Recommended Usage of the Authenticated Received Chain (ARC)
draft-ietf-dmarc-arc-usage-01

Document Type Active Internet-Draft (dmarc WG)
Last updated 2016-12-27
Replaces draft-jones-arc-usage
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DMARC Working Group                                             S. Jones
Internet-Draft                                                 DMARC.org
Obsoletes: draft-jones-arc-usage-01 (if                     J. Rae-Grant
           approved)                                              Google
Intended status: Informational                                  T. Adams
Expires: May 29, 2016                                             Paypal
                                                        K. Andersen, Ed.
                                                                LinkedIn
                                                       December 27, 2016

      Recommended Usage of the Authenticated Received Chain (ARC)
                     draft-ietf-dmarc-arc-usage-01

Abstract

   The Authentication Received Chain (ARC) provides a means to preserve
   email authentication results and verify the identity of email message
   handlers, each of which participates by inserting certain header
   fields before passing the message on.  But the specification does not
   indicate how intermediaries and receivers should interpret or utilize
   ARC.  This document will provide guidance in these areas.

Status of This Memo

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   This Internet-Draft will expire on May 29, 2017.

Copyright Notice

   Copyright (c) 2016 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

Jones, et al.           Expires December 27, 2016               [Page 1]
Internet-Draft                  ARC-USAGE                      June 2016

   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  How does ARC work?  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Guidance for Receivers/Validators . . . . . . . . . . . . . .   4
     3.1.  What is the significance of an intact ARC chain?  . . . .   4
     3.2.  What exactly is an "intact" ARC chain?  . . . . . . . . .   4
     3.3.  What is the significance of an invalid ("broken") ARC
           chain?  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  What does the absence of an ARC chain in a message mean?    5
     3.5.  What reasonable conclusions can you draw based upon
           seeing lots of mail with ARC chains?  . . . . . . . . . .   5
     3.6.  What if none of the intermediaries have been seen
           previously? . . . . . . . . . . . . . . . . . . . . . . .   6
     3.7.  What about ARC chains where some intermediaries are known
           and others are not? . . . . . . . . . . . . . . . . . . .   6
     3.8.  What should message handlers do when they detect
           malicious content in messages where ARC is present? . . .   6
     3.9.  What feedback does a sender or domain owner get about ARC
           when it is applied to their messages? . . . . . . . . . .   7
     3.10. What prevents a malicious actor from removing the ARC
           header fields,  . . . . . . . . . . . . . . . . . . . . .   7
   4.  Guidance for Intermediaries . . . . . . . . . . . . . . . . .   8
     4.1.  What is an Intermediary under ARC?  . . . . . . . . . . .   8
     4.2.  What are the minimum requirements for an ARC
           Intermediary? . . . . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  More specifically a participating ARC intermediary
               must do the following:  . . . . . . . . . . . . . . .   8
     4.3.  Should every MTA be an ARC participant? . . . . . . . . .   8
     4.4.  What should an intermediary do in the case of an invalid
           or "broken" ARC chain?  . . . . . . . . . . . . . . . . .   9
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