Internet Message Access Protocol - CONVERT Extension
RFC 5259

Document Type RFC - Proposed Standard (July 2008; No errata)
Last updated 2015-10-14
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Network Working Group                                   A. Melnikov, Ed.
Request for Comments: 5259                                     Isode Ltd
Category: Standards Track                                 P. Coates, Ed.
                                                        Sun Microsystems
                                                               July 2008

          Internet Message Access Protocol - CONVERT Extension

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

   CONVERT defines extensions to IMAP allowing clients to request
   adaptation and/or transcoding of attachments.  Clients can specify
   the conversion details or allow servers to decide based on knowledge
   of client capabilities, on user or administrator preferences, or on
   server settings.

Melnikov & Coates           Standards Track                     [Page 1]
RFC 5259                 IMAP CONVERT extension                July 2008

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  Relation with Other IMAP Specifications  . . . . . . . . . . .  4
     3.1.  CAPABILITY Response  . . . . . . . . . . . . . . . . . . .  4
   4.  Scope of Conversions . . . . . . . . . . . . . . . . . . . . .  4
   5.  Discovery of Available Conversions . . . . . . . . . . . . . .  4
     5.1.  CONVERSIONS Command  . . . . . . . . . . . . . . . . . . .  4
     5.2.  CONVERSION Response  . . . . . . . . . . . . . . . . . . .  6
   6.  CONVERT and UID CONVERT Commands . . . . . . . . . . . . . . .  6
   7.  CONVERT Conversion Parameters  . . . . . . . . . . . . . . . . 12
     7.1.  Mandatory-to-Implement Conversions and Conversion
           Parameters . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.2.  Additional Features for Mobile Usage . . . . . . . . . . . 13
   8.  Request/Response Data Items to CONVERT/UID CONVERT Commands  . 14
     8.1.  CONVERTED Untagged Response  . . . . . . . . . . . . . . . 14
     8.2.  BODYPARTSTRUCTURE CONVERT Request and Response Item  . . . 14
     8.3.  BINARY.SIZE CONVERT Request and Response Item  . . . . . . 15
     8.4.  AVAILABLECONVERSIONS CONVERT Request and Response Item . . 16
     8.5.  Implementation Considerations  . . . . . . . . . . . . . . 17
   9.  Status Responses and Response Code Extensions  . . . . . . . . 17
   10. Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . . . 20
   11. Manageability Considerations . . . . . . . . . . . . . . . . . 24
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
     12.1. Registration of unknown-character-replacement Media
           Type Parameter . . . . . . . . . . . . . . . . . . . . . . 25
   13. Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   14. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     15.2. Informative References . . . . . . . . . . . . . . . . . . 29

Melnikov & Coates           Standards Track                     [Page 2]
RFC 5259                 IMAP CONVERT extension                July 2008

1.  Introduction

   This document defines the CONVERT extension to IMAP4 [RFC3501].
   CONVERT provides adaptation and transcoding of body parts as needed
   by the client.  Conversion (adaptation, transcoding) may be requested
   by the client and performed by the server on a best effort basis or,
   when requested by the client, decided by the server based on the
   server's knowledge of the client capabilities, user or administrator
   preferences, or server settings.

   This extension is primarily intended to be useful to mobile clients.
   It satisfies requirements specified in [OMA-ME-RD].

   A server that supports CONVERT can convert body parts to other
   formats to be viewed (for example) on a mobile device.  The client
   can explicitly request a particular conversion or ask the server to
   select the best available conversion.  When allowed by the client,
   the server determines how to convert based on its own strategy (e.g.,
   based on knowledge of the client as discussed hereafter).  If the
   server knows the characteristics of the device (out of scope for
   CONVERT) or can determine them (for example, using a conversion
   parameter containing device type), converted body parts can also be
   optimized for capabilities of the device (e.g., form factor of
   pictures).  The client is able to control conversions using optional
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