enclosed in double-quotes because the former contains
+ the period and the latter contains both semicolon and double-quote
+ characters (the double-quote characters appearing as quoted-pair
+ constructs). Conversely, the display name for Who? could appear
+ without them because the question mark is legal in an atom. Notice
+ also that jdoe@example.org and boss@nil.test have no display names
+ associated with them at all, and jdoe@example.org uses the simpler
+ address form without the angle brackets.
+
+Appendix A.1.3. Group Addresses
+
+ ----
+ From: Pete <pete@silly.example>
+ To: A Group:Ed Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
+ Cc: Undisclosed recipients:;
+ Date: Thu, 13 Feb 1969 23:32:54 -0330
+ Message-ID: <testabcd.1234@silly.example>
+
+ Testing.
+ ----
+
+ In this message, the "To:" field has a single group recipient named
+ "A Group", which contains 3 addresses, and a "Cc:" field with an
+ empty group recipient named Undisclosed recipients.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 45]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.2. Reply Messages
+
+ The following is a series of three messages that make up a
+ conversation thread between John and Mary. John first sends a
+ message to Mary, Mary then replies to John's message, and then John
+ replies to Mary's reply message.
+
+ Note especially the "Message-ID:", "References:", and "In-Reply-To:"
+ fields in each message.
+
+ ----
+ From: John Doe <jdoe@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+ When sending replies, the Subject field is often retained, though
+ prepended with "Re: " as described in section 3.6.5.
+
+ ----
+ From: Mary Smith <mary@example.net>
+ To: John Doe <jdoe@machine.example>
+ Reply-To: "Mary Smith: Personal Account" <smith@home.example>
+ Subject: Re: Saying Hello
+ Date: Fri, 21 Nov 1997 10:01:10 -0600
+ Message-ID: <3456@example.net>
+ In-Reply-To: <1234@local.machine.example>
+ References: <1234@local.machine.example>
+
+ This is a reply to your hello.
+ ----
+
+ Note the "Reply-To:" field in the above message. When John replies
+ to Mary's message above, the reply should go to the address in the
+ "Reply-To:" field instead of the address in the "From:" field.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 46]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ ----
+ To: "Mary Smith: Personal Account" <smith@home.example>
+ From: John Doe <jdoe@machine.example>
+ Subject: Re: Saying Hello
+ Date: Fri, 21 Nov 1997 11:00:00 -0600
+ Message-ID: <abcd.1234@local.machine.test>
+ In-Reply-To: <3456@example.net>
+ References: <1234@local.machine.example> <3456@example.net>
+
+ This is a reply to your reply.
+ ----
+
+Appendix A.3. Resent Messages
+
+ Start with the message that has been used as an example several
+ times:
+
+ ----
+ From: John Doe <jdoe@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+ Say that Mary, upon receiving this message, wishes to send a copy of
+ the message to Jane such that (a) the message would appear to have
+ come straight from John; (b) if Jane replies to the message, the
+ reply should go back to John; and (c) all of the original
+ information, like the date the message was originally sent to Mary,
+ the message identifier, and the original addressee, is preserved. In
+ this case, resent fields are prepended to the message:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 47]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ ----
+ Resent-From: Mary Smith <mary@example.net>
+ Resent-To: Jane Brown <j-brown@other.example>
+ Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
+ Resent-Message-ID: <78910@example.net>
+ From: John Doe <jdoe@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+ If Jane, in turn, wished to resend this message to another person,
+ she would prepend her own set of resent header fields to the above
+ and send that. (Note that for brevity, trace fields are not shown.)
+
+Appendix A.4. Messages with Trace Fields
+
+ As messages are sent through the transport system as described in
+ [RFC5321], trace fields are prepended to the message. The following
+ is an example of what those trace fields might look like. Note that
+ there is some folding white space in the first one since these lines
+ can be long.
+
+ ----
+ Received: from x.y.test
+ by example.net
+ via TCP
+ with ESMTP
+ id ABC12345
+ for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
+ Received: from node.example by x.y.test; 21 Nov 1997 10:01:22 -0600
+ From: John Doe <jdoe@node.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: Fri, 21 Nov 1997 09:55:06 -0600
+ Message-ID: <1234@local.node.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+
+
+
+
+
+
+Resnick Standards Track [Page 48]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.5. White Space, Comments, and Other Oddities
+
+ White space, including folding white space, and comments can be
+ inserted between many of the tokens of fields. Taking the example
+ from A.1.3, white space and comments can be inserted into all of the
+ fields.
+
+ ----
+ From: Pete(A nice \) chap) <pete(his account)@silly.test(his host)>
+ To:A Group(Some people)
+ :Chris Jones <c@(Chris's host.)public.example>,
+ joe@example.org,
+ John <jdoe@one.test> (my dear friend); (the end of the group)
+ Cc:(Empty list)(start)Hidden recipients :(nobody(that I know)) ;
+ Date: Thu,
+ 13
+ Feb
+ 1969
+ 23:32
+ -0330 (Newfoundland Time)
+ Message-ID: <testabcd.1234@silly.test>
+
+ Testing.
+ ----
+
+ The above example is aesthetically displeasing, but perfectly legal.
+ Note particularly (1) the comments in the "From:" field (including
+ one that has a ")" character appearing as part of a quoted-pair); (2)
+ the white space absent after the ":" in the "To:" field as well as
+ the comment and folding white space after the group name, the special
+ character (".") in the comment in Chris Jones's address, and the
+ folding white space before and after "joe@example.org,"; (3) the
+ multiple and nested comments in the "Cc:" field as well as the
+ comment immediately following the ":" after "Cc"; (4) the folding
+ white space (but no comments except at the end) and the missing
+ seconds in the time of the date field; and (5) the white space before
+ (but not within) the identifier in the "Message-ID:" field.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 49]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.6. Obsoleted Forms
+
+ The following are examples of obsolete (that is, the "MUST NOT
+ generate") syntactic elements described in section 4 of this
+ document.
+
+Appendix A.6.1. Obsolete Addressing
+
+ Note in the example below the lack of quotes around Joe Q. Public,
+ the route that appears in the address for Mary Smith, the two commas
+ that appear in the "To:" field, and the spaces that appear around the
+ "." in the jdoe address.
+
+ ----
+ From: Joe Q. Public <john.q.public@example.com>
+ To: Mary Smith <@node.test:mary@example.net>, , jdoe@test . example
+ Date: Tue, 1 Jul 2003 10:52:37 +0200
+ Message-ID: <5678.21-Nov-1997@example.com>
+
+ Hi everyone.
+ ----
+
+Appendix A.6.2. Obsolete Dates
+
+ The following message uses an obsolete date format, including a non-
+ numeric time zone and a two digit year. Note that although the day-
+ of-week is missing, that is not specific to the obsolete syntax; it
+ is optional in the current syntax as well.
+
+ ----
+ From: John Doe <jdoe@machine.example>
+ To: Mary Smith <mary@example.net>
+ Subject: Saying Hello
+ Date: 21 Nov 97 09:55:06 GMT
+ Message-ID: <1234@local.machine.example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 50]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix A.6.3. Obsolete White Space and Comments
+
+ White space and comments can appear between many more elements than
+ in the current syntax. Also, folding lines that are made up entirely
+ of white space are legal.
+
+ ----
+ From : John Doe <jdoe@machine(comment). example>
+ To : Mary Smith
+ __
+ <mary@example.net>
+ Subject : Saying Hello
+ Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
+ Message-ID : <1234 @ local(blah) .machine .example>
+
+ This is a message just to say hello.
+ So, "Hello".
+ ----
+
+ Note especially the second line of the "To:" field. It starts with
+ two space characters. (Note that "__" represent blank spaces.)
+ Therefore, it is considered part of the folding, as described in
+ section 4.2. Also, the comments and white space throughout
+ addresses, dates, and message identifiers are all part of the
+ obsolete syntax.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 51]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Appendix B. Differences from Earlier Specifications
+
+ This appendix contains a list of changes that have been made in the
+ Internet Message Format from earlier specifications, specifically
+ [RFC0822], [RFC1123], and [RFC2822]. Items marked with an asterisk
+ (*) below are items which appear in section 4 of this document and
+ therefore can no longer be generated.
+
+ The following are the changes made from [RFC0822] and [RFC1123] to
+ [RFC2822] that remain in this document:
+
+ 1. Period allowed in obsolete form of phrase.
+ 2. ABNF moved out of document, now in [RFC5234].
+ 3. Four or more digits allowed for year.
+ 4. Header field ordering (and lack thereof) made explicit.
+ 5. Encrypted header field removed.
+ 6. Specifically allow and give meaning to "-0000" time zone.
+ 7. Folding white space is not allowed between every token.
+ 8. Requirement for destinations removed.
+ 9. Forwarding and resending redefined.
+ 10. Extension header fields no longer specifically called out.
+ 11. ASCII 0 (null) removed.*
+ 12. Folding continuation lines cannot contain only white space.*
+ 13. Free insertion of comments not allowed in date.*
+ 14. Non-numeric time zones not allowed.*
+ 15. Two digit years not allowed.*
+ 16. Three digit years interpreted, but not allowed for generation.*
+ 17. Routes in addresses not allowed.*
+ 18. CFWS within local-parts and domains not allowed.*
+ 19. Empty members of address lists not allowed.*
+ 20. Folding white space between field name and colon not allowed.*
+ 21. Comments between field name and colon not allowed.
+ 22. Tightened syntax of in-reply-to and references.*
+ 23. CFWS within msg-id not allowed.*
+ 24. Tightened semantics of resent fields as informational only.
+ 25. Resent-Reply-To not allowed.*
+ 26. No multiple occurrences of fields (except resent and received).*
+ 27. Free CR and LF not allowed.*
+ 28. Line length limits specified.
+ 29. Bcc more clearly specified.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 52]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ The following are changes from [RFC2822].
+ 1. Assorted typographical/grammatical errors fixed and
+ clarifications made.
+ 2. Changed "standard" to "document" or "specification" throughout.
+ 3. Made distinction between "header field" and "header section".
+ 4. Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
+ 5. Moved discussion of specials to the "Atom" section. Moved text
+ to "Overall message syntax" section.
+ 6. Simplified CFWS syntax.
+ 7. Fixed unstructured syntax.
+ 8. Changed date and time syntax to deal with white space in
+ obsolete date syntax.
+ 9. Removed quoted-pair from domain literals and message
+ identifiers.*
+ 10. Clarified that other specifications limit domain syntax.
+ 11. Simplified "Bcc:" and "Resent-Bcc:" syntax.
+ 12. Allowed optional-field to appear within trace information.
+ 13. Removed no-fold-quote from msg-id. Clarified syntax
+ limitations.
+ 14. Generalized "Received:" syntax to fix bugs and move definition
+ out of this document.
+ 15. Simplified obs-qp. Fixed and simplified obs-utext (which now
+ only appears in the obsolete syntax). Removed obs-text and obs-
+ char, adding obs-body.
+ 16. Fixed obsolete date syntax to allow for more (or less) comments
+ and white space.
+ 17. Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list,
+ obs-addr-list, obs-phrase-list, and the newly added obs-group-
+ list).
+ 18. Fixed obs-reply-to syntax.
+ 19. Fixed obs-bcc and obs-resent-bcc to allow empty lists.
+ 20. Removed obs-path.
+
+Appendix C. Acknowledgements
+
+ Many people contributed to this document. They included folks who
+ participated in the Detailed Revision and Update of Messaging
+ Standards (DRUMS) Working Group of the Internet Engineering Task
+ Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
+ people who simply sent their comments in via email. The editor is
+ deeply indebted to them all and thanks them sincerely. The below
+ list includes everyone who sent email concerning both this document
+ and [RFC2822]. Hopefully, everyone who contributed is named here:
+
+ +--------------------+----------------------+---------------------+
+ | Matti Aarnio | Tanaka Akira | Russ Allbery |
+ | Eric Allman | Harald Alvestrand | Ran Atkinson |
+ | Jos Backus | Bruce Balden | Dave Barr |
+
+
+
+Resnick Standards Track [Page 53]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ | Alan Barrett | John Beck | J Robert von Behren |
+ | Jos den Bekker | D J Bernstein | James Berriman |
+ | Oliver Block | Norbert Bollow | Raj Bose |
+ | Antony Bowesman | Scott Bradner | Randy Bush |
+ | Tom Byrer | Bruce Campbell | Larry Campbell |
+ | W J Carpenter | Michael Chapman | Richard Clayton |
+ | Maurizio Codogno | Jim Conklin | R Kelley Cook |
+ | Nathan Coulter | Steve Coya | Mark Crispin |
+ | Dave Crocker | Matt Curtin | Michael D'Errico |
+ | Cyrus Daboo | Michael D Dean | Jutta Degener |
+ | Mark Delany | Steve Dorner | Harold A Driscoll |
+ | Michael Elkins | Frank Ellerman | Robert Elz |
+ | Johnny Eriksson | Erik E Fair | Roger Fajman |
+ | Patrik Faltstrom | Claus Andre Faerber | Barry Finkel |
+ | Erik Forsberg | Chuck Foster | Paul Fox |
+ | Klaus M Frank | Ned Freed | Jochen Friedrich |
+ | Randall C Gellens | Sukvinder Singh Gill | Tim Goodwin |
+ | Philip Guenther | Arnt Gulbrandsen | Eric A Hall |
+ | Tony Hansen | John Hawkinson | Philip Hazel |
+ | Kai Henningsen | Robert Herriot | Paul Hethmon |
+ | Jim Hill | Alfred Hoenes | Paul E Hoffman |
+ | Steve Hole | Kari Hurtta | Marco S Hyman |
+ | Ofer Inbar | Olle Jarnefors | Kevin Johnson |
+ | Sudish Joseph | Maynard Kang | Prabhat Keni |
+ | John C Klensin | Graham Klyne | Brad Knowles |
+ | Shuhei Kobayashi | Peter Koch | Dan Kohn |
+ | Christian Kuhtz | Anand Kumria | Steen Larsen |
+ | Eliot Lear | Barry Leiba | Jay Levitt |
+ | Bruce Lilly | Lars-Johan Liman | Charles Lindsey |
+ | Pete Loshin | Simon Lyall | Bill Manning |
+ | John Martin | Mark Martinec | Larry Masinter |
+ | Denis McKeon | William P McQuillan | Alexey Melnikov |
+ | Perry E Metzger | Steven Miller | S Moonesamy |
+ | Keith Moore | John Gardiner Myers | Chris Newman |
+ | John W Noerenberg | Eric Norman | Mike O'Dell |
+ | Larry Osterman | Paul Overell | Jacob Palme |
+ | Michael A Patton | Uzi Paz | Michael A Quinlan |
+ | Robert Rapplean | Eric S Raymond | Sam Roberts |
+ | Hugh Sasse | Bart Schaefer | Tom Scola |
+ | Wolfgang Segmuller | Nick Shelness | John Stanley |
+ | Einar Stefferud | Jeff Stephenson | Bernard Stern |
+ | Peter Sylvester | Mark Symons | Eric Thomas |
+ | Lee Thompson | Karel De Vriendt | Matthew Wall |
+ | Rolf Weber | Brent B Welch | Dan Wing |
+ | Jack De Winter | Gregory J Woodhouse | Greg A Woods |
+ | Kazu Yamamoto | Alain Zahm | Jamie Zawinski |
+ | Timothy S Zurcher | | |
+ +--------------------+----------------------+---------------------+
+
+
+
+Resnick Standards Track [Page 54]
+
+RFC 5322 Internet Message Format October 2008
+
+
+7. References
+
+7.1. Normative References
+
+ [ANSI.X3-4.1986] American National Standards Institute, "Coded
+ Character Set - 7-bit American Standard Code for
+ Information Interchange", ANSI X3.4, 1986.
+
+ [RFC1034] Mockapetris, P., "Domain names - concepts and
+ facilities", STD 13, RFC 1034, November 1987.
+
+ [RFC1035] Mockapetris, P., "Domain names - implementation and
+ specification", STD 13, RFC 1035, November 1987.
+
+ [RFC1123] Braden, R., "Requirements for Internet Hosts -
+ Application and Support", STD 3, RFC 1123,
+ October 1989.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", STD 68, RFC 5234,
+ January 2008.
+
+7.2. Informative References
+
+ [RFC0822] Crocker, D., "Standard for the format of ARPA
+ Internet text messages", STD 11, RFC 822,
+ August 1982.
+
+ [RFC1305] Mills, D., "Network Time Protocol (Version 3)
+ Specification, Implementation", RFC 1305,
+ March 1992.
+
+ [ISO.2022.1994] International Organization for Standardization,
+ "Information technology - Character code structure
+ and extension techniques", ISO Standard 2022, 1994.
+
+ [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) Part One: Format of Internet
+ Message Bodies", RFC 2045, November 1996.
+
+ [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) Part Two: Media Types",
+ RFC 2046, November 1996.
+
+
+
+
+
+Resnick Standards Track [Page 55]
+
+RFC 5322 Internet Message Format October 2008
+
+
+ [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
+ Extensions) Part Three: Message Header Extensions
+ for Non-ASCII Text", RFC 2047, November 1996.
+
+ [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) Part Five: Conformance
+ Criteria and Examples", RFC 2049, November 1996.
+
+ [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
+ April 2001.
+
+ [RFC3864] Klyne, G., Nottingham, M., and J. Mogul,
+ "Registration Procedures for Message Header
+ Fields", BCP 90, RFC 3864, September 2004.
+
+ [RFC4021] Klyne, G. and J. Palme, "Registration of Mail and
+ MIME Header Fields", RFC 4021, March 2005.
+
+ [RFC4288] Freed, N. and J. Klensin, "Media Type
+ Specifications and Registration Procedures",
+ BCP 13, RFC 4288, December 2005.
+
+ [RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet
+ Mail Extensions (MIME) Part Four: Registration
+ Procedures", BCP 13, RFC 4289, December 2005.
+
+ [RFC5321] Klensin, J., "Simple Mail Transfer Protocol",
+ RFC 5321, October 2008.
+
+Author's Address
+
+ Peter W. Resnick (editor)
+ Qualcomm Incorporated
+ 5775 Morehouse Drive
+ San Diego, CA 92121-1714
+ US
+
+ Phone: +1 858 651 4478
+ EMail: presnick@qualcomm.com
+ URI: http://www.qualcomm.com/~presnick/
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 56]
+
+RFC 5322 Internet Message Format October 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 57]
+
diff --git a/rfc/rfc5804.txt b/rfc/rfc5804.txt
@@ -0,0 +1,2747 @@
+
+
+
+
+
+
+Internet Engineering Task Force (IETF) A. Melnikov, Ed.
+Request for Comments: 5804 Isode Limited
+Category: Standards Track T. Martin
+ISSN: 2070-1721 BeThereBeSquare, Inc.
+ July 2010
+
+
+ A Protocol for Remotely Managing Sieve Scripts
+
+Abstract
+
+ Sieve scripts allow users to filter incoming email. Message stores
+ are commonly sealed servers so users cannot log into them, yet users
+ must be able to update their scripts on them. This document
+ describes a protocol "ManageSieve" for securely managing Sieve
+ scripts on a remote server. This protocol allows a user to have
+ multiple scripts, and also alerts a user to syntactically flawed
+ scripts.
+
+Status of This Memo
+
+ This is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc5804.
+
+Copyright Notice
+
+ Copyright (c) 2010 IETF Trust and the persons identified as the
+ document authors. All rights reserved.
+
+ This document is subject to BCP 78 and the IETF Trust's Legal
+ Provisions Relating to IETF Documents
+ (http://trustee.ietf.org/license-info) in effect on the date of
+ publication of this document. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+
+
+
+Melnikov & Martin Standards Track [Page 1]
+
+RFC 5804 ManageSieve July 2010
+
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Commands and Responses .....................................3
+ 1.2. Syntax .....................................................3
+ 1.3. Response Codes .............................................3
+ 1.4. Active Script ..............................................6
+ 1.5. Quotas .....................................................6
+ 1.6. Script Names ...............................................6
+ 1.7. Capabilities ...............................................7
+ 1.8. Transport ..................................................9
+ 1.9. Conventions Used in This Document .........................10
+ 2. Commands .......................................................10
+ 2.1. AUTHENTICATE Command ......................................11
+ 2.1.1. Use of SASL PLAIN Mechanism over TLS ...............16
+ 2.2. STARTTLS Command ..........................................16
+ 2.2.1. Server Identity Check ..............................17
+ 2.3. LOGOUT Command ............................................20
+ 2.4. CAPABILITY Command ........................................20
+ 2.5. HAVESPACE Command .........................................20
+ 2.6. PUTSCRIPT Command .........................................21
+ 2.7. LISTSCRIPTS Command .......................................23
+ 2.8. SETACTIVE Command .........................................24
+ 2.9. GETSCRIPT Command .........................................25
+ 2.10. DELETESCRIPT Command .....................................25
+ 2.11. RENAMESCRIPT Command .....................................26
+ 2.12. CHECKSCRIPT Command ......................................27
+ 2.13. NOOP Command .............................................28
+ 2.14. Recommended Extensions ...................................28
+ 2.14.1. UNAUTHENTICATE Command ............................28
+ 3. Sieve URL Scheme ...............................................29
+ 4. Formal Syntax ..................................................31
+ 5. Security Considerations ........................................37
+ 6. IANA Considerations ............................................38
+ 6.1. ManageSieve Capability Registration Template ..............39
+ 6.2. Registration of Initial ManageSieve Capabilities ..........39
+ 6.3. ManageSieve Response Code Registration Template ...........41
+ 6.4. Registration of Initial ManageSieve Response Codes ........41
+ 7. Internationalization Considerations ............................46
+ 8. Acknowledgements ...............................................46
+ 9. References .....................................................47
+ 9.1. Normative References ......................................47
+ 9.2. Informative References ....................................48
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 2]
+
+RFC 5804 ManageSieve July 2010
+
+
+1. Introduction
+
+1.1. Commands and Responses
+
+ A ManageSieve connection consists of the establishment of a client/
+ server network connection, an initial greeting from the server, and
+ client/server interactions. These client/server interactions consist
+ of a client command, server data, and a server completion result
+ response.
+
+ All interactions transmitted by client and server are in the form of
+ lines, that is, strings that end with a CRLF. The protocol receiver
+ of a ManageSieve client or server is either reading a line or reading
+ a sequence of octets with a known count followed by a line.
+
+1.2. Syntax
+
+ ManageSieve is a line-oriented protocol much like [IMAP] or [ACAP],
+ which runs over TCP. There are three data types: atoms, numbers and
+ strings. Strings may be quoted or literal. See [ACAP] for detailed
+ descriptions of these types.
+
+ Each command consists of an atom (the command name) followed by zero
+ or more strings and numbers terminated by CRLF.
+
+ All client queries are replied to with either an OK, NO, or BYE
+ response. Each response may be followed by a response code (see
+ Section 1.3) and by a string consisting of human-readable text in the
+ local language (as returned by the LANGUAGE capability; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. The contents of the string
+ SHOULD be shown to the user ,and implementations MUST NOT attempt to
+ parse the message for meaning.
+
+ The BYE response SHOULD be used if the server wishes to close the
+ connection. A server may wish to do this because the client was idle
+ for too long or there were too many failed authentication attempts.
+ This response can be issued at any time and should be immediately
+ followed by a server hang-up of the connection. If a server has an
+ inactivity timeout resulting in client autologout, it MUST be no less
+ than 30 minutes after successful authentication. The inactivity
+ timeout MAY be less before authentication.
+
+1.3. Response Codes
+
+ An OK, NO, or BYE response from the server MAY contain a response
+ code to describe the event in a more detailed machine-parsable
+ fashion. A response code consists of data inside parentheses in the
+ form of an atom, possibly followed by a space and arguments.
+
+
+
+Melnikov & Martin Standards Track [Page 3]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response codes are defined when there is a specific action that a
+ client can take based upon the additional information. In order to
+ support future extension, the response code is represented as a
+ slash-separated (Solidus, %x2F) hierarchy with each level of
+ hierarchy representing increasing detail about the error. Response
+ codes MUST NOT start with the Solidus character. Clients MUST
+ tolerate additional hierarchical response code detail that they don't
+ understand. For example, if the client supports the "QUOTA" response
+ code, but doesn't understand the "QUOTA/MAXSCRIPTS" response code, it
+ should treat "QUOTA/MAXSCRIPTS" as "QUOTA".
+
+ Client implementations MUST tolerate (ignore) response codes that
+ they do not recognize.
+
+ The currently defined response codes are the following:
+
+ AUTH-TOO-WEAK
+
+ This response code is returned in the NO or BYE response from an
+ AUTHENTICATE command. It indicates that site security policy forbids
+ the use of the requested mechanism for the specified authentication
+ identity.
+
+ ENCRYPT-NEEDED
+
+ This response code is returned in the NO or BYE response from an
+ AUTHENTICATE command. It indicates that site security policy
+ requires the use of a strong encryption mechanism for the specified
+ authentication identity and mechanism.
+
+ QUOTA
+
+ If this response code is returned in the NO/BYE response, it means
+ that the command would have placed the user above the site-defined
+ quota constraints. If this response code is returned in the OK
+ response, it can mean that the user's storage is near its quota, or
+ it can mean that the account exceeded its quota but that the
+ condition is being allowed by the server (the server supports
+ so-called soft quotas). The QUOTA response code has two more
+ detailed variants: "QUOTA/MAXSCRIPTS" (the maximum number of per-user
+ scripts) and "QUOTA/MAXSIZE" (the maximum script size).
+
+ REFERRAL
+
+ This response code may be returned with a BYE result from any
+ command, and includes a mandatory parameter that indicates what
+ server to access to manage this user's Sieve scripts. The server
+ will be specified by a Sieve URL (see Section 3). The scriptname
+
+
+
+Melnikov & Martin Standards Track [Page 4]
+
+RFC 5804 ManageSieve July 2010
+
+
+ portion of the URL MUST NOT be specified. The client should
+ authenticate to the specified server and use it for all further
+ commands in the current session.
+
+ SASL
+
+ This response code can occur in the OK response to a successful
+ AUTHENTICATE command and includes the optional final server response
+ data from the server as specified by [SASL].
+
+ TRANSITION-NEEDED
+
+ This response code occurs in a NO response of an AUTHENTICATE
+ command. It indicates that the user name is valid, but the entry in
+ the authentication database needs to be updated in order to permit
+ authentication with the specified mechanism. This is typically done
+ by establishing a secure channel using TLS, verifying server identity
+ as specified in Section 2.2.1, and finally authenticating once using
+ the [PLAIN] authentication mechanism. The selected mechanism SHOULD
+ then work for authentications in subsequent sessions.
+
+ This condition can happen if a user has an entry in a system
+ authentication database such as Unix /etc/passwd, but does not have
+ credentials suitable for use by the specified mechanism.
+
+ TRYLATER
+
+ A command failed due to a temporary server failure. The client MAY
+ continue using local information and try the command later. This
+ response code only makes sense when returned in a NO/BYE response.
+
+ ACTIVE
+
+ A command failed because it is not allowed on the active script, for
+ example, DELETESCRIPT on the active script. This response code only
+ makes sense when returned in a NO/BYE response.
+
+ NONEXISTENT
+
+ A command failed because the referenced script name doesn't exist.
+ This response code only makes sense when returned in a NO/BYE
+ response.
+
+ ALREADYEXISTS
+
+ A command failed because the referenced script name already exists.
+ This response code only makes sense when returned in a NO/BYE
+ response.
+
+
+
+Melnikov & Martin Standards Track [Page 5]
+
+RFC 5804 ManageSieve July 2010
+
+
+ TAG
+
+ This response code name is followed by a string specified in the
+ command. See Section 2.13 for a possible use case.
+
+ WARNINGS
+
+ This response code MAY be returned by the server in the OK response
+ (but it might be returned with the NO/BYE response as well) and
+ signals the client that even though the script is syntactically
+ valid, it might contain errors not intended by the script writer.
+ This response code is typically returned in response to PUTSCRIPT
+ and/or CHECKSCRIPT commands. A client seeing such response code
+ SHOULD present the returned warning text to the user.
+
+1.4. Active Script
+
+ A user may have multiple Sieve scripts on the server, yet only one
+ script may be used for filtering of incoming messages. This is the
+ active script. Users may have zero or one active script and MUST use
+ the SETACTIVE command described below for changing the active script
+ or disabling Sieve processing. For example, users may have an
+ everyday script they normally use and a special script they use when
+ they go on vacation. Users can change which script is being used
+ without having to download and upload a script stored somewhere else.
+
+1.5. Quotas
+
+ Servers SHOULD impose quotas to prevent malicious users from
+ overflowing available storage. If a command would place a user over
+ a quota setting, servers that impose such quotas MUST reply with a NO
+ response containing the QUOTA response code. Client implementations
+ MUST be able to handle commands failing because of quota
+ restrictions.
+
+1.6. Script Names
+
+ A Sieve script name is a sequence of Unicode characters encoded in
+ UTF-8 [UTF-8]. A script name MUST comply with Net-Unicode Definition
+ (Section 2 of [NET-UNICODE]), with the additional restriction of
+ prohibiting the following Unicode characters:
+
+ o 0000-001F; [CONTROL CHARACTERS]
+
+ o 007F; DELETE
+
+ o 0080-009F; [CONTROL CHARACTERS]
+
+
+
+
+Melnikov & Martin Standards Track [Page 6]
+
+RFC 5804 ManageSieve July 2010
+
+
+ o 2028; LINE SEPARATOR
+
+ o 2029; PARAGRAPH SEPARATOR
+
+ Sieve script names MUST be at least one octet (and hence Unicode
+ character) long. Zero octets script name has a special meaning (see
+ Section 2.8). Servers MUST allow names of up to 128 Unicode
+ characters in length (which can take up to 512 bytes when encoded in
+ UTF-8, not counting the terminating NUL), and MAY allow longer names.
+ A server that receives a script name longer than its internal limit
+ MUST reject the corresponding operation, in particular it MUST NOT
+ truncate the script name.
+
+1.7. Capabilities
+
+ Server capabilities are sent automatically by the server upon a
+ client connection, or after successful STARTTLS and AUTHENTICATE
+ (which establishes a Simple Authentication and Security Layer (SASL))
+ commands. Capabilities may change immediately after a successfully
+ completed STARTTLS command, and/or immediately after a successfully
+ completed AUTHENTICATE command, and/or after a successfully completed
+ UNAUTHENTICATE command (see Section 2.14.1). Capabilities MUST
+ remain static at all other times.
+
+ Clients MAY request the capabilities at a later time by issuing the
+ CAPABILITY command described later. The capabilities consist of a
+ series of lines each with one or two strings. The first string is
+ the name of the capability, which is case-insensitive. The second
+ optional string is the value associated with that capability. Order
+ of capabilities is arbitrary, but each capability name can appear at
+ most once.
+
+ The following capabilities are defined in this document:
+
+ IMPLEMENTATION - Name of implementation and version. This capability
+ MUST always be returned by the server.
+
+ SASL - List of SASL mechanisms supported by the server, each
+ separated by a space. This list can be empty if and only if STARTTLS
+ is also advertised. This means that the client must negotiate TLS
+ encryption with STARTTLS first, at which point the SASL capability
+ will list a non-empty list of SASL mechanisms.
+
+ SIEVE - List of space-separated Sieve extensions (as listed in Sieve
+ "require" action [SIEVE]) supported by the Sieve engine. This
+ capability MUST always be returned by the server.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 7]
+
+RFC 5804 ManageSieve July 2010
+
+
+ STARTTLS - If TLS [TLS] is supported by this implementation. Before
+ advertising this capability a server MUST verify to the best of its
+ ability that TLS can be successfully negotiated by a client with
+ common cipher suites. Specifically, a server should verify that a
+ server certificate has been installed and that the TLS subsystem has
+ successfully initialized. This capability SHOULD NOT be advertised
+ once STARTTLS or AUTHENTICATE command completes successfully. Client
+ and server implementations MUST implement the STARTTLS extension.
+
+ MAXREDIRECTS - Specifies the limit on the number of Sieve "redirect"
+ actions a script can perform during a single evaluation. Note that
+ this is different from the total number of "redirect" actions a
+ script can contain. The value is a non-negative number represented
+ as a ManageSieve string.
+
+ NOTIFY - A space-separated list of URI schema parts for supported
+ notification methods. This capability MUST be specified if the Sieve
+ implementation supports the "enotify" extension [NOTIFY].
+
+ LANGUAGE - The language (<Language-Tag> from [RFC5646]) currently
+ used for human-readable error messages. If this capability is not
+ returned, the "i-default" [RFC2277] language is assumed. Note that
+ the current language MAY be per-user configurable (i.e., it MAY
+ change after authentication).
+
+ OWNER - The canonical name of the logged-in user (SASL "authorization
+ identity") encoded in UTF-8. This capability MUST NOT be returned in
+ unauthenticated state and SHOULD be returned once the AUTHENTICATE
+ command succeeds.
+
+ VERSION - This capability MUST be returned by servers compliant with
+ this document or its successor. For servers compliant with this
+ document, the capability value is the string "1.0". Lack of this
+ capability means that the server predates this specification and thus
+ doesn't support the following commands: RENAMESCRIPT, CHECKSCRIPT,
+ and NOOP.
+
+ Section 2.14 defines some additional ManageSieve extensions and their
+ respective capabilities.
+
+ A server implementation MUST return SIEVE, IMPLEMENTATION, and
+ VERSION capabilities.
+
+ A client implementation MUST ignore any listed capabilities that it
+ does not understand.
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 8]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Example:
+
+ S: "IMPlemENTATION" "Example1 ManageSieved v001"
+ S: "SASl" "DIGEST-MD5 GSSAPI"
+ S: "SIeVE" "fileinto vacation"
+ S: "StaRTTLS"
+ S: "NOTIFY" "xmpp mailto"
+ S: "MAXREdIRECTS" "5"
+ S: "VERSION" "1.0"
+ S: OK
+
+ After successful authentication, this might look like this:
+
+ Example:
+
+ S: "IMPlemENTATION" "Example1 ManageSieved v001"
+ S: "SASl" "DIGEST-MD5 GSSAPI"
+ S: "SIeVE" "fileinto vacation"
+ S: "NOTIFY" "xmpp mailto"
+ S: "OWNER" "alexey@example.com"
+ S: "MAXREdIRECTS" "5"
+ S: "VERSION" "1.0"
+ S: OK
+
+1.8. Transport
+
+ The ManageSieve protocol assumes a reliable data stream such as that
+ provided by TCP. When TCP is used, a ManageSieve server typically
+ listens on port 4190.
+
+ Before opening the TCP connection, the ManageSieve client first MUST
+ resolve the Domain Name System (DNS) hostname associated with the
+ receiving entity and determine the appropriate TCP port for
+ communication with the receiving entity. The process is as follows:
+
+ 1. Attempt to resolve the hostname using a [DNS-SRV] Service of
+ "sieve" and a Proto of "tcp" for the target domain (e.g.,
+ "example.net"), resulting in resource records such as
+ "_sieve._tcp.example.net.". The result of the SRV lookup, if
+ successful, will be one or more combinations of a port and
+ hostname; the ManageSieve client MUST resolve the returned
+ hostnames to IPv4/IPv6 addresses according to returned SRV record
+ weight. IP addresses from the first successfully resolved
+ hostname (with the corresponding port number returned by SRV
+ lookup) are used to connect to the server. If connection using
+ one of the IP addresses fails, the next resolved IP address is
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 9]
+
+RFC 5804 ManageSieve July 2010
+
+
+ used to connect. If connection to all resolved IP addresses
+ fails, then the resolution/connect is repeated for the next
+ hostname returned by SRV lookup.
+
+ 2. If the SRV lookup fails, the fallback SHOULD be a normal IPv4 or
+ IPv6 address record resolution to determine the IP address, where
+ the port used is the default ManageSieve port of 4190.
+
+1.9. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [KEYWORDS].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. Line breaks that do not start a new "C:" or
+ "S:" exist for editorial reasons.
+
+ Examples of authentication in this document are using DIGEST-MD5
+ [DIGEST-MD5] and GSSAPI [GSSAPI] SASL mechanisms.
+
+2. Commands
+
+ This section and its subsections describe valid ManageSieve commands.
+ Upon initial connection to the server, the client's session is in
+ non-authenticated state. Prior to successful authentication, only
+ the AUTHENTICATE, CAPABILITY, STARTTLS, LOGOUT, and NOOP (see Section
+ 2.13) commands are valid. ManageSieve extensions MAY define other
+ commands that are valid in non-authenticated state. Servers MUST
+ reject all other commands with a NO response. Clients may pipeline
+ commands (send more than one command at a time without waiting for
+ completion of the first command). However, a group of commands sent
+ together MUST NOT have an AUTHENTICATE (*), a STARTTLS, or a
+ HAVESPACE command anywhere but the last command in the list.
+
+ (*) - The only exception to this rule is when the AUTHENTICATE
+ command contains an initial response for a SASL mechanism that allows
+ clients to send data first, the mechanism is known to complete in one
+ round trip, and the mechanism doesn't negotiate a SASL security
+ layer. Two examples of such SASL mechanisms are PLAIN [PLAIN] and
+ EXTERNAL [SASL].
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 10]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.1. AUTHENTICATE Command
+
+ Arguments: String - mechanism
+ String - initial data (optional)
+
+ The AUTHENTICATE command indicates a SASL [SASL] authentication
+ mechanism to the server. If the server supports the requested
+ authentication mechanism, it performs an authentication protocol
+ exchange to identify and authenticate the user. Optionally, it also
+ negotiates a security layer for subsequent protocol interactions. If
+ the requested authentication mechanism is not supported, the server
+ rejects the AUTHENTICATE command by sending the NO response.
+
+ The authentication protocol exchange consists of a series of server
+ challenges and client responses that are specific to the selected
+ authentication mechanism. A server challenge consists of a string
+ (quoted or literal) followed by a CRLF. The contents of the string
+ is a base-64 encoding [BASE64] of the SASL data. A client response
+ consists of a string (quoted or literal) with the base-64 encoding of
+ the SASL data followed by a CRLF. If the client wishes to cancel the
+ authentication exchange, it issues a string containing a single "*".
+ If the server receives such a response, it MUST reject the
+ AUTHENTICATE command by sending a NO reply.
+
+ Note that an empty challenge/response is sent as an empty string. If
+ the mechanism dictates that the final response is sent by the server,
+ this data MAY be placed within the data portion of the SASL response
+ code to save a round trip.
+
+ The optional initial-response argument to the AUTHENTICATE command is
+ used to save a round trip when using authentication mechanisms that
+ are defined to send no data in the initial challenge. When the
+ initial-response argument is used with such a mechanism, the initial
+ empty challenge is not sent to the client and the server uses the
+ data in the initial-response argument as if it were sent in response
+ to the empty challenge. If the initial-response argument to the
+ AUTHENTICATE command is used with a mechanism that sends data in the
+ initial challenge, the server MUST reject the AUTHENTICATE command by
+ sending the NO response.
+
+ The service name specified by this protocol's profile of SASL is
+ "sieve".
+
+ Reauthentication is not supported by ManageSieve protocol's profile
+ of SASL. That is, after a successfully completed AUTHENTICATE
+ command, no more AUTHENTICATE commands may be issued in the same
+ session. After a successful AUTHENTICATE command completes, a server
+ MUST reject any further AUTHENTICATE commands with a NO reply.
+
+
+
+Melnikov & Martin Standards Track [Page 11]
+
+RFC 5804 ManageSieve July 2010
+
+
+ However, note that a server may implement the UNAUTHENTICATE
+ extension described in Section 2.14.1.
+
+ If a security layer is negotiated through the SASL authentication
+ exchange, it takes effect immediately following the CRLF that
+ concludes the successful authentication exchange for the client, and
+ the CRLF of the OK response for the server.
+
+ When a security layer takes effect, the ManageSieve protocol is reset
+ to the initial state (the state in ManageSieve after a client has
+ connected to the server). The server MUST discard any knowledge
+ obtained from the client that was not obtained from the SASL (or TLS)
+ negotiation itself. Likewise, the client MUST discard any knowledge
+ obtained from the server, such as the list of ManageSieve extensions,
+ that was not obtained from the SASL (and/or TLS) negotiation itself.
+ (Note that a client MAY compare the advertised SASL mechanisms before
+ and after authentication in order to detect an active down-
+ negotiation attack. See below.)
+
+ Once a SASL security layer is established, the server MUST re-issue
+ the capability results, followed by an OK response. This is
+ necessary to protect against man-in-the-middle attacks that alter the
+ capabilities list prior to SASL negotiation. The capability results
+ MUST include all SASL mechanisms the server was capable of
+ negotiating with that client. This is done in order to allow the
+ client to detect an active down-negotiation attack. If a user-
+ oriented client detects such a down-negotiation attack, it SHOULD
+ either notify the user (it MAY give the user the opportunity to
+ continue with the ManageSieve session in this case) or close the
+ transport connection and indicate that a down-negotiation attack
+ might be in progress. If an automated client detects a down-
+ negotiation attack, it SHOULD return or log an error indicating that
+ a possible attack might be in progress and/or SHOULD close the
+ transport connection.
+
+ When both [TLS] and SASL security layers are in effect, the TLS
+ encoding MUST be applied (when sending data) after the SASL encoding.
+
+ Server implementations SHOULD support SASL proxy authentication so
+ that an administrator can administer a user's scripts. Proxy
+ authentication is when a user authenticates as herself/himself but
+ requests the server to act (authorize) as another user.
+
+ The authorization identity generated by this [SASL] exchange is a
+ "simple username" (in the sense defined in [SASLprep]), and both
+ client and server MUST use the [SASLprep] profile of the [StringPrep]
+ algorithm to prepare these names for transmission or comparison. If
+ preparation of the authorization identity fails or results in an
+
+
+
+Melnikov & Martin Standards Track [Page 12]
+
+RFC 5804 ManageSieve July 2010
+
+
+ empty string (unless it was transmitted as the empty string), the
+ server MUST fail the authentication.
+
+ If an AUTHENTICATE command fails with a NO response, the client MAY
+ try another authentication mechanism by issuing another AUTHENTICATE
+ command. In other words, the client may request authentication types
+ in decreasing order of preference.
+
+ Note that a failed (NO) response to the AUTHENTICATE command may
+ contain one of the following response codes: AUTH-TOO-WEAK, ENCRYPT-
+ NEEDED, or TRANSITION-NEEDED. See Section 1.3 for detailed
+ description of the relevant conditions.
+
+ To ensure interoperability, both client and server implementations of
+ the ManageSieve protocol MUST implement the SCRAM-SHA-1 [SCRAM] SASL
+ mechanism, as well as [PLAIN] over [TLS].
+
+ Note: use of PLAIN over TLS reflects current use of PLAIN over TLS in
+ other email-related protocols; however, a longer-term goal is to
+ migrate email-related protocols from using PLAIN over TLS to SCRAM-
+ SHA-1 mechanism.
+
+ Examples (Note that long lines are folded for readability and are not
+ part of protocol exchange):
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: "VERSION" "1.0"
+ S: OK
+ C: Authenticate "DIGEST-MD5"
+ S: "cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
+ 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
+ cyxjaGFyc2V0PXV0Zi04"
+ C: "Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
+ QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
+ aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
+ N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
+ ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
+ A9YXV0aA=="
+ S: OK (SASL "cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZ
+ mZmZA==")
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 13]
+
+RFC 5804 ManageSieve July 2010
+
+
+ A slightly different variant of the same authentication exchange is:
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "VERSION" "1.0"
+ S: "STARTTLS"
+ S: OK
+ C: Authenticate "DIGEST-MD5"
+ S: {136}
+ S: cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
+ 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
+ cyxjaGFyc2V0PXV0Zi04
+ C: {300+}
+ C: Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
+ QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
+ aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
+ N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
+ ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
+ A9YXV0aA==
+ S: {56}
+ S: cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
+ C: ""
+ S: OK
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 14]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Another example demonstrating use of SASL PLAIN mechanism under TLS
+ follows. This example also demonstrate use of SASL "initial
+ response" (the second parameter to the Authenticate command):
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" ""
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: OK
+ C: STARTTLS
+ S: OK
+ <TLS negotiation, further commands are under TLS layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN"
+ S: "SIEVE" "fileinto vacation"
+ S: OK
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xu"
+ S: NO
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xz"
+ S: NO
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xy"
+ S: BYE "Too many failed authentication attempts"
+ <Server closes connection>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 15]
+
+RFC 5804 ManageSieve July 2010
+
+
+ The following example demonstrates use of SASL "initial response".
+ It also demonstrates that an empty response can be sent as a literal
+ and that negotiating a SASL security layer results in the server
+ re-issuing server capabilities:
+
+ C: AUTHENTICATE "GSSAPI" {1488+}
+ C: YIIE[...1480 octets here ...]dA==
+ S: {208}
+ S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKic
+ [...114 octets here ...]
+ /yzpAy9p+Y0LanLskOTvMc0MnjgAa4YEr3eJ6
+ C: {0+}
+ C:
+ S: {44}
+ S: BQQF/wAMAAwAAAAAYRGFAo6W0vIHti8i1UXODgEAEAA=
+ C: {44+}
+ C: BQQE/wAMAAwAAAAAIsT1iv9UkZApw471iXt6cwEAAAE=
+ S: OK
+ <Further commands/responses are under SASL security layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "LANGUAGE" "ru"
+ S: "MAXREDIRECTS" "3"
+ S: ok
+
+2.1.1. Use of SASL PLAIN Mechanism over TLS
+
+ This section is normative for ManageSieve client implementations that
+ support SASL [PLAIN] over [TLS].
+
+ If a ManageSieve client is willing to use SASL PLAIN over TLS to
+ authenticate to the ManageSieve server, the client MUST verify the
+ server identity (see Section 2.2.1). If the server identity can't be
+ verified (e.g., the server has not provided any certificate, or if
+ the certificate verification fails), the client MUST NOT attempt to
+ authenticate using the SASL PLAIN mechanism.
+
+2.2. STARTTLS Command
+
+ Support for STARTTLS command in servers is optional. Its
+ availability is advertised with "STARTTLS" capability as described in
+ Section 1.7.
+
+ The STARTTLS command requests commencement of a TLS [TLS]
+ negotiation. The negotiation begins immediately after the CRLF in
+ the OK response. After a client issues a STARTTLS command, it MUST
+
+
+
+Melnikov & Martin Standards Track [Page 16]
+
+RFC 5804 ManageSieve July 2010
+
+
+ NOT issue further commands until a server response is seen and the
+ TLS negotiation is complete.
+
+ The STARTTLS command is only valid in non-authenticated state. The
+ server remains in non-authenticated state, even if client credentials
+ are supplied during the TLS negotiation. The SASL [SASL] EXTERNAL
+ mechanism MAY be used to authenticate once TLS client credentials are
+ successfully exchanged, but servers supporting the STARTTLS command
+ are not required to support the EXTERNAL mechanism.
+
+ After the TLS layer is established, the server MUST re-issue the
+ capability results, followed by an OK response. This is necessary to
+ protect against man-in-the-middle attacks that alter the capabilities
+ list prior to STARTTLS. This capability result MUST NOT include the
+ STARTTLS capability.
+
+ The client MUST discard cached capability information and replace it
+ with the new information. The server MAY advertise different
+ capabilities after STARTTLS.
+
+ Example:
+
+ C: StartTls
+ S: oK
+ <TLS negotiation, further commands are under TLS layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "VERSION" "1.0"
+ S: "LANGUAGE" "fr"
+ S: ok
+
+2.2.1. Server Identity Check
+
+ During the TLS negotiation, the ManageSieve client MUST check its
+ understanding of the server hostname/IP address against the server's
+ identity as presented in the server Certificate message, in order to
+ prevent man-in-the-middle attacks. In this section, the client's
+ understanding of the server's identity is called the "reference
+ identity".
+
+ Checking is performed according to the following rules:
+
+ o If the reference identity is a hostname:
+
+ 1. If a subjectAltName extension of the SRVName [X509-SRV],
+ dNSName [X509] (in that order of preference) type is present
+ in the server's certificate, then it SHOULD be used as the
+
+
+
+Melnikov & Martin Standards Track [Page 17]
+
+RFC 5804 ManageSieve July 2010
+
+
+ source of the server's identity. Matching is performed as
+ described in Section 2.2.1.1, with the exception that no
+ wildcard matching is allowed for SRVName type. If the
+ certificate contains multiple names (e.g., more than one
+ dNSName field), then a match with any one of the fields is
+ considered acceptable.
+
+ 2. The client MAY use other types of subjectAltName for
+ performing comparison.
+
+ 3. The server's identity MAY also be verified by comparing the
+ reference identity to the Common Name (CN) [RFC4519] value in
+ the leaf Relative Distinguished Name (RDN) of the subjectName
+ field of the server's certificate. This comparison is
+ performed using the rules for comparison of DNS names in
+ Section 2.2.1.1, below. Although the use of the Common Name
+ value is existing practice, it is deprecated, and
+ Certification Authorities are encouraged to provide
+ subjectAltName values instead. Note that the TLS
+ implementation may represent DNs in certificates according to
+ X.500 or other conventions. For example, some X.500
+ implementations order the RDNs in a DN using a left-to-right
+ (most significant to least significant) convention instead of
+ LDAP's right-to-left convention.
+
+ o When the reference identity is an IP address, the iPAddress
+ subjectAltName SHOULD be used by the client for comparison. The
+ comparison is performed as described in Section 2.2.1.2.
+
+ If the server identity check fails, user-oriented clients SHOULD
+ either notify the user (clients MAY give the user the opportunity to
+ continue with the ManageSieve session in this case) or close the
+ transport connection and indicate that the server's identity is
+ suspect. Automated clients SHOULD return or log an error indicating
+ that the server's identity is suspect and/or SHOULD close the
+ transport connection. Automated clients MAY provide a configuration
+ setting that disables this check, but MUST provide a setting that
+ enables it.
+
+ Beyond the server identity check described in this section, clients
+ should be prepared to do further checking to ensure that the server
+ is authorized to provide the service it is requested to provide. The
+ client may need to make use of local policy information in making
+ this determination.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 18]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.2.1.1. Comparison of DNS Names
+
+ If the reference identity is an internationalized domain name,
+ conforming implementations MUST convert it to the ASCII Compatible
+ Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
+ before comparison with subjectAltName values of type dNSName.
+ Specifically, conforming implementations MUST perform the conversion
+ operation specified in Section 4 of [RFC3490] as follows:
+
+ o in step 1, the domain name SHALL be considered a "stored string";
+
+ o in step 3, set the flag called "UseSTD3ASCIIRules";
+
+ o in step 4, process each label with the "ToASCII" operation; and
+
+ o in step 5, change all label separators to U+002E (full stop).
+
+ After performing the "to-ASCII" conversion, the DNS labels and names
+ MUST be compared for equality according to the rules specified in
+ Section 3 of [RFC3490]; i.e., once all label separators are replaced
+ with U+002E (dot) they are compared in the case-insensitive manner.
+
+ The '*' (ASCII 42) wildcard character is allowed in subjectAltName
+ values of type dNSName, and then only as the left-most (least
+ significant) DNS label in that value. This wildcard matches any
+ left-most DNS label in the server name. That is, the subject
+ *.example.com matches the server names a.example.com and
+ b.example.com, but does not match example.com or a.b.example.com.
+
+2.2.1.2. Comparison of IP Addresses
+
+ When the reference identity is an IP address, the identity MUST be
+ converted to the "network byte order" octet string representation
+ [RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the
+ octet string will contain exactly four octets. For IP Version 6, as
+ specified in RFC 2460, the octet string will contain exactly sixteen
+ octets. This octet string is then compared against subjectAltName
+ values of type iPAddress. A match occurs if the reference identity
+ octet string and value octet strings are identical.
+
+2.2.1.3. Comparison of Other subjectName Types
+
+ Client implementations MAY support matching against subjectAltName
+ values of other types as described in other documents.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 19]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.3. LOGOUT Command
+
+ The client sends the LOGOUT command when it is finished with a
+ connection and wishes to terminate it. The server MUST reply with an
+ OK response. The server MUST ignore commands issued by the client
+ after the LOGOUT command.
+
+ The client SHOULD wait for the OK response before closing the
+ connection. This avoids the TCP connection going into the TIME_WAIT
+ state on the server. In order to avoid going into the TIME_WAIT TCP
+ state, the server MAY wait for a short while for the client to close
+ the TCP connection first. Whether or not the server waits for the
+ client to close the connection, it MUST then close the connection
+ itself.
+
+ Example:
+
+ C: Logout
+ S: Ok
+ <connection is terminated>
+
+2.4. CAPABILITY Command
+
+ The CAPABILITY command requests the server capabilities as described
+ earlier in this document. It has no parameters.
+
+ Example:
+
+ C: CAPABILITY
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN SCRAM-SHA-1 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: OK
+
+2.5. HAVESPACE Command
+
+ Arguments: String - name
+ Number - script size
+
+ The HAVESPACE command is used to query the server for available
+ space. Clients specify the name they wish to save the script as and
+ its size in octets. Both parameters can be used by the server to see
+ if the script with the specified name and size is within a user's
+ quota(s). For example, the server MAY use the script name to check
+ if a script would be replaced or a new one would be created. Servers
+ respond with a NO if storing a script with that name and size would
+
+
+
+Melnikov & Martin Standards Track [Page 20]
+
+RFC 5804 ManageSieve July 2010
+
+
+ fail or OK otherwise. Clients SHOULD issue this command before
+ attempting to place a script on the server.
+
+ Note that the OK response from the HAVESPACE command does not
+ constitute a guarantee of success as server disk space conditions
+ could change between the client issuing the HAVESPACE and the client
+ issuing the PUTSCRIPT commands. A QUOTA response code (see
+ Section 1.3) remains a possible (albeit unlikely) response to a
+ subsequent PUTSCRIPT with the same name and size.
+
+ Example:
+
+ C: HAVESPACE "myscript" 999999
+ S: NO (QUOTA/MAXSIZE) "Quota exceeded"
+
+ C: HAVESPACE "foobar" 435
+ S: OK
+
+2.6. PUTSCRIPT Command
+
+ Arguments: String - Script name
+ String - Script content
+
+ The PUTSCRIPT command is used by the client to submit a Sieve script
+ to the server.
+
+ If the script already exists, upon success the old script will be
+ overwritten. The old script MUST NOT be overwritten if PUTSCRIPT
+ fails in any way. A script of zero length SHOULD be disallowed.
+
+ This command places the script on the server. It does not affect
+ whether the script is processed on incoming mail, unless it replaces
+ the script that is already active. The SETACTIVE command is used to
+ mark a script as active.
+
+ When submitting large scripts, clients SHOULD use the HAVESPACE
+ command beforehand to query if the server is willing to accept a
+ script of that size.
+
+ The server MUST check the submitted script for validity, which
+ includes checking that the script complies with the Sieve grammar
+ [SIEVE] and that all Sieve extensions mentioned in the script's
+ "require" statement(s) are supported by the Sieve interpreter. (Note
+ that if the Sieve interpreter supports the Sieve "ihave" extension
+ [I-HAVE], any unrecognized/unsupported extension mentioned in the
+ "ihave" test MUST NOT cause the validation failure.) Other checks
+ such as validating the supplied command arguments for each command
+ MAY be performed. Essentially, the performed validation SHOULD be
+
+
+
+Melnikov & Martin Standards Track [Page 21]
+
+RFC 5804 ManageSieve July 2010
+
+
+ the same as performed when compiling the script for execution.
+ Implementations that use a binary representation to store compiled
+ scripts can extend the validation to a full compilation, in order to
+ avoid validating uploaded scripts multiple times.
+
+ If the script fails the validation, the server MUST reply with a NO
+ response. Any script that fails the validity test MUST NOT be stored
+ on the server. The message given with a NO response MUST be human
+ readable and SHOULD contain a specific error message giving the line
+ number of the first error. Implementors should strive to produce
+ helpful error messages similar to those given by programming language
+ compilers. Client implementations should note that this may be a
+ multiline literal string with more than one error message separated
+ by CRLFs. The human-readable message is in the language returned in
+ the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
+ encoded in UTF-8 [UTF-8].
+
+ An OK response MAY contain the WARNINGS response code. In such a
+ case the human-readable message that follows the OK response SHOULD
+ contain a specific warning message (or messages) giving the line
+ number(s) in the script that might contain errors not intended by the
+ script writer. The human-readable message is in the language
+ returned in the latest LANGUAGE capability (or in "i-default"; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
+ response code SHOULD present the message to the user.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 22]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Examples:
+
+ C: Putscript "foo" {31+}
+ C: #comment
+ C: InvalidSieveCommand
+ C:
+ S: NO "line 2: Syntax error"
+
+ C: Putscript "mysievescript" {110+}
+ C: require ["fileinto"];
+ C:
+ C: if envelope :contains "to" "tmartin+sent" {
+ C: fileinto "INBOX.sent";
+ C: }
+ S: OK
+
+ C: Putscript "myforwards" {190+}
+ C: redirect "111@example.net";
+ C:
+ C: if size :under 10k {
+ C: redirect "mobile@cell.example.com";
+ C: }
+ C:
+ C: if envelope :contains "to" "tmartin+lists" {
+ C: redirect "lists@groups.example.com";
+ C: }
+ S: OK (WARNINGS) "line 8: server redirect action
+ limit is 2, this redirect might be ignored"
+
+2.7. LISTSCRIPTS Command
+
+ This command lists the scripts the user has on the server. Upon
+ success, a list of CRLF-separated script names (each represented as a
+ quoted or literal string) is returned followed by an OK response. If
+ there exists an active script, the atom ACTIVE is appended to the
+ corresponding script name. The atom ACTIVE MUST NOT appear on more
+ than one response line.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 23]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Example:
+
+ C: Listscripts
+ S: "summer_script"
+ S: "vacation_script"
+ S: {13}
+ S: clever"script
+ S: "main_script" ACTIVE
+ S: OK
+
+ C: listscripts
+ S: "summer_script"
+ S: "main_script" active
+ S: OK
+
+2.8. SETACTIVE Command
+
+ Arguments: String - script name
+
+ This command sets a script active. If the script name is the empty
+ string (i.e., ""), then any active script is disabled. Disabling an
+ active script when there is no script active is not an error and MUST
+ result in an OK reply.
+
+ If the script does not exist on the server, then the server MUST
+ reply with a NO response. Such a reply SHOULD contain the
+ NONEXISTENT response code.
+
+ Examples:
+
+ C: Setactive "vacationscript"
+ S: Ok
+
+ C: Setactive ""
+ S: Ok
+
+ C: Setactive "baz"
+ S: No (NONEXISTENT) "There is no script by that name"
+
+ C: Setactive "baz"
+ S: No (NONEXISTENT) {31}
+ S: There is no script by that name
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 24]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.9. GETSCRIPT Command
+
+ Arguments: String - script name
+
+ This command gets the contents of the specified script. If the
+ script does not exist, the server MUST reply with a NO response.
+ Such a reply SHOULD contain the NONEXISTENT response code.
+
+ Upon success, a string with the contents of the script is returned
+ followed by an OK response.
+
+ Example:
+
+ C: Getscript "myscript"
+ S: {54}
+ S: #this is my wonderful script
+ S: reject "I reject all";
+ S:
+ S: OK
+
+2.10. DELETESCRIPT Command
+
+ Arguments: String - script name
+
+ This command is used to delete a user's Sieve script. Servers MUST
+ reply with a NO response if the script does not exist. Such
+ responses SHOULD include the NONEXISTENT response code.
+
+ The server MUST NOT allow the client to delete an active script, so
+ the server MUST reply with a NO response if attempted. Such a
+ response SHOULD contain the ACTIVE response code. If a client wishes
+ to delete an active script, it should use the SETACTIVE command to
+ disable the script first.
+
+ Example:
+
+ C: Deletescript "foo"
+ S: Ok
+
+ C: Deletescript "baz"
+ S: No (ACTIVE) "You may not delete an active script"
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 25]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.11. RENAMESCRIPT Command
+
+ Arguments: String - Old Script name
+ String - New Script name
+
+ This command is used to rename a user's Sieve script. Servers MUST
+ reply with a NO response if the old script does not exist (in which
+ case the NONEXISTENT response code SHOULD be included), or a script
+ with the new name already exists (in which case the ALREADYEXISTS
+ response code SHOULD be included). Renaming the active script is
+ allowed; the renamed script remains active.
+
+ Example:
+
+ C: Renamescript "foo" "bar"
+ S: Ok
+
+ C: Renamescript "baz" "bar"
+ S: No "bar already exists"
+
+ If the server doesn't support the RENAMESCRIPT command, the client
+ can emulate it by performing the following steps:
+
+ 1. List available scripts with LISTSCRIPTS. If the script with the
+ new script name exists, then the client should ask the user
+ whether to abort the operation, to replace the script (by issuing
+ the DELETESCRIPT <newname> after that), or to choose a different
+ name.
+
+ 2. Download the old script with GETSCRIPT <oldname>.
+
+ 3. Upload the old script with the new name: PUTSCRIPT <newname>.
+
+ 4. If the old script was active (as reported by LISTSCRIPTS in step
+ 1), then make the new script active: SETACTIVE <newname>.
+
+ 5. Delete the old script: DELETESCRIPT <oldname>.
+
+ Note that these steps don't describe how to handle various other
+ error conditions (for example, NO response containing QUOTA response
+ code in step 3). Error handling is left as an exercise for the
+ reader.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 26]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.12. CHECKSCRIPT Command
+
+ Arguments: String - Script content
+
+ The CHECKSCRIPT command is used by the client to verify Sieve script
+ validity without storing the script on the server.
+
+ The server MUST check the submitted script for syntactic validity,
+ which includes checking that all Sieve extensions mentioned in Sieve
+ script "require" statement(s) are supported by the Sieve interpreter.
+ (Note that if the Sieve interpreter supports the Sieve "ihave"
+ extension [I-HAVE], any unrecognized/unsupported extension mentioned
+ in the "ihave" test MUST NOT cause the syntactic validation failure.)
+ If the script fails this test, the server MUST reply with a NO
+ response. The message given with a NO response MUST be human
+ readable and SHOULD contain a specific error message giving the line
+ number of the first error. Implementors should strive to produce
+ helpful error messages similar to those given by programming language
+ compilers. Client implementations should note that this may be a
+ multiline literal string with more than one error message separated
+ by CRLFs. The human-readable message is in the language returned in
+ the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
+ encoded in UTF-8 [UTF-8].
+
+ Examples:
+
+ C: CheckScript {31+}
+ C: #comment
+ C: InvalidSieveCommand
+ C:
+ S: NO "line 2: Syntax error"
+
+ A ManageSieve server supporting this command MUST NOT check if the
+ script will put the current user over its quota limit.
+
+ An OK response MAY contain the WARNINGS response code. In such a
+ case, the human-readable message that follows the OK response SHOULD
+ contain a specific warning message (or messages) giving the line
+ number(s) in the script that might contain errors not intended by the
+ script writer. The human-readable message is in the language
+ returned in the latest LANGUAGE capability (or in "i-default"; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
+ response code SHOULD present the message to the user.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 27]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.13. NOOP Command
+
+ Arguments: String - tag to echo back (optional)
+
+ The NOOP command does nothing, beyond returning a response to the
+ client. It may be used by clients for protocol re-synchronization or
+ to reset any inactivity auto-logout timer on the server.
+
+ The response to the NOOP command is always OK, followed by the TAG
+ response code together with the supplied string. If no string was
+ supplied in the NOOP command, the TAG response code MUST NOT be
+ included.
+
+ Examples:
+
+ C: NOOP
+ S: OK "NOOP completed"
+
+ C: NOOP "STARTTLS-SYNC-42"
+ S: OK (TAG {16}
+ S: STARTTLS-SYNC-42) "Done"
+
+2.14. Recommended Extensions
+
+ The UNAUTHENTICATE extension (advertised as the "UNAUTHENTICATE"
+ capability with no parameters) defines a new UNAUTHENTICATE command,
+ which allows a client to return the server to non-authenticated
+ state. Support for this extension is RECOMMENDED.
+
+2.14.1. UNAUTHENTICATE Command
+
+ The UNAUTHENTICATE command returns the server to the
+ non-authenticated state. It doesn't affect any previously
+ established TLS [TLS] or SASL (Section 2.1) security layer.
+
+ The UNAUTHENTICATE command is only valid in authenticated state. If
+ issued in a wrong state, the server MUST reject it with a NO
+ response.
+
+ The UNAUTHENTICATE command has no parameters.
+
+ When issued in the authenticated state, the UNAUTHENTICATE command
+ MUST NOT fail (i.e., it must never return anything other than OK or
+ BYE).
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 28]
+
+RFC 5804 ManageSieve July 2010
+
+
+3. Sieve URL Scheme
+
+ URI scheme name: sieve
+
+ Status: permanent
+
+ URI scheme syntax: Described using ABNF [ABNF]. Some ABNF
+ productions not defined below are from [URI-GEN].
+
+ sieveurl = sieveurl-server / sieveurl-list-scripts /
+ sieveurl-script
+
+ sieveurl-server = "sieve://" authority
+
+ sieveurl-list-scripts = "sieve://" authority ["/"]
+
+ sieveurl-script = "sieve://" authority "/"
+ [owner "/"] scriptname
+
+ authority = <defined in [URI-GEN]>
+
+ owner = *ochar
+ ;; %-encoded version of [SASL] authorization
+ ;; identity (script owner) or "userid".
+ ;;
+ ;; Empty owner is used to reference
+ ;; global scripts.
+ ;;
+ ;; Note that ASCII characters such as " ", ";",
+ ;; "&", "=", "/" and "?" must be %-encoded
+ ;; as per rule specified in [URI-GEN].
+
+ scriptname = 1*ochar
+ ;; %-encoded version of UTF-8 representation
+ ;; of the script name.
+ ;; Note that ASCII characters such as " ", ";",
+ ;; "&", "=", "/" and "?" must be %-encoded
+ ;; as per rule specified in [URI-GEN].
+
+ ochar = unreserved / pct-encoded / sub-delims-sh /
+ ":" / "@"
+ ;; Same as [URI-GEN] 'pchar',
+ ;; but without ";", "&" and "=".
+
+ unreserved = <defined in [URI-GEN]>
+
+ pct-encoded = <defined in [URI-GEN]>
+
+
+
+
+Melnikov & Martin Standards Track [Page 29]
+
+RFC 5804 ManageSieve July 2010
+
+
+ sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
+ "*" / "+" / ","
+ ;; Same as [URI-GEN] sub-delims,
+ ;; but without ";", "&" and "=".
+
+ URI scheme semantics:
+
+ A Sieve URL identifies a Sieve server or a Sieve script on a Sieve
+ server. The latter form is associated with the application/sieve
+ MIME type defined in [SIEVE]. There is no MIME type associated
+ with the former form of Sieve URI.
+
+ The server form is used in the REFERRAL response code (see Section
+ 1.3) in order to designate another server where the client should
+ perform its operations.
+
+ The script form allows to retrieve (GETSCRIPT), update
+ (PUTSCRIPT), delete (DELETESCRIPT), or activate (SETACTIVE) the
+ named script; however, the most typical action would be to
+ retrieve the script. If the script name is empty (omitted), the
+ URI requests that the client lists available scripts using the
+ LISTSCRIPTS command.
+
+ Encoding considerations:
+
+ The script name and/or the owner, if present, is in UTF-8. Non--
+ US-ASCII UTF-8 octets MUST be percent-encoded as described in
+ [URI-GEN]. US-ASCII characters such as " " (space), ";", "&",
+ "=", "/" and "?" MUST be %-encoded as described in [URI-GEN].
+ Note that "&" and "?" are in this list in order to allow for
+ future extensions.
+
+ Note that the empty owner (e.g., sieve://example.com//script) is
+ different from the missing owner (e.g.,
+ sieve://example.com/script) and is reserved for referencing global
+ scripts.
+
+ The user name (in the "authority" part), if present, is in UTF-8.
+ Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
+ [URI-GEN].
+
+ Applications/protocols that use this URI scheme name:
+ ManageSieve [RFC5804] clients and servers. Clients that can store
+ user preferences in protocols such as [LDAP] or [ACAP].
+
+ Interoperability considerations: None.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 30]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Security considerations:
+ The <scriptname> part of a ManageSieve URL might potentially disclose
+ some confidential information about the author of the script or,
+ depending on a ManageSieve implementation, about configuration of the
+ mail system. The latter might be used to prepare for a more complex
+ attack on the mail system.
+
+ Clients resolving ManageSieve URLs that wish to achieve data
+ confidentiality and/or integrity SHOULD use the STARTTLS command (if
+ supported by the server) before starting authentication, or use a
+ SASL mechanism, such as GSSAPI, that provides a confidentiality
+ security layer.
+
+ Contact: Alexey Melnikov <alexey.melnikov@isode.com>
+
+ Author/Change controller: IESG.
+
+ References: This document and RFC 5228 [SIEVE].
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (BNF) notation as specified in [ABNF]. This uses the ABNF core
+ rules as specified in Appendix A of the ABNF specification [ABNF].
+ "UTF8-2", "UTF8-3", and "UTF8-4" non-terminal are defined in [UTF-8].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper- or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ SAFE-CHAR = %x01-09 / %x0B-0C / %x0E-21 / %x23-5B /
+ %x5D-7F
+ ;; any TEXT-CHAR except QUOTED-SPECIALS
+
+ QUOTED-CHAR = SAFE-UTF8-CHAR / "\" QUOTED-SPECIALS
+
+ QUOTED-SPECIALS = DQUOTE / "\"
+
+ SAFE-UTF8-CHAR = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4
+ ;; <UTF8-2>, <UTF8-3>, and <UTF8-4>
+ ;; are defined in [UTF-8].
+
+ ATOM-CHAR = "!" / %x23-27 / %x2A-5B / %x5D-7A / %x7C-7E
+ ;; Any CHAR except ATOM-SPECIALS
+
+ ATOM-SPECIALS = "(" / ")" / "{" / SP / CTL / QUOTED-SPECIALS
+
+
+
+
+Melnikov & Martin Standards Track [Page 31]
+
+RFC 5804 ManageSieve July 2010
+
+
+ NZDIGIT = %x31-39
+ ;; 1-9
+
+ atom = 1*1024ATOM-CHAR
+
+ iana-token = atom
+ ;; MUST be registered with IANA
+
+ auth-type = DQUOTE auth-type-name DQUOTE
+
+ auth-type-name = iana-token
+ ;; as defined in SASL [SASL]
+
+ command = (command-any / command-auth /
+ command-nonauth) CRLF
+ ;; Modal based on state
+
+ command-any = command-capability / command-logout /
+ command-noop
+ ;; Valid in all states
+
+ command-auth = command-getscript / command-setactive /
+ command-listscripts / command-deletescript /
+ command-putscript / command-checkscript /
+ command-havespace /
+ command-renamescript /
+ command-unauthenticate
+ ;; Valid only in Authenticated state
+
+ command-nonauth = command-authenticate / command-starttls
+ ;; Valid only when in Non-Authenticated
+ ;; state
+
+ command-authenticate = "AUTHENTICATE" SP auth-type [SP string]
+ *(CRLF string)
+
+ command-capability = "CAPABILITY"
+
+ command-deletescript = "DELETESCRIPT" SP sieve-name
+
+ command-getscript = "GETSCRIPT" SP sieve-name
+
+ command-havespace = "HAVESPACE" SP sieve-name SP number
+
+ command-listscripts = "LISTSCRIPTS"
+
+ command-noop = "NOOP" [SP string]
+
+
+
+
+Melnikov & Martin Standards Track [Page 32]
+
+RFC 5804 ManageSieve July 2010
+
+
+ command-logout = "LOGOUT"
+
+ command-putscript = "PUTSCRIPT" SP sieve-name SP sieve-script
+
+ command-checkscript = "CHECKSCRIPT" SP sieve-script
+
+ sieve-script = string
+
+ command-renamescript = "RENAMESCRIPT" SP old-sieve-name SP
+ new-sieve-name
+
+ old-sieve-name = sieve-name
+
+ new-sieve-name = sieve-name
+
+ command-setactive = "SETACTIVE" SP active-sieve-name
+
+ command-starttls = "STARTTLS"
+
+ command-unauthenticate= "UNAUTHENTICATE"
+
+ extend-token = atom
+ ;; MUST be defined by a Standards Track or
+ ;; IESG-approved experimental protocol
+ ;; extension
+
+ extension-data = extension-item *(SP extension-item)
+
+ extension-item = extend-token / string / number /
+ "(" [extension-data] ")"
+
+ literal-c2s = "{" number "+}" CRLF *OCTET
+ ;; The number represents the number of
+ ;; octets.
+ ;; This type of literal can only be sent
+ ;; from the client to the server.
+
+ literal-s2c = "{" number "}" CRLF *OCTET
+ ;; Almost identical to literal-c2s,
+ ;; but with no '+' character.
+ ;; The number represents the number of
+ ;; octets.
+ ;; This type of literal can only be sent
+ ;; from the server to the client.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 33]
+
+RFC 5804 ManageSieve July 2010
+
+
+ number = (NZDIGIT *DIGIT) / "0"
+ ;; A 32-bit unsigned number
+ ;; with no extra leading zeros.
+ ;; (0 <= n < 4,294,967,296)
+
+ number-str = string
+ ;; <number> encoded as a <string>.
+
+ quoted = DQUOTE *1024QUOTED-CHAR DQUOTE
+ ;; limited to 1024 octets between the <">s
+
+ resp-code = "AUTH-TOO-WEAK" / "ENCRYPT-NEEDED" / "QUOTA"
+ ["/" ("MAXSCRIPTS" / "MAXSIZE")] /
+ resp-code-sasl /
+ resp-code-referral /
+ "TRANSITION-NEEDED" / "TRYLATER" /
+ "ACTIVE" / "NONEXISTENT" /
+ "ALREADYEXISTS" / "WARNINGS" /
+ "TAG" SP string /
+ resp-code-ext
+
+ resp-code-referral = "REFERRAL" SP sieveurl
+
+ resp-code-sasl = "SASL" SP string
+
+ resp-code-name = iana-token
+ ;; The response code name is hierarchical,
+ ;; separated by '/'.
+ ;; The response code name MUST NOT start
+ ;; with '/'.
+
+ resp-code-ext = resp-code-name [SP extension-data]
+ ;; unknown response codes MUST be tolerated
+ ;; by the client.
+
+ response = response-authenticate /
+ response-logout /
+ response-getscript /
+ response-setactive /
+ response-listscripts /
+ response-deletescript /
+ response-putscript /
+ response-checkscript /
+ response-capability /
+ response-havespace /
+ response-starttls /
+ response-renamescript /
+ response-noop /
+
+
+
+Melnikov & Martin Standards Track [Page 34]
+
+RFC 5804 ManageSieve July 2010
+
+
+ response-unauthenticate
+
+ response-authenticate = *(string CRLF)
+ ((response-ok [response-capability]) /
+ response-nobye)
+ ;; <response-capability> is REQUIRED if a
+ ;; SASL security layer was negotiated and
+ ;; MUST be omitted otherwise.
+
+ response-capability = *(single-capability) response-oknobye
+
+ single-capability = capability-name [SP string] CRLF
+
+ capability-name = string
+
+ ;; Note that literal-s2c is allowed.
+
+ initial-capabilities = DQUOTE "IMPLEMENTATION" DQUOTE SP string /
+ DQUOTE "SASL" DQUOTE SP sasl-mechs /
+ DQUOTE "SIEVE" DQUOTE SP sieve-extensions /
+ DQUOTE "MAXREDIRECTS" DQUOTE SP number-str /
+ DQUOTE "NOTIFY" DQUOTE SP notify-mechs /
+ DQUOTE "STARTTLS" DQUOTE /
+ DQUOTE "LANGUAGE" DQUOTE SP language /
+ DQUOTE "VERSION" DQUOTE SP version /
+ DQUOTE "OWNER" DQUOTE SP string
+ ;; Each capability conforms to
+ ;; the syntax for single-capability.
+ ;; Also, note that the capability name
+ ;; can be returned as either literal-s2c
+ ;; or quoted, even though only "quoted"
+ ;; string is shown above.
+
+ version = ( DQUOTE "1.0" DQUOTE ) / version-ext
+
+ version-ext = DQUOTE ver-major "." ver-minor DQUOTE
+ ; Future versions specified in updates
+ ; to this document. An increment to
+ ; the ver-major means a backward-incompatible
+ ; change to the protocol, e.g., "3.5" (ver-major "3")
+ ; is not backward-compatible with any "2.X" version.
+ ; Any version "Z.W" MUST be backward compatible
+ ; with any version "Z.Q", where Q < W.
+ ; For example, version "2.4" is backward compatible
+ ; with version "2.0", "2.1", "2.2", and "2.3".
+
+ ver-major = number
+
+
+
+
+Melnikov & Martin Standards Track [Page 35]
+
+RFC 5804 ManageSieve July 2010
+
+
+ ver-minor = number
+
+ sasl-mechs = string
+ ; Space-separated list of SASL mechanisms,
+ ; each SASL mechanism name complies with rules
+ ; specified in [SASL].
+ ; Can be empty.
+
+ sieve-extensions = string
+ ; Space-separated list of supported SIEVE extensions.
+ ; Can be empty.
+
+ language = string
+ ; Contains <Language-Tag> from [RFC5646].
+
+
+ notify-mechs = string
+ ; Space-separated list of URI schema parts
+ ; for supported notification [NOTIFY] methods.
+ ; MUST NOT be empty.
+
+ response-deletescript = response-oknobye
+
+ response-getscript = (sieve-script CRLF response-ok) /
+ response-nobye
+
+ response-havespace = response-oknobye
+
+ response-listscripts = *(sieve-name [SP "ACTIVE"] CRLF)
+ response-oknobye
+ ;; ACTIVE may only occur with one sieve-name
+
+ response-logout = response-oknobye
+
+ response-unauthenticate= response-oknobye
+ ;; "NO" response can only be returned when
+ ;; the command is issued in a wrong state
+ ;; or has a wrong number of parameters
+
+ response-ok = "OK" [SP "(" resp-code ")"]
+ [SP string] CRLF
+ ;; The string contains human-readable text
+ ;; encoded as UTF-8.
+
+ response-nobye = ("NO" / "BYE") [SP "(" resp-code ")"]
+ [SP string] CRLF
+ ;; The string contains human-readable text
+ ;; encoded as UTF-8.
+
+
+
+Melnikov & Martin Standards Track [Page 36]
+
+RFC 5804 ManageSieve July 2010
+
+
+ response-oknobye = response-ok / response-nobye
+
+ response-noop = response-ok
+
+ response-putscript = response-oknobye
+
+ response-checkscript = response-oknobye
+
+ response-renamescript = response-oknobye
+
+ response-setactive = response-oknobye
+
+ response-starttls = (response-ok response-capability) /
+ response-nobye
+
+ sieve-name = string
+ ;; See Section 1.6 for the full list of
+ ;; prohibited characters.
+ ;; Empty string is not allowed.
+
+ active-sieve-name = string
+ ;; See Section 1.6 for the full list of
+ ;; prohibited characters.
+ ;; This is similar to <sieve-name>, but
+ ;; empty string is allowed and has a special
+ ;; meaning.
+
+ string = quoted / literal-c2s / literal-s2c
+ ;; literal-c2s is only allowed when sent
+ ;; from the client to the server.
+ ;; literal-s2c is only allowed when sent
+ ;; from the server to the client.
+ ;; quoted is allowed in either direction.
+
+5. Security Considerations
+
+ The AUTHENTICATE command uses SASL [SASL] to provide authentication
+ and authorization services. Integrity and privacy services can be
+ provided by [SASL] and/or [TLS]. When a SASL mechanism is used, the
+ security considerations for that mechanism apply.
+
+ This protocol's transactions are susceptible to passive observers or
+ man-in-the-middle attacks that alter the data, unless the optional
+ encryption and integrity services of the SASL (via the AUTHENTICATE
+ command) and/or [TLS] (via the STARTTLS command) are enabled, or an
+ external security mechanism is used for protection. It may be useful
+ to allow configuration of both clients and servers to refuse to
+ transfer sensitive information in the absence of strong encryption.
+
+
+
+Melnikov & Martin Standards Track [Page 37]
+
+RFC 5804 ManageSieve July 2010
+
+
+ If an implementation supports SASL mechanisms that are vulnerable to
+ passive eavesdropping attacks (such as [PLAIN]), then the
+ implementation MUST support at least one configuration where these
+ SASL mechanisms are not advertised or used without the presence of an
+ external security layer such as [TLS].
+
+ Some response codes returned on failed AUTHENTICATE command may
+ disclose whether or not the username is valid (e.g., TRANSITION-
+ NEEDED), so server implementations SHOULD provide the ability to
+ disable these features (or make them not conditional on a per-user
+ basis) for sites concerned about such disclosure. In the case of
+ ENCRYPT-NEEDED, if it is applied to all identities then no extra
+ information is disclosed, but if it is applied on a per-user basis it
+ can disclose information.
+
+ A compromised or malicious server can use the TRANSITION-NEEDED
+ response code to force the client that is configured to use a
+ mechanism that does not disclose the user's password to the server
+ (e.g., Kerberos), to send the bare password to the server. Clients
+ SHOULD have the ability to disable the password transition feature,
+ or disclose that risk to the user and offer the user an option of how
+ to proceed.
+
+6. IANA Considerations
+
+ IANA has reserved TCP port number 4190 for use with the ManageSieve
+ protocol described in this document.
+
+ IANA has registered the "sieve" URI scheme defined in Section 3 of
+ this document.
+
+ IANA has registered "sieve" in the "GSSAPI/Kerberos/SASL Service
+ Names" registry.
+
+ IANA has created a new registry for ManageSieve capabilities. The
+ registration template for ManageSieve capabilities is specified in
+ Section 6.1. ManageSieve protocol capabilities MUST be specified in
+ a Standards-Track or IESG-approved Experimental RFC.
+
+ IANA has created a new registry for ManageSieve response codes. The
+ registration template for ManageSieve response codes is specified in
+ Section 6.3. ManageSieve protocol response codes MUST be specified
+ in a Standards-Track or IESG-approved Experimental RFC.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 38]
+
+RFC 5804 ManageSieve July 2010
+
+
+6.1. ManageSieve Capability Registration Template
+
+ To: iana@iana.org
+ Subject: ManageSieve Capability Registration
+
+ Please register the following ManageSieve capability:
+
+ Capability name:
+ Description:
+ Relevant publications:
+ Person & email address to contact for further information:
+ Author/Change controller:
+
+6.2. Registration of Initial ManageSieve Capabilities
+
+ To: iana@iana.org
+ Subject: ManageSieve Capability Registration
+
+ Please register the following ManageSieve capabilities:
+
+ Capability name: IMPLEMENTATION
+ Description: Its value contains the name of the server
+ implementation and its version.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: SASL
+ Description: Its value contains a space-separated list of SASL
+ mechanisms supported by the server.
+ Relevant publications: this RFC, Sections 1.7 and 2.1.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: SIEVE
+ Description: Its value contains a space-separated list of supported
+ SIEVE extensions.
+ Relevant publications: this RFC, Section 1.7. Also [SIEVE].
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 39]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Capability name: STARTTLS
+ Description: This capability is returned if the server supports TLS
+ (STARTTLS command).
+ Relevant publications: this RFC, Sections 1.7 and 2.2.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: NOTIFY
+ Description: This capability is returned if the server supports the
+ 'enotify' [NOTIFY] Sieve extension.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: MAXREDIRECTS
+ Description: This capability returns the limit on the number of
+ Sieve "redirect" actions a script can perform during a
+ single evaluation. The value is a non-negative number
+ represented as a ManageSieve string.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: LANGUAGE
+ Description: The language (<Language-Tag> from [RFC5646]) currently
+ used for human-readable error messages.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: OWNER
+ Description: Its value contains the UTF-8-encoded name of the
+ currently logged-in user ("authorization identity"
+ according to RFC 4422).
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 40]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Capability name: VERSION
+ Description: This capability is returned if the server is compliant
+ with RFC 5804; i.e., that it supports RENAMESCRIPT,
+ CHECKSCRIPT, and NOOP commands.
+ Relevant publications: this RFC, Sections 2.11, 2.12, and 2.13.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+6.3. ManageSieve Response Code Registration Template
+
+ To: iana@iana.org
+ Subject: ManageSieve Response Code Registration
+
+ Please register the following ManageSieve response code:
+
+ Response Code:
+ Arguments (use ABNF to specify syntax, or the word NONE if none
+ can be specified):
+ Purpose:
+ Published Specification(s):
+ Person & email address to contact for further information:
+ Author/Change controller:
+
+6.4. Registration of Initial ManageSieve Response Codes
+
+ To: iana@iana.org
+ Subject: ManageSieve Response Code Registration
+
+ Please register the following ManageSieve response codes:
+
+ Response Code: AUTH-TOO-WEAK
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code is returned in the NO response from
+ an AUTHENTICATE command. It indicates that site
+ security policy forbids the use of the requested
+ mechanism for the specified authentication identity.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 41]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: ENCRYPT-NEEDED
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code is returned in the NO response from
+ an AUTHENTICATE command. It indicates that site
+ security policy requires the use of a strong
+ encryption mechanism for the specified authentication
+ identity and mechanism.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: QUOTA
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined quota constraints. If
+ this response code is returned in the OK response, it
+ can mean that the user is near its quota or that the
+ user exceeded its quota, but the server supports soft
+ quotas.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: QUOTA/MAXSCRIPTS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined limit on the number of
+ Sieve scripts. If this response code is returned in
+ the OK response, it can mean that the user is near its
+ quota or that the user exceeded its quota, but the
+ server supports soft quotas. This response code is a
+ more specific version of the QUOTA response code.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 42]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: QUOTA/MAXSIZE
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined maximum script size.
+ If this response code is returned in the OK response,
+ it can mean that the user is near its quota or that
+ the user exceeded its quota, but the server supports
+ soft quotas. This response code is a more specific
+ version of the QUOTA response code.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: REFERRAL
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): <sieveurl>
+ Purpose: This response code may be returned with a BYE result
+ from any command, and includes a mandatory parameter
+ that indicates what server to access to manage this
+ user's Sieve scripts. The server will be specified by
+ a Sieve URL (see Section 3). The scriptname portion
+ of the URL MUST NOT be specified. The client should
+ authenticate to the specified server and use it for
+ all further commands in the current session.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: SASL
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): <string>
+ Purpose: This response code can occur in the OK response to a
+ successful AUTHENTICATE command and includes the
+ optional final server response data from the server as
+ specified by [SASL].
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 43]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: TRANSITION-NEEDED
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code occurs in a NO response of an
+ AUTHENTICATE command. It indicates that the user name
+ is valid, but the entry in the authentication database
+ needs to be updated in order to permit authentication
+ with the specified mechanism. This is typically done
+ by establishing a secure channel using TLS, followed
+ by authenticating once using the [PLAIN]
+ authentication mechanism. The selected mechanism
+ SHOULD then work for authentications in subsequent
+ sessions.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: TRYLATER
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed due to a temporary server failure.
+ The client MAY continue using local information and
+ try the command later. This response code only make
+ sense when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: ACTIVE
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because it is not allowed on the
+ active script, for example, DELETESCRIPT on the active
+ script. This response code only makes sense when
+ returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 44]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: NONEXISTENT
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because the referenced script name
+ doesn't exist. This response code only makes sense
+ when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: ALREADYEXISTS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because the referenced script name
+ already exists. This response code only makes sense
+ when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: WARNINGS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code MAY be returned by the server in
+ the OK response (but it might be returned with the NO/
+ BYE response as well) and signals the client that even
+ though the script is syntactically valid, it might
+ contain errors not intended by the script writer.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: TAG
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): string
+ Purpose: This response code name is followed by a string
+ specified in the command that caused this response.
+ It is typically used for client state synchronization.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 45]
+
+RFC 5804 ManageSieve July 2010
+
+
+7. Internationalization Considerations
+
+ The LANGUAGE capability (see Section 1.7) allows a client to discover
+ the current language used in all human-readable responses that might
+ be returned at the end of any OK/NO/BYE response. Human-readable
+ text in OK responses typically doesn't need to be shown to the user,
+ unless it is returned in response to a PUTSCRIPT or CHECKSCRIPT
+ command that also contains the WARNINGS response code (Section 1.3).
+ Human-readable text from NO/BYE responses is intended be shown to the
+ user, unless the client can automatically handle failure of the
+ command that caused such a response. Clients SHOULD use response
+ codes (Section 1.3) for automatic error handling. Response codes MAY
+ also be used by the client to present error messages in a language
+ understood by the user, for example, if the LANGUAGE capability
+ doesn't return a language understood by the user.
+
+ Note that the human-readable text from OK (WARNINGS) or NO/BYE
+ responses for PUTSCRIPT/CHECKSCRIPT commands is intended for advanced
+ users that understand Sieve language. Such advanced users are often
+ sophisticated enough to be able to handle whatever language the
+ server is using, even if it is not their preferred language, and will
+ want to see error/warning text no matter what language the server
+ puts it in.
+
+ A client that generates Sieve script automatically, for example, if
+ the script is generated without user intervention or from a UI that
+ presents an abstract list of conditions and corresponding actions,
+ SHOULD NOT present warning/error messages to the user, because the
+ user might not even be aware that the client is using Sieve
+ underneath. However, if the client has a debugging mode, such
+ warnings/errors SHOULD be available in the debugging mode.
+
+ Note that this document doesn't provide a way to modify the currently
+ used language. It is expected that a future extension will address
+ that.
+
+8. Acknowledgements
+
+ Thanks to Simon Josefsson, Larry Greenfield, Allen Johnson, Chris
+ Newman, Lyndon Nerenberg, Tim Showalter, Sarah Robeson, Walter Wong,
+ Barry Leiba, Arnt Gulbrandsen, Stephan Bosch, Ken Murchison, Phil
+ Pennock, Ned Freed, Jeffrey Hutzelman, Mark E. Mallett, Dilyan
+ Palauzov, Dave Cridland, Aaron Stone, Robert Burrell Donkin, Patrick
+ Ben Koetter, Bjoern Hoehrmann, Martin Duerst, Pasi Eronen, Magnus
+ Westerlund, Tim Polk, and Julien Coloos for help with this document.
+ Special thank you to Phil Pennock for providing text for the NOOP
+ command, as well as finding various bugs in the document.
+
+
+
+
+Melnikov & Martin Standards Track [Page 46]
+
+RFC 5804 ManageSieve July 2010
+
+
+9. References
+
+9.1. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", STD 68, RFC 5234, January 2008.
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November
+ 1997.
+
+ [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
+ Encodings", RFC 4648, October 2006.
+
+ [DNS-SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR
+ for specifying the location of services (DNS SRV)",
+ RFC 2782, February 2000.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [NET-UNICODE] Klensin, J. and M. Padlipsky, "Unicode Format for
+ Network Interchange", RFC 5198, March 2008.
+
+ [NOTIFY] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
+ "Sieve Email Filtering: Extension for Notifications",
+ RFC 5435, January 2009.
+
+ [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
+ Languages", BCP 18, RFC 2277, January 1998.
+
+ [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version
+ 6 (IPv6) Specification", RFC 2460, December 1998.
+
+ [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
+ "Internationalizing Domain Names in Applications
+ (IDNA)", RFC 3490, March 2003.
+
+ [RFC4519] Sciberras, A., "Lightweight Directory Access Protocol
+ (LDAP): Schema for User Applications", RFC 4519, June
+ 2006.
+
+ [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
+ Languages", BCP 47, RFC 5646, September 2009.
+
+ [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
+ September 1981.
+
+
+
+
+Melnikov & Martin Standards Track [Page 47]
+
+RFC 5804 ManageSieve July 2010
+
+
+ [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication
+ and Security Layer (SASL)", RFC 4422, June 2006.
+
+ [SASLprep] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+ [SCRAM] Menon-Sen, A., Melnikov, A., Newman, C., and N.
+ Williams, "Salted Challenge Response Authentication
+ Mechanism (SCRAM) SASL and GSS-API Mechanisms", RFC
+ 5802, July 2010.
+
+ [SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email
+ Filtering Language", RFC 5228, January 2008.
+
+ [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
+ Security (TLS) Protocol Version 1.2", RFC 5246, August
+ 2008.
+
+ [URI-GEN] Berners-Lee, T., Fielding, R., and L. Masinter,
+ "Uniform Resource Identifier (URI): Generic Syntax",
+ STD 66, RFC 3986, January 2005.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
+ Housley, R., and W. Polk, "Internet X.509 Public Key
+ Infrastructure Certificate and Certificate Revocation
+ List (CRL) Profile", RFC 5280, May 2008.
+
+ [X509-SRV] Santesson, S., "Internet X.509 Public Key
+ Infrastructure Subject Alternative Name for Expression
+ of Service Name", RFC 4985, August 2007.
+
+9.2. Informative References
+
+ [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication
+ as a SASL Mechanism", RFC 2831, May 2000.
+
+ [GSSAPI] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
+ Authentication and Security Layer (SASL) Mechanism",
+ RFC 4752, November 2006.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 48]
+
+RFC 5804 ManageSieve July 2010
+
+
+ [I-HAVE] Freed, N., "Sieve Email Filtering: Ihave Extension",
+ RFC 5463, March 2009.
+
+ [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [LDAP] Zeilenga, K., "Lightweight Directory Access Protocol
+ (LDAP): Technical Specification Road Map", RFC 4510,
+ June 2006.
+
+ [PLAIN] Zeilenga, K., "The PLAIN Simple Authentication and
+ Security Layer (SASL) Mechanism", RFC 4616, August
+ 2006.
+
+Authors' Addresses
+
+ Alexey Melnikov (editor)
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Tim Martin
+ BeThereBeSquare, Inc.
+ 672 Haight st.
+ San Francisco, CA 94117
+ USA
+
+ Phone: +1 510 260-4175
+ EMail: timmartin@alumni.cmu.edu
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 49]
+
diff --git a/rfc/rfc822.txt b/rfc/rfc822.txt
@@ -0,0 +1,2901 @@
+
+
+
+
+
+
+ RFC # 822
+
+ Obsoletes: RFC #733 (NIC #41952)
+
+
+
+
+
+
+
+
+
+
+
+
+ STANDARD FOR THE FORMAT OF
+
+ ARPA INTERNET TEXT MESSAGES
+
+
+
+
+
+
+ August 13, 1982
+
+
+
+
+
+
+ Revised by
+
+ David H. Crocker
+
+
+ Dept. of Electrical Engineering
+ University of Delaware, Newark, DE 19711
+ Network: DCrocker @ UDel-Relay
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ TABLE OF CONTENTS
+
+
+ PREFACE .................................................... ii
+
+ 1. INTRODUCTION ........................................... 1
+
+ 1.1. Scope ............................................ 1
+ 1.2. Communication Framework .......................... 2
+
+ 2. NOTATIONAL CONVENTIONS ................................. 3
+
+ 3. LEXICAL ANALYSIS OF MESSAGES ........................... 5
+
+ 3.1. General Description .............................. 5
+ 3.2. Header Field Definitions ......................... 9
+ 3.3. Lexical Tokens ................................... 10
+ 3.4. Clarifications ................................... 11
+
+ 4. MESSAGE SPECIFICATION .................................. 17
+
+ 4.1. Syntax ........................................... 17
+ 4.2. Forwarding ....................................... 19
+ 4.3. Trace Fields ..................................... 20
+ 4.4. Originator Fields ................................ 21
+ 4.5. Receiver Fields .................................. 23
+ 4.6. Reference Fields ................................. 23
+ 4.7. Other Fields ..................................... 24
+
+ 5. DATE AND TIME SPECIFICATION ............................ 26
+
+ 5.1. Syntax ........................................... 26
+ 5.2. Semantics ........................................ 26
+
+ 6. ADDRESS SPECIFICATION .................................. 27
+
+ 6.1. Syntax ........................................... 27
+ 6.2. Semantics ........................................ 27
+ 6.3. Reserved Address ................................. 33
+
+ 7. BIBLIOGRAPHY ........................................... 34
+
+
+ APPENDIX
+
+ A. EXAMPLES ............................................... 36
+ B. SIMPLE FIELD PARSING ................................... 40
+ C. DIFFERENCES FROM RFC #733 .............................. 41
+ D. ALPHABETICAL LISTING OF SYNTAX RULES ................... 44
+
+
+ August 13, 1982 - i - RFC #822
+
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ PREFACE
+
+
+ By 1977, the Arpanet employed several informal standards for
+ the text messages (mail) sent among its host computers. It was
+ felt necessary to codify these practices and provide for those
+ features that seemed imminent. The result of that effort was
+ Request for Comments (RFC) #733, "Standard for the Format of ARPA
+ Network Text Message", by Crocker, Vittal, Pogran, and Henderson.
+ The specification attempted to avoid major changes in existing
+ software, while permitting several new features.
+
+ This document revises the specifications in RFC #733, in
+ order to serve the needs of the larger and more complex ARPA
+ Internet. Some of RFC #733's features failed to gain adequate
+ acceptance. In order to simplify the standard and the software
+ that follows it, these features have been removed. A different
+ addressing scheme is used, to handle the case of inter-network
+ mail; and the concept of re-transmission has been introduced.
+
+ This specification is intended for use in the ARPA Internet.
+ However, an attempt has been made to free it of any dependence on
+ that environment, so that it can be applied to other network text
+ message systems.
+
+ The specification of RFC #733 took place over the course of
+ one year, using the ARPANET mail environment, itself, to provide
+ an on-going forum for discussing the capabilities to be included.
+ More than twenty individuals, from across the country, partici-
+ pated in the original discussion. The development of this
+ revised specification has, similarly, utilized network mail-based
+ group discussion. Both specification efforts greatly benefited
+ from the comments and ideas of the participants.
+
+ The syntax of the standard, in RFC #733, was originally
+ specified in the Backus-Naur Form (BNF) meta-language. Ken L.
+ Harrenstien, of SRI International, was responsible for re-coding
+ the BNF into an augmented BNF that makes the representation
+ smaller and easier to understand.
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - ii - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 1. INTRODUCTION
+
+ 1.1. SCOPE
+
+ This standard specifies a syntax for text messages that are
+ sent among computer users, within the framework of "electronic
+ mail". The standard supersedes the one specified in ARPANET
+ Request for Comments #733, "Standard for the Format of ARPA Net-
+ work Text Messages".
+
+ In this context, messages are viewed as having an envelope
+ and contents. The envelope contains whatever information is
+ needed to accomplish transmission and delivery. The contents
+ compose the object to be delivered to the recipient. This stan-
+ dard applies only to the format and some of the semantics of mes-
+ sage contents. It contains no specification of the information
+ in the envelope.
+
+ However, some message systems may use information from the
+ contents to create the envelope. It is intended that this stan-
+ dard facilitate the acquisition of such information by programs.
+
+ Some message systems may store messages in formats that
+ differ from the one specified in this standard. This specifica-
+ tion is intended strictly as a definition of what message content
+ format is to be passed BETWEEN hosts.
+
+ Note: This standard is NOT intended to dictate the internal for-
+ mats used by sites, the specific message system features
+ that they are expected to support, or any of the charac-
+ teristics of user interface programs that create or read
+ messages.
+
+ A distinction should be made between what the specification
+ REQUIRES and what it ALLOWS. Messages can be made complex and
+ rich with formally-structured components of information or can be
+ kept small and simple, with a minimum of such information. Also,
+ the standard simplifies the interpretation of differing visual
+ formats in messages; only the visual aspect of a message is
+ affected and not the interpretation of information within it.
+ Implementors may choose to retain such visual distinctions.
+
+ The formal definition is divided into four levels. The bot-
+ tom level describes the meta-notation used in this document. The
+ second level describes basic lexical analyzers that feed tokens
+ to higher-level parsers. Next is an overall specification for
+ messages; it permits distinguishing individual fields. Finally,
+ there is definition of the contents of several structured fields.
+
+
+
+ August 13, 1982 - 1 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 1.2. COMMUNICATION FRAMEWORK
+
+ Messages consist of lines of text. No special provisions
+ are made for encoding drawings, facsimile, speech, or structured
+ text. No significant consideration has been given to questions
+ of data compression or to transmission and storage efficiency,
+ and the standard tends to be free with the number of bits con-
+ sumed. For example, field names are specified as free text,
+ rather than special terse codes.
+
+ A general "memo" framework is used. That is, a message con-
+ sists of some information in a rigid format, followed by the main
+ part of the message, with a format that is not specified in this
+ document. The syntax of several fields of the rigidly-formated
+ ("headers") section is defined in this specification; some of
+ these fields must be included in all messages.
+
+ The syntax that distinguishes between header fields is
+ specified separately from the internal syntax for particular
+ fields. This separation is intended to allow simple parsers to
+ operate on the general structure of messages, without concern for
+ the detailed structure of individual header fields. Appendix B
+ is provided to facilitate construction of these parsers.
+
+ In addition to the fields specified in this document, it is
+ expected that other fields will gain common use. As necessary,
+ the specifications for these "extension-fields" will be published
+ through the same mechanism used to publish this document. Users
+ may also wish to extend the set of fields that they use
+ privately. Such "user-defined fields" are permitted.
+
+ The framework severely constrains document tone and appear-
+ ance and is primarily useful for most intra-organization communi-
+ cations and well-structured inter-organization communication.
+ It also can be used for some types of inter-process communica-
+ tion, such as simple file transfer and remote job entry. A more
+ robust framework might allow for multi-font, multi-color, multi-
+ dimension encoding of information. A less robust one, as is
+ present in most single-machine message systems, would more
+ severely constrain the ability to add fields and the decision to
+ include specific fields. In contrast with paper-based communica-
+ tion, it is interesting to note that the RECEIVER of a message
+ can exercise an extraordinary amount of control over the
+ message's appearance. The amount of actual control available to
+ message receivers is contingent upon the capabilities of their
+ individual message systems.
+
+
+
+
+
+ August 13, 1982 - 2 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 2. NOTATIONAL CONVENTIONS
+
+ This specification uses an augmented Backus-Naur Form (BNF)
+ notation. The differences from standard BNF involve naming rules
+ and indicating repetition and "local" alternatives.
+
+ 2.1. RULE NAMING
+
+ Angle brackets ("<", ">") are not used, in general. The
+ name of a rule is simply the name itself, rather than "<name>".
+ Quotation-marks enclose literal text (which may be upper and/or
+ lower case). Certain basic rules are in uppercase, such as
+ SPACE, TAB, CRLF, DIGIT, ALPHA, etc. Angle brackets are used in
+ rule definitions, and in the rest of this document, whenever
+ their presence will facilitate discerning the use of rule names.
+
+ 2.2. RULE1 / RULE2: ALTERNATIVES
+
+ Elements separated by slash ("/") are alternatives. There-
+ fore "foo / bar" will accept foo or bar.
+
+ 2.3. (RULE1 RULE2): LOCAL ALTERNATIVES
+
+ Elements enclosed in parentheses are treated as a single
+ element. Thus, "(elem (foo / bar) elem)" allows the token
+ sequences "elem foo elem" and "elem bar elem".
+
+ 2.4. *RULE: REPETITION
+
+ The character "*" preceding an element indicates repetition.
+ The full form is:
+
+ <l>*<m>element
+
+ indicating at least <l> and at most <m> occurrences of element.
+ Default values are 0 and infinity so that "*(element)" allows any
+ number, including zero; "1*element" requires at least one; and
+ "1*2element" allows one or two.
+
+ 2.5. [RULE]: OPTIONAL
+
+ Square brackets enclose optional elements; "[foo bar]" is
+ equivalent to "*1(foo bar)".
+
+ 2.6. NRULE: SPECIFIC REPETITION
+
+ "<n>(element)" is equivalent to "<n>*<n>(element)"; that is,
+ exactly <n> occurrences of (element). Thus 2DIGIT is a 2-digit
+ number, and 3ALPHA is a string of three alphabetic characters.
+
+
+ August 13, 1982 - 3 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 2.7. #RULE: LISTS
+
+ A construct "#" is defined, similar to "*", as follows:
+
+ <l>#<m>element
+
+ indicating at least <l> and at most <m> elements, each separated
+ by one or more commas (","). This makes the usual form of lists
+ very easy; a rule such as '(element *("," element))' can be shown
+ as "1#element". Wherever this construct is used, null elements
+ are allowed, but do not contribute to the count of elements
+ present. That is, "(element),,(element)" is permitted, but
+ counts as only two elements. Therefore, where at least one ele-
+ ment is required, at least one non-null element must be present.
+ Default values are 0 and infinity so that "#(element)" allows any
+ number, including zero; "1#element" requires at least one; and
+ "1#2element" allows one or two.
+
+ 2.8. ; COMMENTS
+
+ A semi-colon, set off some distance to the right of rule
+ text, starts a comment that continues to the end of line. This
+ is a simple way of including useful notes in parallel with the
+ specifications.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 4 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 3. LEXICAL ANALYSIS OF MESSAGES
+
+ 3.1. GENERAL DESCRIPTION
+
+ A message consists of header fields and, optionally, a body.
+ The body is simply a sequence of lines containing ASCII charac-
+ ters. It is separated from the headers by a null line (i.e., a
+ line with nothing preceding the CRLF).
+
+ 3.1.1. LONG HEADER FIELDS
+
+ Each header field can be viewed as a single, logical line of
+ ASCII characters, comprising a field-name and a field-body.
+ For convenience, the field-body portion of this conceptual
+ entity can be split into a multiple-line representation; this
+ is called "folding". The general rule is that wherever there
+ may be linear-white-space (NOT simply LWSP-chars), a CRLF
+ immediately followed by AT LEAST one LWSP-char may instead be
+ inserted. Thus, the single line
+
+ To: "Joe & J. Harvey" <ddd @Org>, JJV @ BBN
+
+ can be represented as:
+
+ To: "Joe & J. Harvey" <ddd @ Org>,
+ JJV@BBN
+
+ and
+
+ To: "Joe & J. Harvey"
+ <ddd@ Org>, JJV
+ @BBN
+
+ and
+
+ To: "Joe &
+ J. Harvey" <ddd @ Org>, JJV @ BBN
+
+ The process of moving from this folded multiple-line
+ representation of a header field to its single line represen-
+ tation is called "unfolding". Unfolding is accomplished by
+ regarding CRLF immediately followed by a LWSP-char as
+ equivalent to the LWSP-char.
+
+ Note: While the standard permits folding wherever linear-
+ white-space is permitted, it is recommended that struc-
+ tured fields, such as those containing addresses, limit
+ folding to higher-level syntactic breaks. For address
+ fields, it is recommended that such folding occur
+
+
+ August 13, 1982 - 5 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ between addresses, after the separating comma.
+
+ 3.1.2. STRUCTURE OF HEADER FIELDS
+
+ Once a field has been unfolded, it may be viewed as being com-
+ posed of a field-name followed by a colon (":"), followed by a
+ field-body, and terminated by a carriage-return/line-feed.
+ The field-name must be composed of printable ASCII characters
+ (i.e., characters that have values between 33. and 126.,
+ decimal, except colon). The field-body may be composed of any
+ ASCII characters, except CR or LF. (While CR and/or LF may be
+ present in the actual text, they are removed by the action of
+ unfolding the field.)
+
+ Certain field-bodies of headers may be interpreted according
+ to an internal syntax that some systems may wish to parse.
+ These fields are called "structured fields". Examples
+ include fields containing dates and addresses. Other fields,
+ such as "Subject" and "Comments", are regarded simply as
+ strings of text.
+
+ Note: Any field which has a field-body that is defined as
+ other than simply <text> is to be treated as a struc-
+ tured field.
+
+ Field-names, unstructured field bodies and structured
+ field bodies each are scanned by their own, independent
+ "lexical" analyzers.
+
+ 3.1.3. UNSTRUCTURED FIELD BODIES
+
+ For some fields, such as "Subject" and "Comments", no struc-
+ turing is assumed, and they are treated simply as <text>s, as
+ in the message body. Rules of folding apply to these fields,
+ so that such field bodies which occupy several lines must
+ therefore have the second and successive lines indented by at
+ least one LWSP-char.
+
+ 3.1.4. STRUCTURED FIELD BODIES
+
+ To aid in the creation and reading of structured fields, the
+ free insertion of linear-white-space (which permits folding
+ by inclusion of CRLFs) is allowed between lexical tokens.
+ Rather than obscuring the syntax specifications for these
+ structured fields with explicit syntax for this linear-white-
+ space, the existence of another "lexical" analyzer is assumed.
+ This analyzer does not apply for unstructured field bodies
+ that are simply strings of text, as described above. The
+ analyzer provides an interpretation of the unfolded text
+
+
+ August 13, 1982 - 6 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ composing the body of the field as a sequence of lexical sym-
+ bols.
+
+ These symbols are:
+
+ - individual special characters
+ - quoted-strings
+ - domain-literals
+ - comments
+ - atoms
+
+ The first four of these symbols are self-delimiting. Atoms
+ are not; they are delimited by the self-delimiting symbols and
+ by linear-white-space. For the purposes of regenerating
+ sequences of atoms and quoted-strings, exactly one SPACE is
+ assumed to exist, and should be used, between them. (Also, in
+ the "Clarifications" section on "White Space", below, note the
+ rules about treatment of multiple contiguous LWSP-chars.)
+
+ So, for example, the folded body of an address field
+
+ ":sysmail"@ Some-Group. Some-Org,
+ Muhammed.(I am the greatest) Ali @(the)Vegas.WBA
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 7 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ is analyzed into the following lexical symbols and types:
+
+ :sysmail quoted string
+ @ special
+ Some-Group atom
+ . special
+ Some-Org atom
+ , special
+ Muhammed atom
+ . special
+ (I am the greatest) comment
+ Ali atom
+ @ atom
+ (the) comment
+ Vegas atom
+ . special
+ WBA atom
+
+ The canonical representations for the data in these addresses
+ are the following strings:
+
+ ":sysmail"@Some-Group.Some-Org
+
+ and
+
+ Muhammed.Ali@Vegas.WBA
+
+ Note: For purposes of display, and when passing such struc-
+ tured information to other systems, such as mail proto-
+ col services, there must be NO linear-white-space
+ between <word>s that are separated by period (".") or
+ at-sign ("@") and exactly one SPACE between all other
+ <word>s. Also, headers should be in a folded form.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 8 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 3.2. HEADER FIELD DEFINITIONS
+
+ These rules show a field meta-syntax, without regard for the
+ particular type or internal syntax. Their purpose is to permit
+ detection of fields; also, they present to higher-level parsers
+ an image of each field as fitting on one line.
+
+ field = field-name ":" [ field-body ] CRLF
+
+ field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
+
+ field-body = field-body-contents
+ [CRLF LWSP-char field-body]
+
+ field-body-contents =
+ <the ASCII characters making up the field-body, as
+ defined in the following sections, and consisting
+ of combinations of atom, quoted-string, and
+ specials tokens, or else consisting of texts>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 9 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 3.3. LEXICAL TOKENS
+
+ The following rules are used to define an underlying lexical
+ analyzer, which feeds tokens to higher level parsers. See the
+ ANSI references, in the Bibliography.
+
+ ; ( Octal, Decimal.)
+ CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
+ ALPHA = <any ASCII alphabetic character>
+ ; (101-132, 65.- 90.)
+ ; (141-172, 97.-122.)
+ DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.)
+ CTL = <any ASCII control ; ( 0- 37, 0.- 31.)
+ character and DEL> ; ( 177, 127.)
+ CR = <ASCII CR, carriage return> ; ( 15, 13.)
+ LF = <ASCII LF, linefeed> ; ( 12, 10.)
+ SPACE = <ASCII SP, space> ; ( 40, 32.)
+ HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.)
+ <"> = <ASCII quote mark> ; ( 42, 34.)
+ CRLF = CR LF
+
+ LWSP-char = SPACE / HTAB ; semantics = SPACE
+
+ linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE
+ ; CRLF => folding
+
+ specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-
+ / "," / ";" / ":" / "\" / <"> ; string, to use
+ / "." / "[" / "]" ; within a word.
+
+ delimiters = specials / linear-white-space / comment
+
+ text = <any CHAR, including bare ; => atoms, specials,
+ CR & bare LF, but NOT ; comments and
+ including CRLF> ; quoted-strings are
+ ; NOT recognized.
+
+ atom = 1*<any CHAR except specials, SPACE and CTLs>
+
+ quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
+ ; quoted chars.
+
+ qtext = <any CHAR excepting <">, ; => may be folded
+ "\" & CR, and including
+ linear-white-space>
+
+ domain-literal = "[" *(dtext / quoted-pair) "]"
+
+
+
+
+ August 13, 1982 - 10 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ dtext = <any CHAR excluding "[", ; => may be folded
+ "]", "\" & CR, & including
+ linear-white-space>
+
+ comment = "(" *(ctext / quoted-pair / comment) ")"
+
+ ctext = <any CHAR excluding "(", ; => may be folded
+ ")", "\" & CR, & including
+ linear-white-space>
+
+ quoted-pair = "\" CHAR ; may quote any char
+
+ phrase = 1*word ; Sequence of words
+
+ word = atom / quoted-string
+
+
+ 3.4. CLARIFICATIONS
+
+ 3.4.1. QUOTING
+
+ Some characters are reserved for special interpretation, such
+ as delimiting lexical tokens. To permit use of these charac-
+ ters as uninterpreted data, a quoting mechanism is provided.
+ To quote a character, precede it with a backslash ("\").
+
+ This mechanism is not fully general. Characters may be quoted
+ only within a subset of the lexical constructs. In particu-
+ lar, quoting is limited to use within:
+
+ - quoted-string
+ - domain-literal
+ - comment
+
+ Within these constructs, quoting is REQUIRED for CR and "\"
+ and for the character(s) that delimit the token (e.g., "(" and
+ ")" for a comment). However, quoting is PERMITTED for any
+ character.
+
+ Note: In particular, quoting is NOT permitted within atoms.
+ For example when the local-part of an addr-spec must
+ contain a special character, a quoted string must be
+ used. Therefore, a specification such as:
+
+ Full\ Name@Domain
+
+ is not legal and must be specified as:
+
+ "Full Name"@Domain
+
+
+ August 13, 1982 - 11 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 3.4.2. WHITE SPACE
+
+ Note: In structured field bodies, multiple linear space ASCII
+ characters (namely HTABs and SPACEs) are treated as
+ single spaces and may freely surround any symbol. In
+ all header fields, the only place in which at least one
+ LWSP-char is REQUIRED is at the beginning of continua-
+ tion lines in a folded field.
+
+ When passing text to processes that do not interpret text
+ according to this standard (e.g., mail protocol servers), then
+ NO linear-white-space characters should occur between a period
+ (".") or at-sign ("@") and a <word>. Exactly ONE SPACE should
+ be used in place of arbitrary linear-white-space and comment
+ sequences.
+
+ Note: Within systems conforming to this standard, wherever a
+ member of the list of delimiters is allowed, LWSP-chars
+ may also occur before and/or after it.
+
+ Writers of mail-sending (i.e., header-generating) programs
+ should realize that there is no network-wide definition of the
+ effect of ASCII HT (horizontal-tab) characters on the appear-
+ ance of text at another network host; therefore, the use of
+ tabs in message headers, though permitted, is discouraged.
+
+ 3.4.3. COMMENTS
+
+ A comment is a set of ASCII characters, which is enclosed in
+ matching parentheses and which is not within a quoted-string
+ The comment construct permits message originators to add text
+ which will be useful for human readers, but which will be
+ ignored by the formal semantics. Comments should be retained
+ while the message is subject to interpretation according to
+ this standard. However, comments must NOT be included in
+ other cases, such as during protocol exchanges with mail
+ servers.
+
+ Comments nest, so that if an unquoted left parenthesis occurs
+ in a comment string, there must also be a matching right
+ parenthesis. When a comment acts as the delimiter between a
+ sequence of two lexical symbols, such as two atoms, it is lex-
+ ically equivalent with a single SPACE, for the purposes of
+ regenerating the sequence, such as when passing the sequence
+ onto a mail protocol server. Comments are detected as such
+ only within field-bodies of structured fields.
+
+ If a comment is to be "folded" onto multiple lines, then the
+ syntax for folding must be adhered to. (See the "Lexical
+
+
+ August 13, 1982 - 12 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ Analysis of Messages" section on "Folding Long Header Fields"
+ above, and the section on "Case Independence" below.) Note
+ that the official semantics therefore do not "see" any
+ unquoted CRLFs that are in comments, although particular pars-
+ ing programs may wish to note their presence. For these pro-
+ grams, it would be reasonable to interpret a "CRLF LWSP-char"
+ as being a CRLF that is part of the comment; i.e., the CRLF is
+ kept and the LWSP-char is discarded. Quoted CRLFs (i.e., a
+ backslash followed by a CR followed by a LF) still must be
+ followed by at least one LWSP-char.
+
+ 3.4.4. DELIMITING AND QUOTING CHARACTERS
+
+ The quote character (backslash) and characters that delimit
+ syntactic units are not, generally, to be taken as data that
+ are part of the delimited or quoted unit(s). In particular,
+ the quotation-marks that define a quoted-string, the
+ parentheses that define a comment and the backslash that
+ quotes a following character are NOT part of the quoted-
+ string, comment or quoted character. A quotation-mark that is
+ to be part of a quoted-string, a parenthesis that is to be
+ part of a comment and a backslash that is to be part of either
+ must each be preceded by the quote-character backslash ("\").
+ Note that the syntax allows any character to be quoted within
+ a quoted-string or comment; however only certain characters
+ MUST be quoted to be included as data. These characters are
+ the ones that are not part of the alternate text group (i.e.,
+ ctext or qtext).
+
+ The one exception to this rule is that a single SPACE is
+ assumed to exist between contiguous words in a phrase, and
+ this interpretation is independent of the actual number of
+ LWSP-chars that the creator places between the words. To
+ include more than one SPACE, the creator must make the LWSP-
+ chars be part of a quoted-string.
+
+ Quotation marks that delimit a quoted string and backslashes
+ that quote the following character should NOT accompany the
+ quoted-string when the string is passed to processes that do
+ not interpret data according to this specification (e.g., mail
+ protocol servers).
+
+ 3.4.5. QUOTED-STRINGS
+
+ Where permitted (i.e., in words in structured fields) quoted-
+ strings are treated as a single symbol. That is, a quoted-
+ string is equivalent to an atom, syntactically. If a quoted-
+ string is to be "folded" onto multiple lines, then the syntax
+ for folding must be adhered to. (See the "Lexical Analysis of
+
+
+ August 13, 1982 - 13 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ Messages" section on "Folding Long Header Fields" above, and
+ the section on "Case Independence" below.) Therefore, the
+ official semantics do not "see" any bare CRLFs that are in
+ quoted-strings; however particular parsing programs may wish
+ to note their presence. For such programs, it would be rea-
+ sonable to interpret a "CRLF LWSP-char" as being a CRLF which
+ is part of the quoted-string; i.e., the CRLF is kept and the
+ LWSP-char is discarded. Quoted CRLFs (i.e., a backslash fol-
+ lowed by a CR followed by a LF) are also subject to rules of
+ folding, but the presence of the quoting character (backslash)
+ explicitly indicates that the CRLF is data to the quoted
+ string. Stripping off the first following LWSP-char is also
+ appropriate when parsing quoted CRLFs.
+
+ 3.4.6. BRACKETING CHARACTERS
+
+ There is one type of bracket which must occur in matched pairs
+ and may have pairs nested within each other:
+
+ o Parentheses ("(" and ")") are used to indicate com-
+ ments.
+
+ There are three types of brackets which must occur in matched
+ pairs, and which may NOT be nested:
+
+ o Colon/semi-colon (":" and ";") are used in address
+ specifications to indicate that the included list of
+ addresses are to be treated as a group.
+
+ o Angle brackets ("<" and ">") are generally used to
+ indicate the presence of a one machine-usable refer-
+ ence (e.g., delimiting mailboxes), possibly including
+ source-routing to the machine.
+
+ o Square brackets ("[" and "]") are used to indicate the
+ presence of a domain-literal, which the appropriate
+ name-domain is to use directly, bypassing normal
+ name-resolution mechanisms.
+
+ 3.4.7. CASE INDEPENDENCE
+
+ Except as noted, alphabetic strings may be represented in any
+ combination of upper and lower case. The only syntactic units
+
+
+
+
+
+
+
+
+ August 13, 1982 - 14 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ which requires preservation of case information are:
+
+ - text
+ - qtext
+ - dtext
+ - ctext
+ - quoted-pair
+ - local-part, except "Postmaster"
+
+ When matching any other syntactic unit, case is to be ignored.
+ For example, the field-names "From", "FROM", "from", and even
+ "FroM" are semantically equal and should all be treated ident-
+ ically.
+
+ When generating these units, any mix of upper and lower case
+ alphabetic characters may be used. The case shown in this
+ specification is suggested for message-creating processes.
+
+ Note: The reserved local-part address unit, "Postmaster", is
+ an exception. When the value "Postmaster" is being
+ interpreted, it must be accepted in any mixture of
+ case, including "POSTMASTER", and "postmaster".
+
+ 3.4.8. FOLDING LONG HEADER FIELDS
+
+ Each header field may be represented on exactly one line con-
+ sisting of the name of the field and its body, and terminated
+ by a CRLF; this is what the parser sees. For readability, the
+ field-body portion of long header fields may be "folded" onto
+ multiple lines of the actual field. "Long" is commonly inter-
+ preted to mean greater than 65 or 72 characters. The former
+ length serves as a limit, when the message is to be viewed on
+ most simple terminals which use simple display software; how-
+ ever, the limit is not imposed by this standard.
+
+ Note: Some display software often can selectively fold lines,
+ to suit the display terminal. In such cases, sender-
+ provided folding can interfere with the display
+ software.
+
+ 3.4.9. BACKSPACE CHARACTERS
+
+ ASCII BS characters (Backspace, decimal 8) may be included in
+ texts and quoted-strings to effect overstriking. However, any
+ use of backspaces which effects an overstrike to the left of
+ the beginning of the text or quoted-string is prohibited.
+
+
+
+
+
+ August 13, 1982 - 15 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 3.4.10. NETWORK-SPECIFIC TRANSFORMATIONS
+
+ During transmission through heterogeneous networks, it may be
+ necessary to force data to conform to a network's local con-
+ ventions. For example, it may be required that a CR be fol-
+ lowed either by LF, making a CRLF, or by <null>, if the CR is
+ to stand alone). Such transformations are reversed, when the
+ message exits that network.
+
+ When crossing network boundaries, the message should be
+ treated as passing through two modules. It will enter the
+ first module containing whatever network-specific transforma-
+ tions that were necessary to permit migration through the
+ "current" network. It then passes through the modules:
+
+ o Transformation Reversal
+
+ The "current" network's idiosyncracies are removed and
+ the message is returned to the canonical form speci-
+ fied in this standard.
+
+ o Transformation
+
+ The "next" network's local idiosyncracies are imposed
+ on the message.
+
+ ------------------
+ From ==> | Remove Net-A |
+ Net-A | idiosyncracies |
+ ------------------
+ ||
+ \/
+ Conformance
+ with standard
+ ||
+ \/
+ ------------------
+ | Impose Net-B | ==> To
+ | idiosyncracies | Net-B
+ ------------------
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 16 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 4. MESSAGE SPECIFICATION
+
+ 4.1. SYNTAX
+
+ Note: Due to an artifact of the notational conventions, the syn-
+ tax indicates that, when present, some fields, must be in
+ a particular order. Header fields are NOT required to
+ occur in any particular order, except that the message
+ body must occur AFTER the headers. It is recommended
+ that, if present, headers be sent in the order "Return-
+ Path", "Received", "Date", "From", "Subject", "Sender",
+ "To", "cc", etc.
+
+ This specification permits multiple occurrences of most
+ fields. Except as noted, their interpretation is not
+ specified here, and their use is discouraged.
+
+ The following syntax for the bodies of various fields should
+ be thought of as describing each field body as a single long
+ string (or line). The "Lexical Analysis of Message" section on
+ "Long Header Fields", above, indicates how such long strings can
+ be represented on more than one line in the actual transmitted
+ message.
+
+ message = fields *( CRLF *text ) ; Everything after
+ ; first null line
+ ; is message body
+
+ fields = dates ; Creation time,
+ source ; author id & one
+ 1*destination ; address required
+ *optional-field ; others optional
+
+ source = [ trace ] ; net traversals
+ originator ; original mail
+ [ resent ] ; forwarded
+
+ trace = return ; path to sender
+ 1*received ; receipt tags
+
+ return = "Return-path" ":" route-addr ; return address
+
+ received = "Received" ":" ; one per relay
+ ["from" domain] ; sending host
+ ["by" domain] ; receiving host
+ ["via" atom] ; physical path
+ *("with" atom) ; link/mail protocol
+ ["id" msg-id] ; receiver msg id
+ ["for" addr-spec] ; initial form
+
+
+ August 13, 1982 - 17 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ ";" date-time ; time received
+
+ originator = authentic ; authenticated addr
+ [ "Reply-To" ":" 1#address] )
+
+ authentic = "From" ":" mailbox ; Single author
+ / ( "Sender" ":" mailbox ; Actual submittor
+ "From" ":" 1#mailbox) ; Multiple authors
+ ; or not sender
+
+ resent = resent-authentic
+ [ "Resent-Reply-To" ":" 1#address] )
+
+ resent-authentic =
+ = "Resent-From" ":" mailbox
+ / ( "Resent-Sender" ":" mailbox
+ "Resent-From" ":" 1#mailbox )
+
+ dates = orig-date ; Original
+ [ resent-date ] ; Forwarded
+
+ orig-date = "Date" ":" date-time
+
+ resent-date = "Resent-Date" ":" date-time
+
+ destination = "To" ":" 1#address ; Primary
+ / "Resent-To" ":" 1#address
+ / "cc" ":" 1#address ; Secondary
+ / "Resent-cc" ":" 1#address
+ / "bcc" ":" #address ; Blind carbon
+ / "Resent-bcc" ":" #address
+
+ optional-field =
+ / "Message-ID" ":" msg-id
+ / "Resent-Message-ID" ":" msg-id
+ / "In-Reply-To" ":" *(phrase / msg-id)
+ / "References" ":" *(phrase / msg-id)
+ / "Keywords" ":" #phrase
+ / "Subject" ":" *text
+ / "Comments" ":" *text
+ / "Encrypted" ":" 1#2word
+ / extension-field ; To be defined
+ / user-defined-field ; May be pre-empted
+
+ msg-id = "<" addr-spec ">" ; Unique message id
+
+
+
+
+
+
+ August 13, 1982 - 18 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ extension-field =
+ <Any field which is defined in a document
+ published as a formal extension to this
+ specification; none will have names beginning
+ with the string "X-">
+
+ user-defined-field =
+ <Any field which has not been defined
+ in this specification or published as an
+ extension to this specification; names for
+ such fields must be unique and may be
+ pre-empted by published extensions>
+
+ 4.2. FORWARDING
+
+ Some systems permit mail recipients to forward a message,
+ retaining the original headers, by adding some new fields. This
+ standard supports such a service, through the "Resent-" prefix to
+ field names.
+
+ Whenever the string "Resent-" begins a field name, the field
+ has the same semantics as a field whose name does not have the
+ prefix. However, the message is assumed to have been forwarded
+ by an original recipient who attached the "Resent-" field. This
+ new field is treated as being more recent than the equivalent,
+ original field. For example, the "Resent-From", indicates the
+ person that forwarded the message, whereas the "From" field indi-
+ cates the original author.
+
+ Use of such precedence information depends upon partici-
+ pants' communication needs. For example, this standard does not
+ dictate when a "Resent-From:" address should receive replies, in
+ lieu of sending them to the "From:" address.
+
+ Note: In general, the "Resent-" fields should be treated as con-
+ taining a set of information that is independent of the
+ set of original fields. Information for one set should
+ not automatically be taken from the other. The interpre-
+ tation of multiple "Resent-" fields, of the same type, is
+ undefined.
+
+ In the remainder of this specification, occurrence of legal
+ "Resent-" fields are treated identically with the occurrence of
+
+
+
+
+
+
+
+
+ August 13, 1982 - 19 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ fields whose names do not contain this prefix.
+
+ 4.3. TRACE FIELDS
+
+ Trace information is used to provide an audit trail of mes-
+ sage handling. In addition, it indicates a route back to the
+ sender of the message.
+
+ The list of known "via" and "with" values are registered
+ with the Network Information Center, SRI International, Menlo
+ Park, California.
+
+ 4.3.1. RETURN-PATH
+
+ This field is added by the final transport system that
+ delivers the message to its recipient. The field is intended
+ to contain definitive information about the address and route
+ back to the message's originator.
+
+ Note: The "Reply-To" field is added by the originator and
+ serves to direct replies, whereas the "Return-Path"
+ field is used to identify a path back to the origina-
+ tor.
+
+ While the syntax indicates that a route specification is
+ optional, every attempt should be made to provide that infor-
+ mation in this field.
+
+ 4.3.2. RECEIVED
+
+ A copy of this field is added by each transport service that
+ relays the message. The information in the field can be quite
+ useful for tracing transport problems.
+
+ The names of the sending and receiving hosts and time-of-
+ receipt may be specified. The "via" parameter may be used, to
+ indicate what physical mechanism the message was sent over,
+ such as Arpanet or Phonenet, and the "with" parameter may be
+ used to indicate the mail-, or connection-, level protocol
+ that was used, such as the SMTP mail protocol, or X.25 tran-
+ sport protocol.
+
+ Note: Several "with" parameters may be included, to fully
+ specify the set of protocols that were used.
+
+ Some transport services queue mail; the internal message iden-
+ tifier that is assigned to the message may be noted, using the
+ "id" parameter. When the sending host uses a destination
+ address specification that the receiving host reinterprets, by
+
+
+ August 13, 1982 - 20 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ expansion or transformation, the receiving host may wish to
+ record the original specification, using the "for" parameter.
+ For example, when a copy of mail is sent to the member of a
+ distribution list, this parameter may be used to record the
+ original address that was used to specify the list.
+
+ 4.4. ORIGINATOR FIELDS
+
+ The standard allows only a subset of the combinations possi-
+ ble with the From, Sender, Reply-To, Resent-From, Resent-Sender,
+ and Resent-Reply-To fields. The limitation is intentional.
+
+ 4.4.1. FROM / RESENT-FROM
+
+ This field contains the identity of the person(s) who wished
+ this message to be sent. The message-creation process should
+ default this field to be a single, authenticated machine
+ address, indicating the AGENT (person, system or process)
+ entering the message. If this is not done, the "Sender" field
+ MUST be present. If the "From" field IS defaulted this way,
+ the "Sender" field is optional and is redundant with the
+ "From" field. In all cases, addresses in the "From" field
+ must be machine-usable (addr-specs) and may not contain named
+ lists (groups).
+
+ 4.4.2. SENDER / RESENT-SENDER
+
+ This field contains the authenticated identity of the AGENT
+ (person, system or process) that sends the message. It is
+ intended for use when the sender is not the author of the mes-
+ sage, or to indicate who among a group of authors actually
+ sent the message. If the contents of the "Sender" field would
+ be completely redundant with the "From" field, then the
+ "Sender" field need not be present and its use is discouraged
+ (though still legal). In particular, the "Sender" field MUST
+ be present if it is NOT the same as the "From" Field.
+
+ The Sender mailbox specification includes a word sequence
+ which must correspond to a specific agent (i.e., a human user
+ or a computer program) rather than a standard address. This
+ indicates the expectation that the field will identify the
+ single AGENT (person, system, or process) responsible for
+ sending the mail and not simply include the name of a mailbox
+ from which the mail was sent. For example in the case of a
+ shared login name, the name, by itself, would not be adequate.
+ The local-part address unit, which refers to this agent, is
+ expected to be a computer system term, and not (for example) a
+ generalized person reference which can be used outside the
+ network text message context.
+
+
+ August 13, 1982 - 21 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ Since the critical function served by the "Sender" field is
+ identification of the agent responsible for sending mail and
+ since computer programs cannot be held accountable for their
+ behavior, it is strongly recommended that when a computer pro-
+ gram generates a message, the HUMAN who is responsible for
+ that program be referenced as part of the "Sender" field mail-
+ box specification.
+
+ 4.4.3. REPLY-TO / RESENT-REPLY-TO
+
+ This field provides a general mechanism for indicating any
+ mailbox(es) to which responses are to be sent. Three typical
+ uses for this feature can be distinguished. In the first
+ case, the author(s) may not have regular machine-based mail-
+ boxes and therefore wish(es) to indicate an alternate machine
+ address. In the second case, an author may wish additional
+ persons to be made aware of, or responsible for, replies. A
+ somewhat different use may be of some help to "text message
+ teleconferencing" groups equipped with automatic distribution
+ services: include the address of that service in the "Reply-
+ To" field of all messages submitted to the teleconference;
+ then participants can "reply" to conference submissions to
+ guarantee the correct distribution of any submission of their
+ own.
+
+ Note: The "Return-Path" field is added by the mail transport
+ service, at the time of final deliver. It is intended
+ to identify a path back to the orginator of the mes-
+ sage. The "Reply-To" field is added by the message
+ originator and is intended to direct replies.
+
+ 4.4.4. AUTOMATIC USE OF FROM / SENDER / REPLY-TO
+
+ For systems which automatically generate address lists for
+ replies to messages, the following recommendations are made:
+
+ o The "Sender" field mailbox should be sent notices of
+ any problems in transport or delivery of the original
+ messages. If there is no "Sender" field, then the
+ "From" field mailbox should be used.
+
+ o The "Sender" field mailbox should NEVER be used
+ automatically, in a recipient's reply message.
+
+ o If the "Reply-To" field exists, then the reply should
+ go to the addresses indicated in that field and not to
+ the address(es) indicated in the "From" field.
+
+
+
+
+ August 13, 1982 - 22 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ o If there is a "From" field, but no "Reply-To" field,
+ the reply should be sent to the address(es) indicated
+ in the "From" field.
+
+ Sometimes, a recipient may actually wish to communicate with
+ the person that initiated the message transfer. In such
+ cases, it is reasonable to use the "Sender" address.
+
+ This recommendation is intended only for automated use of
+ originator-fields and is not intended to suggest that replies
+ may not also be sent to other recipients of messages. It is
+ up to the respective mail-handling programs to decide what
+ additional facilities will be provided.
+
+ Examples are provided in Appendix A.
+
+ 4.5. RECEIVER FIELDS
+
+ 4.5.1. TO / RESENT-TO
+
+ This field contains the identity of the primary recipients of
+ the message.
+
+ 4.5.2. CC / RESENT-CC
+
+ This field contains the identity of the secondary (informa-
+ tional) recipients of the message.
+
+ 4.5.3. BCC / RESENT-BCC
+
+ This field contains the identity of additional recipients of
+ the message. The contents of this field are not included in
+ copies of the message sent to the primary and secondary reci-
+ pients. Some systems may choose to include the text of the
+ "Bcc" field only in the author(s)'s copy, while others may
+ also include it in the text sent to all those indicated in the
+ "Bcc" list.
+
+ 4.6. REFERENCE FIELDS
+
+ 4.6.1. MESSAGE-ID / RESENT-MESSAGE-ID
+
+ This field contains a unique identifier (the local-part
+ address unit) which refers to THIS version of THIS message.
+ The uniqueness of the message identifier is guaranteed by the
+ host which generates it. This identifier is intended to be
+ machine readable and not necessarily meaningful to humans. A
+ message identifier pertains to exactly one instantiation of a
+ particular message; subsequent revisions to the message should
+
+
+ August 13, 1982 - 23 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ each receive new message identifiers.
+
+ 4.6.2. IN-REPLY-TO
+
+ The contents of this field identify previous correspon-
+ dence which this message answers. Note that if message iden-
+ tifiers are used in this field, they must use the msg-id
+ specification format.
+
+ 4.6.3. REFERENCES
+
+ The contents of this field identify other correspondence
+ which this message references. Note that if message identif-
+ iers are used, they must use the msg-id specification format.
+
+ 4.6.4. KEYWORDS
+
+ This field contains keywords or phrases, separated by
+ commas.
+
+ 4.7. OTHER FIELDS
+
+ 4.7.1. SUBJECT
+
+ This is intended to provide a summary, or indicate the
+ nature, of the message.
+
+ 4.7.2. COMMENTS
+
+ Permits adding text comments onto the message without
+ disturbing the contents of the message's body.
+
+ 4.7.3. ENCRYPTED
+
+ Sometimes, data encryption is used to increase the
+ privacy of message contents. If the body of a message has
+ been encrypted, to keep its contents private, the "Encrypted"
+ field can be used to note the fact and to indicate the nature
+ of the encryption. The first <word> parameter indicates the
+ software used to encrypt the body, and the second, optional
+ <word> is intended to aid the recipient in selecting the
+ proper decryption key. This code word may be viewed as an
+ index to a table of keys held by the recipient.
+
+ Note: Unfortunately, headers must contain envelope, as well
+ as contents, information. Consequently, it is neces-
+ sary that they remain unencrypted, so that mail tran-
+ sport services may access them. Since names,
+ addresses, and "Subject" field contents may contain
+
+
+ August 13, 1982 - 24 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ sensitive information, this requirement limits total
+ message privacy.
+
+ Names of encryption software are registered with the Net-
+ work Information Center, SRI International, Menlo Park, Cali-
+ fornia.
+
+ 4.7.4. EXTENSION-FIELD
+
+ A limited number of common fields have been defined in
+ this document. As network mail requirements dictate, addi-
+ tional fields may be standardized. To provide user-defined
+ fields with a measure of safety, in name selection, such
+ extension-fields will never have names that begin with the
+ string "X-".
+
+ Names of Extension-fields are registered with the Network
+ Information Center, SRI International, Menlo Park, California.
+
+ 4.7.5. USER-DEFINED-FIELD
+
+ Individual users of network mail are free to define and
+ use additional header fields. Such fields must have names
+ which are not already used in the current specification or in
+ any definitions of extension-fields, and the overall syntax of
+ these user-defined-fields must conform to this specification's
+ rules for delimiting and folding fields. Due to the
+ extension-field publishing process, the name of a user-
+ defined-field may be pre-empted
+
+ Note: The prefatory string "X-" will never be used in the
+ names of Extension-fields. This provides user-defined
+ fields with a protected set of names.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 25 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 5. DATE AND TIME SPECIFICATION
+
+ 5.1. SYNTAX
+
+ date-time = [ day "," ] date time ; dd mm yy
+ ; hh:mm:ss zzz
+
+ day = "Mon" / "Tue" / "Wed" / "Thu"
+ / "Fri" / "Sat" / "Sun"
+
+ date = 1*2DIGIT month 2DIGIT ; day month year
+ ; e.g. 20 Jun 82
+
+ month = "Jan" / "Feb" / "Mar" / "Apr"
+ / "May" / "Jun" / "Jul" / "Aug"
+ / "Sep" / "Oct" / "Nov" / "Dec"
+
+ time = hour zone ; ANSI and Military
+
+ hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT]
+ ; 00:00:00 - 23:59:59
+
+ zone = "UT" / "GMT" ; Universal Time
+ ; North American : UT
+ / "EST" / "EDT" ; Eastern: - 5/ - 4
+ / "CST" / "CDT" ; Central: - 6/ - 5
+ / "MST" / "MDT" ; Mountain: - 7/ - 6
+ / "PST" / "PDT" ; Pacific: - 8/ - 7
+ / 1ALPHA ; Military: Z = UT;
+ ; A:-1; (J not used)
+ ; M:-12; N:+1; Y:+12
+ / ( ("+" / "-") 4DIGIT ) ; Local differential
+ ; hours+min. (HHMM)
+
+ 5.2. SEMANTICS
+
+ If included, day-of-week must be the day implied by the date
+ specification.
+
+ Time zone may be indicated in several ways. "UT" is Univer-
+ sal Time (formerly called "Greenwich Mean Time"); "GMT" is per-
+ mitted as a reference to Universal Time. The military standard
+ uses a single character for each zone. "Z" is Universal Time.
+ "A" indicates one hour earlier, and "M" indicates 12 hours ear-
+ lier; "N" is one hour later, and "Y" is 12 hours later. The
+ letter "J" is not used. The other remaining two forms are taken
+ from ANSI standard X3.51-1975. One allows explicit indication of
+ the amount of offset from UT; the other uses common 3-character
+ strings for indicating time zones in North America.
+
+
+ August 13, 1982 - 26 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 6. ADDRESS SPECIFICATION
+
+ 6.1. SYNTAX
+
+ address = mailbox ; one addressee
+ / group ; named list
+
+ group = phrase ":" [#mailbox] ";"
+
+ mailbox = addr-spec ; simple address
+ / phrase route-addr ; name & addr-spec
+
+ route-addr = "<" [route] addr-spec ">"
+
+ route = 1#("@" domain) ":" ; path-relative
+
+ addr-spec = local-part "@" domain ; global address
+
+ local-part = word *("." word) ; uninterpreted
+ ; case-preserved
+
+ domain = sub-domain *("." sub-domain)
+
+ sub-domain = domain-ref / domain-literal
+
+ domain-ref = atom ; symbolic reference
+
+ 6.2. SEMANTICS
+
+ A mailbox receives mail. It is a conceptual entity which
+ does not necessarily pertain to file storage. For example, some
+ sites may choose to print mail on their line printer and deliver
+ the output to the addressee's desk.
+
+ A mailbox specification comprises a person, system or pro-
+ cess name reference, a domain-dependent string, and a name-domain
+ reference. The name reference is optional and is usually used to
+ indicate the human name of a recipient. The name-domain refer-
+ ence specifies a sequence of sub-domains. The domain-dependent
+ string is uninterpreted, except by the final sub-domain; the rest
+ of the mail service merely transmits it as a literal string.
+
+ 6.2.1. DOMAINS
+
+ A name-domain is a set of registered (mail) names. A name-
+ domain specification resolves to a subordinate name-domain
+ specification or to a terminal domain-dependent string.
+ Hence, domain specification is extensible, permitting any
+ number of registration levels.
+
+
+ August 13, 1982 - 27 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ Name-domains model a global, logical, hierarchical addressing
+ scheme. The model is logical, in that an address specifica-
+ tion is related to name registration and is not necessarily
+ tied to transmission path. The model's hierarchy is a
+ directed graph, called an in-tree, such that there is a single
+ path from the root of the tree to any node in the hierarchy.
+ If more than one path actually exists, they are considered to
+ be different addresses.
+
+ The root node is common to all addresses; consequently, it is
+ not referenced. Its children constitute "top-level" name-
+ domains. Usually, a service has access to its own full domain
+ specification and to the names of all top-level name-domains.
+
+ The "top" of the domain addressing hierarchy -- a child of the
+ root -- is indicated by the right-most field, in a domain
+ specification. Its child is specified to the left, its child
+ to the left, and so on.
+
+ Some groups provide formal registration services; these con-
+ stitute name-domains that are independent logically of
+ specific machines. In addition, networks and machines impli-
+ citly compose name-domains, since their membership usually is
+ registered in name tables.
+
+ In the case of formal registration, an organization implements
+ a (distributed) data base which provides an address-to-route
+ mapping service for addresses of the form:
+
+ person@registry.organization
+
+ Note that "organization" is a logical entity, separate from
+ any particular communication network.
+
+ A mechanism for accessing "organization" is universally avail-
+ able. That mechanism, in turn, seeks an instantiation of the
+ registry; its location is not indicated in the address specif-
+ ication. It is assumed that the system which operates under
+ the name "organization" knows how to find a subordinate regis-
+ try. The registry will then use the "person" string to deter-
+ mine where to send the mail specification.
+
+ The latter, network-oriented case permits simple, direct,
+ attachment-related address specification, such as:
+
+ user@host.network
+
+ Once the network is accessed, it is expected that a message
+ will go directly to the host and that the host will resolve
+
+
+ August 13, 1982 - 28 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ the user name, placing the message in the user's mailbox.
+
+ 6.2.2. ABBREVIATED DOMAIN SPECIFICATION
+
+ Since any number of levels is possible within the domain
+ hierarchy, specification of a fully qualified address can
+ become inconvenient. This standard permits abbreviated domain
+ specification, in a special case:
+
+ For the address of the sender, call the left-most
+ sub-domain Level N. In a header address, if all of
+ the sub-domains above (i.e., to the right of) Level N
+ are the same as those of the sender, then they do not
+ have to appear in the specification. Otherwise, the
+ address must be fully qualified.
+
+ This feature is subject to approval by local sub-
+ domains. Individual sub-domains may require their
+ member systems, which originate mail, to provide full
+ domain specification only. When permitted, abbrevia-
+ tions may be present only while the message stays
+ within the sub-domain of the sender.
+
+ Use of this mechanism requires the sender's sub-domain
+ to reserve the names of all top-level domains, so that
+ full specifications can be distinguished from abbrevi-
+ ated specifications.
+
+ For example, if a sender's address is:
+
+ sender@registry-A.registry-1.organization-X
+
+ and one recipient's address is:
+
+ recipient@registry-B.registry-1.organization-X
+
+ and another's is:
+
+ recipient@registry-C.registry-2.organization-X
+
+ then ".registry-1.organization-X" need not be specified in the
+ the message, but "registry-C.registry-2" DOES have to be
+ specified. That is, the first two addresses may be abbrevi-
+ ated, but the third address must be fully specified.
+
+ When a message crosses a domain boundary, all addresses must
+ be specified in the full format, ending with the top-level
+ name-domain in the right-most field. It is the responsibility
+ of mail forwarding services to ensure that addresses conform
+
+
+ August 13, 1982 - 29 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ with this requirement. In the case of abbreviated addresses,
+ the relaying service must make the necessary expansions. It
+ should be noted that it often is difficult for such a service
+ to locate all occurrences of address abbreviations. For exam-
+ ple, it will not be possible to find such abbreviations within
+ the body of the message. The "Return-Path" field can aid
+ recipients in recovering from these errors.
+
+ Note: When passing any portion of an addr-spec onto a process
+ which does not interpret data according to this stan-
+ dard (e.g., mail protocol servers). There must be NO
+ LWSP-chars preceding or following the at-sign or any
+ delimiting period ("."), such as shown in the above
+ examples, and only ONE SPACE between contiguous
+ <word>s.
+
+ 6.2.3. DOMAIN TERMS
+
+ A domain-ref must be THE official name of a registry, network,
+ or host. It is a symbolic reference, within a name sub-
+ domain. At times, it is necessary to bypass standard mechan-
+ isms for resolving such references, using more primitive
+ information, such as a network host address rather than its
+ associated host name.
+
+ To permit such references, this standard provides the domain-
+ literal construct. Its contents must conform with the needs
+ of the sub-domain in which it is interpreted.
+
+ Domain-literals which refer to domains within the ARPA Inter-
+ net specify 32-bit Internet addresses, in four 8-bit fields
+ noted in decimal, as described in Request for Comments #820,
+ "Assigned Numbers." For example:
+
+ [10.0.3.19]
+
+ Note: THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED. It
+ is permitted only as a means of bypassing temporary
+ system limitations, such as name tables which are not
+ complete.
+
+ The names of "top-level" domains, and the names of domains
+ under in the ARPA Internet, are registered with the Network
+ Information Center, SRI International, Menlo Park, California.
+
+ 6.2.4. DOMAIN-DEPENDENT LOCAL STRING
+
+ The local-part of an addr-spec in a mailbox specification
+ (i.e., the host's name for the mailbox) is understood to be
+
+
+ August 13, 1982 - 30 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ whatever the receiving mail protocol server allows. For exam-
+ ple, some systems do not understand mailbox references of the
+ form "P. D. Q. Bach", but others do.
+
+ This specification treats periods (".") as lexical separators.
+ Hence, their presence in local-parts which are not quoted-
+ strings, is detected. However, such occurrences carry NO
+ semantics. That is, if a local-part has periods within it, an
+ address parser will divide the local-part into several tokens,
+ but the sequence of tokens will be treated as one uninter-
+ preted unit. The sequence will be re-assembled, when the
+ address is passed outside of the system such as to a mail pro-
+ tocol service.
+
+ For example, the address:
+
+ First.Last@Registry.Org
+
+ is legal and does not require the local-part to be surrounded
+ with quotation-marks. (However, "First Last" DOES require
+ quoting.) The local-part of the address, when passed outside
+ of the mail system, within the Registry.Org domain, is
+ "First.Last", again without quotation marks.
+
+ 6.2.5. BALANCING LOCAL-PART AND DOMAIN
+
+ In some cases, the boundary between local-part and domain can
+ be flexible. The local-part may be a simple string, which is
+ used for the final determination of the recipient's mailbox.
+ All other levels of reference are, therefore, part of the
+ domain.
+
+ For some systems, in the case of abbreviated reference to the
+ local and subordinate sub-domains, it may be possible to
+ specify only one reference within the domain part and place
+ the other, subordinate name-domain references within the
+ local-part. This would appear as:
+
+ mailbox.sub1.sub2@this-domain
+
+ Such a specification would be acceptable to address parsers
+ which conform to RFC #733, but do not support this newer
+ Internet standard. While contrary to the intent of this stan-
+ dard, the form is legal.
+
+ Also, some sub-domains have a specification syntax which does
+ not conform to this standard. For example:
+
+ sub-net.mailbox@sub-domain.domain
+
+
+ August 13, 1982 - 31 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ uses a different parsing sequence for local-part than for
+ domain.
+
+ Note: As a rule, the domain specification should contain
+ fields which are encoded according to the syntax of
+ this standard and which contain generally-standardized
+ information. The local-part specification should con-
+ tain only that portion of the address which deviates
+ from the form or intention of the domain field.
+
+ 6.2.6. MULTIPLE MAILBOXES
+
+ An individual may have several mailboxes and wish to receive
+ mail at whatever mailbox is convenient for the sender to
+ access. This standard does not provide a means of specifying
+ "any member of" a list of mailboxes.
+
+ A set of individuals may wish to receive mail as a single unit
+ (i.e., a distribution list). The <group> construct permits
+ specification of such a list. Recipient mailboxes are speci-
+ fied within the bracketed part (":" - ";"). A copy of the
+ transmitted message is to be sent to each mailbox listed.
+ This standard does not permit recursive specification of
+ groups within groups.
+
+ While a list must be named, it is not required that the con-
+ tents of the list be included. In this case, the <address>
+ serves only as an indication of group distribution and would
+ appear in the form:
+
+ name:;
+
+ Some mail services may provide a group-list distribution
+ facility, accepting a single mailbox reference, expanding it
+ to the full distribution list, and relaying the mail to the
+ list's members. This standard provides no additional syntax
+ for indicating such a service. Using the <group> address
+ alternative, while listing one mailbox in it, can mean either
+ that the mailbox reference will be expanded to a list or that
+ there is a group with one member.
+
+ 6.2.7. EXPLICIT PATH SPECIFICATION
+
+ At times, a message originator may wish to indicate the
+ transmission path that a message should follow. This is
+ called source routing. The normal addressing scheme, used in
+ an addr-spec, is carefully separated from such information;
+ the <route> portion of a route-addr is provided for such occa-
+ sions. It specifies the sequence of hosts and/or transmission
+
+
+ August 13, 1982 - 32 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ services that are to be traversed. Both domain-refs and
+ domain-literals may be used.
+
+ Note: The use of source routing is discouraged. Unless the
+ sender has special need of path restriction, the choice
+ of transmission route should be left to the mail tran-
+ sport service.
+
+ 6.3. RESERVED ADDRESS
+
+ It often is necessary to send mail to a site, without know-
+ ing any of its valid addresses. For example, there may be mail
+ system dysfunctions, or a user may wish to find out a person's
+ correct address, at that site.
+
+ This standard specifies a single, reserved mailbox address
+ (local-part) which is to be valid at each site. Mail sent to
+ that address is to be routed to a person responsible for the
+ site's mail system or to a person with responsibility for general
+ site operation. The name of the reserved local-part address is:
+
+ Postmaster
+
+ so that "Postmaster@domain" is required to be valid.
+
+ Note: This reserved local-part must be matched without sensi-
+ tivity to alphabetic case, so that "POSTMASTER", "postmas-
+ ter", and even "poStmASteR" is to be accepted.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 33 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ 7. BIBLIOGRAPHY
+
+
+ ANSI. "USA Standard Code for Information Interchange," X3.4.
+ American National Standards Institute: New York (1968). Also
+ in: Feinler, E. and J. Postel, eds., "ARPANET Protocol Hand-
+ book", NIC 7104.
+
+ ANSI. "Representations of Universal Time, Local Time Differen-
+ tials, and United States Time Zone References for Information
+ Interchange," X3.51-1975. American National Standards Insti-
+ tute: New York (1975).
+
+ Bemer, R.W., "Time and the Computer." In: Interface Age (Feb.
+ 1979).
+
+ Bennett, C.J. "JNT Mail Protocol". Joint Network Team, Ruther-
+ ford and Appleton Laboratory: Didcot, England.
+
+ Bhushan, A.K., Pogran, K.T., Tomlinson, R.S., and White, J.E.
+ "Standardizing Network Mail Headers," ARPANET Request for
+ Comments No. 561, Network Information Center No. 18516; SRI
+ International: Menlo Park (September 1973).
+
+ Birrell, A.D., Levin, R., Needham, R.M., and Schroeder, M.D.
+ "Grapevine: An Exercise in Distributed Computing," Communica-
+ tions of the ACM 25, 4 (April 1982), 260-274.
+
+ Crocker, D.H., Vittal, J.J., Pogran, K.T., Henderson, D.A.
+ "Standard for the Format of ARPA Network Text Message,"
+ ARPANET Request for Comments No. 733, Network Information
+ Center No. 41952. SRI International: Menlo Park (November
+ 1977).
+
+ Feinler, E.J. and Postel, J.B. ARPANET Protocol Handbook, Net-
+ work Information Center No. 7104 (NTIS AD A003890). SRI
+ International: Menlo Park (April 1976).
+
+ Harary, F. "Graph Theory". Addison-Wesley: Reading, Mass.
+ (1969).
+
+ Levin, R. and Schroeder, M. "Transport of Electronic Messages
+ through a Network," TeleInformatics 79, pp. 29-33. North
+ Holland (1979). Also as Xerox Palo Alto Research Center
+ Technical Report CSL-79-4.
+
+ Myer, T.H. and Henderson, D.A. "Message Transmission Protocol,"
+ ARPANET Request for Comments, No. 680, Network Information
+ Center No. 32116. SRI International: Menlo Park (1975).
+
+
+ August 13, 1982 - 34 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ NBS. "Specification of Message Format for Computer Based Message
+ Systems, Recommended Federal Information Processing Standard."
+ National Bureau of Standards: Gaithersburg, Maryland
+ (October 1981).
+
+ NIC. Internet Protocol Transition Workbook. Network Information
+ Center, SRI-International, Menlo Park, California (March
+ 1982).
+
+ Oppen, D.C. and Dalal, Y.K. "The Clearinghouse: A Decentralized
+ Agent for Locating Named Objects in a Distributed Environ-
+ ment," OPD-T8103. Xerox Office Products Division: Palo Alto,
+ CA. (October 1981).
+
+ Postel, J.B. "Assigned Numbers," ARPANET Request for Comments,
+ No. 820. SRI International: Menlo Park (August 1982).
+
+ Postel, J.B. "Simple Mail Transfer Protocol," ARPANET Request
+ for Comments, No. 821. SRI International: Menlo Park (August
+ 1982).
+
+ Shoch, J.F. "Internetwork naming, addressing and routing," in
+ Proc. 17th IEEE Computer Society International Conference, pp.
+ 72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C.
+
+ Su, Z. and Postel, J. "The Domain Naming Convention for Internet
+ User Applications," ARPANET Request for Comments, No. 819.
+ SRI International: Menlo Park (August 1982).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 35 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ APPENDIX
+
+
+ A. EXAMPLES
+
+ A.1. ADDRESSES
+
+ A.1.1. Alfred Neuman <Neuman@BBN-TENEXA>
+
+ A.1.2. Neuman@BBN-TENEXA
+
+ These two "Alfred Neuman" examples have identical seman-
+ tics, as far as the operation of the local host's mail sending
+ (distribution) program (also sometimes called its "mailer")
+ and the remote host's mail protocol server are concerned. In
+ the first example, the "Alfred Neuman" is ignored by the
+ mailer, as "Neuman@BBN-TENEXA" completely specifies the reci-
+ pient. The second example contains no superfluous informa-
+ tion, and, again, "Neuman@BBN-TENEXA" is the intended reci-
+ pient.
+
+ Note: When the message crosses name-domain boundaries, then
+ these specifications must be changed, so as to indicate
+ the remainder of the hierarchy, starting with the top
+ level.
+
+ A.1.3. "George, Ted" <Shared@Group.Arpanet>
+
+ This form might be used to indicate that a single mailbox
+ is shared by several users. The quoted string is ignored by
+ the originating host's mailer, because "Shared@Group.Arpanet"
+ completely specifies the destination mailbox.
+
+ A.1.4. Wilt . (the Stilt) Chamberlain@NBA.US
+
+ The "(the Stilt)" is a comment, which is NOT included in
+ the destination mailbox address handed to the originating
+ system's mailer. The local-part of the address is the string
+ "Wilt.Chamberlain", with NO space between the first and second
+ words.
+
+ A.1.5. Address Lists
+
+ Gourmets: Pompous Person <WhoZiWhatZit@Cordon-Bleu>,
+ Childs@WGBH.Boston, Galloping Gourmet@
+ ANT.Down-Under (Australian National Television),
+ Cheapie@Discount-Liquors;,
+ Cruisers: Port@Portugal, Jones@SEA;,
+ Another@Somewhere.SomeOrg
+
+
+ August 13, 1982 - 36 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ This group list example points out the use of comments and the
+ mixing of addresses and groups.
+
+ A.2. ORIGINATOR ITEMS
+
+ A.2.1. Author-sent
+
+ George Jones logs into his host as "Jones". He sends
+ mail himself.
+
+ From: Jones@Group.Org
+
+ or
+
+ From: George Jones <Jones@Group.Org>
+
+ A.2.2. Secretary-sent
+
+ George Jones logs in as Jones on his host. His secre-
+ tary, who logs in as Secy sends mail for him. Replies to the
+ mail should go to George.
+
+ From: George Jones <Jones@Group>
+ Sender: Secy@Other-Group
+
+ A.2.3. Secretary-sent, for user of shared directory
+
+ George Jones' secretary sends mail for George. Replies
+ should go to George.
+
+ From: George Jones<Shared@Group.Org>
+ Sender: Secy@Other-Group
+
+ Note that there need not be a space between "Jones" and the
+ "<", but adding a space enhances readability (as is the case
+ in other examples.
+
+ A.2.4. Committee activity, with one author
+
+ George is a member of a committee. He wishes to have any
+ replies to his message go to all committee members.
+
+ From: George Jones <Jones@Host.Net>
+ Sender: Jones@Host
+ Reply-To: The Committee: Jones@Host.Net,
+ Smith@Other.Org,
+ Doe@Somewhere-Else;
+
+ Note that if George had not included himself in the
+
+
+ August 13, 1982 - 37 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ enumeration of The Committee, he would not have gotten an
+ implicit reply; the presence of the "Reply-to" field SUPER-
+ SEDES the sending of a reply to the person named in the "From"
+ field.
+
+ A.2.5. Secretary acting as full agent of author
+
+ George Jones asks his secretary (Secy@Host) to send a
+ message for him in his capacity as Group. He wants his secre-
+ tary to handle all replies.
+
+ From: George Jones <Group@Host>
+ Sender: Secy@Host
+ Reply-To: Secy@Host
+
+ A.2.6. Agent for user without online mailbox
+
+ A friend of George's, Sarah, is visiting. George's
+ secretary sends some mail to a friend of Sarah in computer-
+ land. Replies should go to George, whose mailbox is Jones at
+ Registry.
+
+ From: Sarah Friendly <Secy@Registry>
+ Sender: Secy-Name <Secy@Registry>
+ Reply-To: Jones@Registry.
+
+ A.2.7. Agent for member of a committee
+
+ George's secretary sends out a message which was authored
+ jointly by all the members of a committee. Note that the name
+ of the committee cannot be specified, since <group> names are
+ not permitted in the From field.
+
+ From: Jones@Host,
+ Smith@Other-Host,
+ Doe@Somewhere-Else
+ Sender: Secy@SHost
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 38 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ A.3. COMPLETE HEADERS
+
+ A.3.1. Minimum required
+
+ Date: 26 Aug 76 1429 EDT Date: 26 Aug 76 1429 EDT
+ From: Jones@Registry.Org or From: Jones@Registry.Org
+ Bcc: To: Smith@Registry.Org
+
+ Note that the "Bcc" field may be empty, while the "To" field
+ is required to have at least one address.
+
+ A.3.2. Using some of the additional fields
+
+ Date: 26 Aug 76 1430 EDT
+ From: George Jones<Group@Host>
+ Sender: Secy@SHOST
+ To: "Al Neuman"@Mad-Host,
+ Sam.Irving@Other-Host
+ Message-ID: <some.string@SHOST>
+
+ A.3.3. About as complex as you're going to get
+
+ Date : 27 Aug 76 0932 PDT
+ From : Ken Davis <KDavis@This-Host.This-net>
+ Subject : Re: The Syntax in the RFC
+ Sender : KSecy@Other-Host
+ Reply-To : Sam.Irving@Reg.Organization
+ To : George Jones <Group@Some-Reg.An-Org>,
+ Al.Neuman@MAD.Publisher
+ cc : Important folk:
+ Tom Softwood <Balsa@Tree.Root>,
+ "Sam Irving"@Other-Host;,
+ Standard Distribution:
+ /main/davis/people/standard@Other-Host,
+ "<Jones>standard.dist.3"@Tops-20-Host>;
+ Comment : Sam is away on business. He asked me to handle
+ his mail for him. He'll be able to provide a
+ more accurate explanation when he returns
+ next week.
+ In-Reply-To: <some.string@DBM.Group>, George's message
+ X-Special-action: This is a sample of user-defined field-
+ names. There could also be a field-name
+ "Special-action", but its name might later be
+ preempted
+ Message-ID: <4231.629.XYzi-What@Other-Host>
+
+
+
+
+
+
+ August 13, 1982 - 39 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ B. SIMPLE FIELD PARSING
+
+ Some mail-reading software systems may wish to perform only
+ minimal processing, ignoring the internal syntax of structured
+ field-bodies and treating them the same as unstructured-field-
+ bodies. Such software will need only to distinguish:
+
+ o Header fields from the message body,
+
+ o Beginnings of fields from lines which continue fields,
+
+ o Field-names from field-contents.
+
+ The abbreviated set of syntactic rules which follows will
+ suffice for this purpose. It describes a limited view of mes-
+ sages and is a subset of the syntactic rules provided in the main
+ part of this specification. One small exception is that the con-
+ tents of field-bodies consist only of text:
+
+ B.1. SYNTAX
+
+
+ message = *field *(CRLF *text)
+
+ field = field-name ":" [field-body] CRLF
+
+ field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
+
+ field-body = *text [CRLF LWSP-char field-body]
+
+
+ B.2. SEMANTICS
+
+ Headers occur before the message body and are terminated by
+ a null line (i.e., two contiguous CRLFs).
+
+ A line which continues a header field begins with a SPACE or
+ HTAB character, while a line beginning a field starts with a
+ printable character which is not a colon.
+
+ A field-name consists of one or more printable characters
+ (excluding colon, space, and control-characters). A field-name
+ MUST be contained on one line. Upper and lower case are not dis-
+ tinguished when comparing field-names.
+
+
+
+
+
+
+
+ August 13, 1982 - 40 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ C. DIFFERENCES FROM RFC #733
+
+ The following summarizes the differences between this stan-
+ dard and the one specified in Arpanet Request for Comments #733,
+ "Standard for the Format of ARPA Network Text Messages". The
+ differences are listed in the order of their occurrence in the
+ current specification.
+
+ C.1. FIELD DEFINITIONS
+
+ C.1.1. FIELD NAMES
+
+ These now must be a sequence of printable characters. They
+ may not contain any LWSP-chars.
+
+ C.2. LEXICAL TOKENS
+
+ C.2.1. SPECIALS
+
+ The characters period ("."), left-square bracket ("["), and
+ right-square bracket ("]") have been added. For presentation
+ purposes, and when passing a specification to a system that
+ does not conform to this standard, periods are to be contigu-
+ ous with their surrounding lexical tokens. No linear-white-
+ space is permitted between them. The presence of one LWSP-
+ char between other tokens is still directed.
+
+ C.2.2. ATOM
+
+ Atoms may not contain SPACE.
+
+ C.2.3. SPECIAL TEXT
+
+ ctext and qtext have had backslash ("\") added to the list of
+ prohibited characters.
+
+ C.2.4. DOMAINS
+
+ The lexical tokens <domain-literal> and <dtext> have been
+ added.
+
+ C.3. MESSAGE SPECIFICATION
+
+ C.3.1. TRACE
+
+ The "Return-path:" and "Received:" fields have been specified.
+
+
+
+
+
+ August 13, 1982 - 41 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ C.3.2. FROM
+
+ The "From" field must contain machine-usable addresses (addr-
+ spec). Multiple addresses may be specified, but named-lists
+ (groups) may not.
+
+ C.3.3. RESENT
+
+ The meta-construct of prefacing field names with the string
+ "Resent-" has been added, to indicate that a message has been
+ forwarded by an intermediate recipient.
+
+ C.3.4. DESTINATION
+
+ A message must contain at least one destination address field.
+ "To" and "CC" are required to contain at least one address.
+
+ C.3.5. IN-REPLY-TO
+
+ The field-body is no longer a comma-separated list, although a
+ sequence is still permitted.
+
+ C.3.6. REFERENCE
+
+ The field-body is no longer a comma-separated list, although a
+ sequence is still permitted.
+
+ C.3.7. ENCRYPTED
+
+ A field has been specified that permits senders to indicate
+ that the body of a message has been encrypted.
+
+ C.3.8. EXTENSION-FIELD
+
+ Extension fields are prohibited from beginning with the char-
+ acters "X-".
+
+ C.4. DATE AND TIME SPECIFICATION
+
+ C.4.1. SIMPLIFICATION
+
+ Fewer optional forms are permitted and the list of three-
+ letter time zones has been shortened.
+
+ C.5. ADDRESS SPECIFICATION
+
+
+
+
+
+
+ August 13, 1982 - 42 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ C.5.1. ADDRESS
+
+ The use of quoted-string, and the ":"-atom-":" construct, have
+ been removed. An address now is either a single mailbox
+ reference or is a named list of addresses. The latter indi-
+ cates a group distribution.
+
+ C.5.2. GROUPS
+
+ Group lists are now required to to have a name. Group lists
+ may not be nested.
+
+ C.5.3. MAILBOX
+
+ A mailbox specification may indicate a person's name, as
+ before. Such a named list no longer may specify multiple
+ mailboxes and may not be nested.
+
+ C.5.4. ROUTE ADDRESSING
+
+ Addresses now are taken to be absolute, global specifications,
+ independent of transmission paths. The <route> construct has
+ been provided, to permit explicit specification of transmis-
+ sion path. RFC #733's use of multiple at-signs ("@") was
+ intended as a general syntax for indicating routing and/or
+ hierarchical addressing. The current standard separates these
+ specifications and only one at-sign is permitted.
+
+ C.5.5. AT-SIGN
+
+ The string " at " no longer is used as an address delimiter.
+ Only at-sign ("@") serves the function.
+
+ C.5.6. DOMAINS
+
+ Hierarchical, logical name-domains have been added.
+
+ C.6. RESERVED ADDRESS
+
+ The local-part "Postmaster" has been reserved, so that users can
+ be guaranteed at least one valid address at a site.
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 43 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ D. ALPHABETICAL LISTING OF SYNTAX RULES
+
+ address = mailbox ; one addressee
+ / group ; named list
+ addr-spec = local-part "@" domain ; global address
+ ALPHA = <any ASCII alphabetic character>
+ ; (101-132, 65.- 90.)
+ ; (141-172, 97.-122.)
+ atom = 1*<any CHAR except specials, SPACE and CTLs>
+ authentic = "From" ":" mailbox ; Single author
+ / ( "Sender" ":" mailbox ; Actual submittor
+ "From" ":" 1#mailbox) ; Multiple authors
+ ; or not sender
+ CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
+ comment = "(" *(ctext / quoted-pair / comment) ")"
+ CR = <ASCII CR, carriage return> ; ( 15, 13.)
+ CRLF = CR LF
+ ctext = <any CHAR excluding "(", ; => may be folded
+ ")", "\" & CR, & including
+ linear-white-space>
+ CTL = <any ASCII control ; ( 0- 37, 0.- 31.)
+ character and DEL> ; ( 177, 127.)
+ date = 1*2DIGIT month 2DIGIT ; day month year
+ ; e.g. 20 Jun 82
+ dates = orig-date ; Original
+ [ resent-date ] ; Forwarded
+ date-time = [ day "," ] date time ; dd mm yy
+ ; hh:mm:ss zzz
+ day = "Mon" / "Tue" / "Wed" / "Thu"
+ / "Fri" / "Sat" / "Sun"
+ delimiters = specials / linear-white-space / comment
+ destination = "To" ":" 1#address ; Primary
+ / "Resent-To" ":" 1#address
+ / "cc" ":" 1#address ; Secondary
+ / "Resent-cc" ":" 1#address
+ / "bcc" ":" #address ; Blind carbon
+ / "Resent-bcc" ":" #address
+ DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.)
+ domain = sub-domain *("." sub-domain)
+ domain-literal = "[" *(dtext / quoted-pair) "]"
+ domain-ref = atom ; symbolic reference
+ dtext = <any CHAR excluding "[", ; => may be folded
+ "]", "\" & CR, & including
+ linear-white-space>
+ extension-field =
+ <Any field which is defined in a document
+ published as a formal extension to this
+ specification; none will have names beginning
+ with the string "X-">
+
+
+ August 13, 1982 - 44 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ field = field-name ":" [ field-body ] CRLF
+ fields = dates ; Creation time,
+ source ; author id & one
+ 1*destination ; address required
+ *optional-field ; others optional
+ field-body = field-body-contents
+ [CRLF LWSP-char field-body]
+ field-body-contents =
+ <the ASCII characters making up the field-body, as
+ defined in the following sections, and consisting
+ of combinations of atom, quoted-string, and
+ specials tokens, or else consisting of texts>
+ field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":">
+ group = phrase ":" [#mailbox] ";"
+ hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT]
+ ; 00:00:00 - 23:59:59
+ HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.)
+ LF = <ASCII LF, linefeed> ; ( 12, 10.)
+ linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE
+ ; CRLF => folding
+ local-part = word *("." word) ; uninterpreted
+ ; case-preserved
+ LWSP-char = SPACE / HTAB ; semantics = SPACE
+ mailbox = addr-spec ; simple address
+ / phrase route-addr ; name & addr-spec
+ message = fields *( CRLF *text ) ; Everything after
+ ; first null line
+ ; is message body
+ month = "Jan" / "Feb" / "Mar" / "Apr"
+ / "May" / "Jun" / "Jul" / "Aug"
+ / "Sep" / "Oct" / "Nov" / "Dec"
+ msg-id = "<" addr-spec ">" ; Unique message id
+ optional-field =
+ / "Message-ID" ":" msg-id
+ / "Resent-Message-ID" ":" msg-id
+ / "In-Reply-To" ":" *(phrase / msg-id)
+ / "References" ":" *(phrase / msg-id)
+ / "Keywords" ":" #phrase
+ / "Subject" ":" *text
+ / "Comments" ":" *text
+ / "Encrypted" ":" 1#2word
+ / extension-field ; To be defined
+ / user-defined-field ; May be pre-empted
+ orig-date = "Date" ":" date-time
+ originator = authentic ; authenticated addr
+ [ "Reply-To" ":" 1#address] )
+ phrase = 1*word ; Sequence of words
+
+
+
+
+ August 13, 1982 - 45 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ qtext = <any CHAR excepting <">, ; => may be folded
+ "\" & CR, and including
+ linear-white-space>
+ quoted-pair = "\" CHAR ; may quote any char
+ quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
+ ; quoted chars.
+ received = "Received" ":" ; one per relay
+ ["from" domain] ; sending host
+ ["by" domain] ; receiving host
+ ["via" atom] ; physical path
+ *("with" atom) ; link/mail protocol
+ ["id" msg-id] ; receiver msg id
+ ["for" addr-spec] ; initial form
+ ";" date-time ; time received
+
+ resent = resent-authentic
+ [ "Resent-Reply-To" ":" 1#address] )
+ resent-authentic =
+ = "Resent-From" ":" mailbox
+ / ( "Resent-Sender" ":" mailbox
+ "Resent-From" ":" 1#mailbox )
+ resent-date = "Resent-Date" ":" date-time
+ return = "Return-path" ":" route-addr ; return address
+ route = 1#("@" domain) ":" ; path-relative
+ route-addr = "<" [route] addr-spec ">"
+ source = [ trace ] ; net traversals
+ originator ; original mail
+ [ resent ] ; forwarded
+ SPACE = <ASCII SP, space> ; ( 40, 32.)
+ specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-
+ / "," / ";" / ":" / "\" / <"> ; string, to use
+ / "." / "[" / "]" ; within a word.
+ sub-domain = domain-ref / domain-literal
+ text = <any CHAR, including bare ; => atoms, specials,
+ CR & bare LF, but NOT ; comments and
+ including CRLF> ; quoted-strings are
+ ; NOT recognized.
+ time = hour zone ; ANSI and Military
+ trace = return ; path to sender
+ 1*received ; receipt tags
+ user-defined-field =
+ <Any field which has not been defined
+ in this specification or published as an
+ extension to this specification; names for
+ such fields must be unique and may be
+ pre-empted by published extensions>
+ word = atom / quoted-string
+
+
+
+
+ August 13, 1982 - 46 - RFC #822
+
+
+
+ Standard for ARPA Internet Text Messages
+
+
+ zone = "UT" / "GMT" ; Universal Time
+ ; North American : UT
+ / "EST" / "EDT" ; Eastern: - 5/ - 4
+ / "CST" / "CDT" ; Central: - 6/ - 5
+ / "MST" / "MDT" ; Mountain: - 7/ - 6
+ / "PST" / "PDT" ; Pacific: - 8/ - 7
+ / 1ALPHA ; Military: Z = UT;
+ <"> = <ASCII quote mark> ; ( 42, 34.)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ August 13, 1982 - 47 - RFC #822
+
diff --git a/rfc/sieve/rfc3028.txt b/rfc/sieve/rfc3028.txt
@@ -0,0 +1,2019 @@
+
+
+
+
+
+
+Network Working Group T. Showalter
+Request for Comments: 3028 Mirapoint, Inc.
+Category: Standards Track January 2001
+
+
+ Sieve: A Mail Filtering Language
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+Abstract
+
+ This document describes a language for filtering e-mail messages at
+ time of final delivery. It is designed to be implementable on either
+ a mail client or mail server. It is meant to be extensible, simple,
+ and independent of access protocol, mail architecture, and operating
+ system. It is suitable for running on a mail server where users may
+ not be allowed to execute arbitrary programs, such as on black box
+ Internet Message Access Protocol (IMAP) servers, as it has no
+ variables, loops, or ability to shell out to external programs.
+
+Table of Contents
+
+ 1. Introduction ........................................... 3
+ 1.1. Conventions Used in This Document ..................... 4
+ 1.2. Example mail messages ................................. 4
+ 2. Design ................................................. 5
+ 2.1. Form of the Language .................................. 5
+ 2.2. Whitespace ............................................ 5
+ 2.3. Comments .............................................. 6
+ 2.4. Literal Data .......................................... 6
+ 2.4.1. Numbers ............................................... 6
+ 2.4.2. Strings ............................................... 7
+ 2.4.2.1. String Lists .......................................... 7
+ 2.4.2.2. Headers ............................................... 8
+ 2.4.2.3. Addresses ............................................. 8
+ 2.4.2.4. MIME Parts ............................................ 9
+ 2.5. Tests ................................................. 9
+ 2.5.1. Test Lists ............................................ 9
+
+
+
+Showalter Standards Track [Page 1]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ 2.6. Arguments ............................................. 9
+ 2.6.1. Positional Arguments .................................. 9
+ 2.6.2. Tagged Arguments ...................................... 10
+ 2.6.3. Optional Arguments .................................... 10
+ 2.6.4. Types of Arguments .................................... 10
+ 2.7. String Comparison ..................................... 11
+ 2.7.1. Match Type ............................................ 11
+ 2.7.2. Comparisons Across Character Sets ..................... 12
+ 2.7.3. Comparators ........................................... 12
+ 2.7.4. Comparisons Against Addresses ......................... 13
+ 2.8. Blocks ................................................ 14
+ 2.9. Commands .............................................. 14
+ 2.10. Evaluation ............................................ 15
+ 2.10.1. Action Interaction .................................... 15
+ 2.10.2. Implicit Keep ......................................... 15
+ 2.10.3. Message Uniqueness in a Mailbox ....................... 15
+ 2.10.4. Limits on Numbers of Actions .......................... 16
+ 2.10.5. Extensions and Optional Features ...................... 16
+ 2.10.6. Errors ................................................ 17
+ 2.10.7. Limits on Execution ................................... 17
+ 3. Control Commands ....................................... 17
+ 3.1. Control Structure If .................................. 18
+ 3.2. Control Structure Require ............................. 19
+ 3.3. Control Structure Stop ................................ 19
+ 4. Action Commands ........................................ 19
+ 4.1. Action reject ......................................... 20
+ 4.2. Action fileinto ....................................... 20
+ 4.3. Action redirect ....................................... 21
+ 4.4. Action keep ........................................... 21
+ 4.5. Action discard ........................................ 22
+ 5. Test Commands .......................................... 22
+ 5.1. Test address .......................................... 23
+ 5.2. Test allof ............................................ 23
+ 5.3. Test anyof ............................................ 24
+ 5.4. Test envelope ......................................... 24
+ 5.5. Test exists ........................................... 25
+ 5.6. Test false ............................................ 25
+ 5.7. Test header ........................................... 25
+ 5.8. Test not .............................................. 26
+ 5.9. Test size ............................................. 26
+ 5.10. Test true ............................................. 26
+ 6. Extensibility .......................................... 26
+ 6.1. Capability String ..................................... 27
+ 6.2. IANA Considerations ................................... 28
+ 6.2.1. Template for Capability Registrations ................. 28
+ 6.2.2. Initial Capability Registrations ...................... 28
+ 6.3. Capability Transport .................................. 29
+ 7. Transmission ........................................... 29
+
+
+
+Showalter Standards Track [Page 2]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ 8. Parsing ................................................ 30
+ 8.1. Lexical Tokens ........................................ 30
+ 8.2. Grammar ............................................... 31
+ 9. Extended Example ....................................... 32
+ 10. Security Considerations ................................ 34
+ 11. Acknowledgments ........................................ 34
+ 12. Author's Address ....................................... 34
+ 13. References ............................................. 34
+ 14. Full Copyright Statement ............................... 36
+
+1. Introduction
+
+ This memo documents a language that can be used to create filters for
+ electronic mail. It is not tied to any particular operating system or
+ mail architecture. It requires the use of [IMAIL]-compliant
+ messages, but should otherwise generalize to many systems.
+
+ The language is powerful enough to be useful but limited in order to
+ allow for a safe server-side filtering system. The intention is to
+ make it impossible for users to do anything more complex (and
+ dangerous) than write simple mail filters, along with facilitating
+ the use of GUIs for filter creation and manipulation. The language is
+ not Turing-complete: it provides no way to write a loop or a function
+ and variables are not provided.
+
+ Scripts written in Sieve are executed during final delivery, when the
+ message is moved to the user-accessible mailbox. In systems where
+ the MTA does final delivery, such as traditional Unix mail, it is
+ reasonable to sort when the MTA deposits mail into the user's
+ mailbox.
+
+ There are a number of reasons to use a filtering system. Mail
+ traffic for most users has been increasing due to increased usage of
+ e-mail, the emergence of unsolicited email as a form of advertising,
+ and increased usage of mailing lists.
+
+ Experience at Carnegie Mellon has shown that if a filtering system is
+ made available to users, many will make use of it in order to file
+ messages from specific users or mailing lists. However, many others
+ did not make use of the Andrew system's FLAMES filtering language
+ [FLAMES] due to difficulty in setting it up.
+
+ Because of the expectation that users will make use of filtering if
+ it is offered and easy to use, this language has been made simple
+ enough to allow many users to make use of it, but rich enough that it
+ can be used productively. However, it is expected that GUI-based
+ editors will be the preferred way of editing filters for a large
+ number of users.
+
+
+
+Showalter Standards Track [Page 3]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+1.1. Conventions Used in This Document
+
+ In the sections of this document that discuss the requirements of
+ various keywords and operators, the following conventions have been
+ adopted.
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and
+ "MAY" in this document are to be interpreted as defined in
+ [KEYWORDS].
+
+ Each section on a command (test, action, or control structure) has a
+ line labeled "Syntax:". This line describes the syntax of the
+ command, including its name and its arguments. Required arguments
+ are listed inside angle brackets ("<" and ">"). Optional arguments
+ are listed inside square brackets ("[" and "]"). Each argument is
+ followed by its type, so "<key: string>" represents an argument
+ called "key" that is a string. Literal strings are represented with
+ double-quoted strings. Alternatives are separated with slashes, and
+ parenthesis are used for grouping, similar to [ABNF].
+
+ In the "Syntax" line, there are three special pieces of syntax that
+ are frequently repeated, MATCH-TYPE, COMPARATOR, and ADDRESS-PART.
+ These are discussed in sections 2.7.1, 2.7.3, and 2.7.4,
+ respectively.
+
+ The formal grammar for these commands in section 10 and is the
+ authoritative reference on how to construct commands, but the formal
+ grammar does not specify the order, semantics, number or types of
+ arguments to commands, nor the legal command names. The intent is to
+ allow for extension without changing the grammar.
+
+1.2. Example mail messages
+
+ The following mail messages will be used throughout this document in
+ examples.
+
+ Message A
+ -----------------------------------------------------------
+ Date: Tue, 1 Apr 1997 09:06:31 -0800 (PST)
+ From: coyote@desert.example.org
+ To: roadrunner@acme.example.com
+ Subject: I have a present for you
+
+ Look, I'm sorry about the whole anvil thing, and I really
+ didn't mean to try and drop it on you from the top of the
+ cliff. I want to try to make it up to you. I've got some
+ great birdseed over here at my place--top of the line
+
+
+
+
+Showalter Standards Track [Page 4]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ stuff--and if you come by, I'll have it all wrapped up
+ for you. I'm really sorry for all the problems I've caused
+ for you over the years, but I know we can work this out.
+ --
+ Wile E. Coyote "Super Genius" coyote@desert.example.org
+ -----------------------------------------------------------
+
+ Message B
+ -----------------------------------------------------------
+ From: youcouldberich!@reply-by-postal-mail.invalid
+ Sender: b1ff@de.res.example.com
+ To: rube@landru.example.edu
+ Date: Mon, 31 Mar 1997 18:26:10 -0800
+ Subject: $$$ YOU, TOO, CAN BE A MILLIONAIRE! $$$
+
+ YOU MAY HAVE ALREADY WON TEN MILLION DOLLARS, BUT I DOUBT
+ IT! SO JUST POST THIS TO SIX HUNDRED NEWSGROUPS! IT WILL
+ GUARANTEE THAT YOU GET AT LEAST FIVE RESPONSES WITH MONEY!
+ MONEY! MONEY! COLD HARD CASH! YOU WILL RECEIVE OVER
+ $20,000 IN LESS THAN TWO MONTHS! AND IT'S LEGAL!!!!!!!!!
+ !!!!!!!!!!!!!!!!!!111111111!!!!!!!11111111111!!1 JUST
+ SEND $5 IN SMALL, UNMARKED BILLS TO THE ADDRESSES BELOW!
+ -----------------------------------------------------------
+
+2. Design
+
+2.1. Form of the Language
+
+ The language consists of a set of commands. Each command consists of
+ a set of tokens delimited by whitespace. The command identifier is
+ the first token and it is followed by zero or more argument tokens.
+ Arguments may be literal data, tags, blocks of commands, or test
+ commands.
+
+ The language is represented in UTF-8, as specified in [UTF-8].
+
+ Tokens in the ASCII range are considered case-insensitive.
+
+2.2. Whitespace
+
+ Whitespace is used to separate tokens. Whitespace is made up of
+ tabs, newlines (CRLF, never just CR or LF), and the space character.
+ The amount of whitespace used is not significant.
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 5]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+2.3. Comments
+
+ Two types of comments are offered. Comments are semantically
+ equivalent to whitespace and can be used anyplace that whitespace is
+ (with one exception in multi-line strings, as described in the
+ grammar).
+
+ Hash comments begin with a "#" character that is not contained within
+ a string and continue until the next CRLF.
+
+ Example: if size :over 100K { # this is a comment
+ discard;
+ }
+
+ Bracketed comments begin with the token "/*" and end with "*/" outside
+ of a string. Bracketed comments may span multiple lines. Bracketed
+ comments do not nest.
+
+ Example: if size :over 100K { /* this is a comment
+ this is still a comment */ discard /* this is a comment
+ */ ;
+ }
+
+2.4. Literal Data
+
+ Literal data means data that is not executed, merely evaluated "as
+ is", to be used as arguments to commands. Literal data is limited to
+ numbers and strings.
+
+2.4.1. Numbers
+
+ Numbers are given as ordinary decimal numbers. However, those
+ numbers that have a tendency to be fairly large, such as message
+ sizes, MAY have a "K", "M", or "G" appended to indicate a multiple of
+ a power of two. To be comparable with the power-of-two-based
+ versions of SI units that computers frequently use, K specifies
+ kibi-, or 1,024 (2^10) times the value of the number; M specifies
+ mebi-, or 1,048,576 (2^20) times the value of the number; and G
+ specifies tebi-, or 1,073,741,824 (2^30) times the value of the
+ number [BINARY-SI].
+
+ Implementations MUST provide 31 bits of magnitude in numbers, but MAY
+ provide more.
+
+ Only positive integers are permitted by this specification.
+
+
+
+
+
+
+Showalter Standards Track [Page 6]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+2.4.2. Strings
+
+ Scripts involve large numbers of strings as they are used for pattern
+ matching, addresses, textual bodies, etc. Typically, short quoted
+ strings suffice for most uses, but a more convenient form is provided
+ for longer strings such as bodies of messages.
+
+ A quoted string starts and ends with a single double quote (the <">
+ character, ASCII 34). A backslash ("\", ASCII 92) inside of a quoted
+ string is followed by either another backslash or a double quote.
+ This two-character sequence represents a single backslash or double-
+ quote within the string, respectively.
+
+ No other characters should be escaped with a single backslash.
+
+ An undefined escape sequence (such as "\a" in a context where "a" has
+ no special meaning) is interpreted as if there were no backslash (in
+ this case, "\a" is just "a").
+
+ Non-printing characters such as tabs, CR and LF, and control
+ characters are permitted in quoted strings. Quoted strings MAY span
+ multiple lines. NUL (ASCII 0) is not allowed in strings.
+
+ For entering larger amounts of text, such as an email message, a
+ multi-line form is allowed. It starts with the keyword "text:",
+ followed by a CRLF, and ends with the sequence of a CRLF, a single
+ period, and another CRLF. In order to allow the message to contain
+ lines with a single-dot, lines are dot-stuffed. That is, when
+ composing a message body, an extra `.' is added before each line
+ which begins with a `.'. When the server interprets the script,
+ these extra dots are removed. Note that a line that begins with a
+ dot followed by a non-dot character is not interpreted dot-stuffed;
+ that is, ".foo" is interpreted as ".foo". However, because this is
+ potentially ambiguous, scripts SHOULD be properly dot-stuffed so such
+ lines do not appear.
+
+ Note that a hashed comment or whitespace may occur in between the
+ "text:" and the CRLF, but not within the string itself. Bracketed
+ comments are not allowed here.
+
+2.4.2.1. String Lists
+
+ When matching patterns, it is frequently convenient to match against
+ groups of strings instead of single strings. For this reason, a list
+ of strings is allowed in many tests, implying that if the test is
+ true using any one of the strings, then the test is true.
+ Implementations are encouraged to use short-circuit evaluation in
+ these cases.
+
+
+
+Showalter Standards Track [Page 7]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ For instance, the test `header :contains ["To", "Cc"]
+ ["me@example.com", "me00@landru.example.edu"]' is true if either the
+ To header or Cc header of the input message contains either of the
+ e-mail addresses "me@example.com" or "me00@landru.example.edu".
+
+ Conversely, in any case where a list of strings is appropriate, a
+ single string is allowed without being a member of a list: it is
+ equivalent to a list with a single member. This means that the test
+ `exists "To"' is equivalent to the test `exists ["To"]'.
+
+2.4.2.2. Headers
+
+ Headers are a subset of strings. In the Internet Message
+ Specification [IMAIL] [RFC1123], each header line is allowed to have
+ whitespace nearly anywhere in the line, including after the field
+ name and before the subsequent colon. Extra spaces between the
+ header name and the ":" in a header field are ignored.
+
+ A header name never contains a colon. The "From" header refers to a
+ line beginning "From:" (or "From :", etc.). No header will match
+ the string "From:" due to the trailing colon.
+
+ Folding of long header lines (as described in [IMAIL] 3.4.8) is
+ removed prior to interpretation of the data. The folding syntax (the
+ CRLF that ends a line plus any leading whitespace at the beginning of
+ the next line that indicates folding) are interpreted as if they were
+ a single space.
+
+2.4.2.3. Addresses
+
+ A number of commands call for email addresses, which are also a
+ subset of strings. When these addresses are used in outbound
+ contexts, addresses must be compliant with [IMAIL], but are further
+ constrained. Using the symbols defined in [IMAIL], section 6.1, the
+ syntax of an address is:
+
+ sieve-address = addr-spec ; simple address
+ / phrase "<" addr-spec ">" ; name & addr-spec
+
+ That is, routes and group syntax are not permitted. If multiple
+ addresses are required, use a string list. Named groups are not used
+ here.
+
+ Implementations MUST ensure that the addresses are syntactically
+ valid, but need not ensure that they actually identify an email
+ recipient.
+
+
+
+
+
+Showalter Standards Track [Page 8]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+2.4.2.4. MIME Parts
+
+ In a few places, [MIME] body parts are represented as strings. These
+ parts include MIME headers and the body. This provides a way of
+ embedding typed data within a Sieve script so that, among other
+ things, character sets other than UTF-8 can be used for output
+ messages.
+
+2.5. Tests
+
+ Tests are given as arguments to commands in order to control their
+ actions. In this document, tests are given to if/elsif/else to
+ decide which block of code is run.
+
+ Tests MUST NOT have side effects. That is, a test cannot affect the
+ state of the filter or message. No tests in this specification have
+ side effects, and side effects are forbidden in extension tests as
+ well.
+
+ The rationale for this is that tests with side effects impair
+ readability and maintainability and are difficult to represent in a
+ graphic interface for generating scripts. Side effects are confined
+ to actions where they are clearer.
+
+2.5.1. Test Lists
+
+ Some tests ("allof" and "anyof", which implement logical "and" and
+ logical "or", respectively) may require more than a single test as an
+ argument. The test-list syntax element provides a way of grouping
+ tests.
+
+ Example: if anyof (not exists ["From", "Date"],
+ header :contains "from" "fool@example.edu") {
+ discard;
+ }
+
+2.6. Arguments
+
+ In order to specify what to do, most commands take arguments. There
+ are three types of arguments: positional, tagged, and optional.
+
+2.6.1. Positional Arguments
+
+ Positional arguments are given to a command which discerns their
+ meaning based on their order. When a command takes positional
+ arguments, all positional arguments must be supplied and must be in
+ the order prescribed.
+
+
+
+
+Showalter Standards Track [Page 9]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+2.6.2. Tagged Arguments
+
+ This document provides for tagged arguments in the style of
+ CommonLISP. These are also similar to flags given to commands in
+ most command-line systems.
+
+ A tagged argument is an argument for a command that begins with ":"
+ followed by a tag naming the argument, such as ":contains". This
+ argument means that zero or more of the next tokens have some
+ particular meaning depending on the argument. These next tokens may
+ be numbers or strings but they are never blocks.
+
+ Tagged arguments are similar to positional arguments, except that
+ instead of the meaning being derived from the command, it is derived
+ from the tag.
+
+ Tagged arguments must appear before positional arguments, but they
+ may appear in any order with other tagged arguments. For simplicity
+ of the specification, this is not expressed in the syntax definitions
+ with commands, but they still may be reordered arbitrarily provided
+ they appear before positional arguments. Tagged arguments may be
+ mixed with optional arguments.
+
+ To simplify this specification, tagged arguments SHOULD NOT take
+ tagged arguments as arguments.
+
+2.6.3. Optional Arguments
+
+ Optional arguments are exactly like tagged arguments except that they
+ may be left out, in which case a default value is implied. Because
+ optional arguments tend to result in shorter scripts, they have been
+ used far more than tagged arguments.
+
+ One particularly noteworthy case is the ":comparator" argument, which
+ allows the user to specify which [ACAP] comparator will be used to
+ compare two strings, since different languages may impose different
+ orderings on UTF-8 [UTF-8] characters.
+
+2.6.4. Types of Arguments
+
+ Abstractly, arguments may be literal data, tests, or blocks of
+ commands. In this way, an "if" control structure is merely a command
+ that happens to take a test and a block as arguments and may execute
+ the block of code.
+
+ However, this abstraction is ambiguous from a parsing standpoint.
+ The grammar in section 9.2 presents a parsable version of this:
+ Arguments are string-lists, numbers, and tags, which may be followed
+
+
+
+Showalter Standards Track [Page 10]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ by a test or a test-list, which may be followed by a block of
+ commands. No more than one test or test list, nor more than one
+ block of commands, may be used, and commands that end with blocks of
+ commands do not end with semicolons.
+
+2.7. String Comparison
+
+ When matching one string against another, there are a number of ways
+ of performing the match operation. These are accomplished with three
+ types of matches: an exact match, a substring match, and a wildcard
+ glob-style match. These are described below.
+
+ In order to provide for matches between character sets and case
+ insensitivity, Sieve borrows ACAP's comparator registry.
+
+ However, when a string represents the name of a header, the
+ comparator is never user-specified. Header comparisons are always
+ done with the "i;ascii-casemap" operator, i.e., case-insensitive
+ comparisons, because this is the way things are defined in the
+ message specification [IMAIL].
+
+2.7.1. Match Type
+
+ There are three match types describing the matching used in this
+ specification: ":is", ":contains", and ":matches". Match type
+ arguments are supplied to those commands which allow them to specify
+ what kind of match is to be performed.
+
+ These are used as tagged arguments to tests that perform string
+ comparison.
+
+ The ":contains" match type describes a substring match. If the value
+ argument contains the key argument as a substring, the match is true.
+ For instance, the string "frobnitzm" contains "frob" and "nit", but
+ not "fbm". The null key ("") is contained in all values.
+
+ The ":is" match type describes an absolute match; if the contents of
+ the first string are absolutely the same as the contents of the
+ second string, they match. Only the string "frobnitzm" is the string
+ "frobnitzm". The null key ":is" and only ":is" the null value.
+
+ The ":matches" version specifies a wildcard match using the
+ characters "*" and "?". "*" matches zero or more characters, and "?"
+ matches a single character. "?" and "*" may be escaped as "\\?" and
+ "\\*" in strings to match against themselves. The first backslash
+ escapes the second backslash; together, they escape the "*". This is
+ awkward, but it is commonplace in several programming languages that
+ use globs and regular expressions.
+
+
+
+Showalter Standards Track [Page 11]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ In order to specify what type of match is supposed to happen,
+ commands that support matching take optional tagged arguments
+ ":matches", ":is", and ":contains". Commands default to using ":is"
+ matching if no match type argument is supplied. Note that these
+ modifiers may interact with comparators; in particular, some
+ comparators are not suitable for matching with ":contains" or
+ ":matches". It is an error to use a comparator with ":contains" or
+ ":matches" that is not compatible with it.
+
+ It is an error to give more than one of these arguments to a given
+ command.
+
+ For convenience, the "MATCH-TYPE" syntax element is defined here as
+ follows:
+
+ Syntax: ":is" / ":contains" / ":matches"
+
+2.7.2. Comparisons Across Character Sets
+
+ All Sieve scripts are represented in UTF-8, but messages may involve
+ a number of character sets. In order for comparisons to work across
+ character sets, implementations SHOULD implement the following
+ behavior:
+
+ Implementations decode header charsets to UTF-8. Two strings are
+ considered equal if their UTF-8 representations are identical.
+ Implementations should decode charsets represented in the forms
+ specified by [MIME] for both message headers and bodies.
+ Implementations must be capable of decoding US-ASCII, ISO-8859-1,
+ the ASCII subset of ISO-8859-* character sets, and UTF-8.
+
+ If implementations fail to support the above behavior, they MUST
+ conform to the following:
+
+ No two strings can be considered equal if one contains octets
+ greater than 127.
+
+2.7.3. Comparators
+
+ In order to allow for language-independent, case-independent matches,
+ the match type may be coupled with a comparator name. Comparators
+ are described for [ACAP]; a registry is defined for ACAP, and this
+ specification uses that registry.
+
+ ACAP defines multiple comparator types. Only equality types are used
+ in this specification.
+
+
+
+
+
+Showalter Standards Track [Page 12]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ All implementations MUST support the "i;octet" comparator (simply
+ compares octets) and the "i;ascii-casemap" comparator (which treats
+ uppercase and lowercase characters in the ASCII subset of UTF-8 as
+ the same). If left unspecified, the default is "i;ascii-casemap".
+
+ Some comparators may not be usable with substring matches; that is,
+ they may only work with ":is". It is an error to try and use a
+ comparator with ":matches" or ":contains" that is not compatible with
+ it.
+
+ A comparator is specified by the ":comparator" option with commands
+ that support matching. This option is followed by a string providing
+ the name of the comparator to be used. For convenience, the syntax
+ of a comparator is abbreviated to "COMPARATOR", and (repeated in
+ several tests) is as follows:
+
+ Syntax: ":comparator" <comparator-name: string>
+
+ So in this example,
+
+ Example: if header :contains :comparator "i;octet" "Subject"
+ "MAKE MONEY FAST" {
+ discard;
+ }
+
+ would discard any message with subjects like "You can MAKE MONEY
+ FAST", but not "You can Make Money Fast", since the comparator used
+ is case-sensitive.
+
+ Comparators other than i;octet and i;ascii-casemap must be declared
+ with require, as they are extensions. If a comparator declared with
+ require is not known, it is an error, and execution fails. If the
+ comparator is not declared with require, it is also an error, even if
+ the comparator is supported. (See 2.10.5.)
+
+ Both ":matches" and ":contains" match types are compatible with the
+ "i;octet" and "i;ascii-casemap" comparators and may be used with
+ them.
+
+ It is an error to give more than one of these arguments to a given
+ command.
+
+2.7.4. Comparisons Against Addresses
+
+ Addresses are one of the most frequent things represented as strings.
+ These are structured, and being able to compare against the local-
+ part or the domain of an address is useful, so some tests that act
+
+
+
+
+Showalter Standards Track [Page 13]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ exclusively on addresses take an additional optional argument that
+ specifies what the test acts on.
+
+ These optional arguments are ":localpart", ":domain", and ":all",
+ which act on the local-part (left-side), the domain part (right-
+ side), and the whole address.
+
+ The kind of comparison done, such as whether or not the test done is
+ case-insensitive, is specified as a comparator argument to the test.
+
+ If an optional address-part is omitted, the default is ":all".
+
+ It is an error to give more than one of these arguments to a given
+ command.
+
+ For convenience, the "ADDRESS-PART" syntax element is defined here as
+ follows:
+
+ Syntax: ":localpart" / ":domain" / ":all"
+
+2.8. Blocks
+
+ Blocks are sets of commands enclosed within curly braces. Blocks are
+ supplied to commands so that the commands can implement control
+ commands.
+
+ A control structure is a command that happens to take a test and a
+ block as one of its arguments; depending on the result of the test
+ supplied as another argument, it runs the code in the block some
+ number of times.
+
+ With the commands supplied in this memo, there are no loops. The
+ control structures supplied--if, elsif, and else--run a block either
+ once or not at all. So there are two arguments, the test and the
+ block.
+
+2.9. Commands
+
+ Sieve scripts are sequences of commands. Commands can take any of
+ the tokens above as arguments, and arguments may be either tagged or
+ positional arguments. Not all commands take all arguments.
+
+ There are three kinds of commands: test commands, action commands,
+ and control commands.
+
+ The simplest is an action command. An action command is an
+ identifier followed by zero or more arguments, terminated by a
+ semicolon. Action commands do not take tests or blocks as arguments.
+
+
+
+Showalter Standards Track [Page 14]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ A control command is similar, but it takes a test as an argument, and
+ ends with a block instead of a semicolon.
+
+ A test command is used as part of a control command. It is used to
+ specify whether or not the block of code given to the control command
+ is executed.
+
+2.10. Evaluation
+
+2.10.1. Action Interaction
+
+ Some actions cannot be used with other actions because the result
+ would be absurd. These restrictions are noted throughout this memo.
+
+ Extension actions MUST state how they interact with actions defined
+ in this specification.
+
+2.10.2. Implicit Keep
+
+ Previous experience with filtering systems suggests that cases tend
+ to be missed in scripts. To prevent errors, Sieve has an "implicit
+ keep".
+
+ An implicit keep is a keep action (see 4.4) performed in absence of
+ any action that cancels the implicit keep.
+
+ An implicit keep is performed if a message is not written to a
+ mailbox, redirected to a new address, or explicitly thrown out. That
+ is, if a fileinto, a keep, a redirect, or a discard is performed, an
+ implicit keep is not.
+
+ Some actions may be defined to not cancel the implicit keep. These
+ actions may not directly affect the delivery of a message, and are
+ used for their side effects. None of the actions specified in this
+ document meet that criteria, but extension actions will.
+
+ For instance, with any of the short messages offered above, the
+ following script produces no actions.
+
+ Example: if size :over 500K { discard; }
+
+ As a result, the implicit keep is taken.
+
+2.10.3. Message Uniqueness in a Mailbox
+
+ Implementations SHOULD NOT deliver a message to the same folder more
+ than once, even if a script explicitly asks for a message to be
+ written to a mailbox twice.
+
+
+
+Showalter Standards Track [Page 15]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ The test for equality of two messages is implementation-defined.
+
+ If a script asks for a message to be written to a mailbox twice, it
+ MUST NOT be treated as an error.
+
+2.10.4. Limits on Numbers of Actions
+
+ Site policy MAY limit numbers of actions taken and MAY impose
+ restrictions on which actions can be used together. In the event
+ that a script hits a policy limit on the number of actions taken for
+ a particular message, an error occurs.
+
+ Implementations MUST prohibit more than one reject.
+
+ Implementations MUST allow at least one keep or one fileinto. If
+ fileinto is not implemented, implementations MUST allow at least one
+ keep.
+
+ Implementations SHOULD prohibit reject when used with other actions.
+
+2.10.5. Extensions and Optional Features
+
+ Because of the differing capabilities of many mail systems, several
+ features of this specification are optional. Before any of these
+ extensions can be executed, they must be declared with the "require"
+ action.
+
+ If an extension is not enabled with "require", implementations MUST
+ treat it as if they did not support it at all.
+
+ If a script does not understand an extension declared with require,
+ the script must not be used at all. Implementations MUST NOT execute
+ scripts which require unknown capability names.
+
+ Note: The reason for this restriction is that prior experiences with
+ languages such as LISP and Tcl suggest that this is a workable
+ way of noting that a given script uses an extension.
+
+ Experience with PostScript suggests that mechanisms that allow
+ a script to work around missing extensions are not used in
+ practice.
+
+ Extensions which define actions MUST state how they interact with
+ actions discussed in the base specification.
+
+
+
+
+
+
+
+Showalter Standards Track [Page 16]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+2.10.6. Errors
+
+ In any programming language, there are compile-time and run-time
+ errors.
+
+ Compile-time errors are ones in syntax that are detectable if a
+ syntax check is done.
+
+ Run-time errors are not detectable until the script is run. This
+ includes transient failures like disk full conditions, but also
+ includes issues like invalid combinations of actions.
+
+ When an error occurs in a Sieve script, all processing stops.
+
+ Implementations MAY choose to do a full parse, then evaluate the
+ script, then do all actions. Implementations might even go so far as
+ to ensure that execution is atomic (either all actions are executed
+ or none are executed).
+
+ Other implementations may choose to parse and run at the same time.
+ Such implementations are simpler, but have issues with partial
+ failure (some actions happen, others don't).
+
+ Implementations might even go so far as to ensure that scripts can
+ never execute an invalid set of actions (e.g., reject + fileinto)
+ before execution, although this could involve solving the Halting
+ Problem.
+
+ This specification allows any of these approaches. Solving the
+ Halting Problem is considered extra credit.
+
+ When an error happens, implementations MUST notify the user that an
+ error occurred, which actions (if any) were taken, and do an implicit
+ keep.
+
+2.10.7. Limits on Execution
+
+ Implementations may limit certain constructs. However, this
+ specification places a lower bound on some of these limits.
+
+ Implementations MUST support fifteen levels of nested blocks.
+
+ Implementations MUST support fifteen levels of nested test lists.
+
+3. Control Commands
+
+ Control structures are needed to allow for multiple and conditional
+ actions.
+
+
+
+Showalter Standards Track [Page 17]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+3.1. Control Structure If
+
+ There are three pieces to if: "if", "elsif", and "else". Each is
+ actually a separate command in terms of the grammar. However, an
+ elsif MUST only follow an if, and an else MUST follow only either an
+ if or an elsif. An error occurs if these conditions are not met.
+
+ Syntax: if <test1: test> <block1: block>
+
+ Syntax: elsif <test2: test> <block2: block>
+
+ Syntax: else <block>
+
+ The semantics are similar to those of any of the many other
+ programming languages these control commands appear in. When the
+ interpreter sees an "if", it evaluates the test associated with it.
+ If the test is true, it executes the block associated with it.
+
+ If the test of the "if" is false, it evaluates the test of the first
+ "elsif" (if any). If the test of "elsif" is true, it runs the
+ elsif's block. An elsif may be followed by an elsif, in which case,
+ the interpreter repeats this process until it runs out of elsifs.
+
+ When the interpreter runs out of elsifs, there may be an "else" case.
+ If there is, and none of the if or elsif tests were true, the
+ interpreter runs the else case.
+
+ This provides a way of performing exactly one of the blocks in the
+ chain.
+
+ In the following example, both Message A and B are dropped.
+
+ Example: require "fileinto";
+ if header :contains "from" "coyote" {
+ discard;
+ } elsif header :contains ["subject"] ["$$$"] {
+ discard;
+ } else {
+ fileinto "INBOX";
+ }
+
+
+ When the script below is run over message A, it redirects the message
+ to acm@example.edu; message B, to postmaster@example.edu; any other
+ message is redirected to field@example.edu.
+
+
+
+
+
+
+Showalter Standards Track [Page 18]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Example: if header :contains ["From"] ["coyote"] {
+ redirect "acm@example.edu";
+ } elsif header :contains "Subject" "$$$" {
+ redirect "postmaster@example.edu";
+ } else {
+ redirect "field@example.edu";
+ }
+
+ Note that this definition prohibits the "... else if ..." sequence
+ used by C. This is intentional, because this construct produces a
+ shift-reduce conflict.
+
+3.2. Control Structure Require
+
+ Syntax: require <capabilities: string-list>
+
+ The require action notes that a script makes use of a certain
+ extension. Such a declaration is required to use the extension, as
+ discussed in section 2.10.5. Multiple capabilities can be declared
+ with a single require.
+
+ The require command, if present, MUST be used before anything other
+ than a require can be used. An error occurs if a require appears
+ after a command other than require.
+
+ Example: require ["fileinto", "reject"];
+
+ Example: require "fileinto";
+ require "vacation";
+
+3.3. Control Structure Stop
+
+ Syntax: stop
+
+ The "stop" action ends all processing. If no actions have been
+ executed, then the keep action is taken.
+
+4. Action Commands
+
+ This document supplies five actions that may be taken on a message:
+ keep, fileinto, redirect, reject, and discard.
+
+ Implementations MUST support the "keep", "discard", and "redirect"
+ actions.
+
+ Implementations SHOULD support "reject" and "fileinto".
+
+
+
+
+
+Showalter Standards Track [Page 19]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Implementations MAY limit the number of certain actions taken (see
+ section 2.10.4).
+
+4.1. Action reject
+
+ Syntax: reject <reason: string>
+
+ The optional "reject" action refuses delivery of a message by sending
+ back an [MDN] to the sender. It resends the message to the sender,
+ wrapping it in a "reject" form, noting that it was rejected by the
+ recipient. In the following script, message A is rejected and
+ returned to the sender.
+
+ Example: if header :contains "from" "coyote@desert.example.org" {
+ reject "I am not taking mail from you, and I don't want
+ your birdseed, either!";
+ }
+
+ A reject message MUST take the form of a failure MDN as specified by
+ [MDN]. The human-readable portion of the message, the first
+ component of the MDN, contains the human readable message describing
+ the error, and it SHOULD contain additional text alerting the
+ original sender that mail was refused by a filter. This part of the
+ MDN might appear as follows:
+
+ ------------------------------------------------------------
+ Message was refused by recipient's mail filtering program. Reason
+ given was as follows:
+
+ I am not taking mail from you, and I don't want your birdseed,
+ either!
+ ------------------------------------------------------------
+
+ The MDN action-value field as defined in the MDN specification MUST
+ be "deleted" and MUST have the MDN-sent-automatically and automatic-
+ action modes set.
+
+ Because some implementations can not or will not implement the reject
+ command, it is optional. The capability string to be used with the
+ require command is "reject".
+
+4.2. Action fileinto
+
+ Syntax: fileinto <folder: string>
+
+ The "fileinto" action delivers the message into the specified folder.
+ Implementations SHOULD support fileinto, but in some environments
+ this may be impossible.
+
+
+
+Showalter Standards Track [Page 20]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ The capability string for use with the require command is "fileinto".
+
+ In the following script, message A is filed into folder
+ "INBOX.harassment".
+
+ Example: require "fileinto";
+ if header :contains ["from"] "coyote" {
+ fileinto "INBOX.harassment";
+ }
+
+4.3. Action redirect
+
+ Syntax: redirect <address: string>
+
+ The "redirect" action is used to send the message to another user at
+ a supplied address, as a mail forwarding feature does. The
+ "redirect" action makes no changes to the message body or existing
+ headers, but it may add new headers. The "redirect" modifies the
+ envelope recipient.
+
+ The redirect command performs an MTA-style "forward"--that is, what
+ you get from a .forward file using sendmail under UNIX. The address
+ on the SMTP envelope is replaced with the one on the redirect command
+ and the message is sent back out. (This is not an MUA-style forward,
+ which creates a new message with a different sender and message ID,
+ wrapping the old message in a new one.)
+
+ A simple script can be used for redirecting all mail:
+
+ Example: redirect "bart@example.edu";
+
+ Implementations SHOULD take measures to implement loop control,
+ possibly including adding headers to the message or counting received
+ headers. If an implementation detects a loop, it causes an error.
+
+4.4. Action keep
+
+ Syntax: keep
+
+ The "keep" action is whatever action is taken in lieu of all other
+ actions, if no filtering happens at all; generally, this simply means
+ to file the message into the user's main mailbox. This command
+ provides a way to execute this action without needing to know the
+ name of the user's main mailbox, providing a way to call it without
+ needing to understand the user's setup, or the underlying mail
+ system.
+
+
+
+
+
+Showalter Standards Track [Page 21]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ For instance, in an implementation where the IMAP server is running
+ scripts on behalf of the user at time of delivery, a keep command is
+ equivalent to a fileinto "INBOX".
+
+ Example: if size :under 1M { keep; } else { discard; }
+
+ Note that the above script is identical to the one below.
+
+ Example: if not size :under 1M { discard; }
+
+4.5. Action discard
+
+ Syntax: discard
+
+ Discard is used to silently throw away the message. It does so by
+ simply canceling the implicit keep. If discard is used with other
+ actions, the other actions still happen. Discard is compatible with
+ all other actions. (For instance fileinto+discard is equivalent to
+ fileinto.)
+
+ Discard MUST be silent; that is, it MUST NOT return a non-delivery
+ notification of any kind ([DSN], [MDN], or otherwise).
+
+ In the following script, any mail from "idiot@example.edu" is thrown
+ out.
+
+ Example: if header :contains ["from"] ["idiot@example.edu"] {
+ discard;
+ }
+
+ While an important part of this language, "discard" has the potential
+ to create serious problems for users: Students who leave themselves
+ logged in to an unattended machine in a public computer lab may find
+ their script changed to just "discard". In order to protect users in
+ this situation (along with similar situations), implementations MAY
+ keep messages destroyed by a script for an indefinite period, and MAY
+ disallow scripts that throw out all mail.
+
+5. Test Commands
+
+ Tests are used in conditionals to decide which part(s) of the
+ conditional to execute.
+
+ Implementations MUST support these tests: "address", "allof",
+ "anyof", "exists", "false", "header", "not", "size", and "true".
+
+ Implementations SHOULD support the "envelope" test.
+
+
+
+
+Showalter Standards Track [Page 22]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+5.1. Test address
+
+ Syntax: address [ADDRESS-PART] [COMPARATOR] [MATCH-TYPE]
+ <header-list: string-list> <key-list: string-list>
+
+ The address test matches Internet addresses in structured headers
+ that contain addresses. It returns true if any header contains any
+ key in the specified part of the address, as modified by the
+ comparator and the match keyword.
+
+ Like envelope and header, this test returns true if any combination
+ of the header-list and key-list arguments match.
+
+ Internet email addresses [IMAIL] have the somewhat awkward
+ characteristic that the local-part to the left of the at-sign is
+ considered case sensitive, and the domain-part to the right of the
+ at-sign is case insensitive. The "address" command does not deal
+ with this itself, but provides the ADDRESS-PART argument for allowing
+ users to deal with it.
+
+ The address primitive never acts on the phrase part of an email
+ address, nor on comments within that address. It also never acts on
+ group names, although it does act on the addresses within the group
+ construct.
+
+ Implementations MUST restrict the address test to headers that
+ contain addresses, but MUST include at least From, To, Cc, Bcc,
+ Sender, Resent-From, Resent-To, and SHOULD include any other header
+ that utilizes an "address-list" structured header body.
+
+ Example: if address :is :all "from" "tim@example.com" {
+ discard;
+
+5.2. Test allof
+
+ Syntax: allof <tests: test-list>
+
+ The allof test performs a logical AND on the tests supplied to it.
+
+ Example: allof (false, false) => false
+ allof (false, true) => false
+ allof (true, true) => true
+
+ The allof test takes as its argument a test-list.
+
+
+
+
+
+
+
+Showalter Standards Track [Page 23]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+5.3. Test anyof
+
+ Syntax: anyof <tests: test-list>
+
+ The anyof test performs a logical OR on the tests supplied to it.
+
+ Example: anyof (false, false) => false
+ anyof (false, true) => true
+ anyof (true, true) => true
+
+5.4. Test envelope
+
+ Syntax: envelope [COMPARATOR] [ADDRESS-PART] [MATCH-TYPE]
+ <envelope-part: string-list> <key-list: string-list>
+
+ The "envelope" test is true if the specified part of the SMTP (or
+ equivalent) envelope matches the specified key.
+
+ If one of the envelope-part strings is (case insensitive) "from",
+ then matching occurs against the FROM address used in the SMTP MAIL
+ command.
+
+ If one of the envelope-part strings is (case insensitive) "to", then
+ matching occurs against the TO address used in the SMTP RCPT command
+ that resulted in this message getting delivered to this user. Note
+ that only the most recent TO is available, and only the one relevant
+ to this user.
+
+ The envelope-part is a string list and may contain more than one
+ parameter, in which case all of the strings specified in the key-list
+ are matched against all parts given in the envelope-part list.
+
+ Like address and header, this test returns true if any combination of
+ the envelope-part and key-list arguments is true.
+
+ All tests against envelopes MUST drop source routes.
+
+ If the SMTP transaction involved several RCPT commands, only the data
+ from the RCPT command that caused delivery to this user is available
+ in the "to" part of the envelope.
+
+ If a protocol other than SMTP is used for message transport,
+ implementations are expected to adapt this command appropriately.
+
+ The envelope command is optional. Implementations SHOULD support it,
+ but the necessary information may not be available in all cases.
+
+
+
+
+
+Showalter Standards Track [Page 24]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Example: require "envelope";
+ if envelope :all :is "from" "tim@example.com" {
+ discard;
+ }
+
+5.5. Test exists
+
+ Syntax: exists <header-names: string-list>
+
+ The "exists" test is true if the headers listed in the header-names
+ argument exist within the message. All of the headers must exist or
+ the test is false.
+
+ The following example throws out mail that doesn't have a From header
+ and a Date header.
+
+ Example: if not exists ["From","Date"] {
+ discard;
+ }
+
+5.6. Test false
+
+ Syntax: false
+
+ The "false" test always evaluates to false.
+
+5.7. Test header
+
+ Syntax: header [COMPARATOR] [MATCH-TYPE]
+ <header-names: string-list> <key-list: string-list>
+
+ The "header" test evaluates to true if any header name matches any
+ key. The type of match is specified by the optional match argument,
+ which defaults to ":is" if not specified, as specified in section
+ 2.6.
+
+ Like address and envelope, this test returns true if any combination
+ of the string-list and key-list arguments match.
+
+ If a header listed in the header-names argument exists, it contains
+ the null key (""). However, if the named header is not present, it
+ does not contain the null key. So if a message contained the header
+
+ X-Caffeine: C8H10N4O2
+
+
+
+
+
+
+
+Showalter Standards Track [Page 25]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ these tests on that header evaluate as follows:
+
+ header :is ["X-Caffeine"] [""] => false
+ header :contains ["X-Caffeine"] [""] => true
+
+5.8. Test not
+
+ Syntax: not <test>
+
+ The "not" test takes some other test as an argument, and yields the
+ opposite result. "not false" evaluates to "true" and "not true"
+ evaluates to "false".
+
+5.9. Test size
+
+ Syntax: size <":over" / ":under"> <limit: number>
+
+ The "size" test deals with the size of a message. It takes either a
+ tagged argument of ":over" or ":under", followed by a number
+ representing the size of the message.
+
+ If the argument is ":over", and the size of the message is greater
+ than the number provided, the test is true; otherwise, it is false.
+
+ If the argument is ":under", and the size of the message is less than
+ the number provided, the test is true; otherwise, it is false.
+
+ Exactly one of ":over" or ":under" must be specified, and anything
+ else is an error.
+
+ The size of a message is defined to be the number of octets from the
+ initial header until the last character in the message body.
+
+ Note that for a message that is exactly 4,000 octets, the message is
+ neither ":over" 4000 octets or ":under" 4000 octets.
+
+5.10. Test true
+
+ Syntax: true
+
+ The "true" test always evaluates to true.
+
+6. Extensibility
+
+ New control structures, actions, and tests can be added to the
+ language. Sites must make these features known to their users; this
+ document does not define a way to discover the list of extensions
+ supported by the server.
+
+
+
+Showalter Standards Track [Page 26]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Any extensions to this language MUST define a capability string that
+ uniquely identifies that extension. If a new version of an extension
+ changes the functionality of a previously defined extension, it MUST
+ use a different name.
+
+ In a situation where there is a submission protocol and an extension
+ advertisement mechanism aware of the details of this language,
+ scripts submitted can be checked against the mail server to prevent
+ use of an extension that the server does not support.
+
+ Extensions MUST state how they interact with constraints defined in
+ section 2.10, e.g., whether they cancel the implicit keep, and which
+ actions they are compatible and incompatible with.
+
+6.1. Capability String
+
+ Capability strings are typically short strings describing what
+ capabilities are supported by the server.
+
+ Capability strings beginning with "vnd." represent vendor-defined
+ extensions. Such extensions are not defined by Internet standards or
+ RFCs, but are still registered with IANA in order to prevent
+ conflicts. Extensions starting with "vnd." SHOULD be followed by the
+ name of the vendor and product, such as "vnd.acme.rocket-sled".
+
+ The following capability strings are defined by this document:
+
+ envelope The string "envelope" indicates that the implementation
+ supports the "envelope" command.
+
+ fileinto The string "fileinto" indicates that the implementation
+ supports the "fileinto" command.
+
+ reject The string "reject" indicates that the implementation
+ supports the "reject" command.
+
+ comparator- The string "comparator-elbonia" is provided if the
+ implementation supports the "elbonia" comparator.
+ Therefore, all implementations have at least the
+ "comparator-i;octet" and "comparator-i;ascii-casemap"
+ capabilities. However, these comparators may be used
+ without being declared with require.
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 27]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+6.2. IANA Considerations
+
+ In order to provide a standard set of extensions, a registry is
+ provided by IANA. Capability names may be registered on a first-
+ come, first-served basis. Extensions designed for interoperable use
+ SHOULD be defined as standards track or IESG approved experimental
+ RFCs.
+
+6.2.1. Template for Capability Registrations
+
+ The following template is to be used for registering new Sieve
+ extensions with IANA.
+
+ To: iana@iana.org
+ Subject: Registration of new Sieve extension
+
+ Capability name:
+ Capability keyword:
+ Capability arguments:
+ Standards Track/IESG-approved experimental RFC number:
+ Person and email address to contact for further information:
+
+6.2.2. Initial Capability Registrations
+
+ The following are to be added to the IANA registry for Sieve
+ extensions as the initial contents of the capability registry.
+
+ Capability name: fileinto
+ Capability keyword: fileinto
+ Capability arguments: fileinto <folder: string>
+ Standards Track/IESG-approved experimental RFC number:
+ RFC 3028 (Sieve base spec)
+ Person and email address to contact for further information:
+ Tim Showalter
+ tjs@mirapoint.com
+
+ Capability name: reject
+ Capability keyword: reject
+ Capability arguments: reject <reason: string>
+ Standards Track/IESG-approved experimental RFC number:
+ RFC 3028 (Sieve base spec)
+ Person and email address to contact for further information:
+ Tim Showalter
+ tjs@mirapoint.com
+
+
+
+
+
+
+
+Showalter Standards Track [Page 28]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Capability name: envelope
+ Capability keyword: envelope
+ Capability arguments:
+ envelope [COMPARATOR] [ADDRESS-PART] [MATCH-TYPE]
+ <envelope-part: string-list> <key-list: string-list>
+ Standards Track/IESG-approved experimental RFC number:
+ RFC 3028 (Sieve base spec)
+ Person and email address to contact for further information:
+ Tim Showalter
+ tjs@mirapoint.com
+
+ Capability name: comparator-*
+ Capability keyword:
+ comparator-* (anything starting with "comparator-")
+ Capability arguments: (none)
+ Standards Track/IESG-approved experimental RFC number:
+ RFC 3028, Sieve, by reference of
+ RFC 2244, Application Configuration Access Protocol
+ Person and email address to contact for further information:
+ Tim Showalter
+ tjs@mirapoint.com
+
+6.3. Capability Transport
+
+ As the range of mail systems that this document is intended to apply
+ to is quite varied, a method of advertising which capabilities an
+ implementation supports is difficult due to the wide range of
+ possible implementations. Such a mechanism, however, should have
+ property that the implementation can advertise the complete set of
+ extensions that it supports.
+
+7. Transmission
+
+ The MIME type for a Sieve script is "application/sieve".
+
+ The registration of this type for RFC 2048 requirements is as
+ follows:
+
+ Subject: Registration of MIME media type application/sieve
+
+ MIME media type name: application
+ MIME subtype name: sieve
+ Required parameters: none
+ Optional parameters: none
+ Encoding considerations: Most sieve scripts will be textual,
+ written in UTF-8. When non-7bit characters are used,
+ quoted-printable is appropriate for transport systems
+ that require 7bit encoding.
+
+
+
+Showalter Standards Track [Page 29]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ Security considerations: Discussed in section 10 of RFC 3028.
+ Interoperability considerations: Discussed in section 2.10.5
+ of RFC 3028.
+ Published specification: RFC 3028.
+ Applications which use this media type: sieve-enabled mail servers
+ Additional information:
+ Magic number(s):
+ File extension(s): .siv
+ Macintosh File Type Code(s):
+ Person & email address to contact for further information:
+ See the discussion list at ietf-mta-filters@imc.org.
+ Intended usage:
+ COMMON
+ Author/Change controller:
+ See Author information in RFC 3028.
+
+8. Parsing
+
+ The Sieve grammar is separated into tokens and a separate grammar as
+ most programming languages are.
+
+8.1. Lexical Tokens
+
+ Sieve scripts are encoded in UTF-8. The following assumes a valid
+ UTF-8 encoding; special characters in Sieve scripts are all ASCII.
+
+ The following are tokens in Sieve:
+
+ - identifiers
+ - tags
+ - numbers
+ - quoted strings
+ - multi-line strings
+ - other separators
+
+ Blanks, horizontal tabs, CRLFs, and comments ("white space") are
+ ignored except as they separate tokens. Some white space is required
+ to separate otherwise adjacent tokens and in specific places in the
+ multi-line strings.
+
+ The other separators are single individual characters, and are
+ mentioned explicitly in the grammar.
+
+ The lexical structure of sieve is defined in the following BNF (as
+ described in [ABNF]):
+
+
+
+
+
+
+Showalter Standards Track [Page 30]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ bracket-comment = "/*" *(CHAR-NOT-STAR / ("*" CHAR-NOT-SLASH)) "*/"
+ ;; No */ allowed inside a comment.
+ ;; (No * is allowed unless it is the last character,
+ ;; or unless it is followed by a character that isn't a
+ ;; slash.)
+
+ CHAR-NOT-DOT = (%x01-09 / %x0b-0c / %x0e-2d / %x2f-ff)
+ ;; no dots, no CRLFs
+
+ CHAR-NOT-CRLF = (%x01-09 / %x0b-0c / %x0e-ff)
+
+ CHAR-NOT-SLASH = (%x00-57 / %x58-ff)
+
+ CHAR-NOT-STAR = (%x00-51 / %x53-ff)
+
+ comment = bracket-comment / hash-comment
+
+ hash-comment = ( "#" *CHAR-NOT-CRLF CRLF )
+
+ identifier = (ALPHA / "_") *(ALPHA DIGIT "_")
+
+ tag = ":" identifier
+
+ number = 1*DIGIT [QUANTIFIER]
+
+ QUANTIFIER = "K" / "M" / "G"
+
+ quoted-string = DQUOTE *CHAR DQUOTE
+ ;; in general, \ CHAR inside a string maps to CHAR
+ ;; so \" maps to " and \\ maps to \
+ ;; note that newlines and other characters are all allowed
+ ;; strings
+
+ multi-line = "text:" *(SP / HTAB) (hash-comment / CRLF)
+ *(multi-line-literal / multi-line-dotstuff)
+ "." CRLF
+ multi-line-literal = [CHAR-NOT-DOT *CHAR-NOT-CRLF] CRLF
+ multi-line-dotstuff = "." 1*CHAR-NOT-CRLF CRLF
+ ;; A line containing only "." ends the multi-line.
+ ;; Remove a leading '.' if followed by another '.'.
+
+ white-space = 1*(SP / CRLF / HTAB) / comment
+
+8.2. Grammar
+
+ The following is the grammar of Sieve after it has been lexically
+ interpreted. No white space or comments appear below. The start
+ symbol is "start".
+
+
+
+Showalter Standards Track [Page 31]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ argument = string-list / number / tag
+
+ arguments = *argument [test / test-list]
+
+ block = "{" commands "}"
+
+ command = identifier arguments ( ";" / block )
+
+ commands = *command
+
+ start = commands
+
+ string = quoted-string / multi-line
+
+ string-list = "[" string *("," string) "]" / string ;; if
+ there is only a single string, the brackets are optional
+
+ test = identifier arguments
+
+ test-list = "(" test *("," test) ")"
+
+9. Extended Example
+
+ The following is an extended example of a Sieve script. Note that it
+ does not make use of the implicit keep.
+
+ #
+ # Example Sieve Filter
+ # Declare any optional features or extension used by the script
+ #
+ require ["fileinto", "reject"];
+
+ #
+ # Reject any large messages (note that the four leading dots get
+ # "stuffed" to three)
+ #
+ if size :over 1M
+ {
+ reject text:
+ Please do not send me large attachments.
+ Put your file on a server and send me the URL.
+ Thank you.
+ .... Fred
+ .
+ ;
+ stop;
+ }
+ #
+
+
+
+Showalter Standards Track [Page 32]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ # Handle messages from known mailing lists
+ # Move messages from IETF filter discussion list to filter folder
+ #
+ if header :is "Sender" "owner-ietf-mta-filters@imc.org"
+ {
+ fileinto "filter"; # move to "filter" folder
+ }
+ #
+ # Keep all messages to or from people in my company
+ #
+ elsif address :domain :is ["From", "To"] "example.com"
+ {
+ keep; # keep in "In" folder
+ }
+
+ #
+ # Try and catch unsolicited email. If a message is not to me,
+ # or it contains a subject known to be spam, file it away.
+ #
+ elsif anyof (not address :all :contains
+ ["To", "Cc", "Bcc"] "me@example.com",
+ header :matches "subject"
+ ["*make*money*fast*", "*university*dipl*mas*"])
+ {
+ # If message header does not contain my address,
+ # it's from a list.
+ fileinto "spam"; # move to "spam" folder
+ }
+ else
+ {
+ # Move all other (non-company) mail to "personal"
+ # folder.
+ fileinto "personal";
+ }
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 33]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+10. Security Considerations
+
+ Users must get their mail. It is imperative that whatever method
+ implementations use to store the user-defined filtering scripts be
+ secure.
+
+ It is equally important that implementations sanity-check the user's
+ scripts, and not allow users to create on-demand mailbombs. For
+ instance, an implementation that allows a user to reject or redirect
+ multiple times to a single message might also allow a user to create
+ a mailbomb triggered by mail from a specific user. Site- or
+ implementation-defined limits on actions are useful for this.
+
+ Several commands, such as "discard", "redirect", and "fileinto" allow
+ for actions to be taken that are potentially very dangerous.
+
+ Implementations SHOULD take measures to prevent languages from
+ looping.
+
+11. Acknowledgments
+
+ I am very thankful to Chris Newman for his support and his ABNF
+ syntax checker, to John Myers and Steve Hole for outlining the
+ requirements for the original drafts, to Larry Greenfield for nagging
+ me about the grammar and finally fixing it, to Greg Sereda for
+ repeatedly fixing and providing examples, to Ned Freed for fixing
+ everything else, to Rob Earhart for an early implementation and a
+ great deal of help, and to Randall Gellens for endless amounts of
+ proofreading. I am grateful to Carnegie Mellon University where most
+ of the work on this document was done. I am also indebted to all of
+ the readers of the ietf-mta-filters@imc.org mailing list.
+
+12. Author's Address
+
+ Tim Showalter
+ Mirapoint, Inc.
+ 909 Hermosa Court
+ Sunnyvale, CA 94085
+
+ EMail: tjs@mirapoint.com
+
+13. References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+
+
+
+
+
+Showalter Standards Track [Page 34]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+ [ACAP] Newman, C. and J. G. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November 1997.
+
+ [BINARY-SI] "Standard IEC 60027-2: Letter symbols to be used in
+ electrical technology - Part 2: Telecommunications and
+ electronics", January 1999.
+
+ [DSN] Moore, K. and G. Vaudreuil, "An Extensible Message Format
+ for Delivery Status Notifications", RFC 1894, January
+ 1996.
+
+ [FLAMES] Borenstein, N, and C. Thyberg, "Power, Ease of Use, and
+ Cooperative Work in a Practical Multimedia Message
+ System", Int. J. of Man-Machine Studies, April, 1991.
+ Reprinted in Computer-Supported Cooperative Work and
+ Groupware, Saul Greenberg, editor, Harcourt Brace
+ Jovanovich, 1991. Reprinted in Readings in Groupware and
+ Computer-Supported Cooperative Work, Ronald Baecker,
+ editor, Morgan Kaufmann, 1993.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - version
+ 4rev1", RFC 2060, December 1996.
+
+ [IMAIL] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822, August 1982.
+
+ [MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [MDN] Fajman, R., "An Extensible Message Format for Message
+ Disposition Notifications", RFC 2298, March 1998.
+
+ [RFC1123] Braden, R., "Requirements for Internet Hosts --
+ Application and Support", STD 3, RFC 1123, November 1989.
+
+ [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
+ 821, August 1982.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of Unicode
+ and ISO 10646", RFC 2044, October 1996.
+
+
+
+
+
+
+
+Showalter Standards Track [Page 35]
+
+RFC 3028 Sieve: A Mail Filtering Language January 2001
+
+
+14. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2001). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 36]
+
diff --git a/rfc/sieve/rfc3431.txt b/rfc/sieve/rfc3431.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group W. Segmuller
+Request for Comment: 3431 IBM T.J. Watson Research Center
+Category: Standards Track December 2002
+
+
+ Sieve Extension: Relational Tests
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+Abstract
+
+ This document describes the RELATIONAL extension to the Sieve mail
+ filtering language defined in RFC 3028. This extension extends
+ existing conditional tests in Sieve to allow relational operators.
+ In addition to testing their content, it also allows for testing of
+ the number of entities in header and envelope fields.
+
+1 Introduction
+
+ Sieve [SIEVE] is a language for filtering e-mail messages at the time
+ of final delivery. It is designed to be implementable on either a
+ mail client or mail server. It is meant to be extensible, simple,
+ and independent of access protocol, mail architecture, and operating
+ system. It is suitable for running on a mail server where users may
+ not be allowed to execute arbitrary programs, such as on black box
+ Internet Messages Access Protocol (IMAP) servers, as it has no
+ variables, loops, nor the ability to shell out to external programs.
+
+ The RELATIONAL extension provides relational operators on the
+ address, envelope, and header tests. This extension also provides a
+ way of counting the entities in a message header or address field.
+
+ With this extension, the sieve script may now determine if a field is
+ greater than or less than a value instead of just equivalent. One
+ use is for the x-priority field: move messages with a priority
+ greater than 3 to the "work on later" folder. Mail could also be
+ sorted by the from address. Those userids that start with 'a'-'m' go
+ to one folder, and the rest go to another folder.
+
+
+
+Segmuller Standards Track [Page 1]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+ The sieve script can also determine the number of fields in the
+ header, or the number of addresses in a recipient field. For
+ example: are there more than 5 addresses in the to and cc fields.
+
+2 Conventions used in this document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in BCP 14, RFC 2119.
+
+ Conventions for notations are as in [SIEVE] section 1.1, including
+ the use of [KEYWORDS] and "Syntax:" label for the definition of
+ action and tagged arguments syntax, and the use of [ABNF].
+
+ The capability string associated with extension defined in this
+ document is "relational".
+
+3 Comparators
+
+ This document does not define any comparators or exempt any
+ comparators from the require clause. Any comparator used, other than
+ "i;octet" and "i;ascii-casemap", MUST be declared a require clause as
+ defined in [SIEVE].
+
+ The "i;ascii-numeric" comparator, as defined in [ACAP], MUST be
+ supported for any implementation of this extension. The comparator
+ "i;ascii-numeric" MUST support at least 32 bit unsigned integers.
+
+ Larger integers MAY be supported. Note: the "i;ascii-numeric"
+ comparator does not support negative numbers.
+
+4 Match Type
+
+ This document defines two new match types. They are the VALUE match
+ type and the COUNT match type.
+
+ The syntax is:
+
+ MATCH-TYPE =/ COUNT / VALUE
+
+ COUNT = ":count" relational-match
+
+ VALUE = ":value" relational-match
+
+ relational-match = DQUOTE ( "gt" / "ge" / "lt"
+ / "le" / "eq" / "ne" ) DQUOTE
+
+
+
+
+
+Segmuller Standards Track [Page 2]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+4.1 Match Type Value
+
+ The VALUE match type does a relational comparison between strings.
+
+ The VALUE match type may be used with any comparator which returns
+ sort information.
+
+ Leading and trailing white space MUST be removed from the value of
+ the message for the comparison. White space is defined as
+
+ SP / HTAB / CRLF
+
+ A value from the message is considered the left side of the relation.
+ A value from the test expression, the key-list for address, envelope,
+ and header tests, is the right side of the relation.
+
+ If there are multiple values on either side or both sides, the test
+ is considered true, if any pair is true.
+
+4.2 Match Type Count
+
+ The COUNT match type first determines the number of the specified
+ entities in the message and does a relational comparison of the
+ number of entities to the values specified in the test expression.
+
+ The COUNT match type SHOULD only be used with numeric comparators.
+
+ The Address Test counts the number of recipients in the specified
+ fields. Group names are ignored.
+
+ The Envelope Test counts the number of recipients in the specified
+ envelope parts. The envelope "to" will always have only one entry,
+ which is the address of the user for whom the sieve script is
+ running. There is no way a sieve script can determine if the message
+ was actually sent to someone else using this test. The envelope
+ "from" will be 0 if the MAIL FROM is blank, or 1 if MAIL FROM is not
+ blank.
+
+ The Header Test counts the total number of instances of the specified
+ fields. This does not count individual addresses in the "to", "cc",
+ and other recipient fields.
+
+ In all cases, if more than one field name is specified, the counts
+ for all specified fields are added together to obtain the number for
+ comparison. Thus, specifying ["to", "cc"] in an address COUNT test,
+ comparing the total number of "to" and "cc" addresses; if separate
+ counts are desired, they must be done in two comparisons, perhaps
+ joined by "allof" or "anyof".
+
+
+
+Segmuller Standards Track [Page 3]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+5 Security Considerations
+
+ Security considerations are discussed in [SIEVE].
+
+ An implementation MUST ensure that the test for envelope "to" only
+ reflects the delivery to the current user. It MUST not be possible
+ for a user to determine if this message was delivered to someone else
+ using this test.
+
+6 Example
+
+ Using the message:
+
+ received: ...
+ received: ...
+ subject: example
+ to: foo@example.com.invalid, baz@example.com.invalid
+ cc: qux@example.com.invalid
+
+ The test:
+
+ address :count "ge" :comparator "i;ascii-numeric" ["to", "cc"]
+ ["3"]
+
+ would be true and the test
+
+ anyof ( address :count "ge" :comparator "i;ascii-numeric"
+ ["to"] ["3"],
+ address :count "ge" :comparator "i;ascii-numeric"
+ ["cc"] ["3"] )
+
+ would be false.
+
+ To check the number of received fields in the header, the
+ following test may be used:
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["received"] ["3"]
+
+ This would return false. But
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["received", "subject"] ["3"]
+
+ would return true.
+
+
+
+
+
+
+Segmuller Standards Track [Page 4]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+ The test:
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["to", "cc"] ["3"]
+
+ will always return false on an RFC 2822 compliant message [RFC2822],
+ since a message can have at most one "to" field and at most one "cc"
+ field. This test counts the number of fields, not the number of
+ addresses.
+
+7 Extended Example
+
+ require ["relational", "comparator-i;ascii-numeric"];
+
+ if header :value "lt" :comparator "i;ascii-numeric"
+ ["x-priority"] ["3"]
+ {
+ fileinto "Priority";
+ }
+
+ elseif address :count "gt" :comparator "i;ascii-numeric"
+ ["to"] ["5"]
+ {
+ # everything with more than 5 recipients in the "to" field
+ # is considered SPAM
+ fileinto "SPAM";
+ }
+
+ elseif address :value "gt" :all :comparator "i;ascii-casemap"
+ ["from"] ["M"]
+ {
+ fileinto "From N-Z";
+ } else {
+ fileinto "From A-M";
+ }
+
+ if allof ( address :count "eq" :comparator "i;ascii-numeric"
+ ["to", "cc"] ["1"] ,
+ address :all :comparator "i;ascii-casemap"
+ ["to", "cc"] ["me@foo.example.com.invalid"]
+ {
+ fileinto "Only me";
+ }
+
+
+
+
+
+
+
+
+Segmuller Standards Track [Page 5]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+8 IANA Considerations
+
+ The following template specifies the IANA registration of the Sieve
+ extension specified in this document:
+
+ To: iana@iana.org
+ Subject: Registration of new Sieve extension
+
+ Capability name: RELATIONAL
+ Capability keyword: relational
+ Capability arguments: N/A
+ Standards Track/IESG-approved experimental RFC number: this RFC
+ Person and email address to contact for further information:
+ Wolfgang Segmuller
+ IBM T.J. Watson Research Center
+ 30 Saw Mill River Rd
+ Hawthorne, NY 10532
+
+ Email: whs@watson.ibm.com
+
+ This information should be added to the list of sieve extensions
+ given on http://www.iana.org/assignments/sieve-extensions.
+
+9 References
+
+9.1 Normative References
+
+ [SIEVE] Showalter, T., "Sieve: A Mail Filtering Language", RFC
+ 3028, January 2001.
+
+ [Keywords] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [ABNF] Crocker, D., "Augmented BNF for Syntax Specifications:
+ ABNF", RFC 2234, November 1997.
+
+ [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
+ 2001.
+
+9.2 Non-Normative References
+
+ [ACAP] Newman, C. and J. G. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November 1997.
+
+
+
+
+
+
+
+
+Segmuller Standards Track [Page 6]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+10 Author's Address
+
+ Wolfgang Segmuller
+ IBM T.J. Watson Research Center
+ 30 Saw Mill River Rd
+ Hawthorne, NY 10532
+
+ EMail: whs@watson.ibm.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Segmuller Standards Track [Page 7]
+
+RFC 3431 Sieve Extension: Relational Tests December 2002
+
+
+11 Full Copyright Statement
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Segmuller Standards Track [Page 8]
+
diff --git a/rfc/sieve/rfc5231.txt b/rfc/sieve/rfc5231.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group W. Segmuller
+Request for Comments: 5231 B. Leiba
+Obsoletes: 3431 IBM T.J. Watson Research Center
+Category: Standards Track January 2008
+
+
+ Sieve Email Filtering: Relational Extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document describes the RELATIONAL extension to the Sieve mail
+ filtering language defined in RFC 3028. This extension extends
+ existing conditional tests in Sieve to allow relational operators.
+ In addition to testing their content, it also allows for testing of
+ the number of entities in header and envelope fields.
+
+ This document obsoletes RFC 3431.
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Conventions Used in This Document . . . . . . . . . . . . . . . 2
+ 3. Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 4. Match Types . . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 4.1. Match Type VALUE . . . . . . . . . . . . . . . . . . . . . 3
+ 4.2. Match Type COUNT . . . . . . . . . . . . . . . . . . . . . 3
+ 5. Interaction with Other Sieve Actions . . . . . . . . . . . . . 4
+ 6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 7. Extended Example . . . . . . . . . . . . . . . . . . . . . . . 6
+ 8. Changes since RFC 3431 . . . . . . . . . . . . . . . . . . . . 6
+ 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
+ 10. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
+ 11. Normative References . . . . . . . . . . . . . . . . . . . . . 7
+
+
+
+
+
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 1]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+1. Introduction
+
+ The RELATIONAL extension to the Sieve mail filtering language [Sieve]
+ provides relational operators on the address, envelope, and header
+ tests. This extension also provides a way of counting the entities
+ in a message header or address field.
+
+ With this extension, the Sieve script may now determine if a field is
+ greater than or less than a value instead of just equivalent. One
+ use is for the x-priority field: move messages with a priority
+ greater than 3 to the "work on later" folder. Mail could also be
+ sorted by the from address. Those userids that start with 'a'-'m' go
+ to one folder, and the rest go to another folder.
+
+ The Sieve script can also determine the number of fields in the
+ header, or the number of addresses in a recipient field, for example,
+ whether there are more than 5 addresses in the to and cc fields.
+
+ The capability string associated with the extension defined in this
+ document is "relational".
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in BCP 14, RFC 2119.
+
+ Conventions for notations are as in [Sieve] section 1.1, including
+ the use of [Kwds] and the use of [ABNF].
+
+3. Comparators
+
+ This document does not define any comparators or exempt any
+ comparators from the require clause. Any comparator used must be
+ treated as defined in [Sieve].
+
+ The "i;ascii-numeric" comparator, as defined in [RFC4790], MUST be
+ supported for any implementation of this extension. The comparator
+ "i;ascii-numeric" MUST support at least 32-bit unsigned integers.
+
+ Larger integers MAY be supported. Note: the "i;ascii-numeric"
+ comparator does not support negative numbers.
+
+
+
+
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 2]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+4. Match Types
+
+ This document defines two new match types. They are the VALUE match
+ type and the COUNT match type.
+
+ The syntax is:
+
+ MATCH-TYPE =/ COUNT / VALUE
+
+ COUNT = ":count" relational-match
+
+ VALUE = ":value" relational-match
+
+ relational-match = DQUOTE
+ ("gt" / "ge" / "lt" / "le" / "eq" / "ne") DQUOTE
+ ; "gt" means "greater than", the C operator ">".
+ ; "ge" means "greater than or equal", the C operator ">=".
+ ; "lt" means "less than", the C operator "<".
+ ; "le" means "less than or equal", the C operator "<=".
+ ; "eq" means "equal to", the C operator "==".
+ ; "ne" means "not equal to", the C operator "!=".
+
+4.1. Match Type VALUE
+
+ The VALUE match type does a relational comparison between strings.
+
+ The VALUE match type may be used with any comparator that returns
+ sort information.
+
+ A value from the message is considered the left side of the relation.
+ A value from the test expression, the key-list for address, envelope,
+ and header tests, is the right side of the relation.
+
+ If there are multiple values on either side or both sides, the test
+ is considered true if any pair is true.
+
+4.2. Match Type COUNT
+
+ The COUNT match type first determines the number of the specified
+ entities in the message and does a relational comparison of the
+ number of entities, as defined below, to the values specified in the
+ test expression.
+
+ The COUNT match type SHOULD only be used with numeric comparators.
+
+ The Address Test counts the number of addresses (the number of
+ "mailbox" elements, as defined in [RFC2822]) in the specified fields.
+ Group names are ignored, but the contained mailboxes are counted.
+
+
+
+Segmuller & Leiba Standards Track [Page 3]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+ The Envelope Test counts the number of addresses in the specified
+ envelope parts. The envelope "to" will always have only one entry,
+ which is the address of the user for whom the Sieve script is
+ running. Using this test, there is no way a Sieve script can
+ determine if the message was actually sent to someone else. The
+ envelope "from" will be 0 if the MAIL FROM is empty, or 1 if MAIL
+ FROM is not empty.
+
+ The Header Test counts the total number of instances of the specified
+ fields. This does not count individual addresses in the "to", "cc",
+ and other recipient fields.
+
+ In all cases, if more than one field name is specified, the counts
+ for all specified fields are added together to obtain the number for
+ comparison. Thus, specifying ["to", "cc"] in an address COUNT test
+ compares the total number of "to" and "cc" addresses; if separate
+ counts are desired, they must be done in two comparisons, perhaps
+ joined by "allof" or "anyof".
+
+5. Interaction with Other Sieve Actions
+
+ This specification adds two match types. The VALUE match type only
+ works with comparators that return sort information. The COUNT match
+ type only makes sense with numeric comparators.
+
+ There is no interaction with any other Sieve operations, nor with any
+ known extensions. In particular, this specification has no effect on
+ implicit KEEP, nor on any explicit message actions.
+
+6. Example
+
+ Using the message:
+
+ received: ...
+ received: ...
+ subject: example
+ to: foo@example.com, baz@example.com
+ cc: qux@example.com
+
+ The test:
+
+ address :count "ge" :comparator "i;ascii-numeric"
+ ["to", "cc"] ["3"]
+
+ would evaluate to true, and the test
+
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 4]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+ anyof ( address :count "ge" :comparator "i;ascii-numeric"
+ ["to"] ["3"],
+ address :count "ge" :comparator "i;ascii-numeric"
+ ["cc"] ["3"] )
+
+ would evaluate to false.
+
+ To check the number of received fields in the header, the following
+ test may be used:
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["received"] ["3"]
+
+ This would evaluate to false. But
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["received", "subject"] ["3"]
+
+ would evaluate to true.
+
+ The test:
+
+ header :count "ge" :comparator "i;ascii-numeric"
+ ["to", "cc"] ["3"]
+
+ will always evaluate to false on an RFC 2822 compliant message
+ [RFC2822], since a message can have at most one "to" field and at
+ most one "cc" field. This test counts the number of fields, not the
+ number of addresses.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 5]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+7. Extended Example
+
+ require ["relational", "comparator-i;ascii-numeric", "fileinto"];
+
+ if header :value "lt" :comparator "i;ascii-numeric"
+ ["x-priority"] ["3"]
+ {
+ fileinto "Priority";
+ }
+
+ elsif address :count "gt" :comparator "i;ascii-numeric"
+ ["to"] ["5"]
+ {
+ # everything with more than 5 recipients in the "to" field
+ # is considered SPAM
+ fileinto "SPAM";
+ }
+
+ elsif address :value "gt" :all :comparator "i;ascii-casemap"
+ ["from"] ["M"]
+ {
+ fileinto "From N-Z";
+ } else {
+ fileinto "From A-M";
+ }
+
+ if allof ( address :count "eq" :comparator "i;ascii-numeric"
+ ["to", "cc"] ["1"] ,
+ address :all :comparator "i;ascii-casemap"
+ ["to", "cc"] ["me@foo.example.com"] )
+ {
+ fileinto "Only me";
+ }
+
+8. Changes since RFC 3431
+
+ Apart from several minor editorial/wording changes, the following
+ list describes the notable changes to this specification since RFC
+ 3431.
+
+ o Updated references, including changing the comparator reference
+ from the Application Configuration Access Protocol (ACAP) to the
+ "Internet Application Protocol Collation Registry" document
+ [RFC4790].
+
+ o Updated and corrected the examples.
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 6]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+ o Added definition comments to ABNF for "gt", "lt", etc.
+
+ o Clarified what RFC 2822 elements are counted in the COUNT test.
+
+ o Removed the requirement to strip white space from header fields
+ before comparing; a more general version of this requirement has
+ been added to the Sieve base spec.
+
+9. IANA Considerations
+
+ The following template specifies the IANA registration of the
+ relational Sieve extension specified in this document:
+
+ To: iana@iana.org
+ Subject: Registration of new Sieve extension
+
+ Capability name: relational
+ Description: Extends existing conditional tests in Sieve language
+ to allow relational operators
+ RFC number: RFC 5231
+ Contact address: The Sieve discussion list <ietf-mta-filters@imc.org>
+
+10. Security Considerations
+
+ An implementation MUST ensure that the test for envelope "to" only
+ reflects the delivery to the current user. Using this test, it MUST
+ not be possible for a user to determine if this message was delivered
+ to someone else.
+
+ Additional security considerations are discussed in [Sieve].
+
+11. Normative References
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [Kwds] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, March 1997.
+
+ [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
+ April 2001.
+
+ [RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet
+ Application Protocol Collation Registry", RFC 4790,
+ March 2007.
+
+ [Sieve] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
+ Filtering Language", RFC 5228, January 2008.
+
+
+
+Segmuller & Leiba Standards Track [Page 7]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+Authors' Addresses
+
+ Wolfgang Segmuller
+ IBM T.J. Watson Research Center
+ 19 Skyline Drive
+ Hawthorne, NY 10532
+ US
+
+ Phone: +1 914 784 7408
+ EMail: werewolf@us.ibm.com
+
+
+ Barry Leiba
+ IBM T.J. Watson Research Center
+ 19 Skyline Drive
+ Hawthorne, NY 10532
+ US
+
+ Phone: +1 914 784 7941
+ EMail: leiba@watson.ibm.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Segmuller & Leiba Standards Track [Page 8]
+
+RFC 5231 Sieve: Relational Extension January 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
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+
+Network Working Group N. Freed
+Request for Comments: 5260 Sun Microsystems
+Category: Standards Track July 2008
+
+
+ Sieve Email Filtering: Date and Index Extensions
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document describes the "date" and "index" extensions to the
+ Sieve email filtering language. The "date" extension gives Sieve the
+ ability to test date and time values in various ways. The "index"
+ extension provides a means to limit header and address tests to
+ specific instances of header fields when header fields are repeated.
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Conventions Used in This Document . . . . . . . . . . . . . . 2
+ 3. Capability Identifiers . . . . . . . . . . . . . . . . . . . . 3
+ 4. Date Test . . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 4.1. Zone and Originalzone Arguments . . . . . . . . . . . . . 4
+ 4.2. Date-part Argument . . . . . . . . . . . . . . . . . . . . 4
+ 4.3. Comparator Interactions with Date-part Arguments . . . . . 5
+ 4.4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
+ 5. Currentdate Test . . . . . . . . . . . . . . . . . . . . . . . 6
+ 5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
+ 6. Index Extension . . . . . . . . . . . . . . . . . . . . . . . 7
+ 6.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
+ 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
+ 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
+ 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
+ 9.2. Informative References . . . . . . . . . . . . . . . . . . 10
+ Appendix A. Julian Date Conversions . . . . . . . . . . . . . . . 11
+ Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 12
+
+
+
+
+
+
+
+Freed Standards Track [Page 1]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+1. Introduction
+
+ Sieve [RFC5228] is a language for filtering email messages at or
+ around the time of final delivery. It is designed to be
+ implementable on either a mail client or mail server. It is meant to
+ be extensible, simple, and independent of access protocol, mail
+ architecture, and operating system. It is suitable for running on a
+ mail server where users may not be allowed to execute arbitrary
+ programs, such as on black box Internet Message Access Protocol
+ [RFC3501] servers, as it does not have user-controlled loops or the
+ ability to run external programs.
+
+ The "date" extension provides a new date test to extract and match
+ date/time information from structured header fields. The date test
+ is similar in concept to the address test specified in [RFC5228],
+ which performs similar operations on addresses in header fields.
+
+ The "date" extension also provides a currentdate test that operates
+ on the date and time when the Sieve script is executed.
+
+ Some header fields containing date/time information, e.g., Received:,
+ naturally occur more than once in a single header. In such cases it
+ is useful to be able to restrict the date test to some subset of the
+ fields that are present. For example, it may be useful to apply a
+ date test to the last (earliest) Received: field. Additionally, it
+ may also be useful to apply similar restrictions to either the header
+ or address tests specified in [RFC5228].
+
+ For this reason, this specification also defines an "index"
+ extension. This extension adds two additional tagged arguments
+ :index and :last to the header, address, and date tests. If present,
+ these arguments specify which occurrence of the named header field is
+ to be tested.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [RFC2119].
+
+ The terms used to describe the various components of the Sieve
+ language are taken from Section 1.1 of [RFC5228]. Section 2 of the
+ same document describes basic Sieve language syntax and semantics.
+ The date-time syntactic element defined using ABNF notation [RFC5234]
+ in [RFC3339] is also used here.
+
+
+
+
+
+
+Freed Standards Track [Page 2]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+3. Capability Identifiers
+
+ The capability strings associated with the two extensions defined in
+ this document are "date" and "index".
+
+4. Date Test
+
+ Usage: date [<":zone" <time-zone: string>> / ":originalzone"]
+ [COMPARATOR] [MATCH-TYPE] <header-name: string>
+ <date-part: string> <key-list: string-list>
+
+ The date test matches date/time information derived from headers
+ containing [RFC2822] date-time values. The date/time information is
+ extracted from the header, shifted to the specified time zone, and
+ the value of the given date-part is determined. The test returns
+ true if the resulting string matches any of the strings specified in
+ the key-list, as controlled by the comparator and match keywords.
+ The date test returns false unconditionally if the specified header
+ field does not exist, the field exists but does not contain a
+ syntactically valid date-time specification, the date-time isn't
+ valid according to the rules of the calendar system (e.g., January
+ 32nd, February 29 in a non-leap year), or the resulting string fails
+ to match any key-list value.
+
+ The type of match defaults to ":is" and the default comparator is
+ "i;ascii-casemap".
+
+ Unlike the header and address tests, the date test can only be
+ applied to a single header field at a time. If multiple header
+ fields with the same name are present, only the first field that is
+ found is used. (Note, however, that this behavior can be modified
+ with the "index" extension defined below.) These restrictions
+ simplify the test and keep the meaning clear.
+
+ The "relational" extension [RFC5231] adds a match type called
+ ":count". The count of a date test is 1 if the specified field
+ exists and contains a valid date; 0, otherwise.
+
+ Implementations MUST support extraction of RFC 2822 date-time
+ information that either makes up the entire header field (e.g., as it
+ does in a standard Date: header field) or appears at the end of a
+ header field following a semicolon (e.g., as it does in a standard
+ Received: header field). Implementations MAY support extraction of
+ date and time information in RFC2822 or other formats that appears in
+ other positions in header field content. In the case of a field
+ containing more than one date or time value, the last one that
+ appears SHOULD be used.
+
+
+
+
+Freed Standards Track [Page 3]
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+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+4.1. Zone and Originalzone Arguments
+
+ The :originalzone argument specifies that the time zone offset
+ originally in the extracted date-time value should be retained. The
+ :zone argument specifies a specific time zone offset that the date-
+ time value is to be shifted to prior to testing. It is an error to
+ specify both :zone and :originalzone.
+
+ The value of time-zone MUST be an offset relative to UTC with the
+ following syntax:
+
+ time-zone = ( "+" / "-" ) 4DIGIT
+
+ The "+" or "-" indicates whether the time-of-day is ahead of (i.e.,
+ east of) or behind (i.e., west of) UTC. The first two digits
+ indicate the number of hours difference from Universal Time, and the
+ last two digits indicate the number of minutes difference from
+ Universal Time. Note that this agrees with the RFC 2822 format for
+ time zone offsets, not the ISO 8601 format.
+
+ If both the :zone and :originalzone arguments are omitted, the local
+ time zone MUST be used.
+
+4.2. Date-part Argument
+
+ The date-part argument specifies a particular part of the resulting
+ date/time value to match against the key-list. Possible case-
+ insensitive values are:
+
+ "year" => the year, "0000" .. "9999".
+ "month" => the month, "01" .. "12".
+ "day" => the day, "01" .. "31".
+ "date" => the date in "yyyy-mm-dd" format.
+ "julian" => the Modified Julian Day, that is, the date
+ expressed as an integer number of days since
+ 00:00 UTC on November 17, 1858 (using the Gregorian
+ calendar). This corresponds to the regular
+ Julian Day minus 2400000.5. Sample routines to
+ convert to and from modified Julian dates are
+ given in Appendix A.
+ "hour" => the hour, "00" .. "23".
+ "minute" => the minute, "00" .. "59".
+ "second" => the second, "00" .. "60".
+ "time" => the time in "hh:mm:ss" format.
+ "iso8601" => the date and time in restricted ISO 8601 format.
+ "std11" => the date and time in a format appropriate
+ for use in a Date: header field [RFC2822].
+
+
+
+
+Freed Standards Track [Page 4]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+ "zone" => the time zone in use. If the user specified a
+ time zone with ":zone", "zone" will
+ contain that value. If :originalzone is specified
+ this value will be the original zone specified
+ in the date-time value. If neither argument is
+ specified the value will be the server's default
+ time zone in offset format "+hhmm" or "-hhmm". An
+ offset of 0 (Zulu) always has a positive sign.
+ "weekday" => the day of the week expressed as an integer between
+ "0" and "6". "0" is Sunday, "1" is Monday, etc.
+
+ The restricted ISO 8601 format is specified by the date-time ABNF
+ production given in [RFC3339], Section 5.6, with the added
+ restrictions that the letters "T" and "Z" MUST be in upper case, and
+ a time zone offset of zero MUST be represented by "Z" and not
+ "+00:00".
+
+4.3. Comparator Interactions with Date-part Arguments
+
+ Not all comparators are suitable with all date-part arguments. In
+ general, the date-parts can be compared and tested for equality with
+ either "i;ascii-casemap" (the default) or "i;octet", but there are
+ two exceptions:
+
+ julian This is an integer, and may or may not have leading zeros.
+ As such, "i;ascii-numeric" is almost certainly the best
+ comparator to use with it.
+
+ std11 This is provided as a means to obtain date/time values in a
+ format appropriate for inclusion in email header fields. The
+ wide range of possible syntaxes for a std11 date/time --
+ which implementations of this extension are free to use when
+ composing a std11 string -- makes this format a poor choice
+ for comparisons. Nevertheless, if a comparison must be
+ performed, this is case-insensitive, and therefore "i;ascii-
+ casemap" needs to be used.
+
+ "year", "month", "day", "hour", "minute", "second" and "weekday" all
+ use fixed-width string representations of integers, and can therefore
+ be compared with "i;octet", "i;ascii-casemap", and "i;ascii-numeric"
+ with equivalent results.
+
+ "date" and "time" also use fixed-width string representations of
+ integers, and can therefore be compared with "i;octet" and "i;ascii-
+ casemap"; however, "i;ascii-numeric" can't be used with it, as
+ "i;ascii-numeric" doesn't allow for non-digit characters.
+
+
+
+
+
+Freed Standards Track [Page 5]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+4.4. Examples
+
+ The Date: field can be checked to test when the sender claims to have
+ created the message and act accordingly:
+
+ require ["date", "relational", "fileinto"];
+ if allof(header :is "from" "boss@example.com",
+ date :value "ge" :originalzone "date" "hour" "09",
+ date :value "lt" :originalzone "date" "hour" "17")
+ { fileinto "urgent"; }
+
+ Testing the initial Received: field can provide an indication of when
+ a message was actually received by the local system:
+
+ require ["date", "relational", "fileinto"];
+ if anyof(date :is "received" "weekday" "0",
+ date :is "received" "weekday" "6")
+ { fileinto "weekend"; }
+
+5. Currentdate Test
+
+ Usage: currentdate [":zone" <time-zone: string>]
+ [COMPARATOR] [MATCH-TYPE]
+ <date-part: string>
+ <key-list: string-list>
+
+ The currentdate test is similar to the date test, except that it
+ operates on the current date/time rather than a value extracted from
+ the message header. In particular, the ":zone" and date-part
+ arguments are the same as those in the date test.
+
+ All currentdate tests in a single Sieve script MUST refer to the same
+ point in time during execution of the script.
+
+ The :count value of a currentdate test is always 1.
+
+5.1. Examples
+
+ The simplest use of currentdate is to have an action that only
+ operates at certain times. For example, a user might want to have
+ messages redirected to their pager after business hours and on
+ weekends:
+
+
+
+
+
+
+
+
+
+Freed Standards Track [Page 6]
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+RFC 5260 Sieve Date and Index Extensions July 2008
+
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+ require ["date", "relational"];
+ if anyof(currentdate :is "weekday" "0",
+ currentdate :is "weekday" "6",
+ currentdate :value "lt" "hour" "09",
+ currentdate :value "ge" "hour" "17")
+ { redirect "pager@example.com"; }
+
+ Currentdate can be used to set up vacation [RFC5230] responses in
+ advance and to stop response generation automatically:
+
+ require ["date", "relational", "vacation"];
+ if allof(currentdate :value "ge" "date" "2007-06-30",
+ currentdate :value "le" "date" "2007-07-07")
+ { vacation :days 7 "I'm away during the first week in July."; }
+
+ Currentdate may also be used in conjunction with the variables
+ extension to pass time-dependent arguments to other tests and
+ actions. The following Sieve places messages in a folder named
+ according to the current month and year:
+
+ require ["date", "variables", "fileinto"];
+ if currentdate :matches "month" "*" { set "month" "${1}"; }
+ if currentdate :matches "year" "*" { set "year" "${1}"; }
+ fileinto "${month}-${year}";
+
+ Finally, currentdate can be used in conjunction with the editheader
+ extension to insert a header-field containing date/time information:
+
+ require ["variables", "date", "editheader"];
+ if currentdate :matches "std11" "*"
+ {addheader "Processing-date" "${0}";}
+
+6. Index Extension
+
+ The "index" extension, if specified, adds optional :index and :last
+ arguments to the header, address, and date tests as follows:
+
+ Syntax: date [":index" <fieldno: number> [":last"]]
+ [<":zone" <time-zone: string>> / ":originalzone"]
+ [COMPARATOR] [MATCH-TYPE] <header-name: string>
+ <date-part: string> <key-list: string-list>
+
+
+ Syntax: header [":index" <fieldno: number> [":last"]]
+ [COMPARATOR] [MATCH-TYPE]
+ <header-names: string-list> <key-list: string-list>
+
+
+
+
+
+Freed Standards Track [Page 7]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+ Syntax: address [":index" <fieldno: number> [":last"]]
+ [ADDRESS-PART] [COMPARATOR] [MATCH-TYPE]
+ <header-list: string-list> <key-list: string-list>
+
+ If :index <fieldno> is specified, the attempts to match a value are
+ limited to the header field fieldno (beginning at 1, the first named
+ header field). If :last is also specified, the count is backwards; 1
+ denotes the last named header field, 2 the second to last, and so on.
+ Specifying :last without :index is an error.
+
+ :index only counts separate header fields, not multiple occurrences
+ within a single field. In particular, :index cannot be used to test
+ a specific address in an address list contained within a single
+ header field.
+
+ Both header and address allow the specification of more than one
+ header field name. If more than one header field name is specified,
+ all the named header fields are counted in the order specified by the
+ header-list.
+
+6.1. Example
+
+ Mail delivery may involve multiple hops, resulting in the Received:
+ field containing information about when a message first entered the
+ local administrative domain being the second or subsequent field in
+ the message. As long as the field offset is consistent, it can be
+ tested:
+
+ # Implement the Internet-Draft cutoff date check assuming the
+ # second Received: field specifies when the message first
+ # entered the local email infrastructure.
+ require ["date", "relational", "index"];
+ if date :value "gt" :index 2 :zone "-0500" "received"
+ "iso8601" "2007-02-26T09:00:00-05:00",
+ { redirect "aftercutoff@example.org"; }
+
+7. Security Considerations
+
+ The facilities defined here, like the facilities in the base Sieve
+ specification, operate on message header information that can easily
+ be forged. Note, however, that some fields are inherently more
+ reliable than others. For example, the Date: field is typically
+ inserted by the message sender and can be altered at any point. By
+ contrast, the uppermost Received: field is typically inserted by the
+ local mail system and is therefore difficult for the sender or an
+ intermediary to falsify.
+
+
+
+
+
+Freed Standards Track [Page 8]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+ Use of the currentdate test makes script behavior inherently less
+ predictable and harder to analyze. This may have consequences for
+ systems that use script analysis to try and spot problematic scripts.
+
+ All of the security considerations given in the base Sieve
+ specification also apply to these extensions.
+
+8. IANA Considerations
+
+ The following templates specify the IANA registrations of the two
+ Sieve extensions specified in this document:
+
+ To: iana@iana.org
+ Subject: Registration of new Sieve extensions
+
+ Capability name: date
+ Description: The "date" extension gives Sieve the ability
+ to test date and time values.
+ RFC number: RFC 5260
+ Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
+
+ Capability name: index
+ Description: The "index" extension provides a means to
+ limit header and address tests to specific
+ instances when more than one field of a
+ given type is present.
+ RFC number: RFC 5260
+ Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
+
+9. References
+
+9.1. Normative References
+
+ [CALGO199] Tantzen, R., "Algorithm 199: Conversions Between Calendar
+ Date and Julian Day Number", Collected Algorithms from
+ CACM 199.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
+ April 2001.
+
+ [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
+ Internet: Timestamps", RFC 3339, July 2002.
+
+ [RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
+ Language", RFC 5228, January 2008.
+
+
+
+Freed Standards Track [Page 9]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+ [RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering:
+ Relational Extension", RFC 5231, January 2008.
+
+ [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", STD 68, RFC 5234, January 2008.
+
+9.2. Informative References
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [RFC5230] Showalter, T. and N. Freed, "Sieve Email Filtering:
+ Vacation Extension", RFC 5230, January 2008.
+
+
+
+
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+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+Appendix A. Julian Date Conversions
+
+ The following C routines show how to translate day/month/year
+ information to and from modified Julian dates. These routines are
+ straightforward translations of the Algol routines specified in CACM
+ Algorithm 199 [CALGO199].
+
+ Given the day, month, and year, jday returns the modified Julian
+ date.
+
+ int jday(int year, int month, int day)
+ {
+ int j, c, ya;
+
+ if (month > 2)
+ month -= 3;
+ else
+ {
+ month += 9;
+ year--;
+ }
+ c = year / 100;
+ ya = year - c * 100;
+ return (c * 146097 / 4 + ya * 1461 / 4 + (month * 153 + 2) / 5 +
+ day + 1721119);
+ }
+
+
+
+
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+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+ Given j, the modified Julian date, jdate returns the day, month, and
+ year.
+
+ void jdate(int j, int *year, int *month, int *day)
+ {
+ int y, m, d;
+
+ j -= 1721119;
+ y = (j * 4 - 1) / 146097;
+ j = j * 4 - y * 146097 - 1;
+ d = j / 4;
+ j = (d * 4 + 3) / 1461;
+ d = d * 4 - j * 1461 + 3;
+ d = (d + 4) / 4;
+ m = (d * 5 - 3) / 153;
+ d = d * 5 - m * 153 - 3;
+ *day = (d + 5) / 5;
+ *year = y * 100 + j;
+ if (m < 10)
+ *month = m + 3;
+ else
+ {
+ *month = m - 9;
+ *year += 1;
+ }
+ }
+
+Appendix B. Acknowledgements
+
+ Dave Cridland contributed the text describing the proper comparators
+ to use with different date-parts. Cyrus Daboo, Frank Ellerman,
+ Alexey Melnikov, Chris Newman, Dilyan Palauzov, and Aaron Stone
+ provided helpful suggestions and corrections.
+
+Author's Address
+
+ Ned Freed
+ Sun Microsystems
+ 800 Royal Oaks
+ Monrovia, CA 91016-6347
+ USA
+
+ Phone: +1 909 457 4293
+ EMail: ned.freed@mrochek.com
+
+
+
+
+
+
+
+Freed Standards Track [Page 12]
+
+RFC 5260 Sieve Date and Index Extensions July 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
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+Network Working Group P. Saint-Andre
+Request for Comments: 5437 Cisco
+Category: Standards Track A. Melnikov
+ Isode Limited
+ January 2009
+
+
+ Sieve Notification Mechanism:
+ Extensible Messaging and Presence Protocol (XMPP)
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (c) 2009 IETF Trust and the persons identified as the
+ document authors. All rights reserved.
+
+ This document is subject to BCP 78 and the IETF Trust's Legal
+ Provisions Relating to IETF Documents (http://trustee.ietf.org/
+ license-info) in effect on the date of publication of this document.
+ Please review these documents carefully, as they describe your rights
+ and restrictions with respect to this document.
+
+Abstract
+
+ This document describes a profile of the Sieve extension for
+ notifications, to allow notifications to be sent over the Extensible
+ Messaging and Presence Protocol (XMPP), also known as Jabber.
+
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+Saint-Andre & Melnikov Standards Track [Page 1]
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+RFC 5437 Sieve Notify Method: XMPP January 2009
+
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+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Overview ...................................................3
+ 1.2. Terminology ................................................3
+ 2. Definition ......................................................3
+ 2.1. Notify Parameter "method" ..................................3
+ 2.2. Test notify_method_capability ..............................3
+ 2.3. Notify Tag ":from" .........................................4
+ 2.4. Notify Tag ":importance" ...................................4
+ 2.5. Notify Tag ":message" ......................................4
+ 2.6. Notify Tag ":options" ......................................4
+ 2.7. XMPP Syntax ................................................4
+ 3. Examples ........................................................6
+ 3.1. Basic Action ...............................................6
+ 3.2. Action with "body" .........................................7
+ 3.3. Action with "body", ":importance", ":message", and
+ "subject" ..................................................7
+ 3.4. Action with ":from", ":message", ":importance",
+ "body", and "subject" ......................................8
+ 4. Requirements Conformance ........................................9
+ 5. Internationalization Considerations ............................10
+ 6. Security Considerations ........................................11
+ 7. IANA Considerations ............................................12
+ 8. References .....................................................12
+ 8.1. Normative References ......................................12
+ 8.2. Informative References ....................................13
+
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+Saint-Andre & Melnikov Standards Track [Page 2]
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+RFC 5437 Sieve Notify Method: XMPP January 2009
+
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+1. Introduction
+
+1.1. Overview
+
+ The [NOTIFY] extension to the [SIEVE] mail filtering language is a
+ framework for providing notifications by employing URIs to specify
+ the notification mechanism. This document defines how xmpp URIs (see
+ [XMPP-URI]) are used to generate notifications via the Extensible
+ Messaging and Presence Protocol [XMPP], which is widely implemented
+ in Jabber instant messaging technologies.
+
+1.2. Terminology
+
+ This document inherits terminology from [NOTIFY], [SIEVE], and
+ [XMPP]. In particular, the terms "parameter" and "tag" are used as
+ described in [NOTIFY] to refer to aspects of Sieve scripts, and the
+ term "key" is used as described in [XMPP-URI] to refer to aspects of
+ an XMPP URI.
+
+ The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
+ "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
+ RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
+ interpreted as described in [TERMS].
+
+2. Definition
+
+2.1. Notify Parameter "method"
+
+ The "method" parameter MUST be a URI that conforms to the xmpp URI
+ scheme (as specified in [XMPP-URI]) and that identifies an XMPP
+ account associated with the email inbox. The URI MAY include the
+ resource identifier of an XMPP address and/or the query component
+ portion of an XMPP URI, but SHOULD NOT include an authority component
+ or fragment identifier component. The processing application MUST
+ extract an XMPP address from the URI in accordance with the
+ processing rules specified in [XMPP-URI]. The resulting XMPP address
+ MUST be encapsulated in XMPP syntax as the value of the XMPP 'to'
+ attribute.
+
+2.2. Test notify_method_capability
+
+ In response to a notify_method_capability test for the "online"
+ notification-capability, an implementation SHOULD return a value of
+ "yes" if it has knowledge of an active presence session (see
+ [XMPP-IM]) for the specified XMPP notification-uri; otherwise, it
+ SHOULD return a value of "maybe" (since typical XMPP systems may not
+ allow a Sieve engine to gain knowledge about the presence of XMPP
+ entities).
+
+
+
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+RFC 5437 Sieve Notify Method: XMPP January 2009
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+2.3. Notify Tag ":from"
+
+ If included, the ":from" tag MUST be an electronic address that
+ conforms to the "Mailbox" rule defined in [RFC5321]. The value of
+ the ":from" tag MAY be included in the human-readable XML character
+ data of the XMPP notification; alternatively or in addition, it MAY
+ be transformed into formal XMPP syntax, in which case it MUST be
+ encapsulated as the value of an XMPP SHIM (Stanza Headers and
+ Internet Metadata) [SHIM] header named "Resent-From".
+
+2.4. Notify Tag ":importance"
+
+ The ":importance" tag has no special meaning for this notification
+ mechanism, and this specification puts no restriction on its use.
+ The value of the ":importance" tag MAY be transformed into XMPP
+ syntax (in addition to or instead of including appropriate text in
+ the XML character data of the XMPP <body/> element); if so, it SHOULD
+ be encapsulated as the value of an XMPP SHIM (Stanza Headers and
+ Internet Metadata) [SHIM] header named "Urgency", where the XML
+ character of that header is "high" if the value of the ":importance"
+ tag is "1", "medium" if the value of the ":importance" tag is "2",
+ and "low" if the value of the ":importance" tag is "3".
+
+2.5. Notify Tag ":message"
+
+ If the ":message" tag is included, that string MUST be transformed
+ into the XML character data of an XMPP <body/> element (where the
+ string is generated according to the guidelines specified in Section
+ 3.6 of [NOTIFY]).
+
+2.6. Notify Tag ":options"
+
+ The ":options" tag has no special meaning for this notification
+ mechanism. Any handling of this tag is the responsibility of an
+ implementation.
+
+2.7. XMPP Syntax
+
+ The xmpp mechanism results in the sending of an XMPP message to
+ notify a recipient about an email message. The general XMPP syntax
+ is as follows:
+
+ o The notification MUST be an XMPP <message/> stanza.
+
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+ o The value of the XMPP 'from' attribute SHOULD be the XMPP address
+ of the notification service associated with the Sieve engine or
+ the XMPP address of the entity to be notified. The value of the
+ XMPP 'from' attribute MUST NOT be generated from the Sieve ":from"
+ tag.
+
+ o The value of the XMPP 'to' attribute MUST be the XMPP address
+ specified in the XMPP URI contained in the "method" notify
+ parameter.
+
+ o The value of the XMPP 'type' attribute MUST be 'headline' or
+ 'normal'.
+
+ o The XMPP <message/> stanza MUST include a <body/> child element.
+ If the ":message" tag is included in the Sieve script, that string
+ MUST be used as the XML character data of the <body/> element. If
+ not and if the XMPP URI contained in the "method" notify parameter
+ specified a "body" key in the query component, that value SHOULD
+ be used. Otherwise, the XML character data SHOULD be some
+ configurable text indicating that the message is a Sieve
+ notification.
+
+ o The XMPP <message/> stanza MAY include a <subject/> child element.
+ If the XMPP URI contained in the "method" notify parameter
+ specified a "subject" key in the query component, that value
+ SHOULD be used as the XML character data of the <subject/>
+ element. Otherwise, the XML character data SHOULD be some
+ configurable text indicating that the message is a Sieve
+ notification.
+
+ o The XMPP <message/> stanza SHOULD include a URI, for the recipient
+ to use as a hint in locating the message, encapsulated as the XML
+ character data of a <url/> child element of an <x/> element
+ qualified by the 'jabber:x:oob' namespace, as specified in [OOB].
+ If included, the URI SHOULD be an Internet Message Access Protocol
+ [IMAP] URL that specifies the location of the message, as defined
+ in [IMAP-URL], but MAY be another URI type that can specify or
+ hint at the location of an email message, such as a URI for an
+ HTTP resource [HTTP] or a Post Office Protocol Version 3 (POP3)
+ mailbox [POP-URL] at which the message can be accessed. It is not
+ expected that an XMPP user agent shall directly handle such a URI,
+ but instead that it shall invoke an appropriate helper application
+ to handle the URI.
+
+ o The XMPP <message/> stanza MAY include an XMPP SHIM (Stanza
+ Headers and Internet Metadata) [SHIM] header named "Resent-From".
+ If the Sieve script included a ":from" tag, the "Resent-From"
+
+
+
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+RFC 5437 Sieve Notify Method: XMPP January 2009
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+ value MUST be the value of the ":from" tag; otherwise, the
+ "Resent-From" value SHOULD be the envelope recipient address of
+ the original email message that triggered the notification.
+
+3. Examples
+
+ In the following examples, the sender of the email has an address of
+ <mailto:juliet@example.org>, the entity to be notified has an email
+ address of <mailto:romeo@example.com> and an XMPP address of
+ romeo@im.example.com (resulting in an XMPP URI of
+ <xmpp:romeo@im.example.com>), and the notification service associated
+ with the Sieve engine has an XMPP address of notify.example.com.
+
+ Note: In the following examples, line breaks are included in XMPP
+ URIs solely for the purpose of readability.
+
+3.1. Basic Action
+
+ The following is a basic Sieve notify action with only a method. The
+ XML character data of the XMPP <body/> and <subject/> elements are
+ therefore generated by the Sieve engine based on configuration. In
+ addition, the Sieve engine includes a URI pointing to the message.
+
+ Basic action (Sieve syntax)
+
+ notify "xmpp:romeo@im.example.com"
+
+ The resulting XMPP <message/> stanza might be as follows:
+
+ Basic action (XMPP syntax)
+
+ <message from='notify.example.com'
+ to='romeo@im.example.com'
+ type='headline'
+ xml:lang='en'>
+ <subject>SIEVE</subject>
+ <body><juliet@example.com> You got mail.</body>
+ <x xmlns='jabber:x:oob'>
+ <url>
+ imap://romeo@example.com/INBOX;UIDVALIDITY=385759043/;UID=18
+ </url>
+ </x>
+ </message>
+
+
+
+
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+3.2. Action with "body"
+
+ The following action contains a "body" key in the query component of
+ the XMPP URI but no ":message" tag in the Sieve script. As a result,
+ the XML character data of the XMPP <body/> element in the XMPP
+ notification is taken from the XMPP URI. In addition, the Sieve
+ engine includes a URI pointing to the message.
+
+ Action with "body" (Sieve syntax)
+
+ notify "xmpp:romeo@im.example.com?message
+ ;body=Wherefore%20art%20thou%3F"
+
+ The resulting XMPP <message/> stanza might be as follows.
+
+ Action with "body" (XMPP syntax)
+
+ <message from='notify.example.com'
+ to='romeo@im.example.com'
+ type='headline'
+ xml:lang='en'>
+ <subject>SIEVE</subject>
+ <body>Wherefore art thou?</body>
+ <x xmlns='jabber:x:oob'>
+ <url>
+ imap://romeo@example.com/INBOX;UIDVALIDITY=385759044/;UID=19
+ </url>
+ </x>
+ </message>
+
+3.3. Action with "body", ":importance", ":message", and "subject"
+
+ The following action specifies an ":importance" tag and a ":message"
+ tag in the Sieve script, as well as a "body" key and a "subject" key
+ in the query component of the XMPP URI. As a result, the ":message"
+ tag from the Sieve script overrides the "body" key from the XMPP URI
+ when generating the XML character data of the XMPP <body/> element.
+ In addition, the Sieve engine includes a URI pointing to the message.
+
+ Action with "body", ":importance", ":message", and "subject" (Sieve
+ syntax)
+
+ notify :importance "1"
+ :message "Contact Juliet immediately!"
+ "xmpp:romeo@im.example.com?message
+ ;body=You%27re%20in%20trouble
+ ;subject=ALERT%21"
+
+
+
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+ The resulting XMPP <message/> stanza might be as follows.
+
+ Action with "body", ":importance", ":message", and "subject" (XMPP
+ syntax)
+
+ <message from='notify.example.com'
+ to='romeo@im.example.com'
+ type='headline'
+ xml:lang='en'>
+ <subject>ALERT!</subject>
+ <body>Contact Juliet immediately!</body>
+ <headers xmlns='http://jabber.org/protocol/shim'>
+ <header name='Urgency'>high</header>
+ </headers>
+ <x xmlns='jabber:x:oob'>
+ <url>
+ imap://romeo@example.com/INBOX;UIDVALIDITY=385759045/;UID=20
+ </url>
+ </x>
+ </message>
+
+3.4. Action with ":from", ":message", ":importance", "body", and
+ "subject"
+
+ The following action specifies a ":from" tag, an ":importance" tag,
+ and a ":message" tag in the Sieve script, as well as a "body" key and
+ a "subject" key in the query component of the XMPP URI. As a result,
+ the ":message" tag from the Sieve script overrides the "body" key
+ from the XMPP URI when generating the XML character data of the XMPP
+ <body/> element. In addition, the Sieve engine includes a URI
+ pointing to the message, as well as an XMPP SHIM (Stanza Headers and
+ Internet Metadata) [SHIM] header named "Resent-From" (which
+ encapsulates the value of the ":from" tag).
+
+ Action with ":from", ":importance", ":message", "body", and "subject"
+ (Sieve syntax)
+
+ notify :from "romeo.my.romeo@example.com"
+ :importance "1"
+ :message "Contact Juliet immediately!"
+ "xmpp:romeo@im.example.com?message
+ ;body=You%27re%20in%20trouble
+ ;subject=ALERT%21"
+
+ The resulting XMPP <message/> stanza might be as follows.
+
+
+
+
+
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+ Action with ":from", ":importance", ":message", "body", and "subject"
+ (XMPP syntax)
+
+ <message from='notify.example.com'
+ to='romeo@im.example.com'
+ type='headline'
+ xml:lang='en'>
+ <subject>ALERT!</subject>
+ <body>Contact Juliet immediately!</body>
+ <headers xmlns='http://jabber.org/protocol/shim'>
+ <header name='Resent-From'>romeo.my.romeo@example.com</header>
+ <header name='Urgency'>high</header>
+ </headers>
+ <x xmlns='jabber:x:oob'>
+ <url>
+ imap://romeo@example.com/INBOX;UIDVALIDITY=385759045/;UID=21
+ </url>
+ </x>
+ </message>
+
+4. Requirements Conformance
+
+ Section 3.8 of [NOTIFY] specifies a set of requirements for Sieve
+ notification methods. The conformance of the xmpp notification
+ mechanism is provided here.
+
+ 1. An implementation of the xmpp notification method SHOULD NOT
+ modify the final notification text (e.g., to limit the length);
+ however, a given deployment MAY do so (e.g., if recipients pay
+ per character or byte for XMPP messages). Modification of
+ characters themselves should not be necessary, since XMPP
+ character data is encoded in [UTF-8].
+
+ 2. An implementation MAY ignore parameters specified in the
+ ":from", ":importance", and ":options" tags.
+
+ 3. There is no recommended default message for an implementation to
+ include if the ":message" tag is not specified.
+
+ 4. A notification sent via the xmpp notification method MAY include
+ a timestamp in the textual message.
+
+ 5. The value of the XMPP 'from' attribute MUST be the XMPP address
+ of the notification service associated with the Sieve engine.
+ The value of the Sieve ":from" tag MAY be transformed into the
+ value of an XMPP SHIM (Stanza Headers and Internet Metadata)
+ [SHIM] header named "Resent-From".
+
+
+
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+ 6. The value of the XMPP 'to' attribute MUST be the XMPP address
+ specified in the XMPP URI contained in the "method" parameter.
+
+ 7. In accordance with [XMPP-URI], an implementation MUST ignore any
+ URI action or key it does not understand (i.e., the URI MUST be
+ processed as if the action or key were not present). It is
+ RECOMMENDED to support the XMPP "message" query type (see
+ [QUERIES]) and the associated "body" and "subject" keys, which
+ SHOULD be mapped to the XMPP <body/> and <subject/> child
+ elements of the XMPP <message/> stanza, respectively. However,
+ if included, then the Sieve notify ":message" tag MUST be mapped
+ to the XMPP <body/> element, overriding the "body" key (if any)
+ included in the XMPP URI.
+
+ 8. An implementation MUST NOT include any other extraneous
+ information not specified in parameters to the notify action.
+
+ 9. In response to a notify_method_capability test for the "online"
+ notification-capability, an implementation SHOULD return a value
+ of "yes" if it has knowledge of an active presence session (see
+ [XMPP-IM]) for the specified XMPP notification-uri, but only if
+ the entity that requested the test is authorized to know the
+ presence of the associated XMPP entity (e.g., via explicit
+ presence subscription as specified in [XMPP-IM]); otherwise, it
+ SHOULD return a value of "maybe" (since typical XMPP systems may
+ not allow a Sieve engine to gain knowledge about the presence of
+ XMPP entities).
+
+ 10. An implementation SHOULD NOT attempt to retry delivery of a
+ notification if it receives an XMPP error of type "auth" or
+ "cancel", MAY attempt to retry delivery if it receives an XMPP
+ error of type "wait", and MAY attempt to retry delivery if it
+ receives an XMPP error of "modify", but only if it makes
+ appropriate modifications to the notification (see [XMPP]); in
+ any case, the number of retries SHOULD be limited to a
+ configurable number no less than 3 and no more than 10. An
+ implementation MAY throttle notifications if the number of
+ notifications within a given time period becomes excessive
+ according to local service policy. Duplicate suppression (if
+ any) is a matter of implementation and is not specified herein.
+
+5. Internationalization Considerations
+
+ Although an XMPP address may contain nearly any [UNICODE] character,
+ the value of the "method" parameter MUST be a Uniform Resource
+ Identifier (see [URI]) rather than an Internationalized Resource
+ Identifier (see [IRI]). The rules specified in [XMPP-URI] MUST be
+ followed when generating XMPP URIs.
+
+
+
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+ In accordance with Section 13 of RFC 3920, all data sent over XMPP
+ MUST be encoded in [UTF-8].
+
+6. Security Considerations
+
+ Depending on the information included, sending a notification can be
+ comparable to forwarding mail to the notification recipient. Care
+ must be taken when forwarding mail automatically, to ensure that
+ confidential information is not sent into an insecure environment.
+ In particular, implementations MUST conform to the security
+ considerations given in [NOTIFY], [SIEVE], and [XMPP].
+
+ [NOTIFY] specifies that a notification method MUST provide mechanisms
+ for avoiding notification loops. One type of notification loop can
+ be caused by message forwarding; however, such loops are prevented
+ because XMPP does not support the forwarding of messages from one
+ XMPP address to another. Another type of notification loop can be
+ caused by auto-replies to XMPP messages received by the XMPP
+ notification service associated with the Sieve engine; therefore,
+ such a service MUST NOT auto-reply to XMPP messages it receives.
+
+ A common use case might be for a user to create a script that enables
+ the Sieve engine to act differently if the user is currently
+ available at a particular type of service (e.g., send notifications
+ to the user's XMPP address if the user has an active session at an
+ XMPP service). Whether the user is currently available can be
+ determined by means of a notify_method_capability test for the
+ "online" notification-capability. In XMPP, information about current
+ network availability is called "presence" (see also [MODEL]). Since
+ [XMPP-IM] requires that a user must approve a presence subscription
+ before an entity can gain access to the user's presence information,
+ a limited but reasonably safe implementation might be for the Sieve
+ engine to request a subscription to the user's presence. The user
+ would then need to approve that subscription request so that the
+ Sieve engine can act appropriately depending on whether the user is
+ online or offline. However, the Sieve engine MUST NOT use the user's
+ presence information when processing scripts on behalf of a script
+ owner other than the user, unless the Sieve engine has explicit
+ knowledge (e.g., via integration with an XMPP server's presence
+ authorization rules) that the script owner is authorized to know the
+ user's presence. While it would be possible to design a more
+ advanced approach to the delegation of presence authorization, any
+ such approach is left to future standards work.
+
+
+
+
+
+
+
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+RFC 5437 Sieve Notify Method: XMPP January 2009
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+7. IANA Considerations
+
+ The following template provides the IANA registration of the Sieve
+ notification mechanism specified in this document:
+
+ To: iana@iana.org
+ Subject: Registration of new Sieve notification mechanism
+ Mechanism name: xmpp
+ Mechanism URI: RFC 5122 [XMPP-URI]
+ Mechanism-specific options: none
+ Permanent and readily available reference: RFC 5437
+ Person and email address to contact for further information:
+ Peter Saint-Andre <registrar@xmpp.org>
+
+ This information has been added to the list of Sieve notification
+ mechanisms maintained at <http://www.iana.org>.
+
+8. References
+
+8.1. Normative References
+
+ [NOTIFY] Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
+ Martin, "Sieve Email Filtering: Extension for
+ Notifications", RFC 5435, January 2009.
+
+ [OOB] Saint-Andre, P., "Out of Band Data", XSF XEP 0066,
+ August 2006.
+
+ [QUERIES] Saint-Andre, P., "XMPP URI Scheme Query Components", XSF
+ XEP 0147, September 2006.
+
+ [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
+ October 2008.
+
+ [SHIM] Saint-Andre, P. and J. Hildebrand, "Stanza Headers and
+ Internet Metadata", XSF XEP 0131, July 2006.
+
+ [SIEVE] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
+ Filtering Language", RFC 5228, January 2008.
+
+ [TERMS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [XMPP-URI] Saint-Andre, P., "Internationalized Resource Identifiers
+ (IRIs) and Uniform Resource Identifiers (URIs) for the
+ Extensible Messaging and Presence Protocol (XMPP)",
+ RFC 5122, February 2008.
+
+
+
+
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+8.2. Informative References
+
+ [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
+ Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
+ Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
+
+ [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [IMAP-URL] Melnikov, A. and C. Newman, "IMAP URL Scheme", RFC 5092,
+ November 2007.
+
+ [IRI] Duerst, M. and M. Suignard, "Internationalized Resource
+ Identifiers (IRIs)", RFC 3987, January 2005.
+
+ [MODEL] Day, M., Rosenberg, J., and H. Sugano, "A Model for
+ Presence and Instant Messaging", RFC 2778, February 2000.
+
+ [POP-URL] Gellens, R., "POP URL Scheme", RFC 2384, August 1998.
+
+ [UNICODE] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0", 2000.
+
+ The Unicode Standard, Version 3.2.0 is defined by The
+ Unicode Standard, Version 3.0 (Reading, MA, Addison-
+ Wesley, 2000. ISBN 0-201-61633-5), as amended by the
+ Unicode Standard Annex #27: Unicode 3.1
+ (http://www.unicode.org/reports/tr27/) and by the Unicode
+ Standard Annex #28: Unicode 3.2
+ (http://www.unicode.org/reports/tr28/).
+
+ [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+ Resource Identifier (URI): Generic Syntax", STD 66,
+ RFC 3986, January 2005.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [XMPP] Saint-Andre, P., "Extensible Messaging and Presence
+ Protocol (XMPP): Core", RFC 3920, October 2004.
+
+ [XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence
+ Protocol (XMPP): Instant Messaging and Presence",
+ RFC 3921, October 2004.
+
+
+
+
+
+
+
+Saint-Andre & Melnikov Standards Track [Page 13]
+
+RFC 5437 Sieve Notify Method: XMPP January 2009
+
+
+Authors' Addresses
+
+ Peter Saint-Andre
+ Cisco
+
+ EMail: psaintan@cisco.com
+
+
+ Alexey Melnikov
+ Isode Limited
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+Saint-Andre & Melnikov Standards Track [Page 14]
+
diff --git a/rfc/sieve/rfc5804.txt b/rfc/sieve/rfc5804.txt
@@ -0,0 +1,2747 @@
+
+
+
+
+
+
+Internet Engineering Task Force (IETF) A. Melnikov, Ed.
+Request for Comments: 5804 Isode Limited
+Category: Standards Track T. Martin
+ISSN: 2070-1721 BeThereBeSquare, Inc.
+ July 2010
+
+
+ A Protocol for Remotely Managing Sieve Scripts
+
+Abstract
+
+ Sieve scripts allow users to filter incoming email. Message stores
+ are commonly sealed servers so users cannot log into them, yet users
+ must be able to update their scripts on them. This document
+ describes a protocol "ManageSieve" for securely managing Sieve
+ scripts on a remote server. This protocol allows a user to have
+ multiple scripts, and also alerts a user to syntactically flawed
+ scripts.
+
+Status of This Memo
+
+ This is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc5804.
+
+Copyright Notice
+
+ Copyright (c) 2010 IETF Trust and the persons identified as the
+ document authors. All rights reserved.
+
+ This document is subject to BCP 78 and the IETF Trust's Legal
+ Provisions Relating to IETF Documents
+ (http://trustee.ietf.org/license-info) in effect on the date of
+ publication of this document. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+
+
+
+Melnikov & Martin Standards Track [Page 1]
+
+RFC 5804 ManageSieve July 2010
+
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Commands and Responses .....................................3
+ 1.2. Syntax .....................................................3
+ 1.3. Response Codes .............................................3
+ 1.4. Active Script ..............................................6
+ 1.5. Quotas .....................................................6
+ 1.6. Script Names ...............................................6
+ 1.7. Capabilities ...............................................7
+ 1.8. Transport ..................................................9
+ 1.9. Conventions Used in This Document .........................10
+ 2. Commands .......................................................10
+ 2.1. AUTHENTICATE Command ......................................11
+ 2.1.1. Use of SASL PLAIN Mechanism over TLS ...............16
+ 2.2. STARTTLS Command ..........................................16
+ 2.2.1. Server Identity Check ..............................17
+ 2.3. LOGOUT Command ............................................20
+ 2.4. CAPABILITY Command ........................................20
+ 2.5. HAVESPACE Command .........................................20
+ 2.6. PUTSCRIPT Command .........................................21
+ 2.7. LISTSCRIPTS Command .......................................23
+ 2.8. SETACTIVE Command .........................................24
+ 2.9. GETSCRIPT Command .........................................25
+ 2.10. DELETESCRIPT Command .....................................25
+ 2.11. RENAMESCRIPT Command .....................................26
+ 2.12. CHECKSCRIPT Command ......................................27
+ 2.13. NOOP Command .............................................28
+ 2.14. Recommended Extensions ...................................28
+ 2.14.1. UNAUTHENTICATE Command ............................28
+ 3. Sieve URL Scheme ...............................................29
+ 4. Formal Syntax ..................................................31
+ 5. Security Considerations ........................................37
+ 6. IANA Considerations ............................................38
+ 6.1. ManageSieve Capability Registration Template ..............39
+ 6.2. Registration of Initial ManageSieve Capabilities ..........39
+ 6.3. ManageSieve Response Code Registration Template ...........41
+ 6.4. Registration of Initial ManageSieve Response Codes ........41
+ 7. Internationalization Considerations ............................46
+ 8. Acknowledgements ...............................................46
+ 9. References .....................................................47
+ 9.1. Normative References ......................................47
+ 9.2. Informative References ....................................48
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 2]
+
+RFC 5804 ManageSieve July 2010
+
+
+1. Introduction
+
+1.1. Commands and Responses
+
+ A ManageSieve connection consists of the establishment of a client/
+ server network connection, an initial greeting from the server, and
+ client/server interactions. These client/server interactions consist
+ of a client command, server data, and a server completion result
+ response.
+
+ All interactions transmitted by client and server are in the form of
+ lines, that is, strings that end with a CRLF. The protocol receiver
+ of a ManageSieve client or server is either reading a line or reading
+ a sequence of octets with a known count followed by a line.
+
+1.2. Syntax
+
+ ManageSieve is a line-oriented protocol much like [IMAP] or [ACAP],
+ which runs over TCP. There are three data types: atoms, numbers and
+ strings. Strings may be quoted or literal. See [ACAP] for detailed
+ descriptions of these types.
+
+ Each command consists of an atom (the command name) followed by zero
+ or more strings and numbers terminated by CRLF.
+
+ All client queries are replied to with either an OK, NO, or BYE
+ response. Each response may be followed by a response code (see
+ Section 1.3) and by a string consisting of human-readable text in the
+ local language (as returned by the LANGUAGE capability; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. The contents of the string
+ SHOULD be shown to the user ,and implementations MUST NOT attempt to
+ parse the message for meaning.
+
+ The BYE response SHOULD be used if the server wishes to close the
+ connection. A server may wish to do this because the client was idle
+ for too long or there were too many failed authentication attempts.
+ This response can be issued at any time and should be immediately
+ followed by a server hang-up of the connection. If a server has an
+ inactivity timeout resulting in client autologout, it MUST be no less
+ than 30 minutes after successful authentication. The inactivity
+ timeout MAY be less before authentication.
+
+1.3. Response Codes
+
+ An OK, NO, or BYE response from the server MAY contain a response
+ code to describe the event in a more detailed machine-parsable
+ fashion. A response code consists of data inside parentheses in the
+ form of an atom, possibly followed by a space and arguments.
+
+
+
+Melnikov & Martin Standards Track [Page 3]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response codes are defined when there is a specific action that a
+ client can take based upon the additional information. In order to
+ support future extension, the response code is represented as a
+ slash-separated (Solidus, %x2F) hierarchy with each level of
+ hierarchy representing increasing detail about the error. Response
+ codes MUST NOT start with the Solidus character. Clients MUST
+ tolerate additional hierarchical response code detail that they don't
+ understand. For example, if the client supports the "QUOTA" response
+ code, but doesn't understand the "QUOTA/MAXSCRIPTS" response code, it
+ should treat "QUOTA/MAXSCRIPTS" as "QUOTA".
+
+ Client implementations MUST tolerate (ignore) response codes that
+ they do not recognize.
+
+ The currently defined response codes are the following:
+
+ AUTH-TOO-WEAK
+
+ This response code is returned in the NO or BYE response from an
+ AUTHENTICATE command. It indicates that site security policy forbids
+ the use of the requested mechanism for the specified authentication
+ identity.
+
+ ENCRYPT-NEEDED
+
+ This response code is returned in the NO or BYE response from an
+ AUTHENTICATE command. It indicates that site security policy
+ requires the use of a strong encryption mechanism for the specified
+ authentication identity and mechanism.
+
+ QUOTA
+
+ If this response code is returned in the NO/BYE response, it means
+ that the command would have placed the user above the site-defined
+ quota constraints. If this response code is returned in the OK
+ response, it can mean that the user's storage is near its quota, or
+ it can mean that the account exceeded its quota but that the
+ condition is being allowed by the server (the server supports
+ so-called soft quotas). The QUOTA response code has two more
+ detailed variants: "QUOTA/MAXSCRIPTS" (the maximum number of per-user
+ scripts) and "QUOTA/MAXSIZE" (the maximum script size).
+
+ REFERRAL
+
+ This response code may be returned with a BYE result from any
+ command, and includes a mandatory parameter that indicates what
+ server to access to manage this user's Sieve scripts. The server
+ will be specified by a Sieve URL (see Section 3). The scriptname
+
+
+
+Melnikov & Martin Standards Track [Page 4]
+
+RFC 5804 ManageSieve July 2010
+
+
+ portion of the URL MUST NOT be specified. The client should
+ authenticate to the specified server and use it for all further
+ commands in the current session.
+
+ SASL
+
+ This response code can occur in the OK response to a successful
+ AUTHENTICATE command and includes the optional final server response
+ data from the server as specified by [SASL].
+
+ TRANSITION-NEEDED
+
+ This response code occurs in a NO response of an AUTHENTICATE
+ command. It indicates that the user name is valid, but the entry in
+ the authentication database needs to be updated in order to permit
+ authentication with the specified mechanism. This is typically done
+ by establishing a secure channel using TLS, verifying server identity
+ as specified in Section 2.2.1, and finally authenticating once using
+ the [PLAIN] authentication mechanism. The selected mechanism SHOULD
+ then work for authentications in subsequent sessions.
+
+ This condition can happen if a user has an entry in a system
+ authentication database such as Unix /etc/passwd, but does not have
+ credentials suitable for use by the specified mechanism.
+
+ TRYLATER
+
+ A command failed due to a temporary server failure. The client MAY
+ continue using local information and try the command later. This
+ response code only makes sense when returned in a NO/BYE response.
+
+ ACTIVE
+
+ A command failed because it is not allowed on the active script, for
+ example, DELETESCRIPT on the active script. This response code only
+ makes sense when returned in a NO/BYE response.
+
+ NONEXISTENT
+
+ A command failed because the referenced script name doesn't exist.
+ This response code only makes sense when returned in a NO/BYE
+ response.
+
+ ALREADYEXISTS
+
+ A command failed because the referenced script name already exists.
+ This response code only makes sense when returned in a NO/BYE
+ response.
+
+
+
+Melnikov & Martin Standards Track [Page 5]
+
+RFC 5804 ManageSieve July 2010
+
+
+ TAG
+
+ This response code name is followed by a string specified in the
+ command. See Section 2.13 for a possible use case.
+
+ WARNINGS
+
+ This response code MAY be returned by the server in the OK response
+ (but it might be returned with the NO/BYE response as well) and
+ signals the client that even though the script is syntactically
+ valid, it might contain errors not intended by the script writer.
+ This response code is typically returned in response to PUTSCRIPT
+ and/or CHECKSCRIPT commands. A client seeing such response code
+ SHOULD present the returned warning text to the user.
+
+1.4. Active Script
+
+ A user may have multiple Sieve scripts on the server, yet only one
+ script may be used for filtering of incoming messages. This is the
+ active script. Users may have zero or one active script and MUST use
+ the SETACTIVE command described below for changing the active script
+ or disabling Sieve processing. For example, users may have an
+ everyday script they normally use and a special script they use when
+ they go on vacation. Users can change which script is being used
+ without having to download and upload a script stored somewhere else.
+
+1.5. Quotas
+
+ Servers SHOULD impose quotas to prevent malicious users from
+ overflowing available storage. If a command would place a user over
+ a quota setting, servers that impose such quotas MUST reply with a NO
+ response containing the QUOTA response code. Client implementations
+ MUST be able to handle commands failing because of quota
+ restrictions.
+
+1.6. Script Names
+
+ A Sieve script name is a sequence of Unicode characters encoded in
+ UTF-8 [UTF-8]. A script name MUST comply with Net-Unicode Definition
+ (Section 2 of [NET-UNICODE]), with the additional restriction of
+ prohibiting the following Unicode characters:
+
+ o 0000-001F; [CONTROL CHARACTERS]
+
+ o 007F; DELETE
+
+ o 0080-009F; [CONTROL CHARACTERS]
+
+
+
+
+Melnikov & Martin Standards Track [Page 6]
+
+RFC 5804 ManageSieve July 2010
+
+
+ o 2028; LINE SEPARATOR
+
+ o 2029; PARAGRAPH SEPARATOR
+
+ Sieve script names MUST be at least one octet (and hence Unicode
+ character) long. Zero octets script name has a special meaning (see
+ Section 2.8). Servers MUST allow names of up to 128 Unicode
+ characters in length (which can take up to 512 bytes when encoded in
+ UTF-8, not counting the terminating NUL), and MAY allow longer names.
+ A server that receives a script name longer than its internal limit
+ MUST reject the corresponding operation, in particular it MUST NOT
+ truncate the script name.
+
+1.7. Capabilities
+
+ Server capabilities are sent automatically by the server upon a
+ client connection, or after successful STARTTLS and AUTHENTICATE
+ (which establishes a Simple Authentication and Security Layer (SASL))
+ commands. Capabilities may change immediately after a successfully
+ completed STARTTLS command, and/or immediately after a successfully
+ completed AUTHENTICATE command, and/or after a successfully completed
+ UNAUTHENTICATE command (see Section 2.14.1). Capabilities MUST
+ remain static at all other times.
+
+ Clients MAY request the capabilities at a later time by issuing the
+ CAPABILITY command described later. The capabilities consist of a
+ series of lines each with one or two strings. The first string is
+ the name of the capability, which is case-insensitive. The second
+ optional string is the value associated with that capability. Order
+ of capabilities is arbitrary, but each capability name can appear at
+ most once.
+
+ The following capabilities are defined in this document:
+
+ IMPLEMENTATION - Name of implementation and version. This capability
+ MUST always be returned by the server.
+
+ SASL - List of SASL mechanisms supported by the server, each
+ separated by a space. This list can be empty if and only if STARTTLS
+ is also advertised. This means that the client must negotiate TLS
+ encryption with STARTTLS first, at which point the SASL capability
+ will list a non-empty list of SASL mechanisms.
+
+ SIEVE - List of space-separated Sieve extensions (as listed in Sieve
+ "require" action [SIEVE]) supported by the Sieve engine. This
+ capability MUST always be returned by the server.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 7]
+
+RFC 5804 ManageSieve July 2010
+
+
+ STARTTLS - If TLS [TLS] is supported by this implementation. Before
+ advertising this capability a server MUST verify to the best of its
+ ability that TLS can be successfully negotiated by a client with
+ common cipher suites. Specifically, a server should verify that a
+ server certificate has been installed and that the TLS subsystem has
+ successfully initialized. This capability SHOULD NOT be advertised
+ once STARTTLS or AUTHENTICATE command completes successfully. Client
+ and server implementations MUST implement the STARTTLS extension.
+
+ MAXREDIRECTS - Specifies the limit on the number of Sieve "redirect"
+ actions a script can perform during a single evaluation. Note that
+ this is different from the total number of "redirect" actions a
+ script can contain. The value is a non-negative number represented
+ as a ManageSieve string.
+
+ NOTIFY - A space-separated list of URI schema parts for supported
+ notification methods. This capability MUST be specified if the Sieve
+ implementation supports the "enotify" extension [NOTIFY].
+
+ LANGUAGE - The language (<Language-Tag> from [RFC5646]) currently
+ used for human-readable error messages. If this capability is not
+ returned, the "i-default" [RFC2277] language is assumed. Note that
+ the current language MAY be per-user configurable (i.e., it MAY
+ change after authentication).
+
+ OWNER - The canonical name of the logged-in user (SASL "authorization
+ identity") encoded in UTF-8. This capability MUST NOT be returned in
+ unauthenticated state and SHOULD be returned once the AUTHENTICATE
+ command succeeds.
+
+ VERSION - This capability MUST be returned by servers compliant with
+ this document or its successor. For servers compliant with this
+ document, the capability value is the string "1.0". Lack of this
+ capability means that the server predates this specification and thus
+ doesn't support the following commands: RENAMESCRIPT, CHECKSCRIPT,
+ and NOOP.
+
+ Section 2.14 defines some additional ManageSieve extensions and their
+ respective capabilities.
+
+ A server implementation MUST return SIEVE, IMPLEMENTATION, and
+ VERSION capabilities.
+
+ A client implementation MUST ignore any listed capabilities that it
+ does not understand.
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 8]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Example:
+
+ S: "IMPlemENTATION" "Example1 ManageSieved v001"
+ S: "SASl" "DIGEST-MD5 GSSAPI"
+ S: "SIeVE" "fileinto vacation"
+ S: "StaRTTLS"
+ S: "NOTIFY" "xmpp mailto"
+ S: "MAXREdIRECTS" "5"
+ S: "VERSION" "1.0"
+ S: OK
+
+ After successful authentication, this might look like this:
+
+ Example:
+
+ S: "IMPlemENTATION" "Example1 ManageSieved v001"
+ S: "SASl" "DIGEST-MD5 GSSAPI"
+ S: "SIeVE" "fileinto vacation"
+ S: "NOTIFY" "xmpp mailto"
+ S: "OWNER" "alexey@example.com"
+ S: "MAXREdIRECTS" "5"
+ S: "VERSION" "1.0"
+ S: OK
+
+1.8. Transport
+
+ The ManageSieve protocol assumes a reliable data stream such as that
+ provided by TCP. When TCP is used, a ManageSieve server typically
+ listens on port 4190.
+
+ Before opening the TCP connection, the ManageSieve client first MUST
+ resolve the Domain Name System (DNS) hostname associated with the
+ receiving entity and determine the appropriate TCP port for
+ communication with the receiving entity. The process is as follows:
+
+ 1. Attempt to resolve the hostname using a [DNS-SRV] Service of
+ "sieve" and a Proto of "tcp" for the target domain (e.g.,
+ "example.net"), resulting in resource records such as
+ "_sieve._tcp.example.net.". The result of the SRV lookup, if
+ successful, will be one or more combinations of a port and
+ hostname; the ManageSieve client MUST resolve the returned
+ hostnames to IPv4/IPv6 addresses according to returned SRV record
+ weight. IP addresses from the first successfully resolved
+ hostname (with the corresponding port number returned by SRV
+ lookup) are used to connect to the server. If connection using
+ one of the IP addresses fails, the next resolved IP address is
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 9]
+
+RFC 5804 ManageSieve July 2010
+
+
+ used to connect. If connection to all resolved IP addresses
+ fails, then the resolution/connect is repeated for the next
+ hostname returned by SRV lookup.
+
+ 2. If the SRV lookup fails, the fallback SHOULD be a normal IPv4 or
+ IPv6 address record resolution to determine the IP address, where
+ the port used is the default ManageSieve port of 4190.
+
+1.9. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [KEYWORDS].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. Line breaks that do not start a new "C:" or
+ "S:" exist for editorial reasons.
+
+ Examples of authentication in this document are using DIGEST-MD5
+ [DIGEST-MD5] and GSSAPI [GSSAPI] SASL mechanisms.
+
+2. Commands
+
+ This section and its subsections describe valid ManageSieve commands.
+ Upon initial connection to the server, the client's session is in
+ non-authenticated state. Prior to successful authentication, only
+ the AUTHENTICATE, CAPABILITY, STARTTLS, LOGOUT, and NOOP (see Section
+ 2.13) commands are valid. ManageSieve extensions MAY define other
+ commands that are valid in non-authenticated state. Servers MUST
+ reject all other commands with a NO response. Clients may pipeline
+ commands (send more than one command at a time without waiting for
+ completion of the first command). However, a group of commands sent
+ together MUST NOT have an AUTHENTICATE (*), a STARTTLS, or a
+ HAVESPACE command anywhere but the last command in the list.
+
+ (*) - The only exception to this rule is when the AUTHENTICATE
+ command contains an initial response for a SASL mechanism that allows
+ clients to send data first, the mechanism is known to complete in one
+ round trip, and the mechanism doesn't negotiate a SASL security
+ layer. Two examples of such SASL mechanisms are PLAIN [PLAIN] and
+ EXTERNAL [SASL].
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 10]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.1. AUTHENTICATE Command
+
+ Arguments: String - mechanism
+ String - initial data (optional)
+
+ The AUTHENTICATE command indicates a SASL [SASL] authentication
+ mechanism to the server. If the server supports the requested
+ authentication mechanism, it performs an authentication protocol
+ exchange to identify and authenticate the user. Optionally, it also
+ negotiates a security layer for subsequent protocol interactions. If
+ the requested authentication mechanism is not supported, the server
+ rejects the AUTHENTICATE command by sending the NO response.
+
+ The authentication protocol exchange consists of a series of server
+ challenges and client responses that are specific to the selected
+ authentication mechanism. A server challenge consists of a string
+ (quoted or literal) followed by a CRLF. The contents of the string
+ is a base-64 encoding [BASE64] of the SASL data. A client response
+ consists of a string (quoted or literal) with the base-64 encoding of
+ the SASL data followed by a CRLF. If the client wishes to cancel the
+ authentication exchange, it issues a string containing a single "*".
+ If the server receives such a response, it MUST reject the
+ AUTHENTICATE command by sending a NO reply.
+
+ Note that an empty challenge/response is sent as an empty string. If
+ the mechanism dictates that the final response is sent by the server,
+ this data MAY be placed within the data portion of the SASL response
+ code to save a round trip.
+
+ The optional initial-response argument to the AUTHENTICATE command is
+ used to save a round trip when using authentication mechanisms that
+ are defined to send no data in the initial challenge. When the
+ initial-response argument is used with such a mechanism, the initial
+ empty challenge is not sent to the client and the server uses the
+ data in the initial-response argument as if it were sent in response
+ to the empty challenge. If the initial-response argument to the
+ AUTHENTICATE command is used with a mechanism that sends data in the
+ initial challenge, the server MUST reject the AUTHENTICATE command by
+ sending the NO response.
+
+ The service name specified by this protocol's profile of SASL is
+ "sieve".
+
+ Reauthentication is not supported by ManageSieve protocol's profile
+ of SASL. That is, after a successfully completed AUTHENTICATE
+ command, no more AUTHENTICATE commands may be issued in the same
+ session. After a successful AUTHENTICATE command completes, a server
+ MUST reject any further AUTHENTICATE commands with a NO reply.
+
+
+
+Melnikov & Martin Standards Track [Page 11]
+
+RFC 5804 ManageSieve July 2010
+
+
+ However, note that a server may implement the UNAUTHENTICATE
+ extension described in Section 2.14.1.
+
+ If a security layer is negotiated through the SASL authentication
+ exchange, it takes effect immediately following the CRLF that
+ concludes the successful authentication exchange for the client, and
+ the CRLF of the OK response for the server.
+
+ When a security layer takes effect, the ManageSieve protocol is reset
+ to the initial state (the state in ManageSieve after a client has
+ connected to the server). The server MUST discard any knowledge
+ obtained from the client that was not obtained from the SASL (or TLS)
+ negotiation itself. Likewise, the client MUST discard any knowledge
+ obtained from the server, such as the list of ManageSieve extensions,
+ that was not obtained from the SASL (and/or TLS) negotiation itself.
+ (Note that a client MAY compare the advertised SASL mechanisms before
+ and after authentication in order to detect an active down-
+ negotiation attack. See below.)
+
+ Once a SASL security layer is established, the server MUST re-issue
+ the capability results, followed by an OK response. This is
+ necessary to protect against man-in-the-middle attacks that alter the
+ capabilities list prior to SASL negotiation. The capability results
+ MUST include all SASL mechanisms the server was capable of
+ negotiating with that client. This is done in order to allow the
+ client to detect an active down-negotiation attack. If a user-
+ oriented client detects such a down-negotiation attack, it SHOULD
+ either notify the user (it MAY give the user the opportunity to
+ continue with the ManageSieve session in this case) or close the
+ transport connection and indicate that a down-negotiation attack
+ might be in progress. If an automated client detects a down-
+ negotiation attack, it SHOULD return or log an error indicating that
+ a possible attack might be in progress and/or SHOULD close the
+ transport connection.
+
+ When both [TLS] and SASL security layers are in effect, the TLS
+ encoding MUST be applied (when sending data) after the SASL encoding.
+
+ Server implementations SHOULD support SASL proxy authentication so
+ that an administrator can administer a user's scripts. Proxy
+ authentication is when a user authenticates as herself/himself but
+ requests the server to act (authorize) as another user.
+
+ The authorization identity generated by this [SASL] exchange is a
+ "simple username" (in the sense defined in [SASLprep]), and both
+ client and server MUST use the [SASLprep] profile of the [StringPrep]
+ algorithm to prepare these names for transmission or comparison. If
+ preparation of the authorization identity fails or results in an
+
+
+
+Melnikov & Martin Standards Track [Page 12]
+
+RFC 5804 ManageSieve July 2010
+
+
+ empty string (unless it was transmitted as the empty string), the
+ server MUST fail the authentication.
+
+ If an AUTHENTICATE command fails with a NO response, the client MAY
+ try another authentication mechanism by issuing another AUTHENTICATE
+ command. In other words, the client may request authentication types
+ in decreasing order of preference.
+
+ Note that a failed (NO) response to the AUTHENTICATE command may
+ contain one of the following response codes: AUTH-TOO-WEAK, ENCRYPT-
+ NEEDED, or TRANSITION-NEEDED. See Section 1.3 for detailed
+ description of the relevant conditions.
+
+ To ensure interoperability, both client and server implementations of
+ the ManageSieve protocol MUST implement the SCRAM-SHA-1 [SCRAM] SASL
+ mechanism, as well as [PLAIN] over [TLS].
+
+ Note: use of PLAIN over TLS reflects current use of PLAIN over TLS in
+ other email-related protocols; however, a longer-term goal is to
+ migrate email-related protocols from using PLAIN over TLS to SCRAM-
+ SHA-1 mechanism.
+
+ Examples (Note that long lines are folded for readability and are not
+ part of protocol exchange):
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: "VERSION" "1.0"
+ S: OK
+ C: Authenticate "DIGEST-MD5"
+ S: "cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
+ 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
+ cyxjaGFyc2V0PXV0Zi04"
+ C: "Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
+ QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
+ aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
+ N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
+ ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
+ A9YXV0aA=="
+ S: OK (SASL "cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZ
+ mZmZA==")
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 13]
+
+RFC 5804 ManageSieve July 2010
+
+
+ A slightly different variant of the same authentication exchange is:
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "VERSION" "1.0"
+ S: "STARTTLS"
+ S: OK
+ C: Authenticate "DIGEST-MD5"
+ S: {136}
+ S: cmVhbG09ImVsd29vZC5pbm5vc29mdC5leGFtcGxlLmNvbSIsbm9uY2U9Ik
+ 9BNk1HOXRFUUdtMmhoIixxb3A9ImF1dGgiLGFsZ29yaXRobT1tZDUtc2Vz
+ cyxjaGFyc2V0PXV0Zi04
+ C: {300+}
+ C: Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
+ QuaW5ub3NvZnQuZXhhbXBsZS5jb20iLG5vbmNlPSJPQTZNRzl0RVFHbTJo
+ aCIsbmM9MDAwMDAwMDEsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsZGlnZX
+ N0LXVyaT0ic2lldmUvZWx3b29kLmlubm9zb2Z0LmV4YW1wbGUuY29tIixy
+ ZXNwb25zZT1kMzg4ZGFkOTBkNGJiZDc2MGExNTIzMjFmMjE0M2FmNyxxb3
+ A9YXV0aA==
+ S: {56}
+ S: cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
+ C: ""
+ S: OK
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 14]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Another example demonstrating use of SASL PLAIN mechanism under TLS
+ follows. This example also demonstrate use of SASL "initial
+ response" (the second parameter to the Authenticate command):
+
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" ""
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: OK
+ C: STARTTLS
+ S: OK
+ <TLS negotiation, further commands are under TLS layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN"
+ S: "SIEVE" "fileinto vacation"
+ S: OK
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xu"
+ S: NO
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xz"
+ S: NO
+ C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xy"
+ S: BYE "Too many failed authentication attempts"
+ <Server closes connection>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 15]
+
+RFC 5804 ManageSieve July 2010
+
+
+ The following example demonstrates use of SASL "initial response".
+ It also demonstrates that an empty response can be sent as a literal
+ and that negotiating a SASL security layer results in the server
+ re-issuing server capabilities:
+
+ C: AUTHENTICATE "GSSAPI" {1488+}
+ C: YIIE[...1480 octets here ...]dA==
+ S: {208}
+ S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKic
+ [...114 octets here ...]
+ /yzpAy9p+Y0LanLskOTvMc0MnjgAa4YEr3eJ6
+ C: {0+}
+ C:
+ S: {44}
+ S: BQQF/wAMAAwAAAAAYRGFAo6W0vIHti8i1UXODgEAEAA=
+ C: {44+}
+ C: BQQE/wAMAAwAAAAAIsT1iv9UkZApw471iXt6cwEAAAE=
+ S: OK
+ <Further commands/responses are under SASL security layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "LANGUAGE" "ru"
+ S: "MAXREDIRECTS" "3"
+ S: ok
+
+2.1.1. Use of SASL PLAIN Mechanism over TLS
+
+ This section is normative for ManageSieve client implementations that
+ support SASL [PLAIN] over [TLS].
+
+ If a ManageSieve client is willing to use SASL PLAIN over TLS to
+ authenticate to the ManageSieve server, the client MUST verify the
+ server identity (see Section 2.2.1). If the server identity can't be
+ verified (e.g., the server has not provided any certificate, or if
+ the certificate verification fails), the client MUST NOT attempt to
+ authenticate using the SASL PLAIN mechanism.
+
+2.2. STARTTLS Command
+
+ Support for STARTTLS command in servers is optional. Its
+ availability is advertised with "STARTTLS" capability as described in
+ Section 1.7.
+
+ The STARTTLS command requests commencement of a TLS [TLS]
+ negotiation. The negotiation begins immediately after the CRLF in
+ the OK response. After a client issues a STARTTLS command, it MUST
+
+
+
+Melnikov & Martin Standards Track [Page 16]
+
+RFC 5804 ManageSieve July 2010
+
+
+ NOT issue further commands until a server response is seen and the
+ TLS negotiation is complete.
+
+ The STARTTLS command is only valid in non-authenticated state. The
+ server remains in non-authenticated state, even if client credentials
+ are supplied during the TLS negotiation. The SASL [SASL] EXTERNAL
+ mechanism MAY be used to authenticate once TLS client credentials are
+ successfully exchanged, but servers supporting the STARTTLS command
+ are not required to support the EXTERNAL mechanism.
+
+ After the TLS layer is established, the server MUST re-issue the
+ capability results, followed by an OK response. This is necessary to
+ protect against man-in-the-middle attacks that alter the capabilities
+ list prior to STARTTLS. This capability result MUST NOT include the
+ STARTTLS capability.
+
+ The client MUST discard cached capability information and replace it
+ with the new information. The server MAY advertise different
+ capabilities after STARTTLS.
+
+ Example:
+
+ C: StartTls
+ S: oK
+ <TLS negotiation, further commands are under TLS layer>
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "VERSION" "1.0"
+ S: "LANGUAGE" "fr"
+ S: ok
+
+2.2.1. Server Identity Check
+
+ During the TLS negotiation, the ManageSieve client MUST check its
+ understanding of the server hostname/IP address against the server's
+ identity as presented in the server Certificate message, in order to
+ prevent man-in-the-middle attacks. In this section, the client's
+ understanding of the server's identity is called the "reference
+ identity".
+
+ Checking is performed according to the following rules:
+
+ o If the reference identity is a hostname:
+
+ 1. If a subjectAltName extension of the SRVName [X509-SRV],
+ dNSName [X509] (in that order of preference) type is present
+ in the server's certificate, then it SHOULD be used as the
+
+
+
+Melnikov & Martin Standards Track [Page 17]
+
+RFC 5804 ManageSieve July 2010
+
+
+ source of the server's identity. Matching is performed as
+ described in Section 2.2.1.1, with the exception that no
+ wildcard matching is allowed for SRVName type. If the
+ certificate contains multiple names (e.g., more than one
+ dNSName field), then a match with any one of the fields is
+ considered acceptable.
+
+ 2. The client MAY use other types of subjectAltName for
+ performing comparison.
+
+ 3. The server's identity MAY also be verified by comparing the
+ reference identity to the Common Name (CN) [RFC4519] value in
+ the leaf Relative Distinguished Name (RDN) of the subjectName
+ field of the server's certificate. This comparison is
+ performed using the rules for comparison of DNS names in
+ Section 2.2.1.1, below. Although the use of the Common Name
+ value is existing practice, it is deprecated, and
+ Certification Authorities are encouraged to provide
+ subjectAltName values instead. Note that the TLS
+ implementation may represent DNs in certificates according to
+ X.500 or other conventions. For example, some X.500
+ implementations order the RDNs in a DN using a left-to-right
+ (most significant to least significant) convention instead of
+ LDAP's right-to-left convention.
+
+ o When the reference identity is an IP address, the iPAddress
+ subjectAltName SHOULD be used by the client for comparison. The
+ comparison is performed as described in Section 2.2.1.2.
+
+ If the server identity check fails, user-oriented clients SHOULD
+ either notify the user (clients MAY give the user the opportunity to
+ continue with the ManageSieve session in this case) or close the
+ transport connection and indicate that the server's identity is
+ suspect. Automated clients SHOULD return or log an error indicating
+ that the server's identity is suspect and/or SHOULD close the
+ transport connection. Automated clients MAY provide a configuration
+ setting that disables this check, but MUST provide a setting that
+ enables it.
+
+ Beyond the server identity check described in this section, clients
+ should be prepared to do further checking to ensure that the server
+ is authorized to provide the service it is requested to provide. The
+ client may need to make use of local policy information in making
+ this determination.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 18]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.2.1.1. Comparison of DNS Names
+
+ If the reference identity is an internationalized domain name,
+ conforming implementations MUST convert it to the ASCII Compatible
+ Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
+ before comparison with subjectAltName values of type dNSName.
+ Specifically, conforming implementations MUST perform the conversion
+ operation specified in Section 4 of [RFC3490] as follows:
+
+ o in step 1, the domain name SHALL be considered a "stored string";
+
+ o in step 3, set the flag called "UseSTD3ASCIIRules";
+
+ o in step 4, process each label with the "ToASCII" operation; and
+
+ o in step 5, change all label separators to U+002E (full stop).
+
+ After performing the "to-ASCII" conversion, the DNS labels and names
+ MUST be compared for equality according to the rules specified in
+ Section 3 of [RFC3490]; i.e., once all label separators are replaced
+ with U+002E (dot) they are compared in the case-insensitive manner.
+
+ The '*' (ASCII 42) wildcard character is allowed in subjectAltName
+ values of type dNSName, and then only as the left-most (least
+ significant) DNS label in that value. This wildcard matches any
+ left-most DNS label in the server name. That is, the subject
+ *.example.com matches the server names a.example.com and
+ b.example.com, but does not match example.com or a.b.example.com.
+
+2.2.1.2. Comparison of IP Addresses
+
+ When the reference identity is an IP address, the identity MUST be
+ converted to the "network byte order" octet string representation
+ [RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the
+ octet string will contain exactly four octets. For IP Version 6, as
+ specified in RFC 2460, the octet string will contain exactly sixteen
+ octets. This octet string is then compared against subjectAltName
+ values of type iPAddress. A match occurs if the reference identity
+ octet string and value octet strings are identical.
+
+2.2.1.3. Comparison of Other subjectName Types
+
+ Client implementations MAY support matching against subjectAltName
+ values of other types as described in other documents.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 19]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.3. LOGOUT Command
+
+ The client sends the LOGOUT command when it is finished with a
+ connection and wishes to terminate it. The server MUST reply with an
+ OK response. The server MUST ignore commands issued by the client
+ after the LOGOUT command.
+
+ The client SHOULD wait for the OK response before closing the
+ connection. This avoids the TCP connection going into the TIME_WAIT
+ state on the server. In order to avoid going into the TIME_WAIT TCP
+ state, the server MAY wait for a short while for the client to close
+ the TCP connection first. Whether or not the server waits for the
+ client to close the connection, it MUST then close the connection
+ itself.
+
+ Example:
+
+ C: Logout
+ S: Ok
+ <connection is terminated>
+
+2.4. CAPABILITY Command
+
+ The CAPABILITY command requests the server capabilities as described
+ earlier in this document. It has no parameters.
+
+ Example:
+
+ C: CAPABILITY
+ S: "IMPLEMENTATION" "Example1 ManageSieved v001"
+ S: "VERSION" "1.0"
+ S: "SASL" "PLAIN SCRAM-SHA-1 GSSAPI"
+ S: "SIEVE" "fileinto vacation"
+ S: "STARTTLS"
+ S: OK
+
+2.5. HAVESPACE Command
+
+ Arguments: String - name
+ Number - script size
+
+ The HAVESPACE command is used to query the server for available
+ space. Clients specify the name they wish to save the script as and
+ its size in octets. Both parameters can be used by the server to see
+ if the script with the specified name and size is within a user's
+ quota(s). For example, the server MAY use the script name to check
+ if a script would be replaced or a new one would be created. Servers
+ respond with a NO if storing a script with that name and size would
+
+
+
+Melnikov & Martin Standards Track [Page 20]
+
+RFC 5804 ManageSieve July 2010
+
+
+ fail or OK otherwise. Clients SHOULD issue this command before
+ attempting to place a script on the server.
+
+ Note that the OK response from the HAVESPACE command does not
+ constitute a guarantee of success as server disk space conditions
+ could change between the client issuing the HAVESPACE and the client
+ issuing the PUTSCRIPT commands. A QUOTA response code (see
+ Section 1.3) remains a possible (albeit unlikely) response to a
+ subsequent PUTSCRIPT with the same name and size.
+
+ Example:
+
+ C: HAVESPACE "myscript" 999999
+ S: NO (QUOTA/MAXSIZE) "Quota exceeded"
+
+ C: HAVESPACE "foobar" 435
+ S: OK
+
+2.6. PUTSCRIPT Command
+
+ Arguments: String - Script name
+ String - Script content
+
+ The PUTSCRIPT command is used by the client to submit a Sieve script
+ to the server.
+
+ If the script already exists, upon success the old script will be
+ overwritten. The old script MUST NOT be overwritten if PUTSCRIPT
+ fails in any way. A script of zero length SHOULD be disallowed.
+
+ This command places the script on the server. It does not affect
+ whether the script is processed on incoming mail, unless it replaces
+ the script that is already active. The SETACTIVE command is used to
+ mark a script as active.
+
+ When submitting large scripts, clients SHOULD use the HAVESPACE
+ command beforehand to query if the server is willing to accept a
+ script of that size.
+
+ The server MUST check the submitted script for validity, which
+ includes checking that the script complies with the Sieve grammar
+ [SIEVE] and that all Sieve extensions mentioned in the script's
+ "require" statement(s) are supported by the Sieve interpreter. (Note
+ that if the Sieve interpreter supports the Sieve "ihave" extension
+ [I-HAVE], any unrecognized/unsupported extension mentioned in the
+ "ihave" test MUST NOT cause the validation failure.) Other checks
+ such as validating the supplied command arguments for each command
+ MAY be performed. Essentially, the performed validation SHOULD be
+
+
+
+Melnikov & Martin Standards Track [Page 21]
+
+RFC 5804 ManageSieve July 2010
+
+
+ the same as performed when compiling the script for execution.
+ Implementations that use a binary representation to store compiled
+ scripts can extend the validation to a full compilation, in order to
+ avoid validating uploaded scripts multiple times.
+
+ If the script fails the validation, the server MUST reply with a NO
+ response. Any script that fails the validity test MUST NOT be stored
+ on the server. The message given with a NO response MUST be human
+ readable and SHOULD contain a specific error message giving the line
+ number of the first error. Implementors should strive to produce
+ helpful error messages similar to those given by programming language
+ compilers. Client implementations should note that this may be a
+ multiline literal string with more than one error message separated
+ by CRLFs. The human-readable message is in the language returned in
+ the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
+ encoded in UTF-8 [UTF-8].
+
+ An OK response MAY contain the WARNINGS response code. In such a
+ case the human-readable message that follows the OK response SHOULD
+ contain a specific warning message (or messages) giving the line
+ number(s) in the script that might contain errors not intended by the
+ script writer. The human-readable message is in the language
+ returned in the latest LANGUAGE capability (or in "i-default"; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
+ response code SHOULD present the message to the user.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 22]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Examples:
+
+ C: Putscript "foo" {31+}
+ C: #comment
+ C: InvalidSieveCommand
+ C:
+ S: NO "line 2: Syntax error"
+
+ C: Putscript "mysievescript" {110+}
+ C: require ["fileinto"];
+ C:
+ C: if envelope :contains "to" "tmartin+sent" {
+ C: fileinto "INBOX.sent";
+ C: }
+ S: OK
+
+ C: Putscript "myforwards" {190+}
+ C: redirect "111@example.net";
+ C:
+ C: if size :under 10k {
+ C: redirect "mobile@cell.example.com";
+ C: }
+ C:
+ C: if envelope :contains "to" "tmartin+lists" {
+ C: redirect "lists@groups.example.com";
+ C: }
+ S: OK (WARNINGS) "line 8: server redirect action
+ limit is 2, this redirect might be ignored"
+
+2.7. LISTSCRIPTS Command
+
+ This command lists the scripts the user has on the server. Upon
+ success, a list of CRLF-separated script names (each represented as a
+ quoted or literal string) is returned followed by an OK response. If
+ there exists an active script, the atom ACTIVE is appended to the
+ corresponding script name. The atom ACTIVE MUST NOT appear on more
+ than one response line.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 23]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Example:
+
+ C: Listscripts
+ S: "summer_script"
+ S: "vacation_script"
+ S: {13}
+ S: clever"script
+ S: "main_script" ACTIVE
+ S: OK
+
+ C: listscripts
+ S: "summer_script"
+ S: "main_script" active
+ S: OK
+
+2.8. SETACTIVE Command
+
+ Arguments: String - script name
+
+ This command sets a script active. If the script name is the empty
+ string (i.e., ""), then any active script is disabled. Disabling an
+ active script when there is no script active is not an error and MUST
+ result in an OK reply.
+
+ If the script does not exist on the server, then the server MUST
+ reply with a NO response. Such a reply SHOULD contain the
+ NONEXISTENT response code.
+
+ Examples:
+
+ C: Setactive "vacationscript"
+ S: Ok
+
+ C: Setactive ""
+ S: Ok
+
+ C: Setactive "baz"
+ S: No (NONEXISTENT) "There is no script by that name"
+
+ C: Setactive "baz"
+ S: No (NONEXISTENT) {31}
+ S: There is no script by that name
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 24]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.9. GETSCRIPT Command
+
+ Arguments: String - script name
+
+ This command gets the contents of the specified script. If the
+ script does not exist, the server MUST reply with a NO response.
+ Such a reply SHOULD contain the NONEXISTENT response code.
+
+ Upon success, a string with the contents of the script is returned
+ followed by an OK response.
+
+ Example:
+
+ C: Getscript "myscript"
+ S: {54}
+ S: #this is my wonderful script
+ S: reject "I reject all";
+ S:
+ S: OK
+
+2.10. DELETESCRIPT Command
+
+ Arguments: String - script name
+
+ This command is used to delete a user's Sieve script. Servers MUST
+ reply with a NO response if the script does not exist. Such
+ responses SHOULD include the NONEXISTENT response code.
+
+ The server MUST NOT allow the client to delete an active script, so
+ the server MUST reply with a NO response if attempted. Such a
+ response SHOULD contain the ACTIVE response code. If a client wishes
+ to delete an active script, it should use the SETACTIVE command to
+ disable the script first.
+
+ Example:
+
+ C: Deletescript "foo"
+ S: Ok
+
+ C: Deletescript "baz"
+ S: No (ACTIVE) "You may not delete an active script"
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 25]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.11. RENAMESCRIPT Command
+
+ Arguments: String - Old Script name
+ String - New Script name
+
+ This command is used to rename a user's Sieve script. Servers MUST
+ reply with a NO response if the old script does not exist (in which
+ case the NONEXISTENT response code SHOULD be included), or a script
+ with the new name already exists (in which case the ALREADYEXISTS
+ response code SHOULD be included). Renaming the active script is
+ allowed; the renamed script remains active.
+
+ Example:
+
+ C: Renamescript "foo" "bar"
+ S: Ok
+
+ C: Renamescript "baz" "bar"
+ S: No "bar already exists"
+
+ If the server doesn't support the RENAMESCRIPT command, the client
+ can emulate it by performing the following steps:
+
+ 1. List available scripts with LISTSCRIPTS. If the script with the
+ new script name exists, then the client should ask the user
+ whether to abort the operation, to replace the script (by issuing
+ the DELETESCRIPT <newname> after that), or to choose a different
+ name.
+
+ 2. Download the old script with GETSCRIPT <oldname>.
+
+ 3. Upload the old script with the new name: PUTSCRIPT <newname>.
+
+ 4. If the old script was active (as reported by LISTSCRIPTS in step
+ 1), then make the new script active: SETACTIVE <newname>.
+
+ 5. Delete the old script: DELETESCRIPT <oldname>.
+
+ Note that these steps don't describe how to handle various other
+ error conditions (for example, NO response containing QUOTA response
+ code in step 3). Error handling is left as an exercise for the
+ reader.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 26]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.12. CHECKSCRIPT Command
+
+ Arguments: String - Script content
+
+ The CHECKSCRIPT command is used by the client to verify Sieve script
+ validity without storing the script on the server.
+
+ The server MUST check the submitted script for syntactic validity,
+ which includes checking that all Sieve extensions mentioned in Sieve
+ script "require" statement(s) are supported by the Sieve interpreter.
+ (Note that if the Sieve interpreter supports the Sieve "ihave"
+ extension [I-HAVE], any unrecognized/unsupported extension mentioned
+ in the "ihave" test MUST NOT cause the syntactic validation failure.)
+ If the script fails this test, the server MUST reply with a NO
+ response. The message given with a NO response MUST be human
+ readable and SHOULD contain a specific error message giving the line
+ number of the first error. Implementors should strive to produce
+ helpful error messages similar to those given by programming language
+ compilers. Client implementations should note that this may be a
+ multiline literal string with more than one error message separated
+ by CRLFs. The human-readable message is in the language returned in
+ the latest LANGUAGE capability (or in "i-default"; see Section 1.7),
+ encoded in UTF-8 [UTF-8].
+
+ Examples:
+
+ C: CheckScript {31+}
+ C: #comment
+ C: InvalidSieveCommand
+ C:
+ S: NO "line 2: Syntax error"
+
+ A ManageSieve server supporting this command MUST NOT check if the
+ script will put the current user over its quota limit.
+
+ An OK response MAY contain the WARNINGS response code. In such a
+ case, the human-readable message that follows the OK response SHOULD
+ contain a specific warning message (or messages) giving the line
+ number(s) in the script that might contain errors not intended by the
+ script writer. The human-readable message is in the language
+ returned in the latest LANGUAGE capability (or in "i-default"; see
+ Section 1.7), encoded in UTF-8 [UTF-8]. A client seeing such a
+ response code SHOULD present the message to the user.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 27]
+
+RFC 5804 ManageSieve July 2010
+
+
+2.13. NOOP Command
+
+ Arguments: String - tag to echo back (optional)
+
+ The NOOP command does nothing, beyond returning a response to the
+ client. It may be used by clients for protocol re-synchronization or
+ to reset any inactivity auto-logout timer on the server.
+
+ The response to the NOOP command is always OK, followed by the TAG
+ response code together with the supplied string. If no string was
+ supplied in the NOOP command, the TAG response code MUST NOT be
+ included.
+
+ Examples:
+
+ C: NOOP
+ S: OK "NOOP completed"
+
+ C: NOOP "STARTTLS-SYNC-42"
+ S: OK (TAG {16}
+ S: STARTTLS-SYNC-42) "Done"
+
+2.14. Recommended Extensions
+
+ The UNAUTHENTICATE extension (advertised as the "UNAUTHENTICATE"
+ capability with no parameters) defines a new UNAUTHENTICATE command,
+ which allows a client to return the server to non-authenticated
+ state. Support for this extension is RECOMMENDED.
+
+2.14.1. UNAUTHENTICATE Command
+
+ The UNAUTHENTICATE command returns the server to the
+ non-authenticated state. It doesn't affect any previously
+ established TLS [TLS] or SASL (Section 2.1) security layer.
+
+ The UNAUTHENTICATE command is only valid in authenticated state. If
+ issued in a wrong state, the server MUST reject it with a NO
+ response.
+
+ The UNAUTHENTICATE command has no parameters.
+
+ When issued in the authenticated state, the UNAUTHENTICATE command
+ MUST NOT fail (i.e., it must never return anything other than OK or
+ BYE).
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 28]
+
+RFC 5804 ManageSieve July 2010
+
+
+3. Sieve URL Scheme
+
+ URI scheme name: sieve
+
+ Status: permanent
+
+ URI scheme syntax: Described using ABNF [ABNF]. Some ABNF
+ productions not defined below are from [URI-GEN].
+
+ sieveurl = sieveurl-server / sieveurl-list-scripts /
+ sieveurl-script
+
+ sieveurl-server = "sieve://" authority
+
+ sieveurl-list-scripts = "sieve://" authority ["/"]
+
+ sieveurl-script = "sieve://" authority "/"
+ [owner "/"] scriptname
+
+ authority = <defined in [URI-GEN]>
+
+ owner = *ochar
+ ;; %-encoded version of [SASL] authorization
+ ;; identity (script owner) or "userid".
+ ;;
+ ;; Empty owner is used to reference
+ ;; global scripts.
+ ;;
+ ;; Note that ASCII characters such as " ", ";",
+ ;; "&", "=", "/" and "?" must be %-encoded
+ ;; as per rule specified in [URI-GEN].
+
+ scriptname = 1*ochar
+ ;; %-encoded version of UTF-8 representation
+ ;; of the script name.
+ ;; Note that ASCII characters such as " ", ";",
+ ;; "&", "=", "/" and "?" must be %-encoded
+ ;; as per rule specified in [URI-GEN].
+
+ ochar = unreserved / pct-encoded / sub-delims-sh /
+ ":" / "@"
+ ;; Same as [URI-GEN] 'pchar',
+ ;; but without ";", "&" and "=".
+
+ unreserved = <defined in [URI-GEN]>
+
+ pct-encoded = <defined in [URI-GEN]>
+
+
+
+
+Melnikov & Martin Standards Track [Page 29]
+
+RFC 5804 ManageSieve July 2010
+
+
+ sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
+ "*" / "+" / ","
+ ;; Same as [URI-GEN] sub-delims,
+ ;; but without ";", "&" and "=".
+
+ URI scheme semantics:
+
+ A Sieve URL identifies a Sieve server or a Sieve script on a Sieve
+ server. The latter form is associated with the application/sieve
+ MIME type defined in [SIEVE]. There is no MIME type associated
+ with the former form of Sieve URI.
+
+ The server form is used in the REFERRAL response code (see Section
+ 1.3) in order to designate another server where the client should
+ perform its operations.
+
+ The script form allows to retrieve (GETSCRIPT), update
+ (PUTSCRIPT), delete (DELETESCRIPT), or activate (SETACTIVE) the
+ named script; however, the most typical action would be to
+ retrieve the script. If the script name is empty (omitted), the
+ URI requests that the client lists available scripts using the
+ LISTSCRIPTS command.
+
+ Encoding considerations:
+
+ The script name and/or the owner, if present, is in UTF-8. Non--
+ US-ASCII UTF-8 octets MUST be percent-encoded as described in
+ [URI-GEN]. US-ASCII characters such as " " (space), ";", "&",
+ "=", "/" and "?" MUST be %-encoded as described in [URI-GEN].
+ Note that "&" and "?" are in this list in order to allow for
+ future extensions.
+
+ Note that the empty owner (e.g., sieve://example.com//script) is
+ different from the missing owner (e.g.,
+ sieve://example.com/script) and is reserved for referencing global
+ scripts.
+
+ The user name (in the "authority" part), if present, is in UTF-8.
+ Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
+ [URI-GEN].
+
+ Applications/protocols that use this URI scheme name:
+ ManageSieve [RFC5804] clients and servers. Clients that can store
+ user preferences in protocols such as [LDAP] or [ACAP].
+
+ Interoperability considerations: None.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 30]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Security considerations:
+ The <scriptname> part of a ManageSieve URL might potentially disclose
+ some confidential information about the author of the script or,
+ depending on a ManageSieve implementation, about configuration of the
+ mail system. The latter might be used to prepare for a more complex
+ attack on the mail system.
+
+ Clients resolving ManageSieve URLs that wish to achieve data
+ confidentiality and/or integrity SHOULD use the STARTTLS command (if
+ supported by the server) before starting authentication, or use a
+ SASL mechanism, such as GSSAPI, that provides a confidentiality
+ security layer.
+
+ Contact: Alexey Melnikov <alexey.melnikov@isode.com>
+
+ Author/Change controller: IESG.
+
+ References: This document and RFC 5228 [SIEVE].
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (BNF) notation as specified in [ABNF]. This uses the ABNF core
+ rules as specified in Appendix A of the ABNF specification [ABNF].
+ "UTF8-2", "UTF8-3", and "UTF8-4" non-terminal are defined in [UTF-8].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper- or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ SAFE-CHAR = %x01-09 / %x0B-0C / %x0E-21 / %x23-5B /
+ %x5D-7F
+ ;; any TEXT-CHAR except QUOTED-SPECIALS
+
+ QUOTED-CHAR = SAFE-UTF8-CHAR / "\" QUOTED-SPECIALS
+
+ QUOTED-SPECIALS = DQUOTE / "\"
+
+ SAFE-UTF8-CHAR = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4
+ ;; <UTF8-2>, <UTF8-3>, and <UTF8-4>
+ ;; are defined in [UTF-8].
+
+ ATOM-CHAR = "!" / %x23-27 / %x2A-5B / %x5D-7A / %x7C-7E
+ ;; Any CHAR except ATOM-SPECIALS
+
+ ATOM-SPECIALS = "(" / ")" / "{" / SP / CTL / QUOTED-SPECIALS
+
+
+
+
+Melnikov & Martin Standards Track [Page 31]
+
+RFC 5804 ManageSieve July 2010
+
+
+ NZDIGIT = %x31-39
+ ;; 1-9
+
+ atom = 1*1024ATOM-CHAR
+
+ iana-token = atom
+ ;; MUST be registered with IANA
+
+ auth-type = DQUOTE auth-type-name DQUOTE
+
+ auth-type-name = iana-token
+ ;; as defined in SASL [SASL]
+
+ command = (command-any / command-auth /
+ command-nonauth) CRLF
+ ;; Modal based on state
+
+ command-any = command-capability / command-logout /
+ command-noop
+ ;; Valid in all states
+
+ command-auth = command-getscript / command-setactive /
+ command-listscripts / command-deletescript /
+ command-putscript / command-checkscript /
+ command-havespace /
+ command-renamescript /
+ command-unauthenticate
+ ;; Valid only in Authenticated state
+
+ command-nonauth = command-authenticate / command-starttls
+ ;; Valid only when in Non-Authenticated
+ ;; state
+
+ command-authenticate = "AUTHENTICATE" SP auth-type [SP string]
+ *(CRLF string)
+
+ command-capability = "CAPABILITY"
+
+ command-deletescript = "DELETESCRIPT" SP sieve-name
+
+ command-getscript = "GETSCRIPT" SP sieve-name
+
+ command-havespace = "HAVESPACE" SP sieve-name SP number
+
+ command-listscripts = "LISTSCRIPTS"
+
+ command-noop = "NOOP" [SP string]
+
+
+
+
+Melnikov & Martin Standards Track [Page 32]
+
+RFC 5804 ManageSieve July 2010
+
+
+ command-logout = "LOGOUT"
+
+ command-putscript = "PUTSCRIPT" SP sieve-name SP sieve-script
+
+ command-checkscript = "CHECKSCRIPT" SP sieve-script
+
+ sieve-script = string
+
+ command-renamescript = "RENAMESCRIPT" SP old-sieve-name SP
+ new-sieve-name
+
+ old-sieve-name = sieve-name
+
+ new-sieve-name = sieve-name
+
+ command-setactive = "SETACTIVE" SP active-sieve-name
+
+ command-starttls = "STARTTLS"
+
+ command-unauthenticate= "UNAUTHENTICATE"
+
+ extend-token = atom
+ ;; MUST be defined by a Standards Track or
+ ;; IESG-approved experimental protocol
+ ;; extension
+
+ extension-data = extension-item *(SP extension-item)
+
+ extension-item = extend-token / string / number /
+ "(" [extension-data] ")"
+
+ literal-c2s = "{" number "+}" CRLF *OCTET
+ ;; The number represents the number of
+ ;; octets.
+ ;; This type of literal can only be sent
+ ;; from the client to the server.
+
+ literal-s2c = "{" number "}" CRLF *OCTET
+ ;; Almost identical to literal-c2s,
+ ;; but with no '+' character.
+ ;; The number represents the number of
+ ;; octets.
+ ;; This type of literal can only be sent
+ ;; from the server to the client.
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 33]
+
+RFC 5804 ManageSieve July 2010
+
+
+ number = (NZDIGIT *DIGIT) / "0"
+ ;; A 32-bit unsigned number
+ ;; with no extra leading zeros.
+ ;; (0 <= n < 4,294,967,296)
+
+ number-str = string
+ ;; <number> encoded as a <string>.
+
+ quoted = DQUOTE *1024QUOTED-CHAR DQUOTE
+ ;; limited to 1024 octets between the <">s
+
+ resp-code = "AUTH-TOO-WEAK" / "ENCRYPT-NEEDED" / "QUOTA"
+ ["/" ("MAXSCRIPTS" / "MAXSIZE")] /
+ resp-code-sasl /
+ resp-code-referral /
+ "TRANSITION-NEEDED" / "TRYLATER" /
+ "ACTIVE" / "NONEXISTENT" /
+ "ALREADYEXISTS" / "WARNINGS" /
+ "TAG" SP string /
+ resp-code-ext
+
+ resp-code-referral = "REFERRAL" SP sieveurl
+
+ resp-code-sasl = "SASL" SP string
+
+ resp-code-name = iana-token
+ ;; The response code name is hierarchical,
+ ;; separated by '/'.
+ ;; The response code name MUST NOT start
+ ;; with '/'.
+
+ resp-code-ext = resp-code-name [SP extension-data]
+ ;; unknown response codes MUST be tolerated
+ ;; by the client.
+
+ response = response-authenticate /
+ response-logout /
+ response-getscript /
+ response-setactive /
+ response-listscripts /
+ response-deletescript /
+ response-putscript /
+ response-checkscript /
+ response-capability /
+ response-havespace /
+ response-starttls /
+ response-renamescript /
+ response-noop /
+
+
+
+Melnikov & Martin Standards Track [Page 34]
+
+RFC 5804 ManageSieve July 2010
+
+
+ response-unauthenticate
+
+ response-authenticate = *(string CRLF)
+ ((response-ok [response-capability]) /
+ response-nobye)
+ ;; <response-capability> is REQUIRED if a
+ ;; SASL security layer was negotiated and
+ ;; MUST be omitted otherwise.
+
+ response-capability = *(single-capability) response-oknobye
+
+ single-capability = capability-name [SP string] CRLF
+
+ capability-name = string
+
+ ;; Note that literal-s2c is allowed.
+
+ initial-capabilities = DQUOTE "IMPLEMENTATION" DQUOTE SP string /
+ DQUOTE "SASL" DQUOTE SP sasl-mechs /
+ DQUOTE "SIEVE" DQUOTE SP sieve-extensions /
+ DQUOTE "MAXREDIRECTS" DQUOTE SP number-str /
+ DQUOTE "NOTIFY" DQUOTE SP notify-mechs /
+ DQUOTE "STARTTLS" DQUOTE /
+ DQUOTE "LANGUAGE" DQUOTE SP language /
+ DQUOTE "VERSION" DQUOTE SP version /
+ DQUOTE "OWNER" DQUOTE SP string
+ ;; Each capability conforms to
+ ;; the syntax for single-capability.
+ ;; Also, note that the capability name
+ ;; can be returned as either literal-s2c
+ ;; or quoted, even though only "quoted"
+ ;; string is shown above.
+
+ version = ( DQUOTE "1.0" DQUOTE ) / version-ext
+
+ version-ext = DQUOTE ver-major "." ver-minor DQUOTE
+ ; Future versions specified in updates
+ ; to this document. An increment to
+ ; the ver-major means a backward-incompatible
+ ; change to the protocol, e.g., "3.5" (ver-major "3")
+ ; is not backward-compatible with any "2.X" version.
+ ; Any version "Z.W" MUST be backward compatible
+ ; with any version "Z.Q", where Q < W.
+ ; For example, version "2.4" is backward compatible
+ ; with version "2.0", "2.1", "2.2", and "2.3".
+
+ ver-major = number
+
+
+
+
+Melnikov & Martin Standards Track [Page 35]
+
+RFC 5804 ManageSieve July 2010
+
+
+ ver-minor = number
+
+ sasl-mechs = string
+ ; Space-separated list of SASL mechanisms,
+ ; each SASL mechanism name complies with rules
+ ; specified in [SASL].
+ ; Can be empty.
+
+ sieve-extensions = string
+ ; Space-separated list of supported SIEVE extensions.
+ ; Can be empty.
+
+ language = string
+ ; Contains <Language-Tag> from [RFC5646].
+
+
+ notify-mechs = string
+ ; Space-separated list of URI schema parts
+ ; for supported notification [NOTIFY] methods.
+ ; MUST NOT be empty.
+
+ response-deletescript = response-oknobye
+
+ response-getscript = (sieve-script CRLF response-ok) /
+ response-nobye
+
+ response-havespace = response-oknobye
+
+ response-listscripts = *(sieve-name [SP "ACTIVE"] CRLF)
+ response-oknobye
+ ;; ACTIVE may only occur with one sieve-name
+
+ response-logout = response-oknobye
+
+ response-unauthenticate= response-oknobye
+ ;; "NO" response can only be returned when
+ ;; the command is issued in a wrong state
+ ;; or has a wrong number of parameters
+
+ response-ok = "OK" [SP "(" resp-code ")"]
+ [SP string] CRLF
+ ;; The string contains human-readable text
+ ;; encoded as UTF-8.
+
+ response-nobye = ("NO" / "BYE") [SP "(" resp-code ")"]
+ [SP string] CRLF
+ ;; The string contains human-readable text
+ ;; encoded as UTF-8.
+
+
+
+Melnikov & Martin Standards Track [Page 36]
+
+RFC 5804 ManageSieve July 2010
+
+
+ response-oknobye = response-ok / response-nobye
+
+ response-noop = response-ok
+
+ response-putscript = response-oknobye
+
+ response-checkscript = response-oknobye
+
+ response-renamescript = response-oknobye
+
+ response-setactive = response-oknobye
+
+ response-starttls = (response-ok response-capability) /
+ response-nobye
+
+ sieve-name = string
+ ;; See Section 1.6 for the full list of
+ ;; prohibited characters.
+ ;; Empty string is not allowed.
+
+ active-sieve-name = string
+ ;; See Section 1.6 for the full list of
+ ;; prohibited characters.
+ ;; This is similar to <sieve-name>, but
+ ;; empty string is allowed and has a special
+ ;; meaning.
+
+ string = quoted / literal-c2s / literal-s2c
+ ;; literal-c2s is only allowed when sent
+ ;; from the client to the server.
+ ;; literal-s2c is only allowed when sent
+ ;; from the server to the client.
+ ;; quoted is allowed in either direction.
+
+5. Security Considerations
+
+ The AUTHENTICATE command uses SASL [SASL] to provide authentication
+ and authorization services. Integrity and privacy services can be
+ provided by [SASL] and/or [TLS]. When a SASL mechanism is used, the
+ security considerations for that mechanism apply.
+
+ This protocol's transactions are susceptible to passive observers or
+ man-in-the-middle attacks that alter the data, unless the optional
+ encryption and integrity services of the SASL (via the AUTHENTICATE
+ command) and/or [TLS] (via the STARTTLS command) are enabled, or an
+ external security mechanism is used for protection. It may be useful
+ to allow configuration of both clients and servers to refuse to
+ transfer sensitive information in the absence of strong encryption.
+
+
+
+Melnikov & Martin Standards Track [Page 37]
+
+RFC 5804 ManageSieve July 2010
+
+
+ If an implementation supports SASL mechanisms that are vulnerable to
+ passive eavesdropping attacks (such as [PLAIN]), then the
+ implementation MUST support at least one configuration where these
+ SASL mechanisms are not advertised or used without the presence of an
+ external security layer such as [TLS].
+
+ Some response codes returned on failed AUTHENTICATE command may
+ disclose whether or not the username is valid (e.g., TRANSITION-
+ NEEDED), so server implementations SHOULD provide the ability to
+ disable these features (or make them not conditional on a per-user
+ basis) for sites concerned about such disclosure. In the case of
+ ENCRYPT-NEEDED, if it is applied to all identities then no extra
+ information is disclosed, but if it is applied on a per-user basis it
+ can disclose information.
+
+ A compromised or malicious server can use the TRANSITION-NEEDED
+ response code to force the client that is configured to use a
+ mechanism that does not disclose the user's password to the server
+ (e.g., Kerberos), to send the bare password to the server. Clients
+ SHOULD have the ability to disable the password transition feature,
+ or disclose that risk to the user and offer the user an option of how
+ to proceed.
+
+6. IANA Considerations
+
+ IANA has reserved TCP port number 4190 for use with the ManageSieve
+ protocol described in this document.
+
+ IANA has registered the "sieve" URI scheme defined in Section 3 of
+ this document.
+
+ IANA has registered "sieve" in the "GSSAPI/Kerberos/SASL Service
+ Names" registry.
+
+ IANA has created a new registry for ManageSieve capabilities. The
+ registration template for ManageSieve capabilities is specified in
+ Section 6.1. ManageSieve protocol capabilities MUST be specified in
+ a Standards-Track or IESG-approved Experimental RFC.
+
+ IANA has created a new registry for ManageSieve response codes. The
+ registration template for ManageSieve response codes is specified in
+ Section 6.3. ManageSieve protocol response codes MUST be specified
+ in a Standards-Track or IESG-approved Experimental RFC.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 38]
+
+RFC 5804 ManageSieve July 2010
+
+
+6.1. ManageSieve Capability Registration Template
+
+ To: iana@iana.org
+ Subject: ManageSieve Capability Registration
+
+ Please register the following ManageSieve capability:
+
+ Capability name:
+ Description:
+ Relevant publications:
+ Person & email address to contact for further information:
+ Author/Change controller:
+
+6.2. Registration of Initial ManageSieve Capabilities
+
+ To: iana@iana.org
+ Subject: ManageSieve Capability Registration
+
+ Please register the following ManageSieve capabilities:
+
+ Capability name: IMPLEMENTATION
+ Description: Its value contains the name of the server
+ implementation and its version.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: SASL
+ Description: Its value contains a space-separated list of SASL
+ mechanisms supported by the server.
+ Relevant publications: this RFC, Sections 1.7 and 2.1.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: SIEVE
+ Description: Its value contains a space-separated list of supported
+ SIEVE extensions.
+ Relevant publications: this RFC, Section 1.7. Also [SIEVE].
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 39]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Capability name: STARTTLS
+ Description: This capability is returned if the server supports TLS
+ (STARTTLS command).
+ Relevant publications: this RFC, Sections 1.7 and 2.2.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: NOTIFY
+ Description: This capability is returned if the server supports the
+ 'enotify' [NOTIFY] Sieve extension.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: MAXREDIRECTS
+ Description: This capability returns the limit on the number of
+ Sieve "redirect" actions a script can perform during a
+ single evaluation. The value is a non-negative number
+ represented as a ManageSieve string.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: LANGUAGE
+ Description: The language (<Language-Tag> from [RFC5646]) currently
+ used for human-readable error messages.
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Capability name: OWNER
+ Description: Its value contains the UTF-8-encoded name of the
+ currently logged-in user ("authorization identity"
+ according to RFC 4422).
+ Relevant publications: this RFC, Section 1.7.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 40]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Capability name: VERSION
+ Description: This capability is returned if the server is compliant
+ with RFC 5804; i.e., that it supports RENAMESCRIPT,
+ CHECKSCRIPT, and NOOP commands.
+ Relevant publications: this RFC, Sections 2.11, 2.12, and 2.13.
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+6.3. ManageSieve Response Code Registration Template
+
+ To: iana@iana.org
+ Subject: ManageSieve Response Code Registration
+
+ Please register the following ManageSieve response code:
+
+ Response Code:
+ Arguments (use ABNF to specify syntax, or the word NONE if none
+ can be specified):
+ Purpose:
+ Published Specification(s):
+ Person & email address to contact for further information:
+ Author/Change controller:
+
+6.4. Registration of Initial ManageSieve Response Codes
+
+ To: iana@iana.org
+ Subject: ManageSieve Response Code Registration
+
+ Please register the following ManageSieve response codes:
+
+ Response Code: AUTH-TOO-WEAK
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code is returned in the NO response from
+ an AUTHENTICATE command. It indicates that site
+ security policy forbids the use of the requested
+ mechanism for the specified authentication identity.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 41]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: ENCRYPT-NEEDED
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code is returned in the NO response from
+ an AUTHENTICATE command. It indicates that site
+ security policy requires the use of a strong
+ encryption mechanism for the specified authentication
+ identity and mechanism.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: QUOTA
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined quota constraints. If
+ this response code is returned in the OK response, it
+ can mean that the user is near its quota or that the
+ user exceeded its quota, but the server supports soft
+ quotas.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: QUOTA/MAXSCRIPTS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined limit on the number of
+ Sieve scripts. If this response code is returned in
+ the OK response, it can mean that the user is near its
+ quota or that the user exceeded its quota, but the
+ server supports soft quotas. This response code is a
+ more specific version of the QUOTA response code.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 42]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: QUOTA/MAXSIZE
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: If this response code is returned in the NO/BYE
+ response, it means that the command would have placed
+ the user above the site-defined maximum script size.
+ If this response code is returned in the OK response,
+ it can mean that the user is near its quota or that
+ the user exceeded its quota, but the server supports
+ soft quotas. This response code is a more specific
+ version of the QUOTA response code.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: REFERRAL
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): <sieveurl>
+ Purpose: This response code may be returned with a BYE result
+ from any command, and includes a mandatory parameter
+ that indicates what server to access to manage this
+ user's Sieve scripts. The server will be specified by
+ a Sieve URL (see Section 3). The scriptname portion
+ of the URL MUST NOT be specified. The client should
+ authenticate to the specified server and use it for
+ all further commands in the current session.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: SASL
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): <string>
+ Purpose: This response code can occur in the OK response to a
+ successful AUTHENTICATE command and includes the
+ optional final server response data from the server as
+ specified by [SASL].
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 43]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: TRANSITION-NEEDED
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code occurs in a NO response of an
+ AUTHENTICATE command. It indicates that the user name
+ is valid, but the entry in the authentication database
+ needs to be updated in order to permit authentication
+ with the specified mechanism. This is typically done
+ by establishing a secure channel using TLS, followed
+ by authenticating once using the [PLAIN]
+ authentication mechanism. The selected mechanism
+ SHOULD then work for authentications in subsequent
+ sessions.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: TRYLATER
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed due to a temporary server failure.
+ The client MAY continue using local information and
+ try the command later. This response code only make
+ sense when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: ACTIVE
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because it is not allowed on the
+ active script, for example, DELETESCRIPT on the active
+ script. This response code only makes sense when
+ returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 44]
+
+RFC 5804 ManageSieve July 2010
+
+
+ Response Code: NONEXISTENT
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because the referenced script name
+ doesn't exist. This response code only makes sense
+ when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: ALREADYEXISTS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: A command failed because the referenced script name
+ already exists. This response code only makes sense
+ when returned in a NO/BYE response.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: WARNINGS
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): NONE
+ Purpose: This response code MAY be returned by the server in
+ the OK response (but it might be returned with the NO/
+ BYE response as well) and signals the client that even
+ though the script is syntactically valid, it might
+ contain errors not intended by the script writer.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+ Response Code: TAG
+ Arguments (use ABNF to specify syntax, or the word NONE if none can
+ be specified): string
+ Purpose: This response code name is followed by a string
+ specified in the command that caused this response.
+ It is typically used for client state synchronization.
+ Published Specification(s): [RFC5804]
+ Person & email address to contact for further information:
+ Alexey Melnikov <alexey.melnikov@isode.com>
+ Author/Change controller: IESG.
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 45]
+
+RFC 5804 ManageSieve July 2010
+
+
+7. Internationalization Considerations
+
+ The LANGUAGE capability (see Section 1.7) allows a client to discover
+ the current language used in all human-readable responses that might
+ be returned at the end of any OK/NO/BYE response. Human-readable
+ text in OK responses typically doesn't need to be shown to the user,
+ unless it is returned in response to a PUTSCRIPT or CHECKSCRIPT
+ command that also contains the WARNINGS response code (Section 1.3).
+ Human-readable text from NO/BYE responses is intended be shown to the
+ user, unless the client can automatically handle failure of the
+ command that caused such a response. Clients SHOULD use response
+ codes (Section 1.3) for automatic error handling. Response codes MAY
+ also be used by the client to present error messages in a language
+ understood by the user, for example, if the LANGUAGE capability
+ doesn't return a language understood by the user.
+
+ Note that the human-readable text from OK (WARNINGS) or NO/BYE
+ responses for PUTSCRIPT/CHECKSCRIPT commands is intended for advanced
+ users that understand Sieve language. Such advanced users are often
+ sophisticated enough to be able to handle whatever language the
+ server is using, even if it is not their preferred language, and will
+ want to see error/warning text no matter what language the server
+ puts it in.
+
+ A client that generates Sieve script automatically, for example, if
+ the script is generated without user intervention or from a UI that
+ presents an abstract list of conditions and corresponding actions,
+ SHOULD NOT present warning/error messages to the user, because the
+ user might not even be aware that the client is using Sieve
+ underneath. However, if the client has a debugging mode, such
+ warnings/errors SHOULD be available in the debugging mode.
+
+ Note that this document doesn't provide a way to modify the currently
+ used language. It is expected that a future extension will address
+ that.
+
+8. Acknowledgements
+
+ Thanks to Simon Josefsson, Larry Greenfield, Allen Johnson, Chris
+ Newman, Lyndon Nerenberg, Tim Showalter, Sarah Robeson, Walter Wong,
+ Barry Leiba, Arnt Gulbrandsen, Stephan Bosch, Ken Murchison, Phil
+ Pennock, Ned Freed, Jeffrey Hutzelman, Mark E. Mallett, Dilyan
+ Palauzov, Dave Cridland, Aaron Stone, Robert Burrell Donkin, Patrick
+ Ben Koetter, Bjoern Hoehrmann, Martin Duerst, Pasi Eronen, Magnus
+ Westerlund, Tim Polk, and Julien Coloos for help with this document.
+ Special thank you to Phil Pennock for providing text for the NOOP
+ command, as well as finding various bugs in the document.
+
+
+
+
+Melnikov & Martin Standards Track [Page 46]
+
+RFC 5804 ManageSieve July 2010
+
+
+9. References
+
+9.1. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", STD 68, RFC 5234, January 2008.
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November
+ 1997.
+
+ [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
+ Encodings", RFC 4648, October 2006.
+
+ [DNS-SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR
+ for specifying the location of services (DNS SRV)",
+ RFC 2782, February 2000.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [NET-UNICODE] Klensin, J. and M. Padlipsky, "Unicode Format for
+ Network Interchange", RFC 5198, March 2008.
+
+ [NOTIFY] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
+ "Sieve Email Filtering: Extension for Notifications",
+ RFC 5435, January 2009.
+
+ [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
+ Languages", BCP 18, RFC 2277, January 1998.
+
+ [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version
+ 6 (IPv6) Specification", RFC 2460, December 1998.
+
+ [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
+ "Internationalizing Domain Names in Applications
+ (IDNA)", RFC 3490, March 2003.
+
+ [RFC4519] Sciberras, A., "Lightweight Directory Access Protocol
+ (LDAP): Schema for User Applications", RFC 4519, June
+ 2006.
+
+ [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
+ Languages", BCP 47, RFC 5646, September 2009.
+
+ [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
+ September 1981.
+
+
+
+
+Melnikov & Martin Standards Track [Page 47]
+
+RFC 5804 ManageSieve July 2010
+
+
+ [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication
+ and Security Layer (SASL)", RFC 4422, June 2006.
+
+ [SASLprep] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+ [SCRAM] Menon-Sen, A., Melnikov, A., Newman, C., and N.
+ Williams, "Salted Challenge Response Authentication
+ Mechanism (SCRAM) SASL and GSS-API Mechanisms", RFC
+ 5802, July 2010.
+
+ [SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email
+ Filtering Language", RFC 5228, January 2008.
+
+ [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
+ Security (TLS) Protocol Version 1.2", RFC 5246, August
+ 2008.
+
+ [URI-GEN] Berners-Lee, T., Fielding, R., and L. Masinter,
+ "Uniform Resource Identifier (URI): Generic Syntax",
+ STD 66, RFC 3986, January 2005.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
+ Housley, R., and W. Polk, "Internet X.509 Public Key
+ Infrastructure Certificate and Certificate Revocation
+ List (CRL) Profile", RFC 5280, May 2008.
+
+ [X509-SRV] Santesson, S., "Internet X.509 Public Key
+ Infrastructure Subject Alternative Name for Expression
+ of Service Name", RFC 4985, August 2007.
+
+9.2. Informative References
+
+ [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication
+ as a SASL Mechanism", RFC 2831, May 2000.
+
+ [GSSAPI] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
+ Authentication and Security Layer (SASL) Mechanism",
+ RFC 4752, November 2006.
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 48]
+
+RFC 5804 ManageSieve July 2010
+
+
+ [I-HAVE] Freed, N., "Sieve Email Filtering: Ihave Extension",
+ RFC 5463, March 2009.
+
+ [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [LDAP] Zeilenga, K., "Lightweight Directory Access Protocol
+ (LDAP): Technical Specification Road Map", RFC 4510,
+ June 2006.
+
+ [PLAIN] Zeilenga, K., "The PLAIN Simple Authentication and
+ Security Layer (SASL) Mechanism", RFC 4616, August
+ 2006.
+
+Authors' Addresses
+
+ Alexey Melnikov (editor)
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Tim Martin
+ BeThereBeSquare, Inc.
+ 672 Haight st.
+ San Francisco, CA 94117
+ USA
+
+ Phone: +1 510 260-4175
+ EMail: timmartin@alumni.cmu.edu
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Martin Standards Track [Page 49]
+
