Tunneling of SMTP Message Transfer Priorities
draft-melnikov-smtp-priority-tunneling-00

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Network Working Group                                        A. Melnikov
Internet-Draft                                                 Isode Ltd
Intended status: Experimental                                K. Carlberg
Expires: November 2, 2012                                            G11
                                                             May 1, 2012

             Tunneling of SMTP Message Transfer Priorities
               draft-melnikov-smtp-priority-tunneling-00

Abstract

   This memo defines a mechanism for tunneling of SMTP (Simple Mail
   Transfer Protocol) Message Transfer Priority values through MTAs
   (Message Transfer Agents) that don't support the MT-PRIORITY SMTP
   extension.

Status of This Memo

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

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   This Internet-Draft will expire on November 2, 2012.

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Internet-Draft  Tunneling of Message Transfer Priorities        May 2012

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
   3.  Handling of messages received via SMTP . . . . . . . . . . . .  4
     3.1.  Handling of the MT-PRIORITY parameter by the receiving
           SMTP server  . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Determining priority of a message  . . . . . . . . . . . .  5
     3.3.  Relay of messages to other conforming SMTP servers . . . .  6
     3.4.  Relay of messages to non-conforming SMTP servers . . . . .  6
     3.5.  Mailing lists and Aliases  . . . . . . . . . . . . . . . .  7
     3.6.  Gatewaying a message into a foreign environment  . . . . .  7
     3.7.  Interaction with DSN SMTP Extension  . . . . . . . . . . .  7
   4.  Header field: MT-Priority  . . . . . . . . . . . . . . . . . .  7
   5.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
     7.1.  Modification of MT-Priority header field and DKIM  . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 12

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1.  Introduction

   This document specifies application layer tunneling of message
   priority through SMTP servers.  The purpose of this tunneling is to
   convey the priority of the message through Message Transfer Agents
   (MTAs) that do not support the SMTP priority extension specified in
   [SMTP-PRIORITY].  The tunneling is done using a new message header
   field to Internet message format specified in [RFC5322].

   Various Mail User Agents (MUAs) already use various other header
   fields that convey a similar meaning, such as message importance.
   Example of such header fields are Importance [RFC2156], Priority
   [RFC2156] and X-Priority (undocumented).  Considering subtle
   differences in the meaning of these header fields and widely
   different syntax, this document defines a new header field.

   This document is motivated by 2 main deployment scenarious: (1) Mail
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