Message Submission BURL Extension
RFC 4468

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• 04

Network Working Group                                          C. Newman
Request for Comments: 4468                              Sun Microsystems
Updates: 3463                                                   May 2006
Category: Standards Track

                   Message Submission BURL 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.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The submission profile of Simple Mail Transfer Protocol (SMTP)
   provides a standard way for an email client to submit a complete
   message for delivery.  This specification extends the submission
   profile by adding a new BURL command that can be used to fetch
   submission data from an Internet Message Access Protocol (IMAP)
   server.  This permits a mail client to inject content from an IMAP
   server into the SMTP infrastructure without downloading it to the
   client and uploading it back to the server.

Newman                      Standards Track                     [Page 1]
RFC 4468           Message Submission BURL Extension            May 2006

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................2
   3. BURL Submission Extension .......................................3
      3.1. SMTP Submission Extension Registration .....................3
      3.2. BURL Transaction ...........................................3
      3.3. The BURL IMAP Options ......................................4
      3.4. Examples ...................................................5
      3.5. Formal Syntax ..............................................6
   4. 8-Bit and Binary ................................................7
   5. Updates to RFC 3463 .............................................7
   6. Response Codes ..................................................7
   7. IANA Considerations .............................................9
   8. Security Considerations .........................................9
   9. References .....................................................11
      9.1. Normative References ......................................11
      9.2. Informative References ....................................12
   Appendix A.  Acknowledgements .....................................13

1.  Introduction

   This specification defines an extension to the standard Message
   Submission [RFC4409] protocol to permit data to be fetched from an
   IMAP server at message submission time.  This MAY be used in
   conjunction with the CHUNKING [RFC3030] mechanism so that chunks of
   the message can come from an external IMAP server.  This provides the
   ability to forward an email message without first downloading it to
   the client.

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].

   The formal syntax uses the Augmented Backus-Naur Form (ABNF)
   [RFC4234] notation including the core rules defined in Appendix B of
   RFC 4234.

Newman                      Standards Track                     [Page 2]
RFC 4468           Message Submission BURL Extension            May 2006

3.  BURL Submission Extension

   This section defines the BURL submission extension.

3.1.  SMTP Submission Extension Registration

   1.  The name of this submission extension is "BURL".  This extends
       the Message Submission protocol on port 587 and MUST NOT be
       advertised by a regular SMTP [RFC2821] server on port 25 that
       acts as a relay for incoming mail from other SMTP relays.

   2.  The EHLO keyword value associated with the extension is "BURL".

   3.  The BURL EHLO keyword will have zero or more arguments.  The only
       argument defined at this time is the "imap" argument, which MUST
       be present in order to use IMAP URLs with BURL.  Clients MUST
       ignore other arguments after the BURL EHLO keyword unless they
       are defined by a subsequent IETF standards track specification.
       The arguments that appear after the BURL EHLO keyword may change
       subsequent to the use of SMTP AUTH [RFC2554], so a server that
       advertises BURL with no arguments prior to authentication
       indicates that BURL is supported but authentication is required
       to use it.

   4.  This extension adds the BURL SMTP verb.  This verb is used as a
       replacement for the DATA command and is only permitted during a
       mail transaction after at least one successful RCPT TO.