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IMAP Support for UTF-8
RFC 6855

Internet Engineering Task Force (IETF)                   P. Resnick, Ed.
Request for Comments: 6855                         Qualcomm Incorporated
Obsoletes: 5738                                           C. Newman, Ed.
Category: Standards Track                                         Oracle
ISSN: 2070-1721                                             S. Shen, Ed.
                                                                   CNNIC
                                                              March 2013

                         IMAP Support for UTF-8

Abstract

   This specification extends the Internet Message Access Protocol
   (IMAP) to support UTF-8 encoded international characters in user
   names, mail addresses, and message headers.  This specification
   replaces RFC 5738.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6855.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Resnick, et al.              Standards Track                    [Page 1]
RFC 6855                 IMAP Support for UTF-8               March 2013

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  2
   3.  "UTF8=ACCEPT" IMAP Capability and UTF-8 in IMAP
       Quoted-Strings . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  IMAP UTF8 "APPEND" Data Extension  . . . . . . . . . . . . . .  4
   5.  "LOGIN" Command and UTF-8  . . . . . . . . . . . . . . . . . .  5
   6.  "UTF8=ONLY" Capability . . . . . . . . . . . . . . . . . . . .  5
   7.  Dealing with Legacy Clients  . . . . . . . . . . . . . . . . .  6
   8.  Issues with UTF-8 Header Mailstore . . . . . . . . . . . . . .  7
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   10. Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     11.1.  Normative References  . . . . . . . . . . . . . . . . . .  9
     11.2.  Informative References  . . . . . . . . . . . . . . . . . 10
   Appendix A.  Design Rationale  . . . . . . . . . . . . . . . . . . 11
   Appendix B.  Acknowledgments . . . . . . . . . . . . . . . . . . . 11

1.  Introduction

   This specification forms part of the Email Address
   Internationalization protocols described in the Email Address
   Internationalization Framework document [RFC6530].  It extends IMAP
   [RFC3501] to permit UTF-8 [RFC3629] in headers, as described in
   "Internationalized Email Headers" [RFC6532].  It also adds a
   mechanism to support mailbox names using the UTF-8 charset.  This
   specification creates two new IMAP capabilities to allow servers to
   advertise these new extensions.

   This specification assumes that the IMAP server will be operating in
   a fully internationalized environment, i.e., one in which all clients
   accessing the server will be able to accept non-ASCII message header
   fields and other information, as specified in Section 3.  At least
   during a transition period, that assumption will not be realistic for
   many environments; the issues involved are discussed in Section 7
   below.

   This specification replaces an earlier, experimental approach to the
   same problem [RFC5738].

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   in this document are to be interpreted as defined in "Key words for
   use in RFCs to Indicate Requirement Levels" [RFC2119].

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