Recommended Usage of the Authenticated Received Chain (ARC)
draft-ietf-dmarc-arc-usage-05
DMARC Working Group S. Jones
Internet-Draft DMARC.org
Intended status: Informational K. Andersen
Expires: October 25, 2018 LinkedIn
J. Rae-Grant
Google
T. Adams, Ed.
Paypal
April 23, 2018
Recommended Usage of the Authenticated Received Chain (ARC)
draft-ietf-dmarc-arc-usage-05
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 October 25, 2018.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Jones, et al. Expires October 25, 2018 [Page 1]
Internet-Draft ARC-USAGE April 2018
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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? . . . . . . . . . . 6
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? . . . 7
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, 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? . . . . . . . . . 9
4.4. What should an intermediary do in the case of an invalid
or "broken" ARC chain? . . . . . . . . . . . . . . . . . 9
4.5. What should I do in the case where there is no ARC chain
present in a message? . . . . . . . . . . . . . . . . . . 9
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