Recommended Usage of the Authenticated Received Chain (ARC)
draft-jones-arc-usage-00

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Last updated 2015-10-16
Replaced by draft-ietf-dmarc-arc-usage
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independent                                              . OAR-DEV Group
Internet-Draft                                             OAR-DEV Group
Intended status: Informational                                  S. Jones
Expires: April 18, 2016                                        DMARC.org
                                                            J. Rae-Grant
                                                                  Google
                                                                T. Adams
                                                                  Paypal
                                                        K. Andersen, Ed.
                                                                LinkedIn
                                                        October 16, 2015

      Recommended Usage of the Authenticated Received Chain (ARC)
                        draft-jones-arc-usage-00

Abstract

   The Authentication Results 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 headers
   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 April 18, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

OAR-DEV Group, et al.    Expires April 18, 2016                 [Page 1]
Internet-Draft                  ARC-USAGE                   October 2015

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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
           headers, altering the content, and creating a new ARC
           chain?  . . . . . . . . . . . . . . . . . . . . . . . . .   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
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