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Display-Based Address Sorting for the IMAP4 SORT Extension
RFC 5957

Internet Engineering Task Force (IETF)                           D. Karp
Request for Comments: 5957                                        Zimbra
Updates: 5256                                                  July 2010
Category: Standards Track
ISSN: 2070-1721

       Display-Based Address Sorting for the IMAP4 SORT Extension

Abstract

   This document describes an IMAP protocol extension enabling server-
   side message sorting on the commonly displayed portion of the From
   and To header fields.

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/rfc5957.

Copyright Notice

   Copyright (c) 2010 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.

Karp               IMAP4 Display-Based Address Sorting          [Page 1]
RFC 5957                                                       July 2010

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................2
   3. DISPLAY Sort Value for an Address ...............................2
   4. The DISPLAYFROM and DISPLAYTO Sort Criteria .....................3
   5. Formal Syntax ...................................................3
   6. Security Considerations .........................................3
   7. Internationalization Considerations .............................4
   8. IANA Considerations .............................................4
   9. Normative References ............................................4

1.  Introduction

   The [SORT] extension to the [IMAP] protocol provides a means for the
   server-based sorting of messages.  It defines a set of sort criteria
   and the mechanism for determining the sort value of a message for
   each such ordering.

   The [SORT] FROM and TO orderings sort messages lexically on the
   [IMAP] addr-mailbox of the first address in the message's From and To
   headers, respectively.  This document provides two alternative
   orderings, DISPLAYFROM and DISPLAYTO, which sort messages based on
   the first From or To address's [IMAP] addr-name (generally the same
   as its [RFC5322] display-name), when present.

   A server that supports the full [SORT] extension as well as both the
   DISPLAYFROM and DISPLAYTO sort criteria indicates this by returning
   "SORT=DISPLAY" in its CAPABILITY response.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  DISPLAY Sort Value for an Address

   For the purposes of the sort criteria defined in this document, the
   sort value for an [IMAP] address structure is defined as follows:

   o  If the address structure's [IMAP] addr-name is non-NIL, apply the
      procedure from [RFC5255], Section 4.6.  (That is, decode any
      [RFC2047] encoded-words and convert the resulting character string
      into a charset valid for the currently active [RFC4790] collation,
      with a default of UTF-8.)  If the resulting octet string is not
      the empty string, use it as the sort value for the address.

Karp               IMAP4 Display-Based Address Sorting          [Page 2]
RFC 5957                                                       July 2010

   o  Otherwise, if the address structure's [IMAP] addr-mailbox and
      [IMAP] addr-host are both non-NIL, the sort value for the address
      is addr-mailbox@addr-host.

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