| 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 | |