Network Working Group C. Newman
Request for Comments: 5255 Sun Microsystems
Category: Standards Track A. Gulbrandsen
Oryx Mail Systems GmhH
A. Melnikov
Isode Limited
June 2008
Internet Message Access Protocol Internationalization
Status of This Memo
This document 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" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
Internet Message Access Protocol (IMAP) version 4rev1 has basic
support for non-ASCII characters in mailbox names and search
substrings. It also supports non-ASCII message headers and content
encoded as specified by Multipurpose Internet Mail Extensions (MIME).
This specification defines a collection of IMAP extensions that
improve international support including language negotiation for
international error text, translations for namespace prefixes, and
comparator negotiation for search, sort, and thread.
Newman, et al. Standards Track [Page 1]RFC 5255 IMAP Internationalization June 2008Table of Contents
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................3
3. LANGUAGE Extension ..............................................3
3.1. LANGUAGE Extension Requirements ............................4
3.2. LANGUAGE Command ...........................................4
3.3. LANGUAGE Response ..........................................6
3.4. TRANSLATION Extension to the NAMESPACE Response ............7
3.5. Formal Syntax ..............................................8
4. I18NLEVEL=1 and I18NLEVEL=2 Extensions ..........................9
4.1. Introduction and Overview ..................................9
4.2. Requirements Common to Both I18NLEVEL=1 and I18NLEVEL=2 ....9
4.3. I18NLEVEL=1 Extension Requirements ........................10
4.4. I18NLEVEL=2 Extension Requirements ........................10
4.5. Compatibility Notes .......................................11
4.6. Comparators and Character Encodings .......................11
4.7. COMPARATOR Command ........................................13
4.8. COMPARATOR Response .......................................14
4.9. BADCOMPARATOR Response Code ...............................14
4.10. Formal Syntax ............................................14
5. Other IMAP Internationalization Issues .........................15
5.1. Unicode Userids and Passwords .............................15
5.2. UTF-8 Mailbox Names .......................................15
5.3. UTF-8 Domains, Addresses, and Mail Headers ................15
6. IANA Considerations ............................................16
7. Security Considerations ........................................16
8. Acknowledgements ...............................................16
9. Relevant Sources of Documents for Internationalized IMAP
Implementations ................................................17
10. Normative References ..........................................17
11. Informative References ........................................18
Newman, et al. Standards Track [Page 2]RFC 5255 IMAP Internationalization June 20081. Introduction
This specification defines two IMAP4rev1 [RFC3501] extensions to
enhance international support. These extensions can be advertised
and implemented separately.
The LANGUAGE extension allows the client to request a suitable
language for protocol error messages and in combination with the
NAMESPACE extension [RFC2342] enables namespace translations.
The I18NLEVEL=2 extension allows the client to request a suitable
collation that will modify the behavior of the base specification's
SEARCH command as well as the SORT and THREAD extensions [SORT].
This leverages the collation registry [RFC4790]. The I18NLEVEL=1
extension updates SEARCH/SORT/THREAD to use i;unicode-casemap
comparator, as defined in [UCM]. I18NLEVEL=1 is a simpler version of
datatracker.ietf.org