+
+
+
+
+
+
+Network Working Group P. Resnick, Ed.
+Request for Comments: 5322 Qualcomm Incorporated
+Obsoletes: 2822 October 2008
+Updates: 4021
+Category: Standards Track
+
+
+ Internet Message Format
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document specifies the Internet Message Format (IMF), a syntax
+ for text messages that are sent between computer users, within the
+ framework of "electronic mail" messages. This specification is a
+ revision of Request For Comments (RFC) 2822, which itself superseded
+ Request For Comments (RFC) 822, "Standard for the Format of ARPA
+ Internet Text Messages", updating it to reflect current practice and
+ incorporating incremental changes that were specified in other RFCs.
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+RFC 5322 Internet Message Format October 2008
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+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 5
+ 1.2.1. Requirements Notation . . . . . . . . . . . . . . . . 5
+ 1.2.2. Syntactic Notation . . . . . . . . . . . . . . . . . . 5
+ 1.2.3. Structure of This Document . . . . . . . . . . . . . . 5
+ 2. Lexical Analysis of Messages . . . . . . . . . . . . . . . . . 6
+ 2.1. General Description . . . . . . . . . . . . . . . . . . . 6
+ 2.1.1. Line Length Limits . . . . . . . . . . . . . . . . . . 7
+ 2.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 8
+ 2.2.1. Unstructured Header Field Bodies . . . . . . . . . . . 8
+ 2.2.2. Structured Header Field Bodies . . . . . . . . . . . . 8
+ 2.2.3. Long Header Fields . . . . . . . . . . . . . . . . . . 8
+ 2.3. Body . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
+ 3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.2. Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
+ 3.2.1. Quoted characters . . . . . . . . . . . . . . . . . . 10
+ 3.2.2. Folding White Space and Comments . . . . . . . . . . . 11
+ 3.2.3. Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
+ 3.2.4. Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
+ 3.2.5. Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
+ 3.3. Date and Time Specification . . . . . . . . . . . . . . . 14
+ 3.4. Address Specification . . . . . . . . . . . . . . . . . . 16
+ 3.4.1. Addr-Spec Specification . . . . . . . . . . . . . . . 17
+ 3.5. Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
+ 3.6. Field Definitions . . . . . . . . . . . . . . . . . . . . 19
+ 3.6.1. The Origination Date Field . . . . . . . . . . . . . . 22
+ 3.6.2. Originator Fields . . . . . . . . . . . . . . . . . . 22
+ 3.6.3. Destination Address Fields . . . . . . . . . . . . . . 23
+ 3.6.4. Identification Fields . . . . . . . . . . . . . . . . 25
+ 3.6.5. Informational Fields . . . . . . . . . . . . . . . . . 27
+ 3.6.6. Resent Fields . . . . . . . . . . . . . . . . . . . . 28
+ 3.6.7. Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
+ 3.6.8. Optional Fields . . . . . . . . . . . . . . . . . . . 30
+ 4. Obsolete Syntax . . . . . . . . . . . . . . . . . . . . . . . 31
+ 4.1. Miscellaneous Obsolete Tokens . . . . . . . . . . . . . . 32
+ 4.2. Obsolete Folding White Space . . . . . . . . . . . . . . . 33
+ 4.3. Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
+ 4.4. Obsolete Addressing . . . . . . . . . . . . . . . . . . . 35
+ 4.5. Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
+ 4.5.1. Obsolete Origination Date Field . . . . . . . . . . . 36
+ 4.5.2. Obsolete Originator Fields . . . . . . . . . . . . . . 36
+ 4.5.3. Obsolete Destination Address Fields . . . . . . . . . 37
+ 4.5.4. Obsolete Identification Fields . . . . . . . . . . . . 37
+ 4.5.5. Obsolete Informational Fields . . . . . . . . . . . . 37
+
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+ 4.5.6. Obsolete Resent Fields . . . . . . . . . . . . . . . . 38
+ 4.5.7. Obsolete Trace Fields . . . . . . . . . . . . . . . . 38
+ 4.5.8. Obsolete optional fields . . . . . . . . . . . . . . . 38
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
+ Appendix A. Example Messages . . . . . . . . . . . . . . . . . 43
+ Appendix A.1. Addressing Examples . . . . . . . . . . . . . . . 44
+ Appendix A.1.1. A Message from One Person to Another with
+ Simple Addressing . . . . . . . . . . . . . . . . 44
+ Appendix A.1.2. Different Types of Mailboxes . . . . . . . . . . . 45
+ Appendix A.1.3. Group Addresses . . . . . . . . . . . . . . . . . 45
+ Appendix A.2. Reply Messages . . . . . . . . . . . . . . . . . . 46
+ Appendix A.3. Resent Messages . . . . . . . . . . . . . . . . . 47
+ Appendix A.4. Messages with Trace Fields . . . . . . . . . . . . 48
+ Appendix A.5. White Space, Comments, and Other Oddities . . . . 49
+ Appendix A.6. Obsoleted Forms . . . . . . . . . . . . . . . . . 50
+ Appendix A.6.1. Obsolete Addressing . . . . . . . . . . . . . . . 50
+ Appendix A.6.2. Obsolete Dates . . . . . . . . . . . . . . . . . . 50
+ Appendix A.6.3. Obsolete White Space and Comments . . . . . . . . 51
+ Appendix B. Differences from Earlier Specifications . . . . . 52
+ Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . 53
+ 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
+ 7.1. Normative References . . . . . . . . . . . . . . . . . . . 55
+ 7.2. Informative References . . . . . . . . . . . . . . . . . . 55
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+RFC 5322 Internet Message Format October 2008
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+
+1. Introduction
+
+1.1. Scope
+
+ This document specifies the Internet Message Format (IMF), a syntax
+ for text messages that are sent between computer users, within the
+ framework of "electronic mail" messages. This specification is an
+ update to [RFC2822], which itself superseded [RFC0822], updating it
+ to reflect current practice and incorporating incremental changes
+ that were specified in other RFCs such as [RFC1123].
+
+ This document specifies a syntax only for text messages. In
+ particular, it makes no provision for the transmission of images,
+ audio, or other sorts of structured data in electronic mail messages.
+ There are several extensions published, such as the MIME document
+ series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
+ for the transmission of such data through electronic mail, either by
+ extending the syntax provided here or by structuring such messages to
+ conform to this syntax. Those mechanisms are outside of the scope of
+ this specification.
+
+ In the context of electronic mail, messages are viewed as having an
+ envelope and contents. The envelope contains whatever information is
+ needed to accomplish transmission and delivery. (See [RFC5321] for a
+ discussion of the envelope.) The contents comprise the object to be
+ delivered to the recipient. This specification applies only to the
+ format and some of the semantics of message contents. It contains no
+ specification of the information in the envelope.
+
+ However, some message systems may use information from the contents
+ to create the envelope. It is intended that this specification
+ facilitate the acquisition of such information by programs.
+
+ This specification is intended as a definition of what message
+ content format is to be passed between systems. Though some message
+ systems locally store messages in this format (which eliminates the
+ need for translation between formats) and others use formats that
+ differ from the one specified in this specification, local storage is
+ outside of the scope of this specification.
+
+ Note: This specification is not intended to dictate the internal
+ formats used by sites, the specific message system features that
+ they are expected to support, or any of the characteristics of
+ user interface programs that create or read messages. In
+ addition, this document does not specify an encoding of the
+ characters for either transport or storage; that is, it does not
+ specify the number of bits used or how those bits are specifically
+ transferred over the wire or stored on disk.
+
+
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+
+1.2. Notational Conventions
+
+1.2.1. Requirements Notation
+
+ This document occasionally uses terms that appear in capital letters.
+ When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
+ NOT", and "MAY" appear capitalized, they are being used to indicate
+ particular requirements of this specification. A discussion of the
+ meanings of these terms appears in [RFC2119].
+
+1.2.2. Syntactic Notation
+
+ This specification uses the Augmented Backus-Naur Form (ABNF)
+ [RFC5234] notation for the formal definitions of the syntax of
+ messages. Characters will be specified either by a decimal value
+ (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
+ a case-insensitive literal value enclosed in quotation marks (e.g.,
+ "A" for either uppercase or lowercase A).
+
+1.2.3. Structure of This Document
+
+ This document is divided into several sections.
+
+ This section, section 1, is a short introduction to the document.
+
+ Section 2 lays out the general description of a message and its
+ constituent parts. This is an overview to help the reader understand
+ some of the general principles used in the later portions of this
+ document. Any examples in this section MUST NOT be taken as
+ specification of the formal syntax of any part of a message.
+
+ Section 3 specifies formal ABNF rules for the structure of each part
+ of a message (the syntax) and describes the relationship between
+ those parts and their meaning in the context of a message (the
+ semantics). That is, it lays out the actual rules for the structure
+ of each part of a message (the syntax) as well as a description of
+ the parts and instructions for their interpretation (the semantics).
+ This includes analysis of the syntax and semantics of subparts of
+ messages that have specific structure. The syntax included in
+ section 3 represents messages as they MUST be created. There are
+ also notes in section 3 to indicate if any of the options specified
+ in the syntax SHOULD be used over any of the others.
+
+ Both sections 2 and 3 describe messages that are legal to generate
+ for purposes of this specification.
+
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+ Section 4 of this document specifies an "obsolete" syntax. There are
+ references in section 3 to these obsolete syntactic elements. The
+ rules of the obsolete syntax are elements that have appeared in
+ earlier versions of this specification or have previously been widely
+ used in Internet messages. As such, these elements MUST be
+ interpreted by parsers of messages in order to be conformant to this
+ specification. However, since items in this syntax have been
+ determined to be non-interoperable or to cause significant problems
+ for recipients of messages, they MUST NOT be generated by creators of
+ conformant messages.
+
+ Section 5 details security considerations to take into account when
+ implementing this specification.
+
+ Appendix A lists examples of different sorts of messages. These
+ examples are not exhaustive of the types of messages that appear on
+ the Internet, but give a broad overview of certain syntactic forms.
+
+ Appendix B lists the differences between this specification and
+ earlier specifications for Internet messages.
+
+ Appendix C contains acknowledgements.
+
+2. Lexical Analysis of Messages
+
+2.1. General Description
+
+ At the most basic level, a message is a series of characters. A
+ message that is conformant with this specification is composed of
+ characters with values in the range of 1 through 127 and interpreted
+ as US-ASCII [ANSI.X3-4.1986] characters. For brevity, this document
+ sometimes refers to this range of characters as simply "US-ASCII
+ characters".
+
+ Note: This document specifies that messages are made up of
+ characters in the US-ASCII range of 1 through 127. There are
+ other documents, specifically the MIME document series ([RFC2045],
+ [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]), that
+ extend this specification to allow for values outside of that
+ range. Discussion of those mechanisms is not within the scope of
+ this specification.
+
+ Messages are divided into lines of characters. A line is a series of
+ characters that is delimited with the two characters carriage-return
+ and line-feed; that is, the carriage return (CR) character (ASCII
+ value 13) followed immediately by the line feed (LF) character (ASCII
+ value 10). (The carriage return/line feed pair is usually written in
+ this document as "CRLF".)
+
+
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+
+ A message consists of header fields (collectively called "the header
+ section of the message") followed, optionally, by a body. The header
+ section is a sequence of lines of characters with special syntax as
+ defined in this specification. The body is simply a sequence of
+ characters that follows the header section and is separated from the
+ header section by an empty line (i.e., a line with nothing preceding
+ the CRLF).
+
+ Note: Common parlance and earlier versions of this specification
+ use the term "header" to either refer to the entire header section
+ or to refer to an individual header field. To avoid ambiguity,
+ this document does not use the terms "header" or "headers" in
+ isolation, but instead always uses "header field" to refer to the
+ individual field and "header section" to refer to the entire
+ collection.
+
+2.1.1. Line Length Limits
+
+ There are two limits that this specification places on the number of
+ characters in a line. Each line of characters MUST be no more than
+ 998 characters, and SHOULD be no more than 78 characters, excluding
+ the CRLF.
+
+ The 998 character limit is due to limitations in many implementations
+ that send, receive, or store IMF messages which simply cannot handle
+ more than 998 characters on a line. Receiving implementations would
+ do well to handle an arbitrarily large number of characters in a line
+ for robustness sake. However, there are so many implementations that
+ (in compliance with the transport requirements of [RFC5321]) do not
+ accept messages containing more than 1000 characters including the CR
+ and LF per line, it is important for implementations not to create
+ such messages.
+
+ The more conservative 78 character recommendation is to accommodate
+ the many implementations of user interfaces that display these
+ messages which may truncate, or disastrously wrap, the display of
+ more than 78 characters per line, in spite of the fact that such
+ implementations are non-conformant to the intent of this
+ specification (and that of [RFC5321] if they actually cause
+ information to be lost). Again, even though this limitation is put
+ on messages, it is incumbent upon implementations that display
+ messages to handle an arbitrarily large number of characters in a
+ line (certainly at least up to the 998 character limit) for the sake
+ of robustness.
+
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+
+2.2. Header Fields
+
+ Header fields are lines beginning with a field name, followed by a
+ colon (":"), followed by a field body, and terminated by CRLF. A
+ field name MUST be composed of printable US-ASCII characters (i.e.,
+ characters that have values between 33 and 126, inclusive), except
+ colon. A field body may be composed of printable US-ASCII characters
+ as well as the space (SP, ASCII value 32) and horizontal tab (HTAB,
+ ASCII value 9) characters (together known as the white space
+ characters, WSP). A field body MUST NOT include CR and LF except
+ when used in "folding" and "unfolding", as described in section
+ 2.2.3. All field bodies MUST conform to the syntax described in
+ sections 3 and 4 of this specification.
+
+2.2.1. Unstructured Header Field Bodies
+
+ Some field bodies in this specification are defined simply as
+ "unstructured" (which is specified in section 3.2.5 as any printable
+ US-ASCII characters plus white space characters) with no further
+ restrictions. These are referred to as unstructured field bodies.
+ Semantically, unstructured field bodies are simply to be treated as a
+ single line of characters with no further processing (except for
+ "folding" and "unfolding" as described in section 2.2.3).
+
+2.2.2. Structured Header Field Bodies
+
+ Some field bodies in this specification have a syntax that is more
+ restrictive than the unstructured field bodies described above.
+ These are referred to as "structured" field bodies. Structured field
+ bodies are sequences of specific lexical tokens as described in
+ sections 3 and 4 of this specification. Many of these tokens are
+ allowed (according to their syntax) to be introduced or end with
+ comments (as described in section 3.2.2) as well as the white space
+ characters, and those white space characters are subject to "folding"
+ and "unfolding" as described in section 2.2.3. Semantic analysis of
+ structured field bodies is given along with their syntax.
+
+2.2.3. Long Header Fields
+
+ Each header field is logically a single line of characters comprising
+ the field name, the colon, and the field body. For convenience
+ however, and to deal with the 998/78 character limitations per line,
+ the field body portion of a header field can be split into a
+ multiple-line representation; this is called "folding". The general
+ rule is that wherever this specification allows for folding white
+ space (not simply WSP characters), a CRLF may be inserted before any
+ WSP.
+
+
+
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+ For example, the header field:
+
+ Subject: This is a test
+
+ can be represented as:
+
+ Subject: This
+ is a test
+
+ Note: Though structured field bodies are defined in such a way
+ that folding can take place between many of the lexical tokens
+ (and even within some of the lexical tokens), folding SHOULD be
+ limited to placing the CRLF at higher-level syntactic breaks. For
+ instance, if a field body is defined as comma-separated values, it
+ is recommended that folding occur after the comma separating the
+ structured items in preference to other places where the field
+ could be folded, even if it is allowed elsewhere.
+
+ The process of moving from this folded multiple-line representation
+ of a header field to its single line representation is called
+ "unfolding". Unfolding is accomplished by simply removing any CRLF
+ that is immediately followed by WSP. Each header field should be
+ treated in its unfolded form for further syntactic and semantic
+ evaluation. An unfolded header field has no length restriction and
+ therefore may be indeterminately long.
+
+2.3. Body
+
+ The body of a message is simply lines of US-ASCII characters. The
+ only two limitations on the body are as follows:
+
+ o CR and LF MUST only occur together as CRLF; they MUST NOT appear
+ independently in the body.
+ o Lines of characters in the body MUST be limited to 998 characters,
+ and SHOULD be limited to 78 characters, excluding the CRLF.
+
+ Note: As was stated earlier, there are other documents,
+ specifically the MIME documents ([RFC2045], [RFC2046], [RFC2049],
+ [RFC4288], [RFC4289]), that extend (and limit) this specification
+ to allow for different sorts of message bodies. Again, these
+ mechanisms are beyond the scope of this document.
+
+
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+3. Syntax
+
+3.1. Introduction
+
+ The syntax as given in this section defines the legal syntax of
+ Internet messages. Messages that are conformant to this
+ specification MUST conform to the syntax in this section. If there
+ are options in this section where one option SHOULD be generated,
+ that is indicated either in the prose or in a comment next to the
+ syntax.
+
+ For the defined expressions, a short description of the syntax and
+ use is given, followed by the syntax in ABNF, followed by a semantic
+ analysis. The following primitive tokens that are used but otherwise
+ unspecified are taken from the "Core Rules" of [RFC5234], Appendix
+ B.1: CR, LF, CRLF, HTAB, SP, WSP, DQUOTE, DIGIT, ALPHA, and VCHAR.
+
+ In some of the definitions, there will be non-terminals whose names
+ start with "obs-". These "obs-" elements refer to tokens defined in
+ the obsolete syntax in section 4. In all cases, these productions
+ are to be ignored for the purposes of generating legal Internet
+ messages and MUST NOT be used as part of such a message. However,
+ when interpreting messages, these tokens MUST be honored as part of
+ the legal syntax. In this sense, section 3 defines a grammar for the
+ generation of messages, with "obs-" elements that are to be ignored,
+ while section 4 adds grammar for the interpretation of messages.
+
+3.2. Lexical Tokens
+
+ The following rules are used to define an underlying lexical
+ analyzer, which feeds tokens to the higher-level parsers. This
+ section defines the tokens used in structured header field bodies.
+
+ Note: Readers of this specification need to pay special attention
+ to how these lexical tokens are used in both the lower-level and
+ higher-level syntax later in the document. Particularly, the
+ white space tokens and the comment tokens defined in section 3.2.2
+ get used in the lower-level tokens defined here, and those lower-
+ level tokens are in turn used as parts of the higher-level tokens
+ defined later. Therefore, white space and comments may be allowed
+ in the higher-level tokens even though they may not explicitly
+ appear in a particular definition.
+
+3.2.1. Quoted characters
+
+ Some characters are reserved for special interpretation, such as
+ delimiting lexical tokens. To permit use of these characters as
+ uninterpreted data, a quoting mechanism is provided.
+
+
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+ quoted-pair = ("\" (VCHAR / WSP)) / obs-qp
+
+ Where any quoted-pair appears, it is to be interpreted as the
+ character alone. That is to say, the "\" character that appears as
+ part of a quoted-pair is semantically "invisible".
+
+ Note: The "\" character may appear in a message where it is not
+ part of a quoted-pair. A "\" character that does not appear in a
+ quoted-pair is not semantically invisible. The only places in
+ this specification where quoted-pair currently appears are
+ ccontent, qcontent, and in obs-dtext in section 4.
+
+3.2.2. Folding White Space and Comments
+
+ White space characters, including white space used in folding
+ (described in section 2.2.3), may appear between many elements in
+ header field bodies. Also, strings of characters that are treated as
+ comments may be included in structured field bodies as characters
+ enclosed in parentheses. The following defines the folding white
+ space (FWS) and comment constructs.
+
+ Strings of characters enclosed in parentheses are considered comments
+ so long as they do not appear within a "quoted-string", as defined in
+ section 3.2.4. Comments may nest.
+
+ There are several places in this specification where comments and FWS
+ may be freely inserted. To accommodate that syntax, an additional
+ token for "CFWS" is defined for places where comments and/or FWS can
+ occur. However, where CFWS occurs in this specification, it MUST NOT
+ be inserted in such a way that any line of a folded header field is
+ made up entirely of WSP characters and nothing else.
+
+ FWS = ([*WSP CRLF] 1*WSP) / obs-FWS
+ ; Folding white space
+
+ ctext = %d33-39 / ; Printable US-ASCII
+ %d42-91 / ; characters not including
+ %d93-126 / ; "(", ")", or "\"
+ obs-ctext
+
+ ccontent = ctext / quoted-pair / comment
+
+ comment = "(" *([FWS] ccontent) [FWS] ")"
+
+ CFWS = (1*([FWS] comment) [FWS]) / FWS
+
+
+
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+
+ Throughout this specification, where FWS (the folding white space
+ token) appears, it indicates a place where folding, as discussed in
+ section 2.2.3, may take place. Wherever folding appears in a message
+ (that is, a header field body containing a CRLF followed by any WSP),
+ unfolding (removal of the CRLF) is performed before any further
+ semantic analysis is performed on that header field according to this
+ specification. That is to say, any CRLF that appears in FWS is
+ semantically "invisible".
+
+ A comment is normally used in a structured field body to provide some
+ human-readable informational text. Since a comment is allowed to
+ contain FWS, folding is permitted within the comment. Also note that
+ since quoted-pair is allowed in a comment, the parentheses and
+ backslash characters may appear in a comment, so long as they appear
+ as a quoted-pair. Semantically, the enclosing parentheses are not
+ part of the comment; the comment is what is contained between the two
+ parentheses. As stated earlier, the "\" in any quoted-pair and the
+ CRLF in any FWS that appears within the comment are semantically
+ "invisible" and therefore not part of the comment either.
+
+ Runs of FWS, comment, or CFWS that occur between lexical tokens in a
+ structured header field are semantically interpreted as a single
+ space character.
+
+3.2.3. Atom
+
+ Several productions in structured header field bodies are simply
+ strings of certain basic characters. Such productions are called
+ atoms.
+
+ Some of the structured header field bodies also allow the period
+ character (".", ASCII value 46) within runs of atext. An additional
+ "dot-atom" token is defined for those purposes.
+
+ Note: The "specials" token does not appear anywhere else in this
+ specification. It is simply the visible (i.e., non-control, non-
+ white space) characters that do not appear in atext. It is
+ provided only because it is useful for implementers who use tools
+ that lexically analyze messages. Each of the characters in
+ specials can be used to indicate a tokenization point in lexical
+ analysis.
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 12]
+\f
+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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 13]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ qtext = %d33 / ; Printable US-ASCII
+ %d35-91 / ; characters not including
+ %d93-126 / ; "\" or the quote character
+ obs-qtext
+
+ qcontent = qtext / quoted-pair
+
+ quoted-string = [CFWS]
+ DQUOTE *([FWS] qcontent) [FWS] DQUOTE
+ [CFWS]
+
+ A quoted-string is treated as a unit. That is, quoted-string is
+ identical to atom, semantically. Since a quoted-string is allowed to
+ contain FWS, folding is permitted. Also note that since quoted-pair
+ is allowed in a quoted-string, the quote and backslash characters may
+ appear in a quoted-string so long as they appear as a quoted-pair.
+
+ Semantically, neither the optional CFWS outside of the quote
+ characters nor the quote characters themselves are part of the
+ quoted-string; the quoted-string is what is contained between the two
+ quote characters. As stated earlier, the "\" in any quoted-pair and
+ the CRLF in any FWS/CFWS that appears within the quoted-string are
+ semantically "invisible" and therefore not part of the quoted-string
+ either.
+
+3.2.5. Miscellaneous Tokens
+
+ Three additional tokens are defined: word and phrase for combinations
+ of atoms and/or quoted-strings, and unstructured for use in
+ unstructured header fields and in some places within structured
+ header fields.
+
+ word = atom / quoted-string
+
+ phrase = 1*word / obs-phrase
+
+ unstructured = (*([FWS] VCHAR) *WSP) / obs-unstruct
+
+3.3. Date and Time Specification
+
+ Date and time values occur in several header fields. This section
+ specifies the syntax for a full date and time specification. Though
+ folding white space is permitted throughout the date-time
+ specification, it is RECOMMENDED that a single space be used in each
+ place that FWS appears (whether it is required or optional); some
+ older implementations will not interpret longer sequences of folding
+ white space correctly.
+
+
+
+
+Resnick Standards Track [Page 14]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ date-time = [ day-of-week "," ] date time [CFWS]
+
+ day-of-week = ([FWS] day-name) / obs-day-of-week
+
+ day-name = "Mon" / "Tue" / "Wed" / "Thu" /
+ "Fri" / "Sat" / "Sun"
+
+ date = day month year
+
+ day = ([FWS] 1*2DIGIT FWS) / obs-day
+
+ month = "Jan" / "Feb" / "Mar" / "Apr" /
+ "May" / "Jun" / "Jul" / "Aug" /
+ "Sep" / "Oct" / "Nov" / "Dec"
+
+ year = (FWS 4*DIGIT FWS) / obs-year
+
+ time = time-of-day zone
+
+ time-of-day = hour ":" minute [ ":" second ]
+
+ hour = 2DIGIT / obs-hour
+
+ minute = 2DIGIT / obs-minute
+
+ second = 2DIGIT / obs-second
+
+ zone = (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
+
+ The day is the numeric day of the month. The year is any numeric
+ year 1900 or later.
+
+ The time-of-day specifies the number of hours, minutes, and
+ optionally seconds since midnight of the date indicated.
+
+ The date and time-of-day SHOULD express local time.
+
+ The zone specifies the offset from Coordinated Universal Time (UTC,
+ formerly referred to as "Greenwich Mean Time") that the date and
+ time-of-day represent. The "+" or "-" indicates whether the time-of-
+ day is ahead of (i.e., east of) or behind (i.e., west of) Universal
+ Time. The first two digits indicate the number of hours difference
+ from Universal Time, and the last two digits indicate the number of
+ additional minutes difference from Universal Time. (Hence, +hhmm
+ means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
+ minutes). The form "+0000" SHOULD be used to indicate a time zone at
+ Universal Time. Though "-0000" also indicates Universal Time, it is
+
+
+
+
+Resnick Standards Track [Page 15]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ used to indicate that the time was generated on a system that may be
+ in a local time zone other than Universal Time and that the date-time
+ contains no information about the local time zone.
+
+ A date-time specification MUST be semantically valid. That is, the
+ day-of-week (if included) MUST be the day implied by the date, the
+ numeric day-of-month MUST be between 1 and the number of days allowed
+ for the specified month (in the specified year), the time-of-day MUST
+ be in the range 00:00:00 through 23:59:60 (the number of seconds
+ allowing for a leap second; see [RFC1305]), and the last two digits
+ of the zone MUST be within the range 00 through 59.
+
+3.4. Address Specification
+
+ Addresses occur in several message header fields to indicate senders
+ and recipients of messages. An address may either be an individual
+ mailbox, or a group of mailboxes.
+
+ address = mailbox / group
+
+ mailbox = name-addr / addr-spec
+
+ name-addr = [display-name] angle-addr
+
+ angle-addr = [CFWS] "<" addr-spec ">" [CFWS] /
+ obs-angle-addr
+
+ group = display-name ":" [group-list] ";" [CFWS]
+
+ display-name = phrase
+
+ mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
+
+ address-list = (address *("," address)) / obs-addr-list
+
+ group-list = mailbox-list / CFWS / obs-group-list
+
+ A mailbox receives mail. It is a conceptual entity that does not
+ necessarily pertain to file storage. For example, some sites may
+ choose to print mail on a printer and deliver the output to the
+ addressee's desk.
+
+ Normally, a mailbox is composed of two parts: (1) an optional display
+ name that indicates the name of the recipient (which can be a person
+ or a system) that could be displayed to the user of a mail
+ application, and (2) an addr-spec address enclosed in angle brackets
+
+
+
+
+
+Resnick Standards Track [Page 16]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ ("<" and ">"). There is an alternate simple form of a mailbox where
+ the addr-spec address appears alone, without the recipient's name or
+ the angle brackets. The Internet addr-spec address is described in
+ section 3.4.1.
+
+ Note: Some legacy implementations used the simple form where the
+ addr-spec appears without the angle brackets, but included the
+ name of the recipient in parentheses as a comment following the
+ addr-spec. Since the meaning of the information in a comment is
+ unspecified, implementations SHOULD use the full name-addr form of
+ the mailbox, instead of the legacy form, to specify the display
+ name associated with a mailbox. Also, because some legacy
+ implementations interpret the comment, comments generally SHOULD
+ NOT be used in address fields to avoid confusing such
+ implementations.
+
+ When it is desirable to treat several mailboxes as a single unit
+ (i.e., in a distribution list), the group construct can be used. The
+ group construct allows the sender to indicate a named group of
+ recipients. This is done by giving a display name for the group,
+ followed by a colon, followed by a comma-separated list of any number
+ of mailboxes (including zero and one), and ending with a semicolon.
+ Because the list of mailboxes can be empty, using the group construct
+ is also a simple way to communicate to recipients that the message
+ was sent to one or more named sets of recipients, without actually
+ providing the individual mailbox address for any of those recipients.
+
+3.4.1. Addr-Spec Specification
+
+ An addr-spec is a specific Internet identifier that contains a
+ locally interpreted string followed by the at-sign character ("@",
+ ASCII value 64) followed by an Internet domain. The locally
+ interpreted string is either a quoted-string or a dot-atom. If the
+ string can be represented as a dot-atom (that is, it contains no
+ characters other than atext characters or "." surrounded by atext
+ characters), then the dot-atom form SHOULD be used and the quoted-
+ string form SHOULD NOT be used. Comments and folding white space
+ SHOULD NOT be used around the "@" in the addr-spec.
+
+ Note: A liberal syntax for the domain portion of addr-spec is
+ given here. However, the domain portion contains addressing
+ information specified by and used in other protocols (e.g.,
+ [RFC1034], [RFC1035], [RFC1123], [RFC5321]). It is therefore
+ incumbent upon implementations to conform to the syntax of
+ addresses for the context in which they are used.
+
+
+
+
+
+
+Resnick Standards Track [Page 17]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ addr-spec = local-part "@" domain
+
+ local-part = dot-atom / quoted-string / obs-local-part
+
+ domain = dot-atom / domain-literal / obs-domain
+
+ domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
+
+ dtext = %d33-90 / ; Printable US-ASCII
+ %d94-126 / ; characters not including
+ obs-dtext ; "[", "]", or "\"
+
+ The domain portion identifies the point to which the mail is
+ delivered. In the dot-atom form, this is interpreted as an Internet
+ domain name (either a host name or a mail exchanger name) as
+ described in [RFC1034], [RFC1035], and [RFC1123]. In the domain-
+ literal form, the domain is interpreted as the literal Internet
+ address of the particular host. In both cases, how addressing is
+ used and how messages are transported to a particular host is covered
+ in separate documents, such as [RFC5321]. These mechanisms are
+ outside of the scope of this document.
+
+ The local-part portion is a domain-dependent string. In addresses,
+ it is simply interpreted on the particular host as a name of a
+ particular mailbox.
+
+3.5. Overall Message Syntax
+
+ A message consists of header fields, optionally followed by a message
+ body. Lines in a message MUST be a maximum of 998 characters
+ excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
+ characters excluding the CRLF. (See section 2.1.1 for explanation.)
+ In a message body, though all of the characters listed in the text
+ rule MAY be used, the use of US-ASCII control characters (values 1
+ through 8, 11, 12, and 14 through 31) is discouraged since their
+ interpretation by receivers for display is not guaranteed.
+
+ message = (fields / obs-fields)
+ [CRLF body]
+
+ body = (*(*998text CRLF) *998text) / obs-body
+
+ text = %d1-9 / ; Characters excluding CR
+ %d11 / ; and LF
+ %d12 /
+ %d14-127
+
+
+
+
+
+Resnick Standards Track [Page 18]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ The header fields carry most of the semantic information and are
+ defined in section 3.6. The body is simply a series of lines of text
+ that are uninterpreted for the purposes of this specification.
+
+3.6. Field Definitions
+
+ The header fields of a message are defined here. All header fields
+ have the same general syntactic structure: a field name, followed by
+ a colon, followed by the field body. The specific syntax for each
+ header field is defined in the subsequent sections.
+
+ Note: In the ABNF syntax for each field in subsequent sections,
+ each field name is followed by the required colon. However, for
+ brevity, sometimes the colon is not referred to in the textual
+ description of the syntax. It is, nonetheless, required.
+
+ It is important to note that the header fields are not guaranteed to
+ be in a particular order. They may appear in any order, and they
+ have been known to be reordered occasionally when transported over
+ the Internet. However, for the purposes of this specification,
+ header fields SHOULD NOT be reordered when a message is transported
+ or transformed. More importantly, the trace header fields and resent
+ header fields MUST NOT be reordered, and SHOULD be kept in blocks
+ prepended to the message. See sections 3.6.6 and 3.6.7 for more
+ information.
+
+ The only required header fields are the origination date field and
+ the originator address field(s). All other header fields are
+ syntactically optional. More information is contained in the table
+ following this definition.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 19]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ fields = *(trace
+ *optional-field /
+ *(resent-date /
+ resent-from /
+ resent-sender /
+ resent-to /
+ resent-cc /
+ resent-bcc /
+ resent-msg-id))
+ *(orig-date /
+ from /
+ sender /
+ reply-to /
+ to /
+ cc /
+ bcc /
+ message-id /
+ in-reply-to /
+ references /
+ subject /
+ comments /
+ keywords /
+ optional-field)
+
+ The following table indicates limits on the number of times each
+ field may occur in the header section of a message as well as any
+ special limitations on the use of those fields. An asterisk ("*")
+ next to a value in the minimum or maximum column indicates that a
+ special restriction appears in the Notes column.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 20]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ +----------------+--------+------------+----------------------------+
+ | Field | Min | Max number | Notes |
+ | | number | | |
+ +----------------+--------+------------+----------------------------+
+ | trace | 0 | unlimited | Block prepended - see |
+ | | | | 3.6.7 |
+ | resent-date | 0* | unlimited* | One per block, required if |
+ | | | | other resent fields are |
+ | | | | present - see 3.6.6 |
+ | resent-from | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-sender | 0* | unlimited* | One per block, MUST occur |
+ | | | | with multi-address |
+ | | | | resent-from - see 3.6.6 |
+ | resent-to | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-cc | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-bcc | 0 | unlimited* | One per block - see 3.6.6 |
+ | resent-msg-id | 0 | unlimited* | One per block - see 3.6.6 |
+ | orig-date | 1 | 1 | |
+ | from | 1 | 1 | See sender and 3.6.2 |
+ | sender | 0* | 1 | MUST occur with |
+ | | | | multi-address from - see |
+ | | | | 3.6.2 |
+ | reply-to | 0 | 1 | |
+ | to | 0 | 1 | |
+ | cc | 0 | 1 | |
+ | bcc | 0 | 1 | |
+ | message-id | 0* | 1 | SHOULD be present - see |
+ | | | | 3.6.4 |
+ | in-reply-to | 0* | 1 | SHOULD occur in some |
+ | | | | replies - see 3.6.4 |
+ | references | 0* | 1 | SHOULD occur in some |
+ | | | | replies - see 3.6.4 |
+ | subject | 0 | 1 | |
+ | comments | 0 | unlimited | |
+ | keywords | 0 | unlimited | |
+ | optional-field | 0 | unlimited | |
+ +----------------+--------+------------+----------------------------+
+
+ The exact interpretation of each field is described in subsequent
+ sections.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 21]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+3.6.1. The Origination Date Field
+
+ The origination date field consists of the field name "Date" followed
+ by a date-time specification.
+
+ orig-date = "Date:" date-time CRLF
+
+ The origination date specifies the date and time at which the creator
+ of the message indicated that the message was complete and ready to
+ enter the mail delivery system. For instance, this might be the time
+ that a user pushes the "send" or "submit" button in an application
+ program. In any case, it is specifically not intended to convey the
+ time that the message is actually transported, but rather the time at
+ which the human or other creator of the message has put the message
+ into its final form, ready for transport. (For example, a portable
+ computer user who is not connected to a network might queue a message
+ for delivery. The origination date is intended to contain the date
+ and time that the user queued the message, not the time when the user
+ connected to the network to send the message.)
+
+3.6.2. Originator Fields
+
+ The originator fields of a message consist of the from field, the
+ sender field (when applicable), and optionally the reply-to field.
+ The from field consists of the field name "From" and a comma-
+ separated list of one or more mailbox specifications. If the from
+ field contains more than one mailbox specification in the mailbox-
+ list, then the sender field, containing the field name "Sender" and a
+ single mailbox specification, MUST appear in the message. In either
+ case, an optional reply-to field MAY also be included, which contains
+ the field name "Reply-To" and a comma-separated list of one or more
+ addresses.
+
+ from = "From:" mailbox-list CRLF
+
+ sender = "Sender:" mailbox CRLF
+
+ reply-to = "Reply-To:" address-list CRLF
+
+ The originator fields indicate the mailbox(es) of the source of the
+ message. The "From:" field specifies the author(s) of the message,
+ that is, the mailbox(es) of the person(s) or system(s) responsible
+ for the writing of the message. The "Sender:" field specifies the
+ mailbox of the agent responsible for the actual transmission of the
+ message. For example, if a secretary were to send a message for
+ another person, the mailbox of the secretary would appear in the
+ "Sender:" field and the mailbox of the actual author would appear in
+ the "From:" field. If the originator of the message can be indicated
+
+
+
+Resnick Standards Track [Page 22]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ by a single mailbox and the author and transmitter are identical, the
+ "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
+ appear.
+
+ Note: The transmitter information is always present. The absence
+ of the "Sender:" field is sometimes mistakenly taken to mean that
+ the agent responsible for transmission of the message has not been
+ specified. This absence merely means that the transmitter is
+ identical to the author and is therefore not redundantly placed
+ into the "Sender:" field.
+
+ The originator fields also provide the information required when
+ replying to a message. When the "Reply-To:" field is present, it
+ indicates the address(es) to which the author of the message suggests
+ that replies be sent. In the absence of the "Reply-To:" field,
+ replies SHOULD by default be sent to the mailbox(es) specified in the
+ "From:" field unless otherwise specified by the person composing the
+ reply.
+
+ In all cases, the "From:" field SHOULD NOT contain any mailbox that
+ does not belong to the author(s) of the message. See also section
+ 3.6.3 for more information on forming the destination addresses for a
+ reply.
+
+3.6.3. Destination Address Fields
+
+ The destination fields of a message consist of three possible fields,
+ each of the same form: the field name, which is either "To", "Cc", or
+ "Bcc", followed by a comma-separated list of one or more addresses
+ (either mailbox or group syntax).
+
+ to = "To:" address-list CRLF
+
+ cc = "Cc:" address-list CRLF
+
+ bcc = "Bcc:" [address-list / CFWS] CRLF
+
+ The destination fields specify the recipients of the message. Each
+ destination field may have one or more addresses, and the addresses
+ indicate the intended recipients of the message. The only difference
+ between the three fields is how each is used.
+
+ The "To:" field contains the address(es) of the primary recipient(s)
+ of the message.
+
+
+
+
+
+
+
+Resnick Standards Track [Page 23]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
+ making a copy on a typewriter using carbon paper) contains the
+ addresses of others who are to receive the message, though the
+ content of the message may not be directed at them.
+
+ The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
+ addresses of recipients of the message whose addresses are not to be
+ revealed to other recipients of the message. There are three ways in
+ which the "Bcc:" field is used. In the first case, when a message
+ containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
+ removed even though all of the recipients (including those specified
+ in the "Bcc:" field) are sent a copy of the message. In the second
+ case, recipients specified in the "To:" and "Cc:" lines each are sent
+ a copy of the message with the "Bcc:" line removed as above, but the
+ recipients on the "Bcc:" line get a separate copy of the message
+ containing a "Bcc:" line. (When there are multiple recipient
+ addresses in the "Bcc:" field, some implementations actually send a
+ separate copy of the message to each recipient with a "Bcc:"
+ containing only the address of that particular recipient.) Finally,
+ since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
+ sent without any addresses indicating to the recipients that blind
+ copies were sent to someone. Which method to use with "Bcc:" fields
+ is implementation dependent, but refer to the "Security
+ Considerations" section of this document for a discussion of each.
+
+ When a message is a reply to another message, the mailboxes of the
+ authors of the original message (the mailboxes in the "From:" field)
+ or mailboxes specified in the "Reply-To:" field (if it exists) MAY
+ appear in the "To:" field of the reply since these would normally be
+ the primary recipients of the reply. If a reply is sent to a message
+ that has destination fields, it is often desirable to send a copy of
+ the reply to all of the recipients of the message, in addition to the
+ author. When such a reply is formed, addresses in the "To:" and
+ "Cc:" fields of the original message MAY appear in the "Cc:" field of
+ the reply, since these are normally secondary recipients of the
+ reply. If a "Bcc:" field is present in the original message,
+ addresses in that field MAY appear in the "Bcc:" field of the reply,
+ but they SHOULD NOT appear in the "To:" or "Cc:" fields.
+
+ Note: Some mail applications have automatic reply commands that
+ include the destination addresses of the original message in the
+ destination addresses of the reply. How those reply commands
+ behave is implementation dependent and is beyond the scope of this
+ document. In particular, whether or not to include the original
+ destination addresses when the original message had a "Reply-To:"
+ field is not addressed here.
+
+
+
+
+
+Resnick Standards Track [Page 24]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+3.6.4. Identification Fields
+
+ Though listed as optional in the table in section 3.6, every message
+ SHOULD have a "Message-ID:" field. Furthermore, reply messages
+ SHOULD have "In-Reply-To:" and "References:" fields as appropriate
+ and as described below.
+
+ The "Message-ID:" field contains a single unique message identifier.
+ The "References:" and "In-Reply-To:" fields each contain one or more
+ unique message identifiers, optionally separated by CFWS.
+
+ The message identifier (msg-id) syntax is a limited version of the
+ addr-spec construct enclosed in the angle bracket characters, "<" and
+ ">". Unlike addr-spec, this syntax only permits the dot-atom-text
+ form on the left-hand side of the "@" and does not have internal CFWS
+ anywhere in the message identifier.
+
+ Note: As with addr-spec, a liberal syntax is given for the right-
+ hand side of the "@" in a msg-id. However, later in this section,
+ the use of a domain for the right-hand side of the "@" is
+ RECOMMENDED. Again, the syntax of domain constructs is specified
+ by and used in other protocols (e.g., [RFC1034], [RFC1035],
+ [RFC1123], [RFC5321]). It is therefore incumbent upon
+ implementations to conform to the syntax of addresses for the
+ context in which they are used.
+
+ message-id = "Message-ID:" msg-id CRLF
+
+ in-reply-to = "In-Reply-To:" 1*msg-id CRLF
+
+ references = "References:" 1*msg-id CRLF
+
+ msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
+
+ id-left = dot-atom-text / obs-id-left
+
+ id-right = dot-atom-text / no-fold-literal / obs-id-right
+
+ no-fold-literal = "[" *dtext "]"
+
+ The "Message-ID:" field provides a unique message identifier that
+ refers to a particular version of a particular message. The
+ uniqueness of the message identifier is guaranteed by the host that
+ generates it (see below). This message identifier is intended to be
+ machine readable and not necessarily meaningful to humans. A message
+ identifier pertains to exactly one version of a particular message;
+ subsequent revisions to the message each receive new message
+ identifiers.
+
+
+
+Resnick Standards Track [Page 25]
+\f
+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]
+\f
+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]
+\f
+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
+
+
+
+
+
+Resnick Standards Track [Page 28]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ Resent fields are used to identify a message as having been
+ reintroduced into the transport system by a user. The purpose of
+ using resent fields is to have the message appear to the final
+ recipient as if it were sent directly by the original sender, with
+ all of the original fields remaining the same. Each set of resent
+ fields correspond to a particular resending event. That is, if a
+ message is resent multiple times, each set of resent fields gives
+ identifying information for each individual time. Resent fields are
+ strictly informational. They MUST NOT be used in the normal
+ processing of replies or other such automatic actions on messages.
+
+ Note: Reintroducing a message into the transport system and using
+ resent fields is a different operation from "forwarding".
+ "Forwarding" has two meanings: One sense of forwarding is that a
+ mail reading program can be told by a user to forward a copy of a
+ message to another person, making the forwarded message the body
+ of the new message. A forwarded message in this sense does not
+ appear to have come from the original sender, but is an entirely
+ new message from the forwarder of the message. Forwarding may
+ also mean that a mail transport program gets a message and
+ forwards it on to a different destination for final delivery.
+ Resent header fields are not intended for use with either type of
+ forwarding.
+
+ The resent originator fields indicate the mailbox of the person(s) or
+ system(s) that resent the message. As with the regular originator
+ fields, there are two forms: a simple "Resent-From:" form, which
+ contains the mailbox of the individual doing the resending, and the
+ more complex form, when one individual (identified in the "Resent-
+ Sender:" field) resends a message on behalf of one or more others
+ (identified in the "Resent-From:" field).
+
+ Note: When replying to a resent message, replies behave just as
+ they would with any other message, using the original "From:",
+ "Reply-To:", "Message-ID:", and other fields. The resent fields
+ are only informational and MUST NOT be used in the normal
+ processing of replies.
+
+ The "Resent-Date:" indicates the date and time at which the resent
+ message is dispatched by the resender of the message. Like the
+ "Date:" field, it is not the date and time that the message was
+ actually transported.
+
+ The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
+ identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
+ except that they indicate the recipients of the resent message, not
+ the recipients of the original message.
+
+
+
+
+Resnick Standards Track [Page 29]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ The "Resent-Message-ID:" field provides a unique identifier for the
+ resent message.
+
+3.6.7. Trace Fields
+
+ The trace fields are a group of header fields consisting of an
+ optional "Return-Path:" field, and one or more "Received:" fields.
+ The "Return-Path:" header field contains a pair of angle brackets
+ that enclose an optional addr-spec. The "Received:" field contains a
+ (possibly empty) list of tokens followed by a semicolon and a date-
+ time specification. Each token must be a word, angle-addr, addr-
+ spec, or a domain. Further restrictions are applied to the syntax of
+ the trace fields by specifications that provide for their use, such
+ as [RFC5321].
+
+ trace = [return]
+ 1*received
+
+ return = "Return-Path:" path CRLF
+
+ path = angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
+
+ received = "Received:" *received-token ";" date-time CRLF
+
+ received-token = word / angle-addr / addr-spec / domain
+
+ A full discussion of the Internet mail use of trace fields is
+ contained in [RFC5321]. For the purposes of this specification, the
+ trace fields are strictly informational, and any formal
+ interpretation of them is outside of the scope of this document.
+
+3.6.8. Optional Fields
+
+ Fields may appear in messages that are otherwise unspecified in this
+ document. They MUST conform to the syntax of an optional-field.
+ This is a field name, made up of the printable US-ASCII characters
+ except SP and colon, followed by a colon, followed by any text that
+ conforms to the unstructured syntax.
+
+ The field names of any optional field MUST NOT be identical to any
+ field name specified elsewhere in this document.
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 30]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ optional-field = field-name ":" unstructured CRLF
+
+ field-name = 1*ftext
+
+ ftext = %d33-57 / ; Printable US-ASCII
+ %d59-126 ; characters not including
+ ; ":".
+
+ For the purposes of this specification, any optional field is
+ uninterpreted.
+
+4. Obsolete Syntax
+
+ Earlier versions of this specification allowed for different (usually
+ more liberal) syntax than is allowed in this version. Also, there
+ have been syntactic elements used in messages on the Internet whose
+ interpretations have never been documented. Though these syntactic
+ forms MUST NOT be generated according to the grammar in section 3,
+ they MUST be accepted and parsed by a conformant receiver. This
+ section documents many of these syntactic elements. Taking the
+ grammar in section 3 and adding the definitions presented in this
+ section will result in the grammar to use for the interpretation of
+ messages.
+
+ Note: This section identifies syntactic forms that any
+ implementation MUST reasonably interpret. However, there are
+ certainly Internet messages that do not conform to even the
+ additional syntax given in this section. The fact that a
+ particular form does not appear in any section of this document is
+ not justification for computer programs to crash or for malformed
+ data to be irretrievably lost by any implementation. It is up to
+ the implementation to deal with messages robustly.
+
+ One important difference between the obsolete (interpreting) and the
+ current (generating) syntax is that in structured header field bodies
+ (i.e., between the colon and the CRLF of any structured header
+ field), white space characters, including folding white space, and
+ comments could be freely inserted between any syntactic tokens. This
+ allowed many complex forms that have proven difficult for some
+ implementations to parse.
+
+ Another key difference between the obsolete and the current syntax is
+ that the rule in section 3.2.2 regarding lines composed entirely of
+ white space in comments and folding white space does not apply. See
+ the discussion of folding white space in section 4.2 below.
+
+ Finally, certain characters that were formerly allowed in messages
+ appear in this section. The NUL character (ASCII value 0) was once
+
+
+
+Resnick Standards Track [Page 31]
+\f
+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]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ obs-phrase = word *(word / "." / CFWS)
+
+ obs-phrase-list = [phrase / CFWS] *("," [phrase / CFWS])
+
+ Bare CR and bare LF appear in messages with two different meanings.
+ In many cases, bare CR or bare LF are used improperly instead of CRLF
+ to indicate line separators. In other cases, bare CR and bare LF are
+ used simply as US-ASCII control characters with their traditional
+ ASCII meanings.
+
+4.2. Obsolete Folding White Space
+
+ In the obsolete syntax, any amount of folding white space MAY be
+ inserted where the obs-FWS rule is allowed. This creates the
+ possibility of having two consecutive "folds" in a line, and
+ therefore the possibility that a line which makes up a folded header
+ field could be composed entirely of white space.
+
+ obs-FWS = 1*WSP *(CRLF 1*WSP)
+
+4.3. Obsolete Date and Time
+
+ The syntax for the obsolete date format allows a 2 digit year in the
+ date field and allows for a list of alphabetic time zone specifiers
+ that were used in earlier versions of this specification. It also
+ permits comments and folding white space between many of the tokens.
+
+ obs-day-of-week = [CFWS] day-name [CFWS]
+
+ obs-day = [CFWS] 1*2DIGIT [CFWS]
+
+ obs-year = [CFWS] 2*DIGIT [CFWS]
+
+ obs-hour = [CFWS] 2DIGIT [CFWS]
+
+ obs-minute = [CFWS] 2DIGIT [CFWS]
+
+ obs-second = [CFWS] 2DIGIT [CFWS]
+
+ obs-zone = "UT" / "GMT" / ; Universal Time
+ ; North American UT
+ ; offsets
+ "EST" / "EDT" / ; Eastern: - 5/ - 4
+ "CST" / "CDT" / ; Central: - 6/ - 5
+ "MST" / "MDT" / ; Mountain: - 7/ - 6
+ "PST" / "PDT" / ; Pacific: - 8/ - 7
+ ;
+
+
+
+
+Resnick Standards Track [Page 33]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+ %d65-73 / ; Military zones - "A"
+ %d75-90 / ; through "I" and "K"
+ %d97-105 / ; through "Z", both
+ %d107-122 ; upper and lower case
+
+ Where a two or three digit year occurs in a date, the year is to be
+ interpreted as follows: If a two digit year is encountered whose
+ value is between 00 and 49, the year is interpreted by adding 2000,
+ ending up with a value between 2000 and 2049. If a two digit year is
+ encountered with a value between 50 and 99, or any three digit year
+ is encountered, the year is interpreted by adding 1900.
+
+ In the obsolete time zone, "UT" and "GMT" are indications of
+ "Universal Time" and "Greenwich Mean Time", respectively, and are
+ both semantically identical to "+0000".
+
+ The remaining three character zones are the US time zones. The first
+ letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
+ "Mountain", and "Pacific". The second letter is either "S" for
+ "Standard" time, or "D" for "Daylight Savings" (or summer) time.
+ Their interpretations are as follows:
+
+ EDT is semantically equivalent to -0400
+ EST is semantically equivalent to -0500
+ CDT is semantically equivalent to -0500
+ CST is semantically equivalent to -0600
+ MDT is semantically equivalent to -0600
+ MST is semantically equivalent to -0700
+ PDT is semantically equivalent to -0700
+ PST is semantically equivalent to -0800
+
+ The 1 character military time zones were defined in a non-standard
+ way in [RFC0822] and are therefore unpredictable in their meaning.
+ The original definitions of the military zones "A" through "I" are
+ equivalent to "+0100" through "+0900", respectively; "K", "L", and
+ "M" are equivalent to "+1000", "+1100", and "+1200", respectively;
+ "N" through "Y" are equivalent to "-0100" through "-1200".
+ respectively; and "Z" is equivalent to "+0000". However, because of
+ the error in [RFC0822], they SHOULD all be considered equivalent to
+ "-0000" unless there is out-of-band information confirming their
+ meaning.
+
+ Other multi-character (usually between 3 and 5) alphabetic time zones
+ have been used in Internet messages. Any such time zone whose
+ meaning is not known SHOULD be considered equivalent to "-0000"
+ unless there is out-of-band information confirming their meaning.
+
+
+
+
+
+Resnick Standards Track [Page 34]
+\f
+RFC 5322 Internet Message Format October 2008
+
+
+4.4. Obsolete Addressing
+
+ There are four primary differences in addressing. First, mailbox
+ addresses were allowed to have a route portion before the addr-spec
+ when enclosed in "<" and ">". The route is simply a comma-separated
+ list of domain names, each preceded by "@", and the list terminated
+ by a colon. Second, CFWS were allowed between the period-separated
+ elements of local-part and domain (i.e., dot-atom was not used). In
+ addition, local-part is allowed to contain quoted-string in addition
+ to just atom. Third, mailbox-list and address-list were allowed to
+ have "null" members. That is, there could be two or more commas in
+ such a list with nothing in between them, or commas at the beginning
+ or end of the list. Finally, US-ASCII control characters and quoted-
+ pairs were allowed in domain literals and are added here.
+
+ obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
+
+ obs-route = obs-domain-list ":"
+
+ obs-domain-list = *(CFWS / ",") "@" domain
+ *("," [CFWS] ["@" domain])
+
+ obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
+
+ obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
+
+ obs-group-list = 1*([CFWS] ",") [CFWS]
+
+ obs-local-part = word *("." word)
+
+ obs-domain = atom *("." atom)
+
+ obs-dtext = obs-NO-WS-CTL / quoted-pair
+
+ When interpreting addresses, the route portion SHOULD be ignored.
+
+4.5. Obsolete Header Fields
+
+ Syntactically, the primary difference in the obsolete field syntax is
+ that it allows multiple occurrences of any of the fields and they may
+ occur in any order. Also, any amount of white space is allowed
+ before the ":" at the end of the field name.
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 35]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
+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]
+\f
projects / ccan / commitdiff