IMAP4 Extension: Message Preview Generation
draft-ietf-extra-imap-fetch-preview-06

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Last updated 2019-07-01
Replaces draft-ietf-extra-imap-fetch-snippet
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EXTRA                                                         M. Slusarz
Internet-Draft                                         Open-Xchange Inc.
Intended status: Standards Track                            July 1, 2019
Expires: January 2, 2020

              IMAP4 Extension: Message Preview Generation
                 draft-ietf-extra-imap-fetch-preview-06

Abstract

   This document specifies an Internet Message Access Protocol (IMAP)
   protocol extension allowing a client to request a server-generated
   abbreviated representation of message data useful as a contextual
   preview of the entire message.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 2, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used In This Document . . . . . . . . . . . . . .   3
   3.  FETCH Data Item . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Command . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  PREVIEW Algorithms  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  FUZZY . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  PREVIEW Priority Modifiers  . . . . . . . . . . . . . . . . .   6
     5.1.  LAZY  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Appendix A.  Change History (To be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . .  12
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Many modern mail clients display small extracts of the body text as
   an aid to allow a user to quickly decide whether they are interested
   in viewing the full message contents.  Mail clients implementing the
   Internet Message Access Protocol [RFC3501] would benefit from a
   standardized, consistent way to generate these brief previews of
   messages.

   Generation of a preview on the server has several benefits.  First,
   it allows consistent representation of previews across all clients.
   This standardized display can reduce user confusion when using
   multiple clients, as abbreviated message representations in clients
   will show identical message contents.

   Second, server-side preview generation is more efficient.  A client-
   based algorithm needs to issue, at a minimum, a FETCH BODYSTRUCTURE
   command in order to determine which MIME [RFC2045] body part(s)
   should be represented in the preview.  Subsequently, at least one
   FETCH BODY command may be needed to retrieve body data used in
   preview generation.  These FETCH commands cannot be pipelined since
   the BODYSTRUCTURE query must be parsed on the client before the list
   of parts to be retrieved via the BODY command(s) can be determined.

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