The IMAP APPENDLIMIT Extension
draft-ietf-imapapnd-appendlimit-extension-07

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Document Type Active Internet-Draft (imapapnd WG)
Last updated 2015-12-28 (latest revision 2015-12-18)
Replaces draft-jayantheesh-imap-appendlimit-extension
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Network Working Group                                        Jayantheesh
Internet-Draft                                                  Narendra
Intended status: Standards Track             Samsung Electronics America
Expires: June 20, 2016                                 December 18, 2015

                     The IMAP APPENDLIMIT Extension
            draft-ietf-imapapnd-appendlimit-extension-07.txt

Abstract

   This document defines an extension to the IMAP service whereby a
   server can inform the client about a maximum mail upload size,
   allowing the client to avoid sending APPEND commands that will fail
   because of the messages are too large.

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
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   This Internet-Draft will expire on June 20, 2016.

Copyright Notice

   Copyright (c) 2015 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   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
     1.1.  Conventions and Terminology . . . . . . . . . . . . . . .   2
   2.  APPENDLIMIT Extension . . . . . . . . . . . . . . . . . . . .   3
   3.  Mailbox specific APPENDLIMIT  . . . . . . . . . . . . . . . .   3
     3.1.  STATUS response to the STATUS command . . . . . . . . . .   4
     3.2.  STATUS response to the LIST command . . . . . . . . . . .   4
     3.3.  APPENDLIMIT behaviour . . . . . . . . . . . . . . . . . .   4
   4.  APPEND response . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Formal syntax . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Some IMAP servers have limits for mail upload size, and those limits
   are not published to the email client.  When the email client APPENDs
   a message with huge attachments, using non-synchronizing literals,
   the APPEND fails because of the upload limit, but the client has
   already sent the message data anyway.  This results in unnecessary
   resource usage.  Especially in the mobile device environment,
   appending mail with huge attachment consumes device resources like
   device battery power and mobile data.

   The IMAP APPENDLIMIT extension provides an ability to advertise
   maximum upload size allowed by the IMAP server, so that email client
   knows the size limitation beforehand.  By implementing this
   extension, IMAP server side processing of huge attachments above the
   maximum upload size can be avoided.

1.1.  Conventions and Terminology

   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].

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.  If a single "C:" or "S:" label applies to
   multiple lines, then the line breaks between those lines are for
   editorial clarity only and are not part of the actual protocol
   exchange.

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2.  APPENDLIMIT Extension

   An IMAP server that supports APPENDLIMIT extension advertises this by
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