Commit | Line | Data |
---|---|---|
657793ae EA |
1 | |
2 | ||
3 | ||
4 | ||
5 | ||
6 | ||
7 | RFC # 822 | |
8 | ||
9 | Obsoletes: RFC #733 (NIC #41952) | |
10 | ||
11 | ||
12 | ||
13 | ||
14 | ||
15 | ||
16 | ||
17 | ||
18 | ||
19 | ||
20 | ||
21 | ||
22 | STANDARD FOR THE FORMAT OF | |
23 | ||
24 | ARPA INTERNET TEXT MESSAGES | |
25 | ||
26 | ||
27 | ||
28 | ||
29 | ||
30 | ||
31 | August 13, 1982 | |
32 | ||
33 | ||
34 | ||
35 | ||
36 | ||
37 | ||
38 | Revised by | |
39 | ||
40 | David H. Crocker | |
41 | ||
42 | ||
43 | Dept. of Electrical Engineering | |
44 | University of Delaware, Newark, DE 19711 | |
45 | Network: DCrocker @ UDel-Relay | |
46 | ||
47 | ||
48 | ||
49 | ||
50 | ||
51 | ||
52 | ||
53 | ||
54 | ||
55 | ||
56 | ||
57 | ||
58 | \f | |
59 | ||
60 | ||
61 | Standard for ARPA Internet Text Messages | |
62 | ||
63 | ||
64 | TABLE OF CONTENTS | |
65 | ||
66 | ||
67 | PREFACE .................................................... ii | |
68 | ||
69 | 1. INTRODUCTION ........................................... 1 | |
70 | ||
71 | 1.1. Scope ............................................ 1 | |
72 | 1.2. Communication Framework .......................... 2 | |
73 | ||
74 | 2. NOTATIONAL CONVENTIONS ................................. 3 | |
75 | ||
76 | 3. LEXICAL ANALYSIS OF MESSAGES ........................... 5 | |
77 | ||
78 | 3.1. General Description .............................. 5 | |
79 | 3.2. Header Field Definitions ......................... 9 | |
80 | 3.3. Lexical Tokens ................................... 10 | |
81 | 3.4. Clarifications ................................... 11 | |
82 | ||
83 | 4. MESSAGE SPECIFICATION .................................. 17 | |
84 | ||
85 | 4.1. Syntax ........................................... 17 | |
86 | 4.2. Forwarding ....................................... 19 | |
87 | 4.3. Trace Fields ..................................... 20 | |
88 | 4.4. Originator Fields ................................ 21 | |
89 | 4.5. Receiver Fields .................................. 23 | |
90 | 4.6. Reference Fields ................................. 23 | |
91 | 4.7. Other Fields ..................................... 24 | |
92 | ||
93 | 5. DATE AND TIME SPECIFICATION ............................ 26 | |
94 | ||
95 | 5.1. Syntax ........................................... 26 | |
96 | 5.2. Semantics ........................................ 26 | |
97 | ||
98 | 6. ADDRESS SPECIFICATION .................................. 27 | |
99 | ||
100 | 6.1. Syntax ........................................... 27 | |
101 | 6.2. Semantics ........................................ 27 | |
102 | 6.3. Reserved Address ................................. 33 | |
103 | ||
104 | 7. BIBLIOGRAPHY ........................................... 34 | |
105 | ||
106 | ||
107 | APPENDIX | |
108 | ||
109 | A. EXAMPLES ............................................... 36 | |
110 | B. SIMPLE FIELD PARSING ................................... 40 | |
111 | C. DIFFERENCES FROM RFC #733 .............................. 41 | |
112 | D. ALPHABETICAL LISTING OF SYNTAX RULES ................... 44 | |
113 | ||
114 | ||
115 | August 13, 1982 - i - RFC #822 | |
116 | \f | |
117 | ||
118 | ||
119 | ||
120 | Standard for ARPA Internet Text Messages | |
121 | ||
122 | ||
123 | PREFACE | |
124 | ||
125 | ||
126 | By 1977, the Arpanet employed several informal standards for | |
127 | the text messages (mail) sent among its host computers. It was | |
128 | felt necessary to codify these practices and provide for those | |
129 | features that seemed imminent. The result of that effort was | |
130 | Request for Comments (RFC) #733, "Standard for the Format of ARPA | |
131 | Network Text Message", by Crocker, Vittal, Pogran, and Henderson. | |
132 | The specification attempted to avoid major changes in existing | |
133 | software, while permitting several new features. | |
134 | ||
135 | This document revises the specifications in RFC #733, in | |
136 | order to serve the needs of the larger and more complex ARPA | |
137 | Internet. Some of RFC #733's features failed to gain adequate | |
138 | acceptance. In order to simplify the standard and the software | |
139 | that follows it, these features have been removed. A different | |
140 | addressing scheme is used, to handle the case of inter-network | |
141 | mail; and the concept of re-transmission has been introduced. | |
142 | ||
143 | This specification is intended for use in the ARPA Internet. | |
144 | However, an attempt has been made to free it of any dependence on | |
145 | that environment, so that it can be applied to other network text | |
146 | message systems. | |
147 | ||
148 | The specification of RFC #733 took place over the course of | |
149 | one year, using the ARPANET mail environment, itself, to provide | |
150 | an on-going forum for discussing the capabilities to be included. | |
151 | More than twenty individuals, from across the country, partici- | |
152 | pated in the original discussion. The development of this | |
153 | revised specification has, similarly, utilized network mail-based | |
154 | group discussion. Both specification efforts greatly benefited | |
155 | from the comments and ideas of the participants. | |
156 | ||
157 | The syntax of the standard, in RFC #733, was originally | |
158 | specified in the Backus-Naur Form (BNF) meta-language. Ken L. | |
159 | Harrenstien, of SRI International, was responsible for re-coding | |
160 | the BNF into an augmented BNF that makes the representation | |
161 | smaller and easier to understand. | |
162 | ||
163 | ||
164 | ||
165 | ||
166 | ||
167 | ||
168 | ||
169 | ||
170 | ||
171 | ||
172 | ||
173 | ||
174 | August 13, 1982 - ii - RFC #822 | |
175 | \f | |
176 | ||
177 | ||
178 | Standard for ARPA Internet Text Messages | |
179 | ||
180 | ||
181 | 1. INTRODUCTION | |
182 | ||
183 | 1.1. SCOPE | |
184 | ||
185 | This standard specifies a syntax for text messages that are | |
186 | sent among computer users, within the framework of "electronic | |
187 | mail". The standard supersedes the one specified in ARPANET | |
188 | Request for Comments #733, "Standard for the Format of ARPA Net- | |
189 | work Text Messages". | |
190 | ||
191 | In this context, messages are viewed as having an envelope | |
192 | and contents. The envelope contains whatever information is | |
193 | needed to accomplish transmission and delivery. The contents | |
194 | compose the object to be delivered to the recipient. This stan- | |
195 | dard applies only to the format and some of the semantics of mes- | |
196 | sage contents. It contains no specification of the information | |
197 | in the envelope. | |
198 | ||
199 | However, some message systems may use information from the | |
200 | contents to create the envelope. It is intended that this stan- | |
201 | dard facilitate the acquisition of such information by programs. | |
202 | ||
203 | Some message systems may store messages in formats that | |
204 | differ from the one specified in this standard. This specifica- | |
205 | tion is intended strictly as a definition of what message content | |
206 | format is to be passed BETWEEN hosts. | |
207 | ||
208 | Note: This standard is NOT intended to dictate the internal for- | |
209 | mats used by sites, the specific message system features | |
210 | that they are expected to support, or any of the charac- | |
211 | teristics of user interface programs that create or read | |
212 | messages. | |
213 | ||
214 | A distinction should be made between what the specification | |
215 | REQUIRES and what it ALLOWS. Messages can be made complex and | |
216 | rich with formally-structured components of information or can be | |
217 | kept small and simple, with a minimum of such information. Also, | |
218 | the standard simplifies the interpretation of differing visual | |
219 | formats in messages; only the visual aspect of a message is | |
220 | affected and not the interpretation of information within it. | |
221 | Implementors may choose to retain such visual distinctions. | |
222 | ||
223 | The formal definition is divided into four levels. The bot- | |
224 | tom level describes the meta-notation used in this document. The | |
225 | second level describes basic lexical analyzers that feed tokens | |
226 | to higher-level parsers. Next is an overall specification for | |
227 | messages; it permits distinguishing individual fields. Finally, | |
228 | there is definition of the contents of several structured fields. | |
229 | ||
230 | ||
231 | ||
232 | August 13, 1982 - 1 - RFC #822 | |
233 | \f | |
234 | ||
235 | ||
236 | Standard for ARPA Internet Text Messages | |
237 | ||
238 | ||
239 | 1.2. COMMUNICATION FRAMEWORK | |
240 | ||
241 | Messages consist of lines of text. No special provisions | |
242 | are made for encoding drawings, facsimile, speech, or structured | |
243 | text. No significant consideration has been given to questions | |
244 | of data compression or to transmission and storage efficiency, | |
245 | and the standard tends to be free with the number of bits con- | |
246 | sumed. For example, field names are specified as free text, | |
247 | rather than special terse codes. | |
248 | ||
249 | A general "memo" framework is used. That is, a message con- | |
250 | sists of some information in a rigid format, followed by the main | |
251 | part of the message, with a format that is not specified in this | |
252 | document. The syntax of several fields of the rigidly-formated | |
253 | ("headers") section is defined in this specification; some of | |
254 | these fields must be included in all messages. | |
255 | ||
256 | The syntax that distinguishes between header fields is | |
257 | specified separately from the internal syntax for particular | |
258 | fields. This separation is intended to allow simple parsers to | |
259 | operate on the general structure of messages, without concern for | |
260 | the detailed structure of individual header fields. Appendix B | |
261 | is provided to facilitate construction of these parsers. | |
262 | ||
263 | In addition to the fields specified in this document, it is | |
264 | expected that other fields will gain common use. As necessary, | |
265 | the specifications for these "extension-fields" will be published | |
266 | through the same mechanism used to publish this document. Users | |
267 | may also wish to extend the set of fields that they use | |
268 | privately. Such "user-defined fields" are permitted. | |
269 | ||
270 | The framework severely constrains document tone and appear- | |
271 | ance and is primarily useful for most intra-organization communi- | |
272 | cations and well-structured inter-organization communication. | |
273 | It also can be used for some types of inter-process communica- | |
274 | tion, such as simple file transfer and remote job entry. A more | |
275 | robust framework might allow for multi-font, multi-color, multi- | |
276 | dimension encoding of information. A less robust one, as is | |
277 | present in most single-machine message systems, would more | |
278 | severely constrain the ability to add fields and the decision to | |
279 | include specific fields. In contrast with paper-based communica- | |
280 | tion, it is interesting to note that the RECEIVER of a message | |
281 | can exercise an extraordinary amount of control over the | |
282 | message's appearance. The amount of actual control available to | |
283 | message receivers is contingent upon the capabilities of their | |
284 | individual message systems. | |
285 | ||
286 | ||
287 | ||
288 | ||
289 | ||
290 | August 13, 1982 - 2 - RFC #822 | |
291 | \f | |
292 | ||
293 | ||
294 | Standard for ARPA Internet Text Messages | |
295 | ||
296 | ||
297 | 2. NOTATIONAL CONVENTIONS | |
298 | ||
299 | This specification uses an augmented Backus-Naur Form (BNF) | |
300 | notation. The differences from standard BNF involve naming rules | |
301 | and indicating repetition and "local" alternatives. | |
302 | ||
303 | 2.1. RULE NAMING | |
304 | ||
305 | Angle brackets ("<", ">") are not used, in general. The | |
306 | name of a rule is simply the name itself, rather than "<name>". | |
307 | Quotation-marks enclose literal text (which may be upper and/or | |
308 | lower case). Certain basic rules are in uppercase, such as | |
309 | SPACE, TAB, CRLF, DIGIT, ALPHA, etc. Angle brackets are used in | |
310 | rule definitions, and in the rest of this document, whenever | |
311 | their presence will facilitate discerning the use of rule names. | |
312 | ||
313 | 2.2. RULE1 / RULE2: ALTERNATIVES | |
314 | ||
315 | Elements separated by slash ("/") are alternatives. There- | |
316 | fore "foo / bar" will accept foo or bar. | |
317 | ||
318 | 2.3. (RULE1 RULE2): LOCAL ALTERNATIVES | |
319 | ||
320 | Elements enclosed in parentheses are treated as a single | |
321 | element. Thus, "(elem (foo / bar) elem)" allows the token | |
322 | sequences "elem foo elem" and "elem bar elem". | |
323 | ||
324 | 2.4. *RULE: REPETITION | |
325 | ||
326 | The character "*" preceding an element indicates repetition. | |
327 | The full form is: | |
328 | ||
329 | <l>*<m>element | |
330 | ||
331 | indicating at least <l> and at most <m> occurrences of element. | |
332 | Default values are 0 and infinity so that "*(element)" allows any | |
333 | number, including zero; "1*element" requires at least one; and | |
334 | "1*2element" allows one or two. | |
335 | ||
336 | 2.5. [RULE]: OPTIONAL | |
337 | ||
338 | Square brackets enclose optional elements; "[foo bar]" is | |
339 | equivalent to "*1(foo bar)". | |
340 | ||
341 | 2.6. NRULE: SPECIFIC REPETITION | |
342 | ||
343 | "<n>(element)" is equivalent to "<n>*<n>(element)"; that is, | |
344 | exactly <n> occurrences of (element). Thus 2DIGIT is a 2-digit | |
345 | number, and 3ALPHA is a string of three alphabetic characters. | |
346 | ||
347 | ||
348 | August 13, 1982 - 3 - RFC #822 | |
349 | \f | |
350 | ||
351 | ||
352 | Standard for ARPA Internet Text Messages | |
353 | ||
354 | ||
355 | 2.7. #RULE: LISTS | |
356 | ||
357 | A construct "#" is defined, similar to "*", as follows: | |
358 | ||
359 | <l>#<m>element | |
360 | ||
361 | indicating at least <l> and at most <m> elements, each separated | |
362 | by one or more commas (","). This makes the usual form of lists | |
363 | very easy; a rule such as '(element *("," element))' can be shown | |
364 | as "1#element". Wherever this construct is used, null elements | |
365 | are allowed, but do not contribute to the count of elements | |
366 | present. That is, "(element),,(element)" is permitted, but | |
367 | counts as only two elements. Therefore, where at least one ele- | |
368 | ment is required, at least one non-null element must be present. | |
369 | Default values are 0 and infinity so that "#(element)" allows any | |
370 | number, including zero; "1#element" requires at least one; and | |
371 | "1#2element" allows one or two. | |
372 | ||
373 | 2.8. ; COMMENTS | |
374 | ||
375 | A semi-colon, set off some distance to the right of rule | |
376 | text, starts a comment that continues to the end of line. This | |
377 | is a simple way of including useful notes in parallel with the | |
378 | specifications. | |
379 | ||
380 | ||
381 | ||
382 | ||
383 | ||
384 | ||
385 | ||
386 | ||
387 | ||
388 | ||
389 | ||
390 | ||
391 | ||
392 | ||
393 | ||
394 | ||
395 | ||
396 | ||
397 | ||
398 | ||
399 | ||
400 | ||
401 | ||
402 | ||
403 | ||
404 | ||
405 | ||
406 | August 13, 1982 - 4 - RFC #822 | |
407 | \f | |
408 | ||
409 | ||
410 | Standard for ARPA Internet Text Messages | |
411 | ||
412 | ||
413 | 3. LEXICAL ANALYSIS OF MESSAGES | |
414 | ||
415 | 3.1. GENERAL DESCRIPTION | |
416 | ||
417 | A message consists of header fields and, optionally, a body. | |
418 | The body is simply a sequence of lines containing ASCII charac- | |
419 | ters. It is separated from the headers by a null line (i.e., a | |
420 | line with nothing preceding the CRLF). | |
421 | ||
422 | 3.1.1. LONG HEADER FIELDS | |
423 | ||
424 | Each header field can be viewed as a single, logical line of | |
425 | ASCII characters, comprising a field-name and a field-body. | |
426 | For convenience, the field-body portion of this conceptual | |
427 | entity can be split into a multiple-line representation; this | |
428 | is called "folding". The general rule is that wherever there | |
429 | may be linear-white-space (NOT simply LWSP-chars), a CRLF | |
430 | immediately followed by AT LEAST one LWSP-char may instead be | |
431 | inserted. Thus, the single line | |
432 | ||
433 | To: "Joe & J. Harvey" <ddd @Org>, JJV @ BBN | |
434 | ||
435 | can be represented as: | |
436 | ||
437 | To: "Joe & J. Harvey" <ddd @ Org>, | |
438 | JJV@BBN | |
439 | ||
440 | and | |
441 | ||
442 | To: "Joe & J. Harvey" | |
443 | <ddd@ Org>, JJV | |
444 | @BBN | |
445 | ||
446 | and | |
447 | ||
448 | To: "Joe & | |
449 | J. Harvey" <ddd @ Org>, JJV @ BBN | |
450 | ||
451 | The process of moving from this folded multiple-line | |
452 | representation of a header field to its single line represen- | |
453 | tation is called "unfolding". Unfolding is accomplished by | |
454 | regarding CRLF immediately followed by a LWSP-char as | |
455 | equivalent to the LWSP-char. | |
456 | ||
457 | Note: While the standard permits folding wherever linear- | |
458 | white-space is permitted, it is recommended that struc- | |
459 | tured fields, such as those containing addresses, limit | |
460 | folding to higher-level syntactic breaks. For address | |
461 | fields, it is recommended that such folding occur | |
462 | ||
463 | ||
464 | August 13, 1982 - 5 - RFC #822 | |
465 | \f | |
466 | ||
467 | ||
468 | Standard for ARPA Internet Text Messages | |
469 | ||
470 | ||
471 | between addresses, after the separating comma. | |
472 | ||
473 | 3.1.2. STRUCTURE OF HEADER FIELDS | |
474 | ||
475 | Once a field has been unfolded, it may be viewed as being com- | |
476 | posed of a field-name followed by a colon (":"), followed by a | |
477 | field-body, and terminated by a carriage-return/line-feed. | |
478 | The field-name must be composed of printable ASCII characters | |
479 | (i.e., characters that have values between 33. and 126., | |
480 | decimal, except colon). The field-body may be composed of any | |
481 | ASCII characters, except CR or LF. (While CR and/or LF may be | |
482 | present in the actual text, they are removed by the action of | |
483 | unfolding the field.) | |
484 | ||
485 | Certain field-bodies of headers may be interpreted according | |
486 | to an internal syntax that some systems may wish to parse. | |
487 | These fields are called "structured fields". Examples | |
488 | include fields containing dates and addresses. Other fields, | |
489 | such as "Subject" and "Comments", are regarded simply as | |
490 | strings of text. | |
491 | ||
492 | Note: Any field which has a field-body that is defined as | |
493 | other than simply <text> is to be treated as a struc- | |
494 | tured field. | |
495 | ||
496 | Field-names, unstructured field bodies and structured | |
497 | field bodies each are scanned by their own, independent | |
498 | "lexical" analyzers. | |
499 | ||
500 | 3.1.3. UNSTRUCTURED FIELD BODIES | |
501 | ||
502 | For some fields, such as "Subject" and "Comments", no struc- | |
503 | turing is assumed, and they are treated simply as <text>s, as | |
504 | in the message body. Rules of folding apply to these fields, | |
505 | so that such field bodies which occupy several lines must | |
506 | therefore have the second and successive lines indented by at | |
507 | least one LWSP-char. | |
508 | ||
509 | 3.1.4. STRUCTURED FIELD BODIES | |
510 | ||
511 | To aid in the creation and reading of structured fields, the | |
512 | free insertion of linear-white-space (which permits folding | |
513 | by inclusion of CRLFs) is allowed between lexical tokens. | |
514 | Rather than obscuring the syntax specifications for these | |
515 | structured fields with explicit syntax for this linear-white- | |
516 | space, the existence of another "lexical" analyzer is assumed. | |
517 | This analyzer does not apply for unstructured field bodies | |
518 | that are simply strings of text, as described above. The | |
519 | analyzer provides an interpretation of the unfolded text | |
520 | ||
521 | ||
522 | August 13, 1982 - 6 - RFC #822 | |
523 | \f | |
524 | ||
525 | ||
526 | Standard for ARPA Internet Text Messages | |
527 | ||
528 | ||
529 | composing the body of the field as a sequence of lexical sym- | |
530 | bols. | |
531 | ||
532 | These symbols are: | |
533 | ||
534 | - individual special characters | |
535 | - quoted-strings | |
536 | - domain-literals | |
537 | - comments | |
538 | - atoms | |
539 | ||
540 | The first four of these symbols are self-delimiting. Atoms | |
541 | are not; they are delimited by the self-delimiting symbols and | |
542 | by linear-white-space. For the purposes of regenerating | |
543 | sequences of atoms and quoted-strings, exactly one SPACE is | |
544 | assumed to exist, and should be used, between them. (Also, in | |
545 | the "Clarifications" section on "White Space", below, note the | |
546 | rules about treatment of multiple contiguous LWSP-chars.) | |
547 | ||
548 | So, for example, the folded body of an address field | |
549 | ||
550 | ":sysmail"@ Some-Group. Some-Org, | |
551 | Muhammed.(I am the greatest) Ali @(the)Vegas.WBA | |
552 | ||
553 | ||
554 | ||
555 | ||
556 | ||
557 | ||
558 | ||
559 | ||
560 | ||
561 | ||
562 | ||
563 | ||
564 | ||
565 | ||
566 | ||
567 | ||
568 | ||
569 | ||
570 | ||
571 | ||
572 | ||
573 | ||
574 | ||
575 | ||
576 | ||
577 | ||
578 | ||
579 | ||
580 | August 13, 1982 - 7 - RFC #822 | |
581 | \f | |
582 | ||
583 | ||
584 | Standard for ARPA Internet Text Messages | |
585 | ||
586 | ||
587 | is analyzed into the following lexical symbols and types: | |
588 | ||
589 | :sysmail quoted string | |
590 | @ special | |
591 | Some-Group atom | |
592 | . special | |
593 | Some-Org atom | |
594 | , special | |
595 | Muhammed atom | |
596 | . special | |
597 | (I am the greatest) comment | |
598 | Ali atom | |
599 | @ atom | |
600 | (the) comment | |
601 | Vegas atom | |
602 | . special | |
603 | WBA atom | |
604 | ||
605 | The canonical representations for the data in these addresses | |
606 | are the following strings: | |
607 | ||
608 | ":sysmail"@Some-Group.Some-Org | |
609 | ||
610 | and | |
611 | ||
612 | Muhammed.Ali@Vegas.WBA | |
613 | ||
614 | Note: For purposes of display, and when passing such struc- | |
615 | tured information to other systems, such as mail proto- | |
616 | col services, there must be NO linear-white-space | |
617 | between <word>s that are separated by period (".") or | |
618 | at-sign ("@") and exactly one SPACE between all other | |
619 | <word>s. Also, headers should be in a folded form. | |
620 | ||
621 | ||
622 | ||
623 | ||
624 | ||
625 | ||
626 | ||
627 | ||
628 | ||
629 | ||
630 | ||
631 | ||
632 | ||
633 | ||
634 | ||
635 | ||
636 | ||
637 | ||
638 | August 13, 1982 - 8 - RFC #822 | |
639 | \f | |
640 | ||
641 | ||
642 | Standard for ARPA Internet Text Messages | |
643 | ||
644 | ||
645 | 3.2. HEADER FIELD DEFINITIONS | |
646 | ||
647 | These rules show a field meta-syntax, without regard for the | |
648 | particular type or internal syntax. Their purpose is to permit | |
649 | detection of fields; also, they present to higher-level parsers | |
650 | an image of each field as fitting on one line. | |
651 | ||
652 | field = field-name ":" [ field-body ] CRLF | |
653 | ||
654 | field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":"> | |
655 | ||
656 | field-body = field-body-contents | |
657 | [CRLF LWSP-char field-body] | |
658 | ||
659 | field-body-contents = | |
660 | <the ASCII characters making up the field-body, as | |
661 | defined in the following sections, and consisting | |
662 | of combinations of atom, quoted-string, and | |
663 | specials tokens, or else consisting of texts> | |
664 | ||
665 | ||
666 | ||
667 | ||
668 | ||
669 | ||
670 | ||
671 | ||
672 | ||
673 | ||
674 | ||
675 | ||
676 | ||
677 | ||
678 | ||
679 | ||
680 | ||
681 | ||
682 | ||
683 | ||
684 | ||
685 | ||
686 | ||
687 | ||
688 | ||
689 | ||
690 | ||
691 | ||
692 | ||
693 | ||
694 | ||
695 | ||
696 | August 13, 1982 - 9 - RFC #822 | |
697 | \f | |
698 | ||
699 | ||
700 | Standard for ARPA Internet Text Messages | |
701 | ||
702 | ||
703 | 3.3. LEXICAL TOKENS | |
704 | ||
705 | The following rules are used to define an underlying lexical | |
706 | analyzer, which feeds tokens to higher level parsers. See the | |
707 | ANSI references, in the Bibliography. | |
708 | ||
709 | ; ( Octal, Decimal.) | |
710 | CHAR = <any ASCII character> ; ( 0-177, 0.-127.) | |
711 | ALPHA = <any ASCII alphabetic character> | |
712 | ; (101-132, 65.- 90.) | |
713 | ; (141-172, 97.-122.) | |
714 | DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.) | |
715 | CTL = <any ASCII control ; ( 0- 37, 0.- 31.) | |
716 | character and DEL> ; ( 177, 127.) | |
717 | CR = <ASCII CR, carriage return> ; ( 15, 13.) | |
718 | LF = <ASCII LF, linefeed> ; ( 12, 10.) | |
719 | SPACE = <ASCII SP, space> ; ( 40, 32.) | |
720 | HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.) | |
721 | <"> = <ASCII quote mark> ; ( 42, 34.) | |
722 | CRLF = CR LF | |
723 | ||
724 | LWSP-char = SPACE / HTAB ; semantics = SPACE | |
725 | ||
726 | linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE | |
727 | ; CRLF => folding | |
728 | ||
729 | specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted- | |
730 | / "," / ";" / ":" / "\" / <"> ; string, to use | |
731 | / "." / "[" / "]" ; within a word. | |
732 | ||
733 | delimiters = specials / linear-white-space / comment | |
734 | ||
735 | text = <any CHAR, including bare ; => atoms, specials, | |
736 | CR & bare LF, but NOT ; comments and | |
737 | including CRLF> ; quoted-strings are | |
738 | ; NOT recognized. | |
739 | ||
740 | atom = 1*<any CHAR except specials, SPACE and CTLs> | |
741 | ||
742 | quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or | |
743 | ; quoted chars. | |
744 | ||
745 | qtext = <any CHAR excepting <">, ; => may be folded | |
746 | "\" & CR, and including | |
747 | linear-white-space> | |
748 | ||
749 | domain-literal = "[" *(dtext / quoted-pair) "]" | |
750 | ||
751 | ||
752 | ||
753 | ||
754 | August 13, 1982 - 10 - RFC #822 | |
755 | \f | |
756 | ||
757 | ||
758 | Standard for ARPA Internet Text Messages | |
759 | ||
760 | ||
761 | dtext = <any CHAR excluding "[", ; => may be folded | |
762 | "]", "\" & CR, & including | |
763 | linear-white-space> | |
764 | ||
765 | comment = "(" *(ctext / quoted-pair / comment) ")" | |
766 | ||
767 | ctext = <any CHAR excluding "(", ; => may be folded | |
768 | ")", "\" & CR, & including | |
769 | linear-white-space> | |
770 | ||
771 | quoted-pair = "\" CHAR ; may quote any char | |
772 | ||
773 | phrase = 1*word ; Sequence of words | |
774 | ||
775 | word = atom / quoted-string | |
776 | ||
777 | ||
778 | 3.4. CLARIFICATIONS | |
779 | ||
780 | 3.4.1. QUOTING | |
781 | ||
782 | Some characters are reserved for special interpretation, such | |
783 | as delimiting lexical tokens. To permit use of these charac- | |
784 | ters as uninterpreted data, a quoting mechanism is provided. | |
785 | To quote a character, precede it with a backslash ("\"). | |
786 | ||
787 | This mechanism is not fully general. Characters may be quoted | |
788 | only within a subset of the lexical constructs. In particu- | |
789 | lar, quoting is limited to use within: | |
790 | ||
791 | - quoted-string | |
792 | - domain-literal | |
793 | - comment | |
794 | ||
795 | Within these constructs, quoting is REQUIRED for CR and "\" | |
796 | and for the character(s) that delimit the token (e.g., "(" and | |
797 | ")" for a comment). However, quoting is PERMITTED for any | |
798 | character. | |
799 | ||
800 | Note: In particular, quoting is NOT permitted within atoms. | |
801 | For example when the local-part of an addr-spec must | |
802 | contain a special character, a quoted string must be | |
803 | used. Therefore, a specification such as: | |
804 | ||
805 | Full\ Name@Domain | |
806 | ||
807 | is not legal and must be specified as: | |
808 | ||
809 | "Full Name"@Domain | |
810 | ||
811 | ||
812 | August 13, 1982 - 11 - RFC #822 | |
813 | \f | |
814 | ||
815 | ||
816 | Standard for ARPA Internet Text Messages | |
817 | ||
818 | ||
819 | 3.4.2. WHITE SPACE | |
820 | ||
821 | Note: In structured field bodies, multiple linear space ASCII | |
822 | characters (namely HTABs and SPACEs) are treated as | |
823 | single spaces and may freely surround any symbol. In | |
824 | all header fields, the only place in which at least one | |
825 | LWSP-char is REQUIRED is at the beginning of continua- | |
826 | tion lines in a folded field. | |
827 | ||
828 | When passing text to processes that do not interpret text | |
829 | according to this standard (e.g., mail protocol servers), then | |
830 | NO linear-white-space characters should occur between a period | |
831 | (".") or at-sign ("@") and a <word>. Exactly ONE SPACE should | |
832 | be used in place of arbitrary linear-white-space and comment | |
833 | sequences. | |
834 | ||
835 | Note: Within systems conforming to this standard, wherever a | |
836 | member of the list of delimiters is allowed, LWSP-chars | |
837 | may also occur before and/or after it. | |
838 | ||
839 | Writers of mail-sending (i.e., header-generating) programs | |
840 | should realize that there is no network-wide definition of the | |
841 | effect of ASCII HT (horizontal-tab) characters on the appear- | |
842 | ance of text at another network host; therefore, the use of | |
843 | tabs in message headers, though permitted, is discouraged. | |
844 | ||
845 | 3.4.3. COMMENTS | |
846 | ||
847 | A comment is a set of ASCII characters, which is enclosed in | |
848 | matching parentheses and which is not within a quoted-string | |
849 | The comment construct permits message originators to add text | |
850 | which will be useful for human readers, but which will be | |
851 | ignored by the formal semantics. Comments should be retained | |
852 | while the message is subject to interpretation according to | |
853 | this standard. However, comments must NOT be included in | |
854 | other cases, such as during protocol exchanges with mail | |
855 | servers. | |
856 | ||
857 | Comments nest, so that if an unquoted left parenthesis occurs | |
858 | in a comment string, there must also be a matching right | |
859 | parenthesis. When a comment acts as the delimiter between a | |
860 | sequence of two lexical symbols, such as two atoms, it is lex- | |
861 | ically equivalent with a single SPACE, for the purposes of | |
862 | regenerating the sequence, such as when passing the sequence | |
863 | onto a mail protocol server. Comments are detected as such | |
864 | only within field-bodies of structured fields. | |
865 | ||
866 | If a comment is to be "folded" onto multiple lines, then the | |
867 | syntax for folding must be adhered to. (See the "Lexical | |
868 | ||
869 | ||
870 | August 13, 1982 - 12 - RFC #822 | |
871 | \f | |
872 | ||
873 | ||
874 | Standard for ARPA Internet Text Messages | |
875 | ||
876 | ||
877 | Analysis of Messages" section on "Folding Long Header Fields" | |
878 | above, and the section on "Case Independence" below.) Note | |
879 | that the official semantics therefore do not "see" any | |
880 | unquoted CRLFs that are in comments, although particular pars- | |
881 | ing programs may wish to note their presence. For these pro- | |
882 | grams, it would be reasonable to interpret a "CRLF LWSP-char" | |
883 | as being a CRLF that is part of the comment; i.e., the CRLF is | |
884 | kept and the LWSP-char is discarded. Quoted CRLFs (i.e., a | |
885 | backslash followed by a CR followed by a LF) still must be | |
886 | followed by at least one LWSP-char. | |
887 | ||
888 | 3.4.4. DELIMITING AND QUOTING CHARACTERS | |
889 | ||
890 | The quote character (backslash) and characters that delimit | |
891 | syntactic units are not, generally, to be taken as data that | |
892 | are part of the delimited or quoted unit(s). In particular, | |
893 | the quotation-marks that define a quoted-string, the | |
894 | parentheses that define a comment and the backslash that | |
895 | quotes a following character are NOT part of the quoted- | |
896 | string, comment or quoted character. A quotation-mark that is | |
897 | to be part of a quoted-string, a parenthesis that is to be | |
898 | part of a comment and a backslash that is to be part of either | |
899 | must each be preceded by the quote-character backslash ("\"). | |
900 | Note that the syntax allows any character to be quoted within | |
901 | a quoted-string or comment; however only certain characters | |
902 | MUST be quoted to be included as data. These characters are | |
903 | the ones that are not part of the alternate text group (i.e., | |
904 | ctext or qtext). | |
905 | ||
906 | The one exception to this rule is that a single SPACE is | |
907 | assumed to exist between contiguous words in a phrase, and | |
908 | this interpretation is independent of the actual number of | |
909 | LWSP-chars that the creator places between the words. To | |
910 | include more than one SPACE, the creator must make the LWSP- | |
911 | chars be part of a quoted-string. | |
912 | ||
913 | Quotation marks that delimit a quoted string and backslashes | |
914 | that quote the following character should NOT accompany the | |
915 | quoted-string when the string is passed to processes that do | |
916 | not interpret data according to this specification (e.g., mail | |
917 | protocol servers). | |
918 | ||
919 | 3.4.5. QUOTED-STRINGS | |
920 | ||
921 | Where permitted (i.e., in words in structured fields) quoted- | |
922 | strings are treated as a single symbol. That is, a quoted- | |
923 | string is equivalent to an atom, syntactically. If a quoted- | |
924 | string is to be "folded" onto multiple lines, then the syntax | |
925 | for folding must be adhered to. (See the "Lexical Analysis of | |
926 | ||
927 | ||
928 | August 13, 1982 - 13 - RFC #822 | |
929 | \f | |
930 | ||
931 | ||
932 | Standard for ARPA Internet Text Messages | |
933 | ||
934 | ||
935 | Messages" section on "Folding Long Header Fields" above, and | |
936 | the section on "Case Independence" below.) Therefore, the | |
937 | official semantics do not "see" any bare CRLFs that are in | |
938 | quoted-strings; however particular parsing programs may wish | |
939 | to note their presence. For such programs, it would be rea- | |
940 | sonable to interpret a "CRLF LWSP-char" as being a CRLF which | |
941 | is part of the quoted-string; i.e., the CRLF is kept and the | |
942 | LWSP-char is discarded. Quoted CRLFs (i.e., a backslash fol- | |
943 | lowed by a CR followed by a LF) are also subject to rules of | |
944 | folding, but the presence of the quoting character (backslash) | |
945 | explicitly indicates that the CRLF is data to the quoted | |
946 | string. Stripping off the first following LWSP-char is also | |
947 | appropriate when parsing quoted CRLFs. | |
948 | ||
949 | 3.4.6. BRACKETING CHARACTERS | |
950 | ||
951 | There is one type of bracket which must occur in matched pairs | |
952 | and may have pairs nested within each other: | |
953 | ||
954 | o Parentheses ("(" and ")") are used to indicate com- | |
955 | ments. | |
956 | ||
957 | There are three types of brackets which must occur in matched | |
958 | pairs, and which may NOT be nested: | |
959 | ||
960 | o Colon/semi-colon (":" and ";") are used in address | |
961 | specifications to indicate that the included list of | |
962 | addresses are to be treated as a group. | |
963 | ||
964 | o Angle brackets ("<" and ">") are generally used to | |
965 | indicate the presence of a one machine-usable refer- | |
966 | ence (e.g., delimiting mailboxes), possibly including | |
967 | source-routing to the machine. | |
968 | ||
969 | o Square brackets ("[" and "]") are used to indicate the | |
970 | presence of a domain-literal, which the appropriate | |
971 | name-domain is to use directly, bypassing normal | |
972 | name-resolution mechanisms. | |
973 | ||
974 | 3.4.7. CASE INDEPENDENCE | |
975 | ||
976 | Except as noted, alphabetic strings may be represented in any | |
977 | combination of upper and lower case. The only syntactic units | |
978 | ||
979 | ||
980 | ||
981 | ||
982 | ||
983 | ||
984 | ||
985 | ||
986 | August 13, 1982 - 14 - RFC #822 | |
987 | \f | |
988 | ||
989 | ||
990 | Standard for ARPA Internet Text Messages | |
991 | ||
992 | ||
993 | which requires preservation of case information are: | |
994 | ||
995 | - text | |
996 | - qtext | |
997 | - dtext | |
998 | - ctext | |
999 | - quoted-pair | |
1000 | - local-part, except "Postmaster" | |
1001 | ||
1002 | When matching any other syntactic unit, case is to be ignored. | |
1003 | For example, the field-names "From", "FROM", "from", and even | |
1004 | "FroM" are semantically equal and should all be treated ident- | |
1005 | ically. | |
1006 | ||
1007 | When generating these units, any mix of upper and lower case | |
1008 | alphabetic characters may be used. The case shown in this | |
1009 | specification is suggested for message-creating processes. | |
1010 | ||
1011 | Note: The reserved local-part address unit, "Postmaster", is | |
1012 | an exception. When the value "Postmaster" is being | |
1013 | interpreted, it must be accepted in any mixture of | |
1014 | case, including "POSTMASTER", and "postmaster". | |
1015 | ||
1016 | 3.4.8. FOLDING LONG HEADER FIELDS | |
1017 | ||
1018 | Each header field may be represented on exactly one line con- | |
1019 | sisting of the name of the field and its body, and terminated | |
1020 | by a CRLF; this is what the parser sees. For readability, the | |
1021 | field-body portion of long header fields may be "folded" onto | |
1022 | multiple lines of the actual field. "Long" is commonly inter- | |
1023 | preted to mean greater than 65 or 72 characters. The former | |
1024 | length serves as a limit, when the message is to be viewed on | |
1025 | most simple terminals which use simple display software; how- | |
1026 | ever, the limit is not imposed by this standard. | |
1027 | ||
1028 | Note: Some display software often can selectively fold lines, | |
1029 | to suit the display terminal. In such cases, sender- | |
1030 | provided folding can interfere with the display | |
1031 | software. | |
1032 | ||
1033 | 3.4.9. BACKSPACE CHARACTERS | |
1034 | ||
1035 | ASCII BS characters (Backspace, decimal 8) may be included in | |
1036 | texts and quoted-strings to effect overstriking. However, any | |
1037 | use of backspaces which effects an overstrike to the left of | |
1038 | the beginning of the text or quoted-string is prohibited. | |
1039 | ||
1040 | ||
1041 | ||
1042 | ||
1043 | ||
1044 | August 13, 1982 - 15 - RFC #822 | |
1045 | \f | |
1046 | ||
1047 | ||
1048 | Standard for ARPA Internet Text Messages | |
1049 | ||
1050 | ||
1051 | 3.4.10. NETWORK-SPECIFIC TRANSFORMATIONS | |
1052 | ||
1053 | During transmission through heterogeneous networks, it may be | |
1054 | necessary to force data to conform to a network's local con- | |
1055 | ventions. For example, it may be required that a CR be fol- | |
1056 | lowed either by LF, making a CRLF, or by <null>, if the CR is | |
1057 | to stand alone). Such transformations are reversed, when the | |
1058 | message exits that network. | |
1059 | ||
1060 | When crossing network boundaries, the message should be | |
1061 | treated as passing through two modules. It will enter the | |
1062 | first module containing whatever network-specific transforma- | |
1063 | tions that were necessary to permit migration through the | |
1064 | "current" network. It then passes through the modules: | |
1065 | ||
1066 | o Transformation Reversal | |
1067 | ||
1068 | The "current" network's idiosyncracies are removed and | |
1069 | the message is returned to the canonical form speci- | |
1070 | fied in this standard. | |
1071 | ||
1072 | o Transformation | |
1073 | ||
1074 | The "next" network's local idiosyncracies are imposed | |
1075 | on the message. | |
1076 | ||
1077 | ------------------ | |
1078 | From ==> | Remove Net-A | | |
1079 | Net-A | idiosyncracies | | |
1080 | ------------------ | |
1081 | || | |
1082 | \/ | |
1083 | Conformance | |
1084 | with standard | |
1085 | || | |
1086 | \/ | |
1087 | ------------------ | |
1088 | | Impose Net-B | ==> To | |
1089 | | idiosyncracies | Net-B | |
1090 | ------------------ | |
1091 | ||
1092 | ||
1093 | ||
1094 | ||
1095 | ||
1096 | ||
1097 | ||
1098 | ||
1099 | ||
1100 | ||
1101 | ||
1102 | August 13, 1982 - 16 - RFC #822 | |
1103 | \f | |
1104 | ||
1105 | ||
1106 | Standard for ARPA Internet Text Messages | |
1107 | ||
1108 | ||
1109 | 4. MESSAGE SPECIFICATION | |
1110 | ||
1111 | 4.1. SYNTAX | |
1112 | ||
1113 | Note: Due to an artifact of the notational conventions, the syn- | |
1114 | tax indicates that, when present, some fields, must be in | |
1115 | a particular order. Header fields are NOT required to | |
1116 | occur in any particular order, except that the message | |
1117 | body must occur AFTER the headers. It is recommended | |
1118 | that, if present, headers be sent in the order "Return- | |
1119 | Path", "Received", "Date", "From", "Subject", "Sender", | |
1120 | "To", "cc", etc. | |
1121 | ||
1122 | This specification permits multiple occurrences of most | |
1123 | fields. Except as noted, their interpretation is not | |
1124 | specified here, and their use is discouraged. | |
1125 | ||
1126 | The following syntax for the bodies of various fields should | |
1127 | be thought of as describing each field body as a single long | |
1128 | string (or line). The "Lexical Analysis of Message" section on | |
1129 | "Long Header Fields", above, indicates how such long strings can | |
1130 | be represented on more than one line in the actual transmitted | |
1131 | message. | |
1132 | ||
1133 | message = fields *( CRLF *text ) ; Everything after | |
1134 | ; first null line | |
1135 | ; is message body | |
1136 | ||
1137 | fields = dates ; Creation time, | |
1138 | source ; author id & one | |
1139 | 1*destination ; address required | |
1140 | *optional-field ; others optional | |
1141 | ||
1142 | source = [ trace ] ; net traversals | |
1143 | originator ; original mail | |
1144 | [ resent ] ; forwarded | |
1145 | ||
1146 | trace = return ; path to sender | |
1147 | 1*received ; receipt tags | |
1148 | ||
1149 | return = "Return-path" ":" route-addr ; return address | |
1150 | ||
1151 | received = "Received" ":" ; one per relay | |
1152 | ["from" domain] ; sending host | |
1153 | ["by" domain] ; receiving host | |
1154 | ["via" atom] ; physical path | |
1155 | *("with" atom) ; link/mail protocol | |
1156 | ["id" msg-id] ; receiver msg id | |
1157 | ["for" addr-spec] ; initial form | |
1158 | ||
1159 | ||
1160 | August 13, 1982 - 17 - RFC #822 | |
1161 | \f | |
1162 | ||
1163 | ||
1164 | Standard for ARPA Internet Text Messages | |
1165 | ||
1166 | ||
1167 | ";" date-time ; time received | |
1168 | ||
1169 | originator = authentic ; authenticated addr | |
1170 | [ "Reply-To" ":" 1#address] ) | |
1171 | ||
1172 | authentic = "From" ":" mailbox ; Single author | |
1173 | / ( "Sender" ":" mailbox ; Actual submittor | |
1174 | "From" ":" 1#mailbox) ; Multiple authors | |
1175 | ; or not sender | |
1176 | ||
1177 | resent = resent-authentic | |
1178 | [ "Resent-Reply-To" ":" 1#address] ) | |
1179 | ||
1180 | resent-authentic = | |
1181 | = "Resent-From" ":" mailbox | |
1182 | / ( "Resent-Sender" ":" mailbox | |
1183 | "Resent-From" ":" 1#mailbox ) | |
1184 | ||
1185 | dates = orig-date ; Original | |
1186 | [ resent-date ] ; Forwarded | |
1187 | ||
1188 | orig-date = "Date" ":" date-time | |
1189 | ||
1190 | resent-date = "Resent-Date" ":" date-time | |
1191 | ||
1192 | destination = "To" ":" 1#address ; Primary | |
1193 | / "Resent-To" ":" 1#address | |
1194 | / "cc" ":" 1#address ; Secondary | |
1195 | / "Resent-cc" ":" 1#address | |
1196 | / "bcc" ":" #address ; Blind carbon | |
1197 | / "Resent-bcc" ":" #address | |
1198 | ||
1199 | optional-field = | |
1200 | / "Message-ID" ":" msg-id | |
1201 | / "Resent-Message-ID" ":" msg-id | |
1202 | / "In-Reply-To" ":" *(phrase / msg-id) | |
1203 | / "References" ":" *(phrase / msg-id) | |
1204 | / "Keywords" ":" #phrase | |
1205 | / "Subject" ":" *text | |
1206 | / "Comments" ":" *text | |
1207 | / "Encrypted" ":" 1#2word | |
1208 | / extension-field ; To be defined | |
1209 | / user-defined-field ; May be pre-empted | |
1210 | ||
1211 | msg-id = "<" addr-spec ">" ; Unique message id | |
1212 | ||
1213 | ||
1214 | ||
1215 | ||
1216 | ||
1217 | ||
1218 | August 13, 1982 - 18 - RFC #822 | |
1219 | \f | |
1220 | ||
1221 | ||
1222 | Standard for ARPA Internet Text Messages | |
1223 | ||
1224 | ||
1225 | extension-field = | |
1226 | <Any field which is defined in a document | |
1227 | published as a formal extension to this | |
1228 | specification; none will have names beginning | |
1229 | with the string "X-"> | |
1230 | ||
1231 | user-defined-field = | |
1232 | <Any field which has not been defined | |
1233 | in this specification or published as an | |
1234 | extension to this specification; names for | |
1235 | such fields must be unique and may be | |
1236 | pre-empted by published extensions> | |
1237 | ||
1238 | 4.2. FORWARDING | |
1239 | ||
1240 | Some systems permit mail recipients to forward a message, | |
1241 | retaining the original headers, by adding some new fields. This | |
1242 | standard supports such a service, through the "Resent-" prefix to | |
1243 | field names. | |
1244 | ||
1245 | Whenever the string "Resent-" begins a field name, the field | |
1246 | has the same semantics as a field whose name does not have the | |
1247 | prefix. However, the message is assumed to have been forwarded | |
1248 | by an original recipient who attached the "Resent-" field. This | |
1249 | new field is treated as being more recent than the equivalent, | |
1250 | original field. For example, the "Resent-From", indicates the | |
1251 | person that forwarded the message, whereas the "From" field indi- | |
1252 | cates the original author. | |
1253 | ||
1254 | Use of such precedence information depends upon partici- | |
1255 | pants' communication needs. For example, this standard does not | |
1256 | dictate when a "Resent-From:" address should receive replies, in | |
1257 | lieu of sending them to the "From:" address. | |
1258 | ||
1259 | Note: In general, the "Resent-" fields should be treated as con- | |
1260 | taining a set of information that is independent of the | |
1261 | set of original fields. Information for one set should | |
1262 | not automatically be taken from the other. The interpre- | |
1263 | tation of multiple "Resent-" fields, of the same type, is | |
1264 | undefined. | |
1265 | ||
1266 | In the remainder of this specification, occurrence of legal | |
1267 | "Resent-" fields are treated identically with the occurrence of | |
1268 | ||
1269 | ||
1270 | ||
1271 | ||
1272 | ||
1273 | ||
1274 | ||
1275 | ||
1276 | August 13, 1982 - 19 - RFC #822 | |
1277 | \f | |
1278 | ||
1279 | ||
1280 | Standard for ARPA Internet Text Messages | |
1281 | ||
1282 | ||
1283 | fields whose names do not contain this prefix. | |
1284 | ||
1285 | 4.3. TRACE FIELDS | |
1286 | ||
1287 | Trace information is used to provide an audit trail of mes- | |
1288 | sage handling. In addition, it indicates a route back to the | |
1289 | sender of the message. | |
1290 | ||
1291 | The list of known "via" and "with" values are registered | |
1292 | with the Network Information Center, SRI International, Menlo | |
1293 | Park, California. | |
1294 | ||
1295 | 4.3.1. RETURN-PATH | |
1296 | ||
1297 | This field is added by the final transport system that | |
1298 | delivers the message to its recipient. The field is intended | |
1299 | to contain definitive information about the address and route | |
1300 | back to the message's originator. | |
1301 | ||
1302 | Note: The "Reply-To" field is added by the originator and | |
1303 | serves to direct replies, whereas the "Return-Path" | |
1304 | field is used to identify a path back to the origina- | |
1305 | tor. | |
1306 | ||
1307 | While the syntax indicates that a route specification is | |
1308 | optional, every attempt should be made to provide that infor- | |
1309 | mation in this field. | |
1310 | ||
1311 | 4.3.2. RECEIVED | |
1312 | ||
1313 | A copy of this field is added by each transport service that | |
1314 | relays the message. The information in the field can be quite | |
1315 | useful for tracing transport problems. | |
1316 | ||
1317 | The names of the sending and receiving hosts and time-of- | |
1318 | receipt may be specified. The "via" parameter may be used, to | |
1319 | indicate what physical mechanism the message was sent over, | |
1320 | such as Arpanet or Phonenet, and the "with" parameter may be | |
1321 | used to indicate the mail-, or connection-, level protocol | |
1322 | that was used, such as the SMTP mail protocol, or X.25 tran- | |
1323 | sport protocol. | |
1324 | ||
1325 | Note: Several "with" parameters may be included, to fully | |
1326 | specify the set of protocols that were used. | |
1327 | ||
1328 | Some transport services queue mail; the internal message iden- | |
1329 | tifier that is assigned to the message may be noted, using the | |
1330 | "id" parameter. When the sending host uses a destination | |
1331 | address specification that the receiving host reinterprets, by | |
1332 | ||
1333 | ||
1334 | August 13, 1982 - 20 - RFC #822 | |
1335 | \f | |
1336 | ||
1337 | ||
1338 | Standard for ARPA Internet Text Messages | |
1339 | ||
1340 | ||
1341 | expansion or transformation, the receiving host may wish to | |
1342 | record the original specification, using the "for" parameter. | |
1343 | For example, when a copy of mail is sent to the member of a | |
1344 | distribution list, this parameter may be used to record the | |
1345 | original address that was used to specify the list. | |
1346 | ||
1347 | 4.4. ORIGINATOR FIELDS | |
1348 | ||
1349 | The standard allows only a subset of the combinations possi- | |
1350 | ble with the From, Sender, Reply-To, Resent-From, Resent-Sender, | |
1351 | and Resent-Reply-To fields. The limitation is intentional. | |
1352 | ||
1353 | 4.4.1. FROM / RESENT-FROM | |
1354 | ||
1355 | This field contains the identity of the person(s) who wished | |
1356 | this message to be sent. The message-creation process should | |
1357 | default this field to be a single, authenticated machine | |
1358 | address, indicating the AGENT (person, system or process) | |
1359 | entering the message. If this is not done, the "Sender" field | |
1360 | MUST be present. If the "From" field IS defaulted this way, | |
1361 | the "Sender" field is optional and is redundant with the | |
1362 | "From" field. In all cases, addresses in the "From" field | |
1363 | must be machine-usable (addr-specs) and may not contain named | |
1364 | lists (groups). | |
1365 | ||
1366 | 4.4.2. SENDER / RESENT-SENDER | |
1367 | ||
1368 | This field contains the authenticated identity of the AGENT | |
1369 | (person, system or process) that sends the message. It is | |
1370 | intended for use when the sender is not the author of the mes- | |
1371 | sage, or to indicate who among a group of authors actually | |
1372 | sent the message. If the contents of the "Sender" field would | |
1373 | be completely redundant with the "From" field, then the | |
1374 | "Sender" field need not be present and its use is discouraged | |
1375 | (though still legal). In particular, the "Sender" field MUST | |
1376 | be present if it is NOT the same as the "From" Field. | |
1377 | ||
1378 | The Sender mailbox specification includes a word sequence | |
1379 | which must correspond to a specific agent (i.e., a human user | |
1380 | or a computer program) rather than a standard address. This | |
1381 | indicates the expectation that the field will identify the | |
1382 | single AGENT (person, system, or process) responsible for | |
1383 | sending the mail and not simply include the name of a mailbox | |
1384 | from which the mail was sent. For example in the case of a | |
1385 | shared login name, the name, by itself, would not be adequate. | |
1386 | The local-part address unit, which refers to this agent, is | |
1387 | expected to be a computer system term, and not (for example) a | |
1388 | generalized person reference which can be used outside the | |
1389 | network text message context. | |
1390 | ||
1391 | ||
1392 | August 13, 1982 - 21 - RFC #822 | |
1393 | \f | |
1394 | ||
1395 | ||
1396 | Standard for ARPA Internet Text Messages | |
1397 | ||
1398 | ||
1399 | Since the critical function served by the "Sender" field is | |
1400 | identification of the agent responsible for sending mail and | |
1401 | since computer programs cannot be held accountable for their | |
1402 | behavior, it is strongly recommended that when a computer pro- | |
1403 | gram generates a message, the HUMAN who is responsible for | |
1404 | that program be referenced as part of the "Sender" field mail- | |
1405 | box specification. | |
1406 | ||
1407 | 4.4.3. REPLY-TO / RESENT-REPLY-TO | |
1408 | ||
1409 | This field provides a general mechanism for indicating any | |
1410 | mailbox(es) to which responses are to be sent. Three typical | |
1411 | uses for this feature can be distinguished. In the first | |
1412 | case, the author(s) may not have regular machine-based mail- | |
1413 | boxes and therefore wish(es) to indicate an alternate machine | |
1414 | address. In the second case, an author may wish additional | |
1415 | persons to be made aware of, or responsible for, replies. A | |
1416 | somewhat different use may be of some help to "text message | |
1417 | teleconferencing" groups equipped with automatic distribution | |
1418 | services: include the address of that service in the "Reply- | |
1419 | To" field of all messages submitted to the teleconference; | |
1420 | then participants can "reply" to conference submissions to | |
1421 | guarantee the correct distribution of any submission of their | |
1422 | own. | |
1423 | ||
1424 | Note: The "Return-Path" field is added by the mail transport | |
1425 | service, at the time of final deliver. It is intended | |
1426 | to identify a path back to the orginator of the mes- | |
1427 | sage. The "Reply-To" field is added by the message | |
1428 | originator and is intended to direct replies. | |
1429 | ||
1430 | 4.4.4. AUTOMATIC USE OF FROM / SENDER / REPLY-TO | |
1431 | ||
1432 | For systems which automatically generate address lists for | |
1433 | replies to messages, the following recommendations are made: | |
1434 | ||
1435 | o The "Sender" field mailbox should be sent notices of | |
1436 | any problems in transport or delivery of the original | |
1437 | messages. If there is no "Sender" field, then the | |
1438 | "From" field mailbox should be used. | |
1439 | ||
1440 | o The "Sender" field mailbox should NEVER be used | |
1441 | automatically, in a recipient's reply message. | |
1442 | ||
1443 | o If the "Reply-To" field exists, then the reply should | |
1444 | go to the addresses indicated in that field and not to | |
1445 | the address(es) indicated in the "From" field. | |
1446 | ||
1447 | ||
1448 | ||
1449 | ||
1450 | August 13, 1982 - 22 - RFC #822 | |
1451 | \f | |
1452 | ||
1453 | ||
1454 | Standard for ARPA Internet Text Messages | |
1455 | ||
1456 | ||
1457 | o If there is a "From" field, but no "Reply-To" field, | |
1458 | the reply should be sent to the address(es) indicated | |
1459 | in the "From" field. | |
1460 | ||
1461 | Sometimes, a recipient may actually wish to communicate with | |
1462 | the person that initiated the message transfer. In such | |
1463 | cases, it is reasonable to use the "Sender" address. | |
1464 | ||
1465 | This recommendation is intended only for automated use of | |
1466 | originator-fields and is not intended to suggest that replies | |
1467 | may not also be sent to other recipients of messages. It is | |
1468 | up to the respective mail-handling programs to decide what | |
1469 | additional facilities will be provided. | |
1470 | ||
1471 | Examples are provided in Appendix A. | |
1472 | ||
1473 | 4.5. RECEIVER FIELDS | |
1474 | ||
1475 | 4.5.1. TO / RESENT-TO | |
1476 | ||
1477 | This field contains the identity of the primary recipients of | |
1478 | the message. | |
1479 | ||
1480 | 4.5.2. CC / RESENT-CC | |
1481 | ||
1482 | This field contains the identity of the secondary (informa- | |
1483 | tional) recipients of the message. | |
1484 | ||
1485 | 4.5.3. BCC / RESENT-BCC | |
1486 | ||
1487 | This field contains the identity of additional recipients of | |
1488 | the message. The contents of this field are not included in | |
1489 | copies of the message sent to the primary and secondary reci- | |
1490 | pients. Some systems may choose to include the text of the | |
1491 | "Bcc" field only in the author(s)'s copy, while others may | |
1492 | also include it in the text sent to all those indicated in the | |
1493 | "Bcc" list. | |
1494 | ||
1495 | 4.6. REFERENCE FIELDS | |
1496 | ||
1497 | 4.6.1. MESSAGE-ID / RESENT-MESSAGE-ID | |
1498 | ||
1499 | This field contains a unique identifier (the local-part | |
1500 | address unit) which refers to THIS version of THIS message. | |
1501 | The uniqueness of the message identifier is guaranteed by the | |
1502 | host which generates it. This identifier is intended to be | |
1503 | machine readable and not necessarily meaningful to humans. A | |
1504 | message identifier pertains to exactly one instantiation of a | |
1505 | particular message; subsequent revisions to the message should | |
1506 | ||
1507 | ||
1508 | August 13, 1982 - 23 - RFC #822 | |
1509 | \f | |
1510 | ||
1511 | ||
1512 | Standard for ARPA Internet Text Messages | |
1513 | ||
1514 | ||
1515 | each receive new message identifiers. | |
1516 | ||
1517 | 4.6.2. IN-REPLY-TO | |
1518 | ||
1519 | The contents of this field identify previous correspon- | |
1520 | dence which this message answers. Note that if message iden- | |
1521 | tifiers are used in this field, they must use the msg-id | |
1522 | specification format. | |
1523 | ||
1524 | 4.6.3. REFERENCES | |
1525 | ||
1526 | The contents of this field identify other correspondence | |
1527 | which this message references. Note that if message identif- | |
1528 | iers are used, they must use the msg-id specification format. | |
1529 | ||
1530 | 4.6.4. KEYWORDS | |
1531 | ||
1532 | This field contains keywords or phrases, separated by | |
1533 | commas. | |
1534 | ||
1535 | 4.7. OTHER FIELDS | |
1536 | ||
1537 | 4.7.1. SUBJECT | |
1538 | ||
1539 | This is intended to provide a summary, or indicate the | |
1540 | nature, of the message. | |
1541 | ||
1542 | 4.7.2. COMMENTS | |
1543 | ||
1544 | Permits adding text comments onto the message without | |
1545 | disturbing the contents of the message's body. | |
1546 | ||
1547 | 4.7.3. ENCRYPTED | |
1548 | ||
1549 | Sometimes, data encryption is used to increase the | |
1550 | privacy of message contents. If the body of a message has | |
1551 | been encrypted, to keep its contents private, the "Encrypted" | |
1552 | field can be used to note the fact and to indicate the nature | |
1553 | of the encryption. The first <word> parameter indicates the | |
1554 | software used to encrypt the body, and the second, optional | |
1555 | <word> is intended to aid the recipient in selecting the | |
1556 | proper decryption key. This code word may be viewed as an | |
1557 | index to a table of keys held by the recipient. | |
1558 | ||
1559 | Note: Unfortunately, headers must contain envelope, as well | |
1560 | as contents, information. Consequently, it is neces- | |
1561 | sary that they remain unencrypted, so that mail tran- | |
1562 | sport services may access them. Since names, | |
1563 | addresses, and "Subject" field contents may contain | |
1564 | ||
1565 | ||
1566 | August 13, 1982 - 24 - RFC #822 | |
1567 | \f | |
1568 | ||
1569 | ||
1570 | Standard for ARPA Internet Text Messages | |
1571 | ||
1572 | ||
1573 | sensitive information, this requirement limits total | |
1574 | message privacy. | |
1575 | ||
1576 | Names of encryption software are registered with the Net- | |
1577 | work Information Center, SRI International, Menlo Park, Cali- | |
1578 | fornia. | |
1579 | ||
1580 | 4.7.4. EXTENSION-FIELD | |
1581 | ||
1582 | A limited number of common fields have been defined in | |
1583 | this document. As network mail requirements dictate, addi- | |
1584 | tional fields may be standardized. To provide user-defined | |
1585 | fields with a measure of safety, in name selection, such | |
1586 | extension-fields will never have names that begin with the | |
1587 | string "X-". | |
1588 | ||
1589 | Names of Extension-fields are registered with the Network | |
1590 | Information Center, SRI International, Menlo Park, California. | |
1591 | ||
1592 | 4.7.5. USER-DEFINED-FIELD | |
1593 | ||
1594 | Individual users of network mail are free to define and | |
1595 | use additional header fields. Such fields must have names | |
1596 | which are not already used in the current specification or in | |
1597 | any definitions of extension-fields, and the overall syntax of | |
1598 | these user-defined-fields must conform to this specification's | |
1599 | rules for delimiting and folding fields. Due to the | |
1600 | extension-field publishing process, the name of a user- | |
1601 | defined-field may be pre-empted | |
1602 | ||
1603 | Note: The prefatory string "X-" will never be used in the | |
1604 | names of Extension-fields. This provides user-defined | |
1605 | fields with a protected set of names. | |
1606 | ||
1607 | ||
1608 | ||
1609 | ||
1610 | ||
1611 | ||
1612 | ||
1613 | ||
1614 | ||
1615 | ||
1616 | ||
1617 | ||
1618 | ||
1619 | ||
1620 | ||
1621 | ||
1622 | ||
1623 | ||
1624 | August 13, 1982 - 25 - RFC #822 | |
1625 | \f | |
1626 | ||
1627 | ||
1628 | Standard for ARPA Internet Text Messages | |
1629 | ||
1630 | ||
1631 | 5. DATE AND TIME SPECIFICATION | |
1632 | ||
1633 | 5.1. SYNTAX | |
1634 | ||
1635 | date-time = [ day "," ] date time ; dd mm yy | |
1636 | ; hh:mm:ss zzz | |
1637 | ||
1638 | day = "Mon" / "Tue" / "Wed" / "Thu" | |
1639 | / "Fri" / "Sat" / "Sun" | |
1640 | ||
1641 | date = 1*2DIGIT month 2DIGIT ; day month year | |
1642 | ; e.g. 20 Jun 82 | |
1643 | ||
1644 | month = "Jan" / "Feb" / "Mar" / "Apr" | |
1645 | / "May" / "Jun" / "Jul" / "Aug" | |
1646 | / "Sep" / "Oct" / "Nov" / "Dec" | |
1647 | ||
1648 | time = hour zone ; ANSI and Military | |
1649 | ||
1650 | hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT] | |
1651 | ; 00:00:00 - 23:59:59 | |
1652 | ||
1653 | zone = "UT" / "GMT" ; Universal Time | |
1654 | ; North American : UT | |
1655 | / "EST" / "EDT" ; Eastern: - 5/ - 4 | |
1656 | / "CST" / "CDT" ; Central: - 6/ - 5 | |
1657 | / "MST" / "MDT" ; Mountain: - 7/ - 6 | |
1658 | / "PST" / "PDT" ; Pacific: - 8/ - 7 | |
1659 | / 1ALPHA ; Military: Z = UT; | |
1660 | ; A:-1; (J not used) | |
1661 | ; M:-12; N:+1; Y:+12 | |
1662 | / ( ("+" / "-") 4DIGIT ) ; Local differential | |
1663 | ; hours+min. (HHMM) | |
1664 | ||
1665 | 5.2. SEMANTICS | |
1666 | ||
1667 | If included, day-of-week must be the day implied by the date | |
1668 | specification. | |
1669 | ||
1670 | Time zone may be indicated in several ways. "UT" is Univer- | |
1671 | sal Time (formerly called "Greenwich Mean Time"); "GMT" is per- | |
1672 | mitted as a reference to Universal Time. The military standard | |
1673 | uses a single character for each zone. "Z" is Universal Time. | |
1674 | "A" indicates one hour earlier, and "M" indicates 12 hours ear- | |
1675 | lier; "N" is one hour later, and "Y" is 12 hours later. The | |
1676 | letter "J" is not used. The other remaining two forms are taken | |
1677 | from ANSI standard X3.51-1975. One allows explicit indication of | |
1678 | the amount of offset from UT; the other uses common 3-character | |
1679 | strings for indicating time zones in North America. | |
1680 | ||
1681 | ||
1682 | August 13, 1982 - 26 - RFC #822 | |
1683 | \f | |
1684 | ||
1685 | ||
1686 | Standard for ARPA Internet Text Messages | |
1687 | ||
1688 | ||
1689 | 6. ADDRESS SPECIFICATION | |
1690 | ||
1691 | 6.1. SYNTAX | |
1692 | ||
1693 | address = mailbox ; one addressee | |
1694 | / group ; named list | |
1695 | ||
1696 | group = phrase ":" [#mailbox] ";" | |
1697 | ||
1698 | mailbox = addr-spec ; simple address | |
1699 | / phrase route-addr ; name & addr-spec | |
1700 | ||
1701 | route-addr = "<" [route] addr-spec ">" | |
1702 | ||
1703 | route = 1#("@" domain) ":" ; path-relative | |
1704 | ||
1705 | addr-spec = local-part "@" domain ; global address | |
1706 | ||
1707 | local-part = word *("." word) ; uninterpreted | |
1708 | ; case-preserved | |
1709 | ||
1710 | domain = sub-domain *("." sub-domain) | |
1711 | ||
1712 | sub-domain = domain-ref / domain-literal | |
1713 | ||
1714 | domain-ref = atom ; symbolic reference | |
1715 | ||
1716 | 6.2. SEMANTICS | |
1717 | ||
1718 | A mailbox receives mail. It is a conceptual entity which | |
1719 | does not necessarily pertain to file storage. For example, some | |
1720 | sites may choose to print mail on their line printer and deliver | |
1721 | the output to the addressee's desk. | |
1722 | ||
1723 | A mailbox specification comprises a person, system or pro- | |
1724 | cess name reference, a domain-dependent string, and a name-domain | |
1725 | reference. The name reference is optional and is usually used to | |
1726 | indicate the human name of a recipient. The name-domain refer- | |
1727 | ence specifies a sequence of sub-domains. The domain-dependent | |
1728 | string is uninterpreted, except by the final sub-domain; the rest | |
1729 | of the mail service merely transmits it as a literal string. | |
1730 | ||
1731 | 6.2.1. DOMAINS | |
1732 | ||
1733 | A name-domain is a set of registered (mail) names. A name- | |
1734 | domain specification resolves to a subordinate name-domain | |
1735 | specification or to a terminal domain-dependent string. | |
1736 | Hence, domain specification is extensible, permitting any | |
1737 | number of registration levels. | |
1738 | ||
1739 | ||
1740 | August 13, 1982 - 27 - RFC #822 | |
1741 | \f | |
1742 | ||
1743 | ||
1744 | Standard for ARPA Internet Text Messages | |
1745 | ||
1746 | ||
1747 | Name-domains model a global, logical, hierarchical addressing | |
1748 | scheme. The model is logical, in that an address specifica- | |
1749 | tion is related to name registration and is not necessarily | |
1750 | tied to transmission path. The model's hierarchy is a | |
1751 | directed graph, called an in-tree, such that there is a single | |
1752 | path from the root of the tree to any node in the hierarchy. | |
1753 | If more than one path actually exists, they are considered to | |
1754 | be different addresses. | |
1755 | ||
1756 | The root node is common to all addresses; consequently, it is | |
1757 | not referenced. Its children constitute "top-level" name- | |
1758 | domains. Usually, a service has access to its own full domain | |
1759 | specification and to the names of all top-level name-domains. | |
1760 | ||
1761 | The "top" of the domain addressing hierarchy -- a child of the | |
1762 | root -- is indicated by the right-most field, in a domain | |
1763 | specification. Its child is specified to the left, its child | |
1764 | to the left, and so on. | |
1765 | ||
1766 | Some groups provide formal registration services; these con- | |
1767 | stitute name-domains that are independent logically of | |
1768 | specific machines. In addition, networks and machines impli- | |
1769 | citly compose name-domains, since their membership usually is | |
1770 | registered in name tables. | |
1771 | ||
1772 | In the case of formal registration, an organization implements | |
1773 | a (distributed) data base which provides an address-to-route | |
1774 | mapping service for addresses of the form: | |
1775 | ||
1776 | person@registry.organization | |
1777 | ||
1778 | Note that "organization" is a logical entity, separate from | |
1779 | any particular communication network. | |
1780 | ||
1781 | A mechanism for accessing "organization" is universally avail- | |
1782 | able. That mechanism, in turn, seeks an instantiation of the | |
1783 | registry; its location is not indicated in the address specif- | |
1784 | ication. It is assumed that the system which operates under | |
1785 | the name "organization" knows how to find a subordinate regis- | |
1786 | try. The registry will then use the "person" string to deter- | |
1787 | mine where to send the mail specification. | |
1788 | ||
1789 | The latter, network-oriented case permits simple, direct, | |
1790 | attachment-related address specification, such as: | |
1791 | ||
1792 | user@host.network | |
1793 | ||
1794 | Once the network is accessed, it is expected that a message | |
1795 | will go directly to the host and that the host will resolve | |
1796 | ||
1797 | ||
1798 | August 13, 1982 - 28 - RFC #822 | |
1799 | \f | |
1800 | ||
1801 | ||
1802 | Standard for ARPA Internet Text Messages | |
1803 | ||
1804 | ||
1805 | the user name, placing the message in the user's mailbox. | |
1806 | ||
1807 | 6.2.2. ABBREVIATED DOMAIN SPECIFICATION | |
1808 | ||
1809 | Since any number of levels is possible within the domain | |
1810 | hierarchy, specification of a fully qualified address can | |
1811 | become inconvenient. This standard permits abbreviated domain | |
1812 | specification, in a special case: | |
1813 | ||
1814 | For the address of the sender, call the left-most | |
1815 | sub-domain Level N. In a header address, if all of | |
1816 | the sub-domains above (i.e., to the right of) Level N | |
1817 | are the same as those of the sender, then they do not | |
1818 | have to appear in the specification. Otherwise, the | |
1819 | address must be fully qualified. | |
1820 | ||
1821 | This feature is subject to approval by local sub- | |
1822 | domains. Individual sub-domains may require their | |
1823 | member systems, which originate mail, to provide full | |
1824 | domain specification only. When permitted, abbrevia- | |
1825 | tions may be present only while the message stays | |
1826 | within the sub-domain of the sender. | |
1827 | ||
1828 | Use of this mechanism requires the sender's sub-domain | |
1829 | to reserve the names of all top-level domains, so that | |
1830 | full specifications can be distinguished from abbrevi- | |
1831 | ated specifications. | |
1832 | ||
1833 | For example, if a sender's address is: | |
1834 | ||
1835 | sender@registry-A.registry-1.organization-X | |
1836 | ||
1837 | and one recipient's address is: | |
1838 | ||
1839 | recipient@registry-B.registry-1.organization-X | |
1840 | ||
1841 | and another's is: | |
1842 | ||
1843 | recipient@registry-C.registry-2.organization-X | |
1844 | ||
1845 | then ".registry-1.organization-X" need not be specified in the | |
1846 | the message, but "registry-C.registry-2" DOES have to be | |
1847 | specified. That is, the first two addresses may be abbrevi- | |
1848 | ated, but the third address must be fully specified. | |
1849 | ||
1850 | When a message crosses a domain boundary, all addresses must | |
1851 | be specified in the full format, ending with the top-level | |
1852 | name-domain in the right-most field. It is the responsibility | |
1853 | of mail forwarding services to ensure that addresses conform | |
1854 | ||
1855 | ||
1856 | August 13, 1982 - 29 - RFC #822 | |
1857 | \f | |
1858 | ||
1859 | ||
1860 | Standard for ARPA Internet Text Messages | |
1861 | ||
1862 | ||
1863 | with this requirement. In the case of abbreviated addresses, | |
1864 | the relaying service must make the necessary expansions. It | |
1865 | should be noted that it often is difficult for such a service | |
1866 | to locate all occurrences of address abbreviations. For exam- | |
1867 | ple, it will not be possible to find such abbreviations within | |
1868 | the body of the message. The "Return-Path" field can aid | |
1869 | recipients in recovering from these errors. | |
1870 | ||
1871 | Note: When passing any portion of an addr-spec onto a process | |
1872 | which does not interpret data according to this stan- | |
1873 | dard (e.g., mail protocol servers). There must be NO | |
1874 | LWSP-chars preceding or following the at-sign or any | |
1875 | delimiting period ("."), such as shown in the above | |
1876 | examples, and only ONE SPACE between contiguous | |
1877 | <word>s. | |
1878 | ||
1879 | 6.2.3. DOMAIN TERMS | |
1880 | ||
1881 | A domain-ref must be THE official name of a registry, network, | |
1882 | or host. It is a symbolic reference, within a name sub- | |
1883 | domain. At times, it is necessary to bypass standard mechan- | |
1884 | isms for resolving such references, using more primitive | |
1885 | information, such as a network host address rather than its | |
1886 | associated host name. | |
1887 | ||
1888 | To permit such references, this standard provides the domain- | |
1889 | literal construct. Its contents must conform with the needs | |
1890 | of the sub-domain in which it is interpreted. | |
1891 | ||
1892 | Domain-literals which refer to domains within the ARPA Inter- | |
1893 | net specify 32-bit Internet addresses, in four 8-bit fields | |
1894 | noted in decimal, as described in Request for Comments #820, | |
1895 | "Assigned Numbers." For example: | |
1896 | ||
1897 | [10.0.3.19] | |
1898 | ||
1899 | Note: THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED. It | |
1900 | is permitted only as a means of bypassing temporary | |
1901 | system limitations, such as name tables which are not | |
1902 | complete. | |
1903 | ||
1904 | The names of "top-level" domains, and the names of domains | |
1905 | under in the ARPA Internet, are registered with the Network | |
1906 | Information Center, SRI International, Menlo Park, California. | |
1907 | ||
1908 | 6.2.4. DOMAIN-DEPENDENT LOCAL STRING | |
1909 | ||
1910 | The local-part of an addr-spec in a mailbox specification | |
1911 | (i.e., the host's name for the mailbox) is understood to be | |
1912 | ||
1913 | ||
1914 | August 13, 1982 - 30 - RFC #822 | |
1915 | \f | |
1916 | ||
1917 | ||
1918 | Standard for ARPA Internet Text Messages | |
1919 | ||
1920 | ||
1921 | whatever the receiving mail protocol server allows. For exam- | |
1922 | ple, some systems do not understand mailbox references of the | |
1923 | form "P. D. Q. Bach", but others do. | |
1924 | ||
1925 | This specification treats periods (".") as lexical separators. | |
1926 | Hence, their presence in local-parts which are not quoted- | |
1927 | strings, is detected. However, such occurrences carry NO | |
1928 | semantics. That is, if a local-part has periods within it, an | |
1929 | address parser will divide the local-part into several tokens, | |
1930 | but the sequence of tokens will be treated as one uninter- | |
1931 | preted unit. The sequence will be re-assembled, when the | |
1932 | address is passed outside of the system such as to a mail pro- | |
1933 | tocol service. | |
1934 | ||
1935 | For example, the address: | |
1936 | ||
1937 | First.Last@Registry.Org | |
1938 | ||
1939 | is legal and does not require the local-part to be surrounded | |
1940 | with quotation-marks. (However, "First Last" DOES require | |
1941 | quoting.) The local-part of the address, when passed outside | |
1942 | of the mail system, within the Registry.Org domain, is | |
1943 | "First.Last", again without quotation marks. | |
1944 | ||
1945 | 6.2.5. BALANCING LOCAL-PART AND DOMAIN | |
1946 | ||
1947 | In some cases, the boundary between local-part and domain can | |
1948 | be flexible. The local-part may be a simple string, which is | |
1949 | used for the final determination of the recipient's mailbox. | |
1950 | All other levels of reference are, therefore, part of the | |
1951 | domain. | |
1952 | ||
1953 | For some systems, in the case of abbreviated reference to the | |
1954 | local and subordinate sub-domains, it may be possible to | |
1955 | specify only one reference within the domain part and place | |
1956 | the other, subordinate name-domain references within the | |
1957 | local-part. This would appear as: | |
1958 | ||
1959 | mailbox.sub1.sub2@this-domain | |
1960 | ||
1961 | Such a specification would be acceptable to address parsers | |
1962 | which conform to RFC #733, but do not support this newer | |
1963 | Internet standard. While contrary to the intent of this stan- | |
1964 | dard, the form is legal. | |
1965 | ||
1966 | Also, some sub-domains have a specification syntax which does | |
1967 | not conform to this standard. For example: | |
1968 | ||
1969 | sub-net.mailbox@sub-domain.domain | |
1970 | ||
1971 | ||
1972 | August 13, 1982 - 31 - RFC #822 | |
1973 | \f | |
1974 | ||
1975 | ||
1976 | Standard for ARPA Internet Text Messages | |
1977 | ||
1978 | ||
1979 | uses a different parsing sequence for local-part than for | |
1980 | domain. | |
1981 | ||
1982 | Note: As a rule, the domain specification should contain | |
1983 | fields which are encoded according to the syntax of | |
1984 | this standard and which contain generally-standardized | |
1985 | information. The local-part specification should con- | |
1986 | tain only that portion of the address which deviates | |
1987 | from the form or intention of the domain field. | |
1988 | ||
1989 | 6.2.6. MULTIPLE MAILBOXES | |
1990 | ||
1991 | An individual may have several mailboxes and wish to receive | |
1992 | mail at whatever mailbox is convenient for the sender to | |
1993 | access. This standard does not provide a means of specifying | |
1994 | "any member of" a list of mailboxes. | |
1995 | ||
1996 | A set of individuals may wish to receive mail as a single unit | |
1997 | (i.e., a distribution list). The <group> construct permits | |
1998 | specification of such a list. Recipient mailboxes are speci- | |
1999 | fied within the bracketed part (":" - ";"). A copy of the | |
2000 | transmitted message is to be sent to each mailbox listed. | |
2001 | This standard does not permit recursive specification of | |
2002 | groups within groups. | |
2003 | ||
2004 | While a list must be named, it is not required that the con- | |
2005 | tents of the list be included. In this case, the <address> | |
2006 | serves only as an indication of group distribution and would | |
2007 | appear in the form: | |
2008 | ||
2009 | name:; | |
2010 | ||
2011 | Some mail services may provide a group-list distribution | |
2012 | facility, accepting a single mailbox reference, expanding it | |
2013 | to the full distribution list, and relaying the mail to the | |
2014 | list's members. This standard provides no additional syntax | |
2015 | for indicating such a service. Using the <group> address | |
2016 | alternative, while listing one mailbox in it, can mean either | |
2017 | that the mailbox reference will be expanded to a list or that | |
2018 | there is a group with one member. | |
2019 | ||
2020 | 6.2.7. EXPLICIT PATH SPECIFICATION | |
2021 | ||
2022 | At times, a message originator may wish to indicate the | |
2023 | transmission path that a message should follow. This is | |
2024 | called source routing. The normal addressing scheme, used in | |
2025 | an addr-spec, is carefully separated from such information; | |
2026 | the <route> portion of a route-addr is provided for such occa- | |
2027 | sions. It specifies the sequence of hosts and/or transmission | |
2028 | ||
2029 | ||
2030 | August 13, 1982 - 32 - RFC #822 | |
2031 | \f | |
2032 | ||
2033 | ||
2034 | Standard for ARPA Internet Text Messages | |
2035 | ||
2036 | ||
2037 | services that are to be traversed. Both domain-refs and | |
2038 | domain-literals may be used. | |
2039 | ||
2040 | Note: The use of source routing is discouraged. Unless the | |
2041 | sender has special need of path restriction, the choice | |
2042 | of transmission route should be left to the mail tran- | |
2043 | sport service. | |
2044 | ||
2045 | 6.3. RESERVED ADDRESS | |
2046 | ||
2047 | It often is necessary to send mail to a site, without know- | |
2048 | ing any of its valid addresses. For example, there may be mail | |
2049 | system dysfunctions, or a user may wish to find out a person's | |
2050 | correct address, at that site. | |
2051 | ||
2052 | This standard specifies a single, reserved mailbox address | |
2053 | (local-part) which is to be valid at each site. Mail sent to | |
2054 | that address is to be routed to a person responsible for the | |
2055 | site's mail system or to a person with responsibility for general | |
2056 | site operation. The name of the reserved local-part address is: | |
2057 | ||
2058 | Postmaster | |
2059 | ||
2060 | so that "Postmaster@domain" is required to be valid. | |
2061 | ||
2062 | Note: This reserved local-part must be matched without sensi- | |
2063 | tivity to alphabetic case, so that "POSTMASTER", "postmas- | |
2064 | ter", and even "poStmASteR" is to be accepted. | |
2065 | ||
2066 | ||
2067 | ||
2068 | ||
2069 | ||
2070 | ||
2071 | ||
2072 | ||
2073 | ||
2074 | ||
2075 | ||
2076 | ||
2077 | ||
2078 | ||
2079 | ||
2080 | ||
2081 | ||
2082 | ||
2083 | ||
2084 | ||
2085 | ||
2086 | ||
2087 | ||
2088 | August 13, 1982 - 33 - RFC #822 | |
2089 | \f | |
2090 | ||
2091 | ||
2092 | Standard for ARPA Internet Text Messages | |
2093 | ||
2094 | ||
2095 | 7. BIBLIOGRAPHY | |
2096 | ||
2097 | ||
2098 | ANSI. "USA Standard Code for Information Interchange," X3.4. | |
2099 | American National Standards Institute: New York (1968). Also | |
2100 | in: Feinler, E. and J. Postel, eds., "ARPANET Protocol Hand- | |
2101 | book", NIC 7104. | |
2102 | ||
2103 | ANSI. "Representations of Universal Time, Local Time Differen- | |
2104 | tials, and United States Time Zone References for Information | |
2105 | Interchange," X3.51-1975. American National Standards Insti- | |
2106 | tute: New York (1975). | |
2107 | ||
2108 | Bemer, R.W., "Time and the Computer." In: Interface Age (Feb. | |
2109 | 1979). | |
2110 | ||
2111 | Bennett, C.J. "JNT Mail Protocol". Joint Network Team, Ruther- | |
2112 | ford and Appleton Laboratory: Didcot, England. | |
2113 | ||
2114 | Bhushan, A.K., Pogran, K.T., Tomlinson, R.S., and White, J.E. | |
2115 | "Standardizing Network Mail Headers," ARPANET Request for | |
2116 | Comments No. 561, Network Information Center No. 18516; SRI | |
2117 | International: Menlo Park (September 1973). | |
2118 | ||
2119 | Birrell, A.D., Levin, R., Needham, R.M., and Schroeder, M.D. | |
2120 | "Grapevine: An Exercise in Distributed Computing," Communica- | |
2121 | tions of the ACM 25, 4 (April 1982), 260-274. | |
2122 | ||
2123 | Crocker, D.H., Vittal, J.J., Pogran, K.T., Henderson, D.A. | |
2124 | "Standard for the Format of ARPA Network Text Message," | |
2125 | ARPANET Request for Comments No. 733, Network Information | |
2126 | Center No. 41952. SRI International: Menlo Park (November | |
2127 | 1977). | |
2128 | ||
2129 | Feinler, E.J. and Postel, J.B. ARPANET Protocol Handbook, Net- | |
2130 | work Information Center No. 7104 (NTIS AD A003890). SRI | |
2131 | International: Menlo Park (April 1976). | |
2132 | ||
2133 | Harary, F. "Graph Theory". Addison-Wesley: Reading, Mass. | |
2134 | (1969). | |
2135 | ||
2136 | Levin, R. and Schroeder, M. "Transport of Electronic Messages | |
2137 | through a Network," TeleInformatics 79, pp. 29-33. North | |
2138 | Holland (1979). Also as Xerox Palo Alto Research Center | |
2139 | Technical Report CSL-79-4. | |
2140 | ||
2141 | Myer, T.H. and Henderson, D.A. "Message Transmission Protocol," | |
2142 | ARPANET Request for Comments, No. 680, Network Information | |
2143 | Center No. 32116. SRI International: Menlo Park (1975). | |
2144 | ||
2145 | ||
2146 | August 13, 1982 - 34 - RFC #822 | |
2147 | \f | |
2148 | ||
2149 | ||
2150 | Standard for ARPA Internet Text Messages | |
2151 | ||
2152 | ||
2153 | NBS. "Specification of Message Format for Computer Based Message | |
2154 | Systems, Recommended Federal Information Processing Standard." | |
2155 | National Bureau of Standards: Gaithersburg, Maryland | |
2156 | (October 1981). | |
2157 | ||
2158 | NIC. Internet Protocol Transition Workbook. Network Information | |
2159 | Center, SRI-International, Menlo Park, California (March | |
2160 | 1982). | |
2161 | ||
2162 | Oppen, D.C. and Dalal, Y.K. "The Clearinghouse: A Decentralized | |
2163 | Agent for Locating Named Objects in a Distributed Environ- | |
2164 | ment," OPD-T8103. Xerox Office Products Division: Palo Alto, | |
2165 | CA. (October 1981). | |
2166 | ||
2167 | Postel, J.B. "Assigned Numbers," ARPANET Request for Comments, | |
2168 | No. 820. SRI International: Menlo Park (August 1982). | |
2169 | ||
2170 | Postel, J.B. "Simple Mail Transfer Protocol," ARPANET Request | |
2171 | for Comments, No. 821. SRI International: Menlo Park (August | |
2172 | 1982). | |
2173 | ||
2174 | Shoch, J.F. "Internetwork naming, addressing and routing," in | |
2175 | Proc. 17th IEEE Computer Society International Conference, pp. | |
2176 | 72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C. | |
2177 | ||
2178 | Su, Z. and Postel, J. "The Domain Naming Convention for Internet | |
2179 | User Applications," ARPANET Request for Comments, No. 819. | |
2180 | SRI International: Menlo Park (August 1982). | |
2181 | ||
2182 | ||
2183 | ||
2184 | ||
2185 | ||
2186 | ||
2187 | ||
2188 | ||
2189 | ||
2190 | ||
2191 | ||
2192 | ||
2193 | ||
2194 | ||
2195 | ||
2196 | ||
2197 | ||
2198 | ||
2199 | ||
2200 | ||
2201 | ||
2202 | ||
2203 | ||
2204 | August 13, 1982 - 35 - RFC #822 | |
2205 | \f | |
2206 | ||
2207 | ||
2208 | Standard for ARPA Internet Text Messages | |
2209 | ||
2210 | ||
2211 | APPENDIX | |
2212 | ||
2213 | ||
2214 | A. EXAMPLES | |
2215 | ||
2216 | A.1. ADDRESSES | |
2217 | ||
2218 | A.1.1. Alfred Neuman <Neuman@BBN-TENEXA> | |
2219 | ||
2220 | A.1.2. Neuman@BBN-TENEXA | |
2221 | ||
2222 | These two "Alfred Neuman" examples have identical seman- | |
2223 | tics, as far as the operation of the local host's mail sending | |
2224 | (distribution) program (also sometimes called its "mailer") | |
2225 | and the remote host's mail protocol server are concerned. In | |
2226 | the first example, the "Alfred Neuman" is ignored by the | |
2227 | mailer, as "Neuman@BBN-TENEXA" completely specifies the reci- | |
2228 | pient. The second example contains no superfluous informa- | |
2229 | tion, and, again, "Neuman@BBN-TENEXA" is the intended reci- | |
2230 | pient. | |
2231 | ||
2232 | Note: When the message crosses name-domain boundaries, then | |
2233 | these specifications must be changed, so as to indicate | |
2234 | the remainder of the hierarchy, starting with the top | |
2235 | level. | |
2236 | ||
2237 | A.1.3. "George, Ted" <Shared@Group.Arpanet> | |
2238 | ||
2239 | This form might be used to indicate that a single mailbox | |
2240 | is shared by several users. The quoted string is ignored by | |
2241 | the originating host's mailer, because "Shared@Group.Arpanet" | |
2242 | completely specifies the destination mailbox. | |
2243 | ||
2244 | A.1.4. Wilt . (the Stilt) Chamberlain@NBA.US | |
2245 | ||
2246 | The "(the Stilt)" is a comment, which is NOT included in | |
2247 | the destination mailbox address handed to the originating | |
2248 | system's mailer. The local-part of the address is the string | |
2249 | "Wilt.Chamberlain", with NO space between the first and second | |
2250 | words. | |
2251 | ||
2252 | A.1.5. Address Lists | |
2253 | ||
2254 | Gourmets: Pompous Person <WhoZiWhatZit@Cordon-Bleu>, | |
2255 | Childs@WGBH.Boston, Galloping Gourmet@ | |
2256 | ANT.Down-Under (Australian National Television), | |
2257 | Cheapie@Discount-Liquors;, | |
2258 | Cruisers: Port@Portugal, Jones@SEA;, | |
2259 | Another@Somewhere.SomeOrg | |
2260 | ||
2261 | ||
2262 | August 13, 1982 - 36 - RFC #822 | |
2263 | \f | |
2264 | ||
2265 | ||
2266 | Standard for ARPA Internet Text Messages | |
2267 | ||
2268 | ||
2269 | This group list example points out the use of comments and the | |
2270 | mixing of addresses and groups. | |
2271 | ||
2272 | A.2. ORIGINATOR ITEMS | |
2273 | ||
2274 | A.2.1. Author-sent | |
2275 | ||
2276 | George Jones logs into his host as "Jones". He sends | |
2277 | mail himself. | |
2278 | ||
2279 | From: Jones@Group.Org | |
2280 | ||
2281 | or | |
2282 | ||
2283 | From: George Jones <Jones@Group.Org> | |
2284 | ||
2285 | A.2.2. Secretary-sent | |
2286 | ||
2287 | George Jones logs in as Jones on his host. His secre- | |
2288 | tary, who logs in as Secy sends mail for him. Replies to the | |
2289 | mail should go to George. | |
2290 | ||
2291 | From: George Jones <Jones@Group> | |
2292 | Sender: Secy@Other-Group | |
2293 | ||
2294 | A.2.3. Secretary-sent, for user of shared directory | |
2295 | ||
2296 | George Jones' secretary sends mail for George. Replies | |
2297 | should go to George. | |
2298 | ||
2299 | From: George Jones<Shared@Group.Org> | |
2300 | Sender: Secy@Other-Group | |
2301 | ||
2302 | Note that there need not be a space between "Jones" and the | |
2303 | "<", but adding a space enhances readability (as is the case | |
2304 | in other examples. | |
2305 | ||
2306 | A.2.4. Committee activity, with one author | |
2307 | ||
2308 | George is a member of a committee. He wishes to have any | |
2309 | replies to his message go to all committee members. | |
2310 | ||
2311 | From: George Jones <Jones@Host.Net> | |
2312 | Sender: Jones@Host | |
2313 | Reply-To: The Committee: Jones@Host.Net, | |
2314 | Smith@Other.Org, | |
2315 | Doe@Somewhere-Else; | |
2316 | ||
2317 | Note that if George had not included himself in the | |
2318 | ||
2319 | ||
2320 | August 13, 1982 - 37 - RFC #822 | |
2321 | \f | |
2322 | ||
2323 | ||
2324 | Standard for ARPA Internet Text Messages | |
2325 | ||
2326 | ||
2327 | enumeration of The Committee, he would not have gotten an | |
2328 | implicit reply; the presence of the "Reply-to" field SUPER- | |
2329 | SEDES the sending of a reply to the person named in the "From" | |
2330 | field. | |
2331 | ||
2332 | A.2.5. Secretary acting as full agent of author | |
2333 | ||
2334 | George Jones asks his secretary (Secy@Host) to send a | |
2335 | message for him in his capacity as Group. He wants his secre- | |
2336 | tary to handle all replies. | |
2337 | ||
2338 | From: George Jones <Group@Host> | |
2339 | Sender: Secy@Host | |
2340 | Reply-To: Secy@Host | |
2341 | ||
2342 | A.2.6. Agent for user without online mailbox | |
2343 | ||
2344 | A friend of George's, Sarah, is visiting. George's | |
2345 | secretary sends some mail to a friend of Sarah in computer- | |
2346 | land. Replies should go to George, whose mailbox is Jones at | |
2347 | Registry. | |
2348 | ||
2349 | From: Sarah Friendly <Secy@Registry> | |
2350 | Sender: Secy-Name <Secy@Registry> | |
2351 | Reply-To: Jones@Registry. | |
2352 | ||
2353 | A.2.7. Agent for member of a committee | |
2354 | ||
2355 | George's secretary sends out a message which was authored | |
2356 | jointly by all the members of a committee. Note that the name | |
2357 | of the committee cannot be specified, since <group> names are | |
2358 | not permitted in the From field. | |
2359 | ||
2360 | From: Jones@Host, | |
2361 | Smith@Other-Host, | |
2362 | Doe@Somewhere-Else | |
2363 | Sender: Secy@SHost | |
2364 | ||
2365 | ||
2366 | ||
2367 | ||
2368 | ||
2369 | ||
2370 | ||
2371 | ||
2372 | ||
2373 | ||
2374 | ||
2375 | ||
2376 | ||
2377 | ||
2378 | August 13, 1982 - 38 - RFC #822 | |
2379 | \f | |
2380 | ||
2381 | ||
2382 | Standard for ARPA Internet Text Messages | |
2383 | ||
2384 | ||
2385 | A.3. COMPLETE HEADERS | |
2386 | ||
2387 | A.3.1. Minimum required | |
2388 | ||
2389 | Date: 26 Aug 76 1429 EDT Date: 26 Aug 76 1429 EDT | |
2390 | From: Jones@Registry.Org or From: Jones@Registry.Org | |
2391 | Bcc: To: Smith@Registry.Org | |
2392 | ||
2393 | Note that the "Bcc" field may be empty, while the "To" field | |
2394 | is required to have at least one address. | |
2395 | ||
2396 | A.3.2. Using some of the additional fields | |
2397 | ||
2398 | Date: 26 Aug 76 1430 EDT | |
2399 | From: George Jones<Group@Host> | |
2400 | Sender: Secy@SHOST | |
2401 | To: "Al Neuman"@Mad-Host, | |
2402 | Sam.Irving@Other-Host | |
2403 | Message-ID: <some.string@SHOST> | |
2404 | ||
2405 | A.3.3. About as complex as you're going to get | |
2406 | ||
2407 | Date : 27 Aug 76 0932 PDT | |
2408 | From : Ken Davis <KDavis@This-Host.This-net> | |
2409 | Subject : Re: The Syntax in the RFC | |
2410 | Sender : KSecy@Other-Host | |
2411 | Reply-To : Sam.Irving@Reg.Organization | |
2412 | To : George Jones <Group@Some-Reg.An-Org>, | |
2413 | Al.Neuman@MAD.Publisher | |
2414 | cc : Important folk: | |
2415 | Tom Softwood <Balsa@Tree.Root>, | |
2416 | "Sam Irving"@Other-Host;, | |
2417 | Standard Distribution: | |
2418 | /main/davis/people/standard@Other-Host, | |
2419 | "<Jones>standard.dist.3"@Tops-20-Host>; | |
2420 | Comment : Sam is away on business. He asked me to handle | |
2421 | his mail for him. He'll be able to provide a | |
2422 | more accurate explanation when he returns | |
2423 | next week. | |
2424 | In-Reply-To: <some.string@DBM.Group>, George's message | |
2425 | X-Special-action: This is a sample of user-defined field- | |
2426 | names. There could also be a field-name | |
2427 | "Special-action", but its name might later be | |
2428 | preempted | |
2429 | Message-ID: <4231.629.XYzi-What@Other-Host> | |
2430 | ||
2431 | ||
2432 | ||
2433 | ||
2434 | ||
2435 | ||
2436 | August 13, 1982 - 39 - RFC #822 | |
2437 | \f | |
2438 | ||
2439 | ||
2440 | Standard for ARPA Internet Text Messages | |
2441 | ||
2442 | ||
2443 | B. SIMPLE FIELD PARSING | |
2444 | ||
2445 | Some mail-reading software systems may wish to perform only | |
2446 | minimal processing, ignoring the internal syntax of structured | |
2447 | field-bodies and treating them the same as unstructured-field- | |
2448 | bodies. Such software will need only to distinguish: | |
2449 | ||
2450 | o Header fields from the message body, | |
2451 | ||
2452 | o Beginnings of fields from lines which continue fields, | |
2453 | ||
2454 | o Field-names from field-contents. | |
2455 | ||
2456 | The abbreviated set of syntactic rules which follows will | |
2457 | suffice for this purpose. It describes a limited view of mes- | |
2458 | sages and is a subset of the syntactic rules provided in the main | |
2459 | part of this specification. One small exception is that the con- | |
2460 | tents of field-bodies consist only of text: | |
2461 | ||
2462 | B.1. SYNTAX | |
2463 | ||
2464 | ||
2465 | message = *field *(CRLF *text) | |
2466 | ||
2467 | field = field-name ":" [field-body] CRLF | |
2468 | ||
2469 | field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":"> | |
2470 | ||
2471 | field-body = *text [CRLF LWSP-char field-body] | |
2472 | ||
2473 | ||
2474 | B.2. SEMANTICS | |
2475 | ||
2476 | Headers occur before the message body and are terminated by | |
2477 | a null line (i.e., two contiguous CRLFs). | |
2478 | ||
2479 | A line which continues a header field begins with a SPACE or | |
2480 | HTAB character, while a line beginning a field starts with a | |
2481 | printable character which is not a colon. | |
2482 | ||
2483 | A field-name consists of one or more printable characters | |
2484 | (excluding colon, space, and control-characters). A field-name | |
2485 | MUST be contained on one line. Upper and lower case are not dis- | |
2486 | tinguished when comparing field-names. | |
2487 | ||
2488 | ||
2489 | ||
2490 | ||
2491 | ||
2492 | ||
2493 | ||
2494 | August 13, 1982 - 40 - RFC #822 | |
2495 | \f | |
2496 | ||
2497 | ||
2498 | Standard for ARPA Internet Text Messages | |
2499 | ||
2500 | ||
2501 | C. DIFFERENCES FROM RFC #733 | |
2502 | ||
2503 | The following summarizes the differences between this stan- | |
2504 | dard and the one specified in Arpanet Request for Comments #733, | |
2505 | "Standard for the Format of ARPA Network Text Messages". The | |
2506 | differences are listed in the order of their occurrence in the | |
2507 | current specification. | |
2508 | ||
2509 | C.1. FIELD DEFINITIONS | |
2510 | ||
2511 | C.1.1. FIELD NAMES | |
2512 | ||
2513 | These now must be a sequence of printable characters. They | |
2514 | may not contain any LWSP-chars. | |
2515 | ||
2516 | C.2. LEXICAL TOKENS | |
2517 | ||
2518 | C.2.1. SPECIALS | |
2519 | ||
2520 | The characters period ("."), left-square bracket ("["), and | |
2521 | right-square bracket ("]") have been added. For presentation | |
2522 | purposes, and when passing a specification to a system that | |
2523 | does not conform to this standard, periods are to be contigu- | |
2524 | ous with their surrounding lexical tokens. No linear-white- | |
2525 | space is permitted between them. The presence of one LWSP- | |
2526 | char between other tokens is still directed. | |
2527 | ||
2528 | C.2.2. ATOM | |
2529 | ||
2530 | Atoms may not contain SPACE. | |
2531 | ||
2532 | C.2.3. SPECIAL TEXT | |
2533 | ||
2534 | ctext and qtext have had backslash ("\") added to the list of | |
2535 | prohibited characters. | |
2536 | ||
2537 | C.2.4. DOMAINS | |
2538 | ||
2539 | The lexical tokens <domain-literal> and <dtext> have been | |
2540 | added. | |
2541 | ||
2542 | C.3. MESSAGE SPECIFICATION | |
2543 | ||
2544 | C.3.1. TRACE | |
2545 | ||
2546 | The "Return-path:" and "Received:" fields have been specified. | |
2547 | ||
2548 | ||
2549 | ||
2550 | ||
2551 | ||
2552 | August 13, 1982 - 41 - RFC #822 | |
2553 | \f | |
2554 | ||
2555 | ||
2556 | Standard for ARPA Internet Text Messages | |
2557 | ||
2558 | ||
2559 | C.3.2. FROM | |
2560 | ||
2561 | The "From" field must contain machine-usable addresses (addr- | |
2562 | spec). Multiple addresses may be specified, but named-lists | |
2563 | (groups) may not. | |
2564 | ||
2565 | C.3.3. RESENT | |
2566 | ||
2567 | The meta-construct of prefacing field names with the string | |
2568 | "Resent-" has been added, to indicate that a message has been | |
2569 | forwarded by an intermediate recipient. | |
2570 | ||
2571 | C.3.4. DESTINATION | |
2572 | ||
2573 | A message must contain at least one destination address field. | |
2574 | "To" and "CC" are required to contain at least one address. | |
2575 | ||
2576 | C.3.5. IN-REPLY-TO | |
2577 | ||
2578 | The field-body is no longer a comma-separated list, although a | |
2579 | sequence is still permitted. | |
2580 | ||
2581 | C.3.6. REFERENCE | |
2582 | ||
2583 | The field-body is no longer a comma-separated list, although a | |
2584 | sequence is still permitted. | |
2585 | ||
2586 | C.3.7. ENCRYPTED | |
2587 | ||
2588 | A field has been specified that permits senders to indicate | |
2589 | that the body of a message has been encrypted. | |
2590 | ||
2591 | C.3.8. EXTENSION-FIELD | |
2592 | ||
2593 | Extension fields are prohibited from beginning with the char- | |
2594 | acters "X-". | |
2595 | ||
2596 | C.4. DATE AND TIME SPECIFICATION | |
2597 | ||
2598 | C.4.1. SIMPLIFICATION | |
2599 | ||
2600 | Fewer optional forms are permitted and the list of three- | |
2601 | letter time zones has been shortened. | |
2602 | ||
2603 | C.5. ADDRESS SPECIFICATION | |
2604 | ||
2605 | ||
2606 | ||
2607 | ||
2608 | ||
2609 | ||
2610 | August 13, 1982 - 42 - RFC #822 | |
2611 | \f | |
2612 | ||
2613 | ||
2614 | Standard for ARPA Internet Text Messages | |
2615 | ||
2616 | ||
2617 | C.5.1. ADDRESS | |
2618 | ||
2619 | The use of quoted-string, and the ":"-atom-":" construct, have | |
2620 | been removed. An address now is either a single mailbox | |
2621 | reference or is a named list of addresses. The latter indi- | |
2622 | cates a group distribution. | |
2623 | ||
2624 | C.5.2. GROUPS | |
2625 | ||
2626 | Group lists are now required to to have a name. Group lists | |
2627 | may not be nested. | |
2628 | ||
2629 | C.5.3. MAILBOX | |
2630 | ||
2631 | A mailbox specification may indicate a person's name, as | |
2632 | before. Such a named list no longer may specify multiple | |
2633 | mailboxes and may not be nested. | |
2634 | ||
2635 | C.5.4. ROUTE ADDRESSING | |
2636 | ||
2637 | Addresses now are taken to be absolute, global specifications, | |
2638 | independent of transmission paths. The <route> construct has | |
2639 | been provided, to permit explicit specification of transmis- | |
2640 | sion path. RFC #733's use of multiple at-signs ("@") was | |
2641 | intended as a general syntax for indicating routing and/or | |
2642 | hierarchical addressing. The current standard separates these | |
2643 | specifications and only one at-sign is permitted. | |
2644 | ||
2645 | C.5.5. AT-SIGN | |
2646 | ||
2647 | The string " at " no longer is used as an address delimiter. | |
2648 | Only at-sign ("@") serves the function. | |
2649 | ||
2650 | C.5.6. DOMAINS | |
2651 | ||
2652 | Hierarchical, logical name-domains have been added. | |
2653 | ||
2654 | C.6. RESERVED ADDRESS | |
2655 | ||
2656 | The local-part "Postmaster" has been reserved, so that users can | |
2657 | be guaranteed at least one valid address at a site. | |
2658 | ||
2659 | ||
2660 | ||
2661 | ||
2662 | ||
2663 | ||
2664 | ||
2665 | ||
2666 | ||
2667 | ||
2668 | August 13, 1982 - 43 - RFC #822 | |
2669 | \f | |
2670 | ||
2671 | ||
2672 | Standard for ARPA Internet Text Messages | |
2673 | ||
2674 | ||
2675 | D. ALPHABETICAL LISTING OF SYNTAX RULES | |
2676 | ||
2677 | address = mailbox ; one addressee | |
2678 | / group ; named list | |
2679 | addr-spec = local-part "@" domain ; global address | |
2680 | ALPHA = <any ASCII alphabetic character> | |
2681 | ; (101-132, 65.- 90.) | |
2682 | ; (141-172, 97.-122.) | |
2683 | atom = 1*<any CHAR except specials, SPACE and CTLs> | |
2684 | authentic = "From" ":" mailbox ; Single author | |
2685 | / ( "Sender" ":" mailbox ; Actual submittor | |
2686 | "From" ":" 1#mailbox) ; Multiple authors | |
2687 | ; or not sender | |
2688 | CHAR = <any ASCII character> ; ( 0-177, 0.-127.) | |
2689 | comment = "(" *(ctext / quoted-pair / comment) ")" | |
2690 | CR = <ASCII CR, carriage return> ; ( 15, 13.) | |
2691 | CRLF = CR LF | |
2692 | ctext = <any CHAR excluding "(", ; => may be folded | |
2693 | ")", "\" & CR, & including | |
2694 | linear-white-space> | |
2695 | CTL = <any ASCII control ; ( 0- 37, 0.- 31.) | |
2696 | character and DEL> ; ( 177, 127.) | |
2697 | date = 1*2DIGIT month 2DIGIT ; day month year | |
2698 | ; e.g. 20 Jun 82 | |
2699 | dates = orig-date ; Original | |
2700 | [ resent-date ] ; Forwarded | |
2701 | date-time = [ day "," ] date time ; dd mm yy | |
2702 | ; hh:mm:ss zzz | |
2703 | day = "Mon" / "Tue" / "Wed" / "Thu" | |
2704 | / "Fri" / "Sat" / "Sun" | |
2705 | delimiters = specials / linear-white-space / comment | |
2706 | destination = "To" ":" 1#address ; Primary | |
2707 | / "Resent-To" ":" 1#address | |
2708 | / "cc" ":" 1#address ; Secondary | |
2709 | / "Resent-cc" ":" 1#address | |
2710 | / "bcc" ":" #address ; Blind carbon | |
2711 | / "Resent-bcc" ":" #address | |
2712 | DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.) | |
2713 | domain = sub-domain *("." sub-domain) | |
2714 | domain-literal = "[" *(dtext / quoted-pair) "]" | |
2715 | domain-ref = atom ; symbolic reference | |
2716 | dtext = <any CHAR excluding "[", ; => may be folded | |
2717 | "]", "\" & CR, & including | |
2718 | linear-white-space> | |
2719 | extension-field = | |
2720 | <Any field which is defined in a document | |
2721 | published as a formal extension to this | |
2722 | specification; none will have names beginning | |
2723 | with the string "X-"> | |
2724 | ||
2725 | ||
2726 | August 13, 1982 - 44 - RFC #822 | |
2727 | \f | |
2728 | ||
2729 | ||
2730 | Standard for ARPA Internet Text Messages | |
2731 | ||
2732 | ||
2733 | field = field-name ":" [ field-body ] CRLF | |
2734 | fields = dates ; Creation time, | |
2735 | source ; author id & one | |
2736 | 1*destination ; address required | |
2737 | *optional-field ; others optional | |
2738 | field-body = field-body-contents | |
2739 | [CRLF LWSP-char field-body] | |
2740 | field-body-contents = | |
2741 | <the ASCII characters making up the field-body, as | |
2742 | defined in the following sections, and consisting | |
2743 | of combinations of atom, quoted-string, and | |
2744 | specials tokens, or else consisting of texts> | |
2745 | field-name = 1*<any CHAR, excluding CTLs, SPACE, and ":"> | |
2746 | group = phrase ":" [#mailbox] ";" | |
2747 | hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT] | |
2748 | ; 00:00:00 - 23:59:59 | |
2749 | HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.) | |
2750 | LF = <ASCII LF, linefeed> ; ( 12, 10.) | |
2751 | linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE | |
2752 | ; CRLF => folding | |
2753 | local-part = word *("." word) ; uninterpreted | |
2754 | ; case-preserved | |
2755 | LWSP-char = SPACE / HTAB ; semantics = SPACE | |
2756 | mailbox = addr-spec ; simple address | |
2757 | / phrase route-addr ; name & addr-spec | |
2758 | message = fields *( CRLF *text ) ; Everything after | |
2759 | ; first null line | |
2760 | ; is message body | |
2761 | month = "Jan" / "Feb" / "Mar" / "Apr" | |
2762 | / "May" / "Jun" / "Jul" / "Aug" | |
2763 | / "Sep" / "Oct" / "Nov" / "Dec" | |
2764 | msg-id = "<" addr-spec ">" ; Unique message id | |
2765 | optional-field = | |
2766 | / "Message-ID" ":" msg-id | |
2767 | / "Resent-Message-ID" ":" msg-id | |
2768 | / "In-Reply-To" ":" *(phrase / msg-id) | |
2769 | / "References" ":" *(phrase / msg-id) | |
2770 | / "Keywords" ":" #phrase | |
2771 | / "Subject" ":" *text | |
2772 | / "Comments" ":" *text | |
2773 | / "Encrypted" ":" 1#2word | |
2774 | / extension-field ; To be defined | |
2775 | / user-defined-field ; May be pre-empted | |
2776 | orig-date = "Date" ":" date-time | |
2777 | originator = authentic ; authenticated addr | |
2778 | [ "Reply-To" ":" 1#address] ) | |
2779 | phrase = 1*word ; Sequence of words | |
2780 | ||
2781 | ||
2782 | ||
2783 | ||
2784 | August 13, 1982 - 45 - RFC #822 | |
2785 | \f | |
2786 | ||
2787 | ||
2788 | Standard for ARPA Internet Text Messages | |
2789 | ||
2790 | ||
2791 | qtext = <any CHAR excepting <">, ; => may be folded | |
2792 | "\" & CR, and including | |
2793 | linear-white-space> | |
2794 | quoted-pair = "\" CHAR ; may quote any char | |
2795 | quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or | |
2796 | ; quoted chars. | |
2797 | received = "Received" ":" ; one per relay | |
2798 | ["from" domain] ; sending host | |
2799 | ["by" domain] ; receiving host | |
2800 | ["via" atom] ; physical path | |
2801 | *("with" atom) ; link/mail protocol | |
2802 | ["id" msg-id] ; receiver msg id | |
2803 | ["for" addr-spec] ; initial form | |
2804 | ";" date-time ; time received | |
2805 | ||
2806 | resent = resent-authentic | |
2807 | [ "Resent-Reply-To" ":" 1#address] ) | |
2808 | resent-authentic = | |
2809 | = "Resent-From" ":" mailbox | |
2810 | / ( "Resent-Sender" ":" mailbox | |
2811 | "Resent-From" ":" 1#mailbox ) | |
2812 | resent-date = "Resent-Date" ":" date-time | |
2813 | return = "Return-path" ":" route-addr ; return address | |
2814 | route = 1#("@" domain) ":" ; path-relative | |
2815 | route-addr = "<" [route] addr-spec ">" | |
2816 | source = [ trace ] ; net traversals | |
2817 | originator ; original mail | |
2818 | [ resent ] ; forwarded | |
2819 | SPACE = <ASCII SP, space> ; ( 40, 32.) | |
2820 | specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted- | |
2821 | / "," / ";" / ":" / "\" / <"> ; string, to use | |
2822 | / "." / "[" / "]" ; within a word. | |
2823 | sub-domain = domain-ref / domain-literal | |
2824 | text = <any CHAR, including bare ; => atoms, specials, | |
2825 | CR & bare LF, but NOT ; comments and | |
2826 | including CRLF> ; quoted-strings are | |
2827 | ; NOT recognized. | |
2828 | time = hour zone ; ANSI and Military | |
2829 | trace = return ; path to sender | |
2830 | 1*received ; receipt tags | |
2831 | user-defined-field = | |
2832 | <Any field which has not been defined | |
2833 | in this specification or published as an | |
2834 | extension to this specification; names for | |
2835 | such fields must be unique and may be | |
2836 | pre-empted by published extensions> | |
2837 | word = atom / quoted-string | |
2838 | ||
2839 | ||
2840 | ||
2841 | ||
2842 | August 13, 1982 - 46 - RFC #822 | |
2843 | \f | |
2844 | ||
2845 | ||
2846 | Standard for ARPA Internet Text Messages | |
2847 | ||
2848 | ||
2849 | zone = "UT" / "GMT" ; Universal Time | |
2850 | ; North American : UT | |
2851 | / "EST" / "EDT" ; Eastern: - 5/ - 4 | |
2852 | / "CST" / "CDT" ; Central: - 6/ - 5 | |
2853 | / "MST" / "MDT" ; Mountain: - 7/ - 6 | |
2854 | / "PST" / "PDT" ; Pacific: - 8/ - 7 | |
2855 | / 1ALPHA ; Military: Z = UT; | |
2856 | <"> = <ASCII quote mark> ; ( 42, 34.) | |
2857 | ||
2858 | ||
2859 | ||
2860 | ||
2861 | ||
2862 | ||
2863 | ||
2864 | ||
2865 | ||
2866 | ||
2867 | ||
2868 | ||
2869 | ||
2870 | ||
2871 | ||
2872 | ||
2873 | ||
2874 | ||
2875 | ||
2876 | ||
2877 | ||
2878 | ||
2879 | ||
2880 | ||
2881 | ||
2882 | ||
2883 | ||
2884 | ||
2885 | ||
2886 | ||
2887 | ||
2888 | ||
2889 | ||
2890 | ||
2891 | ||
2892 | ||
2893 | ||
2894 | ||
2895 | ||
2896 | ||
2897 | ||
2898 | ||
2899 | ||
2900 | August 13, 1982 - 47 - RFC #822 | |
2901 |