Email Authentication Status Codes
RFC 7372

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Internet Engineering Task Force (IETF)                      M. Kucherawy
Request for Comments: 7372                                September 2014
Updates: 7208
Category: Standards Track
ISSN: 2070-1721

                   Email Authentication Status Codes

Abstract

   This document registers code points to allow status codes to be
   returned to an email client to indicate that a message is being
   rejected or deferred specifically because of email authentication
   failures.

   This document updates RFC 7208, since some of the code points
   registered replace the ones recommended for use in that document.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7372.

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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Kucherawy                    Standards Track                    [Page 1]
RFC 7372                 Email Auth Status Codes          September 2014

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Key Words . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  New Enhanced Status Codes . . . . . . . . . . . . . . . . . .   3
     3.1.  DKIM Failure Codes  . . . . . . . . . . . . . . . . . . .   3
     3.2.  SPF Failure Codes . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Reverse DNS Failure Code  . . . . . . . . . . . . . . . .   5
     3.4.  Multiple Authentication Failures Code . . . . . . . . . .   5
   4.  General Considerations  . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   8

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 (DKIM) and Sender Policy Framework (SPF), two
   protocols for conducting message authentication.  Another common
   email acceptance test is the reverse Domain Name System (DNS) 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 any of these mechanisms.  This is
   potentially useful information to agents that need more than
   rudimentary handling information about the reason a message was
   rejected on receipt.  This document introduces enhanced status codes
   for reporting those cases to clients.

   Section 3.2 updates [RFC7208], as new enhanced status codes relevant
   to that specification are being registered and recommended for use.

2.  Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

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RFC 7372                 Email Auth Status Codes          September 2014

3.  New Enhanced Status Codes

   The new enhanced status codes are defined in the following
   subsections.

3.1.  DKIM Failure Codes

   In the code point definitions below, the following definitions are
   used:

   passing:  A signature is "passing" if the basic DKIM verification
      algorithm, as defined in [RFC6376], succeeds.

   acceptable:  A signature is "acceptable" if it satisfies all locally
      defined requirements (if any) in addition to passing the basic
      DKIM verification algorithm (e.g., certain header fields are
      included in the signed content, no partial signatures, etc.).