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2860 lines
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Network Working Group P. Resnick, Editor
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Request for Comments: 2822 QUALCOMM Incorporated
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Obsoletes: 822 April 2001
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Category: Standards Track
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Internet Message Format
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Status of this Memo
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This document specifies an Internet standards track protocol for the
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Internet community, and requests discussion and suggestions for
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improvements. Please refer to the current edition of the "Internet
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Official Protocol Standards" (STD 1) for the standardization state
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and status of this protocol. Distribution of this memo is unlimited.
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Copyright Notice
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Copyright (C) The Internet Society (2001). All Rights Reserved.
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Abstract
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This standard specifies a syntax for text messages that are sent
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between computer users, within the framework of "electronic mail"
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messages. This standard supersedes the one specified in Request For
|
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Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
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Messages", updating it to reflect current practice and incorporating
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incremental changes that were specified in other RFCs.
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Table of Contents
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1. Introduction ............................................... 3
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1.1. Scope .................................................... 3
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1.2. Notational conventions ................................... 4
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1.2.1. Requirements notation .................................. 4
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1.2.2. Syntactic notation ..................................... 4
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1.3. Structure of this document ............................... 4
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2. Lexical Analysis of Messages ............................... 5
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2.1. General Description ...................................... 5
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2.1.1. Line Length Limits ..................................... 6
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2.2. Header Fields ............................................ 7
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2.2.1. Unstructured Header Field Bodies ....................... 7
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2.2.2. Structured Header Field Bodies ......................... 7
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2.2.3. Long Header Fields ..................................... 7
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2.3. Body ..................................................... 8
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3. Syntax ..................................................... 9
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3.1. Introduction ............................................. 9
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3.2. Lexical Tokens ........................................... 9
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Resnick Standards Track [Page 1]
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RFC 2822 Internet Message Format April 2001
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3.2.1. Primitive Tokens ....................................... 9
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3.2.2. Quoted characters ......................................10
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3.2.3. Folding white space and comments .......................11
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3.2.4. Atom ...................................................12
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3.2.5. Quoted strings .........................................13
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3.2.6. Miscellaneous tokens ...................................13
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3.3. Date and Time Specification ..............................14
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3.4. Address Specification ....................................15
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3.4.1. Addr-spec specification ................................16
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3.5 Overall message syntax ....................................17
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3.6. Field definitions ........................................18
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3.6.1. The origination date field .............................20
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3.6.2. Originator fields ......................................21
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3.6.3. Destination address fields .............................22
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3.6.4. Identification fields ..................................23
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3.6.5. Informational fields ...................................26
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3.6.6. Resent fields ..........................................26
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3.6.7. Trace fields ...........................................28
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3.6.8. Optional fields ........................................29
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4. Obsolete Syntax ............................................29
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4.1. Miscellaneous obsolete tokens ............................30
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4.2. Obsolete folding white space .............................31
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4.3. Obsolete Date and Time ...................................31
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4.4. Obsolete Addressing ......................................33
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4.5. Obsolete header fields ...................................33
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4.5.1. Obsolete origination date field ........................34
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4.5.2. Obsolete originator fields .............................34
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4.5.3. Obsolete destination address fields ....................34
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4.5.4. Obsolete identification fields .........................35
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4.5.5. Obsolete informational fields ..........................35
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4.5.6. Obsolete resent fields .................................35
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4.5.7. Obsolete trace fields ..................................36
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4.5.8. Obsolete optional fields ...............................36
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5. Security Considerations ....................................36
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6. Bibliography ...............................................37
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7. Editor's Address ...........................................38
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8. Acknowledgements ...........................................39
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Appendix A. Example messages ..................................41
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A.1. Addressing examples ......................................41
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A.1.1. A message from one person to another with simple
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addressing .............................................41
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A.1.2. Different types of mailboxes ...........................42
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A.1.3. Group addresses ........................................43
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A.2. Reply messages ...........................................43
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A.3. Resent messages ..........................................44
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A.4. Messages with trace fields ...............................46
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A.5. White space, comments, and other oddities ................47
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A.6. Obsoleted forms ..........................................47
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Resnick Standards Track [Page 2]
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RFC 2822 Internet Message Format April 2001
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A.6.1. Obsolete addressing ....................................48
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A.6.2. Obsolete dates .........................................48
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A.6.3. Obsolete white space and comments ......................48
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Appendix B. Differences from earlier standards ................49
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Appendix C. Notices ...........................................50
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Full Copyright Statement ......................................51
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1. Introduction
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1.1. Scope
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||
|
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This standard specifies a syntax for text messages that are sent
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between computer users, within the framework of "electronic mail"
|
||
messages. This standard supersedes the one specified in Request For
|
||
Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
|
||
Messages" [RFC822], updating it to reflect current practice and
|
||
incorporating incremental changes that were specified in other RFCs
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[STD3].
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This standard specifies a syntax only for text messages. In
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particular, it makes no provision for the transmission of images,
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audio, or other sorts of structured data in electronic mail messages.
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There are several extensions published, such as the MIME document
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series [RFC2045, RFC2046, RFC2049], which describe mechanisms for the
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transmission of such data through electronic mail, either by
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extending the syntax provided here or by structuring such messages to
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conform to this syntax. Those mechanisms are outside of the scope of
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this standard.
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In the context of electronic mail, messages are viewed as having an
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envelope and contents. The envelope contains whatever information is
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needed to accomplish transmission and delivery. (See [RFC2821] for a
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discussion of the envelope.) The contents comprise the object to be
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delivered to the recipient. This standard applies only to the format
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and some of the semantics of message contents. It contains no
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specification of the information in the envelope.
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However, some message systems may use information from the contents
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to create the envelope. It is intended that this standard facilitate
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the acquisition of such information by programs.
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This specification is intended as a definition of what message
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content format is to be passed between systems. Though some message
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systems locally store messages in this format (which eliminates the
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need for translation between formats) and others use formats that
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differ from the one specified in this standard, local storage is
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outside of the scope of this standard.
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Resnick Standards Track [Page 3]
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RFC 2822 Internet Message Format April 2001
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Note: This standard is not intended to dictate the internal formats
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used by sites, the specific message system features that they are
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expected to support, or any of the characteristics of user interface
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programs that create or read messages. In addition, this standard
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does not specify an encoding of the characters for either transport
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or storage; that is, it does not specify the number of bits used or
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how those bits are specifically transferred over the wire or stored
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on disk.
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1.2. Notational conventions
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1.2.1. Requirements notation
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This document occasionally uses terms that appear in capital letters.
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When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
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NOT", and "MAY" appear capitalized, they are being used to indicate
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particular requirements of this specification. A discussion of the
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meanings of these terms appears in [RFC2119].
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1.2.2. Syntactic notation
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This standard uses the Augmented Backus-Naur Form (ABNF) notation
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specified in [RFC2234] for the formal definitions of the syntax of
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messages. Characters will be specified either by a decimal value
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(e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
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a case-insensitive literal value enclosed in quotation marks (e.g.,
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"A" for either uppercase or lowercase A). See [RFC2234] for the full
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description of the notation.
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||
|
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1.3. Structure of this document
|
||
|
||
This document is divided into several sections.
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||
|
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This section, section 1, is a short introduction to the document.
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Section 2 lays out the general description of a message and its
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constituent parts. This is an overview to help the reader understand
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some of the general principles used in the later portions of this
|
||
document. Any examples in this section MUST NOT be taken as
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specification of the formal syntax of any part of a message.
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Section 3 specifies formal ABNF rules for the structure of each part
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of a message (the syntax) and describes the relationship between
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those parts and their meaning in the context of a message (the
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semantics). That is, it describes the actual rules for the structure
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of each part of a message (the syntax) as well as a description of
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the parts and instructions on how they ought to be interpreted (the
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semantics). This includes analysis of the syntax and semantics of
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Resnick Standards Track [Page 4]
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RFC 2822 Internet Message Format April 2001
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subparts of messages that have specific structure. The syntax
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included in section 3 represents messages as they MUST be created.
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There are also notes in section 3 to indicate if any of the options
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specified in the syntax SHOULD be used over any of the others.
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Both sections 2 and 3 describe messages that are legal to generate
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for purposes of this standard.
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Section 4 of this document specifies an "obsolete" syntax. There are
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references in section 3 to these obsolete syntactic elements. The
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rules of the obsolete syntax are elements that have appeared in
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earlier revisions of this standard or have previously been widely
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||
used in Internet messages. As such, these elements MUST be
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||
interpreted by parsers of messages in order to be conformant to this
|
||
standard. However, since items in this syntax have been determined
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to be non-interoperable or to cause significant problems for
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recipients of messages, they MUST NOT be generated by creators of
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||
conformant messages.
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||
|
||
Section 5 details security considerations to take into account when
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||
implementing this standard.
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|
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Section 6 is a bibliography of references in this document.
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Section 7 contains the editor's address.
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||
|
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Section 8 contains acknowledgements.
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||
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Appendix A lists examples of different sorts of messages. These
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examples are not exhaustive of the types of messages that appear on
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the Internet, but give a broad overview of certain syntactic forms.
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|
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Appendix B lists the differences between this standard and earlier
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standards for Internet messages.
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Appendix C has copyright and intellectual property notices.
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||
|
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2. Lexical Analysis of Messages
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2.1. General Description
|
||
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||
At the most basic level, a message is a series of characters. A
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message that is conformant with this standard is comprised of
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||
characters with values in the range 1 through 127 and interpreted as
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US-ASCII characters [ASCII]. For brevity, this document sometimes
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refers to this range of characters as simply "US-ASCII characters".
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Resnick Standards Track [Page 5]
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RFC 2822 Internet Message Format April 2001
|
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||
|
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Note: This standard specifies that messages are made up of characters
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||
in the US-ASCII range of 1 through 127. There are other documents,
|
||
specifically the MIME document series [RFC2045, RFC2046, RFC2047,
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||
RFC2048, RFC2049], that extend this standard to allow for values
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outside of that range. Discussion of those mechanisms is not within
|
||
the scope of this standard.
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||
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Messages are divided into lines of characters. A line is a series of
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characters that is delimited with the two characters carriage-return
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and line-feed; that is, the carriage return (CR) character (ASCII
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||
value 13) followed immediately by the line feed (LF) character (ASCII
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value 10). (The carriage-return/line-feed pair is usually written in
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this document as "CRLF".)
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||
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A message consists of header fields (collectively called "the header
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||
of the message") followed, optionally, by a body. The header is a
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sequence of lines of characters with special syntax as defined in
|
||
this standard. The body is simply a sequence of characters that
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follows the header and is separated from the header by an empty line
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(i.e., a line with nothing preceding the CRLF).
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||
|
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2.1.1. Line Length Limits
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||
|
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There are two limits that this standard places on the number of
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characters in a line. Each line of characters MUST be no more than
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998 characters, and SHOULD be no more than 78 characters, excluding
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the CRLF.
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||
|
||
The 998 character limit is due to limitations in many implementations
|
||
which send, receive, or store Internet Message Format messages that
|
||
simply cannot handle more than 998 characters on a line. Receiving
|
||
implementations would do well to handle an arbitrarily large number
|
||
of characters in a line for robustness sake. However, there are so
|
||
many implementations which (in compliance with the transport
|
||
requirements of [RFC2821]) do not accept messages containing more
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than 1000 character including the CR and LF per line, it is important
|
||
for implementations not to create such messages.
|
||
|
||
The more conservative 78 character recommendation is to accommodate
|
||
the many implementations of user interfaces that display these
|
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messages which may truncate, or disastrously wrap, the display of
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more than 78 characters per line, in spite of the fact that such
|
||
implementations are non-conformant to the intent of this
|
||
specification (and that of [RFC2821] if they actually cause
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information to be lost). Again, even though this limitation is put on
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messages, it is encumbant upon implementations which display messages
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Resnick Standards Track [Page 6]
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|
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RFC 2822 Internet Message Format April 2001
|
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|
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|
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to handle an arbitrarily large number of characters in a line
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(certainly at least up to the 998 character limit) for the sake of
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robustness.
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|
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2.2. Header Fields
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Header fields are lines composed of a field name, followed by a colon
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(":"), followed by a field body, and terminated by CRLF. A field
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name MUST be composed of printable US-ASCII characters (i.e.,
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characters that have values between 33 and 126, inclusive), except
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colon. A field body may be composed of any US-ASCII characters,
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except for CR and LF. However, a field body may contain CRLF when
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used in header "folding" and "unfolding" as described in section
|
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2.2.3. All field bodies MUST conform to the syntax described in
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||
sections 3 and 4 of this standard.
|
||
|
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2.2.1. Unstructured Header Field Bodies
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||
|
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Some field bodies in this standard are defined simply as
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||
"unstructured" (which is specified below as any US-ASCII characters,
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except for CR and LF) with no further restrictions. These are
|
||
referred to as unstructured field bodies. Semantically, unstructured
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field bodies are simply to be treated as a single line of characters
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with no further processing (except for header "folding" and
|
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"unfolding" as described in section 2.2.3).
|
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|
||
2.2.2. Structured Header Field Bodies
|
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|
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Some field bodies in this standard have specific syntactical
|
||
structure more restrictive than the unstructured field bodies
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||
described above. These are referred to as "structured" field bodies.
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Structured field bodies are sequences of specific lexical tokens as
|
||
described in sections 3 and 4 of this standard. Many of these tokens
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||
are allowed (according to their syntax) to be introduced or end with
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||
comments (as described in section 3.2.3) as well as the space (SP,
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ASCII value 32) and horizontal tab (HTAB, ASCII value 9) characters
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||
(together known as the white space characters, WSP), and those WSP
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||
characters are subject to header "folding" and "unfolding" as
|
||
described in section 2.2.3. Semantic analysis of structured field
|
||
bodies is given along with their syntax.
|
||
|
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2.2.3. Long Header Fields
|
||
|
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Each header field is logically a single line of characters comprising
|
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the field name, the colon, and the field body. For convenience
|
||
however, and to deal with the 998/78 character limitations per line,
|
||
the field body portion of a header field can be split into a multiple
|
||
line representation; this is called "folding". The general rule is
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 7]
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||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
that wherever this standard allows for folding white space (not
|
||
simply WSP characters), a CRLF may be inserted before any WSP. For
|
||
example, the header field:
|
||
|
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Subject: This is a test
|
||
|
||
can be represented as:
|
||
|
||
Subject: This
|
||
is a test
|
||
|
||
Note: Though structured field bodies are defined in such a way that
|
||
folding can take place between many of the lexical tokens (and even
|
||
within some of the lexical tokens), folding SHOULD be limited to
|
||
placing the CRLF at higher-level syntactic breaks. For instance, if
|
||
a field body is defined as comma-separated values, it is recommended
|
||
that folding occur after the comma separating the structured items in
|
||
preference to other places where the field could be folded, even if
|
||
it is allowed elsewhere.
|
||
|
||
The process of moving from this folded multiple-line representation
|
||
of a header field to its single line representation is called
|
||
"unfolding". Unfolding is accomplished by simply removing any CRLF
|
||
that is immediately followed by WSP. Each header field should be
|
||
treated in its unfolded form for further syntactic and semantic
|
||
evaluation.
|
||
|
||
2.3. Body
|
||
|
||
The body of a message is simply lines of US-ASCII characters. The
|
||
only two limitations on the body are as follows:
|
||
|
||
- CR and LF MUST only occur together as CRLF; they MUST NOT appear
|
||
independently in the body.
|
||
|
||
- Lines of characters in the body MUST be limited to 998 characters,
|
||
and SHOULD be limited to 78 characters, excluding the CRLF.
|
||
|
||
Note: As was stated earlier, there are other standards documents,
|
||
specifically the MIME documents [RFC2045, RFC2046, RFC2048, RFC2049]
|
||
that extend this standard to allow for different sorts of message
|
||
bodies. Again, these mechanisms are beyond the scope of this
|
||
document.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 8]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
3. Syntax
|
||
|
||
3.1. Introduction
|
||
|
||
The syntax as given in this section defines the legal syntax of
|
||
Internet messages. Messages that are conformant to this standard
|
||
MUST conform to the syntax in this section. If there are options in
|
||
this section where one option SHOULD be generated, that is indicated
|
||
either in the prose or in a comment next to the syntax.
|
||
|
||
For the defined expressions, a short description of the syntax and
|
||
use is given, followed by the syntax in ABNF, followed by a semantic
|
||
analysis. Primitive tokens that are used but otherwise unspecified
|
||
come from [RFC2234].
|
||
|
||
In some of the definitions, there will be nonterminals whose names
|
||
start with "obs-". These "obs-" elements refer to tokens defined in
|
||
the obsolete syntax in section 4. In all cases, these productions
|
||
are to be ignored for the purposes of generating legal Internet
|
||
messages and MUST NOT be used as part of such a message. However,
|
||
when interpreting messages, these tokens MUST be honored as part of
|
||
the legal syntax. In this sense, section 3 defines a grammar for
|
||
generation of messages, with "obs-" elements that are to be ignored,
|
||
while section 4 adds grammar for interpretation of messages.
|
||
|
||
3.2. Lexical Tokens
|
||
|
||
The following rules are used to define an underlying lexical
|
||
analyzer, which feeds tokens to the higher-level parsers. This
|
||
section defines the tokens used in structured header field bodies.
|
||
|
||
Note: Readers of this standard need to pay special attention to how
|
||
these lexical tokens are used in both the lower-level and
|
||
higher-level syntax later in the document. Particularly, the white
|
||
space tokens and the comment tokens defined in section 3.2.3 get used
|
||
in the lower-level tokens defined here, and those lower-level tokens
|
||
are in turn used as parts of the higher-level tokens defined later.
|
||
Therefore, the white space and comments may be allowed in the
|
||
higher-level tokens even though they may not explicitly appear in a
|
||
particular definition.
|
||
|
||
3.2.1. Primitive Tokens
|
||
|
||
The following are primitive tokens referred to elsewhere in this
|
||
standard, but not otherwise defined in [RFC2234]. Some of them will
|
||
not appear anywhere else in the syntax, but they are convenient to
|
||
refer to in other parts of this document.
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 9]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Note: The "specials" below are just such an example. Though the
|
||
specials token does not appear anywhere else in this standard, it is
|
||
useful for implementers who use tools that lexically analyze
|
||
messages. Each of the characters in specials can be used to indicate
|
||
a tokenization point in lexical analysis.
|
||
|
||
NO-WS-CTL = %d1-8 / ; US-ASCII control characters
|
||
%d11 / ; that do not include the
|
||
%d12 / ; carriage return, line feed,
|
||
%d14-31 / ; and white space characters
|
||
%d127
|
||
|
||
text = %d1-9 / ; Characters excluding CR and LF
|
||
%d11 /
|
||
%d12 /
|
||
%d14-127 /
|
||
obs-text
|
||
|
||
specials = "(" / ")" / ; Special characters used in
|
||
"<" / ">" / ; other parts of the syntax
|
||
"[" / "]" /
|
||
":" / ";" /
|
||
"@" / "\" /
|
||
"," / "." /
|
||
DQUOTE
|
||
|
||
No special semantics are attached to these tokens. They are simply
|
||
single characters.
|
||
|
||
3.2.2. Quoted characters
|
||
|
||
Some characters are reserved for special interpretation, such as
|
||
delimiting lexical tokens. To permit use of these characters as
|
||
uninterpreted data, a quoting mechanism is provided.
|
||
|
||
quoted-pair = ("\" text) / obs-qp
|
||
|
||
Where any quoted-pair appears, it is to be interpreted as the text
|
||
character alone. That is to say, the "\" character that appears as
|
||
part of a quoted-pair is semantically "invisible".
|
||
|
||
Note: The "\" character may appear in a message where it is not part
|
||
of a quoted-pair. A "\" character that does not appear in a
|
||
quoted-pair is not semantically invisible. The only places in this
|
||
standard where quoted-pair currently appears are ccontent, qcontent,
|
||
dcontent, no-fold-quote, and no-fold-literal.
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 10]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
3.2.3. Folding white space and comments
|
||
|
||
White space characters, including white space used in folding
|
||
(described in section 2.2.3), may appear between many elements in
|
||
header field bodies. Also, strings of characters that are treated as
|
||
comments may be included in structured field bodies as characters
|
||
enclosed in parentheses. The following defines the folding white
|
||
space (FWS) and comment constructs.
|
||
|
||
Strings of characters enclosed in parentheses are considered comments
|
||
so long as they do not appear within a "quoted-string", as defined in
|
||
section 3.2.5. Comments may nest.
|
||
|
||
There are several places in this standard where comments and FWS may
|
||
be freely inserted. To accommodate that syntax, an additional token
|
||
for "CFWS" is defined for places where comments and/or FWS can occur.
|
||
However, where CFWS occurs in this standard, it MUST NOT be inserted
|
||
in such a way that any line of a folded header field is made up
|
||
entirely of WSP characters and nothing else.
|
||
|
||
FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
|
||
obs-FWS
|
||
|
||
ctext = NO-WS-CTL / ; Non white space controls
|
||
|
||
%d33-39 / ; The rest of the US-ASCII
|
||
%d42-91 / ; characters not including "(",
|
||
%d93-126 ; ")", or "\"
|
||
|
||
ccontent = ctext / quoted-pair / comment
|
||
|
||
comment = "(" *([FWS] ccontent) [FWS] ")"
|
||
|
||
CFWS = *([FWS] comment) (([FWS] comment) / FWS)
|
||
|
||
Throughout this standard, where FWS (the folding white space token)
|
||
appears, it indicates a place where header folding, as discussed in
|
||
section 2.2.3, may take place. Wherever header folding appears in a
|
||
message (that is, a header field body containing a CRLF followed by
|
||
any WSP), header unfolding (removal of the CRLF) is performed before
|
||
any further lexical analysis is performed on that header field
|
||
according to this standard. That is to say, any CRLF that appears in
|
||
FWS is semantically "invisible."
|
||
|
||
A comment is normally used in a structured field body to provide some
|
||
human readable informational text. Since a comment is allowed to
|
||
contain FWS, folding is permitted within the comment. Also note that
|
||
since quoted-pair is allowed in a comment, the parentheses and
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 11]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
backslash characters may appear in a comment so long as they appear
|
||
as a quoted-pair. Semantically, the enclosing parentheses are not
|
||
part of the comment; the comment is what is contained between the two
|
||
parentheses. As stated earlier, the "\" in any quoted-pair and the
|
||
CRLF in any FWS that appears within the comment are semantically
|
||
"invisible" and therefore not part of the comment either.
|
||
|
||
Runs of FWS, comment or CFWS that occur between lexical tokens in a
|
||
structured field header are semantically interpreted as a single
|
||
space character.
|
||
|
||
3.2.4. Atom
|
||
|
||
Several productions in structured header field bodies are simply
|
||
strings of certain basic characters. Such productions are called
|
||
atoms.
|
||
|
||
Some of the structured header field bodies also allow the period
|
||
character (".", ASCII value 46) within runs of atext. An additional
|
||
"dot-atom" token is defined for those purposes.
|
||
|
||
atext = ALPHA / DIGIT / ; Any character except controls,
|
||
"!" / "#" / ; SP, and specials.
|
||
"$" / "%" / ; Used for atoms
|
||
"&" / "'" /
|
||
"*" / "+" /
|
||
"-" / "/" /
|
||
"=" / "?" /
|
||
"^" / "_" /
|
||
"`" / "{" /
|
||
"|" / "}" /
|
||
"~"
|
||
|
||
atom = [CFWS] 1*atext [CFWS]
|
||
|
||
dot-atom = [CFWS] dot-atom-text [CFWS]
|
||
|
||
dot-atom-text = 1*atext *("." 1*atext)
|
||
|
||
Both atom and dot-atom are interpreted as a single unit, comprised of
|
||
the string of characters that make it up. Semantically, the optional
|
||
comments and FWS surrounding the rest of the characters are not part
|
||
of the atom; the atom is only the run of atext characters in an atom,
|
||
or the atext and "." characters in a dot-atom.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 12]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
3.2.5. Quoted strings
|
||
|
||
Strings of characters that include characters other than those
|
||
allowed in atoms may be represented in a quoted string format, where
|
||
the characters are surrounded by quote (DQUOTE, ASCII value 34)
|
||
characters.
|
||
|
||
qtext = NO-WS-CTL / ; Non white space controls
|
||
|
||
%d33 / ; The rest of the US-ASCII
|
||
%d35-91 / ; characters not including "\"
|
||
%d93-126 ; or the quote character
|
||
|
||
qcontent = qtext / quoted-pair
|
||
|
||
quoted-string = [CFWS]
|
||
DQUOTE *([FWS] qcontent) [FWS] DQUOTE
|
||
[CFWS]
|
||
|
||
A quoted-string is treated as a unit. That is, quoted-string is
|
||
identical to atom, semantically. Since a quoted-string is allowed to
|
||
contain FWS, folding is permitted. Also note that since quoted-pair
|
||
is allowed in a quoted-string, the quote and backslash characters may
|
||
appear in a quoted-string so long as they appear as a quoted-pair.
|
||
|
||
Semantically, neither the optional CFWS outside of the quote
|
||
characters nor the quote characters themselves are part of the
|
||
quoted-string; the quoted-string is what is contained between the two
|
||
quote characters. As stated earlier, the "\" in any quoted-pair and
|
||
the CRLF in any FWS/CFWS that appears within the quoted-string are
|
||
semantically "invisible" and therefore not part of the quoted-string
|
||
either.
|
||
|
||
3.2.6. Miscellaneous tokens
|
||
|
||
Three additional tokens are defined, word and phrase for combinations
|
||
of atoms and/or quoted-strings, and unstructured for use in
|
||
unstructured header fields and in some places within structured
|
||
header fields.
|
||
|
||
word = atom / quoted-string
|
||
|
||
phrase = 1*word / obs-phrase
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 13]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
utext = NO-WS-CTL / ; Non white space controls
|
||
%d33-126 / ; The rest of US-ASCII
|
||
obs-utext
|
||
|
||
unstructured = *([FWS] utext) [FWS]
|
||
|
||
3.3. Date and Time Specification
|
||
|
||
Date and time occur in several header fields. This section specifies
|
||
the syntax for a full date and time specification. Though folding
|
||
white space is permitted throughout the date-time specification, it
|
||
is RECOMMENDED that a single space be used in each place that FWS
|
||
appears (whether it is required or optional); some older
|
||
implementations may not interpret other occurrences of folding white
|
||
space correctly.
|
||
|
||
date-time = [ day-of-week "," ] date FWS time [CFWS]
|
||
|
||
day-of-week = ([FWS] day-name) / obs-day-of-week
|
||
|
||
day-name = "Mon" / "Tue" / "Wed" / "Thu" /
|
||
"Fri" / "Sat" / "Sun"
|
||
|
||
date = day month year
|
||
|
||
year = 4*DIGIT / obs-year
|
||
|
||
month = (FWS month-name FWS) / obs-month
|
||
|
||
month-name = "Jan" / "Feb" / "Mar" / "Apr" /
|
||
"May" / "Jun" / "Jul" / "Aug" /
|
||
"Sep" / "Oct" / "Nov" / "Dec"
|
||
|
||
day = ([FWS] 1*2DIGIT) / obs-day
|
||
|
||
time = time-of-day FWS zone
|
||
|
||
time-of-day = hour ":" minute [ ":" second ]
|
||
|
||
hour = 2DIGIT / obs-hour
|
||
|
||
minute = 2DIGIT / obs-minute
|
||
|
||
second = 2DIGIT / obs-second
|
||
|
||
zone = (( "+" / "-" ) 4DIGIT) / obs-zone
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 14]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
The day is the numeric day of the month. The year is any numeric
|
||
year 1900 or later.
|
||
|
||
The time-of-day specifies the number of hours, minutes, and
|
||
optionally seconds since midnight of the date indicated.
|
||
|
||
The date and time-of-day SHOULD express local time.
|
||
|
||
The zone specifies the offset from Coordinated Universal Time (UTC,
|
||
formerly referred to as "Greenwich Mean Time") that the date and
|
||
time-of-day represent. The "+" or "-" indicates whether the
|
||
time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
|
||
Universal Time. The first two digits indicate the number of hours
|
||
difference from Universal Time, and the last two digits indicate the
|
||
number of minutes difference from Universal Time. (Hence, +hhmm
|
||
means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
|
||
minutes). The form "+0000" SHOULD be used to indicate a time zone at
|
||
Universal Time. Though "-0000" also indicates Universal Time, it is
|
||
used to indicate that the time was generated on a system that may be
|
||
in a local time zone other than Universal Time and therefore
|
||
indicates that the date-time contains no information about the local
|
||
time zone.
|
||
|
||
A date-time specification MUST be semantically valid. That is, the
|
||
day-of-the-week (if included) MUST be the day implied by the date,
|
||
the numeric day-of-month MUST be between 1 and the number of days
|
||
allowed for the specified month (in the specified year), the
|
||
time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
|
||
number of seconds allowing for a leap second; see [STD12]), and the
|
||
zone MUST be within the range -9959 through +9959.
|
||
|
||
3.4. Address Specification
|
||
|
||
Addresses occur in several message header fields to indicate senders
|
||
and recipients of messages. An address may either be an individual
|
||
mailbox, or a group of mailboxes.
|
||
|
||
address = mailbox / group
|
||
|
||
mailbox = name-addr / addr-spec
|
||
|
||
name-addr = [display-name] angle-addr
|
||
|
||
angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
|
||
|
||
group = display-name ":" [mailbox-list / CFWS] ";"
|
||
[CFWS]
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 15]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
display-name = phrase
|
||
|
||
mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
|
||
|
||
address-list = (address *("," address)) / obs-addr-list
|
||
|
||
A mailbox receives mail. It is a conceptual entity which does not
|
||
necessarily pertain to file storage. For example, some sites may
|
||
choose to print mail on a printer and deliver the output to the
|
||
addressee's desk. Normally, a mailbox is comprised of two parts: (1)
|
||
an optional display name that indicates the name of the recipient
|
||
(which could be a person or a system) that could be displayed to the
|
||
user of a mail application, and (2) an addr-spec address enclosed in
|
||
angle brackets ("<" and ">"). There is also an alternate simple form
|
||
of a mailbox where the addr-spec address appears alone, without the
|
||
recipient's name or the angle brackets. The Internet addr-spec
|
||
address is described in section 3.4.1.
|
||
|
||
Note: Some legacy implementations used the simple form where the
|
||
addr-spec appears without the angle brackets, but included the name
|
||
of the recipient in parentheses as a comment following the addr-spec.
|
||
Since the meaning of the information in a comment is unspecified,
|
||
implementations SHOULD use the full name-addr form of the mailbox,
|
||
instead of the legacy form, to specify the display name associated
|
||
with a mailbox. Also, because some legacy implementations interpret
|
||
the comment, comments generally SHOULD NOT be used in address fields
|
||
to avoid confusing such implementations.
|
||
|
||
When it is desirable to treat several mailboxes as a single unit
|
||
(i.e., in a distribution list), the group construct can be used. The
|
||
group construct allows the sender to indicate a named group of
|
||
recipients. This is done by giving a display name for the group,
|
||
followed by a colon, followed by a comma separated list of any number
|
||
of mailboxes (including zero and one), and ending with a semicolon.
|
||
Because the list of mailboxes can be empty, using the group construct
|
||
is also a simple way to communicate to recipients that the message
|
||
was sent to one or more named sets of recipients, without actually
|
||
providing the individual mailbox address for each of those
|
||
recipients.
|
||
|
||
3.4.1. Addr-spec specification
|
||
|
||
An addr-spec is a specific Internet identifier that contains a
|
||
locally interpreted string followed by the at-sign character ("@",
|
||
ASCII value 64) followed by an Internet domain. The locally
|
||
interpreted string is either a quoted-string or a dot-atom. If the
|
||
string can be represented as a dot-atom (that is, it contains no
|
||
characters other than atext characters or "." surrounded by atext
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 16]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
characters), then the dot-atom form SHOULD be used and the
|
||
quoted-string form SHOULD NOT be used. Comments and folding white
|
||
space SHOULD NOT be used around the "@" in the addr-spec.
|
||
|
||
addr-spec = local-part "@" domain
|
||
|
||
local-part = dot-atom / quoted-string / obs-local-part
|
||
|
||
domain = dot-atom / domain-literal / obs-domain
|
||
|
||
domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
|
||
|
||
dcontent = dtext / quoted-pair
|
||
|
||
dtext = NO-WS-CTL / ; Non white space controls
|
||
|
||
%d33-90 / ; The rest of the US-ASCII
|
||
%d94-126 ; characters not including "[",
|
||
; "]", or "\"
|
||
|
||
The domain portion identifies the point to which the mail is
|
||
delivered. In the dot-atom form, this is interpreted as an Internet
|
||
domain name (either a host name or a mail exchanger name) as
|
||
described in [STD3, STD13, STD14]. In the domain-literal form, the
|
||
domain is interpreted as the literal Internet address of the
|
||
particular host. In both cases, how addressing is used and how
|
||
messages are transported to a particular host is covered in the mail
|
||
transport document [RFC2821]. These mechanisms are outside of the
|
||
scope of this document.
|
||
|
||
The local-part portion is a domain dependent string. In addresses,
|
||
it is simply interpreted on the particular host as a name of a
|
||
particular mailbox.
|
||
|
||
3.5 Overall message syntax
|
||
|
||
A message consists of header fields, optionally followed by a message
|
||
body. Lines in a message MUST be a maximum of 998 characters
|
||
excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
|
||
characters excluding the CRLF. (See section 2.1.1 for explanation.)
|
||
In a message body, though all of the characters listed in the text
|
||
rule MAY be used, the use of US-ASCII control characters (values 1
|
||
through 8, 11, 12, and 14 through 31) is discouraged since their
|
||
interpretation by receivers for display is not guaranteed.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 17]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
message = (fields / obs-fields)
|
||
[CRLF body]
|
||
|
||
body = *(*998text CRLF) *998text
|
||
|
||
The header fields carry most of the semantic information and are
|
||
defined in section 3.6. The body is simply a series of lines of text
|
||
which are uninterpreted for the purposes of this standard.
|
||
|
||
3.6. Field definitions
|
||
|
||
The header fields of a message are defined here. All header fields
|
||
have the same general syntactic structure: A field name, followed by
|
||
a colon, followed by the field body. The specific syntax for each
|
||
header field is defined in the subsequent sections.
|
||
|
||
Note: In the ABNF syntax for each field in subsequent sections, each
|
||
field name is followed by the required colon. However, for brevity
|
||
sometimes the colon is not referred to in the textual description of
|
||
the syntax. It is, nonetheless, required.
|
||
|
||
It is important to note that the header fields are not guaranteed to
|
||
be in a particular order. They may appear in any order, and they
|
||
have been known to be reordered occasionally when transported over
|
||
the Internet. However, for the purposes of this standard, header
|
||
fields SHOULD NOT be reordered when a message is transported or
|
||
transformed. More importantly, the trace header fields and resent
|
||
header fields MUST NOT be reordered, and SHOULD be kept in blocks
|
||
prepended to the message. See sections 3.6.6 and 3.6.7 for more
|
||
information.
|
||
|
||
The only required header fields are the origination date field and
|
||
the originator address field(s). All other header fields are
|
||
syntactically optional. More information is contained in the table
|
||
following this definition.
|
||
|
||
fields = *(trace
|
||
*(resent-date /
|
||
resent-from /
|
||
resent-sender /
|
||
resent-to /
|
||
resent-cc /
|
||
resent-bcc /
|
||
resent-msg-id))
|
||
*(orig-date /
|
||
from /
|
||
sender /
|
||
reply-to /
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 18]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
to /
|
||
cc /
|
||
bcc /
|
||
message-id /
|
||
in-reply-to /
|
||
references /
|
||
subject /
|
||
comments /
|
||
keywords /
|
||
optional-field)
|
||
|
||
The following table indicates limits on the number of times each
|
||
field may occur in a message header as well as any special
|
||
limitations on the use of those fields. An asterisk next to a value
|
||
in the minimum or maximum column indicates that a special restriction
|
||
appears in the Notes column.
|
||
|
||
Field Min number Max number Notes
|
||
|
||
trace 0 unlimited Block prepended - see
|
||
3.6.7
|
||
|
||
resent-date 0* unlimited* One per block, required
|
||
if other resent fields
|
||
present - see 3.6.6
|
||
|
||
resent-from 0 unlimited* One per block - see
|
||
3.6.6
|
||
|
||
resent-sender 0* unlimited* One per block, MUST
|
||
occur with multi-address
|
||
resent-from - see 3.6.6
|
||
|
||
resent-to 0 unlimited* One per block - see
|
||
3.6.6
|
||
|
||
resent-cc 0 unlimited* One per block - see
|
||
3.6.6
|
||
|
||
resent-bcc 0 unlimited* One per block - see
|
||
3.6.6
|
||
|
||
resent-msg-id 0 unlimited* One per block - see
|
||
3.6.6
|
||
|
||
orig-date 1 1
|
||
|
||
from 1 1 See sender and 3.6.2
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 19]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
sender 0* 1 MUST occur with multi-
|
||
address from - see 3.6.2
|
||
|
||
reply-to 0 1
|
||
|
||
to 0 1
|
||
|
||
cc 0 1
|
||
|
||
bcc 0 1
|
||
|
||
message-id 0* 1 SHOULD be present - see
|
||
3.6.4
|
||
|
||
in-reply-to 0* 1 SHOULD occur in some
|
||
replies - see 3.6.4
|
||
|
||
references 0* 1 SHOULD occur in some
|
||
replies - see 3.6.4
|
||
|
||
subject 0 1
|
||
|
||
comments 0 unlimited
|
||
|
||
keywords 0 unlimited
|
||
|
||
optional-field 0 unlimited
|
||
|
||
The exact interpretation of each field is described in subsequent
|
||
sections.
|
||
|
||
3.6.1. The origination date field
|
||
|
||
The origination date field consists of the field name "Date" followed
|
||
by a date-time specification.
|
||
|
||
orig-date = "Date:" date-time CRLF
|
||
|
||
The origination date specifies the date and time at which the creator
|
||
of the message indicated that the message was complete and ready to
|
||
enter the mail delivery system. For instance, this might be the time
|
||
that a user pushes the "send" or "submit" button in an application
|
||
program. In any case, it is specifically not intended to convey the
|
||
time that the message is actually transported, but rather the time at
|
||
which the human or other creator of the message has put the message
|
||
into its final form, ready for transport. (For example, a portable
|
||
computer user who is not connected to a network might queue a message
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 20]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
for delivery. The origination date is intended to contain the date
|
||
and time that the user queued the message, not the time when the user
|
||
connected to the network to send the message.)
|
||
|
||
3.6.2. Originator fields
|
||
|
||
The originator fields of a message consist of the from field, the
|
||
sender field (when applicable), and optionally the reply-to field.
|
||
The from field consists of the field name "From" and a
|
||
comma-separated list of one or more mailbox specifications. If the
|
||
from field contains more than one mailbox specification in the
|
||
mailbox-list, then the sender field, containing the field name
|
||
"Sender" and a single mailbox specification, MUST appear in the
|
||
message. In either case, an optional reply-to field MAY also be
|
||
included, which contains the field name "Reply-To" and a
|
||
comma-separated list of one or more addresses.
|
||
|
||
from = "From:" mailbox-list CRLF
|
||
|
||
sender = "Sender:" mailbox CRLF
|
||
|
||
reply-to = "Reply-To:" address-list CRLF
|
||
|
||
The originator fields indicate the mailbox(es) of the source of the
|
||
message. The "From:" field specifies the author(s) of the message,
|
||
that is, the mailbox(es) of the person(s) or system(s) responsible
|
||
for the writing of the message. The "Sender:" field specifies the
|
||
mailbox of the agent responsible for the actual transmission of the
|
||
message. For example, if a secretary were to send a message for
|
||
another person, the mailbox of the secretary would appear in the
|
||
"Sender:" field and the mailbox of the actual author would appear in
|
||
the "From:" field. If the originator of the message can be indicated
|
||
by a single mailbox and the author and transmitter are identical, the
|
||
"Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
|
||
appear.
|
||
|
||
The originator fields also provide the information required when
|
||
replying to a message. When the "Reply-To:" field is present, it
|
||
indicates the mailbox(es) to which the author of the message suggests
|
||
that replies be sent. In the absence of the "Reply-To:" field,
|
||
replies SHOULD by default be sent to the mailbox(es) specified in the
|
||
"From:" field unless otherwise specified by the person composing the
|
||
reply.
|
||
|
||
In all cases, the "From:" field SHOULD NOT contain any mailbox that
|
||
does not belong to the author(s) of the message. See also section
|
||
3.6.3 for more information on forming the destination addresses for a
|
||
reply.
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 21]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
3.6.3. Destination address fields
|
||
|
||
The destination fields of a message consist of three possible fields,
|
||
each of the same form: The field name, which is either "To", "Cc", or
|
||
"Bcc", followed by a comma-separated list of one or more addresses
|
||
(either mailbox or group syntax).
|
||
|
||
to = "To:" address-list CRLF
|
||
|
||
cc = "Cc:" address-list CRLF
|
||
|
||
bcc = "Bcc:" (address-list / [CFWS]) CRLF
|
||
|
||
The destination fields specify the recipients of the message. Each
|
||
destination field may have one or more addresses, and each of the
|
||
addresses indicate the intended recipients of the message. The only
|
||
difference between the three fields is how each is used.
|
||
|
||
The "To:" field contains the address(es) of the primary recipient(s)
|
||
of the message.
|
||
|
||
The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
|
||
making a copy on a typewriter using carbon paper) contains the
|
||
addresses of others who are to receive the message, though the
|
||
content of the message may not be directed at them.
|
||
|
||
The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
|
||
addresses of recipients of the message whose addresses are not to be
|
||
revealed to other recipients of the message. There are three ways in
|
||
which the "Bcc:" field is used. In the first case, when a message
|
||
containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
|
||
removed even though all of the recipients (including those specified
|
||
in the "Bcc:" field) are sent a copy of the message. In the second
|
||
case, recipients specified in the "To:" and "Cc:" lines each are sent
|
||
a copy of the message with the "Bcc:" line removed as above, but the
|
||
recipients on the "Bcc:" line get a separate copy of the message
|
||
containing a "Bcc:" line. (When there are multiple recipient
|
||
addresses in the "Bcc:" field, some implementations actually send a
|
||
separate copy of the message to each recipient with a "Bcc:"
|
||
containing only the address of that particular recipient.) Finally,
|
||
since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
|
||
sent without any addresses indicating to the recipients that blind
|
||
copies were sent to someone. Which method to use with "Bcc:" fields
|
||
is implementation dependent, but refer to the "Security
|
||
Considerations" section of this document for a discussion of each.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 22]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
When a message is a reply to another message, the mailboxes of the
|
||
authors of the original message (the mailboxes in the "From:" field)
|
||
or mailboxes specified in the "Reply-To:" field (if it exists) MAY
|
||
appear in the "To:" field of the reply since these would normally be
|
||
the primary recipients of the reply. If a reply is sent to a message
|
||
that has destination fields, it is often desirable to send a copy of
|
||
the reply to all of the recipients of the message, in addition to the
|
||
author. When such a reply is formed, addresses in the "To:" and
|
||
"Cc:" fields of the original message MAY appear in the "Cc:" field of
|
||
the reply, since these are normally secondary recipients of the
|
||
reply. If a "Bcc:" field is present in the original message,
|
||
addresses in that field MAY appear in the "Bcc:" field of the reply,
|
||
but SHOULD NOT appear in the "To:" or "Cc:" fields.
|
||
|
||
Note: Some mail applications have automatic reply commands that
|
||
include the destination addresses of the original message in the
|
||
destination addresses of the reply. How those reply commands behave
|
||
is implementation dependent and is beyond the scope of this document.
|
||
In particular, whether or not to include the original destination
|
||
addresses when the original message had a "Reply-To:" field is not
|
||
addressed here.
|
||
|
||
3.6.4. Identification fields
|
||
|
||
Though optional, every message SHOULD have a "Message-ID:" field.
|
||
Furthermore, reply messages SHOULD have "In-Reply-To:" and
|
||
"References:" fields as appropriate, as described below.
|
||
|
||
The "Message-ID:" field contains a single unique message identifier.
|
||
The "References:" and "In-Reply-To:" field each contain one or more
|
||
unique message identifiers, optionally separated by CFWS.
|
||
|
||
The message identifier (msg-id) is similar in syntax to an angle-addr
|
||
construct without the internal CFWS.
|
||
|
||
message-id = "Message-ID:" msg-id CRLF
|
||
|
||
in-reply-to = "In-Reply-To:" 1*msg-id CRLF
|
||
|
||
references = "References:" 1*msg-id CRLF
|
||
|
||
msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
|
||
|
||
id-left = dot-atom-text / no-fold-quote / obs-id-left
|
||
|
||
id-right = dot-atom-text / no-fold-literal / obs-id-right
|
||
|
||
no-fold-quote = DQUOTE *(qtext / quoted-pair) DQUOTE
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 23]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
no-fold-literal = "[" *(dtext / quoted-pair) "]"
|
||
|
||
The "Message-ID:" field provides a unique message identifier that
|
||
refers to a particular version of a particular message. The
|
||
uniqueness of the message identifier is guaranteed by the host that
|
||
generates it (see below). This message identifier is intended to be
|
||
machine readable and not necessarily meaningful to humans. A message
|
||
identifier pertains to exactly one instantiation of a particular
|
||
message; subsequent revisions to the message each receive new message
|
||
identifiers.
|
||
|
||
Note: There are many instances when messages are "changed", but those
|
||
changes do not constitute a new instantiation of that message, and
|
||
therefore the message would not get a new message identifier. For
|
||
example, when messages are introduced into the transport system, they
|
||
are often prepended with additional header fields such as trace
|
||
fields (described in section 3.6.7) and resent fields (described in
|
||
section 3.6.6). The addition of such header fields does not change
|
||
the identity of the message and therefore the original "Message-ID:"
|
||
field is retained. In all cases, it is the meaning that the sender
|
||
of the message wishes to convey (i.e., whether this is the same
|
||
message or a different message) that determines whether or not the
|
||
"Message-ID:" field changes, not any particular syntactic difference
|
||
that appears (or does not appear) in the message.
|
||
|
||
The "In-Reply-To:" and "References:" fields are used when creating a
|
||
reply to a message. They hold the message identifier of the original
|
||
message and the message identifiers of other messages (for example,
|
||
in the case of a reply to a message which was itself a reply). The
|
||
"In-Reply-To:" field may be used to identify the message (or
|
||
messages) to which the new message is a reply, while the
|
||
"References:" field may be used to identify a "thread" of
|
||
conversation.
|
||
|
||
When creating a reply to a message, the "In-Reply-To:" and
|
||
"References:" fields of the resultant message are constructed as
|
||
follows:
|
||
|
||
The "In-Reply-To:" field will contain the contents of the "Message-
|
||
ID:" field of the message to which this one is a reply (the "parent
|
||
message"). If there is more than one parent message, then the "In-
|
||
Reply-To:" field will contain the contents of all of the parents'
|
||
"Message-ID:" fields. If there is no "Message-ID:" field in any of
|
||
the parent messages, then the new message will have no "In-Reply-To:"
|
||
field.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 24]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
The "References:" field will contain the contents of the parent's
|
||
"References:" field (if any) followed by the contents of the parent's
|
||
"Message-ID:" field (if any). If the parent message does not contain
|
||
a "References:" field but does have an "In-Reply-To:" field
|
||
containing a single message identifier, then the "References:" field
|
||
will contain the contents of the parent's "In-Reply-To:" field
|
||
followed by the contents of the parent's "Message-ID:" field (if
|
||
any). If the parent has none of the "References:", "In-Reply-To:",
|
||
or "Message-ID:" fields, then the new message will have no
|
||
"References:" field.
|
||
|
||
Note: Some implementations parse the "References:" field to display
|
||
the "thread of the discussion". These implementations assume that
|
||
each new message is a reply to a single parent and hence that they
|
||
can walk backwards through the "References:" field to find the parent
|
||
of each message listed there. Therefore, trying to form a
|
||
"References:" field for a reply that has multiple parents is
|
||
discouraged and how to do so is not defined in this document.
|
||
|
||
The message identifier (msg-id) itself MUST be a globally unique
|
||
identifier for a message. The generator of the message identifier
|
||
MUST guarantee that the msg-id is unique. There are several
|
||
algorithms that can be used to accomplish this. Since the msg-id has
|
||
a similar syntax to angle-addr (identical except that comments and
|
||
folding white space are not allowed), a good method is to put the
|
||
domain name (or a domain literal IP address) of the host on which the
|
||
message identifier was created on the right hand side of the "@", and
|
||
put a combination of the current absolute date and time along with
|
||
some other currently unique (perhaps sequential) identifier available
|
||
on the system (for example, a process id number) on the left hand
|
||
side. Using a date on the left hand side and a domain name or domain
|
||
literal on the right hand side makes it possible to guarantee
|
||
uniqueness since no two hosts use the same domain name or IP address
|
||
at the same time. Though other algorithms will work, it is
|
||
RECOMMENDED that the right hand side contain some domain identifier
|
||
(either of the host itself or otherwise) such that the generator of
|
||
the message identifier can guarantee the uniqueness of the left hand
|
||
side within the scope of that domain.
|
||
|
||
Semantically, the angle bracket characters are not part of the
|
||
msg-id; the msg-id is what is contained between the two angle bracket
|
||
characters.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 25]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
3.6.5. Informational fields
|
||
|
||
The informational fields are all optional. The "Keywords:" field
|
||
contains a comma-separated list of one or more words or
|
||
quoted-strings. The "Subject:" and "Comments:" fields are
|
||
unstructured fields as defined in section 2.2.1, and therefore may
|
||
contain text or folding white space.
|
||
|
||
subject = "Subject:" unstructured CRLF
|
||
|
||
comments = "Comments:" unstructured CRLF
|
||
|
||
keywords = "Keywords:" phrase *("," phrase) CRLF
|
||
|
||
These three fields are intended to have only human-readable content
|
||
with information about the message. The "Subject:" field is the most
|
||
common and contains a short string identifying the topic of the
|
||
message. When used in a reply, the field body MAY start with the
|
||
string "Re: " (from the Latin "res", in the matter of) followed by
|
||
the contents of the "Subject:" field body of the original message.
|
||
If this is done, only one instance of the literal string "Re: " ought
|
||
to be used since use of other strings or more than one instance can
|
||
lead to undesirable consequences. The "Comments:" field contains any
|
||
additional comments on the text of the body of the message. The
|
||
"Keywords:" field contains a comma-separated list of important words
|
||
and phrases that might be useful for the recipient.
|
||
|
||
3.6.6. Resent fields
|
||
|
||
Resent fields SHOULD be added to any message that is reintroduced by
|
||
a user into the transport system. A separate set of resent fields
|
||
SHOULD be added each time this is done. All of the resent fields
|
||
corresponding to a particular resending of the message SHOULD be
|
||
together. Each new set of resent fields is prepended to the message;
|
||
that is, the most recent set of resent fields appear earlier in the
|
||
message. No other fields in the message are changed when resent
|
||
fields are added.
|
||
|
||
Each of the resent fields corresponds to a particular field elsewhere
|
||
in the syntax. For instance, the "Resent-Date:" field corresponds to
|
||
the "Date:" field and the "Resent-To:" field corresponds to the "To:"
|
||
field. In each case, the syntax for the field body is identical to
|
||
the syntax given previously for the corresponding field.
|
||
|
||
When resent fields are used, the "Resent-From:" and "Resent-Date:"
|
||
fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
|
||
"Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
|
||
identical to "Resent-From:".
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 26]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
resent-date = "Resent-Date:" date-time CRLF
|
||
|
||
resent-from = "Resent-From:" mailbox-list CRLF
|
||
|
||
resent-sender = "Resent-Sender:" mailbox CRLF
|
||
|
||
resent-to = "Resent-To:" address-list CRLF
|
||
|
||
resent-cc = "Resent-Cc:" address-list CRLF
|
||
|
||
resent-bcc = "Resent-Bcc:" (address-list / [CFWS]) CRLF
|
||
|
||
resent-msg-id = "Resent-Message-ID:" msg-id CRLF
|
||
|
||
Resent fields are used to identify a message as having been
|
||
reintroduced into the transport system by a user. The purpose of
|
||
using resent fields is to have the message appear to the final
|
||
recipient as if it were sent directly by the original sender, with
|
||
all of the original fields remaining the same. Each set of resent
|
||
fields correspond to a particular resending event. That is, if a
|
||
message is resent multiple times, each set of resent fields gives
|
||
identifying information for each individual time. Resent fields are
|
||
strictly informational. They MUST NOT be used in the normal
|
||
processing of replies or other such automatic actions on messages.
|
||
|
||
Note: Reintroducing a message into the transport system and using
|
||
resent fields is a different operation from "forwarding".
|
||
"Forwarding" has two meanings: One sense of forwarding is that a mail
|
||
reading program can be told by a user to forward a copy of a message
|
||
to another person, making the forwarded message the body of the new
|
||
message. A forwarded message in this sense does not appear to have
|
||
come from the original sender, but is an entirely new message from
|
||
the forwarder of the message. On the other hand, forwarding is also
|
||
used to mean when a mail transport program gets a message and
|
||
forwards it on to a different destination for final delivery. Resent
|
||
header fields are not intended for use with either type of
|
||
forwarding.
|
||
|
||
The resent originator fields indicate the mailbox of the person(s) or
|
||
system(s) that resent the message. As with the regular originator
|
||
fields, there are two forms: a simple "Resent-From:" form which
|
||
contains the mailbox of the individual doing the resending, and the
|
||
more complex form, when one individual (identified in the
|
||
"Resent-Sender:" field) resends a message on behalf of one or more
|
||
others (identified in the "Resent-From:" field).
|
||
|
||
Note: When replying to a resent message, replies behave just as they
|
||
would with any other message, using the original "From:",
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 27]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
"Reply-To:", "Message-ID:", and other fields. The resent fields are
|
||
only informational and MUST NOT be used in the normal processing of
|
||
replies.
|
||
|
||
The "Resent-Date:" indicates the date and time at which the resent
|
||
message is dispatched by the resender of the message. Like the
|
||
"Date:" field, it is not the date and time that the message was
|
||
actually transported.
|
||
|
||
The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
|
||
identically to the "To:", "Cc:", and "Bcc:" fields respectively,
|
||
except that they indicate the recipients of the resent message, not
|
||
the recipients of the original message.
|
||
|
||
The "Resent-Message-ID:" field provides a unique identifier for the
|
||
resent message.
|
||
|
||
3.6.7. Trace fields
|
||
|
||
The trace fields are a group of header fields consisting of an
|
||
optional "Return-Path:" field, and one or more "Received:" fields.
|
||
The "Return-Path:" header field contains a pair of angle brackets
|
||
that enclose an optional addr-spec. The "Received:" field contains a
|
||
(possibly empty) list of name/value pairs followed by a semicolon and
|
||
a date-time specification. The first item of the name/value pair is
|
||
defined by item-name, and the second item is either an addr-spec, an
|
||
atom, a domain, or a msg-id. Further restrictions may be applied to
|
||
the syntax of the trace fields by standards that provide for their
|
||
use, such as [RFC2821].
|
||
|
||
trace = [return]
|
||
1*received
|
||
|
||
return = "Return-Path:" path CRLF
|
||
|
||
path = ([CFWS] "<" ([CFWS] / addr-spec) ">" [CFWS]) /
|
||
obs-path
|
||
|
||
received = "Received:" name-val-list ";" date-time CRLF
|
||
|
||
name-val-list = [CFWS] [name-val-pair *(CFWS name-val-pair)]
|
||
|
||
name-val-pair = item-name CFWS item-value
|
||
|
||
item-name = ALPHA *(["-"] (ALPHA / DIGIT))
|
||
|
||
item-value = 1*angle-addr / addr-spec /
|
||
atom / domain / msg-id
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 28]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
A full discussion of the Internet mail use of trace fields is
|
||
contained in [RFC2821]. For the purposes of this standard, the trace
|
||
fields are strictly informational, and any formal interpretation of
|
||
them is outside of the scope of this document.
|
||
|
||
3.6.8. Optional fields
|
||
|
||
Fields may appear in messages that are otherwise unspecified in this
|
||
standard. They MUST conform to the syntax of an optional-field.
|
||
This is a field name, made up of the printable US-ASCII characters
|
||
except SP and colon, followed by a colon, followed by any text which
|
||
conforms to unstructured.
|
||
|
||
The field names of any optional-field MUST NOT be identical to any
|
||
field name specified elsewhere in this standard.
|
||
|
||
optional-field = field-name ":" unstructured CRLF
|
||
|
||
field-name = 1*ftext
|
||
|
||
ftext = %d33-57 / ; Any character except
|
||
%d59-126 ; controls, SP, and
|
||
; ":".
|
||
|
||
For the purposes of this standard, any optional field is
|
||
uninterpreted.
|
||
|
||
4. Obsolete Syntax
|
||
|
||
Earlier versions of this standard allowed for different (usually more
|
||
liberal) syntax than is allowed in this version. Also, there have
|
||
been syntactic elements used in messages on the Internet whose
|
||
interpretation have never been documented. Though some of these
|
||
syntactic forms MUST NOT be generated according to the grammar in
|
||
section 3, they MUST be accepted and parsed by a conformant receiver.
|
||
This section documents many of these syntactic elements. Taking the
|
||
grammar in section 3 and adding the definitions presented in this
|
||
section will result in the grammar to use for interpretation of
|
||
messages.
|
||
|
||
Note: This section identifies syntactic forms that any implementation
|
||
MUST reasonably interpret. However, there are certainly Internet
|
||
messages which do not conform to even the additional syntax given in
|
||
this section. The fact that a particular form does not appear in any
|
||
section of this document is not justification for computer programs
|
||
to crash or for malformed data to be irretrievably lost by any
|
||
implementation. To repeat an example, though this document requires
|
||
lines in messages to be no longer than 998 characters, silently
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 29]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
discarding the 999th and subsequent characters in a line without
|
||
warning would still be bad behavior for an implementation. It is up
|
||
to the implementation to deal with messages robustly.
|
||
|
||
One important difference between the obsolete (interpreting) and the
|
||
current (generating) syntax is that in structured header field bodies
|
||
(i.e., between the colon and the CRLF of any structured header
|
||
field), white space characters, including folding white space, and
|
||
comments can be freely inserted between any syntactic tokens. This
|
||
allows many complex forms that have proven difficult for some
|
||
implementations to parse.
|
||
|
||
Another key difference between the obsolete and the current syntax is
|
||
that the rule in section 3.2.3 regarding lines composed entirely of
|
||
white space in comments and folding white space does not apply. See
|
||
the discussion of folding white space in section 4.2 below.
|
||
|
||
Finally, certain characters that were formerly allowed in messages
|
||
appear in this section. The NUL character (ASCII value 0) was once
|
||
allowed, but is no longer for compatibility reasons. CR and LF were
|
||
allowed to appear in messages other than as CRLF; this use is also
|
||
shown here.
|
||
|
||
Other differences in syntax and semantics are noted in the following
|
||
sections.
|
||
|
||
4.1. Miscellaneous obsolete tokens
|
||
|
||
These syntactic elements are used elsewhere in the obsolete syntax or
|
||
in the main syntax. The obs-char and obs-qp elements each add ASCII
|
||
value 0. Bare CR and bare LF are added to obs-text and obs-utext.
|
||
The period character is added to obs-phrase. The obs-phrase-list
|
||
provides for "empty" elements in a comma-separated list of phrases.
|
||
|
||
Note: The "period" (or "full stop") character (".") in obs-phrase is
|
||
not a form that was allowed in earlier versions of this or any other
|
||
standard. Period (nor any other character from specials) was not
|
||
allowed in phrase because it introduced a parsing difficulty
|
||
distinguishing between phrases and portions of an addr-spec (see
|
||
section 4.4). It appears here because the period character is
|
||
currently used in many messages in the display-name portion of
|
||
addresses, especially for initials in names, and therefore must be
|
||
interpreted properly. In the future, period may appear in the
|
||
regular syntax of phrase.
|
||
|
||
obs-qp = "\" (%d0-127)
|
||
|
||
obs-text = *LF *CR *(obs-char *LF *CR)
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 30]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
obs-char = %d0-9 / %d11 / ; %d0-127 except CR and
|
||
%d12 / %d14-127 ; LF
|
||
|
||
obs-utext = obs-text
|
||
|
||
obs-phrase = word *(word / "." / CFWS)
|
||
|
||
obs-phrase-list = phrase / 1*([phrase] [CFWS] "," [CFWS]) [phrase]
|
||
|
||
Bare CR and bare LF appear in messages with two different meanings.
|
||
In many cases, bare CR or bare LF are used improperly instead of CRLF
|
||
to indicate line separators. In other cases, bare CR and bare LF are
|
||
used simply as ASCII control characters with their traditional ASCII
|
||
meanings.
|
||
|
||
4.2. Obsolete folding white space
|
||
|
||
In the obsolete syntax, any amount of folding white space MAY be
|
||
inserted where the obs-FWS rule is allowed. This creates the
|
||
possibility of having two consecutive "folds" in a line, and
|
||
therefore the possibility that a line which makes up a folded header
|
||
field could be composed entirely of white space.
|
||
|
||
obs-FWS = 1*WSP *(CRLF 1*WSP)
|
||
|
||
4.3. Obsolete Date and Time
|
||
|
||
The syntax for the obsolete date format allows a 2 digit year in the
|
||
date field and allows for a list of alphabetic time zone
|
||
specifications that were used in earlier versions of this standard.
|
||
It also permits comments and folding white space between many of the
|
||
tokens.
|
||
|
||
obs-day-of-week = [CFWS] day-name [CFWS]
|
||
|
||
obs-year = [CFWS] 2*DIGIT [CFWS]
|
||
|
||
obs-month = CFWS month-name CFWS
|
||
|
||
obs-day = [CFWS] 1*2DIGIT [CFWS]
|
||
|
||
obs-hour = [CFWS] 2DIGIT [CFWS]
|
||
|
||
obs-minute = [CFWS] 2DIGIT [CFWS]
|
||
|
||
obs-second = [CFWS] 2DIGIT [CFWS]
|
||
|
||
obs-zone = "UT" / "GMT" / ; Universal Time
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 31]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
; North American UT
|
||
; offsets
|
||
"EST" / "EDT" / ; Eastern: - 5/ - 4
|
||
"CST" / "CDT" / ; Central: - 6/ - 5
|
||
"MST" / "MDT" / ; Mountain: - 7/ - 6
|
||
"PST" / "PDT" / ; Pacific: - 8/ - 7
|
||
|
||
%d65-73 / ; Military zones - "A"
|
||
%d75-90 / ; through "I" and "K"
|
||
%d97-105 / ; through "Z", both
|
||
%d107-122 ; upper and lower case
|
||
|
||
Where a two or three digit year occurs in a date, the year is to be
|
||
interpreted as follows: If a two digit year is encountered whose
|
||
value is between 00 and 49, the year is interpreted by adding 2000,
|
||
ending up with a value between 2000 and 2049. If a two digit year is
|
||
encountered with a value between 50 and 99, or any three digit year
|
||
is encountered, the year is interpreted by adding 1900.
|
||
|
||
In the obsolete time zone, "UT" and "GMT" are indications of
|
||
"Universal Time" and "Greenwich Mean Time" respectively and are both
|
||
semantically identical to "+0000".
|
||
|
||
The remaining three character zones are the US time zones. The first
|
||
letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
|
||
"Mountain" and "Pacific". The second letter is either "S" for
|
||
"Standard" time, or "D" for "Daylight" (or summer) time. Their
|
||
interpretations are as follows:
|
||
|
||
EDT is semantically equivalent to -0400
|
||
EST is semantically equivalent to -0500
|
||
CDT is semantically equivalent to -0500
|
||
CST is semantically equivalent to -0600
|
||
MDT is semantically equivalent to -0600
|
||
MST is semantically equivalent to -0700
|
||
PDT is semantically equivalent to -0700
|
||
PST is semantically equivalent to -0800
|
||
|
||
The 1 character military time zones were defined in a non-standard
|
||
way in [RFC822] and are therefore unpredictable in their meaning.
|
||
The original definitions of the military zones "A" through "I" are
|
||
equivalent to "+0100" through "+0900" respectively; "K", "L", and "M"
|
||
are equivalent to "+1000", "+1100", and "+1200" respectively; "N"
|
||
through "Y" are equivalent to "-0100" through "-1200" respectively;
|
||
and "Z" is equivalent to "+0000". However, because of the error in
|
||
[RFC822], they SHOULD all be considered equivalent to "-0000" unless
|
||
there is out-of-band information confirming their meaning.
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 32]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Other multi-character (usually between 3 and 5) alphabetic time zones
|
||
have been used in Internet messages. Any such time zone whose
|
||
meaning is not known SHOULD be considered equivalent to "-0000"
|
||
unless there is out-of-band information confirming their meaning.
|
||
|
||
4.4. Obsolete Addressing
|
||
|
||
There are three primary differences in addressing. First, mailbox
|
||
addresses were allowed to have a route portion before the addr-spec
|
||
when enclosed in "<" and ">". The route is simply a comma-separated
|
||
list of domain names, each preceded by "@", and the list terminated
|
||
by a colon. Second, CFWS were allowed between the period-separated
|
||
elements of local-part and domain (i.e., dot-atom was not used). In
|
||
addition, local-part is allowed to contain quoted-string in addition
|
||
to just atom. Finally, mailbox-list and address-list were allowed to
|
||
have "null" members. That is, there could be two or more commas in
|
||
such a list with nothing in between them.
|
||
|
||
obs-angle-addr = [CFWS] "<" [obs-route] addr-spec ">" [CFWS]
|
||
|
||
obs-route = [CFWS] obs-domain-list ":" [CFWS]
|
||
|
||
obs-domain-list = "@" domain *(*(CFWS / "," ) [CFWS] "@" domain)
|
||
|
||
obs-local-part = word *("." word)
|
||
|
||
obs-domain = atom *("." atom)
|
||
|
||
obs-mbox-list = 1*([mailbox] [CFWS] "," [CFWS]) [mailbox]
|
||
|
||
obs-addr-list = 1*([address] [CFWS] "," [CFWS]) [address]
|
||
|
||
When interpreting addresses, the route portion SHOULD be ignored.
|
||
|
||
4.5. Obsolete header fields
|
||
|
||
Syntactically, the primary difference in the obsolete field syntax is
|
||
that it allows multiple occurrences of any of the fields and they may
|
||
occur in any order. Also, any amount of white space is allowed
|
||
before the ":" at the end of the field name.
|
||
|
||
obs-fields = *(obs-return /
|
||
obs-received /
|
||
obs-orig-date /
|
||
obs-from /
|
||
obs-sender /
|
||
obs-reply-to /
|
||
obs-to /
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 33]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
obs-cc /
|
||
obs-bcc /
|
||
obs-message-id /
|
||
obs-in-reply-to /
|
||
obs-references /
|
||
obs-subject /
|
||
obs-comments /
|
||
obs-keywords /
|
||
obs-resent-date /
|
||
obs-resent-from /
|
||
obs-resent-send /
|
||
obs-resent-rply /
|
||
obs-resent-to /
|
||
obs-resent-cc /
|
||
obs-resent-bcc /
|
||
obs-resent-mid /
|
||
obs-optional)
|
||
|
||
Except for destination address fields (described in section 4.5.3),
|
||
the interpretation of multiple occurrences of fields is unspecified.
|
||
Also, the interpretation of trace fields and resent fields which do
|
||
not occur in blocks prepended to the message is unspecified as well.
|
||
Unless otherwise noted in the following sections, interpretation of
|
||
other fields is identical to the interpretation of their non-obsolete
|
||
counterparts in section 3.
|
||
|
||
4.5.1. Obsolete origination date field
|
||
|
||
obs-orig-date = "Date" *WSP ":" date-time CRLF
|
||
|
||
4.5.2. Obsolete originator fields
|
||
|
||
obs-from = "From" *WSP ":" mailbox-list CRLF
|
||
|
||
obs-sender = "Sender" *WSP ":" mailbox CRLF
|
||
|
||
obs-reply-to = "Reply-To" *WSP ":" mailbox-list CRLF
|
||
|
||
4.5.3. Obsolete destination address fields
|
||
|
||
obs-to = "To" *WSP ":" address-list CRLF
|
||
|
||
obs-cc = "Cc" *WSP ":" address-list CRLF
|
||
|
||
obs-bcc = "Bcc" *WSP ":" (address-list / [CFWS]) CRLF
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 34]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
When multiple occurrences of destination address fields occur in a
|
||
message, they SHOULD be treated as if the address-list in the first
|
||
occurrence of the field is combined with the address lists of the
|
||
subsequent occurrences by adding a comma and concatenating.
|
||
|
||
4.5.4. Obsolete identification fields
|
||
|
||
The obsolete "In-Reply-To:" and "References:" fields differ from the
|
||
current syntax in that they allow phrase (words or quoted strings) to
|
||
appear. The obsolete forms of the left and right sides of msg-id
|
||
allow interspersed CFWS, making them syntactically identical to
|
||
local-part and domain respectively.
|
||
|
||
obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
|
||
|
||
obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
|
||
|
||
obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
|
||
|
||
obs-id-left = local-part
|
||
|
||
obs-id-right = domain
|
||
|
||
For purposes of interpretation, the phrases in the "In-Reply-To:" and
|
||
"References:" fields are ignored.
|
||
|
||
Semantically, none of the optional CFWS surrounding the local-part
|
||
and the domain are part of the obs-id-left and obs-id-right
|
||
respectively.
|
||
|
||
4.5.5. Obsolete informational fields
|
||
|
||
obs-subject = "Subject" *WSP ":" unstructured CRLF
|
||
|
||
obs-comments = "Comments" *WSP ":" unstructured CRLF
|
||
|
||
obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
|
||
|
||
4.5.6. Obsolete resent fields
|
||
|
||
The obsolete syntax adds a "Resent-Reply-To:" field, which consists
|
||
of the field name, the optional comments and folding white space, the
|
||
colon, and a comma separated list of addresses.
|
||
|
||
obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
|
||
|
||
obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 35]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
|
||
|
||
obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
|
||
|
||
obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
|
||
|
||
obs-resent-bcc = "Resent-Bcc" *WSP ":"
|
||
(address-list / [CFWS]) CRLF
|
||
|
||
obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
|
||
|
||
obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
|
||
|
||
As with other resent fields, the "Resent-Reply-To:" field is to be
|
||
treated as trace information only.
|
||
|
||
4.5.7. Obsolete trace fields
|
||
|
||
The obs-return and obs-received are again given here as template
|
||
definitions, just as return and received are in section 3. Their
|
||
full syntax is given in [RFC2821].
|
||
|
||
obs-return = "Return-Path" *WSP ":" path CRLF
|
||
|
||
obs-received = "Received" *WSP ":" name-val-list CRLF
|
||
|
||
obs-path = obs-angle-addr
|
||
|
||
4.5.8. Obsolete optional fields
|
||
|
||
obs-optional = field-name *WSP ":" unstructured CRLF
|
||
|
||
5. Security Considerations
|
||
|
||
Care needs to be taken when displaying messages on a terminal or
|
||
terminal emulator. Powerful terminals may act on escape sequences
|
||
and other combinations of ASCII control characters with a variety of
|
||
consequences. They can remap the keyboard or permit other
|
||
modifications to the terminal which could lead to denial of service
|
||
or even damaged data. They can trigger (sometimes programmable)
|
||
answerback messages which can allow a message to cause commands to be
|
||
issued on the recipient's behalf. They can also effect the operation
|
||
of terminal attached devices such as printers. Message viewers may
|
||
wish to strip potentially dangerous terminal escape sequences from
|
||
the message prior to display. However, other escape sequences appear
|
||
in messages for useful purposes (cf. [RFC2045, RFC2046, RFC2047,
|
||
RFC2048, RFC2049, ISO2022]) and therefore should not be stripped
|
||
indiscriminately.
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 36]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Transmission of non-text objects in messages raises additional
|
||
security issues. These issues are discussed in [RFC2045, RFC2046,
|
||
RFC2047, RFC2048, RFC2049].
|
||
|
||
Many implementations use the "Bcc:" (blind carbon copy) field
|
||
described in section 3.6.3 to facilitate sending messages to
|
||
recipients without revealing the addresses of one or more of the
|
||
addressees to the other recipients. Mishandling this use of "Bcc:"
|
||
has implications for confidential information that might be revealed,
|
||
which could eventually lead to security problems through knowledge of
|
||
even the existence of a particular mail address. For example, if
|
||
using the first method described in section 3.6.3, where the "Bcc:"
|
||
line is removed from the message, blind recipients have no explicit
|
||
indication that they have been sent a blind copy, except insofar as
|
||
their address does not appear in the message header. Because of
|
||
this, one of the blind addressees could potentially send a reply to
|
||
all of the shown recipients and accidentally reveal that the message
|
||
went to the blind recipient. When the second method from section
|
||
3.6.3 is used, the blind recipient's address appears in the "Bcc:"
|
||
field of a separate copy of the message. If the "Bcc:" field sent
|
||
contains all of the blind addressees, all of the "Bcc:" recipients
|
||
will be seen by each "Bcc:" recipient. Even if a separate message is
|
||
sent to each "Bcc:" recipient with only the individual's address,
|
||
implementations still need to be careful to process replies to the
|
||
message as per section 3.6.3 so as not to accidentally reveal the
|
||
blind recipient to other recipients.
|
||
|
||
6. Bibliography
|
||
|
||
[ASCII] American National Standards Institute (ANSI), Coded
|
||
Character Set - 7-Bit American National Standard Code for
|
||
Information Interchange, ANSI X3.4, 1986.
|
||
|
||
[ISO2022] International Organization for Standardization (ISO),
|
||
Information processing - ISO 7-bit and 8-bit coded
|
||
character sets - Code extension techniques, Third edition
|
||
- 1986-05-01, ISO 2022, 1986.
|
||
|
||
[RFC822] Crocker, D., "Standard for the Format of ARPA Internet
|
||
Text Messages", RFC 822, August 1982.
|
||
|
||
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
|
||
Extensions (MIME) Part One: Format of Internet Message
|
||
Bodies", RFC 2045, November 1996.
|
||
|
||
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
|
||
Extensions (MIME) Part Two: Media Types", RFC 2046,
|
||
November 1996.
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 37]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
[RFC2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
|
||
Part Three: Message Header Extensions for Non-ASCII Text",
|
||
RFC 2047, November 1996.
|
||
|
||
[RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
|
||
Internet Mail Extensions (MIME) Part Four: Format of
|
||
Internet Message Bodies", RFC 2048, November 1996.
|
||
|
||
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
|
||
Extensions (MIME) Part Five: Conformance Criteria and
|
||
Examples", RFC 2049, November 1996.
|
||
|
||
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
|
||
Requirement Levels", BCP 14, RFC 2119, March 1997.
|
||
|
||
[RFC2234] Crocker, D., Editor, and P. Overell, "Augmented BNF for
|
||
Syntax Specifications: ABNF", RFC 2234, November 1997.
|
||
|
||
[RFC2821] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
|
||
2821, March 2001.
|
||
|
||
[STD3] Braden, R., "Host Requirements", STD 3, RFC 1122 and RFC
|
||
1123, October 1989.
|
||
|
||
[STD12] Mills, D., "Network Time Protocol", STD 12, RFC 1119,
|
||
September 1989.
|
||
|
||
[STD13] Mockapetris, P., "Domain Name System", STD 13, RFC 1034
|
||
and RFC 1035, November 1987.
|
||
|
||
[STD14] Partridge, C., "Mail Routing and the Domain System", STD
|
||
14, RFC 974, January 1986.
|
||
|
||
7. Editor's Address
|
||
|
||
Peter W. Resnick
|
||
QUALCOMM Incorporated
|
||
5775 Morehouse Drive
|
||
San Diego, CA 92121-1714
|
||
USA
|
||
|
||
Phone: +1 858 651 4478
|
||
Fax: +1 858 651 1102
|
||
EMail: presnick@qualcomm.com
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 38]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
8. Acknowledgements
|
||
|
||
Many people contributed to this document. They included folks who
|
||
participated in the Detailed Revision and Update of Messaging
|
||
Standards (DRUMS) Working Group of the Internet Engineering Task
|
||
Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
|
||
people who simply sent their comments in via e-mail. The editor is
|
||
deeply indebted to them all and thanks them sincerely. The below
|
||
list includes everyone who sent e-mail concerning this document.
|
||
Hopefully, everyone who contributed is named here:
|
||
|
||
Matti Aarnio Barry Finkel Larry Masinter
|
||
Tanaka Akira Erik Forsberg Denis McKeon
|
||
Russ Allbery Chuck Foster William P McQuillan
|
||
Eric Allman Paul Fox Alexey Melnikov
|
||
Harald Tveit Alvestrand Klaus M. Frank Perry E. Metzger
|
||
Ran Atkinson Ned Freed Steven Miller
|
||
Jos Backus Jochen Friedrich Keith Moore
|
||
Bruce Balden Randall C. Gellens John Gardiner Myers
|
||
Dave Barr Sukvinder Singh Gill Chris Newman
|
||
Alan Barrett Tim Goodwin John W. Noerenberg
|
||
John Beck Philip Guenther Eric Norman
|
||
J. Robert von Behren Tony Hansen Mike O'Dell
|
||
Jos den Bekker John Hawkinson Larry Osterman
|
||
D. J. Bernstein Philip Hazel Paul Overell
|
||
James Berriman Kai Henningsen Jacob Palme
|
||
Norbert Bollow Robert Herriot Michael A. Patton
|
||
Raj Bose Paul Hethmon Uzi Paz
|
||
Antony Bowesman Jim Hill Michael A. Quinlan
|
||
Scott Bradner Paul E. Hoffman Eric S. Raymond
|
||
Randy Bush Steve Hole Sam Roberts
|
||
Tom Byrer Kari Hurtta Hugh Sasse
|
||
Bruce Campbell Marco S. Hyman Bart Schaefer
|
||
Larry Campbell Ofer Inbar Tom Scola
|
||
W. J. Carpenter Olle Jarnefors Wolfgang Segmuller
|
||
Michael Chapman Kevin Johnson Nick Shelness
|
||
Richard Clayton Sudish Joseph John Stanley
|
||
Maurizio Codogno Maynard Kang Einar Stefferud
|
||
Jim Conklin Prabhat Keni Jeff Stephenson
|
||
R. Kelley Cook John C. Klensin Bernard Stern
|
||
Steve Coya Graham Klyne Peter Sylvester
|
||
Mark Crispin Brad Knowles Mark Symons
|
||
Dave Crocker Shuhei Kobayashi Eric Thomas
|
||
Matt Curtin Peter Koch Lee Thompson
|
||
Michael D'Errico Dan Kohn Karel De Vriendt
|
||
Cyrus Daboo Christian Kuhtz Matthew Wall
|
||
Jutta Degener Anand Kumria Rolf Weber
|
||
Mark Delany Steen Larsen Brent B. Welch
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 39]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Steve Dorner Eliot Lear Dan Wing
|
||
Harold A. Driscoll Barry Leiba Jack De Winter
|
||
Michael Elkins Jay Levitt Gregory J. Woodhouse
|
||
Robert Elz Lars-Johan Liman Greg A. Woods
|
||
Johnny Eriksson Charles Lindsey Kazu Yamamoto
|
||
Erik E. Fair Pete Loshin Alain Zahm
|
||
Roger Fajman Simon Lyall Jamie Zawinski
|
||
Patrik Faltstrom Bill Manning Timothy S. Zurcher
|
||
Claus Andre Farber John Martin
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 40]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Appendix A. Example messages
|
||
|
||
This section presents a selection of messages. These are intended to
|
||
assist in the implementation of this standard, but should not be
|
||
taken as normative; that is to say, although the examples in this
|
||
section were carefully reviewed, if there happens to be a conflict
|
||
between these examples and the syntax described in sections 3 and 4
|
||
of this document, the syntax in those sections is to be taken as
|
||
correct.
|
||
|
||
Messages are delimited in this section between lines of "----". The
|
||
"----" lines are not part of the message itself.
|
||
|
||
A.1. Addressing examples
|
||
|
||
The following are examples of messages that might be sent between two
|
||
individuals.
|
||
|
||
A.1.1. A message from one person to another with simple addressing
|
||
|
||
This could be called a canonical message. It has a single author,
|
||
John Doe, a single recipient, Mary Smith, a subject, the date, a
|
||
message identifier, and a textual message in the body.
|
||
|
||
----
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 41]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
If John's secretary Michael actually sent the message, though John
|
||
was the author and replies to this message should go back to him, the
|
||
sender field would be used:
|
||
|
||
----
|
||
From: John Doe <jdoe@machine.example>
|
||
Sender: Michael Jones <mjones@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
A.1.2. Different types of mailboxes
|
||
|
||
This message includes multiple addresses in the destination fields
|
||
and also uses several different forms of addresses.
|
||
|
||
----
|
||
From: "Joe Q. Public" <john.q.public@example.com>
|
||
To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
|
||
Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
|
||
Date: Tue, 1 Jul 2003 10:52:37 +0200
|
||
Message-ID: <5678.21-Nov-1997@example.com>
|
||
|
||
Hi everyone.
|
||
----
|
||
|
||
Note that the display names for Joe Q. Public and Giant; "Big" Box
|
||
needed to be enclosed in double-quotes because the former contains
|
||
the period and the latter contains both semicolon and double-quote
|
||
characters (the double-quote characters appearing as quoted-pair
|
||
construct). Conversely, the display name for Who? could appear
|
||
without them because the question mark is legal in an atom. Notice
|
||
also that jdoe@example.org and boss@nil.test have no display names
|
||
associated with them at all, and jdoe@example.org uses the simpler
|
||
address form without the angle brackets.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 42]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
A.1.3. Group addresses
|
||
|
||
----
|
||
From: Pete <pete@silly.example>
|
||
To: A Group:Chris Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
|
||
Cc: Undisclosed recipients:;
|
||
Date: Thu, 13 Feb 1969 23:32:54 -0330
|
||
Message-ID: <testabcd.1234@silly.example>
|
||
|
||
Testing.
|
||
----
|
||
|
||
In this message, the "To:" field has a single group recipient named A
|
||
Group which contains 3 addresses, and a "Cc:" field with an empty
|
||
group recipient named Undisclosed recipients.
|
||
|
||
A.2. Reply messages
|
||
|
||
The following is a series of three messages that make up a
|
||
conversation thread between John and Mary. John firsts sends a
|
||
message to Mary, Mary then replies to John's message, and then John
|
||
replies to Mary's reply message.
|
||
|
||
Note especially the "Message-ID:", "References:", and "In-Reply-To:"
|
||
fields in each message.
|
||
|
||
----
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 43]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
When sending replies, the Subject field is often retained, though
|
||
prepended with "Re: " as described in section 3.6.5.
|
||
|
||
----
|
||
From: Mary Smith <mary@example.net>
|
||
To: John Doe <jdoe@machine.example>
|
||
Reply-To: "Mary Smith: Personal Account" <smith@home.example>
|
||
Subject: Re: Saying Hello
|
||
Date: Fri, 21 Nov 1997 10:01:10 -0600
|
||
Message-ID: <3456@example.net>
|
||
In-Reply-To: <1234@local.machine.example>
|
||
References: <1234@local.machine.example>
|
||
|
||
This is a reply to your hello.
|
||
----
|
||
|
||
Note the "Reply-To:" field in the above message. When John replies
|
||
to Mary's message above, the reply should go to the address in the
|
||
"Reply-To:" field instead of the address in the "From:" field.
|
||
|
||
----
|
||
To: "Mary Smith: Personal Account" <smith@home.example>
|
||
From: John Doe <jdoe@machine.example>
|
||
Subject: Re: Saying Hello
|
||
Date: Fri, 21 Nov 1997 11:00:00 -0600
|
||
Message-ID: <abcd.1234@local.machine.tld>
|
||
In-Reply-To: <3456@example.net>
|
||
References: <1234@local.machine.example> <3456@example.net>
|
||
|
||
This is a reply to your reply.
|
||
----
|
||
|
||
A.3. Resent messages
|
||
|
||
Start with the message that has been used as an example several
|
||
times:
|
||
|
||
----
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 44]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Say that Mary, upon receiving this message, wishes to send a copy of
|
||
the message to Jane such that (a) the message would appear to have
|
||
come straight from John; (b) if Jane replies to the message, the
|
||
reply should go back to John; and (c) all of the original
|
||
information, like the date the message was originally sent to Mary,
|
||
the message identifier, and the original addressee, is preserved. In
|
||
this case, resent fields are prepended to the message:
|
||
|
||
----
|
||
Resent-From: Mary Smith <mary@example.net>
|
||
Resent-To: Jane Brown <j-brown@other.example>
|
||
Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
|
||
Resent-Message-ID: <78910@example.net>
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
If Jane, in turn, wished to resend this message to another person,
|
||
she would prepend her own set of resent header fields to the above
|
||
and send that.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 45]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
A.4. Messages with trace fields
|
||
|
||
As messages are sent through the transport system as described in
|
||
[RFC2821], trace fields are prepended to the message. The following
|
||
is an example of what those trace fields might look like. Note that
|
||
there is some folding white space in the first one since these lines
|
||
can be long.
|
||
|
||
----
|
||
Received: from x.y.test
|
||
by example.net
|
||
via TCP
|
||
with ESMTP
|
||
id ABC12345
|
||
for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
|
||
Received: from machine.example by x.y.test; 21 Nov 1997 10:01:22 -0600
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: Fri, 21 Nov 1997 09:55:06 -0600
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 46]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
A.5. White space, comments, and other oddities
|
||
|
||
White space, including folding white space, and comments can be
|
||
inserted between many of the tokens of fields. Taking the example
|
||
from A.1.3, white space and comments can be inserted into all of the
|
||
fields.
|
||
|
||
----
|
||
From: Pete(A wonderful \) chap) <pete(his account)@silly.test(his host)>
|
||
To:A Group(Some people)
|
||
:Chris Jones <c@(Chris's host.)public.example>,
|
||
joe@example.org,
|
||
John <jdoe@one.test> (my dear friend); (the end of the group)
|
||
Cc:(Empty list)(start)Undisclosed recipients :(nobody(that I know)) ;
|
||
Date: Thu,
|
||
13
|
||
Feb
|
||
1969
|
||
23:32
|
||
-0330 (Newfoundland Time)
|
||
Message-ID: <testabcd.1234@silly.test>
|
||
|
||
Testing.
|
||
----
|
||
|
||
The above example is aesthetically displeasing, but perfectly legal.
|
||
Note particularly (1) the comments in the "From:" field (including
|
||
one that has a ")" character appearing as part of a quoted-pair); (2)
|
||
the white space absent after the ":" in the "To:" field as well as
|
||
the comment and folding white space after the group name, the special
|
||
character (".") in the comment in Chris Jones's address, and the
|
||
folding white space before and after "joe@example.org,"; (3) the
|
||
multiple and nested comments in the "Cc:" field as well as the
|
||
comment immediately following the ":" after "Cc"; (4) the folding
|
||
white space (but no comments except at the end) and the missing
|
||
seconds in the time of the date field; and (5) the white space before
|
||
(but not within) the identifier in the "Message-ID:" field.
|
||
|
||
A.6. Obsoleted forms
|
||
|
||
The following are examples of obsolete (that is, the "MUST NOT
|
||
generate") syntactic elements described in section 4 of this
|
||
document.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 47]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
A.6.1. Obsolete addressing
|
||
|
||
Note in the below example the lack of quotes around Joe Q. Public,
|
||
the route that appears in the address for Mary Smith, the two commas
|
||
that appear in the "To:" field, and the spaces that appear around the
|
||
"." in the jdoe address.
|
||
|
||
----
|
||
From: Joe Q. Public <john.q.public@example.com>
|
||
To: Mary Smith <@machine.tld:mary@example.net>, , jdoe@test . example
|
||
Date: Tue, 1 Jul 2003 10:52:37 +0200
|
||
Message-ID: <5678.21-Nov-1997@example.com>
|
||
|
||
Hi everyone.
|
||
----
|
||
|
||
A.6.2. Obsolete dates
|
||
|
||
The following message uses an obsolete date format, including a non-
|
||
numeric time zone and a two digit year. Note that although the
|
||
day-of-week is missing, that is not specific to the obsolete syntax;
|
||
it is optional in the current syntax as well.
|
||
|
||
----
|
||
From: John Doe <jdoe@machine.example>
|
||
To: Mary Smith <mary@example.net>
|
||
Subject: Saying Hello
|
||
Date: 21 Nov 97 09:55:06 GMT
|
||
Message-ID: <1234@local.machine.example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
A.6.3. Obsolete white space and comments
|
||
|
||
White space and comments can appear between many more elements than
|
||
in the current syntax. Also, folding lines that are made up entirely
|
||
of white space are legal.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 48]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
----
|
||
From : John Doe <jdoe@machine(comment). example>
|
||
To : Mary Smith
|
||
__
|
||
<mary@example.net>
|
||
Subject : Saying Hello
|
||
Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
|
||
Message-ID : <1234 @ local(blah) .machine .example>
|
||
|
||
This is a message just to say hello.
|
||
So, "Hello".
|
||
----
|
||
|
||
Note especially the second line of the "To:" field. It starts with
|
||
two space characters. (Note that "__" represent blank spaces.)
|
||
Therefore, it is considered part of the folding as described in
|
||
section 4.2. Also, the comments and white space throughout
|
||
addresses, dates, and message identifiers are all part of the
|
||
obsolete syntax.
|
||
|
||
Appendix B. Differences from earlier standards
|
||
|
||
This appendix contains a list of changes that have been made in the
|
||
Internet Message Format from earlier standards, specifically [RFC822]
|
||
and [STD3]. Items marked with an asterisk (*) below are items which
|
||
appear in section 4 of this document and therefore can no longer be
|
||
generated.
|
||
|
||
1. Period allowed in obsolete form of phrase.
|
||
2. ABNF moved out of document to [RFC2234].
|
||
3. Four or more digits allowed for year.
|
||
4. Header field ordering (and lack thereof) made explicit.
|
||
5. Encrypted header field removed.
|
||
6. Received syntax loosened to allow any token/value pair.
|
||
7. Specifically allow and give meaning to "-0000" time zone.
|
||
8. Folding white space is not allowed between every token.
|
||
9. Requirement for destinations removed.
|
||
10. Forwarding and resending redefined.
|
||
11. Extension header fields no longer specifically called out.
|
||
12. ASCII 0 (null) removed.*
|
||
13. Folding continuation lines cannot contain only white space.*
|
||
14. Free insertion of comments not allowed in date.*
|
||
15. Non-numeric time zones not allowed.*
|
||
16. Two digit years not allowed.*
|
||
17. Three digit years interpreted, but not allowed for generation.
|
||
18. Routes in addresses not allowed.*
|
||
19. CFWS within local-parts and domains not allowed.*
|
||
20. Empty members of address lists not allowed.*
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 49]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
21. Folding white space between field name and colon not allowed.*
|
||
22. Comments between field name and colon not allowed.
|
||
23. Tightened syntax of in-reply-to and references.*
|
||
24. CFWS within msg-id not allowed.*
|
||
25. Tightened semantics of resent fields as informational only.
|
||
26. Resent-Reply-To not allowed.*
|
||
27. No multiple occurrences of fields (except resent and received).*
|
||
28. Free CR and LF not allowed.*
|
||
29. Routes in return path not allowed.*
|
||
30. Line length limits specified.
|
||
31. Bcc more clearly specified.
|
||
|
||
Appendix C. Notices
|
||
|
||
Intellectual Property
|
||
|
||
The IETF takes no position regarding the validity or scope of any
|
||
intellectual property or other rights that might be claimed to
|
||
pertain to the implementation or use of the technology described in
|
||
this document or the extent to which any license under such rights
|
||
might or might not be available; neither does it represent that it
|
||
has made any effort to identify any such rights. Information on the
|
||
IETF's procedures with respect to rights in standards-track and
|
||
standards-related documentation can be found in BCP-11. Copies of
|
||
claims of rights made available for publication and any assurances of
|
||
licenses to be made available, or the result of an attempt made to
|
||
obtain a general license or permission for the use of such
|
||
proprietary rights by implementors or users of this specification can
|
||
be obtained from the IETF Secretariat.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 50]
|
||
|
||
RFC 2822 Internet Message Format April 2001
|
||
|
||
|
||
Full Copyright Statement
|
||
|
||
Copyright (C) The Internet Society (2001). All Rights Reserved.
|
||
|
||
This document and translations of it may be copied and furnished to
|
||
others, and derivative works that comment on or otherwise explain it
|
||
or assist in its implementation may be prepared, copied, published
|
||
and distributed, in whole or in part, without restriction of any
|
||
kind, provided that the above copyright notice and this paragraph are
|
||
included on all such copies and derivative works. However, this
|
||
document itself may not be modified in any way, such as by removing
|
||
the copyright notice or references to the Internet Society or other
|
||
Internet organizations, except as needed for the purpose of
|
||
developing Internet standards in which case the procedures for
|
||
copyrights defined in the Internet Standards process must be
|
||
followed, or as required to translate it into languages other than
|
||
English.
|
||
|
||
The limited permissions granted above are perpetual and will not be
|
||
revoked by the Internet Society or its successors or assigns.
|
||
|
||
This document and the information contained herein is provided on an
|
||
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
|
||
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
|
||
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
|
||
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
|
||
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
|
||
|
||
Acknowledgement
|
||
|
||
Funding for the RFC Editor function is currently provided by the
|
||
Internet Society.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Resnick Standards Track [Page 51]
|
||
|