MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies
RFC 1521
Document | Type |
RFC - Draft Standard
(September 1993; No errata)
Updated by RFC 1590
Obsoletes RFC 1341
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Authors | Nathaniel Borenstein , Ned Freed | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf ps htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 1521 (Draft Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group N. Borenstein Request for Comments: 1521 Bellcore Obsoletes: 1341 N. Freed Category: Standards Track Innosoft September 1993 MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies Status of this Memo This RFC specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract STD 11, RFC 822 defines a message representation protocol which specifies considerable detail about message headers, but which leaves the message content, or message body, as flat ASCII text. This document redefines the format of message bodies to allow multi-part textual and non-textual message bodies to be represented and exchanged without loss of information. This is based on earlier work documented in RFC 934 and STD 11, RFC 1049, but extends and revises that work. Because RFC 822 said so little about message bodies, this document is largely orthogonal to (rather than a revision of) RFC 822. In particular, this document is designed to provide facilities to include multiple objects in a single message, to represent body text in character sets other than US-ASCII, to represent formatted multi- font text messages, to represent non-textual material such as images and audio fragments, and generally to facilitate later extensions defining new types of Internet mail for use by cooperating mail agents. This document does NOT extend Internet mail header fields to permit anything other than US-ASCII text data. Such extensions are the subject of a companion document [RFC-1522]. This document is a revision of RFC 1341. Significant differences from RFC 1341 are summarized in Appendix H. Borenstein & Freed [Page 1] RFC 1521 MIME September 1993 Table of Contents 1. Introduction....................................... 3 2. Notations, Conventions, and Generic BNF Grammar.... 6 3. The MIME-Version Header Field...................... 7 4. The Content-Type Header Field...................... 9 5. The Content-Transfer-Encoding Header Field......... 13 5.1. Quoted-Printable Content-Transfer-Encoding......... 18 5.2. Base64 Content-Transfer-Encoding................... 21 6. Additional Content-Header Fields................... 23 6.1. Optional Content-ID Header Field................... 23 6.2. Optional Content-Description Header Field.......... 24 7. The Predefined Content-Type Values................. 24 7.1. The Text Content-Type.............................. 24 7.1.1. The charset parameter.............................. 25 7.1.2. The Text/plain subtype............................. 28 7.2. The Multipart Content-Type......................... 28 7.2.1. Multipart: The common syntax...................... 29 7.2.2. The Multipart/mixed (primary) subtype.............. 34 7.2.3. The Multipart/alternative subtype.................. 34 7.2.4. The Multipart/digest subtype....................... 36 7.2.5. The Multipart/parallel subtype..................... 37 7.2.6. Other Multipart subtypes........................... 37 7.3. The Message Content-Type........................... 38 7.3.1. The Message/rfc822 (primary) subtype............... 38 7.3.2. The Message/Partial subtype........................ 39 7.3.3. The Message/External-Body subtype.................. 42 7.3.3.1. The "ftp" and "tftp" access-types............... 44 7.3.3.2. The "anon-ftp" access-type...................... 45 7.3.3.3. The "local-file" and "afs" access-types......... 45 7.3.3.4. The "mail-server" access-type................... 45 7.3.3.5. Examples and Further Explanations............... 46 7.4. The Application Content-Type....................... 49 7.4.1. The Application/Octet-Stream (primary) subtype..... 50 7.4.2. The Application/PostScript subtype................. 50 7.4.3. Other Application subtypes......................... 53 7.5. The Image Content-Type............................. 53 7.6. The Audio Content-Type............................. 54 7.7. The Video Content-Type............................. 54 7.8. Experimental Content-Type Values................... 54 8. Summary............................................ 56Show full document text