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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 2821 (Obsoleted by RFC 5321) ** Obsolete normative reference: RFC 3462 (Obsoleted by RFC 6522) ** Obsolete normative reference: RFC 3798 (Obsoleted by RFC 8098) ** Obsolete normative reference: RFC 4234 (Obsoleted by RFC 5234) == Outdated reference: A later version (-12) exists of draft-ietf-eai-utf8headers-07 == Outdated reference: A later version (-13) exists of draft-ietf-eai-smtpext-08 ** Obsolete normative reference: RFC 4646 (ref. 'LANGTAGS') (Obsoleted by RFC 5646) == Outdated reference: A later version (-12) exists of draft-ietf-eai-downgrade-04 Summary: 6 errors (**), 0 flaws (~~), 4 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Newman 3 Internet-Draft Sun Microsystems 4 Updates: 3461,3464,3798 A. Melnikov, Ed. 5 (if approved) Isode Ltd 6 Intended status: Experimental September 28, 2007 7 Expires: March 31, 2008 9 International Delivery and Disposition Notifications 10 draft-ietf-eai-dsn-04.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on March 31, 2008. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 41 Abstract 43 Delivery status notifications (DSNs) are critical to the correct 44 operation of an email system. However, the existing draft standard 45 is presently limited to US-ASCII text in the machine readable 46 portions of the protocol. This specification adds a new address type 47 for international email addresses so an original recipient address 48 with non-US-ASCII characters can be correctly preserved even after 49 downgrading. This also provides updated content return media types 50 for delivery status notifications and message disposition 51 notifications to support use of the new address type. 53 This document experimentally extends RFC 3461, RFC 3464 and RFC 3798. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Conventions Used in this Document . . . . . . . . . . . . . . 3 59 3. UTF-8 Address Type . . . . . . . . . . . . . . . . . . . . . . 3 60 4. UTF-8 Delivery Status Notifications . . . . . . . . . . . . . 6 61 4.1. Additional requirements on SMTP servers . . . . . . . . . 8 62 5. UTF-8 Message Disposition Notifications . . . . . . . . . . . 8 63 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 64 6.1. UTF-8 Mail Address Type Registration . . . . . . . . . . . 10 65 6.2. Update to 'smtp' Diagnostic Type Registration . . . . . . 11 66 6.3. message/global-headers . . . . . . . . . . . . . . . . . . 11 67 6.4. message/global-delivery-status . . . . . . . . . . . . . . 12 68 6.5. message/global-disposition-notification . . . . . . . . . 13 69 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 70 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 71 8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 72 8.2. Informative References . . . . . . . . . . . . . . . . . . 16 73 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17 74 Appendix B. Changes from -02 . . . . . . . . . . . . . . . . . . 17 75 Appendix C. Changes from -01 . . . . . . . . . . . . . . . . . . 17 76 Appendix D. Changes from -00 . . . . . . . . . . . . . . . . . . 17 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 78 Intellectual Property and Copyright Statements . . . . . . . . . . 19 80 1. Introduction 82 When an email message is transmitted using the UTF8SMTP 83 [I-D.ietf-eai-smtpext] extension and Internationalized Email Headers 84 [I-D.ietf-eai-utf8headers], it is sometimes necessary to return that 85 message or generate a Message Disposition Notification [RFC3798] 86 (MDN). As a message sent to multiple recipients can generate a 87 status and disposition notification for each recipient, it is helpful 88 if a client can correlate these returns based on the recipient 89 address it provided, thus preservation of the original recipient is 90 important. This specification describes how to preserve the original 91 recipient and updates the MDN and DSN formats to support the new 92 address types. 94 2. Conventions Used in this Document 96 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 97 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 98 document are to be interpreted as described in [RFC2119]. 100 The formal syntax use the Augmented Backus-Naur Form (ABNF) [RFC4234] 101 notation including the core rules defined in Appendix B of RFC 4234 102 and the UTF-8 syntax rules in section 4 of [RFC3629]. 104 3. UTF-8 Address Type 106 An Extensible Message Format for Delivery Status Notifications 107 [RFC3464] defines the concept of an address type. The address format 108 introduced in Internationalized Email Headers 109 [I-D.ietf-eai-utf8headers] is a new address type. The syntax for the 110 new address type in the context of status notifications follows: 112 An SMTP [RFC2821] server which advertises both the UTF8SMTP extension 113 [I-D.ietf-eai-smtpext] and the DSN extension [RFC3461] MUST accept a 114 UTF-8 address type in the ORCPT parameter including 8-bit UTF-8 115 characters. This address type also includes a 7-bit encoding 116 suitable for use in a message/delivery-status body part or an ORCPT 117 parameter sent to an SMTP server which does not advertise UTF8SMTP. 119 This address type has 3 forms: utf-8-addr-xtext, utf-8-addr-unitext 120 and utf-8-address. The first 2 forms are 7-bit safe. 122 The utf-8-address form is only suitable for use in newly defined 123 protocols capable of native representation of 8-bit characters. I.e. 124 the utf-8-address form MUST NOT be used in the ORCPT parameter when 125 the SMTP server doesn't advertise support for UTF8SMTP or the SMTP 126 server supports UTF8SMTP, but the address contains US-ASCII 127 characters not permitted in the ORCPT parameter (e.g. the ORCPT 128 parameter forbids unencoded SP and the = character); or in a 7-bit 129 transport environment including a message/delivery-status Original- 130 Recipient or Final-Recipient field. In the former case the utf-8- 131 addr-xtext form (see below) MUST be used instead, in the latter case 132 the utf-8-addr-unitext form MUST be used. The utf-8-address form MAY 133 be used in the ORCPT parameter when the SMTP server also advertises 134 support for UTF8SMTP and the address doesn't contains any US-ASCII 135 characters not permitted in the ORCPT parameter. It SHOULD be used 136 in a message/global-delivery-status Original-Recipient or Final- 137 Recipient DSN field; or in an Original-Recipient header field 138 [RFC3798] if the message is a UTF8SMTP message. 140 In addition, the utf-8-addr-unitext form can be used anywhere where 141 the utf-8-address form is allowed. 143 When using in the ORCPT parameter, the UTF-8 address type requires 144 that US-ASCII CTLs, SP, \, + and = be encoded using xtext encoding as 145 described in [RFC3461]. This is described by the utf-8-addr-xtext 146 form in the ABNF below. Unicode characters MAY be included in a 147 UTF-8 address type using a "\x{HEXPOINT}" syntax 148 (EmbeddedUnicodeChar), where HEXPOINT is 2 to 6 hexadecimal digits. 149 When sending data to a UTF8SMTP capable server, native UTF-8 150 characters SHOULD be used instead of the EmbeddedUnicodeChar syntax 151 described in details below. When sending data to an SMTP server 152 which does not advertise UTF8SMTP, then the EmbeddedUnicodeChar 153 syntax MUST be used instead of UTF-8. 155 When the ORCPT parameter is placed in a message/ 156 global-delivery-status Original-Recipient field, the utf-8-addr-xtext 157 form of the UTF-8 address type SHOULD be converted to the 'utf-8- 158 address' form (see the ABNF below) by removing all xtext encoding 159 first (which will result in the 'utf-8-addr-unitext' form), followed 160 by removal of the 'unitext' encoding. However, if an address is 161 labeled with the UTF-8 address type but does not conform to utf-8 162 syntax, then it MUST be copied into the message/ 163 global-delivery-status field without alteration. 165 The ability to encode characters with the EmbeddedUnicodeChar 166 encodings should be viewed as a transitional mechanism. It is hoped 167 that as systems lacking support for UTF8SMTP become less common over 168 time, these encodings can eventually be phased out. 170 utf-8-type-addr = "utf-8;" utf-8-enc-addr 172 utf-8-address = uMailbox [ 1*WSP "<" Mailbox ">" ] 173 ; 'uMailbox' is defined in [I-D.ietf-eai-smtpext]. 174 ; 'Mailbox' is defined in [RFC2821]. 176 utf-8-enc-addr = utf-8-addr-xtext / 177 utf-8-addr-unitext / 178 utf-8-address 180 ///Add comment about which where each type is used 182 utf-8-addr-xtext = xtext 183 ; xtext is defined in [RFC3461]. 184 ; When xtext encoding is removed, 185 ; the syntax MUST conform to 186 ; 'utf-8-addr-unitext'. 188 utf-8-addr-unitext = 1*(QUCHAR / EmbeddedUnicodeChar) 189 ; MUST follow 'utf-8-address' ABNF when 190 ; dequoted 192 QUCHAR = %x21-2a / %x2c-3c / %x3e-5b / %x5d-7e / 193 UTF8-2 / UTF8-3 / UTF8-4 194 ; US-ASCII printable characters except 195 ; CTLs, SP, '\', '+' and '=', plus 196 ; other Unicode characters in UTF-8 198 EmbeddedUnicodeChar = %x5C.78 "{" HEXPOINT "}" 199 ; starts with "\x" 201 HEXPOINT = "5C" / (HEXDIG8 HEXDIG) / ; 2 digit forms 202 ( NZHEXDIG 2(HEXDIG) ) / ; 3 digit forms 203 ( NZDHEXDIG 3(HEXDIG) ) / 204 ( "D" %x30-37 2(HEXDIG) ) / 205 ; 4 digit forms excluding surrogate 206 ( NZHEXDIG 4(HEXDIG) ) / ; 5 digit forms 207 ( "10" 4*HEXDIG ) ; 6 digit forms 208 ; represents either "\" or a Unicode code point outside the 209 ; US-ASCII repertoire 211 HEXDIG8 = %x38-39 / "A" / "B" / "C" / "D" / "E" / "F" 212 ; HEXDIG excluding 0-7 213 NZHEXDIG = %x31-39 / "A" / "B" / "C" / "D" / "E" / "F" 214 ; HEXDIG excluding "0" 215 NZDHEXDIG = %x31-39 / "A" / "B" / "C" / "E" / "F" 216 ; HEXDIG excluding "0" and "D" 218 4. UTF-8 Delivery Status Notifications 220 A traditional delivery status notification [RFC3464] comes in a 221 three-part multipart/report [RFC3462] container, where the first part 222 is human readable text describing the error, the second part is a 223 7-bit-only message/delivery-status and the optional third part is 224 used for content (message/rfc822) or header (text/rfc822-headers) 225 return. As the present DSN format does not permit returning of 226 undeliverable UTF8SMTP messages, three new media types are needed. 228 The first type, message/global-delivery-status has the syntax of 229 message/delivery-status with three modifications. First, the charset 230 for message/global-delivery-status is UTF-8 and thus any field MAY 231 contain UTF-8 characters when appropriate (see the ABNF below). In 232 particular, the Diagnostic-Code field MAY contain UTF-8 as described 233 in UTF8SMTP [I-D.ietf-eai-smtpext]; the Diagnostic-Code field SHOULD 234 be in i-default language [DEFAULTLANG]. Second, systems generating a 235 message/global-delivery-status body part SHOULD use the utf-8-address 236 form of the UTF-8 address type for all addresses containing 237 characters outside the US-ASCII repertoire. These systems SHOULD up- 238 convert the utf-8-addr-xtext or the utf-8-addr-unitext form of a 239 UTF-8 address type in the ORCPT parameter to the utf-8-address form 240 of a UTF-8 address type in the Original-Recipient field. Third, a 241 new optional field called Localized-Diagnostic is added. Each 242 instance includes a language tag [LANGTAGS] and contains text in the 243 specified language. This is equivalent to the text part of the 244 Diagnostic-Code field. All instances of Localized-Diagnostic MUST 245 use different language tags. The ABNF for message/ 246 global-delivery-status is specified below: 248 utf-8-delivery-status-content = per-message-fields 249 1*( CRLF utf-8-per-recipient-fields ) 250 ; "per-message-fields" remains unchanged from the definition 251 ; in RFC 3464, except for the "extension-field" 252 ; which is updated below. 254 utf-8-per-recipient-fields = 255 [ original-recipient-field CRLF ] 256 final-recipient-field CRLF 257 action-field CRLF 258 status-field CRLF 259 [ remote-mta-field CRLF ] 260 [ diagnostic-code-field CRLF 261 *(localized-diagnostic-text-field CRLF) ] 262 [ last-attempt-date-field CRLF ] 263 [ will-retry-until-field CRLF ] 264 *( extension-field CRLF ) 265 ; All fields except for "original-recipient-field", 266 ; "final-recipient-field", "diagnostic-code-field" 267 ; and "extension-field" remain unchanged from 268 ; the definition in RFC 3464. 270 generic-address =/ utf-8-enc-addr 271 ; Only allowed with the "utf-8" address-type. 272 ; 273 ; This indirectly updates "original-recipient-field" 274 ; and "final-recipient-field" 276 diagnostic-code-field = 277 "Diagnostic-Code" ":" diagnostic-type ";" *text 279 localized-diagnostic-text-field = 280 "Localized-Diagnostic" ":" Language-Tag ";" *utf8-text 281 ; "Language-Tag" is a language tag as defined in [LANGTAGS]. 283 extension-field =/ extension-field-name ":" *utf8-text 285 utf8-text = %d1-9 / ; Any Unicode character except for NUL, 286 %d11 / ; CR and LF, encoded in UTF-8 287 %d12 / 288 %d14-127 / 289 UTFMB 291 UTFMB = UTF2 / UTF3 / UTF4 293 The second type, used for returning the content, is message/global 294 which is similar to message/rfc822, except it contains a message with 295 UTF-8 headers. This media type is described in 297 [I-D.ietf-eai-utf8headers]. 299 The third type, used for returning the headers, is message/ 300 global-headers and contains only the UTF-8 header fields of a message 301 (all lines prior to the first blank line in a UTF8SMTP message). 302 Unlike message/global, this body part provides no difficulties for 303 present infrastructure. 305 Note, that as far as multipart/report [RFC3462] container is 306 concerned, message/global-delivery-status, message/global and 307 message/global-headers MUST be treated as equivalent to message/ 308 delivery-status, message/rfc822 and text/rfc822-headers. I.e. 309 implementations processing multipart/report MUST expect any 310 combinations of the 6 MIME types mentioned above inside a multipart/ 311 report MIME type. 313 All three new types will typically use the "8bit" Content-Transfer- 314 Encoding. (In the event all content is 7-bit, the equivalent 315 traditional types for delivery status notifications MAY be used. For 316 example, if information in message/global-delivery-status part can be 317 represented without any loss of information as message/ 318 delivery-status, then the message/delivery-status body part may be 319 used.) Note that [I-D.ietf-eai-utf8headers] relaxed restriction from 320 MIME [RFC2046] regarding use of Content-Transfer-Encoding in new 321 "message" subtypes. This specification explicitly allows use of 322 Content-Transfer-Encoding in message/global-headers and message/ 323 global-delivery-status. This is not believed to be problematic as 324 these new MIME types are intended primarily for use by newer systems 325 with full support for 8-bit MIME and UTF-8 headers. 327 4.1. Additional requirements on SMTP servers 329 If an SMTP server which advertises both UTF8SMTP and DSN needs to 330 return an undeliverable UTF8SMTP message, then it MUST NOT downgrade 331 [I-D.ietf-eai-downgrade] the UTF8SMTP message when generating the 332 corresponding multipart/report. If the return path SMTP server does 333 not support UTF8SMTP, then the undeliverable body part and headers 334 MUST be encoded using a 7 bit Content-Transfer-Encoding such as 335 base64 or quoted-printable [RFC2045], as detailed in Section 4. 336 Otherwise 8bit Content-Transfer-Encoding can be used. 338 5. UTF-8 Message Disposition Notifications 340 Message Disposition Notifications [RFC3798] have a similar design and 341 structure to DSNs. As a result, they use the same basic return 342 format. When generating a MDN for a UTF-8 header message, the third 343 part of the multipart/report contains the returned content (message/ 344 global) or header (message/global-headers), same as for DSNs. The 345 second part of the multipart/report uses a new media type, message/ 346 global-disposition-notification, which has the syntax of message/ 347 disposition-notification with two modifications. First, the charset 348 for message/global-disposition-notification is UTF-8 and thus any 349 field MAY contain UTF-8 characters when appropriate (see the ABNF 350 below). (In particular, the failure-field, the error-field and the 351 warning-field MAY contain UTF-8. These fields SHOULD be in i-default 352 language [DEFAULTLANG].) Second, systems generating a message/ 353 global-disposition-notification body part (typically a mail user 354 agent) SHOULD use the UTF-8 address type for all addresses containing 355 characters outside the US-ASCII repertoire. 357 The MDN specification also defines the Original-Recipient header 358 field which is added with a copy of the contents of ORCPT at delivery 359 time. When generating an Original-Recipient header field, a delivery 360 agent writing a UTF-8 header message in native format SHOULD convert 361 the utf-8-addr-xtext or the utf-8-addr-unitext form of a UTF-8 362 address type in the ORCPT parameter to the corresponding utf-8- 363 address form. 365 The MDN specification also defines the Disposition-Notification-To 366 header which is an address header and thus follows the same 8-bit 367 rules as other address headers such as "From" and "To" when used in a 368 UTF-8 header message. 370 ; ABNF for "original-recipient-header", "original-recipient-field" 371 ; and "final-recipient-field" from RFC 3798 is implicitly updated 372 ; as they use the updated "generic-address" as defined in 373 ; section 4 of this document. 375 failure-field = "Failure" ":" *utf8-text 376 ; "utf8-text" is defined in section 4 of this document. 378 error-field = "Error" ":" *utf8-text 379 ; "utf8-text" is defined in section 4 of this document. 381 warning-field = "Warning" ":" *utf8-text 382 ; "utf8-text" is defined in section 4 of this document. 384 6. IANA Considerations 386 This specification does not create any new IANA registries. However 387 the following items are registered as a result of this document: 389 6.1. UTF-8 Mail Address Type Registration 391 The mail address type registry was created by RFC 3464. The 392 registration template response follows: 394 (a) The proposed address-type name. 396 UTF-8 398 (b) The syntax for mailbox addresses of this type, specified using 399 BNF, regular expressions, ASN.1, or other non-ambiguous language. 401 See Section 3. 403 (c) If addresses of this type are not composed entirely of graphic 404 characters from the US-ASCII repertoire, a specification for how they 405 are to be encoded as graphic US-ASCII characters in a DSN Original- 406 Recipient or Final-Recipient DSN field. 408 This address type has 3 forms (as defined in Section 3): utf-8-addr- 409 xtext, utf-8-addr-unitext and utf-8-address. The first 2 forms are 410 7-bit safe. 412 The utf-8-address form MUST NOT be used 414 1. in the ORCPT parameter when the SMTP server doesn't advertise 415 support for UTF8SMTP 417 2. or the SMTP server supports UTF8SMTP, but the address contains 418 US-ASCII characters not permitted in the ORCPT parameter (e.g. 419 the ORCPT parameter forbids SP and the = characters); 421 3. or in a 7-bit transport environment including a message/ 422 delivery-status Original-Recipient or Final-Recipient field. 424 The utf-8-addr-xtext form MUST be used instead in the first case, the 425 utf-8-addr-unitext form MUST be used in the other two cases. The 426 utf-8-address form MAY be used in the ORCPT parameter when the SMTP 427 server also advertises support for UTF8SMTP and the address doesn't 428 contains any US-ASCII characters not permitted in the ORCPT 429 parameter; in a message/global-delivery-status Original-Recipient or 430 Final-Recipient DSN field; or in an Original-Recipient header field 431 [RFC3798] if the message is a UTF8SMTP message. 433 In addition, the utf-8-addr-unitext form can be used anywhere where 434 the utf-8-address form is allowed. 436 6.2. Update to 'smtp' Diagnostic Type Registration 438 The mail diagnostic type registry was created by RFC 3464. The 439 registration for the 'smtp' diagnostic type should be updated to 440 reference RFC XXXX in addition to RFC 3464. 442 When the 'smtp' diagnostic type is used in the context of a message/ 443 delivery-status body part, it remains as presently defined. When the 444 'smtp' diagnostic type is used in the context of a message/ 445 global-delivery-status body part, the codes remain the same, but the 446 text portion MAY contain UTF-8 characters. 448 6.3. message/global-headers 450 Type name: message 452 Subtype name: global-headers 454 Required parameters: none 456 Optional parameters: none 458 Encoding considerations: This media type contains Internationalized 459 Email Headers [I-D.ietf-eai-utf8headers] with no message body. 460 Whenever possible, the 8-bit content transfer encoding SHOULD be 461 used. When this media type passes through a 7-bit-only SMTP 462 infrastructure it MAY be encoded with the base64 or quoted- 463 printable content transfer encoding. 465 Security considerations: See Section 7 467 Interoperability considerations: It is important this media type is 468 not converted to a charset other than UTF-8. As a result, 469 implementations MUST NOT include a charset parameter with this 470 media type. Although it might be possible to downconvert this 471 media type to the text/rfc822-header media type, such conversion 472 is discouraged as it loses information. 474 Published specification: RFC XXXX 476 Applications that use this media type: UTF8SMTP servers and email 477 clients that support multipart/report generation or parsing. 479 Additional information: 481 Magic number(s): none 483 File extension(s): In the event this is saved to a file, the 484 extension ".u8hdr" is suggested. 486 Macintosh file type code(s): The 'TEXT' type code is suggested as 487 files of this type are typically used for diagnostic purposes and 488 suitable for analysis in a UTF-8 aware text editor. A uniform 489 type identifier (UTI) of "public.utf8-email-message-header" is 490 suggested. This type conforms to "public.utf8-plain-text" and 491 "public.plain-text". 493 Person & email address to contact for further information: See the 494 Author's address section of this document. 496 Intended usage: COMMON 498 Restrictions on usage: This media type contains textual data in the 499 UTF-8 charset. It typically contains octets with the 8th bit set. 500 As a result a transfer encoding is required when a 7-bit transport 501 is used. 503 Author: See Author's Address section of this document. 505 Change controller: IETF Standards Process 507 6.4. message/global-delivery-status 509 Type name: message 511 Subtype name: global-delivery-status 513 Required parameters: none 515 Optional parameters: none 517 Encoding considerations: This media type contains delivery status 518 notification attributes in the UTF-8 charset. The 8-bit content 519 transfer encoding MUST be used with this content-type, unless it 520 is sent over a 7-bit transport environment in which case quoted- 521 printable or base64 may be necessary. 523 Security considerations: See Section 7 524 Interoperability considerations: This media type provides 525 functionality similar to the message/delivery-status content type 526 for email message return information. Clients of the previous 527 format will need to be upgraded to interpret the new format, 528 however the new media type makes it simple to identify the 529 difference. 531 Published specification: RFC XXXX 533 Applications that use this media type: SMTP servers and email 534 clients that support delivery status notification generation or 535 parsing. 537 Additional information: 539 Magic number(s): none 541 File extension(s): The extension ".u8dsn" is suggested. 543 Macintosh file type code(s): A uniform type identifier (UTI) of 544 "public.utf8-email-message-delivery-status" is suggested. This 545 type conforms to "public.utf8-plain-text". 547 Person & email address to contact for further information: See the 548 Author's address section of this document. 550 Intended usage: COMMON 552 Restrictions on usage: This is expected to be the second part of a 553 multipart/report. 555 Author: See Author's Address section of this document. 557 Change controller: IETF Standards Process 559 6.5. message/global-disposition-notification 561 Type name: message 563 Subtype name: global-disposition-notification 565 Required parameters: none 567 Optional parameters: none 568 Encoding considerations: This media type contains disposition 569 notification attributes in the UTF-8 charset. The 8-bit content 570 transfer encoding MUST be used with this content-type, unless it 571 is sent over a 7-bit transport environment in which case quoted- 572 printable or base64 may be necessary. 574 Security considerations: See Section 7 576 Interoperability considerations: This media type provides 577 functionality similar to the message/disposition-notification 578 content type for email message disposition information. Clients 579 of the previous format will need to be upgraded to interpret the 580 new format, however the new media type makes it simple to identify 581 the difference. 583 Published specification: RFC XXXX 585 Applications that use this media type: Email clients or servers that 586 support message disposition notification generation or parsing. 588 Additional information: 590 Magic number(s): none 592 File extension(s): The extension ".u8mdn" is suggested. 594 Macintosh file type code(s): A uniform type identifier (UTI) of 595 "public.utf8-email-message-disposition-notification" is suggested. 596 This type conforms to "public.utf8-plain-text". 598 Person & email address to contact for further information: See the 599 Author's address section of this document. 601 Intended usage: COMMON 603 Restrictions on usage: This is expected to be the second part of a 604 multipart/report. 606 Author: See Author's Address section of this document. 608 Change controller: IETF Standards Process 610 7. Security Considerations 612 Automated use of report types without authentication presents several 613 security issues. Forging negative reports presents the opportunity 614 for denial-of-service attacks when the reports are used for automated 615 maintenance of directories or mailing lists. Forging positive 616 reports may cause the sender to incorrectly believe a message was 617 delivered when it was not. 619 Malicious users can generate report structures designed to trigger 620 coding flaws in report parsers. Report parsers need to use secure 621 coding techniques to avoid the risk of buffer overflow or denial-of- 622 service attacks against parser coding mistakes. Code reviews of such 623 parsers are also recommended. 625 Malicious users of the email system regularly send messages with 626 forged envelope return paths and these messages trigger delivery 627 status reports that result in a large amount of unwanted traffic on 628 the Internet. Many users choose to ignore delivery status 629 notifications because they are usually the result of "blowback" from 630 forged messages and thus never notice when messages they sent go 631 undelivered. As a result, support for correlation of delivery status 632 and message disposition notification messages with sent-messages has 633 become a critical feature of mail clients and possibly mail stores if 634 the email infrastructure is to remain reliable. In the short term, 635 simply correlating message-IDs may be sufficient to distinguish true 636 status notifications from those resulting from forged originator 637 addresses. But in the longer term, including cryptographic signature 638 material that can securely associate the status notification with the 639 original message is advisable. 641 As this specification permits UTF-8 in additional fields, the 642 security considerations of UTF-8 [RFC3629] apply. 644 8. References 646 8.1. Normative References 648 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 649 Requirement Levels", BCP 14, RFC 2119, March 1997. 651 [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, 652 April 2001. 654 [RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service 655 Extension for Delivery Status Notifications (DSNs)", 656 RFC 3461, January 2003. 658 [RFC3462] Vaudreuil, G., "The Multipart/Report Content Type for the 659 Reporting of Mail System Administrative Messages", 660 RFC 3462, January 2003. 662 [RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format 663 for Delivery Status Notifications", RFC 3464, 664 January 2003. 666 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 667 10646", STD 63, RFC 3629, November 2003. 669 [RFC3798] Hansen, T. and G. Vaudreuil, "Message Disposition 670 Notification", RFC 3798, May 2004. 672 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 673 Specifications: ABNF", RFC 4234, October 2005. 675 [I-D.ietf-eai-utf8headers] 676 Yang, A., "Internationalized Email Headers", 677 draft-ietf-eai-utf8headers-07 (work in progress), 678 April 2007. 680 [I-D.ietf-eai-smtpext] 681 Yao, J. and W. Mao, "SMTP extension for internationalized 682 email address", draft-ietf-eai-smtpext-08 (work in 683 progress), April 2007. 685 [LANGTAGS] 686 Phillips, A. and M. Davis, "Tags for Identifying 687 Languages", RFC 4646, September 2006. 689 [DEFAULTLANG] 690 Alvestrand, H., "IETF Policy on Character Sets and 691 Languages", RFC 2277, January 1998. 693 8.2. Informative References 695 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 696 Extensions (MIME) Part One: Format of Internet Message 697 Bodies", RFC 2045, November 1996. 699 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 700 Extensions (MIME) Part Two: Media Types", RFC 2046, 701 November 1996. 703 [I-D.ietf-eai-downgrade] 704 Yoneya, Y. and K. Fujiwara, "Downgrading mechanism for 705 Email Address Internationalization (EAI)", 706 draft-ietf-eai-downgrade-04 (work in progress), Mar 2007. 708 Appendix A. Acknowledgements 710 Many thanks for input provided by Pete Resnick, James Galvin, Ned 711 Freed, John Klensin, Harald Alvestrand, Frank Ellermann and members 712 of the EAI WG to help solidify this proposal. 714 Appendix B. Changes from -02 716 Make the space between UTF-8 and ASCII address mandatory. 718 Appendix C. Changes from -01 720 Cleaned up and tightened ABNF, in particular HEXPOINT. 722 Extended DSN report syntax to allow for localized version of 723 diagnostic-code-field. 725 Added ABNF for the EAI DSN and EAI MDN. 727 Appendix D. Changes from -00 729 Added paragraph about use of 8bit Content-Transfer-Encoding for new 730 message sub-types. 732 Updated the list of open issues. 734 Clarified that this document is targeted to become an Experimental 735 RFC. 737 Made the EAI downgrade document a normative reference. 739 Updated ABNF for utf-8-address. 741 Authors' Addresses 743 Chris Newman 744 Sun Microsystems 745 3401 Centrelake Dr., Suite 410 746 Ontario, CA 91761 747 US 749 Email: chris.newman@sun.com 750 Alexey Melnikov (editor) 751 Isode Ltd 752 5 Castle Business Village 753 36 Station Road 754 Hampton, Middlesex TW12 2BX 755 UK 757 Email: Alexey.Melnikov@isode.com 759 Full Copyright Statement 761 Copyright (C) The IETF Trust (2007). 763 This document is subject to the rights, licenses and restrictions 764 contained in BCP 78, and except as set forth therein, the authors 765 retain all their rights. 767 This document and the information contained herein are provided on an 768 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 769 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 770 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 771 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 772 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 773 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 775 Intellectual Property 777 The IETF takes no position regarding the validity or scope of any 778 Intellectual Property Rights or other rights that might be claimed to 779 pertain to the implementation or use of the technology described in 780 this document or the extent to which any license under such rights 781 might or might not be available; nor does it represent that it has 782 made any independent effort to identify any such rights. 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