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rfc5322.txt (122322B)
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7 Network Working Group P. Resnick, Ed.
8 Request for Comments: 5322 Qualcomm Incorporated
9 Obsoletes: 2822 October 2008
10 Updates: 4021
11 Category: Standards Track
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14 Internet Message Format
15
16 Status of This Memo
17
18 This document specifies an Internet standards track protocol for the
19 Internet community, and requests discussion and suggestions for
20 improvements. Please refer to the current edition of the "Internet
21 Official Protocol Standards" (STD 1) for the standardization state
22 and status of this protocol. Distribution of this memo is unlimited.
23
24 Abstract
25
26 This document specifies the Internet Message Format (IMF), a syntax
27 for text messages that are sent between computer users, within the
28 framework of "electronic mail" messages. This specification is a
29 revision of Request For Comments (RFC) 2822, which itself superseded
30 Request For Comments (RFC) 822, "Standard for the Format of ARPA
31 Internet Text Messages", updating it to reflect current practice and
32 incorporating incremental changes that were specified in other RFCs.
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58 Resnick Standards Track [Page 1]
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60 RFC 5322 Internet Message Format October 2008
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63 Table of Contents
64
65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
66 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
67 1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 5
68 1.2.1. Requirements Notation . . . . . . . . . . . . . . . . 5
69 1.2.2. Syntactic Notation . . . . . . . . . . . . . . . . . . 5
70 1.2.3. Structure of This Document . . . . . . . . . . . . . . 5
71 2. Lexical Analysis of Messages . . . . . . . . . . . . . . . . . 6
72 2.1. General Description . . . . . . . . . . . . . . . . . . . 6
73 2.1.1. Line Length Limits . . . . . . . . . . . . . . . . . . 7
74 2.2. Header Fields . . . . . . . . . . . . . . . . . . . . . . 8
75 2.2.1. Unstructured Header Field Bodies . . . . . . . . . . . 8
76 2.2.2. Structured Header Field Bodies . . . . . . . . . . . . 8
77 2.2.3. Long Header Fields . . . . . . . . . . . . . . . . . . 8
78 2.3. Body . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
79 3. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
80 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
81 3.2. Lexical Tokens . . . . . . . . . . . . . . . . . . . . . . 10
82 3.2.1. Quoted characters . . . . . . . . . . . . . . . . . . 10
83 3.2.2. Folding White Space and Comments . . . . . . . . . . . 11
84 3.2.3. Atom . . . . . . . . . . . . . . . . . . . . . . . . . 12
85 3.2.4. Quoted Strings . . . . . . . . . . . . . . . . . . . . 13
86 3.2.5. Miscellaneous Tokens . . . . . . . . . . . . . . . . . 14
87 3.3. Date and Time Specification . . . . . . . . . . . . . . . 14
88 3.4. Address Specification . . . . . . . . . . . . . . . . . . 16
89 3.4.1. Addr-Spec Specification . . . . . . . . . . . . . . . 17
90 3.5. Overall Message Syntax . . . . . . . . . . . . . . . . . . 18
91 3.6. Field Definitions . . . . . . . . . . . . . . . . . . . . 19
92 3.6.1. The Origination Date Field . . . . . . . . . . . . . . 22
93 3.6.2. Originator Fields . . . . . . . . . . . . . . . . . . 22
94 3.6.3. Destination Address Fields . . . . . . . . . . . . . . 23
95 3.6.4. Identification Fields . . . . . . . . . . . . . . . . 25
96 3.6.5. Informational Fields . . . . . . . . . . . . . . . . . 27
97 3.6.6. Resent Fields . . . . . . . . . . . . . . . . . . . . 28
98 3.6.7. Trace Fields . . . . . . . . . . . . . . . . . . . . . 30
99 3.6.8. Optional Fields . . . . . . . . . . . . . . . . . . . 30
100 4. Obsolete Syntax . . . . . . . . . . . . . . . . . . . . . . . 31
101 4.1. Miscellaneous Obsolete Tokens . . . . . . . . . . . . . . 32
102 4.2. Obsolete Folding White Space . . . . . . . . . . . . . . . 33
103 4.3. Obsolete Date and Time . . . . . . . . . . . . . . . . . . 33
104 4.4. Obsolete Addressing . . . . . . . . . . . . . . . . . . . 35
105 4.5. Obsolete Header Fields . . . . . . . . . . . . . . . . . . 35
106 4.5.1. Obsolete Origination Date Field . . . . . . . . . . . 36
107 4.5.2. Obsolete Originator Fields . . . . . . . . . . . . . . 36
108 4.5.3. Obsolete Destination Address Fields . . . . . . . . . 37
109 4.5.4. Obsolete Identification Fields . . . . . . . . . . . . 37
110 4.5.5. Obsolete Informational Fields . . . . . . . . . . . . 37
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119 4.5.6. Obsolete Resent Fields . . . . . . . . . . . . . . . . 38
120 4.5.7. Obsolete Trace Fields . . . . . . . . . . . . . . . . 38
121 4.5.8. Obsolete optional fields . . . . . . . . . . . . . . . 38
122 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
123 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
124 Appendix A. Example Messages . . . . . . . . . . . . . . . . . 43
125 Appendix A.1. Addressing Examples . . . . . . . . . . . . . . . 44
126 Appendix A.1.1. A Message from One Person to Another with
127 Simple Addressing . . . . . . . . . . . . . . . . 44
128 Appendix A.1.2. Different Types of Mailboxes . . . . . . . . . . . 45
129 Appendix A.1.3. Group Addresses . . . . . . . . . . . . . . . . . 45
130 Appendix A.2. Reply Messages . . . . . . . . . . . . . . . . . . 46
131 Appendix A.3. Resent Messages . . . . . . . . . . . . . . . . . 47
132 Appendix A.4. Messages with Trace Fields . . . . . . . . . . . . 48
133 Appendix A.5. White Space, Comments, and Other Oddities . . . . 49
134 Appendix A.6. Obsoleted Forms . . . . . . . . . . . . . . . . . 50
135 Appendix A.6.1. Obsolete Addressing . . . . . . . . . . . . . . . 50
136 Appendix A.6.2. Obsolete Dates . . . . . . . . . . . . . . . . . . 50
137 Appendix A.6.3. Obsolete White Space and Comments . . . . . . . . 51
138 Appendix B. Differences from Earlier Specifications . . . . . 52
139 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . 53
140 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
141 7.1. Normative References . . . . . . . . . . . . . . . . . . . 55
142 7.2. Informative References . . . . . . . . . . . . . . . . . . 55
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172 RFC 5322 Internet Message Format October 2008
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175 1. Introduction
176
177 1.1. Scope
178
179 This document specifies the Internet Message Format (IMF), a syntax
180 for text messages that are sent between computer users, within the
181 framework of "electronic mail" messages. This specification is an
182 update to [RFC2822], which itself superseded [RFC0822], updating it
183 to reflect current practice and incorporating incremental changes
184 that were specified in other RFCs such as [RFC1123].
185
186 This document specifies a syntax only for text messages. In
187 particular, it makes no provision for the transmission of images,
188 audio, or other sorts of structured data in electronic mail messages.
189 There are several extensions published, such as the MIME document
190 series ([RFC2045], [RFC2046], [RFC2049]), which describe mechanisms
191 for the transmission of such data through electronic mail, either by
192 extending the syntax provided here or by structuring such messages to
193 conform to this syntax. Those mechanisms are outside of the scope of
194 this specification.
195
196 In the context of electronic mail, messages are viewed as having an
197 envelope and contents. The envelope contains whatever information is
198 needed to accomplish transmission and delivery. (See [RFC5321] for a
199 discussion of the envelope.) The contents comprise the object to be
200 delivered to the recipient. This specification applies only to the
201 format and some of the semantics of message contents. It contains no
202 specification of the information in the envelope.
203
204 However, some message systems may use information from the contents
205 to create the envelope. It is intended that this specification
206 facilitate the acquisition of such information by programs.
207
208 This specification is intended as a definition of what message
209 content format is to be passed between systems. Though some message
210 systems locally store messages in this format (which eliminates the
211 need for translation between formats) and others use formats that
212 differ from the one specified in this specification, local storage is
213 outside of the scope of this specification.
214
215 Note: This specification is not intended to dictate the internal
216 formats used by sites, the specific message system features that
217 they are expected to support, or any of the characteristics of
218 user interface programs that create or read messages. In
219 addition, this document does not specify an encoding of the
220 characters for either transport or storage; that is, it does not
221 specify the number of bits used or how those bits are specifically
222 transferred over the wire or stored on disk.
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231 1.2. Notational Conventions
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233 1.2.1. Requirements Notation
234
235 This document occasionally uses terms that appear in capital letters.
236 When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
237 NOT", and "MAY" appear capitalized, they are being used to indicate
238 particular requirements of this specification. A discussion of the
239 meanings of these terms appears in [RFC2119].
240
241 1.2.2. Syntactic Notation
242
243 This specification uses the Augmented Backus-Naur Form (ABNF)
244 [RFC5234] notation for the formal definitions of the syntax of
245 messages. Characters will be specified either by a decimal value
246 (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
247 a case-insensitive literal value enclosed in quotation marks (e.g.,
248 "A" for either uppercase or lowercase A).
249
250 1.2.3. Structure of This Document
251
252 This document is divided into several sections.
253
254 This section, section 1, is a short introduction to the document.
255
256 Section 2 lays out the general description of a message and its
257 constituent parts. This is an overview to help the reader understand
258 some of the general principles used in the later portions of this
259 document. Any examples in this section MUST NOT be taken as
260 specification of the formal syntax of any part of a message.
261
262 Section 3 specifies formal ABNF rules for the structure of each part
263 of a message (the syntax) and describes the relationship between
264 those parts and their meaning in the context of a message (the
265 semantics). That is, it lays out the actual rules for the structure
266 of each part of a message (the syntax) as well as a description of
267 the parts and instructions for their interpretation (the semantics).
268 This includes analysis of the syntax and semantics of subparts of
269 messages that have specific structure. The syntax included in
270 section 3 represents messages as they MUST be created. There are
271 also notes in section 3 to indicate if any of the options specified
272 in the syntax SHOULD be used over any of the others.
273
274 Both sections 2 and 3 describe messages that are legal to generate
275 for purposes of this specification.
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287 Section 4 of this document specifies an "obsolete" syntax. There are
288 references in section 3 to these obsolete syntactic elements. The
289 rules of the obsolete syntax are elements that have appeared in
290 earlier versions of this specification or have previously been widely
291 used in Internet messages. As such, these elements MUST be
292 interpreted by parsers of messages in order to be conformant to this
293 specification. However, since items in this syntax have been
294 determined to be non-interoperable or to cause significant problems
295 for recipients of messages, they MUST NOT be generated by creators of
296 conformant messages.
297
298 Section 5 details security considerations to take into account when
299 implementing this specification.
300
301 Appendix A lists examples of different sorts of messages. These
302 examples are not exhaustive of the types of messages that appear on
303 the Internet, but give a broad overview of certain syntactic forms.
304
305 Appendix B lists the differences between this specification and
306 earlier specifications for Internet messages.
307
308 Appendix C contains acknowledgements.
309
310 2. Lexical Analysis of Messages
311
312 2.1. General Description
313
314 At the most basic level, a message is a series of characters. A
315 message that is conformant with this specification is composed of
316 characters with values in the range of 1 through 127 and interpreted
317 as US-ASCII [ANSI.X3-4.1986] characters. For brevity, this document
318 sometimes refers to this range of characters as simply "US-ASCII
319 characters".
320
321 Note: This document specifies that messages are made up of
322 characters in the US-ASCII range of 1 through 127. There are
323 other documents, specifically the MIME document series ([RFC2045],
324 [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]), that
325 extend this specification to allow for values outside of that
326 range. Discussion of those mechanisms is not within the scope of
327 this specification.
328
329 Messages are divided into lines of characters. A line is a series of
330 characters that is delimited with the two characters carriage-return
331 and line-feed; that is, the carriage return (CR) character (ASCII
332 value 13) followed immediately by the line feed (LF) character (ASCII
333 value 10). (The carriage return/line feed pair is usually written in
334 this document as "CRLF".)
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343 A message consists of header fields (collectively called "the header
344 section of the message") followed, optionally, by a body. The header
345 section is a sequence of lines of characters with special syntax as
346 defined in this specification. The body is simply a sequence of
347 characters that follows the header section and is separated from the
348 header section by an empty line (i.e., a line with nothing preceding
349 the CRLF).
350
351 Note: Common parlance and earlier versions of this specification
352 use the term "header" to either refer to the entire header section
353 or to refer to an individual header field. To avoid ambiguity,
354 this document does not use the terms "header" or "headers" in
355 isolation, but instead always uses "header field" to refer to the
356 individual field and "header section" to refer to the entire
357 collection.
358
359 2.1.1. Line Length Limits
360
361 There are two limits that this specification places on the number of
362 characters in a line. Each line of characters MUST be no more than
363 998 characters, and SHOULD be no more than 78 characters, excluding
364 the CRLF.
365
366 The 998 character limit is due to limitations in many implementations
367 that send, receive, or store IMF messages which simply cannot handle
368 more than 998 characters on a line. Receiving implementations would
369 do well to handle an arbitrarily large number of characters in a line
370 for robustness sake. However, there are so many implementations that
371 (in compliance with the transport requirements of [RFC5321]) do not
372 accept messages containing more than 1000 characters including the CR
373 and LF per line, it is important for implementations not to create
374 such messages.
375
376 The more conservative 78 character recommendation is to accommodate
377 the many implementations of user interfaces that display these
378 messages which may truncate, or disastrously wrap, the display of
379 more than 78 characters per line, in spite of the fact that such
380 implementations are non-conformant to the intent of this
381 specification (and that of [RFC5321] if they actually cause
382 information to be lost). Again, even though this limitation is put
383 on messages, it is incumbent upon implementations that display
384 messages to handle an arbitrarily large number of characters in a
385 line (certainly at least up to the 998 character limit) for the sake
386 of robustness.
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399 2.2. Header Fields
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401 Header fields are lines beginning with a field name, followed by a
402 colon (":"), followed by a field body, and terminated by CRLF. A
403 field name MUST be composed of printable US-ASCII characters (i.e.,
404 characters that have values between 33 and 126, inclusive), except
405 colon. A field body may be composed of printable US-ASCII characters
406 as well as the space (SP, ASCII value 32) and horizontal tab (HTAB,
407 ASCII value 9) characters (together known as the white space
408 characters, WSP). A field body MUST NOT include CR and LF except
409 when used in "folding" and "unfolding", as described in section
410 2.2.3. All field bodies MUST conform to the syntax described in
411 sections 3 and 4 of this specification.
412
413 2.2.1. Unstructured Header Field Bodies
414
415 Some field bodies in this specification are defined simply as
416 "unstructured" (which is specified in section 3.2.5 as any printable
417 US-ASCII characters plus white space characters) with no further
418 restrictions. These are referred to as unstructured field bodies.
419 Semantically, unstructured field bodies are simply to be treated as a
420 single line of characters with no further processing (except for
421 "folding" and "unfolding" as described in section 2.2.3).
422
423 2.2.2. Structured Header Field Bodies
424
425 Some field bodies in this specification have a syntax that is more
426 restrictive than the unstructured field bodies described above.
427 These are referred to as "structured" field bodies. Structured field
428 bodies are sequences of specific lexical tokens as described in
429 sections 3 and 4 of this specification. Many of these tokens are
430 allowed (according to their syntax) to be introduced or end with
431 comments (as described in section 3.2.2) as well as the white space
432 characters, and those white space characters are subject to "folding"
433 and "unfolding" as described in section 2.2.3. Semantic analysis of
434 structured field bodies is given along with their syntax.
435
436 2.2.3. Long Header Fields
437
438 Each header field is logically a single line of characters comprising
439 the field name, the colon, and the field body. For convenience
440 however, and to deal with the 998/78 character limitations per line,
441 the field body portion of a header field can be split into a
442 multiple-line representation; this is called "folding". The general
443 rule is that wherever this specification allows for folding white
444 space (not simply WSP characters), a CRLF may be inserted before any
445 WSP.
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452 RFC 5322 Internet Message Format October 2008
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455 For example, the header field:
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457 Subject: This is a test
458
459 can be represented as:
460
461 Subject: This
462 is a test
463
464 Note: Though structured field bodies are defined in such a way
465 that folding can take place between many of the lexical tokens
466 (and even within some of the lexical tokens), folding SHOULD be
467 limited to placing the CRLF at higher-level syntactic breaks. For
468 instance, if a field body is defined as comma-separated values, it
469 is recommended that folding occur after the comma separating the
470 structured items in preference to other places where the field
471 could be folded, even if it is allowed elsewhere.
472
473 The process of moving from this folded multiple-line representation
474 of a header field to its single line representation is called
475 "unfolding". Unfolding is accomplished by simply removing any CRLF
476 that is immediately followed by WSP. Each header field should be
477 treated in its unfolded form for further syntactic and semantic
478 evaluation. An unfolded header field has no length restriction and
479 therefore may be indeterminately long.
480
481 2.3. Body
482
483 The body of a message is simply lines of US-ASCII characters. The
484 only two limitations on the body are as follows:
485
486 o CR and LF MUST only occur together as CRLF; they MUST NOT appear
487 independently in the body.
488 o Lines of characters in the body MUST be limited to 998 characters,
489 and SHOULD be limited to 78 characters, excluding the CRLF.
490
491 Note: As was stated earlier, there are other documents,
492 specifically the MIME documents ([RFC2045], [RFC2046], [RFC2049],
493 [RFC4288], [RFC4289]), that extend (and limit) this specification
494 to allow for different sorts of message bodies. Again, these
495 mechanisms are beyond the scope of this document.
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511 3. Syntax
512
513 3.1. Introduction
514
515 The syntax as given in this section defines the legal syntax of
516 Internet messages. Messages that are conformant to this
517 specification MUST conform to the syntax in this section. If there
518 are options in this section where one option SHOULD be generated,
519 that is indicated either in the prose or in a comment next to the
520 syntax.
521
522 For the defined expressions, a short description of the syntax and
523 use is given, followed by the syntax in ABNF, followed by a semantic
524 analysis. The following primitive tokens that are used but otherwise
525 unspecified are taken from the "Core Rules" of [RFC5234], Appendix
526 B.1: CR, LF, CRLF, HTAB, SP, WSP, DQUOTE, DIGIT, ALPHA, and VCHAR.
527
528 In some of the definitions, there will be non-terminals whose names
529 start with "obs-". These "obs-" elements refer to tokens defined in
530 the obsolete syntax in section 4. In all cases, these productions
531 are to be ignored for the purposes of generating legal Internet
532 messages and MUST NOT be used as part of such a message. However,
533 when interpreting messages, these tokens MUST be honored as part of
534 the legal syntax. In this sense, section 3 defines a grammar for the
535 generation of messages, with "obs-" elements that are to be ignored,
536 while section 4 adds grammar for the interpretation of messages.
537
538 3.2. Lexical Tokens
539
540 The following rules are used to define an underlying lexical
541 analyzer, which feeds tokens to the higher-level parsers. This
542 section defines the tokens used in structured header field bodies.
543
544 Note: Readers of this specification need to pay special attention
545 to how these lexical tokens are used in both the lower-level and
546 higher-level syntax later in the document. Particularly, the
547 white space tokens and the comment tokens defined in section 3.2.2
548 get used in the lower-level tokens defined here, and those lower-
549 level tokens are in turn used as parts of the higher-level tokens
550 defined later. Therefore, white space and comments may be allowed
551 in the higher-level tokens even though they may not explicitly
552 appear in a particular definition.
553
554 3.2.1. Quoted characters
555
556 Some characters are reserved for special interpretation, such as
557 delimiting lexical tokens. To permit use of these characters as
558 uninterpreted data, a quoting mechanism is provided.
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567 quoted-pair = ("\" (VCHAR / WSP)) / obs-qp
568
569 Where any quoted-pair appears, it is to be interpreted as the
570 character alone. That is to say, the "\" character that appears as
571 part of a quoted-pair is semantically "invisible".
572
573 Note: The "\" character may appear in a message where it is not
574 part of a quoted-pair. A "\" character that does not appear in a
575 quoted-pair is not semantically invisible. The only places in
576 this specification where quoted-pair currently appears are
577 ccontent, qcontent, and in obs-dtext in section 4.
578
579 3.2.2. Folding White Space and Comments
580
581 White space characters, including white space used in folding
582 (described in section 2.2.3), may appear between many elements in
583 header field bodies. Also, strings of characters that are treated as
584 comments may be included in structured field bodies as characters
585 enclosed in parentheses. The following defines the folding white
586 space (FWS) and comment constructs.
587
588 Strings of characters enclosed in parentheses are considered comments
589 so long as they do not appear within a "quoted-string", as defined in
590 section 3.2.4. Comments may nest.
591
592 There are several places in this specification where comments and FWS
593 may be freely inserted. To accommodate that syntax, an additional
594 token for "CFWS" is defined for places where comments and/or FWS can
595 occur. However, where CFWS occurs in this specification, it MUST NOT
596 be inserted in such a way that any line of a folded header field is
597 made up entirely of WSP characters and nothing else.
598
599 FWS = ([*WSP CRLF] 1*WSP) / obs-FWS
600 ; Folding white space
601
602 ctext = %d33-39 / ; Printable US-ASCII
603 %d42-91 / ; characters not including
604 %d93-126 / ; "(", ")", or "\"
605 obs-ctext
606
607 ccontent = ctext / quoted-pair / comment
608
609 comment = "(" *([FWS] ccontent) [FWS] ")"
610
611 CFWS = (1*([FWS] comment) [FWS]) / FWS
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623 Throughout this specification, where FWS (the folding white space
624 token) appears, it indicates a place where folding, as discussed in
625 section 2.2.3, may take place. Wherever folding appears in a message
626 (that is, a header field body containing a CRLF followed by any WSP),
627 unfolding (removal of the CRLF) is performed before any further
628 semantic analysis is performed on that header field according to this
629 specification. That is to say, any CRLF that appears in FWS is
630 semantically "invisible".
631
632 A comment is normally used in a structured field body to provide some
633 human-readable informational text. Since a comment is allowed to
634 contain FWS, folding is permitted within the comment. Also note that
635 since quoted-pair is allowed in a comment, the parentheses and
636 backslash characters may appear in a comment, so long as they appear
637 as a quoted-pair. Semantically, the enclosing parentheses are not
638 part of the comment; the comment is what is contained between the two
639 parentheses. As stated earlier, the "\" in any quoted-pair and the
640 CRLF in any FWS that appears within the comment are semantically
641 "invisible" and therefore not part of the comment either.
642
643 Runs of FWS, comment, or CFWS that occur between lexical tokens in a
644 structured header field are semantically interpreted as a single
645 space character.
646
647 3.2.3. Atom
648
649 Several productions in structured header field bodies are simply
650 strings of certain basic characters. Such productions are called
651 atoms.
652
653 Some of the structured header field bodies also allow the period
654 character (".", ASCII value 46) within runs of atext. An additional
655 "dot-atom" token is defined for those purposes.
656
657 Note: The "specials" token does not appear anywhere else in this
658 specification. It is simply the visible (i.e., non-control, non-
659 white space) characters that do not appear in atext. It is
660 provided only because it is useful for implementers who use tools
661 that lexically analyze messages. Each of the characters in
662 specials can be used to indicate a tokenization point in lexical
663 analysis.
664
665
666
667
668
669
670
671
672
673
674 Resnick Standards Track [Page 12]
675
676 RFC 5322 Internet Message Format October 2008
677
678
679 atext = ALPHA / DIGIT / ; Printable US-ASCII
680 "!" / "#" / ; characters not including
681 "$" / "%" / ; specials. Used for atoms.
682 "&" / "'" /
683 "*" / "+" /
684 "-" / "/" /
685 "=" / "?" /
686 "^" / "_" /
687 "`" / "{" /
688 "|" / "}" /
689 "~"
690
691 atom = [CFWS] 1*atext [CFWS]
692
693 dot-atom-text = 1*atext *("." 1*atext)
694
695 dot-atom = [CFWS] dot-atom-text [CFWS]
696
697 specials = "(" / ")" / ; Special characters that do
698 "<" / ">" / ; not appear in atext
699 "[" / "]" /
700 ":" / ";" /
701 "@" / "\" /
702 "," / "." /
703 DQUOTE
704
705 Both atom and dot-atom are interpreted as a single unit, comprising
706 the string of characters that make it up. Semantically, the optional
707 comments and FWS surrounding the rest of the characters are not part
708 of the atom; the atom is only the run of atext characters in an atom,
709 or the atext and "." characters in a dot-atom.
710
711 3.2.4. Quoted Strings
712
713 Strings of characters that include characters other than those
714 allowed in atoms can be represented in a quoted string format, where
715 the characters are surrounded by quote (DQUOTE, ASCII value 34)
716 characters.
717
718
719
720
721
722
723
724
725
726
727
728
729
730 Resnick Standards Track [Page 13]
731
732 RFC 5322 Internet Message Format October 2008
733
734
735 qtext = %d33 / ; Printable US-ASCII
736 %d35-91 / ; characters not including
737 %d93-126 / ; "\" or the quote character
738 obs-qtext
739
740 qcontent = qtext / quoted-pair
741
742 quoted-string = [CFWS]
743 DQUOTE *([FWS] qcontent) [FWS] DQUOTE
744 [CFWS]
745
746 A quoted-string is treated as a unit. That is, quoted-string is
747 identical to atom, semantically. Since a quoted-string is allowed to
748 contain FWS, folding is permitted. Also note that since quoted-pair
749 is allowed in a quoted-string, the quote and backslash characters may
750 appear in a quoted-string so long as they appear as a quoted-pair.
751
752 Semantically, neither the optional CFWS outside of the quote
753 characters nor the quote characters themselves are part of the
754 quoted-string; the quoted-string is what is contained between the two
755 quote characters. As stated earlier, the "\" in any quoted-pair and
756 the CRLF in any FWS/CFWS that appears within the quoted-string are
757 semantically "invisible" and therefore not part of the quoted-string
758 either.
759
760 3.2.5. Miscellaneous Tokens
761
762 Three additional tokens are defined: word and phrase for combinations
763 of atoms and/or quoted-strings, and unstructured for use in
764 unstructured header fields and in some places within structured
765 header fields.
766
767 word = atom / quoted-string
768
769 phrase = 1*word / obs-phrase
770
771 unstructured = (*([FWS] VCHAR) *WSP) / obs-unstruct
772
773 3.3. Date and Time Specification
774
775 Date and time values occur in several header fields. This section
776 specifies the syntax for a full date and time specification. Though
777 folding white space is permitted throughout the date-time
778 specification, it is RECOMMENDED that a single space be used in each
779 place that FWS appears (whether it is required or optional); some
780 older implementations will not interpret longer sequences of folding
781 white space correctly.
782
783
784
785
786 Resnick Standards Track [Page 14]
787
788 RFC 5322 Internet Message Format October 2008
789
790
791 date-time = [ day-of-week "," ] date time [CFWS]
792
793 day-of-week = ([FWS] day-name) / obs-day-of-week
794
795 day-name = "Mon" / "Tue" / "Wed" / "Thu" /
796 "Fri" / "Sat" / "Sun"
797
798 date = day month year
799
800 day = ([FWS] 1*2DIGIT FWS) / obs-day
801
802 month = "Jan" / "Feb" / "Mar" / "Apr" /
803 "May" / "Jun" / "Jul" / "Aug" /
804 "Sep" / "Oct" / "Nov" / "Dec"
805
806 year = (FWS 4*DIGIT FWS) / obs-year
807
808 time = time-of-day zone
809
810 time-of-day = hour ":" minute [ ":" second ]
811
812 hour = 2DIGIT / obs-hour
813
814 minute = 2DIGIT / obs-minute
815
816 second = 2DIGIT / obs-second
817
818 zone = (FWS ( "+" / "-" ) 4DIGIT) / obs-zone
819
820 The day is the numeric day of the month. The year is any numeric
821 year 1900 or later.
822
823 The time-of-day specifies the number of hours, minutes, and
824 optionally seconds since midnight of the date indicated.
825
826 The date and time-of-day SHOULD express local time.
827
828 The zone specifies the offset from Coordinated Universal Time (UTC,
829 formerly referred to as "Greenwich Mean Time") that the date and
830 time-of-day represent. The "+" or "-" indicates whether the time-of-
831 day is ahead of (i.e., east of) or behind (i.e., west of) Universal
832 Time. The first two digits indicate the number of hours difference
833 from Universal Time, and the last two digits indicate the number of
834 additional minutes difference from Universal Time. (Hence, +hhmm
835 means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
836 minutes). The form "+0000" SHOULD be used to indicate a time zone at
837 Universal Time. Though "-0000" also indicates Universal Time, it is
838
839
840
841
842 Resnick Standards Track [Page 15]
843
844 RFC 5322 Internet Message Format October 2008
845
846
847 used to indicate that the time was generated on a system that may be
848 in a local time zone other than Universal Time and that the date-time
849 contains no information about the local time zone.
850
851 A date-time specification MUST be semantically valid. That is, the
852 day-of-week (if included) MUST be the day implied by the date, the
853 numeric day-of-month MUST be between 1 and the number of days allowed
854 for the specified month (in the specified year), the time-of-day MUST
855 be in the range 00:00:00 through 23:59:60 (the number of seconds
856 allowing for a leap second; see [RFC1305]), and the last two digits
857 of the zone MUST be within the range 00 through 59.
858
859 3.4. Address Specification
860
861 Addresses occur in several message header fields to indicate senders
862 and recipients of messages. An address may either be an individual
863 mailbox, or a group of mailboxes.
864
865 address = mailbox / group
866
867 mailbox = name-addr / addr-spec
868
869 name-addr = [display-name] angle-addr
870
871 angle-addr = [CFWS] "<" addr-spec ">" [CFWS] /
872 obs-angle-addr
873
874 group = display-name ":" [group-list] ";" [CFWS]
875
876 display-name = phrase
877
878 mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
879
880 address-list = (address *("," address)) / obs-addr-list
881
882 group-list = mailbox-list / CFWS / obs-group-list
883
884 A mailbox receives mail. It is a conceptual entity that does not
885 necessarily pertain to file storage. For example, some sites may
886 choose to print mail on a printer and deliver the output to the
887 addressee's desk.
888
889 Normally, a mailbox is composed of two parts: (1) an optional display
890 name that indicates the name of the recipient (which can be a person
891 or a system) that could be displayed to the user of a mail
892 application, and (2) an addr-spec address enclosed in angle brackets
893
894
895
896
897
898 Resnick Standards Track [Page 16]
899
900 RFC 5322 Internet Message Format October 2008
901
902
903 ("<" and ">"). There is an alternate simple form of a mailbox where
904 the addr-spec address appears alone, without the recipient's name or
905 the angle brackets. The Internet addr-spec address is described in
906 section 3.4.1.
907
908 Note: Some legacy implementations used the simple form where the
909 addr-spec appears without the angle brackets, but included the
910 name of the recipient in parentheses as a comment following the
911 addr-spec. Since the meaning of the information in a comment is
912 unspecified, implementations SHOULD use the full name-addr form of
913 the mailbox, instead of the legacy form, to specify the display
914 name associated with a mailbox. Also, because some legacy
915 implementations interpret the comment, comments generally SHOULD
916 NOT be used in address fields to avoid confusing such
917 implementations.
918
919 When it is desirable to treat several mailboxes as a single unit
920 (i.e., in a distribution list), the group construct can be used. The
921 group construct allows the sender to indicate a named group of
922 recipients. This is done by giving a display name for the group,
923 followed by a colon, followed by a comma-separated list of any number
924 of mailboxes (including zero and one), and ending with a semicolon.
925 Because the list of mailboxes can be empty, using the group construct
926 is also a simple way to communicate to recipients that the message
927 was sent to one or more named sets of recipients, without actually
928 providing the individual mailbox address for any of those recipients.
929
930 3.4.1. Addr-Spec Specification
931
932 An addr-spec is a specific Internet identifier that contains a
933 locally interpreted string followed by the at-sign character ("@",
934 ASCII value 64) followed by an Internet domain. The locally
935 interpreted string is either a quoted-string or a dot-atom. If the
936 string can be represented as a dot-atom (that is, it contains no
937 characters other than atext characters or "." surrounded by atext
938 characters), then the dot-atom form SHOULD be used and the quoted-
939 string form SHOULD NOT be used. Comments and folding white space
940 SHOULD NOT be used around the "@" in the addr-spec.
941
942 Note: A liberal syntax for the domain portion of addr-spec is
943 given here. However, the domain portion contains addressing
944 information specified by and used in other protocols (e.g.,
945 [RFC1034], [RFC1035], [RFC1123], [RFC5321]). It is therefore
946 incumbent upon implementations to conform to the syntax of
947 addresses for the context in which they are used.
948
949
950
951
952
953
954 Resnick Standards Track [Page 17]
955
956 RFC 5322 Internet Message Format October 2008
957
958
959 addr-spec = local-part "@" domain
960
961 local-part = dot-atom / quoted-string / obs-local-part
962
963 domain = dot-atom / domain-literal / obs-domain
964
965 domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
966
967 dtext = %d33-90 / ; Printable US-ASCII
968 %d94-126 / ; characters not including
969 obs-dtext ; "[", "]", or "\"
970
971 The domain portion identifies the point to which the mail is
972 delivered. In the dot-atom form, this is interpreted as an Internet
973 domain name (either a host name or a mail exchanger name) as
974 described in [RFC1034], [RFC1035], and [RFC1123]. In the domain-
975 literal form, the domain is interpreted as the literal Internet
976 address of the particular host. In both cases, how addressing is
977 used and how messages are transported to a particular host is covered
978 in separate documents, such as [RFC5321]. These mechanisms are
979 outside of the scope of this document.
980
981 The local-part portion is a domain-dependent string. In addresses,
982 it is simply interpreted on the particular host as a name of a
983 particular mailbox.
984
985 3.5. Overall Message Syntax
986
987 A message consists of header fields, optionally followed by a message
988 body. Lines in a message MUST be a maximum of 998 characters
989 excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
990 characters excluding the CRLF. (See section 2.1.1 for explanation.)
991 In a message body, though all of the characters listed in the text
992 rule MAY be used, the use of US-ASCII control characters (values 1
993 through 8, 11, 12, and 14 through 31) is discouraged since their
994 interpretation by receivers for display is not guaranteed.
995
996 message = (fields / obs-fields)
997 [CRLF body]
998
999 body = (*(*998text CRLF) *998text) / obs-body
1000
1001 text = %d1-9 / ; Characters excluding CR
1002 %d11 / ; and LF
1003 %d12 /
1004 %d14-127
1005
1006
1007
1008
1009
1010 Resnick Standards Track [Page 18]
1011
1012 RFC 5322 Internet Message Format October 2008
1013
1014
1015 The header fields carry most of the semantic information and are
1016 defined in section 3.6. The body is simply a series of lines of text
1017 that are uninterpreted for the purposes of this specification.
1018
1019 3.6. Field Definitions
1020
1021 The header fields of a message are defined here. All header fields
1022 have the same general syntactic structure: a field name, followed by
1023 a colon, followed by the field body. The specific syntax for each
1024 header field is defined in the subsequent sections.
1025
1026 Note: In the ABNF syntax for each field in subsequent sections,
1027 each field name is followed by the required colon. However, for
1028 brevity, sometimes the colon is not referred to in the textual
1029 description of the syntax. It is, nonetheless, required.
1030
1031 It is important to note that the header fields are not guaranteed to
1032 be in a particular order. They may appear in any order, and they
1033 have been known to be reordered occasionally when transported over
1034 the Internet. However, for the purposes of this specification,
1035 header fields SHOULD NOT be reordered when a message is transported
1036 or transformed. More importantly, the trace header fields and resent
1037 header fields MUST NOT be reordered, and SHOULD be kept in blocks
1038 prepended to the message. See sections 3.6.6 and 3.6.7 for more
1039 information.
1040
1041 The only required header fields are the origination date field and
1042 the originator address field(s). All other header fields are
1043 syntactically optional. More information is contained in the table
1044 following this definition.
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066 Resnick Standards Track [Page 19]
1067
1068 RFC 5322 Internet Message Format October 2008
1069
1070
1071 fields = *(trace
1072 *optional-field /
1073 *(resent-date /
1074 resent-from /
1075 resent-sender /
1076 resent-to /
1077 resent-cc /
1078 resent-bcc /
1079 resent-msg-id))
1080 *(orig-date /
1081 from /
1082 sender /
1083 reply-to /
1084 to /
1085 cc /
1086 bcc /
1087 message-id /
1088 in-reply-to /
1089 references /
1090 subject /
1091 comments /
1092 keywords /
1093 optional-field)
1094
1095 The following table indicates limits on the number of times each
1096 field may occur in the header section of a message as well as any
1097 special limitations on the use of those fields. An asterisk ("*")
1098 next to a value in the minimum or maximum column indicates that a
1099 special restriction appears in the Notes column.
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122 Resnick Standards Track [Page 20]
1123
1124 RFC 5322 Internet Message Format October 2008
1125
1126
1127 +----------------+--------+------------+----------------------------+
1128 | Field | Min | Max number | Notes |
1129 | | number | | |
1130 +----------------+--------+------------+----------------------------+
1131 | trace | 0 | unlimited | Block prepended - see |
1132 | | | | 3.6.7 |
1133 | resent-date | 0* | unlimited* | One per block, required if |
1134 | | | | other resent fields are |
1135 | | | | present - see 3.6.6 |
1136 | resent-from | 0 | unlimited* | One per block - see 3.6.6 |
1137 | resent-sender | 0* | unlimited* | One per block, MUST occur |
1138 | | | | with multi-address |
1139 | | | | resent-from - see 3.6.6 |
1140 | resent-to | 0 | unlimited* | One per block - see 3.6.6 |
1141 | resent-cc | 0 | unlimited* | One per block - see 3.6.6 |
1142 | resent-bcc | 0 | unlimited* | One per block - see 3.6.6 |
1143 | resent-msg-id | 0 | unlimited* | One per block - see 3.6.6 |
1144 | orig-date | 1 | 1 | |
1145 | from | 1 | 1 | See sender and 3.6.2 |
1146 | sender | 0* | 1 | MUST occur with |
1147 | | | | multi-address from - see |
1148 | | | | 3.6.2 |
1149 | reply-to | 0 | 1 | |
1150 | to | 0 | 1 | |
1151 | cc | 0 | 1 | |
1152 | bcc | 0 | 1 | |
1153 | message-id | 0* | 1 | SHOULD be present - see |
1154 | | | | 3.6.4 |
1155 | in-reply-to | 0* | 1 | SHOULD occur in some |
1156 | | | | replies - see 3.6.4 |
1157 | references | 0* | 1 | SHOULD occur in some |
1158 | | | | replies - see 3.6.4 |
1159 | subject | 0 | 1 | |
1160 | comments | 0 | unlimited | |
1161 | keywords | 0 | unlimited | |
1162 | optional-field | 0 | unlimited | |
1163 +----------------+--------+------------+----------------------------+
1164
1165 The exact interpretation of each field is described in subsequent
1166 sections.
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178 Resnick Standards Track [Page 21]
1179
1180 RFC 5322 Internet Message Format October 2008
1181
1182
1183 3.6.1. The Origination Date Field
1184
1185 The origination date field consists of the field name "Date" followed
1186 by a date-time specification.
1187
1188 orig-date = "Date:" date-time CRLF
1189
1190 The origination date specifies the date and time at which the creator
1191 of the message indicated that the message was complete and ready to
1192 enter the mail delivery system. For instance, this might be the time
1193 that a user pushes the "send" or "submit" button in an application
1194 program. In any case, it is specifically not intended to convey the
1195 time that the message is actually transported, but rather the time at
1196 which the human or other creator of the message has put the message
1197 into its final form, ready for transport. (For example, a portable
1198 computer user who is not connected to a network might queue a message
1199 for delivery. The origination date is intended to contain the date
1200 and time that the user queued the message, not the time when the user
1201 connected to the network to send the message.)
1202
1203 3.6.2. Originator Fields
1204
1205 The originator fields of a message consist of the from field, the
1206 sender field (when applicable), and optionally the reply-to field.
1207 The from field consists of the field name "From" and a comma-
1208 separated list of one or more mailbox specifications. If the from
1209 field contains more than one mailbox specification in the mailbox-
1210 list, then the sender field, containing the field name "Sender" and a
1211 single mailbox specification, MUST appear in the message. In either
1212 case, an optional reply-to field MAY also be included, which contains
1213 the field name "Reply-To" and a comma-separated list of one or more
1214 addresses.
1215
1216 from = "From:" mailbox-list CRLF
1217
1218 sender = "Sender:" mailbox CRLF
1219
1220 reply-to = "Reply-To:" address-list CRLF
1221
1222 The originator fields indicate the mailbox(es) of the source of the
1223 message. The "From:" field specifies the author(s) of the message,
1224 that is, the mailbox(es) of the person(s) or system(s) responsible
1225 for the writing of the message. The "Sender:" field specifies the
1226 mailbox of the agent responsible for the actual transmission of the
1227 message. For example, if a secretary were to send a message for
1228 another person, the mailbox of the secretary would appear in the
1229 "Sender:" field and the mailbox of the actual author would appear in
1230 the "From:" field. If the originator of the message can be indicated
1231
1232
1233
1234 Resnick Standards Track [Page 22]
1235
1236 RFC 5322 Internet Message Format October 2008
1237
1238
1239 by a single mailbox and the author and transmitter are identical, the
1240 "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
1241 appear.
1242
1243 Note: The transmitter information is always present. The absence
1244 of the "Sender:" field is sometimes mistakenly taken to mean that
1245 the agent responsible for transmission of the message has not been
1246 specified. This absence merely means that the transmitter is
1247 identical to the author and is therefore not redundantly placed
1248 into the "Sender:" field.
1249
1250 The originator fields also provide the information required when
1251 replying to a message. When the "Reply-To:" field is present, it
1252 indicates the address(es) to which the author of the message suggests
1253 that replies be sent. In the absence of the "Reply-To:" field,
1254 replies SHOULD by default be sent to the mailbox(es) specified in the
1255 "From:" field unless otherwise specified by the person composing the
1256 reply.
1257
1258 In all cases, the "From:" field SHOULD NOT contain any mailbox that
1259 does not belong to the author(s) of the message. See also section
1260 3.6.3 for more information on forming the destination addresses for a
1261 reply.
1262
1263 3.6.3. Destination Address Fields
1264
1265 The destination fields of a message consist of three possible fields,
1266 each of the same form: the field name, which is either "To", "Cc", or
1267 "Bcc", followed by a comma-separated list of one or more addresses
1268 (either mailbox or group syntax).
1269
1270 to = "To:" address-list CRLF
1271
1272 cc = "Cc:" address-list CRLF
1273
1274 bcc = "Bcc:" [address-list / CFWS] CRLF
1275
1276 The destination fields specify the recipients of the message. Each
1277 destination field may have one or more addresses, and the addresses
1278 indicate the intended recipients of the message. The only difference
1279 between the three fields is how each is used.
1280
1281 The "To:" field contains the address(es) of the primary recipient(s)
1282 of the message.
1283
1284
1285
1286
1287
1288
1289
1290 Resnick Standards Track [Page 23]
1291
1292 RFC 5322 Internet Message Format October 2008
1293
1294
1295 The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
1296 making a copy on a typewriter using carbon paper) contains the
1297 addresses of others who are to receive the message, though the
1298 content of the message may not be directed at them.
1299
1300 The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
1301 addresses of recipients of the message whose addresses are not to be
1302 revealed to other recipients of the message. There are three ways in
1303 which the "Bcc:" field is used. In the first case, when a message
1304 containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
1305 removed even though all of the recipients (including those specified
1306 in the "Bcc:" field) are sent a copy of the message. In the second
1307 case, recipients specified in the "To:" and "Cc:" lines each are sent
1308 a copy of the message with the "Bcc:" line removed as above, but the
1309 recipients on the "Bcc:" line get a separate copy of the message
1310 containing a "Bcc:" line. (When there are multiple recipient
1311 addresses in the "Bcc:" field, some implementations actually send a
1312 separate copy of the message to each recipient with a "Bcc:"
1313 containing only the address of that particular recipient.) Finally,
1314 since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
1315 sent without any addresses indicating to the recipients that blind
1316 copies were sent to someone. Which method to use with "Bcc:" fields
1317 is implementation dependent, but refer to the "Security
1318 Considerations" section of this document for a discussion of each.
1319
1320 When a message is a reply to another message, the mailboxes of the
1321 authors of the original message (the mailboxes in the "From:" field)
1322 or mailboxes specified in the "Reply-To:" field (if it exists) MAY
1323 appear in the "To:" field of the reply since these would normally be
1324 the primary recipients of the reply. If a reply is sent to a message
1325 that has destination fields, it is often desirable to send a copy of
1326 the reply to all of the recipients of the message, in addition to the
1327 author. When such a reply is formed, addresses in the "To:" and
1328 "Cc:" fields of the original message MAY appear in the "Cc:" field of
1329 the reply, since these are normally secondary recipients of the
1330 reply. If a "Bcc:" field is present in the original message,
1331 addresses in that field MAY appear in the "Bcc:" field of the reply,
1332 but they SHOULD NOT appear in the "To:" or "Cc:" fields.
1333
1334 Note: Some mail applications have automatic reply commands that
1335 include the destination addresses of the original message in the
1336 destination addresses of the reply. How those reply commands
1337 behave is implementation dependent and is beyond the scope of this
1338 document. In particular, whether or not to include the original
1339 destination addresses when the original message had a "Reply-To:"
1340 field is not addressed here.
1341
1342
1343
1344
1345
1346 Resnick Standards Track [Page 24]
1347
1348 RFC 5322 Internet Message Format October 2008
1349
1350
1351 3.6.4. Identification Fields
1352
1353 Though listed as optional in the table in section 3.6, every message
1354 SHOULD have a "Message-ID:" field. Furthermore, reply messages
1355 SHOULD have "In-Reply-To:" and "References:" fields as appropriate
1356 and as described below.
1357
1358 The "Message-ID:" field contains a single unique message identifier.
1359 The "References:" and "In-Reply-To:" fields each contain one or more
1360 unique message identifiers, optionally separated by CFWS.
1361
1362 The message identifier (msg-id) syntax is a limited version of the
1363 addr-spec construct enclosed in the angle bracket characters, "<" and
1364 ">". Unlike addr-spec, this syntax only permits the dot-atom-text
1365 form on the left-hand side of the "@" and does not have internal CFWS
1366 anywhere in the message identifier.
1367
1368 Note: As with addr-spec, a liberal syntax is given for the right-
1369 hand side of the "@" in a msg-id. However, later in this section,
1370 the use of a domain for the right-hand side of the "@" is
1371 RECOMMENDED. Again, the syntax of domain constructs is specified
1372 by and used in other protocols (e.g., [RFC1034], [RFC1035],
1373 [RFC1123], [RFC5321]). It is therefore incumbent upon
1374 implementations to conform to the syntax of addresses for the
1375 context in which they are used.
1376
1377 message-id = "Message-ID:" msg-id CRLF
1378
1379 in-reply-to = "In-Reply-To:" 1*msg-id CRLF
1380
1381 references = "References:" 1*msg-id CRLF
1382
1383 msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
1384
1385 id-left = dot-atom-text / obs-id-left
1386
1387 id-right = dot-atom-text / no-fold-literal / obs-id-right
1388
1389 no-fold-literal = "[" *dtext "]"
1390
1391 The "Message-ID:" field provides a unique message identifier that
1392 refers to a particular version of a particular message. The
1393 uniqueness of the message identifier is guaranteed by the host that
1394 generates it (see below). This message identifier is intended to be
1395 machine readable and not necessarily meaningful to humans. A message
1396 identifier pertains to exactly one version of a particular message;
1397 subsequent revisions to the message each receive new message
1398 identifiers.
1399
1400
1401
1402 Resnick Standards Track [Page 25]
1403
1404 RFC 5322 Internet Message Format October 2008
1405
1406
1407 Note: There are many instances when messages are "changed", but
1408 those changes do not constitute a new instantiation of that
1409 message, and therefore the message would not get a new message
1410 identifier. For example, when messages are introduced into the
1411 transport system, they are often prepended with additional header
1412 fields such as trace fields (described in section 3.6.7) and
1413 resent fields (described in section 3.6.6). The addition of such
1414 header fields does not change the identity of the message and
1415 therefore the original "Message-ID:" field is retained. In all
1416 cases, it is the meaning that the sender of the message wishes to
1417 convey (i.e., whether this is the same message or a different
1418 message) that determines whether or not the "Message-ID:" field
1419 changes, not any particular syntactic difference that appears (or
1420 does not appear) in the message.
1421
1422 The "In-Reply-To:" and "References:" fields are used when creating a
1423 reply to a message. They hold the message identifier of the original
1424 message and the message identifiers of other messages (for example,
1425 in the case of a reply to a message that was itself a reply). The
1426 "In-Reply-To:" field may be used to identify the message (or
1427 messages) to which the new message is a reply, while the
1428 "References:" field may be used to identify a "thread" of
1429 conversation.
1430
1431 When creating a reply to a message, the "In-Reply-To:" and
1432 "References:" fields of the resultant message are constructed as
1433 follows:
1434
1435 The "In-Reply-To:" field will contain the contents of the
1436 "Message-ID:" field of the message to which this one is a reply (the
1437 "parent message"). If there is more than one parent message, then
1438 the "In-Reply-To:" field will contain the contents of all of the
1439 parents' "Message-ID:" fields. If there is no "Message-ID:" field in
1440 any of the parent messages, then the new message will have no "In-
1441 Reply-To:" field.
1442
1443 The "References:" field will contain the contents of the parent's
1444 "References:" field (if any) followed by the contents of the parent's
1445 "Message-ID:" field (if any). If the parent message does not contain
1446 a "References:" field but does have an "In-Reply-To:" field
1447 containing a single message identifier, then the "References:" field
1448 will contain the contents of the parent's "In-Reply-To:" field
1449 followed by the contents of the parent's "Message-ID:" field (if
1450 any). If the parent has none of the "References:", "In-Reply-To:",
1451 or "Message-ID:" fields, then the new message will have no
1452 "References:" field.
1453
1454
1455
1456
1457
1458 Resnick Standards Track [Page 26]
1459
1460 RFC 5322 Internet Message Format October 2008
1461
1462
1463 Note: Some implementations parse the "References:" field to
1464 display the "thread of the discussion". These implementations
1465 assume that each new message is a reply to a single parent and
1466 hence that they can walk backwards through the "References:" field
1467 to find the parent of each message listed there. Therefore,
1468 trying to form a "References:" field for a reply that has multiple
1469 parents is discouraged; how to do so is not defined in this
1470 document.
1471
1472 The message identifier (msg-id) itself MUST be a globally unique
1473 identifier for a message. The generator of the message identifier
1474 MUST guarantee that the msg-id is unique. There are several
1475 algorithms that can be used to accomplish this. Since the msg-id has
1476 a similar syntax to addr-spec (identical except that quoted strings,
1477 comments, and folding white space are not allowed), a good method is
1478 to put the domain name (or a domain literal IP address) of the host
1479 on which the message identifier was created on the right-hand side of
1480 the "@" (since domain names and IP addresses are normally unique),
1481 and put a combination of the current absolute date and time along
1482 with some other currently unique (perhaps sequential) identifier
1483 available on the system (for example, a process id number) on the
1484 left-hand side. Though other algorithms will work, it is RECOMMENDED
1485 that the right-hand side contain some domain identifier (either of
1486 the host itself or otherwise) such that the generator of the message
1487 identifier can guarantee the uniqueness of the left-hand side within
1488 the scope of that domain.
1489
1490 Semantically, the angle bracket characters are not part of the
1491 msg-id; the msg-id is what is contained between the two angle bracket
1492 characters.
1493
1494 3.6.5. Informational Fields
1495
1496 The informational fields are all optional. The "Subject:" and
1497 "Comments:" fields are unstructured fields as defined in section
1498 2.2.1, and therefore may contain text or folding white space. The
1499 "Keywords:" field contains a comma-separated list of one or more
1500 words or quoted-strings.
1501
1502 subject = "Subject:" unstructured CRLF
1503
1504 comments = "Comments:" unstructured CRLF
1505
1506 keywords = "Keywords:" phrase *("," phrase) CRLF
1507
1508 These three fields are intended to have only human-readable content
1509 with information about the message. The "Subject:" field is the most
1510 common and contains a short string identifying the topic of the
1511
1512
1513
1514 Resnick Standards Track [Page 27]
1515
1516 RFC 5322 Internet Message Format October 2008
1517
1518
1519 message. When used in a reply, the field body MAY start with the
1520 string "Re: " (an abbreviation of the Latin "in re", meaning "in the
1521 matter of") followed by the contents of the "Subject:" field body of
1522 the original message. If this is done, only one instance of the
1523 literal string "Re: " ought to be used since use of other strings or
1524 more than one instance can lead to undesirable consequences. The
1525 "Comments:" field contains any additional comments on the text of the
1526 body of the message. The "Keywords:" field contains a comma-
1527 separated list of important words and phrases that might be useful
1528 for the recipient.
1529
1530 3.6.6. Resent Fields
1531
1532 Resent fields SHOULD be added to any message that is reintroduced by
1533 a user into the transport system. A separate set of resent fields
1534 SHOULD be added each time this is done. All of the resent fields
1535 corresponding to a particular resending of the message SHOULD be
1536 grouped together. Each new set of resent fields is prepended to the
1537 message; that is, the most recent set of resent fields appears
1538 earlier in the message. No other fields in the message are changed
1539 when resent fields are added.
1540
1541 Each of the resent fields corresponds to a particular field elsewhere
1542 in the syntax. For instance, the "Resent-Date:" field corresponds to
1543 the "Date:" field and the "Resent-To:" field corresponds to the "To:"
1544 field. In each case, the syntax for the field body is identical to
1545 the syntax given previously for the corresponding field.
1546
1547 When resent fields are used, the "Resent-From:" and "Resent-Date:"
1548 fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
1549 "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
1550 identical to "Resent-From:".
1551
1552 resent-date = "Resent-Date:" date-time CRLF
1553
1554 resent-from = "Resent-From:" mailbox-list CRLF
1555
1556 resent-sender = "Resent-Sender:" mailbox CRLF
1557
1558 resent-to = "Resent-To:" address-list CRLF
1559
1560 resent-cc = "Resent-Cc:" address-list CRLF
1561
1562 resent-bcc = "Resent-Bcc:" [address-list / CFWS] CRLF
1563
1564 resent-msg-id = "Resent-Message-ID:" msg-id CRLF
1565
1566
1567
1568
1569
1570 Resnick Standards Track [Page 28]
1571
1572 RFC 5322 Internet Message Format October 2008
1573
1574
1575 Resent fields are used to identify a message as having been
1576 reintroduced into the transport system by a user. The purpose of
1577 using resent fields is to have the message appear to the final
1578 recipient as if it were sent directly by the original sender, with
1579 all of the original fields remaining the same. Each set of resent
1580 fields correspond to a particular resending event. That is, if a
1581 message is resent multiple times, each set of resent fields gives
1582 identifying information for each individual time. Resent fields are
1583 strictly informational. They MUST NOT be used in the normal
1584 processing of replies or other such automatic actions on messages.
1585
1586 Note: Reintroducing a message into the transport system and using
1587 resent fields is a different operation from "forwarding".
1588 "Forwarding" has two meanings: One sense of forwarding is that a
1589 mail reading program can be told by a user to forward a copy of a
1590 message to another person, making the forwarded message the body
1591 of the new message. A forwarded message in this sense does not
1592 appear to have come from the original sender, but is an entirely
1593 new message from the forwarder of the message. Forwarding may
1594 also mean that a mail transport program gets a message and
1595 forwards it on to a different destination for final delivery.
1596 Resent header fields are not intended for use with either type of
1597 forwarding.
1598
1599 The resent originator fields indicate the mailbox of the person(s) or
1600 system(s) that resent the message. As with the regular originator
1601 fields, there are two forms: a simple "Resent-From:" form, which
1602 contains the mailbox of the individual doing the resending, and the
1603 more complex form, when one individual (identified in the "Resent-
1604 Sender:" field) resends a message on behalf of one or more others
1605 (identified in the "Resent-From:" field).
1606
1607 Note: When replying to a resent message, replies behave just as
1608 they would with any other message, using the original "From:",
1609 "Reply-To:", "Message-ID:", and other fields. The resent fields
1610 are only informational and MUST NOT be used in the normal
1611 processing of replies.
1612
1613 The "Resent-Date:" indicates the date and time at which the resent
1614 message is dispatched by the resender of the message. Like the
1615 "Date:" field, it is not the date and time that the message was
1616 actually transported.
1617
1618 The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
1619 identically to the "To:", "Cc:", and "Bcc:" fields, respectively,
1620 except that they indicate the recipients of the resent message, not
1621 the recipients of the original message.
1622
1623
1624
1625
1626 Resnick Standards Track [Page 29]
1627
1628 RFC 5322 Internet Message Format October 2008
1629
1630
1631 The "Resent-Message-ID:" field provides a unique identifier for the
1632 resent message.
1633
1634 3.6.7. Trace Fields
1635
1636 The trace fields are a group of header fields consisting of an
1637 optional "Return-Path:" field, and one or more "Received:" fields.
1638 The "Return-Path:" header field contains a pair of angle brackets
1639 that enclose an optional addr-spec. The "Received:" field contains a
1640 (possibly empty) list of tokens followed by a semicolon and a date-
1641 time specification. Each token must be a word, angle-addr, addr-
1642 spec, or a domain. Further restrictions are applied to the syntax of
1643 the trace fields by specifications that provide for their use, such
1644 as [RFC5321].
1645
1646 trace = [return]
1647 1*received
1648
1649 return = "Return-Path:" path CRLF
1650
1651 path = angle-addr / ([CFWS] "<" [CFWS] ">" [CFWS])
1652
1653 received = "Received:" *received-token ";" date-time CRLF
1654
1655 received-token = word / angle-addr / addr-spec / domain
1656
1657 A full discussion of the Internet mail use of trace fields is
1658 contained in [RFC5321]. For the purposes of this specification, the
1659 trace fields are strictly informational, and any formal
1660 interpretation of them is outside of the scope of this document.
1661
1662 3.6.8. Optional Fields
1663
1664 Fields may appear in messages that are otherwise unspecified in this
1665 document. They MUST conform to the syntax of an optional-field.
1666 This is a field name, made up of the printable US-ASCII characters
1667 except SP and colon, followed by a colon, followed by any text that
1668 conforms to the unstructured syntax.
1669
1670 The field names of any optional field MUST NOT be identical to any
1671 field name specified elsewhere in this document.
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682 Resnick Standards Track [Page 30]
1683
1684 RFC 5322 Internet Message Format October 2008
1685
1686
1687 optional-field = field-name ":" unstructured CRLF
1688
1689 field-name = 1*ftext
1690
1691 ftext = %d33-57 / ; Printable US-ASCII
1692 %d59-126 ; characters not including
1693 ; ":".
1694
1695 For the purposes of this specification, any optional field is
1696 uninterpreted.
1697
1698 4. Obsolete Syntax
1699
1700 Earlier versions of this specification allowed for different (usually
1701 more liberal) syntax than is allowed in this version. Also, there
1702 have been syntactic elements used in messages on the Internet whose
1703 interpretations have never been documented. Though these syntactic
1704 forms MUST NOT be generated according to the grammar in section 3,
1705 they MUST be accepted and parsed by a conformant receiver. This
1706 section documents many of these syntactic elements. Taking the
1707 grammar in section 3 and adding the definitions presented in this
1708 section will result in the grammar to use for the interpretation of
1709 messages.
1710
1711 Note: This section identifies syntactic forms that any
1712 implementation MUST reasonably interpret. However, there are
1713 certainly Internet messages that do not conform to even the
1714 additional syntax given in this section. The fact that a
1715 particular form does not appear in any section of this document is
1716 not justification for computer programs to crash or for malformed
1717 data to be irretrievably lost by any implementation. It is up to
1718 the implementation to deal with messages robustly.
1719
1720 One important difference between the obsolete (interpreting) and the
1721 current (generating) syntax is that in structured header field bodies
1722 (i.e., between the colon and the CRLF of any structured header
1723 field), white space characters, including folding white space, and
1724 comments could be freely inserted between any syntactic tokens. This
1725 allowed many complex forms that have proven difficult for some
1726 implementations to parse.
1727
1728 Another key difference between the obsolete and the current syntax is
1729 that the rule in section 3.2.2 regarding lines composed entirely of
1730 white space in comments and folding white space does not apply. See
1731 the discussion of folding white space in section 4.2 below.
1732
1733 Finally, certain characters that were formerly allowed in messages
1734 appear in this section. The NUL character (ASCII value 0) was once
1735
1736
1737
1738 Resnick Standards Track [Page 31]
1739
1740 RFC 5322 Internet Message Format October 2008
1741
1742
1743 allowed, but is no longer for compatibility reasons. Similarly, US-
1744 ASCII control characters other than CR, LF, SP, and HTAB (ASCII
1745 values 1 through 8, 11, 12, 14 through 31, and 127) were allowed to
1746 appear in header field bodies. CR and LF were allowed to appear in
1747 messages other than as CRLF; this use is also shown here.
1748
1749 Other differences in syntax and semantics are noted in the following
1750 sections.
1751
1752 4.1. Miscellaneous Obsolete Tokens
1753
1754 These syntactic elements are used elsewhere in the obsolete syntax or
1755 in the main syntax. Bare CR, bare LF, and NUL are added to obs-qp,
1756 obs-body, and obs-unstruct. US-ASCII control characters are added to
1757 obs-qp, obs-unstruct, obs-ctext, and obs-qtext. The period character
1758 is added to obs-phrase. The obs-phrase-list provides for a
1759 (potentially empty) comma-separated list of phrases that may include
1760 "null" elements. That is, there could be two or more commas in such
1761 a list with nothing in between them, or commas at the beginning or
1762 end of the list.
1763
1764 Note: The "period" (or "full stop") character (".") in obs-phrase
1765 is not a form that was allowed in earlier versions of this or any
1766 other specification. Period (nor any other character from
1767 specials) was not allowed in phrase because it introduced a
1768 parsing difficulty distinguishing between phrases and portions of
1769 an addr-spec (see section 4.4). It appears here because the
1770 period character is currently used in many messages in the
1771 display-name portion of addresses, especially for initials in
1772 names, and therefore must be interpreted properly.
1773
1774 obs-NO-WS-CTL = %d1-8 / ; US-ASCII control
1775 %d11 / ; characters that do not
1776 %d12 / ; include the carriage
1777 %d14-31 / ; return, line feed, and
1778 %d127 ; white space characters
1779
1780 obs-ctext = obs-NO-WS-CTL
1781
1782 obs-qtext = obs-NO-WS-CTL
1783
1784 obs-utext = %d0 / obs-NO-WS-CTL / VCHAR
1785
1786 obs-qp = "\" (%d0 / obs-NO-WS-CTL / LF / CR)
1787
1788 obs-body = *((*LF *CR *((%d0 / text) *LF *CR)) / CRLF)
1789
1790 obs-unstruct = *((*LF *CR *(obs-utext *LF *CR)) / FWS)
1791
1792
1793
1794 Resnick Standards Track [Page 32]
1795
1796 RFC 5322 Internet Message Format October 2008
1797
1798
1799 obs-phrase = word *(word / "." / CFWS)
1800
1801 obs-phrase-list = [phrase / CFWS] *("," [phrase / CFWS])
1802
1803 Bare CR and bare LF appear in messages with two different meanings.
1804 In many cases, bare CR or bare LF are used improperly instead of CRLF
1805 to indicate line separators. In other cases, bare CR and bare LF are
1806 used simply as US-ASCII control characters with their traditional
1807 ASCII meanings.
1808
1809 4.2. Obsolete Folding White Space
1810
1811 In the obsolete syntax, any amount of folding white space MAY be
1812 inserted where the obs-FWS rule is allowed. This creates the
1813 possibility of having two consecutive "folds" in a line, and
1814 therefore the possibility that a line which makes up a folded header
1815 field could be composed entirely of white space.
1816
1817 obs-FWS = 1*WSP *(CRLF 1*WSP)
1818
1819 4.3. Obsolete Date and Time
1820
1821 The syntax for the obsolete date format allows a 2 digit year in the
1822 date field and allows for a list of alphabetic time zone specifiers
1823 that were used in earlier versions of this specification. It also
1824 permits comments and folding white space between many of the tokens.
1825
1826 obs-day-of-week = [CFWS] day-name [CFWS]
1827
1828 obs-day = [CFWS] 1*2DIGIT [CFWS]
1829
1830 obs-year = [CFWS] 2*DIGIT [CFWS]
1831
1832 obs-hour = [CFWS] 2DIGIT [CFWS]
1833
1834 obs-minute = [CFWS] 2DIGIT [CFWS]
1835
1836 obs-second = [CFWS] 2DIGIT [CFWS]
1837
1838 obs-zone = "UT" / "GMT" / ; Universal Time
1839 ; North American UT
1840 ; offsets
1841 "EST" / "EDT" / ; Eastern: - 5/ - 4
1842 "CST" / "CDT" / ; Central: - 6/ - 5
1843 "MST" / "MDT" / ; Mountain: - 7/ - 6
1844 "PST" / "PDT" / ; Pacific: - 8/ - 7
1845 ;
1846
1847
1848
1849
1850 Resnick Standards Track [Page 33]
1851
1852 RFC 5322 Internet Message Format October 2008
1853
1854
1855 %d65-73 / ; Military zones - "A"
1856 %d75-90 / ; through "I" and "K"
1857 %d97-105 / ; through "Z", both
1858 %d107-122 ; upper and lower case
1859
1860 Where a two or three digit year occurs in a date, the year is to be
1861 interpreted as follows: If a two digit year is encountered whose
1862 value is between 00 and 49, the year is interpreted by adding 2000,
1863 ending up with a value between 2000 and 2049. If a two digit year is
1864 encountered with a value between 50 and 99, or any three digit year
1865 is encountered, the year is interpreted by adding 1900.
1866
1867 In the obsolete time zone, "UT" and "GMT" are indications of
1868 "Universal Time" and "Greenwich Mean Time", respectively, and are
1869 both semantically identical to "+0000".
1870
1871 The remaining three character zones are the US time zones. The first
1872 letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
1873 "Mountain", and "Pacific". The second letter is either "S" for
1874 "Standard" time, or "D" for "Daylight Savings" (or summer) time.
1875 Their interpretations are as follows:
1876
1877 EDT is semantically equivalent to -0400
1878 EST is semantically equivalent to -0500
1879 CDT is semantically equivalent to -0500
1880 CST is semantically equivalent to -0600
1881 MDT is semantically equivalent to -0600
1882 MST is semantically equivalent to -0700
1883 PDT is semantically equivalent to -0700
1884 PST is semantically equivalent to -0800
1885
1886 The 1 character military time zones were defined in a non-standard
1887 way in [RFC0822] and are therefore unpredictable in their meaning.
1888 The original definitions of the military zones "A" through "I" are
1889 equivalent to "+0100" through "+0900", respectively; "K", "L", and
1890 "M" are equivalent to "+1000", "+1100", and "+1200", respectively;
1891 "N" through "Y" are equivalent to "-0100" through "-1200".
1892 respectively; and "Z" is equivalent to "+0000". However, because of
1893 the error in [RFC0822], they SHOULD all be considered equivalent to
1894 "-0000" unless there is out-of-band information confirming their
1895 meaning.
1896
1897 Other multi-character (usually between 3 and 5) alphabetic time zones
1898 have been used in Internet messages. Any such time zone whose
1899 meaning is not known SHOULD be considered equivalent to "-0000"
1900 unless there is out-of-band information confirming their meaning.
1901
1902
1903
1904
1905
1906 Resnick Standards Track [Page 34]
1907
1908 RFC 5322 Internet Message Format October 2008
1909
1910
1911 4.4. Obsolete Addressing
1912
1913 There are four primary differences in addressing. First, mailbox
1914 addresses were allowed to have a route portion before the addr-spec
1915 when enclosed in "<" and ">". The route is simply a comma-separated
1916 list of domain names, each preceded by "@", and the list terminated
1917 by a colon. Second, CFWS were allowed between the period-separated
1918 elements of local-part and domain (i.e., dot-atom was not used). In
1919 addition, local-part is allowed to contain quoted-string in addition
1920 to just atom. Third, mailbox-list and address-list were allowed to
1921 have "null" members. That is, there could be two or more commas in
1922 such a list with nothing in between them, or commas at the beginning
1923 or end of the list. Finally, US-ASCII control characters and quoted-
1924 pairs were allowed in domain literals and are added here.
1925
1926 obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
1927
1928 obs-route = obs-domain-list ":"
1929
1930 obs-domain-list = *(CFWS / ",") "@" domain
1931 *("," [CFWS] ["@" domain])
1932
1933 obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
1934
1935 obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
1936
1937 obs-group-list = 1*([CFWS] ",") [CFWS]
1938
1939 obs-local-part = word *("." word)
1940
1941 obs-domain = atom *("." atom)
1942
1943 obs-dtext = obs-NO-WS-CTL / quoted-pair
1944
1945 When interpreting addresses, the route portion SHOULD be ignored.
1946
1947 4.5. Obsolete Header Fields
1948
1949 Syntactically, the primary difference in the obsolete field syntax is
1950 that it allows multiple occurrences of any of the fields and they may
1951 occur in any order. Also, any amount of white space is allowed
1952 before the ":" at the end of the field name.
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962 Resnick Standards Track [Page 35]
1963
1964 RFC 5322 Internet Message Format October 2008
1965
1966
1967 obs-fields = *(obs-return /
1968 obs-received /
1969 obs-orig-date /
1970 obs-from /
1971 obs-sender /
1972 obs-reply-to /
1973 obs-to /
1974 obs-cc /
1975 obs-bcc /
1976 obs-message-id /
1977 obs-in-reply-to /
1978 obs-references /
1979 obs-subject /
1980 obs-comments /
1981 obs-keywords /
1982 obs-resent-date /
1983 obs-resent-from /
1984 obs-resent-send /
1985 obs-resent-rply /
1986 obs-resent-to /
1987 obs-resent-cc /
1988 obs-resent-bcc /
1989 obs-resent-mid /
1990 obs-optional)
1991
1992 Except for destination address fields (described in section 4.5.3),
1993 the interpretation of multiple occurrences of fields is unspecified.
1994 Also, the interpretation of trace fields and resent fields that do
1995 not occur in blocks prepended to the message is unspecified as well.
1996 Unless otherwise noted in the following sections, interpretation of
1997 other fields is identical to the interpretation of their non-obsolete
1998 counterparts in section 3.
1999
2000 4.5.1. Obsolete Origination Date Field
2001
2002 obs-orig-date = "Date" *WSP ":" date-time CRLF
2003
2004 4.5.2. Obsolete Originator Fields
2005
2006 obs-from = "From" *WSP ":" mailbox-list CRLF
2007
2008 obs-sender = "Sender" *WSP ":" mailbox CRLF
2009
2010 obs-reply-to = "Reply-To" *WSP ":" address-list CRLF
2011
2012
2013
2014
2015
2016
2017
2018 Resnick Standards Track [Page 36]
2019
2020 RFC 5322 Internet Message Format October 2008
2021
2022
2023 4.5.3. Obsolete Destination Address Fields
2024
2025 obs-to = "To" *WSP ":" address-list CRLF
2026
2027 obs-cc = "Cc" *WSP ":" address-list CRLF
2028
2029 obs-bcc = "Bcc" *WSP ":"
2030 (address-list / (*([CFWS] ",") [CFWS])) CRLF
2031
2032 When multiple occurrences of destination address fields occur in a
2033 message, they SHOULD be treated as if the address list in the first
2034 occurrence of the field is combined with the address lists of the
2035 subsequent occurrences by adding a comma and concatenating.
2036
2037 4.5.4. Obsolete Identification Fields
2038
2039 The obsolete "In-Reply-To:" and "References:" fields differ from the
2040 current syntax in that they allow phrase (words or quoted strings) to
2041 appear. The obsolete forms of the left and right sides of msg-id
2042 allow interspersed CFWS, making them syntactically identical to
2043 local-part and domain, respectively.
2044
2045 obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
2046
2047 obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
2048
2049 obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
2050
2051 obs-id-left = local-part
2052
2053 obs-id-right = domain
2054
2055 For purposes of interpretation, the phrases in the "In-Reply-To:" and
2056 "References:" fields are ignored.
2057
2058 Semantically, none of the optional CFWS in the local-part and the
2059 domain is part of the obs-id-left and obs-id-right, respectively.
2060
2061 4.5.5. Obsolete Informational Fields
2062
2063 obs-subject = "Subject" *WSP ":" unstructured CRLF
2064
2065 obs-comments = "Comments" *WSP ":" unstructured CRLF
2066
2067 obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
2068
2069
2070
2071
2072
2073
2074 Resnick Standards Track [Page 37]
2075
2076 RFC 5322 Internet Message Format October 2008
2077
2078
2079 4.5.6. Obsolete Resent Fields
2080
2081 The obsolete syntax adds a "Resent-Reply-To:" field, which consists
2082 of the field name, the optional comments and folding white space, the
2083 colon, and a comma separated list of addresses.
2084
2085 obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
2086
2087 obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
2088
2089 obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
2090
2091 obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
2092
2093 obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
2094
2095 obs-resent-bcc = "Resent-Bcc" *WSP ":"
2096 (address-list / (*([CFWS] ",") [CFWS])) CRLF
2097
2098 obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
2099
2100 obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
2101
2102 As with other resent fields, the "Resent-Reply-To:" field is to be
2103 treated as trace information only.
2104
2105 4.5.7. Obsolete Trace Fields
2106
2107 The obs-return and obs-received are again given here as template
2108 definitions, just as return and received are in section 3. Their
2109 full syntax is given in [RFC5321].
2110
2111 obs-return = "Return-Path" *WSP ":" path CRLF
2112
2113 obs-received = "Received" *WSP ":" *received-token CRLF
2114
2115 4.5.8. Obsolete optional fields
2116
2117 obs-optional = field-name *WSP ":" unstructured CRLF
2118
2119 5. Security Considerations
2120
2121 Care needs to be taken when displaying messages on a terminal or
2122 terminal emulator. Powerful terminals may act on escape sequences
2123 and other combinations of US-ASCII control characters with a variety
2124 of consequences. They can remap the keyboard or permit other
2125 modifications to the terminal that could lead to denial of service or
2126 even damaged data. They can trigger (sometimes programmable)
2127
2128
2129
2130 Resnick Standards Track [Page 38]
2131
2132 RFC 5322 Internet Message Format October 2008
2133
2134
2135 answerback messages that can allow a message to cause commands to be
2136 issued on the recipient's behalf. They can also affect the operation
2137 of terminal attached devices such as printers. Message viewers may
2138 wish to strip potentially dangerous terminal escape sequences from
2139 the message prior to display. However, other escape sequences appear
2140 in messages for useful purposes (cf. [ISO.2022.1994], [RFC2045],
2141 [RFC2046], [RFC2047], [RFC2049], [RFC4288], [RFC4289]) and therefore
2142 should not be stripped indiscriminately.
2143
2144 Transmission of non-text objects in messages raises additional
2145 security issues. These issues are discussed in [RFC2045], [RFC2046],
2146 [RFC2047], [RFC2049], [RFC4288], and [RFC4289].
2147
2148 Many implementations use the "Bcc:" (blind carbon copy) field,
2149 described in section 3.6.3, to facilitate sending messages to
2150 recipients without revealing the addresses of one or more of the
2151 addressees to the other recipients. Mishandling this use of "Bcc:"
2152 may disclose confidential information that could eventually lead to
2153 security problems through knowledge of even the existence of a
2154 particular mail address. For example, if using the first method
2155 described in section 3.6.3, where the "Bcc:" line is removed from the
2156 message, blind recipients have no explicit indication that they have
2157 been sent a blind copy, except insofar as their address does not
2158 appear in the header section of a message. Because of this, one of
2159 the blind addressees could potentially send a reply to all of the
2160 shown recipients and accidentally reveal that the message went to the
2161 blind recipient. When the second method from section 3.6.3 is used,
2162 the blind recipient's address appears in the "Bcc:" field of a
2163 separate copy of the message. If the "Bcc:" field sent contains all
2164 of the blind addressees, all of the "Bcc:" recipients will be seen by
2165 each "Bcc:" recipient. Even if a separate message is sent to each
2166 "Bcc:" recipient with only the individual's address, implementations
2167 still need to be careful to process replies to the message as per
2168 section 3.6.3 so as not to accidentally reveal the blind recipient to
2169 other recipients.
2170
2171 6. IANA Considerations
2172
2173 This document updates the registrations that appeared in [RFC4021]
2174 that referred to the definitions in [RFC2822]. IANA has updated the
2175 Permanent Message Header Field Repository with the following header
2176 fields, in accordance with the procedures set out in [RFC3864].
2177
2178 Header field name: Date
2179 Applicable protocol: Mail
2180 Status: standard
2181 Author/Change controller: IETF
2182 Specification document(s): This document (section 3.6.1)
2183
2184
2185
2186 Resnick Standards Track [Page 39]
2187
2188 RFC 5322 Internet Message Format October 2008
2189
2190
2191 Header field name: From
2192 Applicable protocol: Mail
2193 Status: standard
2194 Author/Change controller: IETF
2195 Specification document(s): This document (section 3.6.2)
2196
2197 Header field name: Sender
2198 Applicable protocol: Mail
2199 Status: standard
2200 Author/Change controller: IETF
2201 Specification document(s): This document (section 3.6.2)
2202
2203 Header field name: Reply-To
2204 Applicable protocol: Mail
2205 Status: standard
2206 Author/Change controller: IETF
2207 Specification document(s): This document (section 3.6.2)
2208
2209 Header field name: To
2210 Applicable protocol: Mail
2211 Status: standard
2212 Author/Change controller: IETF
2213 Specification document(s): This document (section 3.6.3)
2214
2215 Header field name: Cc
2216 Applicable protocol: Mail
2217 Status: standard
2218 Author/Change controller: IETF
2219 Specification document(s): This document (section 3.6.3)
2220
2221 Header field name: Bcc
2222 Applicable protocol: Mail
2223 Status: standard
2224 Author/Change controller: IETF
2225 Specification document(s): This document (section 3.6.3)
2226
2227 Header field name: Message-ID
2228 Applicable protocol: Mail
2229 Status: standard
2230 Author/Change controller: IETF
2231 Specification document(s): This document (section 3.6.4)
2232
2233 Header field name: In-Reply-To
2234 Applicable protocol: Mail
2235 Status: standard
2236 Author/Change controller: IETF
2237 Specification document(s): This document (section 3.6.4)
2238
2239
2240
2241
2242 Resnick Standards Track [Page 40]
2243
2244 RFC 5322 Internet Message Format October 2008
2245
2246
2247 Header field name: References
2248 Applicable protocol: Mail
2249 Status: standard
2250 Author/Change controller: IETF
2251 Specification document(s): This document (section 3.6.4)
2252
2253 Header field name: Subject
2254 Applicable protocol: Mail
2255 Status: standard
2256 Author/Change controller: IETF
2257 Specification document(s): This document (section 3.6.5)
2258
2259 Header field name: Comments
2260 Applicable protocol: Mail
2261 Status: standard
2262 Author/Change controller: IETF
2263 Specification document(s): This document (section 3.6.5)
2264
2265 Header field name: Keywords
2266 Applicable protocol: Mail
2267 Status: standard
2268 Author/Change controller: IETF
2269 Specification document(s): This document (section 3.6.5)
2270
2271 Header field name: Resent-Date
2272 Applicable protocol: Mail
2273 Status: standard
2274 Author/Change controller: IETF
2275 Specification document(s): This document (section 3.6.6)
2276
2277 Header field name: Resent-From
2278 Applicable protocol: Mail
2279 Status: standard
2280 Author/Change controller: IETF
2281 Specification document(s): This document (section 3.6.6)
2282
2283 Header field name: Resent-Sender
2284 Applicable protocol: Mail
2285 Status: standard
2286 Author/Change controller: IETF
2287 Specification document(s): This document (section 3.6.6)
2288
2289 Header field name: Resent-To
2290 Applicable protocol: Mail
2291 Status: standard
2292 Author/Change controller: IETF
2293 Specification document(s): This document (section 3.6.6)
2294
2295
2296
2297
2298 Resnick Standards Track [Page 41]
2299
2300 RFC 5322 Internet Message Format October 2008
2301
2302
2303 Header field name: Resent-Cc
2304 Applicable protocol: Mail
2305 Status: standard
2306 Author/Change controller: IETF
2307 Specification document(s): This document (section 3.6.6)
2308
2309 Header field name: Resent-Bcc
2310 Applicable protocol: Mail
2311 Status: standard
2312 Author/Change controller: IETF
2313 Specification document(s): This document (section 3.6.6)
2314
2315 Header field name: Resent-Reply-To
2316 Applicable protocol: Mail
2317 Status: obsolete
2318 Author/Change controller: IETF
2319 Specification document(s): This document (section 4.5.6)
2320
2321 Header field name: Resent-Message-ID
2322 Applicable protocol: Mail
2323 Status: standard
2324 Author/Change controller: IETF
2325 Specification document(s): This document (section 3.6.6)
2326
2327 Header field name: Return-Path
2328 Applicable protocol: Mail
2329 Status: standard
2330 Author/Change controller: IETF
2331 Specification document(s): This document (section 3.6.7)
2332
2333 Header field name: Received
2334 Applicable protocol: Mail
2335 Status: standard
2336 Author/Change controller: IETF
2337 Specification document(s): This document (section 3.6.7)
2338 Related information: [RFC5321]
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354 Resnick Standards Track [Page 42]
2355
2356 RFC 5322 Internet Message Format October 2008
2357
2358
2359 Appendix A. Example Messages
2360
2361 This section presents a selection of messages. These are intended to
2362 assist in the implementation of this specification, but should not be
2363 taken as normative; that is to say, although the examples in this
2364 section were carefully reviewed, if there happens to be a conflict
2365 between these examples and the syntax described in sections 3 and 4
2366 of this document, the syntax in those sections is to be taken as
2367 correct.
2368
2369 In the text version of this document, messages in this section are
2370 delimited between lines of "----". The "----" lines are not part of
2371 the message itself.
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410 Resnick Standards Track [Page 43]
2411
2412 RFC 5322 Internet Message Format October 2008
2413
2414
2415 Appendix A.1. Addressing Examples
2416
2417 The following are examples of messages that might be sent between two
2418 individuals.
2419
2420 Appendix A.1.1. A Message from One Person to Another with Simple
2421 Addressing
2422
2423 This could be called a canonical message. It has a single author,
2424 John Doe, a single recipient, Mary Smith, a subject, the date, a
2425 message identifier, and a textual message in the body.
2426
2427 ----
2428 From: John Doe <jdoe@machine.example>
2429 To: Mary Smith <mary@example.net>
2430 Subject: Saying Hello
2431 Date: Fri, 21 Nov 1997 09:55:06 -0600
2432 Message-ID: <1234@local.machine.example>
2433
2434 This is a message just to say hello.
2435 So, "Hello".
2436 ----
2437
2438 If John's secretary Michael actually sent the message, even though
2439 John was the author and replies to this message should go back to
2440 him, the sender field would be used:
2441
2442 ----
2443 From: John Doe <jdoe@machine.example>
2444 Sender: Michael Jones <mjones@machine.example>
2445 To: Mary Smith <mary@example.net>
2446 Subject: Saying Hello
2447 Date: Fri, 21 Nov 1997 09:55:06 -0600
2448 Message-ID: <1234@local.machine.example>
2449
2450 This is a message just to say hello.
2451 So, "Hello".
2452 ----
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466 Resnick Standards Track [Page 44]
2467
2468 RFC 5322 Internet Message Format October 2008
2469
2470
2471 Appendix A.1.2. Different Types of Mailboxes
2472
2473 This message includes multiple addresses in the destination fields
2474 and also uses several different forms of addresses.
2475
2476 ----
2477 From: "Joe Q. Public" <john.q.public@example.com>
2478 To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
2479 Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
2480 Date: Tue, 1 Jul 2003 10:52:37 +0200
2481 Message-ID: <5678.21-Nov-1997@example.com>
2482
2483 Hi everyone.
2484 ----
2485
2486 Note that the display names for Joe Q. Public and Giant; "Big" Box
2487 needed to be enclosed in double-quotes because the former contains
2488 the period and the latter contains both semicolon and double-quote
2489 characters (the double-quote characters appearing as quoted-pair
2490 constructs). Conversely, the display name for Who? could appear
2491 without them because the question mark is legal in an atom. Notice
2492 also that jdoe@example.org and boss@nil.test have no display names
2493 associated with them at all, and jdoe@example.org uses the simpler
2494 address form without the angle brackets.
2495
2496 Appendix A.1.3. Group Addresses
2497
2498 ----
2499 From: Pete <pete@silly.example>
2500 To: A Group:Ed Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
2501 Cc: Undisclosed recipients:;
2502 Date: Thu, 13 Feb 1969 23:32:54 -0330
2503 Message-ID: <testabcd.1234@silly.example>
2504
2505 Testing.
2506 ----
2507
2508 In this message, the "To:" field has a single group recipient named
2509 "A Group", which contains 3 addresses, and a "Cc:" field with an
2510 empty group recipient named Undisclosed recipients.
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522 Resnick Standards Track [Page 45]
2523
2524 RFC 5322 Internet Message Format October 2008
2525
2526
2527 Appendix A.2. Reply Messages
2528
2529 The following is a series of three messages that make up a
2530 conversation thread between John and Mary. John first sends a
2531 message to Mary, Mary then replies to John's message, and then John
2532 replies to Mary's reply message.
2533
2534 Note especially the "Message-ID:", "References:", and "In-Reply-To:"
2535 fields in each message.
2536
2537 ----
2538 From: John Doe <jdoe@machine.example>
2539 To: Mary Smith <mary@example.net>
2540 Subject: Saying Hello
2541 Date: Fri, 21 Nov 1997 09:55:06 -0600
2542 Message-ID: <1234@local.machine.example>
2543
2544 This is a message just to say hello.
2545 So, "Hello".
2546 ----
2547
2548 When sending replies, the Subject field is often retained, though
2549 prepended with "Re: " as described in section 3.6.5.
2550
2551 ----
2552 From: Mary Smith <mary@example.net>
2553 To: John Doe <jdoe@machine.example>
2554 Reply-To: "Mary Smith: Personal Account" <smith@home.example>
2555 Subject: Re: Saying Hello
2556 Date: Fri, 21 Nov 1997 10:01:10 -0600
2557 Message-ID: <3456@example.net>
2558 In-Reply-To: <1234@local.machine.example>
2559 References: <1234@local.machine.example>
2560
2561 This is a reply to your hello.
2562 ----
2563
2564 Note the "Reply-To:" field in the above message. When John replies
2565 to Mary's message above, the reply should go to the address in the
2566 "Reply-To:" field instead of the address in the "From:" field.
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578 Resnick Standards Track [Page 46]
2579
2580 RFC 5322 Internet Message Format October 2008
2581
2582
2583 ----
2584 To: "Mary Smith: Personal Account" <smith@home.example>
2585 From: John Doe <jdoe@machine.example>
2586 Subject: Re: Saying Hello
2587 Date: Fri, 21 Nov 1997 11:00:00 -0600
2588 Message-ID: <abcd.1234@local.machine.test>
2589 In-Reply-To: <3456@example.net>
2590 References: <1234@local.machine.example> <3456@example.net>
2591
2592 This is a reply to your reply.
2593 ----
2594
2595 Appendix A.3. Resent Messages
2596
2597 Start with the message that has been used as an example several
2598 times:
2599
2600 ----
2601 From: John Doe <jdoe@machine.example>
2602 To: Mary Smith <mary@example.net>
2603 Subject: Saying Hello
2604 Date: Fri, 21 Nov 1997 09:55:06 -0600
2605 Message-ID: <1234@local.machine.example>
2606
2607 This is a message just to say hello.
2608 So, "Hello".
2609 ----
2610
2611 Say that Mary, upon receiving this message, wishes to send a copy of
2612 the message to Jane such that (a) the message would appear to have
2613 come straight from John; (b) if Jane replies to the message, the
2614 reply should go back to John; and (c) all of the original
2615 information, like the date the message was originally sent to Mary,
2616 the message identifier, and the original addressee, is preserved. In
2617 this case, resent fields are prepended to the message:
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634 Resnick Standards Track [Page 47]
2635
2636 RFC 5322 Internet Message Format October 2008
2637
2638
2639 ----
2640 Resent-From: Mary Smith <mary@example.net>
2641 Resent-To: Jane Brown <j-brown@other.example>
2642 Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
2643 Resent-Message-ID: <78910@example.net>
2644 From: John Doe <jdoe@machine.example>
2645 To: Mary Smith <mary@example.net>
2646 Subject: Saying Hello
2647 Date: Fri, 21 Nov 1997 09:55:06 -0600
2648 Message-ID: <1234@local.machine.example>
2649
2650 This is a message just to say hello.
2651 So, "Hello".
2652 ----
2653
2654 If Jane, in turn, wished to resend this message to another person,
2655 she would prepend her own set of resent header fields to the above
2656 and send that. (Note that for brevity, trace fields are not shown.)
2657
2658 Appendix A.4. Messages with Trace Fields
2659
2660 As messages are sent through the transport system as described in
2661 [RFC5321], trace fields are prepended to the message. The following
2662 is an example of what those trace fields might look like. Note that
2663 there is some folding white space in the first one since these lines
2664 can be long.
2665
2666 ----
2667 Received: from x.y.test
2668 by example.net
2669 via TCP
2670 with ESMTP
2671 id ABC12345
2672 for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
2673 Received: from node.example by x.y.test; 21 Nov 1997 10:01:22 -0600
2674 From: John Doe <jdoe@node.example>
2675 To: Mary Smith <mary@example.net>
2676 Subject: Saying Hello
2677 Date: Fri, 21 Nov 1997 09:55:06 -0600
2678 Message-ID: <1234@local.node.example>
2679
2680 This is a message just to say hello.
2681 So, "Hello".
2682 ----
2683
2684
2685
2686
2687
2688
2689
2690 Resnick Standards Track [Page 48]
2691
2692 RFC 5322 Internet Message Format October 2008
2693
2694
2695 Appendix A.5. White Space, Comments, and Other Oddities
2696
2697 White space, including folding white space, and comments can be
2698 inserted between many of the tokens of fields. Taking the example
2699 from A.1.3, white space and comments can be inserted into all of the
2700 fields.
2701
2702 ----
2703 From: Pete(A nice \) chap) <pete(his account)@silly.test(his host)>
2704 To:A Group(Some people)
2705 :Chris Jones <c@(Chris's host.)public.example>,
2706 joe@example.org,
2707 John <jdoe@one.test> (my dear friend); (the end of the group)
2708 Cc:(Empty list)(start)Hidden recipients :(nobody(that I know)) ;
2709 Date: Thu,
2710 13
2711 Feb
2712 1969
2713 23:32
2714 -0330 (Newfoundland Time)
2715 Message-ID: <testabcd.1234@silly.test>
2716
2717 Testing.
2718 ----
2719
2720 The above example is aesthetically displeasing, but perfectly legal.
2721 Note particularly (1) the comments in the "From:" field (including
2722 one that has a ")" character appearing as part of a quoted-pair); (2)
2723 the white space absent after the ":" in the "To:" field as well as
2724 the comment and folding white space after the group name, the special
2725 character (".") in the comment in Chris Jones's address, and the
2726 folding white space before and after "joe@example.org,"; (3) the
2727 multiple and nested comments in the "Cc:" field as well as the
2728 comment immediately following the ":" after "Cc"; (4) the folding
2729 white space (but no comments except at the end) and the missing
2730 seconds in the time of the date field; and (5) the white space before
2731 (but not within) the identifier in the "Message-ID:" field.
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746 Resnick Standards Track [Page 49]
2747
2748 RFC 5322 Internet Message Format October 2008
2749
2750
2751 Appendix A.6. Obsoleted Forms
2752
2753 The following are examples of obsolete (that is, the "MUST NOT
2754 generate") syntactic elements described in section 4 of this
2755 document.
2756
2757 Appendix A.6.1. Obsolete Addressing
2758
2759 Note in the example below the lack of quotes around Joe Q. Public,
2760 the route that appears in the address for Mary Smith, the two commas
2761 that appear in the "To:" field, and the spaces that appear around the
2762 "." in the jdoe address.
2763
2764 ----
2765 From: Joe Q. Public <john.q.public@example.com>
2766 To: Mary Smith <@node.test:mary@example.net>, , jdoe@test . example
2767 Date: Tue, 1 Jul 2003 10:52:37 +0200
2768 Message-ID: <5678.21-Nov-1997@example.com>
2769
2770 Hi everyone.
2771 ----
2772
2773 Appendix A.6.2. Obsolete Dates
2774
2775 The following message uses an obsolete date format, including a non-
2776 numeric time zone and a two digit year. Note that although the day-
2777 of-week is missing, that is not specific to the obsolete syntax; it
2778 is optional in the current syntax as well.
2779
2780 ----
2781 From: John Doe <jdoe@machine.example>
2782 To: Mary Smith <mary@example.net>
2783 Subject: Saying Hello
2784 Date: 21 Nov 97 09:55:06 GMT
2785 Message-ID: <1234@local.machine.example>
2786
2787 This is a message just to say hello.
2788 So, "Hello".
2789 ----
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802 Resnick Standards Track [Page 50]
2803
2804 RFC 5322 Internet Message Format October 2008
2805
2806
2807 Appendix A.6.3. Obsolete White Space and Comments
2808
2809 White space and comments can appear between many more elements than
2810 in the current syntax. Also, folding lines that are made up entirely
2811 of white space are legal.
2812
2813 ----
2814 From : John Doe <jdoe@machine(comment). example>
2815 To : Mary Smith
2816 __
2817 <mary@example.net>
2818 Subject : Saying Hello
2819 Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
2820 Message-ID : <1234 @ local(blah) .machine .example>
2821
2822 This is a message just to say hello.
2823 So, "Hello".
2824 ----
2825
2826 Note especially the second line of the "To:" field. It starts with
2827 two space characters. (Note that "__" represent blank spaces.)
2828 Therefore, it is considered part of the folding, as described in
2829 section 4.2. Also, the comments and white space throughout
2830 addresses, dates, and message identifiers are all part of the
2831 obsolete syntax.
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858 Resnick Standards Track [Page 51]
2859
2860 RFC 5322 Internet Message Format October 2008
2861
2862
2863 Appendix B. Differences from Earlier Specifications
2864
2865 This appendix contains a list of changes that have been made in the
2866 Internet Message Format from earlier specifications, specifically
2867 [RFC0822], [RFC1123], and [RFC2822]. Items marked with an asterisk
2868 (*) below are items which appear in section 4 of this document and
2869 therefore can no longer be generated.
2870
2871 The following are the changes made from [RFC0822] and [RFC1123] to
2872 [RFC2822] that remain in this document:
2873
2874 1. Period allowed in obsolete form of phrase.
2875 2. ABNF moved out of document, now in [RFC5234].
2876 3. Four or more digits allowed for year.
2877 4. Header field ordering (and lack thereof) made explicit.
2878 5. Encrypted header field removed.
2879 6. Specifically allow and give meaning to "-0000" time zone.
2880 7. Folding white space is not allowed between every token.
2881 8. Requirement for destinations removed.
2882 9. Forwarding and resending redefined.
2883 10. Extension header fields no longer specifically called out.
2884 11. ASCII 0 (null) removed.*
2885 12. Folding continuation lines cannot contain only white space.*
2886 13. Free insertion of comments not allowed in date.*
2887 14. Non-numeric time zones not allowed.*
2888 15. Two digit years not allowed.*
2889 16. Three digit years interpreted, but not allowed for generation.*
2890 17. Routes in addresses not allowed.*
2891 18. CFWS within local-parts and domains not allowed.*
2892 19. Empty members of address lists not allowed.*
2893 20. Folding white space between field name and colon not allowed.*
2894 21. Comments between field name and colon not allowed.
2895 22. Tightened syntax of in-reply-to and references.*
2896 23. CFWS within msg-id not allowed.*
2897 24. Tightened semantics of resent fields as informational only.
2898 25. Resent-Reply-To not allowed.*
2899 26. No multiple occurrences of fields (except resent and received).*
2900 27. Free CR and LF not allowed.*
2901 28. Line length limits specified.
2902 29. Bcc more clearly specified.
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914 Resnick Standards Track [Page 52]
2915
2916 RFC 5322 Internet Message Format October 2008
2917
2918
2919 The following are changes from [RFC2822].
2920 1. Assorted typographical/grammatical errors fixed and
2921 clarifications made.
2922 2. Changed "standard" to "document" or "specification" throughout.
2923 3. Made distinction between "header field" and "header section".
2924 4. Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
2925 5. Moved discussion of specials to the "Atom" section. Moved text
2926 to "Overall message syntax" section.
2927 6. Simplified CFWS syntax.
2928 7. Fixed unstructured syntax.
2929 8. Changed date and time syntax to deal with white space in
2930 obsolete date syntax.
2931 9. Removed quoted-pair from domain literals and message
2932 identifiers.*
2933 10. Clarified that other specifications limit domain syntax.
2934 11. Simplified "Bcc:" and "Resent-Bcc:" syntax.
2935 12. Allowed optional-field to appear within trace information.
2936 13. Removed no-fold-quote from msg-id. Clarified syntax
2937 limitations.
2938 14. Generalized "Received:" syntax to fix bugs and move definition
2939 out of this document.
2940 15. Simplified obs-qp. Fixed and simplified obs-utext (which now
2941 only appears in the obsolete syntax). Removed obs-text and obs-
2942 char, adding obs-body.
2943 16. Fixed obsolete date syntax to allow for more (or less) comments
2944 and white space.
2945 17. Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list,
2946 obs-addr-list, obs-phrase-list, and the newly added obs-group-
2947 list).
2948 18. Fixed obs-reply-to syntax.
2949 19. Fixed obs-bcc and obs-resent-bcc to allow empty lists.
2950 20. Removed obs-path.
2951
2952 Appendix C. Acknowledgements
2953
2954 Many people contributed to this document. They included folks who
2955 participated in the Detailed Revision and Update of Messaging
2956 Standards (DRUMS) Working Group of the Internet Engineering Task
2957 Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
2958 people who simply sent their comments in via email. The editor is
2959 deeply indebted to them all and thanks them sincerely. The below
2960 list includes everyone who sent email concerning both this document
2961 and [RFC2822]. Hopefully, everyone who contributed is named here:
2962
2963 +--------------------+----------------------+---------------------+
2964 | Matti Aarnio | Tanaka Akira | Russ Allbery |
2965 | Eric Allman | Harald Alvestrand | Ran Atkinson |
2966 | Jos Backus | Bruce Balden | Dave Barr |
2967
2968
2969
2970 Resnick Standards Track [Page 53]
2971
2972 RFC 5322 Internet Message Format October 2008
2973
2974
2975 | Alan Barrett | John Beck | J Robert von Behren |
2976 | Jos den Bekker | D J Bernstein | James Berriman |
2977 | Oliver Block | Norbert Bollow | Raj Bose |
2978 | Antony Bowesman | Scott Bradner | Randy Bush |
2979 | Tom Byrer | Bruce Campbell | Larry Campbell |
2980 | W J Carpenter | Michael Chapman | Richard Clayton |
2981 | Maurizio Codogno | Jim Conklin | R Kelley Cook |
2982 | Nathan Coulter | Steve Coya | Mark Crispin |
2983 | Dave Crocker | Matt Curtin | Michael D'Errico |
2984 | Cyrus Daboo | Michael D Dean | Jutta Degener |
2985 | Mark Delany | Steve Dorner | Harold A Driscoll |
2986 | Michael Elkins | Frank Ellerman | Robert Elz |
2987 | Johnny Eriksson | Erik E Fair | Roger Fajman |
2988 | Patrik Faltstrom | Claus Andre Faerber | Barry Finkel |
2989 | Erik Forsberg | Chuck Foster | Paul Fox |
2990 | Klaus M Frank | Ned Freed | Jochen Friedrich |
2991 | Randall C Gellens | Sukvinder Singh Gill | Tim Goodwin |
2992 | Philip Guenther | Arnt Gulbrandsen | Eric A Hall |
2993 | Tony Hansen | John Hawkinson | Philip Hazel |
2994 | Kai Henningsen | Robert Herriot | Paul Hethmon |
2995 | Jim Hill | Alfred Hoenes | Paul E Hoffman |
2996 | Steve Hole | Kari Hurtta | Marco S Hyman |
2997 | Ofer Inbar | Olle Jarnefors | Kevin Johnson |
2998 | Sudish Joseph | Maynard Kang | Prabhat Keni |
2999 | John C Klensin | Graham Klyne | Brad Knowles |
3000 | Shuhei Kobayashi | Peter Koch | Dan Kohn |
3001 | Christian Kuhtz | Anand Kumria | Steen Larsen |
3002 | Eliot Lear | Barry Leiba | Jay Levitt |
3003 | Bruce Lilly | Lars-Johan Liman | Charles Lindsey |
3004 | Pete Loshin | Simon Lyall | Bill Manning |
3005 | John Martin | Mark Martinec | Larry Masinter |
3006 | Denis McKeon | William P McQuillan | Alexey Melnikov |
3007 | Perry E Metzger | Steven Miller | S Moonesamy |
3008 | Keith Moore | John Gardiner Myers | Chris Newman |
3009 | John W Noerenberg | Eric Norman | Mike O'Dell |
3010 | Larry Osterman | Paul Overell | Jacob Palme |
3011 | Michael A Patton | Uzi Paz | Michael A Quinlan |
3012 | Robert Rapplean | Eric S Raymond | Sam Roberts |
3013 | Hugh Sasse | Bart Schaefer | Tom Scola |
3014 | Wolfgang Segmuller | Nick Shelness | John Stanley |
3015 | Einar Stefferud | Jeff Stephenson | Bernard Stern |
3016 | Peter Sylvester | Mark Symons | Eric Thomas |
3017 | Lee Thompson | Karel De Vriendt | Matthew Wall |
3018 | Rolf Weber | Brent B Welch | Dan Wing |
3019 | Jack De Winter | Gregory J Woodhouse | Greg A Woods |
3020 | Kazu Yamamoto | Alain Zahm | Jamie Zawinski |
3021 | Timothy S Zurcher | | |
3022 +--------------------+----------------------+---------------------+
3023
3024
3025
3026 Resnick Standards Track [Page 54]
3027
3028 RFC 5322 Internet Message Format October 2008
3029
3030
3031 7. References
3032
3033 7.1. Normative References
3034
3035 [ANSI.X3-4.1986] American National Standards Institute, "Coded
3036 Character Set - 7-bit American Standard Code for
3037 Information Interchange", ANSI X3.4, 1986.
3038
3039 [RFC1034] Mockapetris, P., "Domain names - concepts and
3040 facilities", STD 13, RFC 1034, November 1987.
3041
3042 [RFC1035] Mockapetris, P., "Domain names - implementation and
3043 specification", STD 13, RFC 1035, November 1987.
3044
3045 [RFC1123] Braden, R., "Requirements for Internet Hosts -
3046 Application and Support", STD 3, RFC 1123,
3047 October 1989.
3048
3049 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
3050 Requirement Levels", BCP 14, RFC 2119, March 1997.
3051
3052 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for
3053 Syntax Specifications: ABNF", STD 68, RFC 5234,
3054 January 2008.
3055
3056 7.2. Informative References
3057
3058 [RFC0822] Crocker, D., "Standard for the format of ARPA
3059 Internet text messages", STD 11, RFC 822,
3060 August 1982.
3061
3062 [RFC1305] Mills, D., "Network Time Protocol (Version 3)
3063 Specification, Implementation", RFC 1305,
3064 March 1992.
3065
3066 [ISO.2022.1994] International Organization for Standardization,
3067 "Information technology - Character code structure
3068 and extension techniques", ISO Standard 2022, 1994.
3069
3070 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
3071 Mail Extensions (MIME) Part One: Format of Internet
3072 Message Bodies", RFC 2045, November 1996.
3073
3074 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet
3075 Mail Extensions (MIME) Part Two: Media Types",
3076 RFC 2046, November 1996.
3077
3078
3079
3080
3081
3082 Resnick Standards Track [Page 55]
3083
3084 RFC 5322 Internet Message Format October 2008
3085
3086
3087 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
3088 Extensions) Part Three: Message Header Extensions
3089 for Non-ASCII Text", RFC 2047, November 1996.
3090
3091 [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet
3092 Mail Extensions (MIME) Part Five: Conformance
3093 Criteria and Examples", RFC 2049, November 1996.
3094
3095 [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
3096 April 2001.
3097
3098 [RFC3864] Klyne, G., Nottingham, M., and J. Mogul,
3099 "Registration Procedures for Message Header
3100 Fields", BCP 90, RFC 3864, September 2004.
3101
3102 [RFC4021] Klyne, G. and J. Palme, "Registration of Mail and
3103 MIME Header Fields", RFC 4021, March 2005.
3104
3105 [RFC4288] Freed, N. and J. Klensin, "Media Type
3106 Specifications and Registration Procedures",
3107 BCP 13, RFC 4288, December 2005.
3108
3109 [RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet
3110 Mail Extensions (MIME) Part Four: Registration
3111 Procedures", BCP 13, RFC 4289, December 2005.
3112
3113 [RFC5321] Klensin, J., "Simple Mail Transfer Protocol",
3114 RFC 5321, October 2008.
3115
3116 Author's Address
3117
3118 Peter W. Resnick (editor)
3119 Qualcomm Incorporated
3120 5775 Morehouse Drive
3121 San Diego, CA 92121-1714
3122 US
3123
3124 Phone: +1 858 651 4478
3125 EMail: presnick@qualcomm.com
3126 URI: http://www.qualcomm.com/~presnick/
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138 Resnick Standards Track [Page 56]
3139
3140 RFC 5322 Internet Message Format October 2008
3141
3142
3143 Full Copyright Statement
3144
3145 Copyright (C) The IETF Trust (2008).
3146
3147 This document is subject to the rights, licenses and restrictions
3148 contained in BCP 78, and except as set forth therein, the authors
3149 retain all their rights.
3150
3151 This document and the information contained herein are provided on an
3152 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
3153 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
3154 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
3155 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
3156 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
3157 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
3158
3159 Intellectual Property
3160
3161 The IETF takes no position regarding the validity or scope of any
3162 Intellectual Property Rights or other rights that might be claimed to
3163 pertain to the implementation or use of the technology described in
3164 this document or the extent to which any license under such rights
3165 might or might not be available; nor does it represent that it has
3166 made any independent effort to identify any such rights. Information
3167 on the procedures with respect to rights in RFC documents can be
3168 found in BCP 78 and BCP 79.
3169
3170 Copies of IPR disclosures made to the IETF Secretariat and any
3171 assurances of licenses to be made available, or the result of an
3172 attempt made to obtain a general license or permission for the use of
3173 such proprietary rights by implementers or users of this
3174 specification can be obtained from the IETF on-line IPR repository at
3175 http://www.ietf.org/ipr.
3176
3177 The IETF invites any interested party to bring to its attention any
3178 copyrights, patents or patent applications, or other proprietary
3179 rights that may cover technology that may be required to implement
3180 this standard. Please address the information to the IETF at
3181 ietf-ipr@ietf.org.
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194 Resnick Standards Track [Page 57]
3195