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rfc:rfc5322

Network Working Group P. Resnick, Ed. Request for Comments: 5322 Qualcomm Incorporated Obsoletes: 2822 October 2008 Updates: 4021 Category: Standards Track

                      Internet Message Format

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document specifies the Internet Message Format (IMF), a syntax
 for text messages that are sent between computer users, within the
 framework of "electronic mail" messages.  This specification is a
 revision of Request For Comments (RFC) 2822, which itself superseded
 Request For Comments (RFC) 822, "Standard for the Format of ARPA
 Internet Text Messages", updating it to reflect current practice and
 incorporating incremental changes that were specified in other RFCs.

Resnick Standards Track [Page 1] RFC 5322 Internet Message Format October 2008

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.2.  Notational Conventions . . . . . . . . . . . . . . . . . .  5
     1.2.1.  Requirements Notation  . . . . . . . . . . . . . . . .  5
     1.2.2.  Syntactic Notation . . . . . . . . . . . . . . . . . .  5
     1.2.3.  Structure of This Document . . . . . . . . . . . . . .  5
 2.  Lexical Analysis of Messages . . . . . . . . . . . . . . . . .  6
   2.1.  General Description  . . . . . . . . . . . . . . . . . . .  6
     2.1.1.  Line Length Limits . . . . . . . . . . . . . . . . . .  7
   2.2.  Header Fields  . . . . . . . . . . . . . . . . . . . . . .  8
     2.2.1.  Unstructured Header Field Bodies . . . . . . . . . . .  8
     2.2.2.  Structured Header Field Bodies . . . . . . . . . . . .  8
     2.2.3.  Long Header Fields . . . . . . . . . . . . . . . . . .  8
   2.3.  Body . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
 3.  Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   3.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
   3.2.  Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
     3.2.1.  Quoted characters  . . . . . . . . . . . . . . . . . . 10
     3.2.2.  Folding White Space and Comments . . . . . . . . . . . 11
     3.2.3.  Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
     3.2.4.  Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
     3.2.5.  Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
   3.3.  Date and Time Specification  . . . . . . . . . . . . . . . 14
   3.4.  Address Specification  . . . . . . . . . . . . . . . . . . 16
     3.4.1.  Addr-Spec Specification  . . . . . . . . . . . . . . . 17
   3.5.  Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
   3.6.  Field Definitions  . . . . . . . . . . . . . . . . . . . . 19
     3.6.1.  The Origination Date Field . . . . . . . . . . . . . . 22
     3.6.2.  Originator Fields  . . . . . . . . . . . . . . . . . . 22
     3.6.3.  Destination Address Fields . . . . . . . . . . . . . . 23
     3.6.4.  Identification Fields  . . . . . . . . . . . . . . . . 25
     3.6.5.  Informational Fields . . . . . . . . . . . . . . . . . 27
     3.6.6.  Resent Fields  . . . . . . . . . . . . . . . . . . . . 28
     3.6.7.  Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
     3.6.8.  Optional Fields  . . . . . . . . . . . . . . . . . . . 30
 4.  Obsolete Syntax  . . . . . . . . . . . . . . . . . . . . . . . 31
   4.1.  Miscellaneous Obsolete Tokens  . . . . . . . . . . . . . . 32
   4.2.  Obsolete Folding White Space . . . . . . . . . . . . . . . 33
   4.3.  Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
   4.4.  Obsolete Addressing  . . . . . . . . . . . . . . . . . . . 35
   4.5.  Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
     4.5.1.  Obsolete Origination Date Field  . . . . . . . . . . . 36
     4.5.2.  Obsolete Originator Fields . . . . . . . . . . . . . . 36
     4.5.3.  Obsolete Destination Address Fields  . . . . . . . . . 37
     4.5.4.  Obsolete Identification Fields . . . . . . . . . . . . 37
     4.5.5.  Obsolete Informational Fields  . . . . . . . . . . . . 37

Resnick Standards Track [Page 2] RFC 5322 Internet Message Format October 2008

     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

Resnick Standards Track [Page 3] RFC 5322 Internet Message Format October 2008

1. Introduction

1.1. Scope

 This document specifies the Internet Message Format (IMF), a syntax
 for text messages that are sent between computer users, within the
 framework of "electronic mail" messages.  This specification is an
 update to [RFC2822], which itself superseded [RFC0822], updating it
 to reflect current practice and incorporating incremental changes
 that were specified in other RFCs such as [RFC1123].
 This document specifies a syntax only for text messages.  In
 particular, it makes no provision for the transmission of images,
 audio, or other sorts of structured data in electronic mail messages.
 There are several extensions published, such as the MIME document
 series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
 for the transmission of such data through electronic mail, either by
 extending the syntax provided here or by structuring such messages to
 conform to this syntax.  Those mechanisms are outside of the scope of
 this specification.
 In the context of electronic mail, messages are viewed as having an
 envelope and contents.  The envelope contains whatever information is
 needed to accomplish transmission and delivery.  (See [RFC5321] for a
 discussion of the envelope.)  The contents comprise the object to be
 delivered to the recipient.  This specification applies only to the
 format and some of the semantics of message contents.  It contains no
 specification of the information in the envelope.
 However, some message systems may use information from the contents
 to create the envelope.  It is intended that this specification
 facilitate the acquisition of such information by programs.
 This specification is intended as a definition of what message
 content format is to be passed between systems.  Though some message
 systems locally store messages in this format (which eliminates the
 need for translation between formats) and others use formats that
 differ from the one specified in this specification, local storage is
 outside of the scope of this specification.
    Note: This specification is not intended to dictate the internal
    formats used by sites, the specific message system features that
    they are expected to support, or any of the characteristics of
    user interface programs that create or read messages.  In
    addition, this document does not specify an encoding of the
    characters for either transport or storage; that is, it does not
    specify the number of bits used or how those bits are specifically
    transferred over the wire or stored on disk.

Resnick Standards Track [Page 4] RFC 5322 Internet Message Format October 2008

1.2. Notational Conventions

1.2.1. Requirements Notation

 This document occasionally uses terms that appear in capital letters.
 When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
 NOT", and "MAY" appear capitalized, they are being used to indicate
 particular requirements of this specification.  A discussion of the
 meanings of these terms appears in [RFC2119].

1.2.2. Syntactic Notation

 This specification uses the Augmented Backus-Naur Form (ABNF)
 [RFC5234] notation for the formal definitions of the syntax of
 messages.  Characters will be specified either by a decimal value
 (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
 a case-insensitive literal value enclosed in quotation marks (e.g.,
 "A" for either uppercase or lowercase A).

1.2.3. Structure of This Document

 This document is divided into several sections.
 This section, section 1, is a short introduction to the document.
 Section 2 lays out the general description of a message and its
 constituent parts.  This is an overview to help the reader understand
 some of the general principles used in the later portions of this
 document.  Any examples in this section MUST NOT be taken as
 specification of the formal syntax of any part of a message.
 Section 3 specifies formal ABNF rules for the structure of each part
 of a message (the syntax) and describes the relationship between
 those parts and their meaning in the context of a message (the
 semantics).  That is, it lays out the actual rules for the structure
 of each part of a message (the syntax) as well as a description of
 the parts and instructions for their interpretation (the semantics).
 This includes analysis of the syntax and semantics of subparts of
 messages that have specific structure.  The syntax included in
 section 3 represents messages as they MUST be created.  There are
 also notes in section 3 to indicate if any of the options specified
 in the syntax SHOULD be used over any of the others.
 Both sections 2 and 3 describe messages that are legal to generate
 for purposes of this specification.

Resnick Standards Track [Page 5] RFC 5322 Internet Message Format October 2008

 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".)

Resnick Standards Track [Page 6] RFC 5322 Internet Message Format October 2008

 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.

Resnick Standards Track [Page 7] RFC 5322 Internet Message Format October 2008

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.

Resnick Standards Track [Page 8] RFC 5322 Internet Message Format October 2008

 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.

Resnick Standards Track [Page 9] RFC 5322 Internet Message Format October 2008

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.

Resnick Standards Track [Page 10] RFC 5322 Internet Message Format October 2008

 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

Resnick Standards Track [Page 11] RFC 5322 Internet Message Format October 2008

 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.

Resnick Standards Track [Page 12] RFC 5322 Internet Message Format October 2008

 atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
                     "!" / "#" /        ;  characters not including
                     "$" / "%" /        ;  specials.  Used for atoms.
                     "&" / "'" /
                     "*" / "+" /
                     "-" / "/" /
                     "=" / "?" /
                     "^" / "_" /
                     "`" / "{" /
                     "|" / "}" /
                     "~"
 atom            =   [CFWS] 1*atext [CFWS]
 dot-atom-text   =   1*atext *("." 1*atext)
 dot-atom        =   [CFWS] dot-atom-text [CFWS]
 specials        =   "(" / ")" /        ; Special characters that do
                     "<" / ">" /        ;  not appear in atext
                     "[" / "]" /
                     ":" / ";" /
                     "@" / "\" /
                     "," / "." /
                     DQUOTE
 Both atom and dot-atom are interpreted as a single unit, comprising
 the string of characters that make it up.  Semantically, the optional
 comments and FWS surrounding the rest of the characters are not part
 of the atom; the atom is only the run of atext characters in an atom,
 or the atext and "." characters in a dot-atom.

3.2.4. Quoted Strings

 Strings of characters that include characters other than those
 allowed in atoms can be represented in a quoted string format, where
 the characters are surrounded by quote (DQUOTE, ASCII value 34)
 characters.

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 qtext           =   %d33 /             ; Printable US-ASCII
                     %d35-91 /          ;  characters not including
                     %d93-126 /         ;  "\" or the quote character
                     obs-qtext
 qcontent        =   qtext / quoted-pair
 quoted-string   =   [CFWS]
                     DQUOTE *([FWS] qcontent) [FWS] DQUOTE
                     [CFWS]
 A quoted-string is treated as a unit.  That is, quoted-string is
 identical to atom, semantically.  Since a quoted-string is allowed to
 contain FWS, folding is permitted.  Also note that since quoted-pair
 is allowed in a quoted-string, the quote and backslash characters may
 appear in a quoted-string so long as they appear as a quoted-pair.
 Semantically, neither the optional CFWS outside of the quote
 characters nor the quote characters themselves are part of the
 quoted-string; the quoted-string is what is contained between the two
 quote characters.  As stated earlier, the "\" in any quoted-pair and
 the CRLF in any FWS/CFWS that appears within the quoted-string are
 semantically "invisible" and therefore not part of the quoted-string
 either.

3.2.5. Miscellaneous Tokens

 Three additional tokens are defined: word and phrase for combinations
 of atoms and/or quoted-strings, and unstructured for use in
 unstructured header fields and in some places within structured
 header fields.
 word            =   atom / quoted-string
 phrase          =   1*word / obs-phrase
 unstructured    =   (*([FWS] VCHAR) *WSP) / obs-unstruct

3.3. Date and Time Specification

 Date and time values occur in several header fields.  This section
 specifies the syntax for a full date and time specification.  Though
 folding white space is permitted throughout the date-time
 specification, it is RECOMMENDED that a single space be used in each
 place that FWS appears (whether it is required or optional); some
 older implementations will not interpret longer sequences of folding
 white space correctly.

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 date-time       =   [ day-of-week "," ] date time [CFWS]
 day-of-week     =   ([FWS] day-name) / obs-day-of-week
 day-name        =   "Mon" / "Tue" / "Wed" / "Thu" /
                     "Fri" / "Sat" / "Sun"
 date            =   day month year
 day             =   ([FWS] 1*2DIGIT FWS) / obs-day
 month           =   "Jan" / "Feb" / "Mar" / "Apr" /
                     "May" / "Jun" / "Jul" / "Aug" /
                     "Sep" / "Oct" / "Nov" / "Dec"
 year            =   (FWS 4*DIGIT FWS) / obs-year
 time            =   time-of-day zone
 time-of-day     =   hour ":" minute [ ":" second ]
 hour            =   2DIGIT / obs-hour
 minute          =   2DIGIT / obs-minute
 second          =   2DIGIT / obs-second
 zone            =   (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
 The day is the numeric day of the month.  The year is any numeric
 year 1900 or later.
 The time-of-day specifies the number of hours, minutes, and
 optionally seconds since midnight of the date indicated.
 The date and time-of-day SHOULD express local time.
 The zone specifies the offset from Coordinated Universal Time (UTC,
 formerly referred to as "Greenwich Mean Time") that the date and
 time-of-day represent.  The "+" or "-" indicates whether the time-of-
 day is ahead of (i.e., east of) or behind (i.e., west of) Universal
 Time.  The first two digits indicate the number of hours difference
 from Universal Time, and the last two digits indicate the number of
 additional minutes difference from Universal Time.  (Hence, +hhmm
 means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
 minutes).  The form "+0000" SHOULD be used to indicate a time zone at
 Universal Time.  Though "-0000" also indicates Universal Time, it is

Resnick Standards Track [Page 15] RFC 5322 Internet Message Format October 2008

 used to indicate that the time was generated on a system that may be
 in a local time zone other than Universal Time and that the date-time
 contains no information about the local time zone.
 A date-time specification MUST be semantically valid.  That is, the
 day-of-week (if included) MUST be the day implied by the date, the
 numeric day-of-month MUST be between 1 and the number of days allowed
 for the specified month (in the specified year), the time-of-day MUST
 be in the range 00:00:00 through 23:59:60 (the number of seconds
 allowing for a leap second; see [RFC1305]), and the last two digits
 of the zone MUST be within the range 00 through 59.

3.4. Address Specification

 Addresses occur in several message header fields to indicate senders
 and recipients of messages.  An address may either be an individual
 mailbox, or a group of mailboxes.
 address         =   mailbox / group
 mailbox         =   name-addr / addr-spec
 name-addr       =   [display-name] angle-addr
 angle-addr      =   [CFWS] "<" addr-spec ">" [CFWS] /
                     obs-angle-addr
 group           =   display-name ":" [group-list] ";" [CFWS]
 display-name    =   phrase
 mailbox-list    =   (mailbox *("," mailbox)) / obs-mbox-list
 address-list    =   (address *("," address)) / obs-addr-list
 group-list      =   mailbox-list / CFWS / obs-group-list
 A mailbox receives mail.  It is a conceptual entity that does not
 necessarily pertain to file storage.  For example, some sites may
 choose to print mail on a printer and deliver the output to the
 addressee's desk.
 Normally, a mailbox is composed of two parts: (1) an optional display
 name that indicates the name of the recipient (which can be a person
 or a system) that could be displayed to the user of a mail
 application, and (2) an addr-spec address enclosed in angle brackets

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 ("<" and ">").  There is an alternate simple form of a mailbox where
 the addr-spec address appears alone, without the recipient's name or
 the angle brackets.  The Internet addr-spec address is described in
 section 3.4.1.
    Note: Some legacy implementations used the simple form where the
    addr-spec appears without the angle brackets, but included the
    name of the recipient in parentheses as a comment following the
    addr-spec.  Since the meaning of the information in a comment is
    unspecified, implementations SHOULD use the full name-addr form of
    the mailbox, instead of the legacy form, to specify the display
    name associated with a mailbox.  Also, because some legacy
    implementations interpret the comment, comments generally SHOULD
    NOT be used in address fields to avoid confusing such
    implementations.
 When it is desirable to treat several mailboxes as a single unit
 (i.e., in a distribution list), the group construct can be used.  The
 group construct allows the sender to indicate a named group of
 recipients.  This is done by giving a display name for the group,
 followed by a colon, followed by a comma-separated list of any number
 of mailboxes (including zero and one), and ending with a semicolon.
 Because the list of mailboxes can be empty, using the group construct
 is also a simple way to communicate to recipients that the message
 was sent to one or more named sets of recipients, without actually
 providing the individual mailbox address for any of those recipients.

3.4.1. Addr-Spec Specification

 An addr-spec is a specific Internet identifier that contains a
 locally interpreted string followed by the at-sign character ("@",
 ASCII value 64) followed by an Internet domain.  The locally
 interpreted string is either a quoted-string or a dot-atom.  If the
 string can be represented as a dot-atom (that is, it contains no
 characters other than atext characters or "." surrounded by atext
 characters), then the dot-atom form SHOULD be used and the quoted-
 string form SHOULD NOT be used.  Comments and folding white space
 SHOULD NOT be used around the "@" in the addr-spec.
    Note: A liberal syntax for the domain portion of addr-spec is
    given here.  However, the domain portion contains addressing
    information specified by and used in other protocols (e.g.,
    [RFC1034], [RFC1035], [RFC1123], [RFC5321]).  It is therefore
    incumbent upon implementations to conform to the syntax of
    addresses for the context in which they are used.

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 addr-spec       =   local-part "@" domain
 local-part      =   dot-atom / quoted-string / obs-local-part
 domain          =   dot-atom / domain-literal / obs-domain
 domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
 dtext           =   %d33-90 /          ; Printable US-ASCII
                     %d94-126 /         ;  characters not including
                     obs-dtext          ;  "[", "]", or "\"
 The domain portion identifies the point to which the mail is
 delivered.  In the dot-atom form, this is interpreted as an Internet
 domain name (either a host name or a mail exchanger name) as
 described in [RFC1034], [RFC1035], and [RFC1123].  In the domain-
 literal form, the domain is interpreted as the literal Internet
 address of the particular host.  In both cases, how addressing is
 used and how messages are transported to a particular host is covered
 in separate documents, such as [RFC5321].  These mechanisms are
 outside of the scope of this document.
 The local-part portion is a domain-dependent string.  In addresses,
 it is simply interpreted on the particular host as a name of a
 particular mailbox.

3.5. Overall Message Syntax

 A message consists of header fields, optionally followed by a message
 body.  Lines in a message MUST be a maximum of 998 characters
 excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
 characters excluding the CRLF.  (See section 2.1.1 for explanation.)
 In a message body, though all of the characters listed in the text
 rule MAY be used, the use of US-ASCII control characters (values 1
 through 8, 11, 12, and 14 through 31) is discouraged since their
 interpretation by receivers for display is not guaranteed.
 message         =   (fields / obs-fields)
                     [CRLF body]
 body            =   (*(*998text CRLF) *998text) / obs-body
 text            =   %d1-9 /            ; Characters excluding CR
                     %d11 /             ;  and LF
                     %d12 /
                     %d14-127

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 The header fields carry most of the semantic information and are
 defined in section 3.6.  The body is simply a series of lines of text
 that are uninterpreted for the purposes of this specification.

3.6. Field Definitions

 The header fields of a message are defined here.  All header fields
 have the same general syntactic structure: a field name, followed by
 a colon, followed by the field body.  The specific syntax for each
 header field is defined in the subsequent sections.
    Note: In the ABNF syntax for each field in subsequent sections,
    each field name is followed by the required colon.  However, for
    brevity, sometimes the colon is not referred to in the textual
    description of the syntax.  It is, nonetheless, required.
 It is important to note that the header fields are not guaranteed to
 be in a particular order.  They may appear in any order, and they
 have been known to be reordered occasionally when transported over
 the Internet.  However, for the purposes of this specification,
 header fields SHOULD NOT be reordered when a message is transported
 or transformed.  More importantly, the trace header fields and resent
 header fields MUST NOT be reordered, and SHOULD be kept in blocks
 prepended to the message.  See sections 3.6.6 and 3.6.7 for more
 information.
 The only required header fields are the origination date field and
 the originator address field(s).  All other header fields are
 syntactically optional.  More information is contained in the table
 following this definition.

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 fields          =   *(trace
                       *optional-field /
                       *(resent-date /
                        resent-from /
                        resent-sender /
                        resent-to /
                        resent-cc /
                        resent-bcc /
                        resent-msg-id))
                     *(orig-date /
                     from /
                     sender /
                     reply-to /
                     to /
                     cc /
                     bcc /
                     message-id /
                     in-reply-to /
                     references /
                     subject /
                     comments /
                     keywords /
                     optional-field)
 The following table indicates limits on the number of times each
 field may occur in the header section of a message as well as any
 special limitations on the use of those fields.  An asterisk ("*")
 next to a value in the minimum or maximum column indicates that a
 special restriction appears in the Notes column.

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 +----------------+--------+------------+----------------------------+
 | Field          | Min    | Max number | Notes                      |
 |                | number |            |                            |
 +----------------+--------+------------+----------------------------+
 | trace          | 0      | unlimited  | Block prepended - see      |
 |                |        |            | 3.6.7                      |
 | resent-date    | 0*     | unlimited* | One per block, required if |
 |                |        |            | other resent fields are    |
 |                |        |            | present - see 3.6.6        |
 | resent-from    | 0      | unlimited* | One per block - see 3.6.6  |
 | resent-sender  | 0*     | unlimited* | One per block, MUST occur  |
 |                |        |            | with multi-address         |
 |                |        |            | resent-from - see 3.6.6    |
 | resent-to      | 0      | unlimited* | One per block - see 3.6.6  |
 | resent-cc      | 0      | unlimited* | One per block - see 3.6.6  |
 | resent-bcc     | 0      | unlimited* | One per block - see 3.6.6  |
 | resent-msg-id  | 0      | unlimited* | One per block - see 3.6.6  |
 | orig-date      | 1      | 1          |                            |
 | from           | 1      | 1          | See sender and 3.6.2       |
 | sender         | 0*     | 1          | MUST occur with            |
 |                |        |            | multi-address from - see   |
 |                |        |            | 3.6.2                      |
 | reply-to       | 0      | 1          |                            |
 | to             | 0      | 1          |                            |
 | cc             | 0      | 1          |                            |
 | bcc            | 0      | 1          |                            |
 | message-id     | 0*     | 1          | SHOULD be present - see    |
 |                |        |            | 3.6.4                      |
 | in-reply-to    | 0*     | 1          | SHOULD occur in some       |
 |                |        |            | replies - see 3.6.4        |
 | references     | 0*     | 1          | SHOULD occur in some       |
 |                |        |            | replies - see 3.6.4        |
 | subject        | 0      | 1          |                            |
 | comments       | 0      | unlimited  |                            |
 | keywords       | 0      | unlimited  |                            |
 | optional-field | 0      | unlimited  |                            |
 +----------------+--------+------------+----------------------------+
 The exact interpretation of each field is described in subsequent
 sections.

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3.6.1. The Origination Date Field

 The origination date field consists of the field name "Date" followed
 by a date-time specification.
 orig-date       =   "Date:" date-time CRLF
 The origination date specifies the date and time at which the creator
 of the message indicated that the message was complete and ready to
 enter the mail delivery system.  For instance, this might be the time
 that a user pushes the "send" or "submit" button in an application
 program.  In any case, it is specifically not intended to convey the
 time that the message is actually transported, but rather the time at
 which the human or other creator of the message has put the message
 into its final form, ready for transport.  (For example, a portable
 computer user who is not connected to a network might queue a message
 for delivery.  The origination date is intended to contain the date
 and time that the user queued the message, not the time when the user
 connected to the network to send the message.)

3.6.2. Originator Fields

 The originator fields of a message consist of the from field, the
 sender field (when applicable), and optionally the reply-to field.
 The from field consists of the field name "From" and a comma-
 separated list of one or more mailbox specifications.  If the from
 field contains more than one mailbox specification in the mailbox-
 list, then the sender field, containing the field name "Sender" and a
 single mailbox specification, MUST appear in the message.  In either
 case, an optional reply-to field MAY also be included, which contains
 the field name "Reply-To" and a comma-separated list of one or more
 addresses.
 from            =   "From:" mailbox-list CRLF
 sender          =   "Sender:" mailbox CRLF
 reply-to        =   "Reply-To:" address-list CRLF
 The originator fields indicate the mailbox(es) of the source of the
 message.  The "From:" field specifies the author(s) of the message,
 that is, the mailbox(es) of the person(s) or system(s) responsible
 for the writing of the message.  The "Sender:" field specifies the
 mailbox of the agent responsible for the actual transmission of the
 message.  For example, if a secretary were to send a message for
 another person, the mailbox of the secretary would appear in the
 "Sender:" field and the mailbox of the actual author would appear in
 the "From:" field.  If the originator of the message can be indicated

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 by a single mailbox and the author and transmitter are identical, the
 "Sender:" field SHOULD NOT be used.  Otherwise, both fields SHOULD
 appear.
    Note: The transmitter information is always present.  The absence
    of the "Sender:" field is sometimes mistakenly taken to mean that
    the agent responsible for transmission of the message has not been
    specified.  This absence merely means that the transmitter is
    identical to the author and is therefore not redundantly placed
    into the "Sender:" field.
 The originator fields also provide the information required when
 replying to a message.  When the "Reply-To:" field is present, it
 indicates the address(es) to which the author of the message suggests
 that replies be sent.  In the absence of the "Reply-To:" field,
 replies SHOULD by default be sent to the mailbox(es) specified in the
 "From:" field unless otherwise specified by the person composing the
 reply.
 In all cases, the "From:" field SHOULD NOT contain any mailbox that
 does not belong to the author(s) of the message.  See also section
 3.6.3 for more information on forming the destination addresses for a
 reply.

3.6.3. Destination Address Fields

 The destination fields of a message consist of three possible fields,
 each of the same form: the field name, which is either "To", "Cc", or
 "Bcc", followed by a comma-separated list of one or more addresses
 (either mailbox or group syntax).
 to              =   "To:" address-list CRLF
 cc              =   "Cc:" address-list CRLF
 bcc             =   "Bcc:" [address-list / CFWS] CRLF
 The destination fields specify the recipients of the message.  Each
 destination field may have one or more addresses, and the addresses
 indicate the intended recipients of the message.  The only difference
 between the three fields is how each is used.
 The "To:" field contains the address(es) of the primary recipient(s)
 of the message.

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 The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
 making a copy on a typewriter using carbon paper) contains the
 addresses of others who are to receive the message, though the
 content of the message may not be directed at them.
 The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
 addresses of recipients of the message whose addresses are not to be
 revealed to other recipients of the message.  There are three ways in
 which the "Bcc:" field is used.  In the first case, when a message
 containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
 removed even though all of the recipients (including those specified
 in the "Bcc:" field) are sent a copy of the message.  In the second
 case, recipients specified in the "To:" and "Cc:" lines each are sent
 a copy of the message with the "Bcc:" line removed as above, but the
 recipients on the "Bcc:" line get a separate copy of the message
 containing a "Bcc:" line.  (When there are multiple recipient
 addresses in the "Bcc:" field, some implementations actually send a
 separate copy of the message to each recipient with a "Bcc:"
 containing only the address of that particular recipient.)  Finally,
 since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
 sent without any addresses indicating to the recipients that blind
 copies were sent to someone.  Which method to use with "Bcc:" fields
 is implementation dependent, but refer to the "Security
 Considerations" section of this document for a discussion of each.
 When a message is a reply to another message, the mailboxes of the
 authors of the original message (the mailboxes in the "From:" field)
 or mailboxes specified in the "Reply-To:" field (if it exists) MAY
 appear in the "To:" field of the reply since these would normally be
 the primary recipients of the reply.  If a reply is sent to a message
 that has destination fields, it is often desirable to send a copy of
 the reply to all of the recipients of the message, in addition to the
 author.  When such a reply is formed, addresses in the "To:" and
 "Cc:" fields of the original message MAY appear in the "Cc:" field of
 the reply, since these are normally secondary recipients of the
 reply.  If a "Bcc:" field is present in the original message,
 addresses in that field MAY appear in the "Bcc:" field of the reply,
 but they SHOULD NOT appear in the "To:" or "Cc:" fields.
    Note: Some mail applications have automatic reply commands that
    include the destination addresses of the original message in the
    destination addresses of the reply.  How those reply commands
    behave is implementation dependent and is beyond the scope of this
    document.  In particular, whether or not to include the original
    destination addresses when the original message had a "Reply-To:"
    field is not addressed here.

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3.6.4. Identification Fields

 Though listed as optional in the table in section 3.6, every message
 SHOULD have a "Message-ID:" field.  Furthermore, reply messages
 SHOULD have "In-Reply-To:" and "References:" fields as appropriate
 and as described below.
 The "Message-ID:" field contains a single unique message identifier.
 The "References:" and "In-Reply-To:" fields each contain one or more
 unique message identifiers, optionally separated by CFWS.
 The message identifier (msg-id) syntax is a limited version of the
 addr-spec construct enclosed in the angle bracket characters, "<" and
 ">".  Unlike addr-spec, this syntax only permits the dot-atom-text
 form on the left-hand side of the "@" and does not have internal CFWS
 anywhere in the message identifier.
    Note: As with addr-spec, a liberal syntax is given for the right-
    hand side of the "@" in a msg-id.  However, later in this section,
    the use of a domain for the right-hand side of the "@" is
    RECOMMENDED.  Again, the syntax of domain constructs is specified
    by and used in other protocols (e.g., [RFC1034], [RFC1035],
    [RFC1123], [RFC5321]).  It is therefore incumbent upon
    implementations to conform to the syntax of addresses for the
    context in which they are used.
 message-id      =   "Message-ID:" msg-id CRLF
 in-reply-to     =   "In-Reply-To:" 1*msg-id CRLF
 references      =   "References:" 1*msg-id CRLF
 msg-id          =   [CFWS] "<" id-left "@" id-right ">" [CFWS]
 id-left         =   dot-atom-text / obs-id-left
 id-right        =   dot-atom-text / no-fold-literal / obs-id-right
 no-fold-literal =   "[" *dtext "]"
 The "Message-ID:" field provides a unique message identifier that
 refers to a particular version of a particular message.  The
 uniqueness of the message identifier is guaranteed by the host that
 generates it (see below).  This message identifier is intended to be
 machine readable and not necessarily meaningful to humans.  A message
 identifier pertains to exactly one version of a particular message;
 subsequent revisions to the message each receive new message
 identifiers.

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.

Resnick Standards Track [Page 26] 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

Resnick Standards Track [Page 27] RFC 5322 Internet Message Format October 2008

 message.  When used in a reply, the field body MAY start with the
 string "Re: " (an abbreviation of the Latin "in re", meaning "in the
 matter of") followed by the contents of the "Subject:" field body of
 the original message.  If this is done, only one instance of the
 literal string "Re: " ought to be used since use of other strings or
 more than one instance can lead to undesirable consequences.  The
 "Comments:" field contains any additional comments on the text of the
 body of the message.  The "Keywords:" field contains a comma-
 separated list of important words and phrases that might be useful
 for the recipient.

3.6.6. Resent Fields

 Resent fields SHOULD be added to any message that is reintroduced by
 a user into the transport system.  A separate set of resent fields
 SHOULD be added each time this is done.  All of the resent fields
 corresponding to a particular resending of the message SHOULD be
 grouped together.  Each new set of resent fields is prepended to the
 message; that is, the most recent set of resent fields appears
 earlier in the message.  No other fields in the message are changed
 when resent fields are added.
 Each of the resent fields corresponds to a particular field elsewhere
 in the syntax.  For instance, the "Resent-Date:" field corresponds to
 the "Date:" field and the "Resent-To:" field corresponds to the "To:"
 field.  In each case, the syntax for the field body is identical to
 the syntax given previously for the corresponding field.
 When resent fields are used, the "Resent-From:" and "Resent-Date:"
 fields MUST be sent.  The "Resent-Message-ID:" field SHOULD be sent.
 "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
 identical to "Resent-From:".
 resent-date     =   "Resent-Date:" date-time CRLF
 resent-from     =   "Resent-From:" mailbox-list CRLF
 resent-sender   =   "Resent-Sender:" mailbox CRLF
 resent-to       =   "Resent-To:" address-list CRLF
 resent-cc       =   "Resent-Cc:" address-list CRLF
 resent-bcc      =   "Resent-Bcc:" [address-list / CFWS] CRLF
 resent-msg-id   =   "Resent-Message-ID:" msg-id CRLF

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 Resent fields are used to identify a message as having been
 reintroduced into the transport system by a user.  The purpose of
 using resent fields is to have the message appear to the final
 recipient as if it were sent directly by the original sender, with
 all of the original fields remaining the same.  Each set of resent
 fields correspond to a particular resending event.  That is, if a
 message is resent multiple times, each set of resent fields gives
 identifying information for each individual time.  Resent fields are
 strictly informational.  They MUST NOT be used in the normal
 processing of replies or other such automatic actions on messages.
    Note: Reintroducing a message into the transport system and using
    resent fields is a different operation from "forwarding".
    "Forwarding" has two meanings: One sense of forwarding is that a
    mail reading program can be told by a user to forward a copy of a
    message to another person, making the forwarded message the body
    of the new message.  A forwarded message in this sense does not
    appear to have come from the original sender, but is an entirely
    new message from the forwarder of the message.  Forwarding may
    also mean that a mail transport program gets a message and
    forwards it on to a different destination for final delivery.
    Resent header fields are not intended for use with either type of
    forwarding.
 The resent originator fields indicate the mailbox of the person(s) or
 system(s) that resent the message.  As with the regular originator
 fields, there are two forms: a simple "Resent-From:" form, which
 contains the mailbox of the individual doing the resending, and the
 more complex form, when one individual (identified in the "Resent-
 Sender:" field) resends a message on behalf of one or more others
 (identified in the "Resent-From:" field).
    Note: When replying to a resent message, replies behave just as
    they would with any other message, using the original "From:",
    "Reply-To:", "Message-ID:", and other fields.  The resent fields
    are only informational and MUST NOT be used in the normal
    processing of replies.
 The "Resent-Date:" indicates the date and time at which the resent
 message is dispatched by the resender of the message.  Like the
 "Date:" field, it is not the date and time that the message was
 actually transported.
 The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
 identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
 except that they indicate the recipients of the resent message, not
 the recipients of the original message.

Resnick Standards Track [Page 29] RFC 5322 Internet Message Format October 2008

 The "Resent-Message-ID:" field provides a unique identifier for the
 resent message.

3.6.7. Trace Fields

 The trace fields are a group of header fields consisting of an
 optional "Return-Path:" field, and one or more "Received:" fields.
 The "Return-Path:" header field contains a pair of angle brackets
 that enclose an optional addr-spec.  The "Received:" field contains a
 (possibly empty) list of tokens followed by a semicolon and a date-
 time specification.  Each token must be a word, angle-addr, addr-
 spec, or a domain.  Further restrictions are applied to the syntax of
 the trace fields by specifications that provide for their use, such
 as [RFC5321].
 trace           =   [return]
                     1*received
 return          =   "Return-Path:" path CRLF
 path            =   angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
 received        =   "Received:" *received-token ";" date-time CRLF
 received-token  =   word / angle-addr / addr-spec / domain
 A full discussion of the Internet mail use of trace fields is
 contained in [RFC5321].  For the purposes of this specification, the
 trace fields are strictly informational, and any formal
 interpretation of them is outside of the scope of this document.

3.6.8. Optional Fields

 Fields may appear in messages that are otherwise unspecified in this
 document.  They MUST conform to the syntax of an optional-field.
 This is a field name, made up of the printable US-ASCII characters
 except SP and colon, followed by a colon, followed by any text that
 conforms to the unstructured syntax.
 The field names of any optional field MUST NOT be identical to any
 field name specified elsewhere in this document.

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 optional-field  =   field-name ":" unstructured CRLF
 field-name      =   1*ftext
 ftext           =   %d33-57 /          ; Printable US-ASCII
                     %d59-126           ;  characters not including
                                        ;  ":".
 For the purposes of this specification, any optional field is
 uninterpreted.

4. Obsolete Syntax

 Earlier versions of this specification allowed for different (usually
 more liberal) syntax than is allowed in this version.  Also, there
 have been syntactic elements used in messages on the Internet whose
 interpretations have never been documented.  Though these syntactic
 forms MUST NOT be generated according to the grammar in section 3,
 they MUST be accepted and parsed by a conformant receiver.  This
 section documents many of these syntactic elements.  Taking the
 grammar in section 3 and adding the definitions presented in this
 section will result in the grammar to use for the interpretation of
 messages.
    Note: This section identifies syntactic forms that any
    implementation MUST reasonably interpret.  However, there are
    certainly Internet messages that do not conform to even the
    additional syntax given in this section.  The fact that a
    particular form does not appear in any section of this document is
    not justification for computer programs to crash or for malformed
    data to be irretrievably lost by any implementation.  It is up to
    the implementation to deal with messages robustly.
 One important difference between the obsolete (interpreting) and the
 current (generating) syntax is that in structured header field bodies
 (i.e., between the colon and the CRLF of any structured header
 field), white space characters, including folding white space, and
 comments could be freely inserted between any syntactic tokens.  This
 allowed many complex forms that have proven difficult for some
 implementations to parse.
 Another key difference between the obsolete and the current syntax is
 that the rule in section 3.2.2 regarding lines composed entirely of
 white space in comments and folding white space does not apply.  See
 the discussion of folding white space in section 4.2 below.
 Finally, certain characters that were formerly allowed in messages
 appear in this section.  The NUL character (ASCII value 0) was once

Resnick Standards Track [Page 31] RFC 5322 Internet Message Format October 2008

 allowed, but is no longer for compatibility reasons.  Similarly, US-
 ASCII control characters other than CR, LF, SP, and HTAB (ASCII
 values 1 through 8, 11, 12, 14 through 31, and 127) were allowed to
 appear in header field bodies.  CR and LF were allowed to appear in
 messages other than as CRLF; this use is also shown here.
 Other differences in syntax and semantics are noted in the following
 sections.

4.1. Miscellaneous Obsolete Tokens

 These syntactic elements are used elsewhere in the obsolete syntax or
 in the main syntax.  Bare CR, bare LF, and NUL are added to obs-qp,
 obs-body, and obs-unstruct.  US-ASCII control characters are added to
 obs-qp, obs-unstruct, obs-ctext, and obs-qtext.  The period character
 is added to obs-phrase.  The obs-phrase-list provides for a
 (potentially empty) comma-separated list of phrases that may include
 "null" elements.  That is, there could be two or more commas in such
 a list with nothing in between them, or commas at the beginning or
 end of the list.
    Note: The "period" (or "full stop") character (".") in obs-phrase
    is not a form that was allowed in earlier versions of this or any
    other specification.  Period (nor any other character from
    specials) was not allowed in phrase because it introduced a
    parsing difficulty distinguishing between phrases and portions of
    an addr-spec (see section 4.4).  It appears here because the
    period character is currently used in many messages in the
    display-name portion of addresses, especially for initials in
    names, and therefore must be interpreted properly.
 obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
                     %d11 /             ;  characters that do not
                     %d12 /             ;  include the carriage
                     %d14-31 /          ;  return, line feed, and
                     %d127              ;  white space characters
 obs-ctext       =   obs-NO-WS-CTL
 obs-qtext       =   obs-NO-WS-CTL
 obs-utext       =   %d0 / obs-NO-WS-CTL / VCHAR
 obs-qp          =   "\" (%d0 / obs-NO-WS-CTL / LF / CR)
 obs-body        =   *((*LF *CR *((%d0 / text) *LF *CR)) / CRLF)
 obs-unstruct    =   *((*LF *CR *(obs-utext *LF *CR)) / FWS)

Resnick Standards Track [Page 32] RFC 5322 Internet Message Format October 2008

 obs-phrase      =   word *(word / "." / CFWS)
 obs-phrase-list =   [phrase / CFWS] *("," [phrase / CFWS])
 Bare CR and bare LF appear in messages with two different meanings.
 In many cases, bare CR or bare LF are used improperly instead of CRLF
 to indicate line separators.  In other cases, bare CR and bare LF are
 used simply as US-ASCII control characters with their traditional
 ASCII meanings.

4.2. Obsolete Folding White Space

 In the obsolete syntax, any amount of folding white space MAY be
 inserted where the obs-FWS rule is allowed.  This creates the
 possibility of having two consecutive "folds" in a line, and
 therefore the possibility that a line which makes up a folded header
 field could be composed entirely of white space.
 obs-FWS         =   1*WSP *(CRLF 1*WSP)

4.3. Obsolete Date and Time

 The syntax for the obsolete date format allows a 2 digit year in the
 date field and allows for a list of alphabetic time zone specifiers
 that were used in earlier versions of this specification.  It also
 permits comments and folding white space between many of the tokens.
 obs-day-of-week =   [CFWS] day-name [CFWS]
 obs-day         =   [CFWS] 1*2DIGIT [CFWS]
 obs-year        =   [CFWS] 2*DIGIT [CFWS]
 obs-hour        =   [CFWS] 2DIGIT [CFWS]
 obs-minute      =   [CFWS] 2DIGIT [CFWS]
 obs-second      =   [CFWS] 2DIGIT [CFWS]
 obs-zone        =   "UT" / "GMT" /     ; Universal Time
                                        ; North American UT
                                        ; offsets
                     "EST" / "EDT" /    ; Eastern:  - 5/ - 4
                     "CST" / "CDT" /    ; Central:  - 6/ - 5
                     "MST" / "MDT" /    ; Mountain: - 7/ - 6
                     "PST" / "PDT" /    ; Pacific:  - 8/ - 7
                                        ;

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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.

Resnick Standards Track [Page 35] RFC 5322 Internet Message Format October 2008

 obs-fields      =   *(obs-return /
                     obs-received /
                     obs-orig-date /
                     obs-from /
                     obs-sender /
                     obs-reply-to /
                     obs-to /
                     obs-cc /
                     obs-bcc /
                     obs-message-id /
                     obs-in-reply-to /
                     obs-references /
                     obs-subject /
                     obs-comments /
                     obs-keywords /
                     obs-resent-date /
                     obs-resent-from /
                     obs-resent-send /
                     obs-resent-rply /
                     obs-resent-to /
                     obs-resent-cc /
                     obs-resent-bcc /
                     obs-resent-mid /
                     obs-optional)
 Except for destination address fields (described in section 4.5.3),
 the interpretation of multiple occurrences of fields is unspecified.
 Also, the interpretation of trace fields and resent fields that do
 not occur in blocks prepended to the message is unspecified as well.
 Unless otherwise noted in the following sections, interpretation of
 other fields is identical to the interpretation of their non-obsolete
 counterparts in section 3.

4.5.1. Obsolete Origination Date Field

 obs-orig-date   =   "Date" *WSP ":" date-time CRLF

4.5.2. Obsolete Originator Fields

 obs-from        =   "From" *WSP ":" mailbox-list CRLF
 obs-sender      =   "Sender" *WSP ":" mailbox CRLF
 obs-reply-to    =   "Reply-To" *WSP ":" address-list CRLF

Resnick Standards Track [Page 36] RFC 5322 Internet Message Format October 2008

4.5.3. Obsolete Destination Address Fields

 obs-to          =   "To" *WSP ":" address-list CRLF
 obs-cc          =   "Cc" *WSP ":" address-list CRLF
 obs-bcc         =   "Bcc" *WSP ":"
                     (address-list / (*([CFWS] ",") [CFWS])) CRLF
 When multiple occurrences of destination address fields occur in a
 message, they SHOULD be treated as if the address list in the first
 occurrence of the field is combined with the address lists of the
 subsequent occurrences by adding a comma and concatenating.

4.5.4. Obsolete Identification Fields

 The obsolete "In-Reply-To:" and "References:" fields differ from the
 current syntax in that they allow phrase (words or quoted strings) to
 appear.  The obsolete forms of the left and right sides of msg-id
 allow interspersed CFWS, making them syntactically identical to
 local-part and domain, respectively.
 obs-message-id  =   "Message-ID" *WSP ":" msg-id CRLF
 obs-in-reply-to =   "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
 obs-references  =   "References" *WSP ":" *(phrase / msg-id) CRLF
 obs-id-left     =   local-part
 obs-id-right    =   domain
 For purposes of interpretation, the phrases in the "In-Reply-To:" and
 "References:" fields are ignored.
 Semantically, none of the optional CFWS in the local-part and the
 domain is part of the obs-id-left and obs-id-right, respectively.

4.5.5. Obsolete Informational Fields

 obs-subject     =   "Subject" *WSP ":" unstructured CRLF
 obs-comments    =   "Comments" *WSP ":" unstructured CRLF
 obs-keywords    =   "Keywords" *WSP ":" obs-phrase-list CRLF

Resnick Standards Track [Page 37] RFC 5322 Internet Message Format October 2008

4.5.6. Obsolete Resent Fields

 The obsolete syntax adds a "Resent-Reply-To:" field, which consists
 of the field name, the optional comments and folding white space, the
 colon, and a comma separated list of addresses.
 obs-resent-from =   "Resent-From" *WSP ":" mailbox-list CRLF
 obs-resent-send =   "Resent-Sender" *WSP ":" mailbox CRLF
 obs-resent-date =   "Resent-Date" *WSP ":" date-time CRLF
 obs-resent-to   =   "Resent-To" *WSP ":" address-list CRLF
 obs-resent-cc   =   "Resent-Cc" *WSP ":" address-list CRLF
 obs-resent-bcc  =   "Resent-Bcc" *WSP ":"
                     (address-list / (*([CFWS] ",") [CFWS])) CRLF
 obs-resent-mid  =   "Resent-Message-ID" *WSP ":" msg-id CRLF
 obs-resent-rply =   "Resent-Reply-To" *WSP ":" address-list CRLF
 As with other resent fields, the "Resent-Reply-To:" field is to be
 treated as trace information only.

4.5.7. Obsolete Trace Fields

 The obs-return and obs-received are again given here as template
 definitions, just as return and received are in section 3.  Their
 full syntax is given in [RFC5321].
 obs-return      =   "Return-Path" *WSP ":" path CRLF
 obs-received    =   "Received" *WSP ":" *received-token CRLF

4.5.8. Obsolete optional fields

 obs-optional    =   field-name *WSP ":" unstructured CRLF

5. Security Considerations

 Care needs to be taken when displaying messages on a terminal or
 terminal emulator.  Powerful terminals may act on escape sequences
 and other combinations of US-ASCII control characters with a variety
 of consequences.  They can remap the keyboard or permit other
 modifications to the terminal that could lead to denial of service or
 even damaged data.  They can trigger (sometimes programmable)

Resnick Standards Track [Page 38] RFC 5322 Internet Message Format October 2008

 answerback messages that can allow a message to cause commands to be
 issued on the recipient's behalf.  They can also affect the operation
 of terminal attached devices such as printers.  Message viewers may
 wish to strip potentially dangerous terminal escape sequences from
 the message prior to display.  However, other escape sequences appear
 in messages for useful purposes (cf. [ISO.2022.1994], [RFC2045],
 [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]) and therefore
 should not be stripped indiscriminately.
 Transmission of non-text objects in messages raises additional
 security issues.  These issues are discussed in [RFC2045], [RFC2046],
 [RFC2047], [RFC2049], [RFC4288], and [RFC4289].
 Many implementations use the "Bcc:" (blind carbon copy) field,
 described in section 3.6.3, to facilitate sending messages to
 recipients without revealing the addresses of one or more of the
 addressees to the other recipients.  Mishandling this use of "Bcc:"
 may disclose confidential information that could eventually lead to
 security problems through knowledge of even the existence of a
 particular mail address.  For example, if using the first method
 described in section 3.6.3, where the "Bcc:" line is removed from the
 message, blind recipients have no explicit indication that they have
 been sent a blind copy, except insofar as their address does not
 appear in the header section of a message.  Because of this, one of
 the blind addressees could potentially send a reply to all of the
 shown recipients and accidentally reveal that the message went to the
 blind recipient.  When the second method from section 3.6.3 is used,
 the blind recipient's address appears in the "Bcc:" field of a
 separate copy of the message.  If the "Bcc:" field sent contains all
 of the blind addressees, all of the "Bcc:" recipients will be seen by
 each "Bcc:" recipient.  Even if a separate message is sent to each
 "Bcc:" recipient with only the individual's address, implementations
 still need to be careful to process replies to the message as per
 section 3.6.3 so as not to accidentally reveal the blind recipient to
 other recipients.

6. IANA Considerations

 This document updates the registrations that appeared in [RFC4021]
 that referred to the definitions in [RFC2822].  IANA has updated the
 Permanent Message Header Field Repository with the following header
 fields, in accordance with the procedures set out in [RFC3864].
 Header field name:  Date
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.1)

Resnick Standards Track [Page 39] RFC 5322 Internet Message Format October 2008

 Header field name:  From
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.2)
 Header field name:  Sender
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.2)
 Header field name:  Reply-To
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.2)
 Header field name:  To
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.3)
 Header field name:  Cc
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.3)
 Header field name:  Bcc
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.3)
 Header field name:  Message-ID
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.4)
 Header field name:  In-Reply-To
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.4)

Resnick Standards Track [Page 40] RFC 5322 Internet Message Format October 2008

 Header field name:  References
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.4)
 Header field name:  Subject
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.5)
 Header field name:  Comments
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.5)
 Header field name:  Keywords
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.5)
 Header field name:  Resent-Date
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Resent-From
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Resent-Sender
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Resent-To
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)

Resnick Standards Track [Page 41] RFC 5322 Internet Message Format October 2008

 Header field name:  Resent-Cc
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Resent-Bcc
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Resent-Reply-To
 Applicable protocol:  Mail
 Status:  obsolete
 Author/Change controller:  IETF
 Specification document(s):  This document (section 4.5.6)
 Header field name:  Resent-Message-ID
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.6)
 Header field name:  Return-Path
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.7)
 Header field name:  Received
 Applicable protocol:  Mail
 Status:  standard
 Author/Change controller:  IETF
 Specification document(s):  This document (section 3.6.7)
 Related information:  [RFC5321]

Resnick Standards Track [Page 42] RFC 5322 Internet Message Format October 2008

Appendix A. Example Messages

 This section presents a selection of messages.  These are intended to
 assist in the implementation of this specification, but should not be
 taken as normative; that is to say, although the examples in this
 section were carefully reviewed, if there happens to be a conflict
 between these examples and the syntax described in sections 3 and 4
 of this document, the syntax in those sections is to be taken as
 correct.
 In the text version of this document, messages in this section are
 delimited between lines of "----".  The "----" lines are not part of
 the message itself.

Resnick Standards Track [Page 43] RFC 5322 Internet Message Format October 2008

Appendix A.1. Addressing Examples

 The following are examples of messages that might be sent between two
 individuals.

Appendix A.1.1. A Message from One Person to Another with Simple

               Addressing
 This could be called a canonical message.  It has a single author,
 John Doe, a single recipient, Mary Smith, a subject, the date, a
 message identifier, and a textual message in the body.

From: John Doe jdoe@machine.example

 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----
 If John's secretary Michael actually sent the message, even though
 John was the author and replies to this message should go back to
 him, the sender field would be used:

From: John Doe jdoe@machine.example

 Sender: Michael Jones <mjones@machine.example>
 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----

Resnick Standards Track [Page 44] RFC 5322 Internet Message Format October 2008

Appendix A.1.2. Different Types of Mailboxes

 This message includes multiple addresses in the destination fields
 and also uses several different forms of addresses.

From: "Joe Q. Public" john.q.public@example.com

 To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
 Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
 Date: Tue, 1 Jul 2003 10:52:37 +0200
 Message-ID: <5678.21-Nov-1997@example.com>
 Hi everyone.
 ----
 Note that the display names for Joe Q. Public and Giant; "Big" Box
 needed to be enclosed in double-quotes because the former contains
 the period and the latter contains both semicolon and double-quote
 characters (the double-quote characters appearing as quoted-pair
 constructs).  Conversely, the display name for Who? could appear
 without them because the question mark is legal in an atom.  Notice
 also that jdoe@example.org and boss@nil.test have no display names
 associated with them at all, and jdoe@example.org uses the simpler
 address form without the angle brackets.

Appendix A.1.3. Group Addresses

From: Pete pete@silly.example

 To: A Group:Ed Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
 Cc: Undisclosed recipients:;
 Date: Thu, 13 Feb 1969 23:32:54 -0330
 Message-ID: <testabcd.1234@silly.example>
 Testing.
 ----
 In this message, the "To:" field has a single group recipient named
 "A Group", which contains 3 addresses, and a "Cc:" field with an
 empty group recipient named Undisclosed recipients.

Resnick Standards Track [Page 45] RFC 5322 Internet Message Format October 2008

Appendix A.2. Reply Messages

 The following is a series of three messages that make up a
 conversation thread between John and Mary.  John first sends a
 message to Mary, Mary then replies to John's message, and then John
 replies to Mary's reply message.
 Note especially the "Message-ID:", "References:", and "In-Reply-To:"
 fields in each message.

From: John Doe jdoe@machine.example

 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----
 When sending replies, the Subject field is often retained, though
 prepended with "Re: " as described in section 3.6.5.

From: Mary Smith mary@example.net

 To: John Doe <jdoe@machine.example>
 Reply-To: "Mary Smith: Personal Account" <smith@home.example>
 Subject: Re: Saying Hello
 Date: Fri, 21 Nov 1997 10:01:10 -0600
 Message-ID: <3456@example.net>
 In-Reply-To: <1234@local.machine.example>
 References: <1234@local.machine.example>
 This is a reply to your hello.
 ----
 Note the "Reply-To:" field in the above message.  When John replies
 to Mary's message above, the reply should go to the address in the
 "Reply-To:" field instead of the address in the "From:" field.

Resnick Standards Track [Page 46] RFC 5322 Internet Message Format October 2008

To: "Mary Smith: Personal Account" smith@home.example

 From: John Doe <jdoe@machine.example>
 Subject: Re: Saying Hello
 Date: Fri, 21 Nov 1997 11:00:00 -0600
 Message-ID: <abcd.1234@local.machine.test>
 In-Reply-To: <3456@example.net>
 References: <1234@local.machine.example> <3456@example.net>
 This is a reply to your reply.
 ----

Appendix A.3. Resent Messages

 Start with the message that has been used as an example several
 times:

From: John Doe jdoe@machine.example

 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----
 Say that Mary, upon receiving this message, wishes to send a copy of
 the message to Jane such that (a) the message would appear to have
 come straight from John; (b) if Jane replies to the message, the
 reply should go back to John; and (c) all of the original
 information, like the date the message was originally sent to Mary,
 the message identifier, and the original addressee, is preserved.  In
 this case, resent fields are prepended to the message:

Resnick Standards Track [Page 47] RFC 5322 Internet Message Format October 2008

Resent-From: Mary Smith mary@example.net

 Resent-To: Jane Brown <j-brown@other.example>
 Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
 Resent-Message-ID: <78910@example.net>
 From: John Doe <jdoe@machine.example>
 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----
 If Jane, in turn, wished to resend this message to another person,
 she would prepend her own set of resent header fields to the above
 and send that.  (Note that for brevity, trace fields are not shown.)

Appendix A.4. Messages with Trace Fields

 As messages are sent through the transport system as described in
 [RFC5321], trace fields are prepended to the message.  The following
 is an example of what those trace fields might look like.  Note that
 there is some folding white space in the first one since these lines
 can be long.

Received: from x.y.test

    by example.net
    via TCP
    with ESMTP
    id ABC12345
    for <mary@example.net>;  21 Nov 1997 10:05:43 -0600
 Received: from node.example by x.y.test; 21 Nov 1997 10:01:22 -0600
 From: John Doe <jdoe@node.example>
 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: Fri, 21 Nov 1997 09:55:06 -0600
 Message-ID: <1234@local.node.example>
 This is a message just to say hello.
 So, "Hello".
 ----

Resnick Standards Track [Page 48] RFC 5322 Internet Message Format October 2008

Appendix A.5. White Space, Comments, and Other Oddities

 White space, including folding white space, and comments can be
 inserted between many of the tokens of fields.  Taking the example
 from A.1.3, white space and comments can be inserted into all of the
 fields.

From: Pete(A nice \) chap) <pete(his account)@silly.test(his host)>

 To:A Group(Some people)
      :Chris Jones <c@(Chris's host.)public.example>,
          joe@example.org,
   John <jdoe@one.test> (my dear friend); (the end of the group)
 Cc:(Empty list)(start)Hidden recipients  :(nobody(that I know))  ;
 Date: Thu,
       13
         Feb
           1969
       23:32
                -0330 (Newfoundland Time)
 Message-ID:              <testabcd.1234@silly.test>
 Testing.
 ----
 The above example is aesthetically displeasing, but perfectly legal.
 Note particularly (1) the comments in the "From:" field (including
 one that has a ")" character appearing as part of a quoted-pair); (2)
 the white space absent after the ":" in the "To:" field as well as
 the comment and folding white space after the group name, the special
 character (".") in the comment in Chris Jones's address, and the
 folding white space before and after "joe@example.org,"; (3) the
 multiple and nested comments in the "Cc:" field as well as the
 comment immediately following the ":" after "Cc"; (4) the folding
 white space (but no comments except at the end) and the missing
 seconds in the time of the date field; and (5) the white space before
 (but not within) the identifier in the "Message-ID:" field.

Resnick Standards Track [Page 49] RFC 5322 Internet Message Format October 2008

Appendix A.6. Obsoleted Forms

 The following are examples of obsolete (that is, the "MUST NOT
 generate") syntactic elements described in section 4 of this
 document.

Appendix A.6.1. Obsolete Addressing

 Note in the example below the lack of quotes around Joe Q. Public,
 the route that appears in the address for Mary Smith, the two commas
 that appear in the "To:" field, and the spaces that appear around the
 "." in the jdoe address.

From: Joe Q. Public john.q.public@example.com

 To: Mary Smith <@node.test:mary@example.net>, , jdoe@test  . example
 Date: Tue, 1 Jul 2003 10:52:37 +0200
 Message-ID: <5678.21-Nov-1997@example.com>
 Hi everyone.
 ----

Appendix A.6.2. Obsolete Dates

 The following message uses an obsolete date format, including a non-
 numeric time zone and a two digit year.  Note that although the day-
 of-week is missing, that is not specific to the obsolete syntax; it
 is optional in the current syntax as well.

From: John Doe jdoe@machine.example

 To: Mary Smith <mary@example.net>
 Subject: Saying Hello
 Date: 21 Nov 97 09:55:06 GMT
 Message-ID: <1234@local.machine.example>
 This is a message just to say hello.
 So, "Hello".
 ----

Resnick Standards Track [Page 50] RFC 5322 Internet Message Format October 2008

Appendix A.6.3. Obsolete White Space and Comments

 White space and comments can appear between many more elements than
 in the current syntax.  Also, folding lines that are made up entirely
 of white space are legal.

From : John Doe <jdoe@machine(comment). example>

 To    : Mary Smith
 __
           <mary@example.net>
 Subject     : Saying Hello
 Date  : Fri, 21 Nov 1997 09(comment):   55  :  06 -0600
 Message-ID  : <1234   @   local(blah)  .machine .example>
 This is a message just to say hello.
 So, "Hello".
 ----
 Note especially the second line of the "To:" field.  It starts with
 two space characters.  (Note that "__" represent blank spaces.)
 Therefore, it is considered part of the folding, as described in
 section 4.2.  Also, the comments and white space throughout
 addresses, dates, and message identifiers are all part of the
 obsolete syntax.

Resnick Standards Track [Page 51] RFC 5322 Internet Message Format October 2008

Appendix B. Differences from Earlier Specifications

 This appendix contains a list of changes that have been made in the
 Internet Message Format from earlier specifications, specifically
 [RFC0822], [RFC1123], and [RFC2822].  Items marked with an asterisk
 (*) below are items which appear in section 4 of this document and
 therefore can no longer be generated.
 The following are the changes made from [RFC0822] and [RFC1123] to
 [RFC2822] that remain in this document:
 1.   Period allowed in obsolete form of phrase.
 2.   ABNF moved out of document, now in [RFC5234].
 3.   Four or more digits allowed for year.
 4.   Header field ordering (and lack thereof) made explicit.
 5.   Encrypted header field removed.
 6.   Specifically allow and give meaning to "-0000" time zone.
 7.   Folding white space is not allowed between every token.
 8.   Requirement for destinations removed.
 9.   Forwarding and resending redefined.
 10.  Extension header fields no longer specifically called out.
 11.  ASCII 0 (null) removed.*
 12.  Folding continuation lines cannot contain only white space.*
 13.  Free insertion of comments not allowed in date.*
 14.  Non-numeric time zones not allowed.*
 15.  Two digit years not allowed.*
 16.  Three digit years interpreted, but not allowed for generation.*
 17.  Routes in addresses not allowed.*
 18.  CFWS within local-parts and domains not allowed.*
 19.  Empty members of address lists not allowed.*
 20.  Folding white space between field name and colon not allowed.*
 21.  Comments between field name and colon not allowed.
 22.  Tightened syntax of in-reply-to and references.*
 23.  CFWS within msg-id not allowed.*
 24.  Tightened semantics of resent fields as informational only.
 25.  Resent-Reply-To not allowed.*
 26.  No multiple occurrences of fields (except resent and received).*
 27.  Free CR and LF not allowed.*
 28.  Line length limits specified.
 29.  Bcc more clearly specified.

Resnick Standards Track [Page 52] RFC 5322 Internet Message Format October 2008

 The following are changes from [RFC2822].
 1.   Assorted typographical/grammatical errors fixed and
      clarifications made.
 2.   Changed "standard" to "document" or "specification" throughout.
 3.   Made distinction between "header field" and "header section".
 4.   Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
 5.   Moved discussion of specials to the "Atom" section.  Moved text
      to "Overall message syntax" section.
 6.   Simplified CFWS syntax.
 7.   Fixed unstructured syntax.
 8.   Changed date and time syntax to deal with white space in
      obsolete date syntax.
 9.   Removed quoted-pair from domain literals and message
      identifiers.*
 10.  Clarified that other specifications limit domain syntax.
 11.  Simplified "Bcc:" and "Resent-Bcc:" syntax.
 12.  Allowed optional-field to appear within trace information.
 13.  Removed no-fold-quote from msg-id.  Clarified syntax
      limitations.
 14.  Generalized "Received:" syntax to fix bugs and move definition
      out of this document.
 15.  Simplified obs-qp.  Fixed and simplified obs-utext (which now
      only appears in the obsolete syntax).  Removed obs-text and obs-
      char, adding obs-body.
 16.  Fixed obsolete date syntax to allow for more (or less) comments
      and white space.
 17.  Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list,
      obs-addr-list, obs-phrase-list, and the newly added obs-group-
      list).
 18.  Fixed obs-reply-to syntax.
 19.  Fixed obs-bcc and obs-resent-bcc to allow empty lists.
 20.  Removed obs-path.

Appendix C. Acknowledgements

 Many people contributed to this document.  They included folks who
 participated in the Detailed Revision and Update of Messaging
 Standards (DRUMS) Working Group of the Internet Engineering Task
 Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
 people who simply sent their comments in via email.  The editor is
 deeply indebted to them all and thanks them sincerely.  The below
 list includes everyone who sent email concerning both this document
 and [RFC2822].  Hopefully, everyone who contributed is named here:
 +--------------------+----------------------+---------------------+
 | Matti Aarnio       | Tanaka Akira         | Russ Allbery        |
 | Eric Allman        | Harald Alvestrand    | Ran Atkinson        |
 | Jos Backus         | Bruce Balden         | Dave Barr           |

Resnick Standards Track [Page 53] RFC 5322 Internet Message Format October 2008

 | Alan Barrett       | John Beck            | J Robert von Behren |
 | Jos den Bekker     | D J Bernstein        | James Berriman      |
 | Oliver Block       | Norbert Bollow       | Raj Bose            |
 | Antony Bowesman    | Scott Bradner        | Randy Bush          |
 | Tom Byrer          | Bruce Campbell       | Larry Campbell      |
 | W J Carpenter      | Michael Chapman      | Richard Clayton     |
 | Maurizio Codogno   | Jim Conklin          | R Kelley Cook       |
 | Nathan Coulter     | Steve Coya           | Mark Crispin        |
 | Dave Crocker       | Matt Curtin          | Michael D'Errico    |
 | Cyrus Daboo        | Michael D Dean       | Jutta Degener       |
 | Mark Delany        | Steve Dorner         | Harold A Driscoll   |
 | Michael Elkins     | Frank Ellerman       | Robert Elz          |
 | Johnny Eriksson    | Erik E Fair          | Roger Fajman        |
 | Patrik Faltstrom   | Claus Andre Faerber  | Barry Finkel        |
 | Erik Forsberg      | Chuck Foster         | Paul Fox            |
 | Klaus M Frank      | Ned Freed            | Jochen Friedrich    |
 | Randall C Gellens  | Sukvinder Singh Gill | Tim Goodwin         |
 | Philip Guenther    | Arnt Gulbrandsen     | Eric A Hall         |
 | Tony Hansen        | John Hawkinson       | Philip Hazel        |
 | Kai Henningsen     | Robert Herriot       | Paul Hethmon        |
 | Jim Hill           | Alfred Hoenes        | Paul E Hoffman      |
 | Steve Hole         | Kari Hurtta          | Marco S Hyman       |
 | Ofer Inbar         | Olle Jarnefors       | Kevin Johnson       |
 | Sudish Joseph      | Maynard Kang         | Prabhat Keni        |
 | John C Klensin     | Graham Klyne         | Brad Knowles        |
 | Shuhei Kobayashi   | Peter Koch           | Dan Kohn            |
 | Christian Kuhtz    | Anand Kumria         | Steen Larsen        |
 | Eliot Lear         | Barry Leiba          | Jay Levitt          |
 | Bruce Lilly        | Lars-Johan Liman     | Charles Lindsey     |
 | Pete Loshin        | Simon Lyall          | Bill Manning        |
 | John Martin        | Mark Martinec        | Larry Masinter      |
 | Denis McKeon       | William P McQuillan  | Alexey Melnikov     |
 | Perry E Metzger    | Steven Miller        | S Moonesamy         |
 | Keith Moore        | John Gardiner Myers  | Chris Newman        |
 | John W Noerenberg  | Eric Norman          | Mike O'Dell         |
 | Larry Osterman     | Paul Overell         | Jacob Palme         |
 | Michael A Patton   | Uzi Paz              | Michael A Quinlan   |
 | Robert Rapplean    | Eric S Raymond       | Sam Roberts         |
 | Hugh Sasse         | Bart Schaefer        | Tom Scola           |
 | Wolfgang Segmuller | Nick Shelness        | John Stanley        |
 | Einar Stefferud    | Jeff Stephenson      | Bernard Stern       |
 | Peter Sylvester    | Mark Symons          | Eric Thomas         |
 | Lee Thompson       | Karel De Vriendt     | Matthew Wall        |
 | Rolf Weber         | Brent B Welch        | Dan Wing            |
 | Jack De Winter     | Gregory J Woodhouse  | Greg A Woods        |
 | Kazu Yamamoto      | Alain Zahm           | Jamie Zawinski      |
 | Timothy S Zurcher  |                      |                     |
 +--------------------+----------------------+---------------------+

Resnick Standards Track [Page 54] RFC 5322 Internet Message Format October 2008

7. References

7.1. Normative References

 [ANSI.X3-4.1986]  American National Standards Institute, "Coded
                   Character Set - 7-bit American Standard Code for
                   Information Interchange", ANSI X3.4, 1986.
 [RFC1034]         Mockapetris, P., "Domain names - concepts and
                   facilities", STD 13, RFC 1034, November 1987.
 [RFC1035]         Mockapetris, P., "Domain names - implementation and
                   specification", STD 13, RFC 1035, November 1987.
 [RFC1123]         Braden, R., "Requirements for Internet Hosts -
                   Application and Support", STD 3, RFC 1123,
                   October 1989.
 [RFC2119]         Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC5234]         Crocker, D. and P. Overell, "Augmented BNF for
                   Syntax Specifications: ABNF", STD 68, RFC 5234,
                   January 2008.

7.2. Informative References

 [RFC0822]         Crocker, D., "Standard for the format of ARPA
                   Internet text messages", STD 11, RFC 822,
                   August 1982.
 [RFC1305]         Mills, D., "Network Time Protocol (Version 3)
                   Specification, Implementation", RFC 1305,
                   March 1992.
 [ISO.2022.1994]   International Organization for Standardization,
                   "Information technology - Character code structure
                   and extension techniques", ISO Standard 2022, 1994.
 [RFC2045]         Freed, N. and N. Borenstein, "Multipurpose Internet
                   Mail Extensions (MIME) Part One: Format of Internet
                   Message Bodies", RFC 2045, November 1996.
 [RFC2046]         Freed, N. and N. Borenstein, "Multipurpose Internet
                   Mail Extensions (MIME) Part Two: Media Types",
                   RFC 2046, November 1996.

Resnick Standards Track [Page 55] RFC 5322 Internet Message Format October 2008

 [RFC2047]         Moore, K., "MIME (Multipurpose Internet Mail
                   Extensions) Part Three: Message Header Extensions
                   for Non-ASCII Text", RFC 2047, November 1996.
 [RFC2049]         Freed, N. and N. Borenstein, "Multipurpose Internet
                   Mail Extensions (MIME) Part Five: Conformance
                   Criteria and Examples", RFC 2049, November 1996.
 [RFC2822]         Resnick, P., "Internet Message Format", RFC 2822,
                   April 2001.
 [RFC3864]         Klyne, G., Nottingham, M., and J. Mogul,
                   "Registration Procedures for Message Header
                   Fields", BCP 90, RFC 3864, September 2004.
 [RFC4021]         Klyne, G. and J. Palme, "Registration of Mail and
                   MIME Header Fields", RFC 4021, March 2005.
 [RFC4288]         Freed, N. and J. Klensin, "Media Type
                   Specifications and Registration Procedures",
                   BCP 13, RFC 4288, December 2005.
 [RFC4289]         Freed, N. and J. Klensin, "Multipurpose Internet
                   Mail Extensions (MIME) Part Four: Registration
                   Procedures", BCP 13, RFC 4289, December 2005.
 [RFC5321]         Klensin, J., "Simple Mail Transfer Protocol",
                   RFC 5321, October 2008.

Author's Address

 Peter W. Resnick (editor)
 Qualcomm Incorporated
 5775 Morehouse Drive
 San Diego, CA  92121-1714
 US
 Phone: +1 858 651 4478
 EMail: presnick@qualcomm.com
 URI:   http://www.qualcomm.com/~presnick/

Resnick Standards Track [Page 56] RFC 5322 Internet Message Format October 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Resnick Standards Track [Page 57]

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