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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 12, 2016) is 2750 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-24) exists of draft-ietf-slim-negotiating-human-language-04 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IETF N. Tomkinson 3 Internet-Draft N. Borenstein 4 Intended status: Standards Track Mimecast Ltd 5 Expires: April 15, 2017 October 12, 2016 7 Multiple Language Content Type 8 draft-ietf-slim-multilangcontent-06 10 Abstract 12 This document defines an addition to the Multipurpose Internet Mail 13 Extensions (MIME) standard to make it possible to send one message 14 that contains multiple language versions of the same information. 15 The translations would be identified by a language tag and selected 16 by the email client based on a user's language settings. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on April 15, 2017. 35 Copyright Notice 37 Copyright (c) 2016 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 1. Introduction 52 Since the invention of email and the rapid spread of the Internet, 53 more and more people have been able to communicate in more and more 54 countries and in more and more languages. But during this time of 55 technological evolution, email has remained a single-language 56 communication tool, whether it is English to English, Spanish to 57 Spanish or Japanese to Japanese. 59 Also during this time, many corporations have established their 60 offices in multi-cultural cities and formed departments and teams 61 that span continents, cultures and languages, so the need to 62 communicate efficiently with little margin for miscommunication has 63 grown significantly. 65 The objective of this document is to define an addition to the 66 Multipurpose Internet Mail Extensions (MIME) standard, to make it 67 possible to send a single message to a group of people in such a way 68 that all of the recipients can read the email in their preferred 69 language. The methods of translation of the message content are 70 beyond the scope of this document, but the structure of the email 71 itself is defined herein. 73 Whilst this document depends on identification of language in message 74 parts for non-real-time communication, there is a companion document 75 that is concerned with a similar problem for real-time communication: 76 [I-D.ietf-slim-negotiating-human-language] 78 1.1. Requirements Language 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in RFC 2119 [RFC2119]. 84 2. The Content-Type Header Field 86 The "multipart/multilingual" MIME subtype allows the sending of a 87 message in a number of different languages with the translations 88 embedded in the same message. This MIME subtype helps the receiving 89 email client make sense of the message structure. 91 The multipart subtype "multipart/multilingual" has similar semantics 92 to "multipart/alternative" (as discussed in RFC 2046 [RFC2046]) in 93 that each of the message parts is an alternative version of the same 94 information. The primary difference between "multipart/multilingual" 95 and "multipart/alternative" is that when using "multipart/ 96 multilingual", the message part to select for rendering is chosen 97 based on the values of the Content-Language field and optionally the 98 Translation-Type field instead of the ordering of the parts and the 99 Content-Types. 101 The syntax for this multipart subtype conforms to the common syntax 102 for subtypes of multipart given in section 5.1.1. of RFC 2046 103 [RFC2046]. An example "multipart/multilingual" Content-Type header 104 field would look like this: 106 Content-Type: multipart/multilingual; boundary=01189998819991197253 108 3. The Message Parts 110 A multipart/multilingual message will have a number of message parts: 111 exactly one multilingual preface, one or more language message parts 112 and zero or one language independent message part. The details of 113 these are described below. 115 3.1. The Multilingual Preface 117 In order for the message to be received and displayed in non- 118 conforming email clients, the message SHOULD contain an explanatory 119 message part which MUST NOT be marked with a Content-Language field 120 and MUST be the first of the message parts. For maximum support in 121 the most basic of non-conforming email clients, it SHOULD have a 122 Content-Type of text/plain. Because non-conforming email clients are 123 expected to treat a message with an unknown multipart type as 124 multipart/mixed (in accordance with sections 5.1.3 and 5.1.7 of RFC 125 2046 [RFC2046]) they may show all of the message parts sequentially 126 or as attachments. Including and showing this explanatory part will 127 help the message recipient understand the message structure. 129 This initial message part SHOULD explain briefly to the recipient 130 that the message contains multiple languages and the parts may be 131 rendered sequentially or as attachments. This SHOULD be presented in 132 the same languages that are provided in the subsequent language 133 message parts. 135 As this explanatory section is likely to contain languages using 136 scripts that require non-US-ASCII characters, it is RECOMMENDED that 137 UTF-8 encoding is used for this message part. 139 Whilst this section of the message is useful for backward 140 compatibility, it will normally only be shown when rendered by a non- 141 conforming email client, because conforming email clients SHOULD only 142 show the single language message part identified by the user's 143 preferred language and the language message part's Content-Language. 145 For the correct display of the multilingual preface in a non- 146 conforming email client, the sender MAY use the Content-Disposition 147 field with a value of 'inline' in conformance with RFC 2183 [RFC2183] 148 (which defines the Content-Disposition field). If provided, this 149 SHOULD be placed at the multipart/multilingual level and in the 150 multilingual preface. This makes it clear to a non-conforming email 151 client that the multilingual preface should be displayed immediately 152 to the recipient, followed by any subsequent parts marked as 153 'inline'. 155 For an example of a multilingual preface, see the examples in 156 Section 8. 158 3.2. The Language Message Parts 160 The language message parts are typically translations of the same 161 message content. These message parts SHOULD be ordered so that the 162 first part after the multilingual preface is in the language believed 163 to be the most likely to be recognised by the recipient as this will 164 constitute the default part when language negotiation fails and there 165 is no Language Independent part. All of the language message parts 166 MUST have a Content-Language field and a Content-Type field and MAY 167 have a Translation-Type field. 169 The Content-Type for each individual language message part SHOULD be 170 message/rfc822 to provide good support with non-conforming email 171 clients. However, an implementation MAY use message/global as 172 support for message/global becomes more commonplace. See RFC 6532 173 [RFC6532] for details of message/global. Each language message part 174 SHOULD have a Subject field in the appropriate language for that 175 language part. If there is a From field present, its value MUST 176 include the same email address as the top-level From header although 177 the display name MAY be a localised version. 179 3.3. The Language Independent Message Part 181 If there is language independent content intended for the recipient 182 to see if they have a preferred language other than one of those 183 specified in the language message parts and the default language 184 message part is unlikely to be understood, another part MAY be 185 provided. This could typically be a language independent graphic. 186 When this part is present, it MUST be the last part, MUST have a 187 Content-Language field with a value of "zxx" (as described in BCP 47/ 188 RFC 5646 [RFC5646]) and SHOULD NOT have a Subject field and SHOULD 189 NOT have a From field. The part SHOULD have a Content-Type of 190 message/rfc822 or message/global (to match the language message 191 parts). 193 4. Message Part Selection 195 The logic for selecting the message part to render and present to the 196 recipient is summarised in the next few paragraphs. 198 Firstly, if the email client does not understand multipart/ 199 multilingual then it should treat the message as if it was multipart/ 200 mixed and render message parts accordingly. 202 If the email client does understand multipart/multilingual then it 203 SHOULD ignore the multilingual preface and select the best match for 204 the user's preferred language from the language message parts 205 available. Also, the user may prefer to see the original message 206 content in their second language over a machine translation in their 207 first language. The Translation-Type field value can be used for 208 further selection based on this preference. The selection of 209 language part may be implemented in a variety of ways, although the 210 matching schemes detailed in RFC 4647 [RFC4647] are RECOMMENDED as a 211 starting point for an implementation. The goal is to render the most 212 appropriate translation for the user. 214 If there is no match for the user's preferred language (or there is 215 no preferred language information available) the email client SHOULD 216 select the language independent part (if one exists) or the first 217 language part (directly after the multilingual preface) if a language 218 independent part does not exist. 220 If there is no translation type preference information available, the 221 values of the Translation-Type field may be ignored. 223 Additionally, interactive implementations MAY offer the user a choice 224 from among the available languages. 226 5. The Content-Language Field 228 The Content-Language field in the individual language message parts 229 is used to identify the language in which the message part is 230 written. Based on the value of this field, a conforming email client 231 can determine which message part to display (given the user's 232 language settings). 234 The Content-Language MUST comply with RFC 3282 [RFC3282] (which 235 defines the Content-Language field) and BCP 47/RFC 5646 [RFC5646] 236 (which defines the structure and semantics for the language code 237 values). 239 Examples of this field for English, German and an instruction manual 240 in Spanish and French, could look like the following: 242 Content-Language: en 244 Content-Language: de 246 Content-Language: es, fr 248 6. The Translation-Type Field 250 The Translation-Type field can be used in the individual language 251 message parts to identify the type of translation. Based on the 252 value of this parameter and the user's preferences, a conforming 253 email client can determine which message part to display. 255 This field can have one of three possible values: 'original', 'human' 256 or 'automated' although other values may be added in the future. A 257 value of 'original' is given in the language message part that is in 258 the original language. A value of 'human' is used when a language 259 message part is translated by a human translator or a human has 260 checked and corrected an automated translation. A value of 261 'automated' is used when a language message part has been translated 262 by an electronic agent without proofreading or subsequent correction. 264 Examples of this field include: 266 Translation-Type: original 268 Translation-Type: human 270 7. The Subject Field in the Language Message parts 272 On receipt of the message, conforming email clients will need to 273 render the subject in the correct language for the recipient. To 274 enable this the Subject field SHOULD be provided in each language 275 message part. The value for this field should be a translation of 276 the email subject. 278 US-ASCII and 'encoded-word' examples of this field include: 280 Subject: A really simple email subject 282 Subject: =?UTF-8?Q?Un_asunto_de_correo_electr=C3=b3nico_ 283 realmente_sencillo?= 285 See RFC 2047 [RFC2047] for the specification of 'encoded-word'. 287 The subject to be presented to the recipient should be selected from 288 the message part identified during the message part selection stage. 289 If no Subject field is found (for example if the language independent 290 part is selected) the top-level Subject header field value should be 291 used. 293 8. Examples 295 8.1. An Example of a Simple Multiple language email message 297 Below is a minimal example of a multiple language email message. It 298 has the multilingual preface and two language message parts. 300 From: Nik@example.com 301 To: Nathaniel@example.com 302 Subject: Example of a message in Spanish and English 303 Date: Thu, 7 Jul 2016 21:28:00 +0100 304 MIME-Version: 1.0 305 Content-Type: multipart/multilingual; 306 boundary="01189998819991197253" 308 --01189998819991197253 309 Content-Type: text/plain; charset="UTF-8" 310 Content-Disposition: inline 311 Content-Transfer-Encoding: quoted-printable 313 This is a message in multiple languages. It says the 314 same thing in each language. If you can read it in one language, 315 you can ignore the other translations. The other translations may be 316 presented as attachments or grouped together. 318 Este es un mensaje en varios idiomas. Dice lo mismo en 319 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 320 traducciones. Las otras traducciones pueden presentarse como archivos 321 adjuntos o agrupados. 323 --01189998819991197253 324 Content-Type: message/rfc822 325 Content-Language: en 326 Translation-Type: original 327 Content-Disposition: inline 329 Subject: Example of a message in Spanish and English 330 Content-Type: text/plain; charset="US-ASCII" 331 Content-Transfer-Encoding: 7bit 332 MIME-Version: 1.0 334 Hello, this message content is provided in your language. 336 --01189998819991197253 337 Content-Type: message/rfc822 338 Content-Language: es 339 Translation-Type: human 340 Content-Disposition: inline 342 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 343 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 344 Content-Type: text/plain; charset="US-ASCII" 345 Content-Transfer-Encoding: 7bit 346 MIME-Version: 1.0 348 Hola, el contenido de este mensaje esta disponible en su idioma. 350 --01189998819991197253-- 352 8.2. An Example of a Multiple language email message with language 353 independent part 355 Below is an example of a multiple language email message that has the 356 multilingual preface followed by two language message parts and then 357 a language independent png image. 359 From: Nik@example.com 360 To: Nathaniel@example.com 361 Subject: Example of a message in Spanish and English 362 Date: Thu, 7 Jul 2016 21:08:00 +0100 363 MIME-Version: 1.0 364 Content-Type: multipart/multilingual; 365 boundary="01189998819991197253" 367 --01189998819991197253 368 Content-Type: text/plain; charset="UTF-8" 369 Content-Disposition: inline 370 Content-Transfer-Encoding: quoted-printable 372 This is a message in multiple languages. It says the 373 same thing in each language. If you can read it in one language, 374 you can ignore the other translations. The other translations may be 375 presented as attachments or grouped together. 377 Este es un mensaje en varios idiomas. Dice lo mismo en 378 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 379 traducciones. Las otras traducciones pueden presentarse como archivos 380 adjuntos o agrupados. 382 --01189998819991197253 383 Content-Type: message/rfc822 384 Content-Language: en 385 Translation-Type: original 386 Content-Disposition: inline 388 Subject: Example of a message in Spanish and English 389 Content-Type: text/plain; charset="US-ASCII" 390 Content-Transfer-Encoding: 7bit 391 MIME-Version: 1.0 393 Hello, this message content is provided in your language. 395 --01189998819991197253 396 Content-Type: message/rfc822 397 Content-Language: es 398 Translation-Type: human 399 Content-Disposition: inline 401 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 402 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 403 Content-Type: text/plain; charset="US-ASCII" 404 Content-Transfer-Encoding: 7bit 405 MIME-Version: 1.0 407 Hola, el contenido de este mensaje esta disponible en su idioma. 409 --01189998819991197253 410 Content-Type: message/rfc822; name="Icon" 411 Content-Language: zxx 412 Content-Disposition: inline 414 Content-Type: multipart/mixed; 415 boundary="99911972530118999881"; charset="US-ASCII" 416 Content-Transfer-Encoding: 7bit 417 MIME-Version: 1.0 419 --99911972530118999881 420 Content-Type: image/png; name="icon.png" 421 Content-Disposition: inline 422 Content-Transfer-Encoding: base64 424 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 425 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 426 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 428 --99911972530118999881-- 429 --01189998819991197253-- 430 8.3. An Example of a complex Multiple language email message with 431 language independent part 433 Below is an example of a more complex multiple language email 434 message. It has the multilingual preface and two language message 435 parts and then a language independent png image. The language 436 message parts have multipart/alternative contents and would therefore 437 require further processing to determine the content to display. 439 From: Nik@example.com 440 To: Nathaniel@example.com 441 Subject: Example of a message in Spanish and English 442 Date: Thu, 7 Jul 2016 20:55:00 +0100 443 MIME-Version: 1.0 444 Content-Type: multipart/multilingual; 445 boundary="01189998819991197253" 447 --01189998819991197253 448 Content-Type: text/plain; charset="UTF-8" 449 Content-Disposition: inline 450 Content-Transfer-Encoding: quoted-printable 452 This is a message in multiple languages. It says the 453 same thing in each language. If you can read it in one language, 454 you can ignore the other translations. The other translations may be 455 presented as attachments or grouped together. 457 Este es un mensaje en varios idiomas. Dice lo mismo en 458 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 459 traducciones. Las otras traducciones pueden presentarse como archivos 460 adjuntos o agrupados. 462 --01189998819991197253 463 Content-Type: message/rfc822 464 Content-Language: en 465 Translation-Type: original 466 Content-Disposition: inline 468 Subject: Example of a message in Spanish and English 469 Content-Type: multipart/alternative; 470 boundary="72530118999911999881"; charset="US-ASCII" 471 Content-Transfer-Encoding: 7bit 472 MIME-Version: 1.0 474 --72530118999911999881 475 Content-Type: text/plain; charset="US-ASCII" 476 Content-Transfer-Encoding: 7bit 477 Hello, this message content is provided in your language. 479 --72530118999911999881 480 Content-Type: text/html; charset="US-ASCII" 481 Content-Transfer-Encoding: 7bit 483 Hello, this message content is provided in your language. 485 --72530118999911999881-- 486 --01189998819991197253 487 Content-Type: message/rfc822 488 Content-Language: es 489 Translation-Type: human 490 Content-Disposition: inline 492 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 493 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 494 Content-Type: multipart/alternative; 495 boundary="53011899989991197281"; charset="US-ASCII" 496 Content-Transfer-Encoding: 7bit 497 MIME-Version: 1.0 499 --53011899989991197281 500 Content-Type: text/plain; charset="US-ASCII" 501 Content-Transfer-Encoding: 7bit 503 Hola, el contenido de este mensaje esta disponible en su idioma. 505 --53011899989991197281 506 Content-Type: text/html; charset="US-ASCII" 507 Content-Transfer-Encoding: 7bit 509 Hola, el contenido de este mensaje esta 510 disponible en su idioma. 512 --53011899989991197281-- 513 --01189998819991197253 514 Content-Type: message/rfc822; name="Icon" 515 Content-Language: zxx 516 Content-Disposition: inline 518 Content-Type: multipart/mixed; 519 boundary="99911972530118999881"; charset="US-ASCII" 520 Content-Transfer-Encoding: 7bit 521 MIME-Version: 1.0 523 --99911972530118999881 524 Content-Type: image/png; name="icon.png" 525 Content-Disposition: inline 526 Content-Transfer-Encoding: base64 528 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 529 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 530 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 532 --99911972530118999881-- 533 --01189998819991197253-- 535 9. Changes from Previous Versions 537 9.1. Changes from draft-tomkinson-multilangcontent-01 to draft- 538 tomkinson-slim-multilangcontent-00 540 o File name and version number changed to reflect the proposed WG 541 name SLIM (Selection of Language for Internet Media). 543 o Replaced the Subject-Translation field in the language message 544 parts with Subject and provided US-ASCII and non-US-ASCII 545 examples. 547 o Introduced the language-independent message part. 549 o Many wording improvements and clarifications throughout the 550 document. 552 9.2. Changes from draft-tomkinson-slim-multilangcontent-00 to draft- 553 tomkinson-slim-multilangcontent-01 555 o Added Translation-Type in each language message part to identify 556 the source of the translation (original/human/automated). 558 9.3. Changes from draft-tomkinson-slim-multilangcontent-01 to draft- 559 tomkinson-slim-multilangcontent-02 561 o Changed Translation-Type to be a parameter for the Content- 562 Language field rather than a new separate field. 564 o Added a paragraph about using Content-Disposition field to help 565 non-conforming mail clients correctly render the multilingual 566 preface. 568 o Recommended using a Name parameter on the language part Content- 569 Type to help the recipient identify the translations in non- 570 conforming mail clients. 572 o Many wording improvements and clarifications throughout the 573 document. 575 9.4. Changes from draft-tomkinson-slim-multilangcontent-02 to draft- 576 ietf-slim-multilangcontent-00 578 o Name change to reflect the draft being accepted into SLIM as a 579 working group document. 581 o Updated examples to use UTF-8 encoding where required. 583 o Removed references to 'locale' for identifying language 584 preference. 586 o Recommended language matching schemes from RFC 4647 [RFC4647]. 588 o Renamed the unmatched part to language independent part to 589 reinforce its intended purpose. 591 o Added requirement for using Content-Language: zxx in the language 592 independent part. 594 o Many wording improvements and clarifications throughout the 595 document. 597 9.5. Changes from draft-ietf-slim-multilangcontent-00 to draft-ietf- 598 slim-multilangcontent-01 600 o Changed the inner content type to require message/rfc822 or 601 message/global. 603 o Updated the examples to reflect the new inner content types. 605 o Added to the security considerations to highlight the risk from 606 insufficient spam filters. 608 9.6. Changes from draft-ietf-slim-multilangcontent-01 to draft-ietf- 609 slim-multilangcontent-02 611 o Restricted the use of a From field in the language message parts 612 and the language independent part. 614 o Updated the security considerations to highlight the risk of an 615 unmatched sender addresses that could be set in the language 616 message parts. 618 9.7. Changes from draft-ietf-slim-multilangcontent-02 to draft-ietf- 619 slim-multilangcontent-03 621 o Relaxed the restriction on the use of the From field in the 622 language message parts to allow a localised version of the 623 sender's display name. 625 9.8. Changes from draft-ietf-slim-multilangcontent-03 to draft-ietf- 626 slim-multilangcontent-04 628 o Updated the wording of the security considerations section to 629 reflect the relaxation of the use of the From field in the 630 language message parts. 632 9.9. Changes from draft-ietf-slim-multilangcontent-04 to draft-ietf- 633 slim-multilangcontent-05 635 o Referenced the RFC for message/global in Language Message Parts 636 section. 638 o Removed RFC 2119 keyword in the Message Part Selection section. 640 o Included full email addresses in all examples. 642 o Updated reference name of real-time companion document in the 643 Introduction. 645 o Removed paragraph warning of over use of language sub-tags. 647 o Changed 'exponential' to 'significantly' in Introduction. 649 9.10. Changes from draft-ietf-slim-multilangcontent-05 to draft-ietf- 650 slim-multilangcontent-06 652 o Changed parameter Translation-Type back to a new field to reduce 653 the risk of breaking existing implementations that don't expect 654 any parameters on Content-Language. 656 o Improved the IANA Considerations section to include the full 657 registration template for the multipart/multilingual type and the 658 new Translation-Type field. 660 10. Acknowledgements 662 The authors are grateful for the helpful input received from many 663 people but would especially like to acknowledge the help of Harald 664 Alvestrand, Stephane Bortzmeyer, Eric Burger, Mark Davis, Doug Ewell, 665 Randall Gellens, Gunnar Hellstrom, Barry Leiba, Sean Leonard, John 666 Levine, Alexey Melnikov, Addison Phillips, Julian Reschke, Pete 667 Resnick, Brian Rosen, Fiona Tomkinson, Simon Tyler and Daniel Vargha. 669 The authors would also like to thank Fernando Alvaro and Luis de 670 Pablo for their work on the Spanish translations. 672 11. IANA Considerations 674 11.1. The multipart/multilingual MIME type 676 The multipart/multilingual MIME type will be registered with IANA 677 including a reference to this document. This is the registration 678 template: 680 Media Type name: multipart 682 Media subtype name: multilingual 684 Required parameters: boundary (defined in RFC2046) 686 Optional parameters: N/A 688 Encoding considerations: only "7bit", "8bit", or "binary" are 689 permitted 691 Security considerations: See the Security Considerations section 692 in this document 694 Interoperability considerations: 695 Existing systems that do not treat unknown multipart subtypes 696 as multipart/mixed may not correctly render a 697 multipart/multilingual type. 699 Published specification: This document 701 Applications that use this media type: 702 Mail Transfer Agents, Mail User Agents, spam detection, 703 virus detection modules and message authentication modules. 705 Additional information: 706 Deprecated alias names for this type: N/A 707 Magic number(s): N/A 708 File extension(s): N/A 709 Macintosh file type code(s): N/A 711 Person & email address to contact for further information: 712 Nik Tomkinson 713 rfc.nik.tomkinson@gmail.com 715 Nathaniel Borenstein 716 nsb@mimecast.com 718 Intended usage: Common 720 11.2. The Translation-Type field 722 The Translation-Type field will be added to the IANA "Permanent 723 Message Header Field Names" registry. That entry will reference this 724 document. This is the registration template: 726 Header field name: Translation-Type 728 Applicable protocol: mail 730 Status: Standard 732 Author/Change controller: IETF 734 Specification document(s): this document 736 Related information: none 738 12. Security Considerations 740 Whilst it is intended that each language message part is a direct 741 translation of the original message, this may not always be the case 742 and these parts could contain undesirable content. Therefore there 743 is a possible risk that undesirable text or images could be shown to 744 the recipient if the message is passed through a spam filter that 745 does not check all of the message parts. The risk should be minimal 746 due to the fact that an unknown multipart subtype should be treated 747 as multipart/mixed and so each message part should be subsequently 748 scanned. 750 Because the language message parts have a Content-Type of message/ 751 rfc822 or message/global, they might contain From fields which could 752 have different values to that of the top-level From field and may not 753 reflect the actual sender. The inconsistent From field values might 754 get shown to the recipient in a non-conforming email client and may 755 mislead the recipient into thinking that the email came from someone 756 other than the real sender. 758 13. References 760 13.1. Normative References 762 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 763 Extensions (MIME) Part Two: Media Types", RFC 2046, 764 DOI 10.17487/RFC2046, November 1996, 765 . 767 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 768 Part Three: Message Header Extensions for Non-ASCII Text", 769 RFC 2047, DOI 10.17487/RFC2047, November 1996, 770 . 772 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 773 Requirement Levels", BCP 14, RFC 2119, 774 DOI 10.17487/RFC2119, March 1997, 775 . 777 [RFC2183] Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 778 Presentation Information in Internet Messages: The 779 Content-Disposition Header Field", RFC 2183, 780 DOI 10.17487/RFC2183, August 1997, 781 . 783 [RFC3282] Alvestrand, H., "Content Language Headers", RFC 3282, 784 DOI 10.17487/RFC3282, May 2002, 785 . 787 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 788 BCP 47, RFC 4647, DOI 10.17487/RFC4647, September 2006, 789 . 791 [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying 792 Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, 793 September 2009, . 795 [RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized 796 Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 797 2012, . 799 13.2. Informational References 801 [I-D.ietf-slim-negotiating-human-language] 802 Gellens, R., "Negotiating Human Language in Real-Time 803 Communications", draft-ietf-slim-negotiating-human- 804 language-04 (work in progress), July 2016. 806 Authors' Addresses 808 Nik Tomkinson 809 Mimecast Ltd 810 CityPoint, One Ropemaker Street 811 London EC2Y 9AW 812 United Kingdom 814 Email: rfc.nik.tomkinson@gmail.com 815 Nathaniel Borenstein 816 Mimecast Ltd 817 480 Pleasant Street 818 Watertown MA 02472 819 North America 821 Email: nsb@mimecast.com