Internationalized Email Headers
RFC 5335
Document | Type |
RFC - Experimental
(September 2008; Errata)
Obsoleted by RFC 6532
|
|
---|---|---|---|
Author | Abel Yang | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5335 (Experimental) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Chris Newman | ||
Send notices to | draft-ietf-eai-smtpext@ietf.org |
Network Working Group Y. Abel, Ed. Request for Comments: 5335 TWNIC Updates: 2045, 2822 September 2008 Category: Experimental Internationalized Email Headers Status of This Memo This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited. Abstract Full internationalization of electronic mail requires not only the capabilities to transmit non-ASCII content, to encode selected information in specific header fields, and to use non-ASCII characters in envelope addresses. It also requires being able to express those addresses and the information based on them in mail header fields. This document specifies an experimental variant of Internet mail that permits the use of Unicode encoded in UTF-8, rather than ASCII, as the base form for Internet email header field. This form is permitted in transmission only if authorized by an SMTP extension, as specified in an associated specification. This specification Updates section 6.4 of RFC 2045 to conform with the requirements. Abel Experimental [Page 1] RFC 5335 I18N Email Headers September 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Role of This Specification . . . . . . . . . . . . . . . . 3 1.2. Relation to Other Standards . . . . . . . . . . . . . . . 3 2. Background and History . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Changes on Message Header Fields . . . . . . . . . . . . . . . 5 4.1. UTF-8 Syntax and Normalization . . . . . . . . . . . . . . 5 4.2. Changes on MIME Headers . . . . . . . . . . . . . . . . . 6 4.3. Syntax Extensions to RFC 2822 . . . . . . . . . . . . . . 6 4.4. Change on addr-spec Syntax . . . . . . . . . . . . . . . . 8 4.5. Trace Field Syntax . . . . . . . . . . . . . . . . . . . . 9 4.6. message/global . . . . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 13 Abel Experimental [Page 2] RFC 5335 I18N Email Headers September 2008 1. Introduction 1.1. Role of This Specification Full internationalization of electronic mail requires several capabilities: o The capability to transmit non-ASCII content, provided for as part of the basic MIME specification [RFC2045], [RFC2046]. o The capability to use international characters in envelope addresses, discussed in [RFC4952] and specified in [RFC5336]. o The capability to express those addresses, and information related to them and based on them, in mail header fields, defined in this document. This document specifies an experimental variant of Internet mail that permits the use of Unicode encoded in UTF-8 [RFC3629], rather than ASCII, as the base form for Internet email header fields. This form is permitted in transmission, if authorized by the SMTP extension specified in [RFC5336] or by other transport mechanisms capable of processing it. 1.2. Relation to Other Standards This document updates Section 6.4 of RFC 2045. It removes the blanket ban on applying a content-transfer-encoding to all subtypes of message/, and instead specifies that a composite subtype MAY specify whether or not a content-transfer-encoding can be used for that subtype, with "cannot be used" as the default. This document also updates [RFC2822] and MIME ([RFC2045]), and the fact that an Experimental specification updates a Standards-Track specification means that people who participate in the experiment have to consider those standards updated. Allowing use of a content-transfer-encoding on subtypes of messages is not limited to transmissions that are authorized by the SMTP extension specified in [RFC5336]. Message/global permits use of a content-transfer-encoding. 2. Background and History Mailbox names often represent the names of human users. Many of these users throughout the world have names that are not normally expressed with just the ASCII repertoire of characters, and wouldShow full document text