rohrpost

rfc2822.txt (110695B)

---

 
 
 
 
 
 
 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
 
 
 
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    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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 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]
 
 
 
 
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 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
 
 
 
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 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.
 
 
 
 
 
 
 
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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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 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
 
 
 
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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
 
 
 
 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.
 
 
 
 
 
 
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 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.
 
 
 
 
 
 
 
 
 
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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:".
 
 
 
 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:",
 
 
 
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 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
 
 
 
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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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    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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                         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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    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
 
 
 
 
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 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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    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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 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
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 40]
 
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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 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".
 ----
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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    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.
 
 
 
 
 
 
 
 
 
 
 
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 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".
 ----
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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    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".
 ----
 
 
 
 
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 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]
 
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 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".
 ----
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 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]
 
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 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]
 
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 ----
 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.*
 
 
 
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    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]
 
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 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]