rfc2822.txt - rohrpost - A commandline mail client to change the world as we see it.
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rfc2822.txt (110695B)
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7 Network Working Group P. Resnick, Editor
8 Request for Comments: 2822 QUALCOMM Incorporated
9 Obsoletes: 822 April 2001
10 Category: Standards Track
11
12
13 Internet Message Format
14
15 Status of this Memo
16
17 This document specifies an Internet standards track protocol for the
18 Internet community, and requests discussion and suggestions for
19 improvements. Please refer to the current edition of the "Internet
20 Official Protocol Standards" (STD 1) for the standardization state
21 and status of this protocol. Distribution of this memo is unlimited.
22
23 Copyright Notice
24
25 Copyright (C) The Internet Society (2001). All Rights Reserved.
26
27 Abstract
28
29 This standard specifies a syntax for text messages that are sent
30 between computer users, within the framework of "electronic mail"
31 messages. This standard supersedes the one specified in Request For
32 Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
33 Messages", updating it to reflect current practice and incorporating
34 incremental changes that were specified in other RFCs.
35
36 Table of Contents
37
38 1. Introduction ............................................... 3
39 1.1. Scope .................................................... 3
40 1.2. Notational conventions ................................... 4
41 1.2.1. Requirements notation .................................. 4
42 1.2.2. Syntactic notation ..................................... 4
43 1.3. Structure of this document ............................... 4
44 2. Lexical Analysis of Messages ............................... 5
45 2.1. General Description ...................................... 5
46 2.1.1. Line Length Limits ..................................... 6
47 2.2. Header Fields ............................................ 7
48 2.2.1. Unstructured Header Field Bodies ....................... 7
49 2.2.2. Structured Header Field Bodies ......................... 7
50 2.2.3. Long Header Fields ..................................... 7
51 2.3. Body ..................................................... 8
52 3. Syntax ..................................................... 9
53 3.1. Introduction ............................................. 9
54 3.2. Lexical Tokens ........................................... 9
55
56
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58 Resnick Standards Track [Page 1]
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60 RFC 2822 Internet Message Format April 2001
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62
63 3.2.1. Primitive Tokens ....................................... 9
64 3.2.2. Quoted characters ......................................10
65 3.2.3. Folding white space and comments .......................11
66 3.2.4. Atom ...................................................12
67 3.2.5. Quoted strings .........................................13
68 3.2.6. Miscellaneous tokens ...................................13
69 3.3. Date and Time Specification ..............................14
70 3.4. Address Specification ....................................15
71 3.4.1. Addr-spec specification ................................16
72 3.5 Overall message syntax ....................................17
73 3.6. Field definitions ........................................18
74 3.6.1. The origination date field .............................20
75 3.6.2. Originator fields ......................................21
76 3.6.3. Destination address fields .............................22
77 3.6.4. Identification fields ..................................23
78 3.6.5. Informational fields ...................................26
79 3.6.6. Resent fields ..........................................26
80 3.6.7. Trace fields ...........................................28
81 3.6.8. Optional fields ........................................29
82 4. Obsolete Syntax ............................................29
83 4.1. Miscellaneous obsolete tokens ............................30
84 4.2. Obsolete folding white space .............................31
85 4.3. Obsolete Date and Time ...................................31
86 4.4. Obsolete Addressing ......................................33
87 4.5. Obsolete header fields ...................................33
88 4.5.1. Obsolete origination date field ........................34
89 4.5.2. Obsolete originator fields .............................34
90 4.5.3. Obsolete destination address fields ....................34
91 4.5.4. Obsolete identification fields .........................35
92 4.5.5. Obsolete informational fields ..........................35
93 4.5.6. Obsolete resent fields .................................35
94 4.5.7. Obsolete trace fields ..................................36
95 4.5.8. Obsolete optional fields ...............................36
96 5. Security Considerations ....................................36
97 6. Bibliography ...............................................37
98 7. Editor's Address ...........................................38
99 8. Acknowledgements ...........................................39
100 Appendix A. Example messages ..................................41
101 A.1. Addressing examples ......................................41
102 A.1.1. A message from one person to another with simple
103 addressing .............................................41
104 A.1.2. Different types of mailboxes ...........................42
105 A.1.3. Group addresses ........................................43
106 A.2. Reply messages ...........................................43
107 A.3. Resent messages ..........................................44
108 A.4. Messages with trace fields ...............................46
109 A.5. White space, comments, and other oddities ................47
110 A.6. Obsoleted forms ..........................................47
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119 A.6.1. Obsolete addressing ....................................48
120 A.6.2. Obsolete dates .........................................48
121 A.6.3. Obsolete white space and comments ......................48
122 Appendix B. Differences from earlier standards ................49
123 Appendix C. Notices ...........................................50
124 Full Copyright Statement ......................................51
125
126 1. Introduction
127
128 1.1. Scope
129
130 This standard specifies a syntax for text messages that are sent
131 between computer users, within the framework of "electronic mail"
132 messages. This standard supersedes the one specified in Request For
133 Comments (RFC) 822, "Standard for the Format of ARPA Internet Text
134 Messages" [RFC822], updating it to reflect current practice and
135 incorporating incremental changes that were specified in other RFCs
136 [STD3].
137
138 This standard specifies a syntax only for text messages. In
139 particular, it makes no provision for the transmission of images,
140 audio, or other sorts of structured data in electronic mail messages.
141 There are several extensions published, such as the MIME document
142 series [RFC2045, RFC2046, RFC2049], which describe mechanisms for the
143 transmission of such data through electronic mail, either by
144 extending the syntax provided here or by structuring such messages to
145 conform to this syntax. Those mechanisms are outside of the scope of
146 this standard.
147
148 In the context of electronic mail, messages are viewed as having an
149 envelope and contents. The envelope contains whatever information is
150 needed to accomplish transmission and delivery. (See [RFC2821] for a
151 discussion of the envelope.) The contents comprise the object to be
152 delivered to the recipient. This standard applies only to the format
153 and some of the semantics of message contents. It contains no
154 specification of the information in the envelope.
155
156 However, some message systems may use information from the contents
157 to create the envelope. It is intended that this standard facilitate
158 the acquisition of such information by programs.
159
160 This specification is intended as a definition of what message
161 content format is to be passed between systems. Though some message
162 systems locally store messages in this format (which eliminates the
163 need for translation between formats) and others use formats that
164 differ from the one specified in this standard, local storage is
165 outside of the scope of this standard.
166
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172 RFC 2822 Internet Message Format April 2001
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174
175 Note: This standard is not intended to dictate the internal formats
176 used by sites, the specific message system features that they are
177 expected to support, or any of the characteristics of user interface
178 programs that create or read messages. In addition, this standard
179 does not specify an encoding of the characters for either transport
180 or storage; that is, it does not specify the number of bits used or
181 how those bits are specifically transferred over the wire or stored
182 on disk.
183
184 1.2. Notational conventions
185
186 1.2.1. Requirements notation
187
188 This document occasionally uses terms that appear in capital letters.
189 When the terms "MUST", "SHOULD", "RECOMMENDED", "MUST NOT", "SHOULD
190 NOT", and "MAY" appear capitalized, they are being used to indicate
191 particular requirements of this specification. A discussion of the
192 meanings of these terms appears in [RFC2119].
193
194 1.2.2. Syntactic notation
195
196 This standard uses the Augmented Backus-Naur Form (ABNF) notation
197 specified in [RFC2234] for the formal definitions of the syntax of
198 messages. Characters will be specified either by a decimal value
199 (e.g., the value %d65 for uppercase A and %d97 for lowercase A) or by
200 a case-insensitive literal value enclosed in quotation marks (e.g.,
201 "A" for either uppercase or lowercase A). See [RFC2234] for the full
202 description of the notation.
203
204 1.3. Structure of this document
205
206 This document is divided into several sections.
207
208 This section, section 1, is a short introduction to the document.
209
210 Section 2 lays out the general description of a message and its
211 constituent parts. This is an overview to help the reader understand
212 some of the general principles used in the later portions of this
213 document. Any examples in this section MUST NOT be taken as
214 specification of the formal syntax of any part of a message.
215
216 Section 3 specifies formal ABNF rules for the structure of each part
217 of a message (the syntax) and describes the relationship between
218 those parts and their meaning in the context of a message (the
219 semantics). That is, it describes the actual rules for the structure
220 of each part of a message (the syntax) as well as a description of
221 the parts and instructions on how they ought to be interpreted (the
222 semantics). This includes analysis of the syntax and semantics of
223
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228 RFC 2822 Internet Message Format April 2001
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231 subparts of messages that have specific structure. The syntax
232 included in section 3 represents messages as they MUST be created.
233 There are also notes in section 3 to indicate if any of the options
234 specified in the syntax SHOULD be used over any of the others.
235
236 Both sections 2 and 3 describe messages that are legal to generate
237 for purposes of this standard.
238
239 Section 4 of this document specifies an "obsolete" syntax. There are
240 references in section 3 to these obsolete syntactic elements. The
241 rules of the obsolete syntax are elements that have appeared in
242 earlier revisions of this standard or have previously been widely
243 used in Internet messages. As such, these elements MUST be
244 interpreted by parsers of messages in order to be conformant to this
245 standard. However, since items in this syntax have been determined
246 to be non-interoperable or to cause significant problems for
247 recipients of messages, they MUST NOT be generated by creators of
248 conformant messages.
249
250 Section 5 details security considerations to take into account when
251 implementing this standard.
252
253 Section 6 is a bibliography of references in this document.
254
255 Section 7 contains the editor's address.
256
257 Section 8 contains acknowledgements.
258
259 Appendix A lists examples of different sorts of messages. These
260 examples are not exhaustive of the types of messages that appear on
261 the Internet, but give a broad overview of certain syntactic forms.
262
263 Appendix B lists the differences between this standard and earlier
264 standards for Internet messages.
265
266 Appendix C has copyright and intellectual property notices.
267
268 2. Lexical Analysis of Messages
269
270 2.1. General Description
271
272 At the most basic level, a message is a series of characters. A
273 message that is conformant with this standard is comprised of
274 characters with values in the range 1 through 127 and interpreted as
275 US-ASCII characters [ASCII]. For brevity, this document sometimes
276 refers to this range of characters as simply "US-ASCII characters".
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286
287 Note: This standard specifies that messages are made up of characters
288 in the US-ASCII range of 1 through 127. There are other documents,
289 specifically the MIME document series [RFC2045, RFC2046, RFC2047,
290 RFC2048, RFC2049], that extend this standard to allow for values
291 outside of that range. Discussion of those mechanisms is not within
292 the scope of this standard.
293
294 Messages are divided into lines of characters. A line is a series of
295 characters that is delimited with the two characters carriage-return
296 and line-feed; that is, the carriage return (CR) character (ASCII
297 value 13) followed immediately by the line feed (LF) character (ASCII
298 value 10). (The carriage-return/line-feed pair is usually written in
299 this document as "CRLF".)
300
301 A message consists of header fields (collectively called "the header
302 of the message") followed, optionally, by a body. The header is a
303 sequence of lines of characters with special syntax as defined in
304 this standard. The body is simply a sequence of characters that
305 follows the header and is separated from the header by an empty line
306 (i.e., a line with nothing preceding the CRLF).
307
308 2.1.1. Line Length Limits
309
310 There are two limits that this standard places on the number of
311 characters in a line. Each line of characters MUST be no more than
312 998 characters, and SHOULD be no more than 78 characters, excluding
313 the CRLF.
314
315 The 998 character limit is due to limitations in many implementations
316 which send, receive, or store Internet Message Format messages that
317 simply cannot handle more than 998 characters on a line. Receiving
318 implementations would do well to handle an arbitrarily large number
319 of characters in a line for robustness sake. However, there are so
320 many implementations which (in compliance with the transport
321 requirements of [RFC2821]) do not accept messages containing more
322 than 1000 character including the CR and LF per line, it is important
323 for implementations not to create such messages.
324
325 The more conservative 78 character recommendation is to accommodate
326 the many implementations of user interfaces that display these
327 messages which may truncate, or disastrously wrap, the display of
328 more than 78 characters per line, in spite of the fact that such
329 implementations are non-conformant to the intent of this
330 specification (and that of [RFC2821] if they actually cause
331 information to be lost). Again, even though this limitation is put on
332 messages, it is encumbant upon implementations which display messages
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340 RFC 2822 Internet Message Format April 2001
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343 to handle an arbitrarily large number of characters in a line
344 (certainly at least up to the 998 character limit) for the sake of
345 robustness.
346
347 2.2. Header Fields
348
349 Header fields are lines composed of a field name, followed by a colon
350 (":"), followed by a field body, and terminated by CRLF. A field
351 name MUST be composed of printable US-ASCII characters (i.e.,
352 characters that have values between 33 and 126, inclusive), except
353 colon. A field body may be composed of any US-ASCII characters,
354 except for CR and LF. However, a field body may contain CRLF when
355 used in header "folding" and "unfolding" as described in section
356 2.2.3. All field bodies MUST conform to the syntax described in
357 sections 3 and 4 of this standard.
358
359 2.2.1. Unstructured Header Field Bodies
360
361 Some field bodies in this standard are defined simply as
362 "unstructured" (which is specified below as any US-ASCII characters,
363 except for CR and LF) with no further restrictions. These are
364 referred to as unstructured field bodies. Semantically, unstructured
365 field bodies are simply to be treated as a single line of characters
366 with no further processing (except for header "folding" and
367 "unfolding" as described in section 2.2.3).
368
369 2.2.2. Structured Header Field Bodies
370
371 Some field bodies in this standard have specific syntactical
372 structure more restrictive than the unstructured field bodies
373 described above. These are referred to as "structured" field bodies.
374 Structured field bodies are sequences of specific lexical tokens as
375 described in sections 3 and 4 of this standard. Many of these tokens
376 are allowed (according to their syntax) to be introduced or end with
377 comments (as described in section 3.2.3) as well as the space (SP,
378 ASCII value 32) and horizontal tab (HTAB, ASCII value 9) characters
379 (together known as the white space characters, WSP), and those WSP
380 characters are subject to header "folding" and "unfolding" as
381 described in section 2.2.3. Semantic analysis of structured field
382 bodies is given along with their syntax.
383
384 2.2.3. Long Header Fields
385
386 Each header field is logically a single line of characters comprising
387 the field name, the colon, and the field body. For convenience
388 however, and to deal with the 998/78 character limitations per line,
389 the field body portion of a header field can be split into a multiple
390 line representation; this is called "folding". The general rule is
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399 that wherever this standard allows for folding white space (not
400 simply WSP characters), a CRLF may be inserted before any WSP. For
401 example, the header field:
402
403 Subject: This is a test
404
405 can be represented as:
406
407 Subject: This
408 is a test
409
410 Note: Though structured field bodies are defined in such a way that
411 folding can take place between many of the lexical tokens (and even
412 within some of the lexical tokens), folding SHOULD be limited to
413 placing the CRLF at higher-level syntactic breaks. For instance, if
414 a field body is defined as comma-separated values, it is recommended
415 that folding occur after the comma separating the structured items in
416 preference to other places where the field could be folded, even if
417 it is allowed elsewhere.
418
419 The process of moving from this folded multiple-line representation
420 of a header field to its single line representation is called
421 "unfolding". Unfolding is accomplished by simply removing any CRLF
422 that is immediately followed by WSP. Each header field should be
423 treated in its unfolded form for further syntactic and semantic
424 evaluation.
425
426 2.3. Body
427
428 The body of a message is simply lines of US-ASCII characters. The
429 only two limitations on the body are as follows:
430
431 - CR and LF MUST only occur together as CRLF; they MUST NOT appear
432 independently in the body.
433
434 - Lines of characters in the body MUST be limited to 998 characters,
435 and SHOULD be limited to 78 characters, excluding the CRLF.
436
437 Note: As was stated earlier, there are other standards documents,
438 specifically the MIME documents [RFC2045, RFC2046, RFC2048, RFC2049]
439 that extend this standard to allow for different sorts of message
440 bodies. Again, these mechanisms are beyond the scope of this
441 document.
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454
455 3. Syntax
456
457 3.1. Introduction
458
459 The syntax as given in this section defines the legal syntax of
460 Internet messages. Messages that are conformant to this standard
461 MUST conform to the syntax in this section. If there are options in
462 this section where one option SHOULD be generated, that is indicated
463 either in the prose or in a comment next to the syntax.
464
465 For the defined expressions, a short description of the syntax and
466 use is given, followed by the syntax in ABNF, followed by a semantic
467 analysis. Primitive tokens that are used but otherwise unspecified
468 come from [RFC2234].
469
470 In some of the definitions, there will be nonterminals whose names
471 start with "obs-". These "obs-" elements refer to tokens defined in
472 the obsolete syntax in section 4. In all cases, these productions
473 are to be ignored for the purposes of generating legal Internet
474 messages and MUST NOT be used as part of such a message. However,
475 when interpreting messages, these tokens MUST be honored as part of
476 the legal syntax. In this sense, section 3 defines a grammar for
477 generation of messages, with "obs-" elements that are to be ignored,
478 while section 4 adds grammar for interpretation of messages.
479
480 3.2. Lexical Tokens
481
482 The following rules are used to define an underlying lexical
483 analyzer, which feeds tokens to the higher-level parsers. This
484 section defines the tokens used in structured header field bodies.
485
486 Note: Readers of this standard need to pay special attention to how
487 these lexical tokens are used in both the lower-level and
488 higher-level syntax later in the document. Particularly, the white
489 space tokens and the comment tokens defined in section 3.2.3 get used
490 in the lower-level tokens defined here, and those lower-level tokens
491 are in turn used as parts of the higher-level tokens defined later.
492 Therefore, the white space and comments may be allowed in the
493 higher-level tokens even though they may not explicitly appear in a
494 particular definition.
495
496 3.2.1. Primitive Tokens
497
498 The following are primitive tokens referred to elsewhere in this
499 standard, but not otherwise defined in [RFC2234]. Some of them will
500 not appear anywhere else in the syntax, but they are convenient to
501 refer to in other parts of this document.
502
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510
511 Note: The "specials" below are just such an example. Though the
512 specials token does not appear anywhere else in this standard, it is
513 useful for implementers who use tools that lexically analyze
514 messages. Each of the characters in specials can be used to indicate
515 a tokenization point in lexical analysis.
516
517 NO-WS-CTL = %d1-8 / ; US-ASCII control characters
518 %d11 / ; that do not include the
519 %d12 / ; carriage return, line feed,
520 %d14-31 / ; and white space characters
521 %d127
522
523 text = %d1-9 / ; Characters excluding CR and LF
524 %d11 /
525 %d12 /
526 %d14-127 /
527 obs-text
528
529 specials = "(" / ")" / ; Special characters used in
530 "<" / ">" / ; other parts of the syntax
531 "[" / "]" /
532 ":" / ";" /
533 "@" / "\" /
534 "," / "." /
535 DQUOTE
536
537 No special semantics are attached to these tokens. They are simply
538 single characters.
539
540 3.2.2. Quoted characters
541
542 Some characters are reserved for special interpretation, such as
543 delimiting lexical tokens. To permit use of these characters as
544 uninterpreted data, a quoting mechanism is provided.
545
546 quoted-pair = ("\" text) / obs-qp
547
548 Where any quoted-pair appears, it is to be interpreted as the text
549 character alone. That is to say, the "\" character that appears as
550 part of a quoted-pair is semantically "invisible".
551
552 Note: The "\" character may appear in a message where it is not part
553 of a quoted-pair. A "\" character that does not appear in a
554 quoted-pair is not semantically invisible. The only places in this
555 standard where quoted-pair currently appears are ccontent, qcontent,
556 dcontent, no-fold-quote, and no-fold-literal.
557
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566
567 3.2.3. Folding white space and comments
568
569 White space characters, including white space used in folding
570 (described in section 2.2.3), may appear between many elements in
571 header field bodies. Also, strings of characters that are treated as
572 comments may be included in structured field bodies as characters
573 enclosed in parentheses. The following defines the folding white
574 space (FWS) and comment constructs.
575
576 Strings of characters enclosed in parentheses are considered comments
577 so long as they do not appear within a "quoted-string", as defined in
578 section 3.2.5. Comments may nest.
579
580 There are several places in this standard where comments and FWS may
581 be freely inserted. To accommodate that syntax, an additional token
582 for "CFWS" is defined for places where comments and/or FWS can occur.
583 However, where CFWS occurs in this standard, it MUST NOT be inserted
584 in such a way that any line of a folded header field is made up
585 entirely of WSP characters and nothing else.
586
587 FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
588 obs-FWS
589
590 ctext = NO-WS-CTL / ; Non white space controls
591
592 %d33-39 / ; The rest of the US-ASCII
593 %d42-91 / ; characters not including "(",
594 %d93-126 ; ")", or "\"
595
596 ccontent = ctext / quoted-pair / comment
597
598 comment = "(" *([FWS] ccontent) [FWS] ")"
599
600 CFWS = *([FWS] comment) (([FWS] comment) / FWS)
601
602 Throughout this standard, where FWS (the folding white space token)
603 appears, it indicates a place where header folding, as discussed in
604 section 2.2.3, may take place. Wherever header folding appears in a
605 message (that is, a header field body containing a CRLF followed by
606 any WSP), header unfolding (removal of the CRLF) is performed before
607 any further lexical analysis is performed on that header field
608 according to this standard. That is to say, any CRLF that appears in
609 FWS is semantically "invisible."
610
611 A comment is normally used in a structured field body to provide some
612 human readable informational text. Since a comment is allowed to
613 contain FWS, folding is permitted within the comment. Also note that
614 since quoted-pair is allowed in a comment, the parentheses and
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622
623 backslash characters may appear in a comment so long as they appear
624 as a quoted-pair. Semantically, the enclosing parentheses are not
625 part of the comment; the comment is what is contained between the two
626 parentheses. As stated earlier, the "\" in any quoted-pair and the
627 CRLF in any FWS that appears within the comment are semantically
628 "invisible" and therefore not part of the comment either.
629
630 Runs of FWS, comment or CFWS that occur between lexical tokens in a
631 structured field header are semantically interpreted as a single
632 space character.
633
634 3.2.4. Atom
635
636 Several productions in structured header field bodies are simply
637 strings of certain basic characters. Such productions are called
638 atoms.
639
640 Some of the structured header field bodies also allow the period
641 character (".", ASCII value 46) within runs of atext. An additional
642 "dot-atom" token is defined for those purposes.
643
644 atext = ALPHA / DIGIT / ; Any character except controls,
645 "!" / "#" / ; SP, and specials.
646 "$" / "%" / ; Used for atoms
647 "&" / "'" /
648 "*" / "+" /
649 "-" / "/" /
650 "=" / "?" /
651 "^" / "_" /
652 "`" / "{" /
653 "|" / "}" /
654 "~"
655
656 atom = [CFWS] 1*atext [CFWS]
657
658 dot-atom = [CFWS] dot-atom-text [CFWS]
659
660 dot-atom-text = 1*atext *("." 1*atext)
661
662 Both atom and dot-atom are interpreted as a single unit, comprised of
663 the string of characters that make it up. Semantically, the optional
664 comments and FWS surrounding the rest of the characters are not part
665 of the atom; the atom is only the run of atext characters in an atom,
666 or the atext and "." characters in a dot-atom.
667
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678
679 3.2.5. Quoted strings
680
681 Strings of characters that include characters other than those
682 allowed in atoms may be represented in a quoted string format, where
683 the characters are surrounded by quote (DQUOTE, ASCII value 34)
684 characters.
685
686 qtext = NO-WS-CTL / ; Non white space controls
687
688 %d33 / ; The rest of the US-ASCII
689 %d35-91 / ; characters not including "\"
690 %d93-126 ; or the quote character
691
692 qcontent = qtext / quoted-pair
693
694 quoted-string = [CFWS]
695 DQUOTE *([FWS] qcontent) [FWS] DQUOTE
696 [CFWS]
697
698 A quoted-string is treated as a unit. That is, quoted-string is
699 identical to atom, semantically. Since a quoted-string is allowed to
700 contain FWS, folding is permitted. Also note that since quoted-pair
701 is allowed in a quoted-string, the quote and backslash characters may
702 appear in a quoted-string so long as they appear as a quoted-pair.
703
704 Semantically, neither the optional CFWS outside of the quote
705 characters nor the quote characters themselves are part of the
706 quoted-string; the quoted-string is what is contained between the two
707 quote characters. As stated earlier, the "\" in any quoted-pair and
708 the CRLF in any FWS/CFWS that appears within the quoted-string are
709 semantically "invisible" and therefore not part of the quoted-string
710 either.
711
712 3.2.6. Miscellaneous tokens
713
714 Three additional tokens are defined, word and phrase for combinations
715 of atoms and/or quoted-strings, and unstructured for use in
716 unstructured header fields and in some places within structured
717 header fields.
718
719 word = atom / quoted-string
720
721 phrase = 1*word / obs-phrase
722
723
724
725
726
727
728
729
730 Resnick Standards Track [Page 13]
731
732 RFC 2822 Internet Message Format April 2001
733
734
735 utext = NO-WS-CTL / ; Non white space controls
736 %d33-126 / ; The rest of US-ASCII
737 obs-utext
738
739 unstructured = *([FWS] utext) [FWS]
740
741 3.3. Date and Time Specification
742
743 Date and time occur in several header fields. This section specifies
744 the syntax for a full date and time specification. Though folding
745 white space is permitted throughout the date-time specification, it
746 is RECOMMENDED that a single space be used in each place that FWS
747 appears (whether it is required or optional); some older
748 implementations may not interpret other occurrences of folding white
749 space correctly.
750
751 date-time = [ day-of-week "," ] date FWS time [CFWS]
752
753 day-of-week = ([FWS] day-name) / obs-day-of-week
754
755 day-name = "Mon" / "Tue" / "Wed" / "Thu" /
756 "Fri" / "Sat" / "Sun"
757
758 date = day month year
759
760 year = 4*DIGIT / obs-year
761
762 month = (FWS month-name FWS) / obs-month
763
764 month-name = "Jan" / "Feb" / "Mar" / "Apr" /
765 "May" / "Jun" / "Jul" / "Aug" /
766 "Sep" / "Oct" / "Nov" / "Dec"
767
768 day = ([FWS] 1*2DIGIT) / obs-day
769
770 time = time-of-day FWS zone
771
772 time-of-day = hour ":" minute [ ":" second ]
773
774 hour = 2DIGIT / obs-hour
775
776 minute = 2DIGIT / obs-minute
777
778 second = 2DIGIT / obs-second
779
780 zone = (( "+" / "-" ) 4DIGIT) / obs-zone
781
782
783
784
785
786 Resnick Standards Track [Page 14]
787
788 RFC 2822 Internet Message Format April 2001
789
790
791 The day is the numeric day of the month. The year is any numeric
792 year 1900 or later.
793
794 The time-of-day specifies the number of hours, minutes, and
795 optionally seconds since midnight of the date indicated.
796
797 The date and time-of-day SHOULD express local time.
798
799 The zone specifies the offset from Coordinated Universal Time (UTC,
800 formerly referred to as "Greenwich Mean Time") that the date and
801 time-of-day represent. The "+" or "-" indicates whether the
802 time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
803 Universal Time. The first two digits indicate the number of hours
804 difference from Universal Time, and the last two digits indicate the
805 number of minutes difference from Universal Time. (Hence, +hhmm
806 means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
807 minutes). The form "+0000" SHOULD be used to indicate a time zone at
808 Universal Time. Though "-0000" also indicates Universal Time, it is
809 used to indicate that the time was generated on a system that may be
810 in a local time zone other than Universal Time and therefore
811 indicates that the date-time contains no information about the local
812 time zone.
813
814 A date-time specification MUST be semantically valid. That is, the
815 day-of-the-week (if included) MUST be the day implied by the date,
816 the numeric day-of-month MUST be between 1 and the number of days
817 allowed for the specified month (in the specified year), the
818 time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
819 number of seconds allowing for a leap second; see [STD12]), and the
820 zone MUST be within the range -9959 through +9959.
821
822 3.4. Address Specification
823
824 Addresses occur in several message header fields to indicate senders
825 and recipients of messages. An address may either be an individual
826 mailbox, or a group of mailboxes.
827
828 address = mailbox / group
829
830 mailbox = name-addr / addr-spec
831
832 name-addr = [display-name] angle-addr
833
834 angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
835
836 group = display-name ":" [mailbox-list / CFWS] ";"
837 [CFWS]
838
839
840
841
842 Resnick Standards Track [Page 15]
843
844 RFC 2822 Internet Message Format April 2001
845
846
847 display-name = phrase
848
849 mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
850
851 address-list = (address *("," address)) / obs-addr-list
852
853 A mailbox receives mail. It is a conceptual entity which does not
854 necessarily pertain to file storage. For example, some sites may
855 choose to print mail on a printer and deliver the output to the
856 addressee's desk. Normally, a mailbox is comprised of two parts: (1)
857 an optional display name that indicates the name of the recipient
858 (which could be a person or a system) that could be displayed to the
859 user of a mail application, and (2) an addr-spec address enclosed in
860 angle brackets ("<" and ">"). There is also an alternate simple form
861 of a mailbox where the addr-spec address appears alone, without the
862 recipient's name or the angle brackets. The Internet addr-spec
863 address is described in section 3.4.1.
864
865 Note: Some legacy implementations used the simple form where the
866 addr-spec appears without the angle brackets, but included the name
867 of the recipient in parentheses as a comment following the addr-spec.
868 Since the meaning of the information in a comment is unspecified,
869 implementations SHOULD use the full name-addr form of the mailbox,
870 instead of the legacy form, to specify the display name associated
871 with a mailbox. Also, because some legacy implementations interpret
872 the comment, comments generally SHOULD NOT be used in address fields
873 to avoid confusing such implementations.
874
875 When it is desirable to treat several mailboxes as a single unit
876 (i.e., in a distribution list), the group construct can be used. The
877 group construct allows the sender to indicate a named group of
878 recipients. This is done by giving a display name for the group,
879 followed by a colon, followed by a comma separated list of any number
880 of mailboxes (including zero and one), and ending with a semicolon.
881 Because the list of mailboxes can be empty, using the group construct
882 is also a simple way to communicate to recipients that the message
883 was sent to one or more named sets of recipients, without actually
884 providing the individual mailbox address for each of those
885 recipients.
886
887 3.4.1. Addr-spec specification
888
889 An addr-spec is a specific Internet identifier that contains a
890 locally interpreted string followed by the at-sign character ("@",
891 ASCII value 64) followed by an Internet domain. The locally
892 interpreted string is either a quoted-string or a dot-atom. If the
893 string can be represented as a dot-atom (that is, it contains no
894 characters other than atext characters or "." surrounded by atext
895
896
897
898 Resnick Standards Track [Page 16]
899
900 RFC 2822 Internet Message Format April 2001
901
902
903 characters), then the dot-atom form SHOULD be used and the
904 quoted-string form SHOULD NOT be used. Comments and folding white
905 space SHOULD NOT be used around the "@" in the addr-spec.
906
907 addr-spec = local-part "@" domain
908
909 local-part = dot-atom / quoted-string / obs-local-part
910
911 domain = dot-atom / domain-literal / obs-domain
912
913 domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
914
915 dcontent = dtext / quoted-pair
916
917 dtext = NO-WS-CTL / ; Non white space controls
918
919 %d33-90 / ; The rest of the US-ASCII
920 %d94-126 ; characters not including "[",
921 ; "]", or "\"
922
923 The domain portion identifies the point to which the mail is
924 delivered. In the dot-atom form, this is interpreted as an Internet
925 domain name (either a host name or a mail exchanger name) as
926 described in [STD3, STD13, STD14]. In the domain-literal form, the
927 domain is interpreted as the literal Internet address of the
928 particular host. In both cases, how addressing is used and how
929 messages are transported to a particular host is covered in the mail
930 transport document [RFC2821]. These mechanisms are outside of the
931 scope of this document.
932
933 The local-part portion is a domain dependent string. In addresses,
934 it is simply interpreted on the particular host as a name of a
935 particular mailbox.
936
937 3.5 Overall message syntax
938
939 A message consists of header fields, optionally followed by a message
940 body. Lines in a message MUST be a maximum of 998 characters
941 excluding the CRLF, but it is RECOMMENDED that lines be limited to 78
942 characters excluding the CRLF. (See section 2.1.1 for explanation.)
943 In a message body, though all of the characters listed in the text
944 rule MAY be used, the use of US-ASCII control characters (values 1
945 through 8, 11, 12, and 14 through 31) is discouraged since their
946 interpretation by receivers for display is not guaranteed.
947
948
949
950
951
952
953
954 Resnick Standards Track [Page 17]
955
956 RFC 2822 Internet Message Format April 2001
957
958
959 message = (fields / obs-fields)
960 [CRLF body]
961
962 body = *(*998text CRLF) *998text
963
964 The header fields carry most of the semantic information and are
965 defined in section 3.6. The body is simply a series of lines of text
966 which are uninterpreted for the purposes of this standard.
967
968 3.6. Field definitions
969
970 The header fields of a message are defined here. All header fields
971 have the same general syntactic structure: A field name, followed by
972 a colon, followed by the field body. The specific syntax for each
973 header field is defined in the subsequent sections.
974
975 Note: In the ABNF syntax for each field in subsequent sections, each
976 field name is followed by the required colon. However, for brevity
977 sometimes the colon is not referred to in the textual description of
978 the syntax. It is, nonetheless, required.
979
980 It is important to note that the header fields are not guaranteed to
981 be in a particular order. They may appear in any order, and they
982 have been known to be reordered occasionally when transported over
983 the Internet. However, for the purposes of this standard, header
984 fields SHOULD NOT be reordered when a message is transported or
985 transformed. More importantly, the trace header fields and resent
986 header fields MUST NOT be reordered, and SHOULD be kept in blocks
987 prepended to the message. See sections 3.6.6 and 3.6.7 for more
988 information.
989
990 The only required header fields are the origination date field and
991 the originator address field(s). All other header fields are
992 syntactically optional. More information is contained in the table
993 following this definition.
994
995 fields = *(trace
996 *(resent-date /
997 resent-from /
998 resent-sender /
999 resent-to /
1000 resent-cc /
1001 resent-bcc /
1002 resent-msg-id))
1003 *(orig-date /
1004 from /
1005 sender /
1006 reply-to /
1007
1008
1009
1010 Resnick Standards Track [Page 18]
1011
1012 RFC 2822 Internet Message Format April 2001
1013
1014
1015 to /
1016 cc /
1017 bcc /
1018 message-id /
1019 in-reply-to /
1020 references /
1021 subject /
1022 comments /
1023 keywords /
1024 optional-field)
1025
1026 The following table indicates limits on the number of times each
1027 field may occur in a message header as well as any special
1028 limitations on the use of those fields. An asterisk next to a value
1029 in the minimum or maximum column indicates that a special restriction
1030 appears in the Notes column.
1031
1032 Field Min number Max number Notes
1033
1034 trace 0 unlimited Block prepended - see
1035 3.6.7
1036
1037 resent-date 0* unlimited* One per block, required
1038 if other resent fields
1039 present - see 3.6.6
1040
1041 resent-from 0 unlimited* One per block - see
1042 3.6.6
1043
1044 resent-sender 0* unlimited* One per block, MUST
1045 occur with multi-address
1046 resent-from - see 3.6.6
1047
1048 resent-to 0 unlimited* One per block - see
1049 3.6.6
1050
1051 resent-cc 0 unlimited* One per block - see
1052 3.6.6
1053
1054 resent-bcc 0 unlimited* One per block - see
1055 3.6.6
1056
1057 resent-msg-id 0 unlimited* One per block - see
1058 3.6.6
1059
1060 orig-date 1 1
1061
1062 from 1 1 See sender and 3.6.2
1063
1064
1065
1066 Resnick Standards Track [Page 19]
1067
1068 RFC 2822 Internet Message Format April 2001
1069
1070
1071 sender 0* 1 MUST occur with multi-
1072 address from - see 3.6.2
1073
1074 reply-to 0 1
1075
1076 to 0 1
1077
1078 cc 0 1
1079
1080 bcc 0 1
1081
1082 message-id 0* 1 SHOULD be present - see
1083 3.6.4
1084
1085 in-reply-to 0* 1 SHOULD occur in some
1086 replies - see 3.6.4
1087
1088 references 0* 1 SHOULD occur in some
1089 replies - see 3.6.4
1090
1091 subject 0 1
1092
1093 comments 0 unlimited
1094
1095 keywords 0 unlimited
1096
1097 optional-field 0 unlimited
1098
1099 The exact interpretation of each field is described in subsequent
1100 sections.
1101
1102 3.6.1. The origination date field
1103
1104 The origination date field consists of the field name "Date" followed
1105 by a date-time specification.
1106
1107 orig-date = "Date:" date-time CRLF
1108
1109 The origination date specifies the date and time at which the creator
1110 of the message indicated that the message was complete and ready to
1111 enter the mail delivery system. For instance, this might be the time
1112 that a user pushes the "send" or "submit" button in an application
1113 program. In any case, it is specifically not intended to convey the
1114 time that the message is actually transported, but rather the time at
1115 which the human or other creator of the message has put the message
1116 into its final form, ready for transport. (For example, a portable
1117 computer user who is not connected to a network might queue a message
1118
1119
1120
1121
1122 Resnick Standards Track [Page 20]
1123
1124 RFC 2822 Internet Message Format April 2001
1125
1126
1127 for delivery. The origination date is intended to contain the date
1128 and time that the user queued the message, not the time when the user
1129 connected to the network to send the message.)
1130
1131 3.6.2. Originator fields
1132
1133 The originator fields of a message consist of the from field, the
1134 sender field (when applicable), and optionally the reply-to field.
1135 The from field consists of the field name "From" and a
1136 comma-separated list of one or more mailbox specifications. If the
1137 from field contains more than one mailbox specification in the
1138 mailbox-list, then the sender field, containing the field name
1139 "Sender" and a single mailbox specification, MUST appear in the
1140 message. In either case, an optional reply-to field MAY also be
1141 included, which contains the field name "Reply-To" and a
1142 comma-separated list of one or more addresses.
1143
1144 from = "From:" mailbox-list CRLF
1145
1146 sender = "Sender:" mailbox CRLF
1147
1148 reply-to = "Reply-To:" address-list CRLF
1149
1150 The originator fields indicate the mailbox(es) of the source of the
1151 message. The "From:" field specifies the author(s) of the message,
1152 that is, the mailbox(es) of the person(s) or system(s) responsible
1153 for the writing of the message. The "Sender:" field specifies the
1154 mailbox of the agent responsible for the actual transmission of the
1155 message. For example, if a secretary were to send a message for
1156 another person, the mailbox of the secretary would appear in the
1157 "Sender:" field and the mailbox of the actual author would appear in
1158 the "From:" field. If the originator of the message can be indicated
1159 by a single mailbox and the author and transmitter are identical, the
1160 "Sender:" field SHOULD NOT be used. Otherwise, both fields SHOULD
1161 appear.
1162
1163 The originator fields also provide the information required when
1164 replying to a message. When the "Reply-To:" field is present, it
1165 indicates the mailbox(es) to which the author of the message suggests
1166 that replies be sent. In the absence of the "Reply-To:" field,
1167 replies SHOULD by default be sent to the mailbox(es) specified in the
1168 "From:" field unless otherwise specified by the person composing the
1169 reply.
1170
1171 In all cases, the "From:" field SHOULD NOT contain any mailbox that
1172 does not belong to the author(s) of the message. See also section
1173 3.6.3 for more information on forming the destination addresses for a
1174 reply.
1175
1176
1177
1178 Resnick Standards Track [Page 21]
1179
1180 RFC 2822 Internet Message Format April 2001
1181
1182
1183 3.6.3. Destination address fields
1184
1185 The destination fields of a message consist of three possible fields,
1186 each of the same form: The field name, which is either "To", "Cc", or
1187 "Bcc", followed by a comma-separated list of one or more addresses
1188 (either mailbox or group syntax).
1189
1190 to = "To:" address-list CRLF
1191
1192 cc = "Cc:" address-list CRLF
1193
1194 bcc = "Bcc:" (address-list / [CFWS]) CRLF
1195
1196 The destination fields specify the recipients of the message. Each
1197 destination field may have one or more addresses, and each of the
1198 addresses indicate the intended recipients of the message. The only
1199 difference between the three fields is how each is used.
1200
1201 The "To:" field contains the address(es) of the primary recipient(s)
1202 of the message.
1203
1204 The "Cc:" field (where the "Cc" means "Carbon Copy" in the sense of
1205 making a copy on a typewriter using carbon paper) contains the
1206 addresses of others who are to receive the message, though the
1207 content of the message may not be directed at them.
1208
1209 The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains
1210 addresses of recipients of the message whose addresses are not to be
1211 revealed to other recipients of the message. There are three ways in
1212 which the "Bcc:" field is used. In the first case, when a message
1213 containing a "Bcc:" field is prepared to be sent, the "Bcc:" line is
1214 removed even though all of the recipients (including those specified
1215 in the "Bcc:" field) are sent a copy of the message. In the second
1216 case, recipients specified in the "To:" and "Cc:" lines each are sent
1217 a copy of the message with the "Bcc:" line removed as above, but the
1218 recipients on the "Bcc:" line get a separate copy of the message
1219 containing a "Bcc:" line. (When there are multiple recipient
1220 addresses in the "Bcc:" field, some implementations actually send a
1221 separate copy of the message to each recipient with a "Bcc:"
1222 containing only the address of that particular recipient.) Finally,
1223 since a "Bcc:" field may contain no addresses, a "Bcc:" field can be
1224 sent without any addresses indicating to the recipients that blind
1225 copies were sent to someone. Which method to use with "Bcc:" fields
1226 is implementation dependent, but refer to the "Security
1227 Considerations" section of this document for a discussion of each.
1228
1229
1230
1231
1232
1233
1234 Resnick Standards Track [Page 22]
1235
1236 RFC 2822 Internet Message Format April 2001
1237
1238
1239 When a message is a reply to another message, the mailboxes of the
1240 authors of the original message (the mailboxes in the "From:" field)
1241 or mailboxes specified in the "Reply-To:" field (if it exists) MAY
1242 appear in the "To:" field of the reply since these would normally be
1243 the primary recipients of the reply. If a reply is sent to a message
1244 that has destination fields, it is often desirable to send a copy of
1245 the reply to all of the recipients of the message, in addition to the
1246 author. When such a reply is formed, addresses in the "To:" and
1247 "Cc:" fields of the original message MAY appear in the "Cc:" field of
1248 the reply, since these are normally secondary recipients of the
1249 reply. If a "Bcc:" field is present in the original message,
1250 addresses in that field MAY appear in the "Bcc:" field of the reply,
1251 but SHOULD NOT appear in the "To:" or "Cc:" fields.
1252
1253 Note: Some mail applications have automatic reply commands that
1254 include the destination addresses of the original message in the
1255 destination addresses of the reply. How those reply commands behave
1256 is implementation dependent and is beyond the scope of this document.
1257 In particular, whether or not to include the original destination
1258 addresses when the original message had a "Reply-To:" field is not
1259 addressed here.
1260
1261 3.6.4. Identification fields
1262
1263 Though optional, every message SHOULD have a "Message-ID:" field.
1264 Furthermore, reply messages SHOULD have "In-Reply-To:" and
1265 "References:" fields as appropriate, as described below.
1266
1267 The "Message-ID:" field contains a single unique message identifier.
1268 The "References:" and "In-Reply-To:" field each contain one or more
1269 unique message identifiers, optionally separated by CFWS.
1270
1271 The message identifier (msg-id) is similar in syntax to an angle-addr
1272 construct without the internal CFWS.
1273
1274 message-id = "Message-ID:" msg-id CRLF
1275
1276 in-reply-to = "In-Reply-To:" 1*msg-id CRLF
1277
1278 references = "References:" 1*msg-id CRLF
1279
1280 msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
1281
1282 id-left = dot-atom-text / no-fold-quote / obs-id-left
1283
1284 id-right = dot-atom-text / no-fold-literal / obs-id-right
1285
1286 no-fold-quote = DQUOTE *(qtext / quoted-pair) DQUOTE
1287
1288
1289
1290 Resnick Standards Track [Page 23]
1291
1292 RFC 2822 Internet Message Format April 2001
1293
1294
1295 no-fold-literal = "[" *(dtext / quoted-pair) "]"
1296
1297 The "Message-ID:" field provides a unique message identifier that
1298 refers to a particular version of a particular message. The
1299 uniqueness of the message identifier is guaranteed by the host that
1300 generates it (see below). This message identifier is intended to be
1301 machine readable and not necessarily meaningful to humans. A message
1302 identifier pertains to exactly one instantiation of a particular
1303 message; subsequent revisions to the message each receive new message
1304 identifiers.
1305
1306 Note: There are many instances when messages are "changed", but those
1307 changes do not constitute a new instantiation of that message, and
1308 therefore the message would not get a new message identifier. For
1309 example, when messages are introduced into the transport system, they
1310 are often prepended with additional header fields such as trace
1311 fields (described in section 3.6.7) and resent fields (described in
1312 section 3.6.6). The addition of such header fields does not change
1313 the identity of the message and therefore the original "Message-ID:"
1314 field is retained. In all cases, it is the meaning that the sender
1315 of the message wishes to convey (i.e., whether this is the same
1316 message or a different message) that determines whether or not the
1317 "Message-ID:" field changes, not any particular syntactic difference
1318 that appears (or does not appear) in the message.
1319
1320 The "In-Reply-To:" and "References:" fields are used when creating a
1321 reply to a message. They hold the message identifier of the original
1322 message and the message identifiers of other messages (for example,
1323 in the case of a reply to a message which was itself a reply). The
1324 "In-Reply-To:" field may be used to identify the message (or
1325 messages) to which the new message is a reply, while the
1326 "References:" field may be used to identify a "thread" of
1327 conversation.
1328
1329 When creating a reply to a message, the "In-Reply-To:" and
1330 "References:" fields of the resultant message are constructed as
1331 follows:
1332
1333 The "In-Reply-To:" field will contain the contents of the "Message-
1334 ID:" field of the message to which this one is a reply (the "parent
1335 message"). If there is more than one parent message, then the "In-
1336 Reply-To:" field will contain the contents of all of the parents'
1337 "Message-ID:" fields. If there is no "Message-ID:" field in any of
1338 the parent messages, then the new message will have no "In-Reply-To:"
1339 field.
1340
1341
1342
1343
1344
1345
1346 Resnick Standards Track [Page 24]
1347
1348 RFC 2822 Internet Message Format April 2001
1349
1350
1351 The "References:" field will contain the contents of the parent's
1352 "References:" field (if any) followed by the contents of the parent's
1353 "Message-ID:" field (if any). If the parent message does not contain
1354 a "References:" field but does have an "In-Reply-To:" field
1355 containing a single message identifier, then the "References:" field
1356 will contain the contents of the parent's "In-Reply-To:" field
1357 followed by the contents of the parent's "Message-ID:" field (if
1358 any). If the parent has none of the "References:", "In-Reply-To:",
1359 or "Message-ID:" fields, then the new message will have no
1360 "References:" field.
1361
1362 Note: Some implementations parse the "References:" field to display
1363 the "thread of the discussion". These implementations assume that
1364 each new message is a reply to a single parent and hence that they
1365 can walk backwards through the "References:" field to find the parent
1366 of each message listed there. Therefore, trying to form a
1367 "References:" field for a reply that has multiple parents is
1368 discouraged and how to do so is not defined in this document.
1369
1370 The message identifier (msg-id) itself MUST be a globally unique
1371 identifier for a message. The generator of the message identifier
1372 MUST guarantee that the msg-id is unique. There are several
1373 algorithms that can be used to accomplish this. Since the msg-id has
1374 a similar syntax to angle-addr (identical except that comments and
1375 folding white space are not allowed), a good method is to put the
1376 domain name (or a domain literal IP address) of the host on which the
1377 message identifier was created on the right hand side of the "@", and
1378 put a combination of the current absolute date and time along with
1379 some other currently unique (perhaps sequential) identifier available
1380 on the system (for example, a process id number) on the left hand
1381 side. Using a date on the left hand side and a domain name or domain
1382 literal on the right hand side makes it possible to guarantee
1383 uniqueness since no two hosts use the same domain name or IP address
1384 at the same time. Though other algorithms will work, it is
1385 RECOMMENDED that the right hand side contain some domain identifier
1386 (either of the host itself or otherwise) such that the generator of
1387 the message identifier can guarantee the uniqueness of the left hand
1388 side within the scope of that domain.
1389
1390 Semantically, the angle bracket characters are not part of the
1391 msg-id; the msg-id is what is contained between the two angle bracket
1392 characters.
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402 Resnick Standards Track [Page 25]
1403
1404 RFC 2822 Internet Message Format April 2001
1405
1406
1407 3.6.5. Informational fields
1408
1409 The informational fields are all optional. The "Keywords:" field
1410 contains a comma-separated list of one or more words or
1411 quoted-strings. The "Subject:" and "Comments:" fields are
1412 unstructured fields as defined in section 2.2.1, and therefore may
1413 contain text or folding white space.
1414
1415 subject = "Subject:" unstructured CRLF
1416
1417 comments = "Comments:" unstructured CRLF
1418
1419 keywords = "Keywords:" phrase *("," phrase) CRLF
1420
1421 These three fields are intended to have only human-readable content
1422 with information about the message. The "Subject:" field is the most
1423 common and contains a short string identifying the topic of the
1424 message. When used in a reply, the field body MAY start with the
1425 string "Re: " (from the Latin "res", in the matter of) followed by
1426 the contents of the "Subject:" field body of the original message.
1427 If this is done, only one instance of the literal string "Re: " ought
1428 to be used since use of other strings or more than one instance can
1429 lead to undesirable consequences. The "Comments:" field contains any
1430 additional comments on the text of the body of the message. The
1431 "Keywords:" field contains a comma-separated list of important words
1432 and phrases that might be useful for the recipient.
1433
1434 3.6.6. Resent fields
1435
1436 Resent fields SHOULD be added to any message that is reintroduced by
1437 a user into the transport system. A separate set of resent fields
1438 SHOULD be added each time this is done. All of the resent fields
1439 corresponding to a particular resending of the message SHOULD be
1440 together. Each new set of resent fields is prepended to the message;
1441 that is, the most recent set of resent fields appear earlier in the
1442 message. No other fields in the message are changed when resent
1443 fields are added.
1444
1445 Each of the resent fields corresponds to a particular field elsewhere
1446 in the syntax. For instance, the "Resent-Date:" field corresponds to
1447 the "Date:" field and the "Resent-To:" field corresponds to the "To:"
1448 field. In each case, the syntax for the field body is identical to
1449 the syntax given previously for the corresponding field.
1450
1451 When resent fields are used, the "Resent-From:" and "Resent-Date:"
1452 fields MUST be sent. The "Resent-Message-ID:" field SHOULD be sent.
1453 "Resent-Sender:" SHOULD NOT be used if "Resent-Sender:" would be
1454 identical to "Resent-From:".
1455
1456
1457
1458 Resnick Standards Track [Page 26]
1459
1460 RFC 2822 Internet Message Format April 2001
1461
1462
1463 resent-date = "Resent-Date:" date-time CRLF
1464
1465 resent-from = "Resent-From:" mailbox-list CRLF
1466
1467 resent-sender = "Resent-Sender:" mailbox CRLF
1468
1469 resent-to = "Resent-To:" address-list CRLF
1470
1471 resent-cc = "Resent-Cc:" address-list CRLF
1472
1473 resent-bcc = "Resent-Bcc:" (address-list / [CFWS]) CRLF
1474
1475 resent-msg-id = "Resent-Message-ID:" msg-id CRLF
1476
1477 Resent fields are used to identify a message as having been
1478 reintroduced into the transport system by a user. The purpose of
1479 using resent fields is to have the message appear to the final
1480 recipient as if it were sent directly by the original sender, with
1481 all of the original fields remaining the same. Each set of resent
1482 fields correspond to a particular resending event. That is, if a
1483 message is resent multiple times, each set of resent fields gives
1484 identifying information for each individual time. Resent fields are
1485 strictly informational. They MUST NOT be used in the normal
1486 processing of replies or other such automatic actions on messages.
1487
1488 Note: Reintroducing a message into the transport system and using
1489 resent fields is a different operation from "forwarding".
1490 "Forwarding" has two meanings: One sense of forwarding is that a mail
1491 reading program can be told by a user to forward a copy of a message
1492 to another person, making the forwarded message the body of the new
1493 message. A forwarded message in this sense does not appear to have
1494 come from the original sender, but is an entirely new message from
1495 the forwarder of the message. On the other hand, forwarding is also
1496 used to mean when a mail transport program gets a message and
1497 forwards it on to a different destination for final delivery. Resent
1498 header fields are not intended for use with either type of
1499 forwarding.
1500
1501 The resent originator fields indicate the mailbox of the person(s) or
1502 system(s) that resent the message. As with the regular originator
1503 fields, there are two forms: a simple "Resent-From:" form which
1504 contains the mailbox of the individual doing the resending, and the
1505 more complex form, when one individual (identified in the
1506 "Resent-Sender:" field) resends a message on behalf of one or more
1507 others (identified in the "Resent-From:" field).
1508
1509 Note: When replying to a resent message, replies behave just as they
1510 would with any other message, using the original "From:",
1511
1512
1513
1514 Resnick Standards Track [Page 27]
1515
1516 RFC 2822 Internet Message Format April 2001
1517
1518
1519 "Reply-To:", "Message-ID:", and other fields. The resent fields are
1520 only informational and MUST NOT be used in the normal processing of
1521 replies.
1522
1523 The "Resent-Date:" indicates the date and time at which the resent
1524 message is dispatched by the resender of the message. Like the
1525 "Date:" field, it is not the date and time that the message was
1526 actually transported.
1527
1528 The "Resent-To:", "Resent-Cc:", and "Resent-Bcc:" fields function
1529 identically to the "To:", "Cc:", and "Bcc:" fields respectively,
1530 except that they indicate the recipients of the resent message, not
1531 the recipients of the original message.
1532
1533 The "Resent-Message-ID:" field provides a unique identifier for the
1534 resent message.
1535
1536 3.6.7. Trace fields
1537
1538 The trace fields are a group of header fields consisting of an
1539 optional "Return-Path:" field, and one or more "Received:" fields.
1540 The "Return-Path:" header field contains a pair of angle brackets
1541 that enclose an optional addr-spec. The "Received:" field contains a
1542 (possibly empty) list of name/value pairs followed by a semicolon and
1543 a date-time specification. The first item of the name/value pair is
1544 defined by item-name, and the second item is either an addr-spec, an
1545 atom, a domain, or a msg-id. Further restrictions may be applied to
1546 the syntax of the trace fields by standards that provide for their
1547 use, such as [RFC2821].
1548
1549 trace = [return]
1550 1*received
1551
1552 return = "Return-Path:" path CRLF
1553
1554 path = ([CFWS] "<" ([CFWS] / addr-spec) ">" [CFWS]) /
1555 obs-path
1556
1557 received = "Received:" name-val-list ";" date-time CRLF
1558
1559 name-val-list = [CFWS] [name-val-pair *(CFWS name-val-pair)]
1560
1561 name-val-pair = item-name CFWS item-value
1562
1563 item-name = ALPHA *(["-"] (ALPHA / DIGIT))
1564
1565 item-value = 1*angle-addr / addr-spec /
1566 atom / domain / msg-id
1567
1568
1569
1570 Resnick Standards Track [Page 28]
1571
1572 RFC 2822 Internet Message Format April 2001
1573
1574
1575 A full discussion of the Internet mail use of trace fields is
1576 contained in [RFC2821]. For the purposes of this standard, the trace
1577 fields are strictly informational, and any formal interpretation of
1578 them is outside of the scope of this document.
1579
1580 3.6.8. Optional fields
1581
1582 Fields may appear in messages that are otherwise unspecified in this
1583 standard. They MUST conform to the syntax of an optional-field.
1584 This is a field name, made up of the printable US-ASCII characters
1585 except SP and colon, followed by a colon, followed by any text which
1586 conforms to unstructured.
1587
1588 The field names of any optional-field MUST NOT be identical to any
1589 field name specified elsewhere in this standard.
1590
1591 optional-field = field-name ":" unstructured CRLF
1592
1593 field-name = 1*ftext
1594
1595 ftext = %d33-57 / ; Any character except
1596 %d59-126 ; controls, SP, and
1597 ; ":".
1598
1599 For the purposes of this standard, any optional field is
1600 uninterpreted.
1601
1602 4. Obsolete Syntax
1603
1604 Earlier versions of this standard allowed for different (usually more
1605 liberal) syntax than is allowed in this version. Also, there have
1606 been syntactic elements used in messages on the Internet whose
1607 interpretation have never been documented. Though some of these
1608 syntactic forms MUST NOT be generated according to the grammar in
1609 section 3, they MUST be accepted and parsed by a conformant receiver.
1610 This section documents many of these syntactic elements. Taking the
1611 grammar in section 3 and adding the definitions presented in this
1612 section will result in the grammar to use for interpretation of
1613 messages.
1614
1615 Note: This section identifies syntactic forms that any implementation
1616 MUST reasonably interpret. However, there are certainly Internet
1617 messages which do not conform to even the additional syntax given in
1618 this section. The fact that a particular form does not appear in any
1619 section of this document is not justification for computer programs
1620 to crash or for malformed data to be irretrievably lost by any
1621 implementation. To repeat an example, though this document requires
1622 lines in messages to be no longer than 998 characters, silently
1623
1624
1625
1626 Resnick Standards Track [Page 29]
1627
1628 RFC 2822 Internet Message Format April 2001
1629
1630
1631 discarding the 999th and subsequent characters in a line without
1632 warning would still be bad behavior for an implementation. It is up
1633 to the implementation to deal with messages robustly.
1634
1635 One important difference between the obsolete (interpreting) and the
1636 current (generating) syntax is that in structured header field bodies
1637 (i.e., between the colon and the CRLF of any structured header
1638 field), white space characters, including folding white space, and
1639 comments can be freely inserted between any syntactic tokens. This
1640 allows many complex forms that have proven difficult for some
1641 implementations to parse.
1642
1643 Another key difference between the obsolete and the current syntax is
1644 that the rule in section 3.2.3 regarding lines composed entirely of
1645 white space in comments and folding white space does not apply. See
1646 the discussion of folding white space in section 4.2 below.
1647
1648 Finally, certain characters that were formerly allowed in messages
1649 appear in this section. The NUL character (ASCII value 0) was once
1650 allowed, but is no longer for compatibility reasons. CR and LF were
1651 allowed to appear in messages other than as CRLF; this use is also
1652 shown here.
1653
1654 Other differences in syntax and semantics are noted in the following
1655 sections.
1656
1657 4.1. Miscellaneous obsolete tokens
1658
1659 These syntactic elements are used elsewhere in the obsolete syntax or
1660 in the main syntax. The obs-char and obs-qp elements each add ASCII
1661 value 0. Bare CR and bare LF are added to obs-text and obs-utext.
1662 The period character is added to obs-phrase. The obs-phrase-list
1663 provides for "empty" elements in a comma-separated list of phrases.
1664
1665 Note: The "period" (or "full stop") character (".") in obs-phrase is
1666 not a form that was allowed in earlier versions of this or any other
1667 standard. Period (nor any other character from specials) was not
1668 allowed in phrase because it introduced a parsing difficulty
1669 distinguishing between phrases and portions of an addr-spec (see
1670 section 4.4). It appears here because the period character is
1671 currently used in many messages in the display-name portion of
1672 addresses, especially for initials in names, and therefore must be
1673 interpreted properly. In the future, period may appear in the
1674 regular syntax of phrase.
1675
1676 obs-qp = "\" (%d0-127)
1677
1678 obs-text = *LF *CR *(obs-char *LF *CR)
1679
1680
1681
1682 Resnick Standards Track [Page 30]
1683
1684 RFC 2822 Internet Message Format April 2001
1685
1686
1687 obs-char = %d0-9 / %d11 / ; %d0-127 except CR and
1688 %d12 / %d14-127 ; LF
1689
1690 obs-utext = obs-text
1691
1692 obs-phrase = word *(word / "." / CFWS)
1693
1694 obs-phrase-list = phrase / 1*([phrase] [CFWS] "," [CFWS]) [phrase]
1695
1696 Bare CR and bare LF appear in messages with two different meanings.
1697 In many cases, bare CR or bare LF are used improperly instead of CRLF
1698 to indicate line separators. In other cases, bare CR and bare LF are
1699 used simply as ASCII control characters with their traditional ASCII
1700 meanings.
1701
1702 4.2. Obsolete folding white space
1703
1704 In the obsolete syntax, any amount of folding white space MAY be
1705 inserted where the obs-FWS rule is allowed. This creates the
1706 possibility of having two consecutive "folds" in a line, and
1707 therefore the possibility that a line which makes up a folded header
1708 field could be composed entirely of white space.
1709
1710 obs-FWS = 1*WSP *(CRLF 1*WSP)
1711
1712 4.3. Obsolete Date and Time
1713
1714 The syntax for the obsolete date format allows a 2 digit year in the
1715 date field and allows for a list of alphabetic time zone
1716 specifications that were used in earlier versions of this standard.
1717 It also permits comments and folding white space between many of the
1718 tokens.
1719
1720 obs-day-of-week = [CFWS] day-name [CFWS]
1721
1722 obs-year = [CFWS] 2*DIGIT [CFWS]
1723
1724 obs-month = CFWS month-name CFWS
1725
1726 obs-day = [CFWS] 1*2DIGIT [CFWS]
1727
1728 obs-hour = [CFWS] 2DIGIT [CFWS]
1729
1730 obs-minute = [CFWS] 2DIGIT [CFWS]
1731
1732 obs-second = [CFWS] 2DIGIT [CFWS]
1733
1734 obs-zone = "UT" / "GMT" / ; Universal Time
1735
1736
1737
1738 Resnick Standards Track [Page 31]
1739
1740 RFC 2822 Internet Message Format April 2001
1741
1742
1743 ; North American UT
1744 ; offsets
1745 "EST" / "EDT" / ; Eastern: - 5/ - 4
1746 "CST" / "CDT" / ; Central: - 6/ - 5
1747 "MST" / "MDT" / ; Mountain: - 7/ - 6
1748 "PST" / "PDT" / ; Pacific: - 8/ - 7
1749
1750 %d65-73 / ; Military zones - "A"
1751 %d75-90 / ; through "I" and "K"
1752 %d97-105 / ; through "Z", both
1753 %d107-122 ; upper and lower case
1754
1755 Where a two or three digit year occurs in a date, the year is to be
1756 interpreted as follows: If a two digit year is encountered whose
1757 value is between 00 and 49, the year is interpreted by adding 2000,
1758 ending up with a value between 2000 and 2049. If a two digit year is
1759 encountered with a value between 50 and 99, or any three digit year
1760 is encountered, the year is interpreted by adding 1900.
1761
1762 In the obsolete time zone, "UT" and "GMT" are indications of
1763 "Universal Time" and "Greenwich Mean Time" respectively and are both
1764 semantically identical to "+0000".
1765
1766 The remaining three character zones are the US time zones. The first
1767 letter, "E", "C", "M", or "P" stands for "Eastern", "Central",
1768 "Mountain" and "Pacific". The second letter is either "S" for
1769 "Standard" time, or "D" for "Daylight" (or summer) time. Their
1770 interpretations are as follows:
1771
1772 EDT is semantically equivalent to -0400
1773 EST is semantically equivalent to -0500
1774 CDT is semantically equivalent to -0500
1775 CST is semantically equivalent to -0600
1776 MDT is semantically equivalent to -0600
1777 MST is semantically equivalent to -0700
1778 PDT is semantically equivalent to -0700
1779 PST is semantically equivalent to -0800
1780
1781 The 1 character military time zones were defined in a non-standard
1782 way in [RFC822] and are therefore unpredictable in their meaning.
1783 The original definitions of the military zones "A" through "I" are
1784 equivalent to "+0100" through "+0900" respectively; "K", "L", and "M"
1785 are equivalent to "+1000", "+1100", and "+1200" respectively; "N"
1786 through "Y" are equivalent to "-0100" through "-1200" respectively;
1787 and "Z" is equivalent to "+0000". However, because of the error in
1788 [RFC822], they SHOULD all be considered equivalent to "-0000" unless
1789 there is out-of-band information confirming their meaning.
1790
1791
1792
1793
1794 Resnick Standards Track [Page 32]
1795
1796 RFC 2822 Internet Message Format April 2001
1797
1798
1799 Other multi-character (usually between 3 and 5) alphabetic time zones
1800 have been used in Internet messages. Any such time zone whose
1801 meaning is not known SHOULD be considered equivalent to "-0000"
1802 unless there is out-of-band information confirming their meaning.
1803
1804 4.4. Obsolete Addressing
1805
1806 There are three primary differences in addressing. First, mailbox
1807 addresses were allowed to have a route portion before the addr-spec
1808 when enclosed in "<" and ">". The route is simply a comma-separated
1809 list of domain names, each preceded by "@", and the list terminated
1810 by a colon. Second, CFWS were allowed between the period-separated
1811 elements of local-part and domain (i.e., dot-atom was not used). In
1812 addition, local-part is allowed to contain quoted-string in addition
1813 to just atom. Finally, mailbox-list and address-list were allowed to
1814 have "null" members. That is, there could be two or more commas in
1815 such a list with nothing in between them.
1816
1817 obs-angle-addr = [CFWS] "<" [obs-route] addr-spec ">" [CFWS]
1818
1819 obs-route = [CFWS] obs-domain-list ":" [CFWS]
1820
1821 obs-domain-list = "@" domain *(*(CFWS / "," ) [CFWS] "@" domain)
1822
1823 obs-local-part = word *("." word)
1824
1825 obs-domain = atom *("." atom)
1826
1827 obs-mbox-list = 1*([mailbox] [CFWS] "," [CFWS]) [mailbox]
1828
1829 obs-addr-list = 1*([address] [CFWS] "," [CFWS]) [address]
1830
1831 When interpreting addresses, the route portion SHOULD be ignored.
1832
1833 4.5. Obsolete header fields
1834
1835 Syntactically, the primary difference in the obsolete field syntax is
1836 that it allows multiple occurrences of any of the fields and they may
1837 occur in any order. Also, any amount of white space is allowed
1838 before the ":" at the end of the field name.
1839
1840 obs-fields = *(obs-return /
1841 obs-received /
1842 obs-orig-date /
1843 obs-from /
1844 obs-sender /
1845 obs-reply-to /
1846 obs-to /
1847
1848
1849
1850 Resnick Standards Track [Page 33]
1851
1852 RFC 2822 Internet Message Format April 2001
1853
1854
1855 obs-cc /
1856 obs-bcc /
1857 obs-message-id /
1858 obs-in-reply-to /
1859 obs-references /
1860 obs-subject /
1861 obs-comments /
1862 obs-keywords /
1863 obs-resent-date /
1864 obs-resent-from /
1865 obs-resent-send /
1866 obs-resent-rply /
1867 obs-resent-to /
1868 obs-resent-cc /
1869 obs-resent-bcc /
1870 obs-resent-mid /
1871 obs-optional)
1872
1873 Except for destination address fields (described in section 4.5.3),
1874 the interpretation of multiple occurrences of fields is unspecified.
1875 Also, the interpretation of trace fields and resent fields which do
1876 not occur in blocks prepended to the message is unspecified as well.
1877 Unless otherwise noted in the following sections, interpretation of
1878 other fields is identical to the interpretation of their non-obsolete
1879 counterparts in section 3.
1880
1881 4.5.1. Obsolete origination date field
1882
1883 obs-orig-date = "Date" *WSP ":" date-time CRLF
1884
1885 4.5.2. Obsolete originator fields
1886
1887 obs-from = "From" *WSP ":" mailbox-list CRLF
1888
1889 obs-sender = "Sender" *WSP ":" mailbox CRLF
1890
1891 obs-reply-to = "Reply-To" *WSP ":" mailbox-list CRLF
1892
1893 4.5.3. Obsolete destination address fields
1894
1895 obs-to = "To" *WSP ":" address-list CRLF
1896
1897 obs-cc = "Cc" *WSP ":" address-list CRLF
1898
1899 obs-bcc = "Bcc" *WSP ":" (address-list / [CFWS]) CRLF
1900
1901
1902
1903
1904
1905
1906 Resnick Standards Track [Page 34]
1907
1908 RFC 2822 Internet Message Format April 2001
1909
1910
1911 When multiple occurrences of destination address fields occur in a
1912 message, they SHOULD be treated as if the address-list in the first
1913 occurrence of the field is combined with the address lists of the
1914 subsequent occurrences by adding a comma and concatenating.
1915
1916 4.5.4. Obsolete identification fields
1917
1918 The obsolete "In-Reply-To:" and "References:" fields differ from the
1919 current syntax in that they allow phrase (words or quoted strings) to
1920 appear. The obsolete forms of the left and right sides of msg-id
1921 allow interspersed CFWS, making them syntactically identical to
1922 local-part and domain respectively.
1923
1924 obs-message-id = "Message-ID" *WSP ":" msg-id CRLF
1925
1926 obs-in-reply-to = "In-Reply-To" *WSP ":" *(phrase / msg-id) CRLF
1927
1928 obs-references = "References" *WSP ":" *(phrase / msg-id) CRLF
1929
1930 obs-id-left = local-part
1931
1932 obs-id-right = domain
1933
1934 For purposes of interpretation, the phrases in the "In-Reply-To:" and
1935 "References:" fields are ignored.
1936
1937 Semantically, none of the optional CFWS surrounding the local-part
1938 and the domain are part of the obs-id-left and obs-id-right
1939 respectively.
1940
1941 4.5.5. Obsolete informational fields
1942
1943 obs-subject = "Subject" *WSP ":" unstructured CRLF
1944
1945 obs-comments = "Comments" *WSP ":" unstructured CRLF
1946
1947 obs-keywords = "Keywords" *WSP ":" obs-phrase-list CRLF
1948
1949 4.5.6. Obsolete resent fields
1950
1951 The obsolete syntax adds a "Resent-Reply-To:" field, which consists
1952 of the field name, the optional comments and folding white space, the
1953 colon, and a comma separated list of addresses.
1954
1955 obs-resent-from = "Resent-From" *WSP ":" mailbox-list CRLF
1956
1957 obs-resent-send = "Resent-Sender" *WSP ":" mailbox CRLF
1958
1959
1960
1961
1962 Resnick Standards Track [Page 35]
1963
1964 RFC 2822 Internet Message Format April 2001
1965
1966
1967 obs-resent-date = "Resent-Date" *WSP ":" date-time CRLF
1968
1969 obs-resent-to = "Resent-To" *WSP ":" address-list CRLF
1970
1971 obs-resent-cc = "Resent-Cc" *WSP ":" address-list CRLF
1972
1973 obs-resent-bcc = "Resent-Bcc" *WSP ":"
1974 (address-list / [CFWS]) CRLF
1975
1976 obs-resent-mid = "Resent-Message-ID" *WSP ":" msg-id CRLF
1977
1978 obs-resent-rply = "Resent-Reply-To" *WSP ":" address-list CRLF
1979
1980 As with other resent fields, the "Resent-Reply-To:" field is to be
1981 treated as trace information only.
1982
1983 4.5.7. Obsolete trace fields
1984
1985 The obs-return and obs-received are again given here as template
1986 definitions, just as return and received are in section 3. Their
1987 full syntax is given in [RFC2821].
1988
1989 obs-return = "Return-Path" *WSP ":" path CRLF
1990
1991 obs-received = "Received" *WSP ":" name-val-list CRLF
1992
1993 obs-path = obs-angle-addr
1994
1995 4.5.8. Obsolete optional fields
1996
1997 obs-optional = field-name *WSP ":" unstructured CRLF
1998
1999 5. Security Considerations
2000
2001 Care needs to be taken when displaying messages on a terminal or
2002 terminal emulator. Powerful terminals may act on escape sequences
2003 and other combinations of ASCII control characters with a variety of
2004 consequences. They can remap the keyboard or permit other
2005 modifications to the terminal which could lead to denial of service
2006 or even damaged data. They can trigger (sometimes programmable)
2007 answerback messages which can allow a message to cause commands to be
2008 issued on the recipient's behalf. They can also effect the operation
2009 of terminal attached devices such as printers. Message viewers may
2010 wish to strip potentially dangerous terminal escape sequences from
2011 the message prior to display. However, other escape sequences appear
2012 in messages for useful purposes (cf. [RFC2045, RFC2046, RFC2047,
2013 RFC2048, RFC2049, ISO2022]) and therefore should not be stripped
2014 indiscriminately.
2015
2016
2017
2018 Resnick Standards Track [Page 36]
2019
2020 RFC 2822 Internet Message Format April 2001
2021
2022
2023 Transmission of non-text objects in messages raises additional
2024 security issues. These issues are discussed in [RFC2045, RFC2046,
2025 RFC2047, RFC2048, RFC2049].
2026
2027 Many implementations use the "Bcc:" (blind carbon copy) field
2028 described in section 3.6.3 to facilitate sending messages to
2029 recipients without revealing the addresses of one or more of the
2030 addressees to the other recipients. Mishandling this use of "Bcc:"
2031 has implications for confidential information that might be revealed,
2032 which could eventually lead to security problems through knowledge of
2033 even the existence of a particular mail address. For example, if
2034 using the first method described in section 3.6.3, where the "Bcc:"
2035 line is removed from the message, blind recipients have no explicit
2036 indication that they have been sent a blind copy, except insofar as
2037 their address does not appear in the message header. Because of
2038 this, one of the blind addressees could potentially send a reply to
2039 all of the shown recipients and accidentally reveal that the message
2040 went to the blind recipient. When the second method from section
2041 3.6.3 is used, the blind recipient's address appears in the "Bcc:"
2042 field of a separate copy of the message. If the "Bcc:" field sent
2043 contains all of the blind addressees, all of the "Bcc:" recipients
2044 will be seen by each "Bcc:" recipient. Even if a separate message is
2045 sent to each "Bcc:" recipient with only the individual's address,
2046 implementations still need to be careful to process replies to the
2047 message as per section 3.6.3 so as not to accidentally reveal the
2048 blind recipient to other recipients.
2049
2050 6. Bibliography
2051
2052 [ASCII] American National Standards Institute (ANSI), Coded
2053 Character Set - 7-Bit American National Standard Code for
2054 Information Interchange, ANSI X3.4, 1986.
2055
2056 [ISO2022] International Organization for Standardization (ISO),
2057 Information processing - ISO 7-bit and 8-bit coded
2058 character sets - Code extension techniques, Third edition
2059 - 1986-05-01, ISO 2022, 1986.
2060
2061 [RFC822] Crocker, D., "Standard for the Format of ARPA Internet
2062 Text Messages", RFC 822, August 1982.
2063
2064 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2065 Extensions (MIME) Part One: Format of Internet Message
2066 Bodies", RFC 2045, November 1996.
2067
2068 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2069 Extensions (MIME) Part Two: Media Types", RFC 2046,
2070 November 1996.
2071
2072
2073
2074 Resnick Standards Track [Page 37]
2075
2076 RFC 2822 Internet Message Format April 2001
2077
2078
2079 [RFC2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
2080 Part Three: Message Header Extensions for Non-ASCII Text",
2081 RFC 2047, November 1996.
2082
2083 [RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
2084 Internet Mail Extensions (MIME) Part Four: Format of
2085 Internet Message Bodies", RFC 2048, November 1996.
2086
2087 [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2088 Extensions (MIME) Part Five: Conformance Criteria and
2089 Examples", RFC 2049, November 1996.
2090
2091 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2092 Requirement Levels", BCP 14, RFC 2119, March 1997.
2093
2094 [RFC2234] Crocker, D., Editor, and P. Overell, "Augmented BNF for
2095 Syntax Specifications: ABNF", RFC 2234, November 1997.
2096
2097 [RFC2821] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
2098 2821, March 2001.
2099
2100 [STD3] Braden, R., "Host Requirements", STD 3, RFC 1122 and RFC
2101 1123, October 1989.
2102
2103 [STD12] Mills, D., "Network Time Protocol", STD 12, RFC 1119,
2104 September 1989.
2105
2106 [STD13] Mockapetris, P., "Domain Name System", STD 13, RFC 1034
2107 and RFC 1035, November 1987.
2108
2109 [STD14] Partridge, C., "Mail Routing and the Domain System", STD
2110 14, RFC 974, January 1986.
2111
2112 7. Editor's Address
2113
2114 Peter W. Resnick
2115 QUALCOMM Incorporated
2116 5775 Morehouse Drive
2117 San Diego, CA 92121-1714
2118 USA
2119
2120 Phone: +1 858 651 4478
2121 Fax: +1 858 651 1102
2122 EMail: presnick@qualcomm.com
2123
2124
2125
2126
2127
2128
2129
2130 Resnick Standards Track [Page 38]
2131
2132 RFC 2822 Internet Message Format April 2001
2133
2134
2135 8. Acknowledgements
2136
2137 Many people contributed to this document. They included folks who
2138 participated in the Detailed Revision and Update of Messaging
2139 Standards (DRUMS) Working Group of the Internet Engineering Task
2140 Force (IETF), the chair of DRUMS, the Area Directors of the IETF, and
2141 people who simply sent their comments in via e-mail. The editor is
2142 deeply indebted to them all and thanks them sincerely. The below
2143 list includes everyone who sent e-mail concerning this document.
2144 Hopefully, everyone who contributed is named here:
2145
2146 Matti Aarnio Barry Finkel Larry Masinter
2147 Tanaka Akira Erik Forsberg Denis McKeon
2148 Russ Allbery Chuck Foster William P McQuillan
2149 Eric Allman Paul Fox Alexey Melnikov
2150 Harald Tveit Alvestrand Klaus M. Frank Perry E. Metzger
2151 Ran Atkinson Ned Freed Steven Miller
2152 Jos Backus Jochen Friedrich Keith Moore
2153 Bruce Balden Randall C. Gellens John Gardiner Myers
2154 Dave Barr Sukvinder Singh Gill Chris Newman
2155 Alan Barrett Tim Goodwin John W. Noerenberg
2156 John Beck Philip Guenther Eric Norman
2157 J. Robert von Behren Tony Hansen Mike O'Dell
2158 Jos den Bekker John Hawkinson Larry Osterman
2159 D. J. Bernstein Philip Hazel Paul Overell
2160 James Berriman Kai Henningsen Jacob Palme
2161 Norbert Bollow Robert Herriot Michael A. Patton
2162 Raj Bose Paul Hethmon Uzi Paz
2163 Antony Bowesman Jim Hill Michael A. Quinlan
2164 Scott Bradner Paul E. Hoffman Eric S. Raymond
2165 Randy Bush Steve Hole Sam Roberts
2166 Tom Byrer Kari Hurtta Hugh Sasse
2167 Bruce Campbell Marco S. Hyman Bart Schaefer
2168 Larry Campbell Ofer Inbar Tom Scola
2169 W. J. Carpenter Olle Jarnefors Wolfgang Segmuller
2170 Michael Chapman Kevin Johnson Nick Shelness
2171 Richard Clayton Sudish Joseph John Stanley
2172 Maurizio Codogno Maynard Kang Einar Stefferud
2173 Jim Conklin Prabhat Keni Jeff Stephenson
2174 R. Kelley Cook John C. Klensin Bernard Stern
2175 Steve Coya Graham Klyne Peter Sylvester
2176 Mark Crispin Brad Knowles Mark Symons
2177 Dave Crocker Shuhei Kobayashi Eric Thomas
2178 Matt Curtin Peter Koch Lee Thompson
2179 Michael D'Errico Dan Kohn Karel De Vriendt
2180 Cyrus Daboo Christian Kuhtz Matthew Wall
2181 Jutta Degener Anand Kumria Rolf Weber
2182 Mark Delany Steen Larsen Brent B. Welch
2183
2184
2185
2186 Resnick Standards Track [Page 39]
2187
2188 RFC 2822 Internet Message Format April 2001
2189
2190
2191 Steve Dorner Eliot Lear Dan Wing
2192 Harold A. Driscoll Barry Leiba Jack De Winter
2193 Michael Elkins Jay Levitt Gregory J. Woodhouse
2194 Robert Elz Lars-Johan Liman Greg A. Woods
2195 Johnny Eriksson Charles Lindsey Kazu Yamamoto
2196 Erik E. Fair Pete Loshin Alain Zahm
2197 Roger Fajman Simon Lyall Jamie Zawinski
2198 Patrik Faltstrom Bill Manning Timothy S. Zurcher
2199 Claus Andre Farber John Martin
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242 Resnick Standards Track [Page 40]
2243
2244 RFC 2822 Internet Message Format April 2001
2245
2246
2247 Appendix A. Example messages
2248
2249 This section presents a selection of messages. These are intended to
2250 assist in the implementation of this standard, but should not be
2251 taken as normative; that is to say, although the examples in this
2252 section were carefully reviewed, if there happens to be a conflict
2253 between these examples and the syntax described in sections 3 and 4
2254 of this document, the syntax in those sections is to be taken as
2255 correct.
2256
2257 Messages are delimited in this section between lines of "----". The
2258 "----" lines are not part of the message itself.
2259
2260 A.1. Addressing examples
2261
2262 The following are examples of messages that might be sent between two
2263 individuals.
2264
2265 A.1.1. A message from one person to another with simple addressing
2266
2267 This could be called a canonical message. It has a single author,
2268 John Doe, a single recipient, Mary Smith, a subject, the date, a
2269 message identifier, and a textual message in the body.
2270
2271 ----
2272 From: John Doe <jdoe@machine.example>
2273 To: Mary Smith <mary@example.net>
2274 Subject: Saying Hello
2275 Date: Fri, 21 Nov 1997 09:55:06 -0600
2276 Message-ID: <1234@local.machine.example>
2277
2278 This is a message just to say hello.
2279 So, "Hello".
2280 ----
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298 Resnick Standards Track [Page 41]
2299
2300 RFC 2822 Internet Message Format April 2001
2301
2302
2303 If John's secretary Michael actually sent the message, though John
2304 was the author and replies to this message should go back to him, the
2305 sender field would be used:
2306
2307 ----
2308 From: John Doe <jdoe@machine.example>
2309 Sender: Michael Jones <mjones@machine.example>
2310 To: Mary Smith <mary@example.net>
2311 Subject: Saying Hello
2312 Date: Fri, 21 Nov 1997 09:55:06 -0600
2313 Message-ID: <1234@local.machine.example>
2314
2315 This is a message just to say hello.
2316 So, "Hello".
2317 ----
2318
2319 A.1.2. Different types of mailboxes
2320
2321 This message includes multiple addresses in the destination fields
2322 and also uses several different forms of addresses.
2323
2324 ----
2325 From: "Joe Q. Public" <john.q.public@example.com>
2326 To: Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>
2327 Cc: <boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>
2328 Date: Tue, 1 Jul 2003 10:52:37 +0200
2329 Message-ID: <5678.21-Nov-1997@example.com>
2330
2331 Hi everyone.
2332 ----
2333
2334 Note that the display names for Joe Q. Public and Giant; "Big" Box
2335 needed to be enclosed in double-quotes because the former contains
2336 the period and the latter contains both semicolon and double-quote
2337 characters (the double-quote characters appearing as quoted-pair
2338 construct). Conversely, the display name for Who? could appear
2339 without them because the question mark is legal in an atom. Notice
2340 also that jdoe@example.org and boss@nil.test have no display names
2341 associated with them at all, and jdoe@example.org uses the simpler
2342 address form without the angle brackets.
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354 Resnick Standards Track [Page 42]
2355
2356 RFC 2822 Internet Message Format April 2001
2357
2358
2359 A.1.3. Group addresses
2360
2361 ----
2362 From: Pete <pete@silly.example>
2363 To: A Group:Chris Jones <c@a.test>,joe@where.test,John <jdoe@one.test>;
2364 Cc: Undisclosed recipients:;
2365 Date: Thu, 13 Feb 1969 23:32:54 -0330
2366 Message-ID: <testabcd.1234@silly.example>
2367
2368 Testing.
2369 ----
2370
2371 In this message, the "To:" field has a single group recipient named A
2372 Group which contains 3 addresses, and a "Cc:" field with an empty
2373 group recipient named Undisclosed recipients.
2374
2375 A.2. Reply messages
2376
2377 The following is a series of three messages that make up a
2378 conversation thread between John and Mary. John firsts sends a
2379 message to Mary, Mary then replies to John's message, and then John
2380 replies to Mary's reply message.
2381
2382 Note especially the "Message-ID:", "References:", and "In-Reply-To:"
2383 fields in each message.
2384
2385 ----
2386 From: John Doe <jdoe@machine.example>
2387 To: Mary Smith <mary@example.net>
2388 Subject: Saying Hello
2389 Date: Fri, 21 Nov 1997 09:55:06 -0600
2390 Message-ID: <1234@local.machine.example>
2391
2392 This is a message just to say hello.
2393 So, "Hello".
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 2822 Internet Message Format April 2001
2413
2414
2415 When sending replies, the Subject field is often retained, though
2416 prepended with "Re: " as described in section 3.6.5.
2417
2418 ----
2419 From: Mary Smith <mary@example.net>
2420 To: John Doe <jdoe@machine.example>
2421 Reply-To: "Mary Smith: Personal Account" <smith@home.example>
2422 Subject: Re: Saying Hello
2423 Date: Fri, 21 Nov 1997 10:01:10 -0600
2424 Message-ID: <3456@example.net>
2425 In-Reply-To: <1234@local.machine.example>
2426 References: <1234@local.machine.example>
2427
2428 This is a reply to your hello.
2429 ----
2430
2431 Note the "Reply-To:" field in the above message. When John replies
2432 to Mary's message above, the reply should go to the address in the
2433 "Reply-To:" field instead of the address in the "From:" field.
2434
2435 ----
2436 To: "Mary Smith: Personal Account" <smith@home.example>
2437 From: John Doe <jdoe@machine.example>
2438 Subject: Re: Saying Hello
2439 Date: Fri, 21 Nov 1997 11:00:00 -0600
2440 Message-ID: <abcd.1234@local.machine.tld>
2441 In-Reply-To: <3456@example.net>
2442 References: <1234@local.machine.example> <3456@example.net>
2443
2444 This is a reply to your reply.
2445 ----
2446
2447 A.3. Resent messages
2448
2449 Start with the message that has been used as an example several
2450 times:
2451
2452 ----
2453 From: John Doe <jdoe@machine.example>
2454 To: Mary Smith <mary@example.net>
2455 Subject: Saying Hello
2456 Date: Fri, 21 Nov 1997 09:55:06 -0600
2457 Message-ID: <1234@local.machine.example>
2458
2459 This is a message just to say hello.
2460 So, "Hello".
2461 ----
2462
2463
2464
2465
2466 Resnick Standards Track [Page 44]
2467
2468 RFC 2822 Internet Message Format April 2001
2469
2470
2471 Say that Mary, upon receiving this message, wishes to send a copy of
2472 the message to Jane such that (a) the message would appear to have
2473 come straight from John; (b) if Jane replies to the message, the
2474 reply should go back to John; and (c) all of the original
2475 information, like the date the message was originally sent to Mary,
2476 the message identifier, and the original addressee, is preserved. In
2477 this case, resent fields are prepended to the message:
2478
2479 ----
2480 Resent-From: Mary Smith <mary@example.net>
2481 Resent-To: Jane Brown <j-brown@other.example>
2482 Resent-Date: Mon, 24 Nov 1997 14:22:01 -0800
2483 Resent-Message-ID: <78910@example.net>
2484 From: John Doe <jdoe@machine.example>
2485 To: Mary Smith <mary@example.net>
2486 Subject: Saying Hello
2487 Date: Fri, 21 Nov 1997 09:55:06 -0600
2488 Message-ID: <1234@local.machine.example>
2489
2490 This is a message just to say hello.
2491 So, "Hello".
2492 ----
2493
2494 If Jane, in turn, wished to resend this message to another person,
2495 she would prepend her own set of resent header fields to the above
2496 and send that.
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522 Resnick Standards Track [Page 45]
2523
2524 RFC 2822 Internet Message Format April 2001
2525
2526
2527 A.4. Messages with trace fields
2528
2529 As messages are sent through the transport system as described in
2530 [RFC2821], trace fields are prepended to the message. The following
2531 is an example of what those trace fields might look like. Note that
2532 there is some folding white space in the first one since these lines
2533 can be long.
2534
2535 ----
2536 Received: from x.y.test
2537 by example.net
2538 via TCP
2539 with ESMTP
2540 id ABC12345
2541 for <mary@example.net>; 21 Nov 1997 10:05:43 -0600
2542 Received: from machine.example by x.y.test; 21 Nov 1997 10:01:22 -0600
2543 From: John Doe <jdoe@machine.example>
2544 To: Mary Smith <mary@example.net>
2545 Subject: Saying Hello
2546 Date: Fri, 21 Nov 1997 09:55:06 -0600
2547 Message-ID: <1234@local.machine.example>
2548
2549 This is a message just to say hello.
2550 So, "Hello".
2551 ----
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578 Resnick Standards Track [Page 46]
2579
2580 RFC 2822 Internet Message Format April 2001
2581
2582
2583 A.5. White space, comments, and other oddities
2584
2585 White space, including folding white space, and comments can be
2586 inserted between many of the tokens of fields. Taking the example
2587 from A.1.3, white space and comments can be inserted into all of the
2588 fields.
2589
2590 ----
2591 From: Pete(A wonderful \) chap) <pete(his account)@silly.test(his host)>
2592 To:A Group(Some people)
2593 :Chris Jones <c@(Chris's host.)public.example>,
2594 joe@example.org,
2595 John <jdoe@one.test> (my dear friend); (the end of the group)
2596 Cc:(Empty list)(start)Undisclosed recipients :(nobody(that I know)) ;
2597 Date: Thu,
2598 13
2599 Feb
2600 1969
2601 23:32
2602 -0330 (Newfoundland Time)
2603 Message-ID: <testabcd.1234@silly.test>
2604
2605 Testing.
2606 ----
2607
2608 The above example is aesthetically displeasing, but perfectly legal.
2609 Note particularly (1) the comments in the "From:" field (including
2610 one that has a ")" character appearing as part of a quoted-pair); (2)
2611 the white space absent after the ":" in the "To:" field as well as
2612 the comment and folding white space after the group name, the special
2613 character (".") in the comment in Chris Jones's address, and the
2614 folding white space before and after "joe@example.org,"; (3) the
2615 multiple and nested comments in the "Cc:" field as well as the
2616 comment immediately following the ":" after "Cc"; (4) the folding
2617 white space (but no comments except at the end) and the missing
2618 seconds in the time of the date field; and (5) the white space before
2619 (but not within) the identifier in the "Message-ID:" field.
2620
2621 A.6. Obsoleted forms
2622
2623 The following are examples of obsolete (that is, the "MUST NOT
2624 generate") syntactic elements described in section 4 of this
2625 document.
2626
2627
2628
2629
2630
2631
2632
2633
2634 Resnick Standards Track [Page 47]
2635
2636 RFC 2822 Internet Message Format April 2001
2637
2638
2639 A.6.1. Obsolete addressing
2640
2641 Note in the below example the lack of quotes around Joe Q. Public,
2642 the route that appears in the address for Mary Smith, the two commas
2643 that appear in the "To:" field, and the spaces that appear around the
2644 "." in the jdoe address.
2645
2646 ----
2647 From: Joe Q. Public <john.q.public@example.com>
2648 To: Mary Smith <@machine.tld:mary@example.net>, , jdoe@test . example
2649 Date: Tue, 1 Jul 2003 10:52:37 +0200
2650 Message-ID: <5678.21-Nov-1997@example.com>
2651
2652 Hi everyone.
2653 ----
2654
2655 A.6.2. Obsolete dates
2656
2657 The following message uses an obsolete date format, including a non-
2658 numeric time zone and a two digit year. Note that although the
2659 day-of-week is missing, that is not specific to the obsolete syntax;
2660 it is optional in the current syntax as well.
2661
2662 ----
2663 From: John Doe <jdoe@machine.example>
2664 To: Mary Smith <mary@example.net>
2665 Subject: Saying Hello
2666 Date: 21 Nov 97 09:55:06 GMT
2667 Message-ID: <1234@local.machine.example>
2668
2669 This is a message just to say hello.
2670 So, "Hello".
2671 ----
2672
2673 A.6.3. Obsolete white space and comments
2674
2675 White space and comments can appear between many more elements than
2676 in the current syntax. Also, folding lines that are made up entirely
2677 of white space are legal.
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690 Resnick Standards Track [Page 48]
2691
2692 RFC 2822 Internet Message Format April 2001
2693
2694
2695 ----
2696 From : John Doe <jdoe@machine(comment). example>
2697 To : Mary Smith
2698 __
2699 <mary@example.net>
2700 Subject : Saying Hello
2701 Date : Fri, 21 Nov 1997 09(comment): 55 : 06 -0600
2702 Message-ID : <1234 @ local(blah) .machine .example>
2703
2704 This is a message just to say hello.
2705 So, "Hello".
2706 ----
2707
2708 Note especially the second line of the "To:" field. It starts with
2709 two space characters. (Note that "__" represent blank spaces.)
2710 Therefore, it is considered part of the folding as described in
2711 section 4.2. Also, the comments and white space throughout
2712 addresses, dates, and message identifiers are all part of the
2713 obsolete syntax.
2714
2715 Appendix B. Differences from earlier standards
2716
2717 This appendix contains a list of changes that have been made in the
2718 Internet Message Format from earlier standards, specifically [RFC822]
2719 and [STD3]. Items marked with an asterisk (*) below are items which
2720 appear in section 4 of this document and therefore can no longer be
2721 generated.
2722
2723 1. Period allowed in obsolete form of phrase.
2724 2. ABNF moved out of document to [RFC2234].
2725 3. Four or more digits allowed for year.
2726 4. Header field ordering (and lack thereof) made explicit.
2727 5. Encrypted header field removed.
2728 6. Received syntax loosened to allow any token/value pair.
2729 7. Specifically allow and give meaning to "-0000" time zone.
2730 8. Folding white space is not allowed between every token.
2731 9. Requirement for destinations removed.
2732 10. Forwarding and resending redefined.
2733 11. Extension header fields no longer specifically called out.
2734 12. ASCII 0 (null) removed.*
2735 13. Folding continuation lines cannot contain only white space.*
2736 14. Free insertion of comments not allowed in date.*
2737 15. Non-numeric time zones not allowed.*
2738 16. Two digit years not allowed.*
2739 17. Three digit years interpreted, but not allowed for generation.
2740 18. Routes in addresses not allowed.*
2741 19. CFWS within local-parts and domains not allowed.*
2742 20. Empty members of address lists not allowed.*
2743
2744
2745
2746 Resnick Standards Track [Page 49]
2747
2748 RFC 2822 Internet Message Format April 2001
2749
2750
2751 21. Folding white space between field name and colon not allowed.*
2752 22. Comments between field name and colon not allowed.
2753 23. Tightened syntax of in-reply-to and references.*
2754 24. CFWS within msg-id not allowed.*
2755 25. Tightened semantics of resent fields as informational only.
2756 26. Resent-Reply-To not allowed.*
2757 27. No multiple occurrences of fields (except resent and received).*
2758 28. Free CR and LF not allowed.*
2759 29. Routes in return path not allowed.*
2760 30. Line length limits specified.
2761 31. Bcc more clearly specified.
2762
2763 Appendix C. Notices
2764
2765 Intellectual Property
2766
2767 The IETF takes no position regarding the validity or scope of any
2768 intellectual property or other rights that might be claimed to
2769 pertain to the implementation or use of the technology described in
2770 this document or the extent to which any license under such rights
2771 might or might not be available; neither does it represent that it
2772 has made any effort to identify any such rights. Information on the
2773 IETF's procedures with respect to rights in standards-track and
2774 standards-related documentation can be found in BCP-11. Copies of
2775 claims of rights made available for publication and any assurances of
2776 licenses to be made available, or the result of an attempt made to
2777 obtain a general license or permission for the use of such
2778 proprietary rights by implementors or users of this specification can
2779 be obtained from the IETF Secretariat.
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802 Resnick Standards Track [Page 50]
2803
2804 RFC 2822 Internet Message Format April 2001
2805
2806
2807 Full Copyright Statement
2808
2809 Copyright (C) The Internet Society (2001). All Rights Reserved.
2810
2811 This document and translations of it may be copied and furnished to
2812 others, and derivative works that comment on or otherwise explain it
2813 or assist in its implementation may be prepared, copied, published
2814 and distributed, in whole or in part, without restriction of any
2815 kind, provided that the above copyright notice and this paragraph are
2816 included on all such copies and derivative works. However, this
2817 document itself may not be modified in any way, such as by removing
2818 the copyright notice or references to the Internet Society or other
2819 Internet organizations, except as needed for the purpose of
2820 developing Internet standards in which case the procedures for
2821 copyrights defined in the Internet Standards process must be
2822 followed, or as required to translate it into languages other than
2823 English.
2824
2825 The limited permissions granted above are perpetual and will not be
2826 revoked by the Internet Society or its successors or assigns.
2827
2828 This document and the information contained herein is provided on an
2829 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
2830 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
2831 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
2832 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
2833 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
2834
2835 Acknowledgement
2836
2837 Funding for the RFC Editor function is currently provided by the
2838 Internet Society.
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
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