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Versions: (draft-kucherawy-email-auth-codes) 00 01 02 03 04 05 06 07 RFC 7372

Network Working Group                                       M. Kucherawy
Internet-Draft                                              May 23, 2014
Intended status: Informational
Expires: November 24, 2014


                   Email Authentication Status Codes
                 draft-ietf-appsawg-email-auth-codes-00

Abstract

   There is at present no way to return a status code to an email client
   that indicates a message is being rejected or deferred specifically
   because of email authentication failures.  This document registers
   codes for this purpose.

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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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on November 24, 2014.

Copyright Notice

   Copyright (c) 2014 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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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  New Status Codes  . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  DKIM Failures Code  . . . . . . . . . . . . . . . . . . . . 3
     2.2.  SPF Failures Code . . . . . . . . . . . . . . . . . . . . . 4
     2.3.  Reverse DNS Failure Code  . . . . . . . . . . . . . . . . . 4
   3.  General Considerations  . . . . . . . . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . . . 5







































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1.  Introduction

   [RFC3463] introduced Enhanced Mail System Status Codes, and [RFC5248]
   created an IANA registry for these.

   [RFC6376] and [RFC7208] introduced, respectively, DomainKeys
   Identified Mail and Sender Policy Framework, two protocols for
   conducting email authentication.  Another common email acceptance
   test is the reverse Domain Name System check on an email client's IP
   address, as described in Section 3 of [RFC7001].

   The current set of enhanced status codes does not include any code
   for indicating that a message is being rejected or deferred due to
   local policy reasons related to either of these two mechanisms.  This
   document introduces enhanced status codes for reporting those cases
   to clients.

2.  New Status Codes

   The following new status codes are defined:

2.1.  DKIM Failures Code


      Code:               X.7.19
      Sample Text:        No valid DKIM signature found
      Associated basic status code:  5
      Description:        This status code is returned when a message
                          did not contain a valid DKIM signature,
                          contrary to local policy requirements.
      Reference:          [this document]
      Submitter:          M. Kucherawy
      Change controller:  IESG


      Code:               X.7.20
      Sample Text:        No valid author DKIM signature found
      Associated basic status code:  5
      Description:        This status code is returned when a message
                          did not contain a valid DKIM signature
                          matching the domain(s) found in the From
                          header field, contrary to local policy
                          requirements.
      Reference:          [this document]
      Submitter:          M. Kucherawy
      Change controller:  IESG





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2.2.  SPF Failures Code


      Code:               X.7.21
      Sample Text:        SPF validation failed
      Associated basic status code:  5
      Description:        This status code is returned when a message
                          failed an SPF check, contrary to local
                          policy requirements.
      Reference:          [this document]
      Submitter:          M. Kucherawy
      Change controller:  IESG

2.3.  Reverse DNS Failure Code


      Code:               X.7.22
      Sample Text:        reverse DNS validation failed
      Associated basic status code:  5
      Description:        This status code is returned when an SMTP
                          client's IP address failed a reverse DNS
                          validation check, contrary to local policy
                          requirements.
      Reference:          [this document]
      Submitter:          M. Kucherawy
      Change controller:  IESG

3.  General Considerations

   By the nature of the Simple Mail Transfer Protocol (SMTP), only one
   enhanced status code can be returned for a given exchange between
   client and server.  However, an operator might decide to defer or
   reject a message for a plurality of reasons.  Clients receiving these
   codes need to consider that the failure reflected by one of these
   status codes might not reflect the only reason, or the most important
   reason, for non-acceptance of the message or command.

4.  Security Considerations

   Use of these codes reveals local policy with respect to email
   authentication, which can be useful information to actors attempting
   to deliver undesirable mail.  It should be noted that there is no
   specific obligation to use these codes; if an operator wishes not to
   reveal this aspect of local policy, it can continue using a generic
   result code such as 5.7.7 or even 5.7.0.






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5.  IANA Considerations

   Registration of two new enhanced status codes, for addition to the
   SMTP Enhanced Status Codes Registry, can be found in Section 2.

6.  Normative References

   [RFC3463]  Vaudreuil, G., "Enhanced Mail System Status Codes",
              RFC 3463, January 2003.

   [RFC5248]  Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced
              Mail System Status Codes", BCP 138, RFC 5248, June 2008.

   [RFC6376]  Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys
              Identified Mail (DKIM) Signatures", STD 76, RFC 6376,
              September 2011.

   [RFC7001]  Kucherawy, M., "Message Header Field for Indicating
              Message Authentication Status", RFC 7001, September 2013.

   [RFC7208]  Kitterman, S., "Sender Policy Framework (SPF) for
              Authorizing Use of Domains in Email, Version 1", RFC 7208,
              April 2014.

Appendix A.  Acknowledgments

   Ned Freed, Arnt Gulbrandsen, and Barry Leiba contributed to this
   work.

Author's Address

   Murray S. Kucherawy
   270 Upland Drive
   San Francisco, CA  94127
   USA

   EMail: superuser@gmail.com














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