rohrpost

rfc5322.txt (122322B)

---

 
 
 
 
 
 
 Network Working Group                                    P. Resnick, Ed.
 Request for Comments: 5322                         Qualcomm Incorporated
 Obsoletes: 2822                                             October 2008
 Updates: 4021
 Category: Standards Track
 
 
                         Internet Message Format
 
 Status of This Memo
 
    This document specifies an Internet standards track protocol for the
    Internet community, and requests discussion and suggestions for
    improvements.  Please refer to the current edition of the "Internet
    Official Protocol Standards" (STD 1) for the standardization state
    and status of this protocol.  Distribution of this memo is unlimited.
 
 Abstract
 
    This document specifies the Internet Message Format (IMF), a syntax
    for text messages that are sent between computer users, within the
    framework of "electronic mail" messages.  This specification is a
    revision of Request For Comments (RFC) 2822, which itself superseded
    Request For Comments (RFC) 822, "Standard for the Format of ARPA
    Internet Text Messages", updating it to reflect current practice and
    incorporating incremental changes that were specified in other RFCs.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 Table of Contents
 
    1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
      1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
      1.2.  Notational Conventions . . . . . . . . . . . . . . . . . .  5
        1.2.1.  Requirements Notation  . . . . . . . . . . . . . . . .  5
        1.2.2.  Syntactic Notation . . . . . . . . . . . . . . . . . .  5
        1.2.3.  Structure of This Document . . . . . . . . . . . . . .  5
    2.  Lexical Analysis of Messages . . . . . . . . . . . . . . . . .  6
      2.1.  General Description  . . . . . . . . . . . . . . . . . . .  6
        2.1.1.  Line Length Limits . . . . . . . . . . . . . . . . . .  7
      2.2.  Header Fields  . . . . . . . . . . . . . . . . . . . . . .  8
        2.2.1.  Unstructured Header Field Bodies . . . . . . . . . . .  8
        2.2.2.  Structured Header Field Bodies . . . . . . . . . . . .  8
        2.2.3.  Long Header Fields . . . . . . . . . . . . . . . . . .  8
      2.3.  Body . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
    3.  Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
      3.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
      3.2.  Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
        3.2.1.  Quoted characters  . . . . . . . . . . . . . . . . . . 10
        3.2.2.  Folding White Space and Comments . . . . . . . . . . . 11
        3.2.3.  Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
        3.2.4.  Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
        3.2.5.  Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
      3.3.  Date and Time Specification  . . . . . . . . . . . . . . . 14
      3.4.  Address Specification  . . . . . . . . . . . . . . . . . . 16
        3.4.1.  Addr-Spec Specification  . . . . . . . . . . . . . . . 17
      3.5.  Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
      3.6.  Field Definitions  . . . . . . . . . . . . . . . . . . . . 19
        3.6.1.  The Origination Date Field . . . . . . . . . . . . . . 22
        3.6.2.  Originator Fields  . . . . . . . . . . . . . . . . . . 22
        3.6.3.  Destination Address Fields . . . . . . . . . . . . . . 23
        3.6.4.  Identification Fields  . . . . . . . . . . . . . . . . 25
        3.6.5.  Informational Fields . . . . . . . . . . . . . . . . . 27
        3.6.6.  Resent Fields  . . . . . . . . . . . . . . . . . . . . 28
        3.6.7.  Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
        3.6.8.  Optional Fields  . . . . . . . . . . . . . . . . . . . 30
    4.  Obsolete Syntax  . . . . . . . . . . . . . . . . . . . . . . . 31
      4.1.  Miscellaneous Obsolete Tokens  . . . . . . . . . . . . . . 32
      4.2.  Obsolete Folding White Space . . . . . . . . . . . . . . . 33
      4.3.  Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
      4.4.  Obsolete Addressing  . . . . . . . . . . . . . . . . . . . 35
      4.5.  Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
        4.5.1.  Obsolete Origination Date Field  . . . . . . . . . . . 36
        4.5.2.  Obsolete Originator Fields . . . . . . . . . . . . . . 36
        4.5.3.  Obsolete Destination Address Fields  . . . . . . . . . 37
        4.5.4.  Obsolete Identification Fields . . . . . . . . . . . . 37
        4.5.5.  Obsolete Informational Fields  . . . . . . . . . . . . 37
 
 
 
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        4.5.6.  Obsolete Resent Fields . . . . . . . . . . . . . . . . 38
        4.5.7.  Obsolete Trace Fields  . . . . . . . . . . . . . . . . 38
        4.5.8.  Obsolete optional fields . . . . . . . . . . . . . . . 38
    5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 38
    6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 39
    Appendix A.     Example Messages . . . . . . . . . . . . . . . . . 43
    Appendix A.1.   Addressing Examples  . . . . . . . . . . . . . . . 44
    Appendix A.1.1. A Message from One Person to Another with
                    Simple Addressing  . . . . . . . . . . . . . . . . 44
    Appendix A.1.2. Different Types of Mailboxes . . . . . . . . . . . 45
    Appendix A.1.3. Group Addresses  . . . . . . . . . . . . . . . . . 45
    Appendix A.2.   Reply Messages . . . . . . . . . . . . . . . . . . 46
    Appendix A.3.   Resent Messages  . . . . . . . . . . . . . . . . . 47
    Appendix A.4.   Messages with Trace Fields . . . . . . . . . . . . 48
    Appendix A.5.   White Space, Comments, and Other Oddities  . . . . 49
    Appendix A.6.   Obsoleted Forms  . . . . . . . . . . . . . . . . . 50
    Appendix A.6.1. Obsolete Addressing  . . . . . . . . . . . . . . . 50
    Appendix A.6.2. Obsolete Dates . . . . . . . . . . . . . . . . . . 50
    Appendix A.6.3. Obsolete White Space and Comments  . . . . . . . . 51
    Appendix B.     Differences from Earlier Specifications  . . . . . 52
    Appendix C.     Acknowledgements . . . . . . . . . . . . . . . . . 53
    7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
      7.1.  Normative References . . . . . . . . . . . . . . . . . . . 55
      7.2.  Informative References . . . . . . . . . . . . . . . . . . 55
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 1.  Introduction
 
 1.1.  Scope
 
    This document specifies the Internet Message Format (IMF), a syntax
    for text messages that are sent between computer users, within the
    framework of "electronic mail" messages.  This specification is an
    update to [RFC2822], which itself superseded [RFC0822], updating it
    to reflect current practice and incorporating incremental changes
    that were specified in other RFCs such as [RFC1123].
 
    This document specifies a syntax only for text messages.  In
    particular, it makes no provision for the transmission of images,
    audio, or other sorts of structured data in electronic mail messages.
    There are several extensions published, such as the MIME document
    series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
    for the transmission of such data through electronic mail, either by
    extending the syntax provided here or by structuring such messages to
    conform to this syntax.  Those mechanisms are outside of the scope of
    this specification.
 
    In the context of electronic mail, messages are viewed as having an
    envelope and contents.  The envelope contains whatever information is
    needed to accomplish transmission and delivery.  (See [RFC5321] for a
    discussion of the envelope.)  The contents comprise the object to be
    delivered to the recipient.  This specification applies only to the
    format and some of the semantics of message contents.  It contains no
    specification of the information in the envelope.
 
    However, some message systems may use information from the contents
    to create the envelope.  It is intended that this specification
    facilitate the acquisition of such information by programs.
 
    This specification is intended as a definition of what message
    content format is to be passed between systems.  Though some message
    systems locally store messages in this format (which eliminates the
    need for translation between formats) and others use formats that
    differ from the one specified in this specification, local storage is
    outside of the scope of this specification.
 
       Note: This specification is not intended to dictate the internal
       formats used by sites, the specific message system features that
       they are expected to support, or any of the characteristics of
       user interface programs that create or read messages.  In
       addition, this document does not specify an encoding of the
       characters for either transport or storage; that is, it does not
       specify the number of bits used or how those bits are specifically
       transferred over the wire or stored on disk.
 
 
 
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 1.2.  Notational Conventions
 
 1.2.1.  Requirements Notation
 
    This document occasionally uses terms that appear in capital letters.
    When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
    NOT", and "MAY" appear capitalized, they are being used to indicate
    particular requirements of this specification.  A discussion of the
    meanings of these terms appears in [RFC2119].
 
 1.2.2.  Syntactic Notation
 
    This specification uses the Augmented Backus-Naur Form (ABNF)
    [RFC5234] notation for the formal definitions of the syntax of
    messages.  Characters will be specified either by a decimal value
    (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
    a case-insensitive literal value enclosed in quotation marks (e.g.,
    "A" for either uppercase or lowercase A).
 
 1.2.3.  Structure of This Document
 
    This document is divided into several sections.
 
    This section, section 1, is a short introduction to the document.
 
    Section 2 lays out the general description of a message and its
    constituent parts.  This is an overview to help the reader understand
    some of the general principles used in the later portions of this
    document.  Any examples in this section MUST NOT be taken as
    specification of the formal syntax of any part of a message.
 
    Section 3 specifies formal ABNF rules for the structure of each part
    of a message (the syntax) and describes the relationship between
    those parts and their meaning in the context of a message (the
    semantics).  That is, it lays out the actual rules for the structure
    of each part of a message (the syntax) as well as a description of
    the parts and instructions for their interpretation (the semantics).
    This includes analysis of the syntax and semantics of subparts of
    messages that have specific structure.  The syntax included in
    section 3 represents messages as they MUST be created.  There are
    also notes in section 3 to indicate if any of the options specified
    in the syntax SHOULD be used over any of the others.
 
    Both sections 2 and 3 describe messages that are legal to generate
    for purposes of this specification.
 
 
 
 
 
 
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    Section 4 of this document specifies an "obsolete" syntax.  There are
    references in section 3 to these obsolete syntactic elements.  The
    rules of the obsolete syntax are elements that have appeared in
    earlier versions of this specification or have previously been widely
    used in Internet messages.  As such, these elements MUST be
    interpreted by parsers of messages in order to be conformant to this
    specification.  However, since items in this syntax have been
    determined to be non-interoperable or to cause significant problems
    for recipients of messages, they MUST NOT be generated by creators of
    conformant messages.
 
    Section 5 details security considerations to take into account when
    implementing this specification.
 
    Appendix A lists examples of different sorts of messages.  These
    examples are not exhaustive of the types of messages that appear on
    the Internet, but give a broad overview of certain syntactic forms.
 
    Appendix B lists the differences between this specification and
    earlier specifications for Internet messages.
 
    Appendix C contains acknowledgements.
 
 2.  Lexical Analysis of Messages
 
 2.1.  General Description
 
    At the most basic level, a message is a series of characters.  A
    message that is conformant with this specification is composed of
    characters with values in the range of 1 through 127 and interpreted
    as US-ASCII [ANSI.X3-4.1986] characters.  For brevity, this document
    sometimes refers to this range of characters as simply "US-ASCII
    characters".
 
       Note: This document specifies that messages are made up of
       characters in the US-ASCII range of 1 through 127.  There are
       other documents, specifically the MIME document series ([RFC2045],
       [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]), that
       extend this specification to allow for values outside of that
       range.  Discussion of those mechanisms is not within the scope of
       this specification.
 
    Messages are divided into lines of characters.  A line is a series of
    characters that is delimited with the two characters carriage-return
    and line-feed; that is, the carriage return (CR) character (ASCII
    value 13) followed immediately by the line feed (LF) character (ASCII
    value 10).  (The carriage return/line feed pair is usually written in
    this document as "CRLF".)
 
 
 
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    A message consists of header fields (collectively called "the header
    section of the message") followed, optionally, by a body.  The header
    section is a sequence of lines of characters with special syntax as
    defined in this specification.  The body is simply a sequence of
    characters that follows the header section and is separated from the
    header section by an empty line (i.e., a line with nothing preceding
    the CRLF).
 
       Note: Common parlance and earlier versions of this specification
       use the term "header" to either refer to the entire header section
       or to refer to an individual header field.  To avoid ambiguity,
       this document does not use the terms "header" or "headers" in
       isolation, but instead always uses "header field" to refer to the
       individual field and "header section" to refer to the entire
       collection.
 
 2.1.1.  Line Length Limits
 
    There are two limits that this specification places on the number of
    characters in a line.  Each line of characters MUST be no more than
    998 characters, and SHOULD be no more than 78 characters, excluding
    the CRLF.
 
    The 998 character limit is due to limitations in many implementations
    that send, receive, or store IMF messages which simply cannot handle
    more than 998 characters on a line.  Receiving implementations would
    do well to handle an arbitrarily large number of characters in a line
    for robustness sake.  However, there are so many implementations that
    (in compliance with the transport requirements of [RFC5321]) do not
    accept messages containing more than 1000 characters including the CR
    and LF per line, it is important for implementations not to create
    such messages.
 
    The more conservative 78 character recommendation is to accommodate
    the many implementations of user interfaces that display these
    messages which may truncate, or disastrously wrap, the display of
    more than 78 characters per line, in spite of the fact that such
    implementations are non-conformant to the intent of this
    specification (and that of [RFC5321] if they actually cause
    information to be lost).  Again, even though this limitation is put
    on messages, it is incumbent upon implementations that display
    messages to handle an arbitrarily large number of characters in a
    line (certainly at least up to the 998 character limit) for the sake
    of robustness.
 
 
 
 
 
 
 
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 2.2.  Header Fields
 
    Header fields are lines beginning with a field name, followed by a
    colon (":"), followed by a field body, and terminated by CRLF.  A
    field name MUST be composed of printable US-ASCII characters (i.e.,
    characters that have values between 33 and 126, inclusive), except
    colon.  A field body may be composed of printable US-ASCII characters
    as well as the space (SP, ASCII value 32) and horizontal tab (HTAB,
    ASCII value 9) characters (together known as the white space
    characters, WSP).  A field body MUST NOT include CR and LF except
    when used in "folding" and "unfolding", as described in section
    2.2.3.  All field bodies MUST conform to the syntax described in
    sections 3 and 4 of this specification.
 
 2.2.1.  Unstructured Header Field Bodies
 
    Some field bodies in this specification are defined simply as
    "unstructured" (which is specified in section 3.2.5 as any printable
    US-ASCII characters plus white space characters) with no further
    restrictions.  These are referred to as unstructured field bodies.
    Semantically, unstructured field bodies are simply to be treated as a
    single line of characters with no further processing (except for
    "folding" and "unfolding" as described in section 2.2.3).
 
 2.2.2.  Structured Header Field Bodies
 
    Some field bodies in this specification have a syntax that is more
    restrictive than the unstructured field bodies described above.
    These are referred to as "structured" field bodies.  Structured field
    bodies are sequences of specific lexical tokens as described in
    sections 3 and 4 of this specification.  Many of these tokens are
    allowed (according to their syntax) to be introduced or end with
    comments (as described in section 3.2.2) as well as the white space
    characters, and those white space characters are subject to "folding"
    and "unfolding" as described in section 2.2.3.  Semantic analysis of
    structured field bodies is given along with their syntax.
 
 2.2.3.  Long Header Fields
 
    Each header field is logically a single line of characters comprising
    the field name, the colon, and the field body.  For convenience
    however, and to deal with the 998/78 character limitations per line,
    the field body portion of a header field can be split into a
    multiple-line representation; this is called "folding".  The general
    rule is that wherever this specification allows for folding white
    space (not simply WSP characters), a CRLF may be inserted before any
    WSP.
 
 
 
 
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    For example, the header field:
 
    Subject: This is a test
 
    can be represented as:
 
    Subject: This
     is a test
 
       Note: Though structured field bodies are defined in such a way
       that folding can take place between many of the lexical tokens
       (and even within some of the lexical tokens), folding SHOULD be
       limited to placing the CRLF at higher-level syntactic breaks.  For
       instance, if a field body is defined as comma-separated values, it
       is recommended that folding occur after the comma separating the
       structured items in preference to other places where the field
       could be folded, even if it is allowed elsewhere.
 
    The process of moving from this folded multiple-line representation
    of a header field to its single line representation is called
    "unfolding".  Unfolding is accomplished by simply removing any CRLF
    that is immediately followed by WSP.  Each header field should be
    treated in its unfolded form for further syntactic and semantic
    evaluation.  An unfolded header field has no length restriction and
    therefore may be indeterminately long.
 
 2.3.  Body
 
    The body of a message is simply lines of US-ASCII characters.  The
    only two limitations on the body are as follows:
 
    o  CR and LF MUST only occur together as CRLF; they MUST NOT appear
       independently in the body.
    o  Lines of characters in the body MUST be limited to 998 characters,
       and SHOULD be limited to 78 characters, excluding the CRLF.
 
       Note: As was stated earlier, there are other documents,
       specifically the MIME documents ([RFC2045], [RFC2046], [RFC2049],
       [RFC4288], [RFC4289]), that extend (and limit) this specification
       to allow for different sorts of message bodies.  Again, these
       mechanisms are beyond the scope of this document.
 
 
 
 
 
 
 
 
 
 
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 3.  Syntax
 
 3.1.  Introduction
 
    The syntax as given in this section defines the legal syntax of
    Internet messages.  Messages that are conformant to this
    specification MUST conform to the syntax in this section.  If there
    are options in this section where one option SHOULD be generated,
    that is indicated either in the prose or in a comment next to the
    syntax.
 
    For the defined expressions, a short description of the syntax and
    use is given, followed by the syntax in ABNF, followed by a semantic
    analysis.  The following primitive tokens that are used but otherwise
    unspecified are taken from the "Core Rules" of [RFC5234], Appendix
    B.1: CR, LF, CRLF, HTAB, SP, WSP, DQUOTE, DIGIT, ALPHA, and VCHAR.
 
    In some of the definitions, there will be non-terminals whose names
    start with "obs-".  These "obs-" elements refer to tokens defined in
    the obsolete syntax in section 4.  In all cases, these productions
    are to be ignored for the purposes of generating legal Internet
    messages and MUST NOT be used as part of such a message.  However,
    when interpreting messages, these tokens MUST be honored as part of
    the legal syntax.  In this sense, section 3 defines a grammar for the
    generation of messages, with "obs-" elements that are to be ignored,
    while section 4 adds grammar for the interpretation of messages.
 
 3.2.  Lexical Tokens
 
    The following rules are used to define an underlying lexical
    analyzer, which feeds tokens to the higher-level parsers.  This
    section defines the tokens used in structured header field bodies.
 
       Note: Readers of this specification need to pay special attention
       to how these lexical tokens are used in both the lower-level and
       higher-level syntax later in the document.  Particularly, the
       white space tokens and the comment tokens defined in section 3.2.2
       get used in the lower-level tokens defined here, and those lower-
       level tokens are in turn used as parts of the higher-level tokens
       defined later.  Therefore, white space and comments may be allowed
       in the higher-level tokens even though they may not explicitly
       appear in a particular definition.
 
 3.2.1.  Quoted characters
 
    Some characters are reserved for special interpretation, such as
    delimiting lexical tokens.  To permit use of these characters as
    uninterpreted data, a quoting mechanism is provided.
 
 
 
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    quoted-pair     =   ("\" (VCHAR / WSP)) / obs-qp
 
    Where any quoted-pair appears, it is to be interpreted as the
    character alone.  That is to say, the "\" character that appears as
    part of a quoted-pair is semantically "invisible".
 
       Note: The "\" character may appear in a message where it is not
       part of a quoted-pair.  A "\" character that does not appear in a
       quoted-pair is not semantically invisible.  The only places in
       this specification where quoted-pair currently appears are
       ccontent, qcontent, and in obs-dtext in section 4.
 
 3.2.2.  Folding White Space and Comments
 
    White space characters, including white space used in folding
    (described in section 2.2.3), may appear between many elements in
    header field bodies.  Also, strings of characters that are treated as
    comments may be included in structured field bodies as characters
    enclosed in parentheses.  The following defines the folding white
    space (FWS) and comment constructs.
 
    Strings of characters enclosed in parentheses are considered comments
    so long as they do not appear within a "quoted-string", as defined in
    section 3.2.4.  Comments may nest.
 
    There are several places in this specification where comments and FWS
    may be freely inserted.  To accommodate that syntax, an additional
    token for "CFWS" is defined for places where comments and/or FWS can
    occur.  However, where CFWS occurs in this specification, it MUST NOT
    be inserted in such a way that any line of a folded header field is
    made up entirely of WSP characters and nothing else.
 
    FWS             =   ([*WSP CRLF] 1*WSP) /  obs-FWS
                                           ; Folding white space
 
    ctext           =   %d33-39 /          ; Printable US-ASCII
                        %d42-91 /          ;  characters not including
                        %d93-126 /         ;  "(", ")", or "\"
                        obs-ctext
 
    ccontent        =   ctext / quoted-pair / comment
 
    comment         =   "(" *([FWS] ccontent) [FWS] ")"
 
    CFWS            =   (1*([FWS] comment) [FWS]) / FWS
 
 
 
 
 
 
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    Throughout this specification, where FWS (the folding white space
    token) appears, it indicates a place where folding, as discussed in
    section 2.2.3, may take place.  Wherever folding appears in a message
    (that is, a header field body containing a CRLF followed by any WSP),
    unfolding (removal of the CRLF) is performed before any further
    semantic analysis is performed on that header field according to this
    specification.  That is to say, any CRLF that appears in FWS is
    semantically "invisible".
 
    A comment is normally used in a structured field body to provide some
    human-readable informational text.  Since a comment is allowed to
    contain FWS, folding is permitted within the comment.  Also note that
    since quoted-pair is allowed in a comment, the parentheses and
    backslash characters may appear in a comment, so long as they appear
    as a quoted-pair.  Semantically, the enclosing parentheses are not
    part of the comment; the comment is what is contained between the two
    parentheses.  As stated earlier, the "\" in any quoted-pair and the
    CRLF in any FWS that appears within the comment are semantically
    "invisible" and therefore not part of the comment either.
 
    Runs of FWS, comment, or CFWS that occur between lexical tokens in a
    structured header field are semantically interpreted as a single
    space character.
 
 3.2.3.  Atom
 
    Several productions in structured header field bodies are simply
    strings of certain basic characters.  Such productions are called
    atoms.
 
    Some of the structured header field bodies also allow the period
    character (".", ASCII value 46) within runs of atext.  An additional
    "dot-atom" token is defined for those purposes.
 
       Note: The "specials" token does not appear anywhere else in this
       specification.  It is simply the visible (i.e., non-control, non-
       white space) characters that do not appear in atext.  It is
       provided only because it is useful for implementers who use tools
       that lexically analyze messages.  Each of the characters in
       specials can be used to indicate a tokenization point in lexical
       analysis.
 
 
 
 
 
 
 
 
 
 
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    atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
                        "!" / "#" /        ;  characters not including
                        "$" / "%" /        ;  specials.  Used for atoms.
                        "&" / "'" /
                        "*" / "+" /
                        "-" / "/" /
                        "=" / "?" /
                        "^" / "_" /
                        "`" / "{" /
                        "|" / "}" /
                        "~"
 
    atom            =   [CFWS] 1*atext [CFWS]
 
    dot-atom-text   =   1*atext *("." 1*atext)
 
    dot-atom        =   [CFWS] dot-atom-text [CFWS]
 
    specials        =   "(" / ")" /        ; Special characters that do
                        "<" / ">" /        ;  not appear in atext
                        "[" / "]" /
                        ":" / ";" /
                        "@" / "\" /
                        "," / "." /
                        DQUOTE
 
    Both atom and dot-atom are interpreted as a single unit, comprising
    the string of characters that make it up.  Semantically, the optional
    comments and FWS surrounding the rest of the characters are not part
    of the atom; the atom is only the run of atext characters in an atom,
    or the atext and "." characters in a dot-atom.
 
 3.2.4.  Quoted Strings
 
    Strings of characters that include characters other than those
    allowed in atoms can be represented in a quoted string format, where
    the characters are surrounded by quote (DQUOTE, ASCII value 34)
    characters.
 
 
 
 
 
 
 
 
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    qtext           =   %d33 /             ; Printable US-ASCII
                        %d35-91 /          ;  characters not including
                        %d93-126 /         ;  "\" or the quote character
                        obs-qtext
 
    qcontent        =   qtext / quoted-pair
 
    quoted-string   =   [CFWS]
                        DQUOTE *([FWS] qcontent) [FWS] DQUOTE
                        [CFWS]
 
    A quoted-string is treated as a unit.  That is, quoted-string is
    identical to atom, semantically.  Since a quoted-string is allowed to
    contain FWS, folding is permitted.  Also note that since quoted-pair
    is allowed in a quoted-string, the quote and backslash characters may
    appear in a quoted-string so long as they appear as a quoted-pair.
 
    Semantically, neither the optional CFWS outside of the quote
    characters nor the quote characters themselves are part of the
    quoted-string; the quoted-string is what is contained between the two
    quote characters.  As stated earlier, the "\" in any quoted-pair and
    the CRLF in any FWS/CFWS that appears within the quoted-string are
    semantically "invisible" and therefore not part of the quoted-string
    either.
 
 3.2.5.  Miscellaneous Tokens
 
    Three additional tokens are defined: word and phrase for combinations
    of atoms and/or quoted-strings, and unstructured for use in
    unstructured header fields and in some places within structured
    header fields.
 
    word            =   atom / quoted-string
 
    phrase          =   1*word / obs-phrase
 
    unstructured    =   (*([FWS] VCHAR) *WSP) / obs-unstruct
 
 3.3.  Date and Time Specification
 
    Date and time values occur in several header fields.  This section
    specifies the syntax for a full date and time specification.  Though
    folding white space is permitted throughout the date-time
    specification, it is RECOMMENDED that a single space be used in each
    place that FWS appears (whether it is required or optional); some
    older implementations will not interpret longer sequences of folding
    white space correctly.
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    date-time       =   [ day-of-week "," ] date time [CFWS]
 
    day-of-week     =   ([FWS] day-name) / obs-day-of-week
 
    day-name        =   "Mon" / "Tue" / "Wed" / "Thu" /
                        "Fri" / "Sat" / "Sun"
 
    date            =   day month year
 
    day             =   ([FWS] 1*2DIGIT FWS) / obs-day
 
    month           =   "Jan" / "Feb" / "Mar" / "Apr" /
                        "May" / "Jun" / "Jul" / "Aug" /
                        "Sep" / "Oct" / "Nov" / "Dec"
 
    year            =   (FWS 4*DIGIT FWS) / obs-year
 
    time            =   time-of-day zone
 
    time-of-day     =   hour ":" minute [ ":" second ]
 
    hour            =   2DIGIT / obs-hour
 
    minute          =   2DIGIT / obs-minute
 
    second          =   2DIGIT / obs-second
 
    zone            =   (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
 
    The day is the numeric day of the month.  The year is any numeric
    year 1900 or later.
 
    The time-of-day specifies the number of hours, minutes, and
    optionally seconds since midnight of the date indicated.
 
    The date and time-of-day SHOULD express local time.
 
    The zone specifies the offset from Coordinated Universal Time (UTC,
    formerly referred to as "Greenwich Mean Time") that the date and
    time-of-day represent.  The "+" or "-" indicates whether the time-of-
    day is ahead of (i.e., east of) or behind (i.e., west of) Universal
    Time.  The first two digits indicate the number of hours difference
    from Universal Time, and the last two digits indicate the number of
    additional minutes difference from Universal Time.  (Hence, +hhmm
    means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
    minutes).  The form "+0000" SHOULD be used to indicate a time zone at
    Universal Time.  Though "-0000" also indicates Universal Time, it is
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    used to indicate that the time was generated on a system that may be
    in a local time zone other than Universal Time and that the date-time
    contains no information about the local time zone.
 
    A date-time specification MUST be semantically valid.  That is, the
    day-of-week (if included) MUST be the day implied by the date, the
    numeric day-of-month MUST be between 1 and the number of days allowed
    for the specified month (in the specified year), the time-of-day MUST
    be in the range 00:00:00 through 23:59:60 (the number of seconds
    allowing for a leap second; see [RFC1305]), and the last two digits
    of the zone MUST be within the range 00 through 59.
 
 3.4.  Address Specification
 
    Addresses occur in several message header fields to indicate senders
    and recipients of messages.  An address may either be an individual
    mailbox, or a group of mailboxes.
 
    address         =   mailbox / group
 
    mailbox         =   name-addr / addr-spec
 
    name-addr       =   [display-name] angle-addr
 
    angle-addr      =   [CFWS] "<" addr-spec ">" [CFWS] /
                        obs-angle-addr
 
    group           =   display-name ":" [group-list] ";" [CFWS]
 
    display-name    =   phrase
 
    mailbox-list    =   (mailbox *("," mailbox)) / obs-mbox-list
 
    address-list    =   (address *("," address)) / obs-addr-list
 
    group-list      =   mailbox-list / CFWS / obs-group-list
 
    A mailbox receives mail.  It is a conceptual entity that does not
    necessarily pertain to file storage.  For example, some sites may
    choose to print mail on a printer and deliver the output to the
    addressee's desk.
 
    Normally, a mailbox is composed of two parts: (1) an optional display
    name that indicates the name of the recipient (which can be a person
    or a system) that could be displayed to the user of a mail
    application, and (2) an addr-spec address enclosed in angle brackets
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    ("<" and ">").  There is an alternate simple form of a mailbox where
    the addr-spec address appears alone, without the recipient's name or
    the angle brackets.  The Internet addr-spec address is described in
    section 3.4.1.
 
       Note: Some legacy implementations used the simple form where the
       addr-spec appears without the angle brackets, but included the
       name of the recipient in parentheses as a comment following the
       addr-spec.  Since the meaning of the information in a comment is
       unspecified, implementations SHOULD use the full name-addr form of
       the mailbox, instead of the legacy form, to specify the display
       name associated with a mailbox.  Also, because some legacy
       implementations interpret the comment, comments generally SHOULD
       NOT be used in address fields to avoid confusing such
       implementations.
 
    When it is desirable to treat several mailboxes as a single unit
    (i.e., in a distribution list), the group construct can be used.  The
    group construct allows the sender to indicate a named group of
    recipients.  This is done by giving a display name for the group,
    followed by a colon, followed by a comma-separated list of any number
    of mailboxes (including zero and one), and ending with a semicolon.
    Because the list of mailboxes can be empty, using the group construct
    is also a simple way to communicate to recipients that the message
    was sent to one or more named sets of recipients, without actually
    providing the individual mailbox address for any of those recipients.
 
 3.4.1.  Addr-Spec Specification
 
    An addr-spec is a specific Internet identifier that contains a
    locally interpreted string followed by the at-sign character ("@",
    ASCII value 64) followed by an Internet domain.  The locally
    interpreted string is either a quoted-string or a dot-atom.  If the
    string can be represented as a dot-atom (that is, it contains no
    characters other than atext characters or "." surrounded by atext
    characters), then the dot-atom form SHOULD be used and the quoted-
    string form SHOULD NOT be used.  Comments and folding white space
    SHOULD NOT be used around the "@" in the addr-spec.
 
       Note: A liberal syntax for the domain portion of addr-spec is
       given here.  However, the domain portion contains addressing
       information specified by and used in other protocols (e.g.,
       [RFC1034], [RFC1035], [RFC1123], [RFC5321]).  It is therefore
       incumbent upon implementations to conform to the syntax of
       addresses for the context in which they are used.
 
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    addr-spec       =   local-part "@" domain
 
    local-part      =   dot-atom / quoted-string / obs-local-part
 
    domain          =   dot-atom / domain-literal / obs-domain
 
    domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
 
    dtext           =   %d33-90 /          ; Printable US-ASCII
                        %d94-126 /         ;  characters not including
                        obs-dtext          ;  "[", "]", or "\"
 
    The domain portion identifies the point to which the mail is
    delivered.  In the dot-atom form, this is interpreted as an Internet
    domain name (either a host name or a mail exchanger name) as
    described in [RFC1034], [RFC1035], and [RFC1123].  In the domain-
    literal form, the domain is interpreted as the literal Internet
    address of the particular host.  In both cases, how addressing is
    used and how messages are transported to a particular host is covered
    in separate documents, such as [RFC5321].  These mechanisms are
    outside of the scope of this document.
 
    The local-part portion is a domain-dependent string.  In addresses,
    it is simply interpreted on the particular host as a name of a
    particular mailbox.
 
 3.5.  Overall Message Syntax
 
    A message consists of header fields, optionally followed by a message
    body.  Lines in a message MUST be a maximum of 998 characters
    excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
    characters excluding the CRLF.  (See section 2.1.1 for explanation.)
    In a message body, though all of the characters listed in the text
    rule MAY be used, the use of US-ASCII control characters (values 1
    through 8, 11, 12, and 14 through 31) is discouraged since their
    interpretation by receivers for display is not guaranteed.
 
    message         =   (fields / obs-fields)
                        [CRLF body]
 
    body            =   (*(*998text CRLF) *998text) / obs-body
 
    text            =   %d1-9 /            ; Characters excluding CR
                        %d11 /             ;  and LF
                        %d12 /
                        %d14-127
 
 
 
 
 
 Resnick                     Standards Track                    [Page 18]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    The header fields carry most of the semantic information and are
    defined in section 3.6.  The body is simply a series of lines of text
    that are uninterpreted for the purposes of this specification.
 
 3.6.  Field Definitions
 
    The header fields of a message are defined here.  All header fields
    have the same general syntactic structure: a field name, followed by
    a colon, followed by the field body.  The specific syntax for each
    header field is defined in the subsequent sections.
 
       Note: In the ABNF syntax for each field in subsequent sections,
       each field name is followed by the required colon.  However, for
       brevity, sometimes the colon is not referred to in the textual
       description of the syntax.  It is, nonetheless, required.
 
    It is important to note that the header fields are not guaranteed to
    be in a particular order.  They may appear in any order, and they
    have been known to be reordered occasionally when transported over
    the Internet.  However, for the purposes of this specification,
    header fields SHOULD NOT be reordered when a message is transported
    or transformed.  More importantly, the trace header fields and resent
    header fields MUST NOT be reordered, and SHOULD be kept in blocks
    prepended to the message.  See sections 3.6.6 and 3.6.7 for more
    information.
 
    The only required header fields are the origination date field and
    the originator address field(s).  All other header fields are
    syntactically optional.  More information is contained in the table
    following this definition.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 19]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    fields          =   *(trace
                          *optional-field /
                          *(resent-date /
                           resent-from /
                           resent-sender /
                           resent-to /
                           resent-cc /
                           resent-bcc /
                           resent-msg-id))
                        *(orig-date /
                        from /
                        sender /
                        reply-to /
                        to /
                        cc /
                        bcc /
                        message-id /
                        in-reply-to /
                        references /
                        subject /
                        comments /
                        keywords /
                        optional-field)
 
    The following table indicates limits on the number of times each
    field may occur in the header section of a message as well as any
    special limitations on the use of those fields.  An asterisk ("*")
    next to a value in the minimum or maximum column indicates that a
    special restriction appears in the Notes column.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    +----------------+--------+------------+----------------------------+
    | Field          | Min    | Max number | Notes                      |
    |                | number |            |                            |
    +----------------+--------+------------+----------------------------+
    | trace          | 0      | unlimited  | Block prepended - see      |
    |                |        |            | 3.6.7                      |
    | resent-date    | 0*     | unlimited* | One per block, required if |
    |                |        |            | other resent fields are    |
    |                |        |            | present - see 3.6.6        |
    | resent-from    | 0      | unlimited* | One per block - see 3.6.6  |
    | resent-sender  | 0*     | unlimited* | One per block, MUST occur  |
    |                |        |            | with multi-address         |
    |                |        |            | resent-from - see 3.6.6    |
    | resent-to      | 0      | unlimited* | One per block - see 3.6.6  |
    | resent-cc      | 0      | unlimited* | One per block - see 3.6.6  |
    | resent-bcc     | 0      | unlimited* | One per block - see 3.6.6  |
    | resent-msg-id  | 0      | unlimited* | One per block - see 3.6.6  |
    | orig-date      | 1      | 1          |                            |
    | from           | 1      | 1          | See sender and 3.6.2       |
    | sender         | 0*     | 1          | MUST occur with            |
    |                |        |            | multi-address from - see   |
    |                |        |            | 3.6.2                      |
    | reply-to       | 0      | 1          |                            |
    | to             | 0      | 1          |                            |
    | cc             | 0      | 1          |                            |
    | bcc            | 0      | 1          |                            |
    | message-id     | 0*     | 1          | SHOULD be present - see    |
    |                |        |            | 3.6.4                      |
    | in-reply-to    | 0*     | 1          | SHOULD occur in some       |
    |                |        |            | replies - see 3.6.4        |
    | references     | 0*     | 1          | SHOULD occur in some       |
    |                |        |            | replies - see 3.6.4        |
    | subject        | 0      | 1          |                            |
    | comments       | 0      | unlimited  |                            |
    | keywords       | 0      | unlimited  |                            |
    | optional-field | 0      | unlimited  |                            |
    +----------------+--------+------------+----------------------------+
 
    The exact interpretation of each field is described in subsequent
    sections.
 
 
 
 
 
 
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
 3.6.1.  The Origination Date Field
 
    The origination date field consists of the field name "Date" followed
    by a date-time specification.
 
    orig-date       =   "Date:" date-time CRLF
 
    The origination date specifies the date and time at which the creator
    of the message indicated that the message was complete and ready to
    enter the mail delivery system.  For instance, this might be the time
    that a user pushes the "send" or "submit" button in an application
    program.  In any case, it is specifically not intended to convey the
    time that the message is actually transported, but rather the time at
    which the human or other creator of the message has put the message
    into its final form, ready for transport.  (For example, a portable
    computer user who is not connected to a network might queue a message
    for delivery.  The origination date is intended to contain the date
    and time that the user queued the message, not the time when the user
    connected to the network to send the message.)
 
 3.6.2.  Originator Fields
 
    The originator fields of a message consist of the from field, the
    sender field (when applicable), and optionally the reply-to field.
    The from field consists of the field name "From" and a comma-
    separated list of one or more mailbox specifications.  If the from
    field contains more than one mailbox specification in the mailbox-
    list, then the sender field, containing the field name "Sender" and a
    single mailbox specification, MUST appear in the message.  In either
    case, an optional reply-to field MAY also be included, which contains
    the field name "Reply-To" and a comma-separated list of one or more
    addresses.
 
    from            =   "From:" mailbox-list CRLF
 
    sender          =   "Sender:" mailbox CRLF
 
    reply-to        =   "Reply-To:" address-list CRLF
 
    The originator fields indicate the mailbox(es) of the source of the
    message.  The "From:" field specifies the author(s) of the message,
    that is, the mailbox(es) of the person(s) or system(s) responsible
    for the writing of the message.  The "Sender:" field specifies the
    mailbox of the agent responsible for the actual transmission of the
    message.  For example, if a secretary were to send a message for
    another person, the mailbox of the secretary would appear in the
    "Sender:" field and the mailbox of the actual author would appear in
    the "From:" field.  If the originator of the message can be indicated
 
 
 
 Resnick                     Standards Track                    [Page 22]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    by a single mailbox and the author and transmitter are identical, the
    "Sender:" field SHOULD NOT be used.  Otherwise, both fields SHOULD
    appear.
 
       Note: The transmitter information is always present.  The absence
       of the "Sender:" field is sometimes mistakenly taken to mean that
       the agent responsible for transmission of the message has not been
       specified.  This absence merely means that the transmitter is
       identical to the author and is therefore not redundantly placed
       into the "Sender:" field.
 
    The originator fields also provide the information required when
    replying to a message.  When the "Reply-To:" field is present, it
    indicates the address(es) to which the author of the message suggests
    that replies be sent.  In the absence of the "Reply-To:" field,
    replies SHOULD by default be sent to the mailbox(es) specified in the
    "From:" field unless otherwise specified by the person composing the
    reply.
 
    In all cases, the "From:" field SHOULD NOT contain any mailbox that
    does not belong to the author(s) of the message.  See also section
    3.6.3 for more information on forming the destination addresses for a
    reply.
 
 3.6.3.  Destination Address Fields
 
    The destination fields of a message consist of three possible fields,
    each of the same form: the field name, which is either "To", "Cc", or
    "Bcc", followed by a comma-separated list of one or more addresses
    (either mailbox or group syntax).
 
    to              =   "To:" address-list CRLF
 
    cc              =   "Cc:" address-list CRLF
 
    bcc             =   "Bcc:" [address-list / CFWS] CRLF
 
    The destination fields specify the recipients of the message.  Each
    destination field may have one or more addresses, and the addresses
    indicate the intended recipients of the message.  The only difference
    between the three fields is how each is used.
 
    The "To:" field contains the address(es) of the primary recipient(s)
    of the message.
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 23]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
    making a copy on a typewriter using carbon paper) contains the
    addresses of others who are to receive the message, though the
    content of the message may not be directed at them.
 
    The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
    addresses of recipients of the message whose addresses are not to be
    revealed to other recipients of the message.  There are three ways in
    which the "Bcc:" field is used.  In the first case, when a message
    containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
    removed even though all of the recipients (including those specified
    in the "Bcc:" field) are sent a copy of the message.  In the second
    case, recipients specified in the "To:" and "Cc:" lines each are sent
    a copy of the message with the "Bcc:" line removed as above, but the
    recipients on the "Bcc:" line get a separate copy of the message
    containing a "Bcc:" line.  (When there are multiple recipient
    addresses in the "Bcc:" field, some implementations actually send a
    separate copy of the message to each recipient with a "Bcc:"
    containing only the address of that particular recipient.)  Finally,
    since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
    sent without any addresses indicating to the recipients that blind
    copies were sent to someone.  Which method to use with "Bcc:" fields
    is implementation dependent, but refer to the "Security
    Considerations" section of this document for a discussion of each.
 
    When a message is a reply to another message, the mailboxes of the
    authors of the original message (the mailboxes in the "From:" field)
    or mailboxes specified in the "Reply-To:" field (if it exists) MAY
    appear in the "To:" field of the reply since these would normally be
    the primary recipients of the reply.  If a reply is sent to a message
    that has destination fields, it is often desirable to send a copy of
    the reply to all of the recipients of the message, in addition to the
    author.  When such a reply is formed, addresses in the "To:" and
    "Cc:" fields of the original message MAY appear in the "Cc:" field of
    the reply, since these are normally secondary recipients of the
    reply.  If a "Bcc:" field is present in the original message,
    addresses in that field MAY appear in the "Bcc:" field of the reply,
    but they SHOULD NOT appear in the "To:" or "Cc:" fields.
 
       Note: Some mail applications have automatic reply commands that
       include the destination addresses of the original message in the
       destination addresses of the reply.  How those reply commands
       behave is implementation dependent and is beyond the scope of this
       document.  In particular, whether or not to include the original
       destination addresses when the original message had a "Reply-To:"
       field is not addressed here.
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
 3.6.4.  Identification Fields
 
    Though listed as optional in the table in section 3.6, every message
    SHOULD have a "Message-ID:" field.  Furthermore, reply messages
    SHOULD have "In-Reply-To:" and "References:" fields as appropriate
    and as described below.
 
    The "Message-ID:" field contains a single unique message identifier.
    The "References:" and "In-Reply-To:" fields each contain one or more
    unique message identifiers, optionally separated by CFWS.
 
    The message identifier (msg-id) syntax is a limited version of the
    addr-spec construct enclosed in the angle bracket characters, "<" and
    ">".  Unlike addr-spec, this syntax only permits the dot-atom-text
    form on the left-hand side of the "@" and does not have internal CFWS
    anywhere in the message identifier.
 
       Note: As with addr-spec, a liberal syntax is given for the right-
       hand side of the "@" in a msg-id.  However, later in this section,
       the use of a domain for the right-hand side of the "@" is
       RECOMMENDED.  Again, the syntax of domain constructs is specified
       by and used in other protocols (e.g., [RFC1034], [RFC1035],
       [RFC1123], [RFC5321]).  It is therefore incumbent upon
       implementations to conform to the syntax of addresses for the
       context in which they are used.
 
    message-id      =   "Message-ID:" msg-id CRLF
 
    in-reply-to     =   "In-Reply-To:" 1*msg-id CRLF
 
    references      =   "References:" 1*msg-id CRLF
 
    msg-id          =   [CFWS] "<" id-left "@" id-right ">" [CFWS]
 
    id-left         =   dot-atom-text / obs-id-left
 
    id-right        =   dot-atom-text / no-fold-literal / obs-id-right
 
    no-fold-literal =   "[" *dtext "]"
 
    The "Message-ID:" field provides a unique message identifier that
    refers to a particular version of a particular message.  The
    uniqueness of the message identifier is guaranteed by the host that
    generates it (see below).  This message identifier is intended to be
    machine readable and not necessarily meaningful to humans.  A message
    identifier pertains to exactly one version of a particular message;
    subsequent revisions to the message each receive new message
    identifiers.
 
 
 
 Resnick                     Standards Track                    [Page 25]
 
 RFC 5322                Internet Message Format             October 2008
 
 
       Note: There are many instances when messages are "changed", but
       those changes do not constitute a new instantiation of that
       message, and therefore the message would not get a new message
       identifier.  For example, when messages are introduced into the
       transport system, they are often prepended with additional header
       fields such as trace fields (described in section 3.6.7) and
       resent fields (described in section 3.6.6).  The addition of such
       header fields does not change the identity of the message and
       therefore the original "Message-ID:" field is retained.  In all
       cases, it is the meaning that the sender of the message wishes to
       convey (i.e., whether this is the same message or a different
       message) that determines whether or not the "Message-ID:" field
       changes, not any particular syntactic difference that appears (or
       does not appear) in the message.
 
    The "In-Reply-To:" and "References:" fields are used when creating a
    reply to a message.  They hold the message identifier of the original
    message and the message identifiers of other messages (for example,
    in the case of a reply to a message that was itself a reply).  The
    "In-Reply-To:" field may be used to identify the message (or
    messages) to which the new message is a reply, while the
    "References:" field may be used to identify a "thread" of
    conversation.
 
    When creating a reply to a message, the "In-Reply-To:" and
    "References:" fields of the resultant message are constructed as
    follows:
 
    The "In-Reply-To:" field will contain the contents of the
    "Message-ID:" field of the message to which this one is a reply (the
    "parent message").  If there is more than one parent message, then
    the "In-Reply-To:" field will contain the contents of all of the
    parents' "Message-ID:" fields.  If there is no "Message-ID:" field in
    any of the parent messages, then the new message will have no "In-
    Reply-To:" field.
 
    The "References:" field will contain the contents of the parent's
    "References:" field (if any) followed by the contents of the parent's
    "Message-ID:" field (if any).  If the parent message does not contain
    a "References:" field but does have an "In-Reply-To:" field
    containing a single message identifier, then the "References:" field
    will contain the contents of the parent's "In-Reply-To:" field
    followed by the contents of the parent's "Message-ID:" field (if
    any).  If the parent has none of the "References:", "In-Reply-To:",
    or "Message-ID:" fields, then the new message will have no
    "References:" field.
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
       Note: Some implementations parse the "References:" field to
       display the "thread of the discussion".  These implementations
       assume that each new message is a reply to a single parent and
       hence that they can walk backwards through the "References:" field
       to find the parent of each message listed there.  Therefore,
       trying to form a "References:" field for a reply that has multiple
       parents is discouraged; how to do so is not defined in this
       document.
 
    The message identifier (msg-id) itself MUST be a globally unique
    identifier for a message.  The generator of the message identifier
    MUST guarantee that the msg-id is unique.  There are several
    algorithms that can be used to accomplish this.  Since the msg-id has
    a similar syntax to addr-spec (identical except that quoted strings,
    comments, and folding white space are not allowed), a good method is
    to put the domain name (or a domain literal IP address) of the host
    on which the message identifier was created on the right-hand side of
    the "@" (since domain names and IP addresses are normally unique),
    and put a combination of the current absolute date and time along
    with some other currently unique (perhaps sequential) identifier
    available on the system (for example, a process id number) on the
    left-hand side.  Though other algorithms will work, it is RECOMMENDED
    that the right-hand side contain some domain identifier (either of
    the host itself or otherwise) such that the generator of the message
    identifier can guarantee the uniqueness of the left-hand side within
    the scope of that domain.
 
    Semantically, the angle bracket characters are not part of the
    msg-id; the msg-id is what is contained between the two angle bracket
    characters.
 
 3.6.5.  Informational Fields
 
    The informational fields are all optional.  The "Subject:" and
    "Comments:" fields are unstructured fields as defined in section
    2.2.1, and therefore may contain text or folding white space.  The
    "Keywords:" field contains a comma-separated list of one or more
    words or quoted-strings.
 
    subject         =   "Subject:" unstructured CRLF
 
    comments        =   "Comments:" unstructured CRLF
 
    keywords        =   "Keywords:" phrase *("," phrase) CRLF
 
    These three fields are intended to have only human-readable content
    with information about the message.  The "Subject:" field is the most
    common and contains a short string identifying the topic of the
 
 
 
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    message.  When used in a reply, the field body MAY start with the
    string "Re: " (an abbreviation of the Latin "in re", meaning "in the
    matter of") followed by the contents of the "Subject:" field body of
    the original message.  If this is done, only one instance of the
    literal string "Re: " ought to be used since use of other strings or
    more than one instance can lead to undesirable consequences.  The
    "Comments:" field contains any additional comments on the text of the
    body of the message.  The "Keywords:" field contains a comma-
    separated list of important words and phrases that might be useful
    for the recipient.
 
 3.6.6.  Resent Fields
 
    Resent fields SHOULD be added to any message that is reintroduced by
    a user into the transport system.  A separate set of resent fields
    SHOULD be added each time this is done.  All of the resent fields
    corresponding to a particular resending of the message SHOULD be
    grouped together.  Each new set of resent fields is prepended to the
    message; that is, the most recent set of resent fields appears
    earlier in the message.  No other fields in the message are changed
    when resent fields are added.
 
    Each of the resent fields corresponds to a particular field elsewhere
    in the syntax.  For instance, the "Resent-Date:" field corresponds to
    the "Date:" field and the "Resent-To:" field corresponds to the "To:"
    field.  In each case, the syntax for the field body is identical to
    the syntax given previously for the corresponding field.
 
    When resent fields are used, the "Resent-From:" and "Resent-Date:"
    fields MUST be sent.  The "Resent-Message-ID:" field SHOULD be sent.
    "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
    identical to "Resent-From:".
 
    resent-date     =   "Resent-Date:" date-time CRLF
 
    resent-from     =   "Resent-From:" mailbox-list CRLF
 
    resent-sender   =   "Resent-Sender:" mailbox CRLF
 
    resent-to       =   "Resent-To:" address-list CRLF
 
    resent-cc       =   "Resent-Cc:" address-list CRLF
 
    resent-bcc      =   "Resent-Bcc:" [address-list / CFWS] CRLF
 
    resent-msg-id   =   "Resent-Message-ID:" msg-id CRLF
 
 
 
 
 
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    Resent fields are used to identify a message as having been
    reintroduced into the transport system by a user.  The purpose of
    using resent fields is to have the message appear to the final
    recipient as if it were sent directly by the original sender, with
    all of the original fields remaining the same.  Each set of resent
    fields correspond to a particular resending event.  That is, if a
    message is resent multiple times, each set of resent fields gives
    identifying information for each individual time.  Resent fields are
    strictly informational.  They MUST NOT be used in the normal
    processing of replies or other such automatic actions on messages.
 
       Note: Reintroducing a message into the transport system and using
       resent fields is a different operation from "forwarding".
       "Forwarding" has two meanings: One sense of forwarding is that a
       mail reading program can be told by a user to forward a copy of a
       message to another person, making the forwarded message the body
       of the new message.  A forwarded message in this sense does not
       appear to have come from the original sender, but is an entirely
       new message from the forwarder of the message.  Forwarding may
       also mean that a mail transport program gets a message and
       forwards it on to a different destination for final delivery.
       Resent header fields are not intended for use with either type of
       forwarding.
 
    The resent originator fields indicate the mailbox of the person(s) or
    system(s) that resent the message.  As with the regular originator
    fields, there are two forms: a simple "Resent-From:" form, which
    contains the mailbox of the individual doing the resending, and the
    more complex form, when one individual (identified in the "Resent-
    Sender:" field) resends a message on behalf of one or more others
    (identified in the "Resent-From:" field).
 
       Note: When replying to a resent message, replies behave just as
       they would with any other message, using the original "From:",
       "Reply-To:", "Message-ID:", and other fields.  The resent fields
       are only informational and MUST NOT be used in the normal
       processing of replies.
 
    The "Resent-Date:" indicates the date and time at which the resent
    message is dispatched by the resender of the message.  Like the
    "Date:" field, it is not the date and time that the message was
    actually transported.
 
    The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
    identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
    except that they indicate the recipients of the resent message, not
    the recipients of the original message.
 
 
 
 
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    The "Resent-Message-ID:" field provides a unique identifier for the
    resent message.
 
 3.6.7.  Trace Fields
 
    The trace fields are a group of header fields consisting of an
    optional "Return-Path:" field, and one or more "Received:" fields.
    The "Return-Path:" header field contains a pair of angle brackets
    that enclose an optional addr-spec.  The "Received:" field contains a
    (possibly empty) list of tokens followed by a semicolon and a date-
    time specification.  Each token must be a word, angle-addr, addr-
    spec, or a domain.  Further restrictions are applied to the syntax of
    the trace fields by specifications that provide for their use, such
    as [RFC5321].
 
    trace           =   [return]
                        1*received
 
    return          =   "Return-Path:" path CRLF
 
    path            =   angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
 
    received        =   "Received:" *received-token ";" date-time CRLF
 
    received-token  =   word / angle-addr / addr-spec / domain
 
    A full discussion of the Internet mail use of trace fields is
    contained in [RFC5321].  For the purposes of this specification, the
    trace fields are strictly informational, and any formal
    interpretation of them is outside of the scope of this document.
 
 3.6.8.  Optional Fields
 
    Fields may appear in messages that are otherwise unspecified in this
    document.  They MUST conform to the syntax of an optional-field.
    This is a field name, made up of the printable US-ASCII characters
    except SP and colon, followed by a colon, followed by any text that
    conforms to the unstructured syntax.
 
    The field names of any optional field MUST NOT be identical to any
    field name specified elsewhere in this document.
 
 
 
 
 
 
 
 
 
 
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    optional-field  =   field-name ":" unstructured CRLF
 
    field-name      =   1*ftext
 
    ftext           =   %d33-57 /          ; Printable US-ASCII
                        %d59-126           ;  characters not including
                                           ;  ":".
 
    For the purposes of this specification, any optional field is
    uninterpreted.
 
 4.  Obsolete Syntax
 
    Earlier versions of this specification allowed for different (usually
    more liberal) syntax than is allowed in this version.  Also, there
    have been syntactic elements used in messages on the Internet whose
    interpretations have never been documented.  Though these syntactic
    forms MUST NOT be generated according to the grammar in section 3,
    they MUST be accepted and parsed by a conformant receiver.  This
    section documents many of these syntactic elements.  Taking the
    grammar in section 3 and adding the definitions presented in this
    section will result in the grammar to use for the interpretation of
    messages.
 
       Note: This section identifies syntactic forms that any
       implementation MUST reasonably interpret.  However, there are
       certainly Internet messages that do not conform to even the
       additional syntax given in this section.  The fact that a
       particular form does not appear in any section of this document is
       not justification for computer programs to crash or for malformed
       data to be irretrievably lost by any implementation.  It is up to
       the implementation to deal with messages robustly.
 
    One important difference between the obsolete (interpreting) and the
    current (generating) syntax is that in structured header field bodies
    (i.e., between the colon and the CRLF of any structured header
    field), white space characters, including folding white space, and
    comments could be freely inserted between any syntactic tokens.  This
    allowed many complex forms that have proven difficult for some
    implementations to parse.
 
    Another key difference between the obsolete and the current syntax is
    that the rule in section 3.2.2 regarding lines composed entirely of
    white space in comments and folding white space does not apply.  See
    the discussion of folding white space in section 4.2 below.
 
    Finally, certain characters that were formerly allowed in messages
    appear in this section.  The NUL character (ASCII value 0) was once
 
 
 
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    allowed, but is no longer for compatibility reasons.  Similarly, US-
    ASCII control characters other than CR, LF, SP, and HTAB (ASCII
    values 1 through 8, 11, 12, 14 through 31, and 127) were allowed to
    appear in header field bodies.  CR and LF were allowed to appear in
    messages other than as CRLF; this use is also shown here.
 
    Other differences in syntax and semantics are noted in the following
    sections.
 
 4.1.  Miscellaneous Obsolete Tokens
 
    These syntactic elements are used elsewhere in the obsolete syntax or
    in the main syntax.  Bare CR, bare LF, and NUL are added to obs-qp,
    obs-body, and obs-unstruct.  US-ASCII control characters are added to
    obs-qp, obs-unstruct, obs-ctext, and obs-qtext.  The period character
    is added to obs-phrase.  The obs-phrase-list provides for a
    (potentially empty) comma-separated list of phrases that may include
    "null" elements.  That is, there could be two or more commas in such
    a list with nothing in between them, or commas at the beginning or
    end of the list.
 
       Note: The "period" (or "full stop") character (".") in obs-phrase
       is not a form that was allowed in earlier versions of this or any
       other specification.  Period (nor any other character from
       specials) was not allowed in phrase because it introduced a
       parsing difficulty distinguishing between phrases and portions of
       an addr-spec (see section 4.4).  It appears here because the
       period character is currently used in many messages in the
       display-name portion of addresses, especially for initials in
       names, and therefore must be interpreted properly.
 
    obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
                        %d11 /             ;  characters that do not
                        %d12 /             ;  include the carriage
                        %d14-31 /          ;  return, line feed, and
                        %d127              ;  white space characters
 
    obs-ctext       =   obs-NO-WS-CTL
 
    obs-qtext       =   obs-NO-WS-CTL
 
    obs-utext       =   %d0 / obs-NO-WS-CTL / VCHAR
 
    obs-qp          =   "\" (%d0 / obs-NO-WS-CTL / LF / CR)
 
    obs-body        =   *((*LF *CR *((%d0 / text) *LF *CR)) / CRLF)
 
    obs-unstruct    =   *((*LF *CR *(obs-utext *LF *CR)) / FWS)
 
 
 
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    obs-phrase      =   word *(word / "." / CFWS)
 
    obs-phrase-list =   [phrase / CFWS] *("," [phrase / CFWS])
 
    Bare CR and bare LF appear in messages with two different meanings.
    In many cases, bare CR or bare LF are used improperly instead of CRLF
    to indicate line separators.  In other cases, bare CR and bare LF are
    used simply as US-ASCII control characters with their traditional
    ASCII meanings.
 
 4.2.  Obsolete Folding White Space
 
    In the obsolete syntax, any amount of folding white space MAY be
    inserted where the obs-FWS rule is allowed.  This creates the
    possibility of having two consecutive "folds" in a line, and
    therefore the possibility that a line which makes up a folded header
    field could be composed entirely of white space.
 
    obs-FWS         =   1*WSP *(CRLF 1*WSP)
 
 4.3.  Obsolete Date and Time
 
    The syntax for the obsolete date format allows a 2 digit year in the
    date field and allows for a list of alphabetic time zone specifiers
    that were used in earlier versions of this specification.  It also
    permits comments and folding white space between many of the tokens.
 
    obs-day-of-week =   [CFWS] day-name [CFWS]
 
    obs-day         =   [CFWS] 1*2DIGIT [CFWS]
 
    obs-year        =   [CFWS] 2*DIGIT [CFWS]
 
    obs-hour        =   [CFWS] 2DIGIT [CFWS]
 
    obs-minute      =   [CFWS] 2DIGIT [CFWS]
 
    obs-second      =   [CFWS] 2DIGIT [CFWS]
 
    obs-zone        =   "UT" / "GMT" /     ; Universal Time
                                           ; North American UT
                                           ; offsets
                        "EST" / "EDT" /    ; Eastern:  - 5/ - 4
                        "CST" / "CDT" /    ; Central:  - 6/ - 5
                        "MST" / "MDT" /    ; Mountain: - 7/ - 6
                        "PST" / "PDT" /    ; Pacific:  - 8/ - 7
                                           ;
 
 
 
 
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                        %d65-73 /          ; Military zones - "A"
                        %d75-90 /          ; through "I" and "K"
                        %d97-105 /         ; through "Z", both
                        %d107-122          ; upper and lower case
 
    Where a two or three digit year occurs in a date, the year is to be
    interpreted as follows: If a two digit year is encountered whose
    value is between 00 and 49, the year is interpreted by adding 2000,
    ending up with a value between 2000 and 2049.  If a two digit year is
    encountered with a value between 50 and 99, or any three digit year
    is encountered, the year is interpreted by adding 1900.
 
    In the obsolete time zone, "UT" and "GMT" are indications of
    "Universal Time" and "Greenwich Mean Time", respectively, and are
    both semantically identical to "+0000".
 
    The remaining three character zones are the US time zones.  The first
    letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
    "Mountain", and "Pacific".  The second letter is either "S" for
    "Standard" time, or "D" for "Daylight Savings" (or summer) time.
    Their interpretations are as follows:
 
       EDT is semantically equivalent to -0400
       EST is semantically equivalent to -0500
       CDT is semantically equivalent to -0500
       CST is semantically equivalent to -0600
       MDT is semantically equivalent to -0600
       MST is semantically equivalent to -0700
       PDT is semantically equivalent to -0700
       PST is semantically equivalent to -0800
 
    The 1 character military time zones were defined in a non-standard
    way in [RFC0822] and are therefore unpredictable in their meaning.
    The original definitions of the military zones "A" through "I" are
    equivalent to "+0100" through "+0900", respectively; "K", "L", and
    "M" are equivalent to "+1000", "+1100", and "+1200", respectively;
    "N" through "Y" are equivalent to "-0100" through "-1200".
    respectively; and "Z" is equivalent to "+0000".  However, because of
    the error in [RFC0822], they SHOULD all be considered equivalent to
    "-0000" unless there is out-of-band information confirming their
    meaning.
 
    Other multi-character (usually between 3 and 5) alphabetic time zones
    have been used in Internet messages.  Any such time zone whose
    meaning is not known SHOULD be considered equivalent to "-0000"
    unless there is out-of-band information confirming their meaning.
 
 
 
 
 
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 4.4.  Obsolete Addressing
 
    There are four primary differences in addressing.  First, mailbox
    addresses were allowed to have a route portion before the addr-spec
    when enclosed in "<" and ">".  The route is simply a comma-separated
    list of domain names, each preceded by "@", and the list terminated
    by a colon.  Second, CFWS were allowed between the period-separated
    elements of local-part and domain (i.e., dot-atom was not used).  In
    addition, local-part is allowed to contain quoted-string in addition
    to just atom.  Third, mailbox-list and address-list were allowed to
    have "null" members.  That is, there could be two or more commas in
    such a list with nothing in between them, or commas at the beginning
    or end of the list.  Finally, US-ASCII control characters and quoted-
    pairs were allowed in domain literals and are added here.
 
    obs-angle-addr  =   [CFWS] "<" obs-route addr-spec ">" [CFWS]
 
    obs-route       =   obs-domain-list ":"
 
    obs-domain-list =   *(CFWS / ",") "@" domain
                        *("," [CFWS] ["@" domain])
 
    obs-mbox-list   =   *([CFWS] ",") mailbox *("," [mailbox / CFWS])
 
    obs-addr-list   =   *([CFWS] ",") address *("," [address / CFWS])
 
    obs-group-list  =   1*([CFWS] ",") [CFWS]
 
    obs-local-part  =   word *("." word)
 
    obs-domain      =   atom *("." atom)
 
    obs-dtext       =   obs-NO-WS-CTL / quoted-pair
 
    When interpreting addresses, the route portion SHOULD be ignored.
 
 4.5.  Obsolete Header Fields
 
    Syntactically, the primary difference in the obsolete field syntax is
    that it allows multiple occurrences of any of the fields and they may
    occur in any order.  Also, any amount of white space is allowed
    before the ":" at the end of the field name.
 
 
 
 
 
 
 
 
 
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    obs-fields      =   *(obs-return /
                        obs-received /
                        obs-orig-date /
                        obs-from /
                        obs-sender /
                        obs-reply-to /
                        obs-to /
                        obs-cc /
                        obs-bcc /
                        obs-message-id /
                        obs-in-reply-to /
                        obs-references /
                        obs-subject /
                        obs-comments /
                        obs-keywords /
                        obs-resent-date /
                        obs-resent-from /
                        obs-resent-send /
                        obs-resent-rply /
                        obs-resent-to /
                        obs-resent-cc /
                        obs-resent-bcc /
                        obs-resent-mid /
                        obs-optional)
 
    Except for destination address fields (described in section 4.5.3),
    the interpretation of multiple occurrences of fields is unspecified.
    Also, the interpretation of trace fields and resent fields that do
    not occur in blocks prepended to the message is unspecified as well.
    Unless otherwise noted in the following sections, interpretation of
    other fields is identical to the interpretation of their non-obsolete
    counterparts in section 3.
 
 4.5.1.  Obsolete Origination Date Field
 
    obs-orig-date   =   "Date" *WSP ":" date-time CRLF
 
 4.5.2.  Obsolete Originator Fields
 
    obs-from        =   "From" *WSP ":" mailbox-list CRLF
 
    obs-sender      =   "Sender" *WSP ":" mailbox CRLF
 
    obs-reply-to    =   "Reply-To" *WSP ":" address-list CRLF
 
 
 
 
 
 
 
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 4.5.3.  Obsolete Destination Address Fields
 
    obs-to          =   "To" *WSP ":" address-list CRLF
 
    obs-cc          =   "Cc" *WSP ":" address-list CRLF
 
    obs-bcc         =   "Bcc" *WSP ":"
                        (address-list / (*([CFWS] ",") [CFWS])) CRLF
 
    When multiple occurrences of destination address fields occur in a
    message, they SHOULD be treated as if the address list in the first
    occurrence of the field is combined with the address lists of the
    subsequent occurrences by adding a comma and concatenating.
 
 4.5.4.  Obsolete Identification Fields
 
    The obsolete "In-Reply-To:" and "References:" fields differ from the
    current syntax in that they allow phrase (words or quoted strings) to
    appear.  The obsolete forms of the left and right sides of msg-id
    allow interspersed CFWS, making them syntactically identical to
    local-part and domain, respectively.
 
    obs-message-id  =   "Message-ID" *WSP ":" msg-id CRLF
 
    obs-in-reply-to =   "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
 
    obs-references  =   "References" *WSP ":" *(phrase / msg-id) CRLF
 
    obs-id-left     =   local-part
 
    obs-id-right    =   domain
 
    For purposes of interpretation, the phrases in the "In-Reply-To:" and
    "References:" fields are ignored.
 
    Semantically, none of the optional CFWS in the local-part and the
    domain is part of the obs-id-left and obs-id-right, respectively.
 
 4.5.5.  Obsolete Informational Fields
 
    obs-subject     =   "Subject" *WSP ":" unstructured CRLF
 
    obs-comments    =   "Comments" *WSP ":" unstructured CRLF
 
    obs-keywords    =   "Keywords" *WSP ":" obs-phrase-list CRLF
 
 
 
 
 
 
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 4.5.6.  Obsolete Resent Fields
 
    The obsolete syntax adds a "Resent-Reply-To:" field, which consists
    of the field name, the optional comments and folding white space, the
    colon, and a comma separated list of addresses.
 
    obs-resent-from =   "Resent-From" *WSP ":" mailbox-list CRLF
 
    obs-resent-send =   "Resent-Sender" *WSP ":" mailbox CRLF
 
    obs-resent-date =   "Resent-Date" *WSP ":" date-time CRLF
 
    obs-resent-to   =   "Resent-To" *WSP ":" address-list CRLF
 
    obs-resent-cc   =   "Resent-Cc" *WSP ":" address-list CRLF
 
    obs-resent-bcc  =   "Resent-Bcc" *WSP ":"
                        (address-list / (*([CFWS] ",") [CFWS])) CRLF
 
    obs-resent-mid  =   "Resent-Message-ID" *WSP ":" msg-id CRLF
 
    obs-resent-rply =   "Resent-Reply-To" *WSP ":" address-list CRLF
 
    As with other resent fields, the "Resent-Reply-To:" field is to be
    treated as trace information only.
 
 4.5.7.  Obsolete Trace Fields
 
    The obs-return and obs-received are again given here as template
    definitions, just as return and received are in section 3.  Their
    full syntax is given in [RFC5321].
 
    obs-return      =   "Return-Path" *WSP ":" path CRLF
 
    obs-received    =   "Received" *WSP ":" *received-token CRLF
 
 4.5.8.  Obsolete optional fields
 
    obs-optional    =   field-name *WSP ":" unstructured CRLF
 
 5.  Security Considerations
 
    Care needs to be taken when displaying messages on a terminal or
    terminal emulator.  Powerful terminals may act on escape sequences
    and other combinations of US-ASCII control characters with a variety
    of consequences.  They can remap the keyboard or permit other
    modifications to the terminal that could lead to denial of service or
    even damaged data.  They can trigger (sometimes programmable)
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    answerback messages that can allow a message to cause commands to be
    issued on the recipient's behalf.  They can also affect the operation
    of terminal attached devices such as printers.  Message viewers may
    wish to strip potentially dangerous terminal escape sequences from
    the message prior to display.  However, other escape sequences appear
    in messages for useful purposes (cf. [ISO.2022.1994], [RFC2045],
    [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]) and therefore
    should not be stripped indiscriminately.
 
    Transmission of non-text objects in messages raises additional
    security issues.  These issues are discussed in [RFC2045], [RFC2046],
    [RFC2047], [RFC2049], [RFC4288], and [RFC4289].
 
    Many implementations use the "Bcc:" (blind carbon copy) field,
    described in section 3.6.3, to facilitate sending messages to
    recipients without revealing the addresses of one or more of the
    addressees to the other recipients.  Mishandling this use of "Bcc:"
    may disclose confidential information that could eventually lead to
    security problems through knowledge of even the existence of a
    particular mail address.  For example, if using the first method
    described in section 3.6.3, where the "Bcc:" line is removed from the
    message, blind recipients have no explicit indication that they have
    been sent a blind copy, except insofar as their address does not
    appear in the header section of a message.  Because of this, one of
    the blind addressees could potentially send a reply to all of the
    shown recipients and accidentally reveal that the message went to the
    blind recipient.  When the second method from section 3.6.3 is used,
    the blind recipient's address appears in the "Bcc:" field of a
    separate copy of the message.  If the "Bcc:" field sent contains all
    of the blind addressees, all of the "Bcc:" recipients will be seen by
    each "Bcc:" recipient.  Even if a separate message is sent to each
    "Bcc:" recipient with only the individual's address, implementations
    still need to be careful to process replies to the message as per
    section 3.6.3 so as not to accidentally reveal the blind recipient to
    other recipients.
 
 6.  IANA Considerations
 
    This document updates the registrations that appeared in [RFC4021]
    that referred to the definitions in [RFC2822].  IANA has updated the
    Permanent Message Header Field Repository with the following header
    fields, in accordance with the procedures set out in [RFC3864].
 
    Header field name:  Date
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.1)
 
 
 
 Resnick                     Standards Track                    [Page 39]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    Header field name:  From
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.2)
 
    Header field name:  Sender
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.2)
 
    Header field name:  Reply-To
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.2)
 
    Header field name:  To
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.3)
 
    Header field name:  Cc
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.3)
 
    Header field name:  Bcc
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.3)
 
    Header field name:  Message-ID
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.4)
 
    Header field name:  In-Reply-To
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.4)
 
 
 
 
 Resnick                     Standards Track                    [Page 40]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    Header field name:  References
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.4)
 
    Header field name:  Subject
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.5)
 
    Header field name:  Comments
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.5)
 
    Header field name:  Keywords
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.5)
 
    Header field name:  Resent-Date
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Resent-From
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Resent-Sender
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Resent-To
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
 
 
 
 Resnick                     Standards Track                    [Page 41]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    Header field name:  Resent-Cc
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Resent-Bcc
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Resent-Reply-To
    Applicable protocol:  Mail
    Status:  obsolete
    Author/Change controller:  IETF
    Specification document(s):  This document (section 4.5.6)
 
    Header field name:  Resent-Message-ID
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.6)
 
    Header field name:  Return-Path
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.7)
 
    Header field name:  Received
    Applicable protocol:  Mail
    Status:  standard
    Author/Change controller:  IETF
    Specification document(s):  This document (section 3.6.7)
    Related information:  [RFC5321]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 42]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.  Example Messages
 
    This section presents a selection of messages.  These are intended to
    assist in the implementation of this specification, but should not be
    taken as normative; that is to say, although the examples in this
    section were carefully reviewed, if there happens to be a conflict
    between these examples and the syntax described in sections 3 and 4
    of this document, the syntax in those sections is to be taken as
    correct.
 
    In the text version of this document, messages in this section are
    delimited between lines of "----".  The "----" lines are not part of
    the message itself.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 43]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.1.  Addressing Examples
 
    The following are examples of messages that might be sent between two
    individuals.
 
 Appendix A.1.1.  A Message from One Person to Another with Simple
                  Addressing
 
    This could be called a canonical message.  It has a single author,
    John Doe, a single recipient, Mary Smith, a subject, the date, a
    message identifier, and a textual message in the body.
 
    ----
    From: John Doe <jdoe@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
    If John's secretary Michael actually sent the message, even though
    John was the author and replies to this message should go back to
    him, the sender field would be used:
 
    ----
    From: John Doe <jdoe@machine.example>
    Sender: Michael Jones <mjones@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 44]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.1.2.  Different Types of Mailboxes
 
    This message includes multiple addresses in the destination fields
    and also uses several different forms of addresses.
 
    ----
    From: "Joe Q. Public" <john.q.public@example.com>
    To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
    Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
    Date: Tue, 1 Jul 2003 10:52:37 +0200
    Message-ID: <5678.21-Nov-1997@example.com>
 
    Hi everyone.
    ----
 
    Note that the display names for Joe Q. Public and Giant; "Big" Box
    needed to be enclosed in double-quotes because the former contains
    the period and the latter contains both semicolon and double-quote
    characters (the double-quote characters appearing as quoted-pair
    constructs).  Conversely, the display name for Who? could appear
    without them because the question mark is legal in an atom.  Notice
    also that jdoe@example.org and boss@nil.test have no display names
    associated with them at all, and jdoe@example.org uses the simpler
    address form without the angle brackets.
 
 Appendix A.1.3.  Group Addresses
 
    ----
    From: Pete <pete@silly.example>
    To: A Group:Ed Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
    Cc: Undisclosed recipients:;
    Date: Thu, 13 Feb 1969 23:32:54 -0330
    Message-ID: <testabcd.1234@silly.example>
 
    Testing.
    ----
 
    In this message, the "To:" field has a single group recipient named
    "A Group", which contains 3 addresses, and a "Cc:" field with an
    empty group recipient named Undisclosed recipients.
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 45]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.2.  Reply Messages
 
    The following is a series of three messages that make up a
    conversation thread between John and Mary.  John first sends a
    message to Mary, Mary then replies to John's message, and then John
    replies to Mary's reply message.
 
    Note especially the "Message-ID:", "References:", and "In-Reply-To:"
    fields in each message.
 
    ----
    From: John Doe <jdoe@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
    When sending replies, the Subject field is often retained, though
    prepended with "Re: " as described in section 3.6.5.
 
    ----
    From: Mary Smith <mary@example.net>
    To: John Doe <jdoe@machine.example>
    Reply-To: "Mary Smith: Personal Account" <smith@home.example>
    Subject: Re: Saying Hello
    Date: Fri, 21 Nov 1997 10:01:10 -0600
    Message-ID: <3456@example.net>
    In-Reply-To: <1234@local.machine.example>
    References: <1234@local.machine.example>
 
    This is a reply to your hello.
    ----
 
    Note the "Reply-To:" field in the above message.  When John replies
    to Mary's message above, the reply should go to the address in the
    "Reply-To:" field instead of the address in the "From:" field.
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 46]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    ----
    To: "Mary Smith: Personal Account" <smith@home.example>
    From: John Doe <jdoe@machine.example>
    Subject: Re: Saying Hello
    Date: Fri, 21 Nov 1997 11:00:00 -0600
    Message-ID: <abcd.1234@local.machine.test>
    In-Reply-To: <3456@example.net>
    References: <1234@local.machine.example> <3456@example.net>
 
    This is a reply to your reply.
    ----
 
 Appendix A.3.  Resent Messages
 
    Start with the message that has been used as an example several
    times:
 
    ----
    From: John Doe <jdoe@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
    Say that Mary, upon receiving this message, wishes to send a copy of
    the message to Jane such that (a) the message would appear to have
    come straight from John; (b) if Jane replies to the message, the
    reply should go back to John; and (c) all of the original
    information, like the date the message was originally sent to Mary,
    the message identifier, and the original addressee, is preserved.  In
    this case, resent fields are prepended to the message:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 47]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    ----
    Resent-From: Mary Smith <mary@example.net>
    Resent-To: Jane Brown <j-brown@other.example>
    Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
    Resent-Message-ID: <78910@example.net>
    From: John Doe <jdoe@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
    If Jane, in turn, wished to resend this message to another person,
    she would prepend her own set of resent header fields to the above
    and send that.  (Note that for brevity, trace fields are not shown.)
 
 Appendix A.4.  Messages with Trace Fields
 
    As messages are sent through the transport system as described in
    [RFC5321], trace fields are prepended to the message.  The following
    is an example of what those trace fields might look like.  Note that
    there is some folding white space in the first one since these lines
    can be long.
 
    ----
    Received: from x.y.test
       by example.net
       via TCP
       with ESMTP
       id ABC12345
       for <mary@example.net>;  21 Nov 1997 10:05:43 -0600
    Received: from node.example by x.y.test; 21 Nov 1997 10:01:22 -0600
    From: John Doe <jdoe@node.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: Fri, 21 Nov 1997 09:55:06 -0600
    Message-ID: <1234@local.node.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 48]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.5.  White Space, Comments, and Other Oddities
 
    White space, including folding white space, and comments can be
    inserted between many of the tokens of fields.  Taking the example
    from A.1.3, white space and comments can be inserted into all of the
    fields.
 
    ----
    From: Pete(A nice \) chap) <pete(his account)@silly.test(his host)>
    To:A Group(Some people)
         :Chris Jones <c@(Chris's host.)public.example>,
             joe@example.org,
      John <jdoe@one.test> (my dear friend); (the end of the group)
    Cc:(Empty list)(start)Hidden recipients  :(nobody(that I know))  ;
    Date: Thu,
          13
            Feb
              1969
          23:32
                   -0330 (Newfoundland Time)
    Message-ID:              <testabcd.1234@silly.test>
 
    Testing.
    ----
 
    The above example is aesthetically displeasing, but perfectly legal.
    Note particularly (1) the comments in the "From:" field (including
    one that has a ")" character appearing as part of a quoted-pair); (2)
    the white space absent after the ":" in the "To:" field as well as
    the comment and folding white space after the group name, the special
    character (".") in the comment in Chris Jones's address, and the
    folding white space before and after "joe@example.org,"; (3) the
    multiple and nested comments in the "Cc:" field as well as the
    comment immediately following the ":" after "Cc"; (4) the folding
    white space (but no comments except at the end) and the missing
    seconds in the time of the date field; and (5) the white space before
    (but not within) the identifier in the "Message-ID:" field.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 49]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.6.  Obsoleted Forms
 
    The following are examples of obsolete (that is, the "MUST NOT
    generate") syntactic elements described in section 4 of this
    document.
 
 Appendix A.6.1.  Obsolete Addressing
 
    Note in the example below the lack of quotes around Joe Q. Public,
    the route that appears in the address for Mary Smith, the two commas
    that appear in the "To:" field, and the spaces that appear around the
    "." in the jdoe address.
 
    ----
    From: Joe Q. Public <john.q.public@example.com>
    To: Mary Smith <@node.test:mary@example.net>, , jdoe@test  . example
    Date: Tue, 1 Jul 2003 10:52:37 +0200
    Message-ID: <5678.21-Nov-1997@example.com>
 
    Hi everyone.
    ----
 
 Appendix A.6.2.  Obsolete Dates
 
    The following message uses an obsolete date format, including a non-
    numeric time zone and a two digit year.  Note that although the day-
    of-week is missing, that is not specific to the obsolete syntax; it
    is optional in the current syntax as well.
 
    ----
    From: John Doe <jdoe@machine.example>
    To: Mary Smith <mary@example.net>
    Subject: Saying Hello
    Date: 21 Nov 97 09:55:06 GMT
    Message-ID: <1234@local.machine.example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 50]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix A.6.3.  Obsolete White Space and Comments
 
    White space and comments can appear between many more elements than
    in the current syntax.  Also, folding lines that are made up entirely
    of white space are legal.
 
    ----
    From  : John Doe <jdoe@machine(comment).  example>
    To    : Mary Smith
    __
              <mary@example.net>
    Subject     : Saying Hello
    Date  : Fri, 21 Nov 1997 09(comment):   55  :  06 -0600
    Message-ID  : <1234   @   local(blah)  .machine .example>
 
    This is a message just to say hello.
    So, "Hello".
    ----
 
    Note especially the second line of the "To:" field.  It starts with
    two space characters.  (Note that "__" represent blank spaces.)
    Therefore, it is considered part of the folding, as described in
    section 4.2.  Also, the comments and white space throughout
    addresses, dates, and message identifiers are all part of the
    obsolete syntax.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 51]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 Appendix B.  Differences from Earlier Specifications
 
    This appendix contains a list of changes that have been made in the
    Internet Message Format from earlier specifications, specifically
    [RFC0822], [RFC1123], and [RFC2822].  Items marked with an asterisk
    (*) below are items which appear in section 4 of this document and
    therefore can no longer be generated.
 
    The following are the changes made from [RFC0822] and [RFC1123] to
    [RFC2822] that remain in this document:
 
    1.   Period allowed in obsolete form of phrase.
    2.   ABNF moved out of document, now in [RFC5234].
    3.   Four or more digits allowed for year.
    4.   Header field ordering (and lack thereof) made explicit.
    5.   Encrypted header field removed.
    6.   Specifically allow and give meaning to "-0000" time zone.
    7.   Folding white space is not allowed between every token.
    8.   Requirement for destinations removed.
    9.   Forwarding and resending redefined.
    10.  Extension header fields no longer specifically called out.
    11.  ASCII 0 (null) removed.*
    12.  Folding continuation lines cannot contain only white space.*
    13.  Free insertion of comments not allowed in date.*
    14.  Non-numeric time zones not allowed.*
    15.  Two digit years not allowed.*
    16.  Three digit years interpreted, but not allowed for generation.*
    17.  Routes in addresses not allowed.*
    18.  CFWS within local-parts and domains not allowed.*
    19.  Empty members of address lists not allowed.*
    20.  Folding white space between field name and colon not allowed.*
    21.  Comments between field name and colon not allowed.
    22.  Tightened syntax of in-reply-to and references.*
    23.  CFWS within msg-id not allowed.*
    24.  Tightened semantics of resent fields as informational only.
    25.  Resent-Reply-To not allowed.*
    26.  No multiple occurrences of fields (except resent and received).*
    27.  Free CR and LF not allowed.*
    28.  Line length limits specified.
    29.  Bcc more clearly specified.
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 52]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    The following are changes from [RFC2822].
    1.   Assorted typographical/grammatical errors fixed and
         clarifications made.
    2.   Changed "standard" to "document" or "specification" throughout.
    3.   Made distinction between "header field" and "header section".
    4.   Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
    5.   Moved discussion of specials to the "Atom" section.  Moved text
         to "Overall message syntax" section.
    6.   Simplified CFWS syntax.
    7.   Fixed unstructured syntax.
    8.   Changed date and time syntax to deal with white space in
         obsolete date syntax.
    9.   Removed quoted-pair from domain literals and message
         identifiers.*
    10.  Clarified that other specifications limit domain syntax.
    11.  Simplified "Bcc:" and "Resent-Bcc:" syntax.
    12.  Allowed optional-field to appear within trace information.
    13.  Removed no-fold-quote from msg-id.  Clarified syntax
         limitations.
    14.  Generalized "Received:" syntax to fix bugs and move definition
         out of this document.
    15.  Simplified obs-qp.  Fixed and simplified obs-utext (which now
         only appears in the obsolete syntax).  Removed obs-text and obs-
         char, adding obs-body.
    16.  Fixed obsolete date syntax to allow for more (or less) comments
         and white space.
    17.  Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list,
         obs-addr-list, obs-phrase-list, and the newly added obs-group-
         list).
    18.  Fixed obs-reply-to syntax.
    19.  Fixed obs-bcc and obs-resent-bcc to allow empty lists.
    20.  Removed obs-path.
 
 Appendix C.  Acknowledgements
 
    Many people contributed to this document.  They included folks who
    participated in the Detailed Revision and Update of Messaging
    Standards (DRUMS) Working Group of the Internet Engineering Task
    Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
    people who simply sent their comments in via email.  The editor is
    deeply indebted to them all and thanks them sincerely.  The below
    list includes everyone who sent email concerning both this document
    and [RFC2822].  Hopefully, everyone who contributed is named here:
 
    +--------------------+----------------------+---------------------+
    | Matti Aarnio       | Tanaka Akira         | Russ Allbery        |
    | Eric Allman        | Harald Alvestrand    | Ran Atkinson        |
    | Jos Backus         | Bruce Balden         | Dave Barr           |
 
 
 
 Resnick                     Standards Track                    [Page 53]
 
 RFC 5322                Internet Message Format             October 2008
 
 
    | Alan Barrett       | John Beck            | J Robert von Behren |
    | Jos den Bekker     | D J Bernstein        | James Berriman      |
    | Oliver Block       | Norbert Bollow       | Raj Bose            |
    | Antony Bowesman    | Scott Bradner        | Randy Bush          |
    | Tom Byrer          | Bruce Campbell       | Larry Campbell      |
    | W J Carpenter      | Michael Chapman      | Richard Clayton     |
    | Maurizio Codogno   | Jim Conklin          | R Kelley Cook       |
    | Nathan Coulter     | Steve Coya           | Mark Crispin        |
    | Dave Crocker       | Matt Curtin          | Michael D'Errico    |
    | Cyrus Daboo        | Michael D Dean       | Jutta Degener       |
    | Mark Delany        | Steve Dorner         | Harold A Driscoll   |
    | Michael Elkins     | Frank Ellerman       | Robert Elz          |
    | Johnny Eriksson    | Erik E Fair          | Roger Fajman        |
    | Patrik Faltstrom   | Claus Andre Faerber  | Barry Finkel        |
    | Erik Forsberg      | Chuck Foster         | Paul Fox            |
    | Klaus M Frank      | Ned Freed            | Jochen Friedrich    |
    | Randall C Gellens  | Sukvinder Singh Gill | Tim Goodwin         |
    | Philip Guenther    | Arnt Gulbrandsen     | Eric A Hall         |
    | Tony Hansen        | John Hawkinson       | Philip Hazel        |
    | Kai Henningsen     | Robert Herriot       | Paul Hethmon        |
    | Jim Hill           | Alfred Hoenes        | Paul E Hoffman      |
    | Steve Hole         | Kari Hurtta          | Marco S Hyman       |
    | Ofer Inbar         | Olle Jarnefors       | Kevin Johnson       |
    | Sudish Joseph      | Maynard Kang         | Prabhat Keni        |
    | John C Klensin     | Graham Klyne         | Brad Knowles        |
    | Shuhei Kobayashi   | Peter Koch           | Dan Kohn            |
    | Christian Kuhtz    | Anand Kumria         | Steen Larsen        |
    | Eliot Lear         | Barry Leiba          | Jay Levitt          |
    | Bruce Lilly        | Lars-Johan Liman     | Charles Lindsey     |
    | Pete Loshin        | Simon Lyall          | Bill Manning        |
    | John Martin        | Mark Martinec        | Larry Masinter      |
    | Denis McKeon       | William P McQuillan  | Alexey Melnikov     |
    | Perry E Metzger    | Steven Miller        | S Moonesamy         |
    | Keith Moore        | John Gardiner Myers  | Chris Newman        |
    | John W Noerenberg  | Eric Norman          | Mike O'Dell         |
    | Larry Osterman     | Paul Overell         | Jacob Palme         |
    | Michael A Patton   | Uzi Paz              | Michael A Quinlan   |
    | Robert Rapplean    | Eric S Raymond       | Sam Roberts         |
    | Hugh Sasse         | Bart Schaefer        | Tom Scola           |
    | Wolfgang Segmuller | Nick Shelness        | John Stanley        |
    | Einar Stefferud    | Jeff Stephenson      | Bernard Stern       |
    | Peter Sylvester    | Mark Symons          | Eric Thomas         |
    | Lee Thompson       | Karel De Vriendt     | Matthew Wall        |
    | Rolf Weber         | Brent B Welch        | Dan Wing            |
    | Jack De Winter     | Gregory J Woodhouse  | Greg A Woods        |
    | Kazu Yamamoto      | Alain Zahm           | Jamie Zawinski      |
    | Timothy S Zurcher  |                      |                     |
    +--------------------+----------------------+---------------------+
 
 
 
 Resnick                     Standards Track                    [Page 54]
 
 RFC 5322                Internet Message Format             October 2008
 
 
 7.  References
 
 7.1.  Normative References
 
    [ANSI.X3-4.1986]  American National Standards Institute, "Coded
                      Character Set - 7-bit American Standard Code for
                      Information Interchange", ANSI X3.4, 1986.
 
    [RFC1034]         Mockapetris, P., "Domain names - concepts and
                      facilities", STD 13, RFC 1034, November 1987.
 
    [RFC1035]         Mockapetris, P., "Domain names - implementation and
                      specification", STD 13, RFC 1035, November 1987.
 
    [RFC1123]         Braden, R., "Requirements for Internet Hosts -
                      Application and Support", STD 3, RFC 1123,
                      October 1989.
 
    [RFC2119]         Bradner, S., "Key words for use in RFCs to Indicate
                      Requirement Levels", BCP 14, RFC 2119, March 1997.
 
    [RFC5234]         Crocker, D. and P. Overell, "Augmented BNF for
                      Syntax Specifications: ABNF", STD 68, RFC 5234,
                      January 2008.
 
 7.2.  Informative References
 
    [RFC0822]         Crocker, D., "Standard for the format of ARPA
                      Internet text messages", STD 11, RFC 822,
                      August 1982.
 
    [RFC1305]         Mills, D., "Network Time Protocol (Version 3)
                      Specification, Implementation", RFC 1305,
                      March 1992.
 
    [ISO.2022.1994]   International Organization for Standardization,
                      "Information technology - Character code structure
                      and extension techniques", ISO Standard 2022, 1994.
 
    [RFC2045]         Freed, N. and N. Borenstein, "Multipurpose Internet
                      Mail Extensions (MIME) Part One: Format of Internet
                      Message Bodies", RFC 2045, November 1996.
 
    [RFC2046]         Freed, N. and N. Borenstein, "Multipurpose Internet
                      Mail Extensions (MIME) Part Two: Media Types",
                      RFC 2046, November 1996.
 
 
 
 
 
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 RFC 5322                Internet Message Format             October 2008
 
 
    [RFC2047]         Moore, K., "MIME (Multipurpose Internet Mail
                      Extensions) Part Three: Message Header Extensions
                      for Non-ASCII Text", RFC 2047, November 1996.
 
    [RFC2049]         Freed, N. and N. Borenstein, "Multipurpose Internet
                      Mail Extensions (MIME) Part Five: Conformance
                      Criteria and Examples", RFC 2049, November 1996.
 
    [RFC2822]         Resnick, P., "Internet Message Format", RFC 2822,
                      April 2001.
 
    [RFC3864]         Klyne, G., Nottingham, M., and J. Mogul,
                      "Registration Procedures for Message Header
                      Fields", BCP 90, RFC 3864, September 2004.
 
    [RFC4021]         Klyne, G. and J. Palme, "Registration of Mail and
                      MIME Header Fields", RFC 4021, March 2005.
 
    [RFC4288]         Freed, N. and J. Klensin, "Media Type
                      Specifications and Registration Procedures",
                      BCP 13, RFC 4288, December 2005.
 
    [RFC4289]         Freed, N. and J. Klensin, "Multipurpose Internet
                      Mail Extensions (MIME) Part Four: Registration
                      Procedures", BCP 13, RFC 4289, December 2005.
 
    [RFC5321]         Klensin, J., "Simple Mail Transfer Protocol",
                      RFC 5321, October 2008.
 
 Author's Address
 
    Peter W. Resnick (editor)
    Qualcomm Incorporated
    5775 Morehouse Drive
    San Diego, CA  92121-1714
    US
 
    Phone: +1 858 651 4478
    EMail: presnick@qualcomm.com
    URI:   http://www.qualcomm.com/~presnick/
 
 
 
 
 
 
 
 
 
 
 
 Resnick                     Standards Track                    [Page 56]
 
 RFC 5322                Internet Message Format             October 2008
 
 
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