idnits 2.17.1 draft-palme-mailext-headers-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** Looks like you're using RFC 2026 boilerplate. This must be updated to follow RFC 3978/3979, as updated by RFC 4748. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- ** The document is more than 15 pages and seems to lack a Table of Contents. == There are 2 instances of lines with non-ascii characters in the document. == The page length should not exceed 58 lines per page, but there was 1 longer page, the longest (page 1) being 2121 lines Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a Security Considerations section. ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) ** The document seems to lack separate sections for Informative/Normative References. All references will be assumed normative when checking for downward references. ** The abstract seems to contain references ([28]), which it shouldn't. Please replace those with straight textual mentions of the documents in question. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year == Line 318 has weird spacing: '...osition expe...' == Line 408 has weird spacing: '...tion on n: ...' == Line 436 has weird spacing: '...ate the or ...' == Line 445 has weird spacing: '...l being follo...' == Line 686 has weird spacing: '...cations readi...' == (1 more instance...) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (September 2002) is 7887 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Missing reference section? '28' on line 1629 looks like a reference -- Missing reference section? '21' on line 1762 looks like a reference -- Missing reference section? '2' on line 1493 looks like a reference -- Missing reference section? '3' on line 1496 looks like a reference -- Missing reference section? '5' on line 1511 looks like a reference -- Missing reference section? '7' on line 1520 looks like a reference -- Missing reference section? '8' on line 1524 looks like a reference -- Missing reference section? '11' on line 1539 looks like a reference -- Missing reference section? '12' on line 1545 looks like a reference -- Missing reference section? '14' on line 1554 looks like a reference -- Missing reference section? '17' on line 1569 looks like a reference -- Missing reference section? '20' on line 1588 looks like a reference -- Missing reference section? '16' on line 1564 looks like a reference -- Missing reference section? '1' on line 1490 looks like a reference -- Missing reference section? '18' on line 1573 looks like a reference -- Missing reference section? '15' on line 1559 looks like a reference -- Missing reference section? '19' on line 1584 looks like a reference -- Missing reference section? '25' on line 1610 looks like a reference -- Missing reference section? '23' on line 1603 looks like a reference -- Missing reference section? '24' on line 1607 looks like a reference -- Missing reference section? '27' on line 1624 looks like a reference -- Missing reference section? '26' on line 1614 looks like a reference -- Missing reference section? '13' on line 1550 looks like a reference -- Missing reference section? '4' on line 1507 looks like a reference -- Missing reference section? '6' on line 1516 looks like a reference -- Missing reference section? '9' on line 1530 looks like a reference -- Missing reference section? '10' on line 1534 looks like a reference Summary: 6 errors (**), 0 flaws (~~), 9 warnings (==), 29 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Jacob Palme 2 Internet Draft Stockholm 3 draft-palme-mailext-headers-08.txt University/KTH 4 Category: Informational Sweden 5 Revision of: RFC 2076 Date: September 2002 6 Expires: March 2003 8 Common Internet Message Header Fields 10 Status of this Memo 12 This document is an Internet-Draft and is in full 13 conformance with all provisions of Section 10 of RFC2026. 15 Internet-Drafts are working documents of the Internet 16 Engineering Task Force (IETF), its areas, and its working 17 groups. Note that other groups may also distribute working 18 documents as Internet-Drafts. 20 Internet-Drafts are draft documents valid for a maximum of 21 six months and may be updated, replaced, or obsoleted by 22 other documents at any time. It is inappropriate to use 23 Internet-Drafts as reference material or to cite them other 24 than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt 29 The list of Internet-Draft Shadow Directories can be 30 accessed at 31 http://www.ietf.org/shadow.html. 33 Copyright (C) The Internet Society 2001. All 34 Rights Reserved. 36 Abstract 38 This memo contains tables of commonly occurring header 39 fields in headings of e-mail messages. The document 40 compiles information from other RFCs such as RFC 2822, RFC 41 1036, RFC 1123, RFC 2156, RFC 1496, RFC 1766, RFC 2183, RFC 42 1864, RFC 2421 and RFC 2045. A few commonly occurring 43 header fields which are not defined in RFCs are also 44 included. For each header field, the memo gives a short 45 description and a reference to the RFC in which the header 46 field is defined. 48 The latest, revised version of this document can be found 49 at URL 50 http://www.dsv.su.se/jpalme/ietf/mail-headers/. The version 51 at that 52 URL may be more recent than the version published as an 53 RFC. 55 Another list of headers can be found at URL 56 http://www.cs.tut.fi/~jkorpela/headers.html [28] 58 Changes since previous draft: 60 Corrected misspelling of "Abouse" should be "Abuse" and 61 "Register-Mail-Reply-Requested-By" should be "Registered- 62 Mail-Reply-Requested-By". Added some RFC references. Added 63 some more warnings concerning "Precedence". 65 Table of contents 67 Abstract 68 1. Introduction 69 2. Use of gatewaying header fields 70 3. Table of header fields 71 **** 3.1 Phrases used in the tables 72 **** 3.2 Trace information 73 **** 3.3 Format and control information 74 **** 3.4 Sender and recipient indication 75 **** 3.5 Response control 76 **** 3.6 Message identification and referral 77 header fields 78 **** 3.7 Other textual header fields 79 **** 3.8 Header fields containing dates and 80 times 81 **** 3.9 Quality information 82 **** 3.10 Language information 83 **** 3.11 Size information 84 **** 3.12 Conversion control 85 **** 3.13 Encoding information 86 **** 3.14 Resent-header fields 87 **** 3.15 Security and reliability 88 **** 3.16 Mailing list control 89 **** 3.17 Miscellaneous 90 4. Acknowledgments 91 Copyright and disclaimer 92 5. References 93 6. Author's address 94 Appendix A: 95 Header fields sorted by Internet RFC document in 96 which they appear. 97 RFC 976 98 RFC 1049 99 RFC 1036 100 RFC 1123 101 RFC 1505 102 RFC 1766 103 RFC 1864 104 RFC 2045 105 RFC 2110 106 RFC 2156 107 RFC 2183 108 RFC 2298 109 RFC 2369 110 RFC 2421 111 son-of-RFC1036 [21] 112 RFC 2822 113 RFC 2912 114 RFC 2919: 115 World Wide Web Consortium (W3C) Recommendations 116 Not Internet standard (as of May 2001) 117 Appendix B: Alphabetical index 119 1. Introduction 121 Many different Internet standards and RFCs define header 122 fields which may occur on Internet Mail Messages and Usenet 123 News Articles. The intention of this document is to list 124 all such header fields in one document as an aid to people 125 developing message systems or interested in Internet Mail 126 standards. 128 The document contains all header fields which the author 129 has found in the following Internet standards: RFC 2822 130 [2], RFC 1036 [3], RFC 1123 [5], RFC 2156 [7], RFC 1496 131 [8], RFC 2045 [11], RFC 1766 [12], RFC 2183 [14], RFC 132 1864[17] and RFC 2421[20]. Note in particular that heading 133 attributes defined in PEM (RFC 1421-1424) and MOSS (RFC 134 1848 [16]) are not included. PEM and MOSS header fields 135 only appear inside the body of a message, and thus are not 136 header fields in the RFC 2822 sense. Mail attributes in 137 envelopes, i.e. attributes controlling the message 138 transport mechanism between mail and news servers, are not 139 included. This means that attributes from SMTP [1], UUCP 140 [18] and NNTP [15] are mainly not covered either. Headings 141 used only in HTTP [19] are not included yet, but may be 142 included in future version of this memo. Some additional 143 header fields which often can be found in e-mail headings 144 but are not part of any Internet standard are also 145 included. 147 The author does not promise that this document contains a 148 complete list of all heading fields which are specified in 149 any standard or used by any mailer. 151 For each header field, the document gives a short 152 description and a reference to the Internet standard or 153 RFC, in which they are defined. 155 The header field names given here are spelled the same way 156 as when they are actually used. This is usually American 157 but sometimes English spelling. One header field in 158 particular, "Organisation/Organization", occurs in e-mail 159 header fields sometimes with the English and other times 160 with the American spelling. 162 The following words are used in this memo with the meaning 163 specified below: 165 heading Formatted text at the top of a message, 166 ended by a blank line 168 header field One field in the heading, beginning with a 169 field name, colon, and followed by the 170 field value(s). The words "heading field" 171 and "header" are also sometimes used with 172 this meaning. 174 It is my intention to continue updating this document after 175 its publication as an RFC. The latest version, which may be 176 more up-to-date (but also less fully checked out) will be 177 kept available for downloading from URL 178 http://www.dsv.su.se/jpalme/ietf/mail-headers/ 180 Please e-mail me (Jacob Palme ) if you 181 have noted header fields which should be included in this 182 memo but are not. 184 2. Use of gatewaying header fields 186 RFC 2156 defines a number of new header fields in Internet 187 mail, which are defined to map header fields which X.400 188 has but which were previously not standardized in Internet 189 mail. The fact that a header field occurs in RFC 2156 190 indicates that it is recommended for use in gatewaying 191 messages between X.400 and Internet mail, but does not mean 192 that the header field is recommended for messages wholly 193 within Internet mail. Some of these header fields may 194 eventually see widespread implementation and use in 195 Internet mail, but at the time of this writing (2002) they 196 are not widely implemented or used. 198 Header fields defined only in RFC 1036 for use in Usenet 199 News sometimes appear in mail messages, either because the 200 messages have been gatewayed from Usenet News to e-mail, or 201 because the messages were written in combined clients 202 supporting both e-mail and Usenet News in the same client. 203 These header fields are not standardized for use in 204 Internet e-mail and should be handled with caution by e- 205 mail agents. 207 3. Table of header fields 209 **** 3.1 Phrases used in the tables 211 "not for general Used to mark header fields which are 212 usage" defined in RFC 2156 for use in 213 messages from or to Internet 214 mail/X.400 gateways. These header 215 fields have not been standardized for 216 general usage in the exchange of 217 messages between Internet mail-based 218 systems. 220 "not standardized Used to mark header fields defined 221 for use in e- only in RFC 1036 for use in Usenet 222 mail" News. These header fields have no 223 standard meaning when appearing in e- 224 mail, some of them may even be used in 225 different ways by different software. 226 When appearing in e-mail, they should 227 be handled with caution. Note that RFC 228 1036, although generally used as a de- 229 facto standard for Usenet News, is not 230 an official IETF standard or even on 231 the IETF standards track. 233 "non-standard" This header field is not specified in 234 any of referenced RFCs which define 235 Internet protocols, including Internet 236 Standards, draft standards or proposed 237 standards. The header field appears 238 here because it often appears in e- 239 mail or Usenet News. Usage of these 240 header fields is not in general 241 recommended. Some header field 242 proposed in ongoing IETF standards 243 development work, but not yet 244 accepted, are also marked in this way. 246 "discouraged" This header field, which is non- 247 standard, is known to create problems 248 and should not be generated. Handling 249 of such header fields in incoming mail 250 should be done with great caution. 252 "controversial" The meaning and usage of this header 253 field is controversial, i.e. different 254 implementors have chosen to implement 255 the header field in different ways. 256 Because of this, such header fields 257 should be handled with caution and 258 understanding of the different 259 possible interpretations. 261 "experimental" This header field is used for newly 262 defined header fields, which are to be 263 tried out before entering the IETF 264 standards track. These should only be 265 used if both communicating parties 266 agree on using them. In practice, some 267 experimental protocols become de-facto- 268 standards before they are made into 269 IETF standards. 271 **** 3.2 Trace information 273 Trace of distribution lists DL- RFC 2156, not 274 passed. Expansion- for general 275 History: usage. 277 List of MTAs passed. Path: RFC 1036: 278 2.1.6, only in 279 Usenet News, 280 not in e-mail. 282 Trace of MTAs which a Received: RFC 2822: RFC 283 message has passed. 1123: 5.2.8. 285 Used to convey the Return- RFC 821, 286 information from the MAIL Path: RFC 1123: 287 FROM envelope attribute in 5.2.13. 288 final delivery, when the 289 message leaves the SMTP 290 environment in which "MAIL 291 FROM" is used. 293 The netnews host, to which NNTP- Non-standard, 294 this article was originally Posting- common in 295 posted. Useful for finding Host: netnews 296 the sender of spams. Since 297 this header is added by the 298 news server, it is a little 299 more difficult to forge than 300 other header fields. 302 **** 3.3 Format and control information 304 Special Usenet News commands Also- son-of-RFC1036 305 and a normal article at the Control: [21], non- 306 same time. standard, only 307 in Usenet News, 308 not in e-mail 310 Controls whether this Alternate- RFC 2156, not 311 message may be forwarded to Recipient: for general 312 alternate recipients such as usage. 313 a postmaster if delivery is 314 not possible to the intended 315 recipient. Default: Allowed. 317 Whether a MIME body part is Content- RFC 2183, 318 to be shown inline or is an Disposition experimental 319 attachment; can also : 320 indicate a suggested 321 filename for use when saving 322 an attachment to a file. 324 Can have the values "voice- Message- Non-standard 325 message", "fax-message", Context: 326 "pager-message", "multimedia- 327 message", "text-message", 328 "none" 330 Only in Usenet News, Control: RFC 1036: 331 contains commands to be 2.1.6, only in 332 performed by News agents. Usenet News, 333 not in e-mail. 335 Whether recipients are to be Disclose- RFC 2156, not 336 told the names of other Recipients: for general 337 recipients of the same usage. 338 message. This is primarily 339 an X.400 facility. In X.400, 340 this is an envelope 341 attribute and refers to 342 disclosure of the envelope 343 recipient list. Disclosure 344 of other recipients is in 345 Internet mail done via the 346 To:, cc: and bcc: header 347 fields. 349 An indicator that this MIME- RFC 2045: 4. 350 message is formatted Version: 351 according to the MIME 352 standard, and an indication 353 of which version of MIME is 354 utilized. 356 Which body part types occur Original- RFC 2156, not 357 in this message. Encoded- for general 358 Information- usage. 359 Types: 361 **** 3.4 Sender and recipient indication 363 Inserted by Sendmail when Apparently- Non-standard, 364 there is no "To:" recipient To: discouraged, 365 in the original message, mentioned in 366 listing recipients derived RFC 1211. 367 from the envelope into the 368 message heading. This 369 behavior is not quite 370 proper, MTAs should not 371 modify headings (except 372 inserting Received lines), 373 and it can in some cases 374 cause Bcc recipients to be 375 wrongly divulged to non-Bcc 376 recipients. 378 Name of the moderator of the Approved: RFC 1036: 379 newsgroup to which this 2.2.11, not 380 article is sent; necessary standardized 381 on an article sent to a for use in e- 382 moderated newsgroup to allow mail. 383 its distribution to the 384 newsgroup members. Also used 385 on certain control messages, 386 which are only performed if 387 they are marked as Approved. 389 Name of the moderator of a Approved- Non-standard, 390 mailing list, and who has By: used by some 391 approved this message for mailing list 392 distribution to the members expansion 393 of the list. systems. 395 Recipients not to be bcc: RFC 2822:, 396 disclosed to other RFC 1123: 397 recipients. (bcc = Blind 5.2.15-16, 398 Carbon Copy). 5.3.7, 399 RFC 2156, RFC 400 2532, RFC 3297. 402 Secondary, informational cc: RFC 2822:, 403 recipients. (cc = Carbon RFC 1123. 404 Copy) 5.2.15-16, 405 5.3.7. 407 Geographical or Distributio RFC 1036: 408 organizational limitation on n: 2.2.7, not 409 where this article can be standardized 410 distributed. Value can be a for use in e- 411 compete or incomplete domain mail. 412 names, also various special 413 values are accepted like 414 "world", "usenet", "USA", 415 etc. 417 Fax number of the Fax:, Non-standard. 418 originator. Telefax: 420 Primary recipients, who are For- Non-standard 421 requested to approve the Approval: 422 information in this message 423 or its attachments. 425 Primary recipients, who are For- Non-standard 426 requested to comment on the Comment: 427 information in this message 428 or its attachments. 430 Primary recipients, who are For- Non-standard 431 requested to handle the Handling: 432 information in this message 433 or its attachments. 435 (2) Used in Usenet News mail From RFC 976: 2.4 436 transport, to indicate the or for use in 437 path through which an >From Usenet News 438 article has gone when (not 439 transferred to a new host. followed by 440 a colon) 441 Sometimes called "From_" 442 header field. 444 (1) This header field should From (not not 445 never appear in e-mail being followed by standardized 446 sent, and should thus not a colon) for use in e- 447 appear in this memo. It is mail 448 however included, since 449 people often ask about it. 451 This header field is used in 452 the so-called Unix mailbox 453 format, also known as 454 Berkely mailbox format or 455 the MBOX format. This is a 456 format for storing a set of 457 messages in a file. A line 458 beginning with "From " is 459 used to separate successive 460 messages in such files. 462 This header field will thus 463 appear when you use a text 464 editor to look at a file in 465 the Unix mailbox format. 466 Some mailers also use this 467 format when printing 468 messages on paper. 470 The information in this 471 header field should NOT be 472 used to find an address to 473 which replies to a message 474 are to be sent. 476 Authors or persons taking From: RFC 2822:, 477 responsibility for the RFC 1123: 478 message. 5.2.15-16, 479 5.3.7, 480 Note difference from the RFC 1036 2.1.1 481 "From " header field (not 482 followed by ":") below. 484 Information about the client Mail-System- Non-standard. 485 software of the originator. Version:, 486 Mailer:, 487 Originating- 488 Client:, X- 489 Mailer, X- 490 Newsreader, 491 X-MimeOLE:, 492 User-Agent: 494 In Usenet News: group(s) to Newsgroups: RFC 1036: 495 which this article was 2.1.3, not 496 posted. standardized 497 Some systems provide this and 498 header field also in e-mail controversial 499 although it is not for use in e- 500 standardized there. mail. 502 Unfortunately, the header 503 field can appear in e-mail 504 with three different and 505 contradictory meanings: 507 (a) Indicating the newsgroup 508 recipient of an 509 article/message sent to both 510 e-mail and Usenet News 511 recipients. 513 (b) In a message adressed to 514 some mail to news gateways, 515 indicates the newsgroup(s) 516 that the message is to be 517 posted to. 519 (c) In a personally 520 addressed reply to an 521 article in a news-group, 522 indicating the newsgroup in 523 which this discussion 524 originated. 526 See also: "Posted-To:". 528 Sometimes used in Usenet Originator: Non-standard in 529 News in similar ways to Usenet News, 530 "Sender:" Experimental in 531 RFC 1528. 532 Also used in printing 533 protocols. 535 Contains information about Originator- Non-standard 536 the authentication of the Info: [25] 537 originator in a format which 538 is not easily used to send 539 email to, to avoid the 540 problems with "Sender" and 541 "X-Sender". 543 Phone number of the Phone: Non-standard. 544 originator. 546 The person or agent Sender: RFC 822: 4.4.2, 547 submitting the message to RFC 2822 3.6.2, 548 the network, if other than RFC 1123: 549 shown by the From: header 5.2.15-16, 550 field. Should be 5.3.7, RFC 551 authenticated, 1036. 552 according to RFC 822, but 553 what 554 kind of authentication is 555 not 556 clear. Some implementations 557 expect that the e-mail 558 address used in this field 559 can be used to reach the 560 sender, others do not. See 561 also "X-Sender". 563 Primary recipients. To: RFC 2822:, 564 RFC 1123: 565 5.2.15-16, 566 5.3.7. 568 If the sender in the X-Envelope- Non-standard. 569 envelope (SMTP "RCTP TO") is From: 570 not the same as the senders 571 in the "From" or "Sender" 572 RFC 2822 header fields, some 573 mail servers add this to the 574 RFC 2822 header fields as an 575 aid to clients which would 576 otherwise not be able to 577 display this information. 579 If the recipient in the X-Envelope- Non-standard. 580 envelope (SMTP "MAIL FROM") To:, 581 is not included in the CC Envelope- 582 list, some mail servers add To: 583 this to the RFC 2822 header 584 field as an aid to clients 585 which would otherwise not be 586 able to display the envelope 587 recipients. 589 48x48 bitmap with picture of X-Face: Non-Standard 590 the sender of this message. 592 Indication in the mail X-RCPT-TO: Non-standard 593 header of recipient on the 594 SMTP envelope. 596 Some mail software expect X-Sender: Non-standard 597 "Sender:" to be an e-mail 598 address which you can send 599 mail to. However, some mail 600 software has as the best 601 authenticated sender a POP 602 or IMAP account, which you 603 might not be able to send 604 to. Because of this, some 605 mail software put the POP or 606 IMAP account into an X- 607 sender header field instead 608 of a Sender header field, to 609 indicate that you may not be 610 able to send e-mail to this 611 address. See also "X-X- 612 Sender". 614 Another use of" X-Sender:" 615 is that some e-mail 616 software, which wants to 617 insert a "Sender:" header, 618 will first change an 619 existing "Sender:" header to 620 "X-Sender". This use is 621 actually often the same as 622 that described in the 623 previous paragraph, since 624 the new "Sender:" is added 625 because it is better 626 authenticated than the old 627 value. 629 Even though some systems put X-X-Sender: Non-standard 630 the POP or IMAP account name 631 into the "X-Sender:" instead 632 of the Sender header field, 633 some mail software tries to 634 send to the "X-Sender:" too. 635 To stop this, some systems 636 have begun to use "X-X- 637 Sender:" to indicate an 638 authentication of the sender 639 which might not be useable 640 to send e-mail to. See also 641 "Originator-Info:" 643 When a message is sent both Posted-To: Non-standard 644 to netnews and e-mail, this 645 header is used in the e-mail 646 version of the message to 647 indicate which newsgroup it 648 was sent to. This header 649 thus contains the same 650 information as the 651 "Newsgroups:" header in the 652 netnews version of the 653 message. 655 E-mail address of X-Admin: Non-standard 656 administrator of a server, 657 through which this message 658 was submitted. 660 **** 3.5 Response control 662 Indicates whether the Content- RFC 2156, not 663 content of a message is to Return: for general 664 be returned with non- usage. 665 delivery notifications. 667 For future options on Disposition- RFC 2298 668 disposition notifications. Notificatio 669 n-Options: 671 Indicate that the sender Disposition- RFC 2298 672 wants a dispoisition Notificatio 673 notification when this n-To: 674 message is received (read, 675 processed, etc.) by its 676 receipents. 678 Address to which Errors-To:, Non-standard, 679 notifications are to be sent Return- discouraged, 680 and a request to get Receipt- some of them 681 delivery notifications. To:, widely used. 682 Internet standards Read- 683 recommend, however, the use Receipt- 684 of MAIL FROM and Return- To:, X- 685 Path, not Errors-To, for Confirm- 686 where delivery notifications reading- 687 are to be sent. to:, Return- 688 Receipt- 689 Requested, 690 Registered- 691 Mail-Reply- 692 Requested- 693 By: 695 Used in Usenet News to Followup- RFC 1036: 696 indicate that future To: 2.2.3, not 697 discussions (=follow-up) on standardized 698 an article should go to a for use in e- 699 different set of newsgroups mail. 700 than the replied-to article. 701 The most common usage is 702 when an article is posted to 703 several newsgroups, and 704 further discussions is to 705 take place in only one of 706 them. 708 In e-mail, this header field 709 may occur in a message which 710 is sent to both e-mail and 711 Usenet News, to show where 712 follow-up in Usenet news is 713 wanted. The header field 714 does not say anything about 715 where follow-up in e-mail is 716 to be sent. 718 The value of this header 719 field should be one or more 720 newsgroup names. 722 The special value "poster" 723 as in "Followup-To: poster" 724 means that replies are to be 725 sent as e-mail to the author 726 only. 728 Whether a delivery report is Generate- RFC 2156, not 729 wanted at successful Delivery- for general 730 delivery. Default is not to Report: usage. 731 generate such a report. 733 Original Recipient Original- RFC 2298 734 information for inclusion in Recipient 735 disposition notifications. 737 Whether non-delivery report Prevent- RFC 2156, not 738 is wanted at delivery error. NonDelivery- for general 739 Default is to want such a Report: usage. 740 report. 742 This header field is meant Reply-To: RFC 2822:, 743 to indicate where the sender RFC 1036: 2.2.1 744 wants replies to go. controversial. 745 Unfortunately, this is 746 ambiguous, since there are 747 different kinds of replies, 748 which the sender may wish to 749 go to different addresses. 750 In particular, there are 751 personal replies intended 752 for only one person, and 753 group replies, intended for 754 the whole group of people 755 who read the replied-to 756 message (often a mailing 757 list, anewsgroup name cannot 758 appear here because of 759 different syntax, see 760 "Followup-To" below.). 762 Some mail systems use this Reply-To2 763 header field to indicate a 764 better form of the e-mail 765 address of the sender. Some 766 mailing list expanders puts 767 the name of the list in this 768 header field. These 769 practices are controversial. 770 The personal opinion of the 771 author of this RFC is that 772 this header field should be 773 avoided except in special 774 cases, but this is a 775 personal opinion not shared 776 by all specialists in the 777 area. 779 Adress to which those Mail- Non-standard, 780 replies to this message Followup- see 781 should be sent, which are To: http://cr.yp.to 782 intended for all who read /proto/replyto. 783 the replied-to message, not html 784 only for its author. 786 Similar to "Reply-To:" but Mail-Reply- Non-standard, 787 more unambiguosly specifies To: see 788 that this is the address for http://cr.yp.to 789 rpelies to the author only, /proto/replyto. 790 not to any other recipients html 791 of the replied-to message. 793 Indicates where to send Abuse- non-standard 794 complains if you get a Reports- 795 message which you think is To:, X- 796 against the laws or rules. Complaints- 797 To:, X- 798 Report- 799 Abuse-To: 801 Used in netnews articles to Mail-Copies- non-standard, 802 indicate that followup To: but commonly 803 (=replies) should be sent to supported by 804 the indicated e-mail newsreaders 805 address. 807 Possible future change of X400- non-standard 808 name for "Content-Return:" Content- 809 Return: 811 **** 3.6 Message identification and referral header fields 813 Reference to specially Article- son-of-RFC1036 814 important articles for a Names: [21], non- 815 particular Usenet Newsgroup. standard 817 Only in Usenet News, similar Article- son-of-RFC1036 818 to "Supersedes:" but does Updates: [21], non- 819 not cause the referenced standard 820 article to be physically 821 deleted. 823 Used in addition to Content- Content- Work in 824 Location if this content Alias: progress 825 part can be retrieved 826 through more than one URI. 827 Only one of them is allowed 828 in the Content-Location, the 829 other can be specified in 830 Content-Alias. 832 Base to be used for Content- RFC 2110 833 resolving relative URIs Base: 834 within this content part. 836 Unique ID of one body part Content-ID: RFC 2045: 7. 837 of the content of a message. 839 URI with which the content Content- RFC 2110 840 of this content part might Location: 841 be retrievable. 843 Used by some automatic Delivered- non-standard 844 services (mainly MLMs and To: 845 autoresponders) for the or 846 purpose of loop detection. X-Loop: 847 The service adds the 848 Delivered-To header to 849 outgoing messages, with its 850 e-mail address as a value, 851 and discards incoming 852 messages which already have 853 it. 855 Reference to message which In-Reply- RFC 2822 856 this message is a reply to. To: 858 Note: It is better to use 859 References instead of In- 860 Reply-To, because many 861 mailers produce a multitude 862 of difficult to interpret 863 content of the In-Reply-To 864 header. 866 Unique ID of this message. Message-ID: RFC 2822, 867 RFC 1036: 868 2.1.5. 870 Reference to previous Obsoletes: RFC 2156, not 871 message being corrected and for general 872 replaced. Compare to usage. 873 "Supersedes:" below. This 874 field may in the future be 875 replaced with "Supersedes:". 877 The "References:" field will References: RFC 2822, 878 contain the contents of the RFC 1036: 879 parent's "References:" field 2.1.5. 880 (if any) followed by the 881 contents of the parent's 882 "Message-ID:" field (if 883 any). 885 Note: In RFC 822, this 886 header indicated other 887 messages, which the current 888 message relates to. But in 889 RFC 2822 this was changed. 890 In Usenet News, the header 891 has always has the new 892 usage. 893 Still another name for Replaces: non-standard, 894 similar functionality as for proposed in 895 "Obsoletes:" and IETF USEFOR 896 "Supersedes:". This may working group 897 become the most recommended 898 header in the future, but is 899 still under discussion in 900 IETF standards development 901 work. 903 References to other related See-Also: Son-of-RFC1036 904 articles in Usenet News. [21], non- 905 standard 907 Commonly used in Usenet News Supersedes: son-of-RFC1036 908 in similar ways to the [21], non- 909 "Obsoletes" header field standard 910 described above. In Usenet 911 News, however, Supersedes 912 causes a full deletion of 913 the replaced article in the 914 server, while "Supersedes" 915 and "Obsoletes" in e-mail is 916 implemented in the client 917 and often does not remove 918 the old version of the text. 920 Mailbox of the person who Translated- non-standard 921 made the translation. By: 923 Reference to the Message-ID Translation- non-standard 924 of a message, which the Of: 925 current message is a 926 translation of. 928 Unique identifier for a X-UIDL: non-standard 929 message, local to a 930 particular local mailbox 931 store. The UIDL identifier 932 is defined in the POP3 933 standard, but not the "X- 934 UIDL:" header. 936 Similar usage as "X-URL". X-URI: Non-standard 937 The URI can be either a URL 938 or a URN. URNs are meant to 939 become more persistent 940 references to resources than 941 URLs. 943 Sometimes used with the same X-URL: Non-standard 944 meaning as "Content- 945 Location:", sometimes to 946 indicate the web home page 947 of the sender or of his 948 organisation. 950 The UID, as defined in the X-IMAP: Non-standard 951 IMAP standard. Only used in 952 internal mailbox storage in 953 some mail systems, should 954 never be visible to a user. 956 **** 3.7 Other textual header fields 958 Comments on a message. Comments: RFC 2822 960 Description of a particular Content- RFC 2045: 8. 961 body part of a message, for Description 962 example a caption for an : 963 image body part. 965 A text string which Content- RFC 2156, not 966 identifies the content of a Identifier: for general 967 message. usage. 969 Search keys for data base Keywords: RFC 2822 970 retrieval. RFC 1036: 971 2.2.9. 973 See Organization above. Organisatio Non-standard. 974 n: 976 Organization to which the Organizatio RFC 1036: 977 sender of this article n: 2.2.8, not 978 belongs. standardized 979 for use in e- 980 mail. 982 Title, heading, subject. Subject: RFC 2822, 983 Often used as thread RFC 1036: 984 indicator for messages 2.1.4. 985 replying to or commenting on 986 other messages. 988 Short text describing a Summary: RFC 1036: 989 longer article. Warning: 2.2.10, not 990 Some mail systems will not standardized 991 display this text to the for use in e- 992 recipient. Because of this, mail, 993 do not use this header field discouraged. 994 for text which you want to 995 ensure that the recipient 996 gets. 998 **** 3.8 Header fields containing dates and times 1000 In Internet, the date when a Date: RFC 2822, 1001 message was written, in RFC 1123: 1002 X.400, the time a message 5.2.14 1003 was submitted. Some Internet RFC 1036: 1004 mail systems also use the 2.1.2. 1005 date when the message was 1006 submitted. 1008 The time when a message was Delivery- RFC 2156, not 1009 delivered to its recipient. Date: for general 1010 usage. 1012 A suggested expiration date. Expires: RFC 1036: 1013 Can be used both to limit 2.2.4, not 1014 the time of an article which standardized 1015 is not meaningful after a for use in e- 1016 certain date, and to extend mail. 1017 the storage of important 1018 articles. 1020 Time at which a message Expiry- RFC 2156, not 1021 loses its validity. This Date: for general 1022 field may in the future be usage. 1023 replaced by "Expires:". 1025 Latest time at which a reply Reply-By: RFC 2156, not 1026 is requested (not demanded). for general 1027 usage. 1029 Time when this message was X-OriginalA Non-standard 1030 delivered into the message rrivalTime: 1031 transport system (usually 1032 the same time as in the last 1033 "Received:" header) 1035 **** 3.9 Quality information 1037 A hint from the originator Importance: RFC 2156 and 1038 to the recipients about how RFC 2421, 1039 important a message is. proposed 1040 Values: High, normal or low. 1041 Not used to control 1042 transmission speed. 1044 Body parts are missing. Incomplete- RFC 2156, not 1045 Copy: for general 1046 usage. 1048 Ratings label to control PICS-Label: REC-PICS- 1049 selection (filtering) of labels, W3C 1050 messages according to the document [23]. 1051 PICS protocol. 1053 Sometimes used as a (a) Precedence: Non-standard, 1054 priority value which can controversial, 1055 influence transmission speed widely used. 1056 and delivery. Common values Because it is 1057 are "bulk" and "first- used for so 1058 class". Other uses is to (b) many different 1059 control automatic replies purposes, there 1060 like delivery status reports is a risk that 1061 and vacation notices and to creator and 1062 (c) control return-of- user of this 1063 content facilities, and to header mean 1064 (d) stop mailing list loops, different 1065 (e) things. 1067 Can be "normal", "urgent" or Priority: RFC 2156, not 1068 "non-urgent" and can for general 1069 influence transmission speed usage. 1070 and delivery. 1072 How sensitive it is to Sensitivity RFC 2156 and 1073 disclose this message to : RFC 2421, 1074 other people than the proposed 1075 specified recipients. 1076 Values: Personal, private, 1077 company confidential. The 1078 absence of this header field 1079 in messages gatewayed from 1080 X.400 indicates that the 1081 message is not sensitive. 1083 Yet another priority X-MSMail- Non-standard 1084 indication. Priority: 1086 Values: 1 (Highest), 2 X-Priority: Non-standard 1087 (High), 3 (Normal), 4 (Low), [24] 1088 5 (Lowest). 3 (Normal) is 1089 default if the field is 1090 omitted. 1092 **** 3.10 Language information 1094 Can include a code for the Content- RFC 1766, 1095 natural language used in a Language: proposed 1096 message, e.g. "en" for standard. 1097 English. 1099 Can include a code for the Language: RFC 2156, not 1100 natural language used in a for general 1101 message, e.g. "en" for usage. 1102 English. 1104 **** 3.11 Size information 1106 Inserted by certain mailers Content- Non-standard, 1107 to indicate the size in Length: discouraged. 1108 bytes of the message text. 1109 This is part of a format 1110 some mailers use when 1111 showing a message to its 1112 users, and this header field 1113 should not be used when 1114 sending a message through 1115 the net. The use of this 1116 header field in transmission 1117 of a message can cause 1118 several robustness and 1119 interoperability problems. 1121 Size of the message. Lines: RFC 1036: 1122 2.2.12, not 1123 standardized 1124 for use in e- 1125 mail. Will be 1126 deprecated in 1127 the future. 1129 **** 3.12 Conversion control 1131 Information on where an Content- Non-standard 1132 alternative variant of this Alternative [27]. 1133 document might be found. : 1135 Non-standard variant of Content- Non-standard. 1136 Conversion: with the same Conversion: 1137 values. 1139 The body of this message may Conversion: RFC 2156, not 1140 not be converted from one for general 1141 character set to another. usage. 1142 Values: Prohibited and 1143 allowed. 1145 The body of this message may Conversion- RFC 2156, not 1146 not be converted from one With-Loss: for general 1147 character set to another if usage. 1148 information will be lost. 1149 Values: Prohibited and 1150 allowed. 1152 **** 3.13 Encoding information 1154 Type information of the Content- non-standard 1155 content in some class Class: 1156 hierarchy. Class hierarchies 1157 are commonly used to 1158 classify data structures in 1159 software development. 1161 Can give more detailed Content- Proposed 1162 information about the Features: Standard, RFC 1163 Content-Type. Example: 2912 1165 Content-features: 1166 (& (Type="image/tiff") 1167 (color=Binary) 1168 (image-file-structure=TIFF-S) 1169 (dpi=200) 1170 (dpi-xyratio=200/100) 1171 (paper-size=A4) 1172 (image-coding=MH) (MRC-mode=0) 1173 (ua-media=stationery) ) 1175 This header is meant to be used when you can choose between 1176 different versions of a resource, such as when using 1177 multipart/atlernative. 1179 Information from the SGML Content- non-standard 1180 entity declaration SGML- 1181 corresponding to the entity Entity: 1182 contained in the body of the 1183 body part. 1185 Coding method used in a MIME Content- RFC 2045: 6. 1186 message body. Transfer- 1187 Encoding: 1189 Format of content (character Content- RFC 1049, 1190 set etc.) Note that the Type: RFC 1123: 1191 values for this header field 5.2.13, 1192 are defined in different RFC 1766: 4.1 1193 ways in RFC 1049 and in MIME RFC 2045: 5. 1194 (RFC 2045), look for the 1195 "MIME-version" header field 1196 to understand if Content- 1197 Type is to be interpreted 1198 according to RFC 1049 or 1199 according to MIME. The MIME 1200 definition should be used in 1201 generating mail. RFC 1049 1202 has "historic" status. 1204 RFC 1766 defines a parameter 1205 "difference" to this header 1206 field. 1208 Various other Content-Type 1209 define various additional 1210 parameters. For example, the 1211 parameter "charset" is 1212 mandatory for all textual 1213 Content-Types. 1215 Used in several different Encoding: RFC 1154, 1216 ways by different mail RFC 1505, 1217 systems. Some use it for a experimental. 1218 kind of content-type 1219 information, some for 1220 encoding and length 1221 information, some for a kind 1222 of boundary information, 1223 some in other ways. 1225 Only used with the value Message- RFC 2156, not 1226 "Delivery Report" to Type: for general 1227 indicates that this is a usage. 1228 delivery report gatewayed 1229 from X.400. 1231 Information about conversion X-MIME- non-standard 1232 of this message on the path Autoconverte 1233 from sender to recipient, d: 1234 like conversion between MIME 1235 encoding formats. Note: Auto- 1236 conversion may invalidate 1237 digital seals and 1238 signatures. 1240 **** 3.14 Resent-header fields 1242 When manually forwarding a Resent- RFC 2822 1243 message, header fields Reply-To:, 1244 referring to the forwarding, Resent- 1245 not to the original message. From:, 1246 Note: MIME specifies another Resent- 1247 way of resending messages, Sender:, 1248 using the "Message" Content- Resent- 1249 Type. Date:, 1250 Resent-To:, 1251 Resent-cc:, 1252 Resent- 1253 bcc:, 1254 Resent- 1255 Message-ID: 1257 **** 3.15 Security and reliability 1259 Checksum of content to Content- RFC 1864, 1260 ensure that it has not been MD5: proposed 1261 modified. standard. 1263 Used in Usenet News to store Xref: RFC 1036: 1264 information to avoid showing 2.2.13, only in 1265 a reader the same article Usenet News, 1266 twice if it was sent to more not in e-mail. 1267 than one newsgroup. Only for 1268 local usage within one 1269 Usenet News server, should 1270 not be sent between servers. 1272 Used in Usenet News to stop Cancel- Non-standard 1273 rough cancels. Lock:, 1274 Crypthographic methods are Cancel-Key 1275 used to ensure that only the 1276 original author of an 1277 article can cancel it. 1279 **** 3.16 Mailing list control 1281 Contains URL to use to List- RFC 2369 [26] 1282 browse the archives of the Archive: 1283 mailing list from which this 1284 message was relayed. 1286 URL to use to get a List- Non-standard 1287 subscription to the digest Digest: 1288 version of the mailing list 1289 from which this message was 1290 relayed. 1292 Contains URL to use to get a List-Help: RFC 2369 [26] 1293 information about the 1294 mailing list from which this 1295 message was relayed. 1297 Stores an identification of List-ID: RFC 2919 [27]. 1298 the mailing list, through 1299 which this message was 1300 distributed. 1302 Non-standard precursors to Mailing- Non-standard 1303 List-ID and List-Post. List:, X- 1304 Mailing- 1305 List: 1307 Contains URL to send e-mail List-Owner: RFC 2369 [26] 1308 to the owner of the mailing 1309 list from which this message 1310 was relayed. 1312 Contains URL to use to send List-Post: RFC 2369 [26] 1313 contributions to the mailing 1314 list from which this message 1315 was relayed. 1317 Information about the List- Non-standard, 1318 software used in a mailing Software: has been 1319 list expander through which considered for 1320 this message has passed. inclusion in 1321 [26]. 1322 Contains URL to use to get a List- RFC 2369 [26] 1323 subscription to the mailing Subscribe: 1324 list from which this message 1325 was relayed. 1327 Contains URL to use to List- RFC 2369 [26] 1328 unsubscribe the mailing list Unsubscribe 1329 from which this message was : 1330 relayed. 1332 Contains URL where List-URL: Non-standard 1333 information of various kinds 1334 about the mailing list from 1335 which this message was 1336 relayed. 1338 Information about the server X- Non-standard. 1339 and software used in a Listserver: Recommended to 1340 mailing list expander , X-List- use "List- 1341 through which this message Host: Software" 1342 has passed. Warning: instead. 1343 "Listserv" is a trademark 1344 and should not be used for 1345 other than the "Listserv" 1346 product. Use, instead the 1347 "List-Software" header 1348 field. 1350 **** 3.17 Miscellaneous 1352 Has been automatically Autoforward RFC 2156, not 1353 forwarded. ed: for general 1354 usage. 1356 Can be used in Internet mail Discarded- RFC 2156, not 1357 to indicate X.400 IPM X400-IPMS- for general 1358 extensions which could not Extensions: usage. 1359 be mapped to Internet mail 1360 format. 1362 Can be used in Internet mail Discarded- RFC 2156, not 1363 to indicate X.400 MTS X400-MTS- for general 1364 extensions which could not Extensions: usage. 1365 be mapped to Internet mail 1366 format. 1368 Name of file in which a copy Fcc: Non-standard. 1369 of this message is stored. 1371 Speech act categoriztion of Speech-Act: Non-standard 1372 a message, examples of 1373 speeach acts are Question, 1374 Idea, More, Promise, Sad, 1375 Happy, Angry, summary, 1376 Decision 1378 This field is used by some Status: Non-standard, 1379 mail delivery systems to should never 1380 indicate the status of appear in mail 1381 delivery for this message in transit. 1382 when stored. Common values 1383 of this field are: 1385 U message is not 1386 Downloaded and 1387 not deleted. 1389 R message is read 1390 or downloaded. 1392 O message is old 1393 but not deleted. 1395 D to be deleted. 1397 N new (a new message 1398 also sometimes is 1399 distinguished by 1400 not having any 1401 "Status:" header 1402 field. 1404 Combinations of these 1405 characters can occur, such 1406 as "Status: OR" to indicate 1407 that a message is downloaded 1408 but not deleted. 1410 Do not archive this message X-No- Non-standard 1411 in publicly available Archive: 1412 archives. Yes 1414 4. Acknowledgments 1416 Harald Tveit Alvestrand, Neil Carpenter, William C. 1417 Carpenter, Rob Chandhok, Ned Freed, Olle J�rnefors, Jukka 1418 Korpela, Usi Paz, Martin Platt, Keith Moore, Maxim 1419 Masiutin, Robert A. Rosenberg, Mark Symons, Nick Smith 1420 Michael C. Tiernan and several other people have helped me 1421 with compiling this list. I especially thank Ned Freed and 1422 Olle J�rnefors for their thorough review and many helpful 1423 suggestions for improvements. I alone take responsibility 1424 for any errors which may still be in the list. 1426 An earlier version of this list has been published as part 1427 of [13]. 1429 Copyright and disclaimer 1431 The IETF takes no position regarding the validity 1432 or scope of any intellectual property or other 1433 rights that might be claimed to pertain to the 1434 implementation or use of the technology described 1435 in this document or the extent to which any 1436 license under such rights might or might not be 1437 available; neither does it represent that it has 1438 made any effort to identify any such rights. 1439 Information on the IETF's procedures with respect 1440 to rights in standards-track and standards- 1441 related documentation can be found in BCP-11. 1442 Copies of claims of rights made available for 1443 publication and any assurances of licenses to be 1444 made available, or the result of an attempt made 1445 to obtain a general license or permission for the 1446 use of such proprietary rights by implementors or 1447 users of this specification can be obtained from 1448 the IETF Secretariat." 1450 The IETF invites any interested party to bring to 1451 its attention any copyrights, patents or patent 1452 applications, or other proprietary rights which 1453 may cover technology that may be required to 1454 practice this standard. Please address the 1455 information to the IETF Executive Director. 1457 Copyright (C) The Internet Society (date). All 1458 Rights Reserved. 1460 This document and translations of it may be 1461 copied and furnished to others, and derivative 1462 works that comment on or otherwise explain it or 1463 assist in its implmentation may be prepared, 1464 copied, published and distributed, in whole or in 1465 part, without restriction of any kind, provided 1466 that the above copyright notice and this 1467 paragraph are included on all such copies and 1468 derivative works. However, this document itself 1469 may not be modified in any way, such as by 1470 removing the copyright notice or references to 1471 the Internet Society or other Internet 1472 organizations, except as needed for the purpose 1473 of developing Internet standards in which case 1474 the procedures for copyrights defined in the 1475 Internet Standards process must be followed, or 1476 as required to translate it into languages other 1477 than English. 1479 The limited permissions granted above are 1480 perpetual and will not be revoked by the Internet 1481 Society or its successors or assigns. 1483 5. References 1485 Ref. Author, title IETF 1486 status 1487 ---- ------------------------------------ (July 1488 2002) 1489 ---------- 1490 [1] J. Klensin: "Simple Mail Transfer Proposed 1491 Protocol", RFC 2821, April 2001. Standard 1493 [2] P. Resnick: "Internet Message Format" Proposed 1494 STD 11, RFC 2822, April 2001. Standard 1496 [3] M.R. Horton, R. Adams: "Standard for Not an 1497 interchange of USENET messages", RFC offi-cial 1498 1036, December 1987. IETF 1499 standard, 1500 but in 1501 reality a 1502 de-facto 1503 standard 1504 for Usenet 1505 News 1507 [4] M. Sirbu: "A Content-Type header Historic 1508 field header field for internet 1509 messages", RFC 1049, March 1988. 1511 [5] R. Braden (editor): "Requirements for Standard, 1512 Internet Hosts -- Application and Required 1513 Support", STD-3, RFC 1123, October 1514 1989. 1516 [6] D. Robinson, R. Ullman: "Encoding Non- 1517 Header field for Internet Messages", standard 1518 RFC 1505, August 1993. 1520 [7] S. Hardcastle-Kille: "Mapping between Proposed 1521 X.400(1988) / ISO 10021 and RFC standard, 1522 2822", RFC 2156 January 1998. elective 1524 [8] H. Alvestrand & J. Romaguera: "Rules Proposed 1525 for Downgrading Messages from standard, 1526 X.400/88 to X.400/84 When MIME elective 1527 Content-Types are Present in the 1528 Messages", RFC 1496, August 1993. 1530 [9] A. Costanzo: "Encoding Header field Non- 1531 Header field for Internet Messages", standard 1532 RFC 1154, April 1990. 1534 [10] A. Costanzo, D. Robinson: "Encoding Experiment 1535 Header field Header field for al 1536 Internet Messages", RFC 1505, August 1537 1993. 1539 [11] N. Freed & N. Borenstein: "MIME Draft 1540 (Multipurpose Internet Mail Standard, 1541 Extensions) Part One: Format of elective 1542 Internet Message Bodies. RFC 2045. 1543 November 1996. 1545 [12] H. Alvestrand: "Tags for the Best 1546 Identification of Languages", RFC Current 1547 3066, January 2001. Practice, 1548 elective 1550 [13] J. Palme: "Electronic Mail", Artech Non- 1551 House publishers, London-Boston standard 1552 January 1995. 1554 [14] R. Troost, S. Dorner: "Communicating Experimental 1555 Presentation Information in Internet 1556 Messages: The Content-Disposition 1557 Header field", RFC 2183, June 1995. 1559 [15] B. Kantor, P. Lapsley, "Network News Proposed 1560 Transfer Protocol: "A Proposed standard 1561 Standard for the Stream-Based 1562 Transmission of News", RFC 977, 1563 January 1986. 1564 [16] 1848 PS S. Crocker, N. Freed, J. Proposed 1565 Galvin, S. Murphy, "MIME Object standard 1566 Security Services", RFC 1848, March 1567 1995. 1569 [17] J. Myers, M. Rose: The Content-MD5 Draft 1570 Header field Header field, RFC 1864, standard 1571 October 1995. 1573 [18] M. Horton, UUCP mail interchange Not an 1574 format standard, RFC 976, Januari offi-cial 1575 1986. IETF 1576 standard, 1577 but in 1578 reality a 1579 de-facto 1580 standard 1581 for Usenet 1582 News 1584 [19] R. Fielding, J. Gettys, J. Mogul, H. Draft 1585 Frystyk, L. Masinter, P. Leach, T. standard 1586 Berners-Lee: Hypertext Transfer 1587 Protocol -- HTTP/1.1, June 1999. 1588 [20] G. Vaudreuil: Voice Profile for Proposed 1589 Internet Mail, RFC 2421 Feburary 1590 1998. 1592 [21] H. Spencer: News Article Format and Not even an 1593 Transmission, June 1994, RFC, but 1594 FTP://zoo.toronto.edu/pub/news.ps.Z still 1595 FTP://zoo.toronto.edu/pub/news.txt.Z widely used 1596 and partly 1597 This document is often referenced almost a de- 1598 under the name "son-of-RFC1036". facto 1599 standard 1600 for Usenet 1601 News 1603 [23] PICS Label Distribution Label Syntax Other 1604 and Communication Protocols, World standard 1605 Wide Web Consortium, October 1996. 1607 [24] Eudora Pro Macintosh User Manual, Non- 1608 Qualcomm Inc., 1988-1995. standard 1610 [25] C. Newman: Originator-Info Message Non- 1611 Header field. work in progress, July standard 1612 1997. 1614 [26] Grant Neufeld and Joshua D. Baer: The Proposed 1615 Use of URLs as Meta-Syntax for Core standard 1616 Mail List Commands and their 1617 Transport through Message Header 1618 fields, RFC 2369, July 1998. 1620 [27] G. Klyne (ed.): Content Negotiation Non- 1621 for Facsimile Using Internet Mail, standard 1622 Work in progress, March 2000. 1624 [27] R. Chandhok, G. Wenger: List-IDE: A Proposed 1625 Structured Field and Namespace for standard 1626 the Identification if Mailing Lists, 1627 RFC 2919, March 2001. 1629 [28] Jukka "Yucca" Korpela: Quick Non- 1630 reference to Internet message standard 1631 headers, 1632 http://www.cs.tut.fi/~jkorpela/header 1633 s.html, October 2001. 1635 6. Author's address 1637 Jacob Palme Phone: +46-8-16 16 67 1638 Stockholm University/KTH Fax: +46-8-783 08 29 1639 Forum 100 E-mail: jpalme@dsv.su.se 1640 S-164 40 Kista, Sweden 1642 Appendix A: 1643 Header fields sorted by Internet RFC document in which 1644 they appear. 1646 RFC 976 1647 ------- 1649 "From " (followed by space, not colon (:") 1651 RFC 1049 1652 -------- 1654 Content-Type 1656 RFC 1036 1657 -------- 1659 Approved 1660 Control 1661 Distribution 1662 Expires 1663 Followup-To 1664 Lines 1665 Newsgroups 1666 Organization 1667 Path 1668 Summary 1669 Xref 1671 RFC 1123 1672 -------- 1674 Content-Type 1676 RFC 1505 1677 -------- 1679 Encoding 1681 RFC 1766 1682 -------- 1684 Content-Language 1686 RFC 1864 1687 -------- 1689 Content-MD5 1691 RFC 2045 1692 -------- 1694 Content-Description 1695 Content-ID 1696 Content-Transfer-Encoding 1697 Content-Type 1698 MIME-Version 1700 RFC 2110 1701 -------- 1703 Content-Base 1704 Content-Location 1705 RFC 2156 1706 -------- 1708 Alternate-recipient 1709 Auto-forwarded see Autoforwarded 1710 Autoforwarded 1711 Content-Identifier 1712 Content-Return 1713 Conversion 1714 Conversion-With-Loss 1715 Delivery-Date 1716 Discarded-X400-IPMS-Extensions 1717 Discarded-X400-MTS-Extensions 1718 Disclose-Recipients 1719 DL-Expansion-History 1720 Expiry-Date 1721 Generate-Delivery-Report 1722 Importance 1723 Incomplete-Copy 1724 Language 1725 Message-Type 1726 Obsoletes 1727 Original-Encoded-Information-Types 1728 Prevent-NonDelivery-Report 1729 Priority 1730 Reply-By 1731 Sensitivity 1733 RFC 2183 1734 -------- 1736 Content-Disposition 1738 RFC 2298 1739 -------- 1741 Disposition-Notification-To 1742 Disposition-Notification-Options 1743 Original-Recipient 1745 RFC 2369 1746 -------- 1748 List-Archive 1749 List-Help 1750 List-Owner 1751 List-Post 1752 List-Software 1753 List-Subscribe 1754 List-Unsubscribe 1756 RFC 2421 1757 -------- 1759 Importance 1760 Sensitivity 1762 son-of-RFC1036 [21] 1763 ------------------- 1765 Also-Control 1766 Article-Names 1767 Article-Updates 1768 See-Also 1769 Supersedes 1771 RFC 2822 1772 -------- 1774 bcc 1775 cc 1776 Comments 1777 Date 1778 From 1779 In-Reply-To 1780 Keywords 1781 Message-ID 1782 Received 1783 References 1784 Reply-To 1785 Resent-bcc 1786 Resent-cc 1787 Resent-Date 1788 Resent-From 1789 Resent-Message-ID 1790 Resent-Reply-To 1791 Resent-Sender 1792 Resent-To 1793 Return-Path 1794 Sender 1795 Subject 1796 To 1798 RFC 2912 1799 -------- 1801 Content-Features 1803 RFC 2919: 1804 -------- 1806 List-ID 1808 World Wide Web Consortium (W3C) Recommendations 1809 ----------------------------------------------- 1811 Pics-Label 1813 Not Internet standard (as of July 2002) 1814 --------------------------------------- 1816 "From " (not followed by ":") 1817 Abuse-Reports-To 1818 Apparently-To 1819 Approved-By 1820 Cancel-Key 1821 Cancel-Lock 1822 Content-Alias 1823 Content-Alternative 1824 Content-Class 1825 Content-Conversion 1826 Content-Length 1827 Content-SGML-Entity 1828 Delivered-To 1829 Encoding 1830 Errors-To 1831 Fax 1832 Fcc 1833 For-Approval 1834 For-Comment 1835 For-Handling 1836 List-Digest 1837 List-URL 1838 Mailing-List 1839 Mail-Copies-To 1840 Mail-Followup-To 1841 Mail-Reply-To 1842 Mail-System-Version 1843 Mailer 1844 Message-Context 1845 NNTP-Posting-Host 1846 Organisation 1847 Originating-Client 1848 Originator 1849 Originator-Info 1850 Phone 1851 Posted-To 1852 Precedence 1853 Registered-Mail-Reply-Requested-By 1854 Replaces 1855 Return-Receipt-Requested 1856 Return-Receipt-To 1857 Read-Receipt-To 1858 Speech-Act 1859 Status 1860 Supersedes 1861 Telefax 1862 Translated-By 1863 Translation-Of 1864 User-Agent 1865 X-Admin 1866 X-Confirm-Reading-To 1867 X-Complaints-To 1868 X-Envelope-From 1869 X-Envelope-To 1870 X-Face 1871 X-IMAP 1872 X-Loop 1873 X-List-Host 1874 X-Listserver 1875 X-Mailer 1876 X-Mailing-List 1877 X-MIME-Autoconverted 1878 X-MIMEOLE 1879 X-MSMail-Priority 1880 X-Newsreader 1881 X-No-Archive 1882 X-OriginalArrivalTime 1883 X-Priority 1884 X-RCPT-TO 1885 X-Report-Abuse-To 1886 X-Sender 1887 X-UIDL 1888 X-URI 1889 X-URL 1890 X-X-Sender 1891 X400-Content-Return 1893 Appendix B: Alphabetical index 1895 Sectio Header field 1896 n ------------ 1897 ------ 1898 - 1900 3.5 Abuse-Reports-To 1901 3.3 Also-Control 1902 3.3 Alternate-Recipient 1903 3.4 Apparently-To 1904 3.4 Approved 1905 3.4 Approved-By 1906 3.6 Article-Names 1907 3.6 Article-Updates 1908 Auto-Forwarded see Autoforwarded 1909 3.17 Autoforwarded 1910 3.4 bcc 1911 3.15 Cancel-Lock 1912 3.4 cc 1913 Client, see Originating-Client 1914 Comment, see For-Comment 1915 3.7 Comments 1916 3.6 Content-Alias 1917 3.12 Content-Alternative 1918 3.6 Content-Base 1919 3.13 Content-Class 1920 3.12 Content-Conversion 1921 3.7 Content-Description 1922 3.3 Content-Disposition 1923 3.13 Content-Features 1924 3.6 Content-ID 1925 3.7 Content-Identifier 1926 3.10 Content-Language see also Language 1927 3.11 Content-Length 1928 3.6 Content-Location 1929 3.15 Content-MD5 1930 3.4 Content-Return 1931 3.13 Content-SGML-Entity 1932 3.13 Content-Transfer-Encoding 1933 3.13 Content-Type 1934 3.3 Control 1935 3.12 Conversion 1936 3.12 Conversion-With-Loss 1937 Copy, see Incomplete-Copy 1938 3.8 Date, see also Delivery-Date, Received, Expires, 1939 Expiry-Date 1940 3.6 Delivered-To 1941 3.8 Delivery-Date 1942 Delivery-Report, see Generate-Delivery-Report, 1943 Prevent-Delivery-Report, Non-Delivery-Report, 1944 Content-Type 1945 Description, see Content-Description 1946 3.17 Discarded-X400-IPMS-Extensions 1947 3.17 Discarded-X400-MTS-Extensions 1948 3.3 Disclose-Recipients 1949 Disposition, see also Content-Disposition 1950 3.5 Disposition-Notification-Options 1951 3.5 Disposition-Notification-To 1952 3.4 Distribution 1953 3.2 DL-Expansion-History 1954 3.13 Encoding see also Content-Transfer-Encoding 1955 3.4 Errors-To 1956 3.8 Expires 1957 3.8 Expiry-Date 1958 Extension see Discarded-X400-IPMS-Extensions, 1959 Discarded-X400-MTS-Extensions 1960 3.4 Fax see also Telefax 1961 3.17 Fcc 1962 3.4 Followup-To 1963 3.4 For-Approval 1964 3.4 For-Comment 1965 3.4 For-Handling 1966 Forwarded, see Autoforwarded 1967 3.4 From (not followed by (":" or preceded by ">") 1968 3.4 From (followed by ":") 1969 3.4 Generate-Delivery-Report 1970 Handling, see For-Handling 1971 History, see DL-Expansion-History 1972 ID, see Content-ID and Message-ID 1973 Identifier, see Content-ID and Message-ID 1974 3.9 Importance 1975 3.6 In-Reply-To 1976 3.9 Incomplete-Copy 1977 3.7 Keywords 1978 Label, see PICS-Label 1979 3.10 Language see also Content-Language 1980 Length see Content-Length 1981 3.11 Lines 1982 3.16 List-Archive 1983 3.16 List-Digest 1984 3.16 List-Help 1985 3.16 List-ID 1986 3.16 List-Owner 1987 3.16 List-Post 1988 3.16 List-Software 1989 3.16 List-Subscribe 1990 3.16 List-URL 1991 3.16 List-Unsubscribe 1992 Loss, see Conversion-With-Loss 1993 3.16 Mailing-List, see also X-Mailing-List 1994 3.5 Mail-Copies-To 1995 3.6 Mail-Followup-To 1996 3.6 Mail-Reply-To 1997 3.4 Mail-System-Version see also X-mailer 1998 3.4 Mailer 1999 MD5 see Content-MD5 2000 3.3 Message-Context 2001 3.6 Message-ID 2002 3.13 Message-Type 2003 3.3 MIME-Version 2004 3.4 Newsgroups 2005 Newsreader, see X-Newsreader 2006 3.3 NNTP-Posting-Host 2007 3.6 Obsoletes 2008 3.7 Organisation 2009 3.7 Organization 2010 3.3 Original-Encoded-Information-Types 2011 3.6 Original-Recipient 2012 3.4 Originating-Client 2013 3.4 Originator 2014 3.4 Originator-Info see also Sender 2015 3.2 Path 2016 3.4 Phone 2017 3.9 PICS-Label 2018 3.4 Posted-To 2019 3.9 Precedence 2020 3.4 Prevent-NonDelivery-Report 2021 3.9 Priority 2022 3.5 Read-Reciept-To 2023 3.2 Received 2024 Recipient, see To, cc, bcc, Alternate-Recipient, 2025 Disclose-Recipients 2026 3.6 References 2027 3.5 Registered-Mail-Reply-Requested-By 2028 3.6 Replaces 2029 3.8 Reply-By 2030 3.4 Reply-To, see also In-Reply-To, References 2031 3.14 Resent-Reply-To: 2032 3.14 Resent-From: 2033 3.14 Resent-Sender: 2034 3.14 Resent-Date: 2035 3.14 Resent-To: 2036 3.14 Resent-Cc: 2037 3.14 Resent-bcc: 2038 3.14 Resent-Message-ID: 2039 3.14 Return see Content-Return 2040 3.2 Return-Path 2041 3.5 Return-Receipt-Requested 2042 3.5 Return-Receipt-To 2043 3.6 See-Also 2044 3.4 Sender 2045 3.9 Sensitivity 2046 3.17 Speech-Act 2047 3.17 Status 2048 3.7 Subject 2049 3.7 Summary 2050 3.6 Supersedes 2051 3.4 Telefax see also Fax 2052 3.4 To 2053 Transfer-Encoding see Content-Transfer-Encoding 2054 3.6 Translated-By 2055 3.6 Translation-Of 2056 Type see Content-Type, Message-Type, Original- 2057 Encoded-Information-Types 2058 3.4 User-Agent 2059 Version, see MIME-Version, X-Mailer 2060 3.4 X-Admin 2061 3.4 X-Complaints-To 2062 3.5 X-Confirm-Reading-To 2063 3.4 X-Envelope-From 2064 3.4 X-Envelope-To 2065 3.4 X-Face 2066 3.6 X-IMAP 2067 3.16 X-List-Host 2068 3.16 X-Listserver 2069 3.6 X-Loop 2070 3.16 X-Mailing-List, see also Mailing-List 2071 3.4 X-Mailer see also Mail-System-Version 2072 3.13 X-MIME-Autoconverted 2073 3.4 X-MimeOLE 2074 3.9 X-MSMail-Priority 2075 3.4 X-Newsreader 2076 3.17 X-No-Archive 2077 3.8 X-OriginalArrivaltime 2078 3.9 X-Priority 2079 3.4 X-Report-Abuse-To 2080 3.4 X-RCPT-TO 2081 3.4 X-Sender see also Originator-Info 2082 3.6 X-UIDL 2083 3.6 X-URI 2084 3.6 X-URL see also Content-Location 2085 3.4 X-X-Sender see also Originator-Info 2086 3.4 X400-Content-Return 2087 3.15 Xref