I hope this would be a consideration as a fix or method to address the problem with DMARC's p=reject restrictive policy for 3rd party signers, including mailing list.

Please correct any misunderstanding with the DMARC draft I may have.

DMARC by definition requires alignment for matching domains. An adkim=s (strict) is an exact match and adkim=r (relaxed) means sub-domains are allowed.

From what I see, there is no 3rd party allowance and the only things that saves you is p=none or p=quarantine.

If the DMARC draft is locked down, I would like to propose an extension. Section 3.1.4.3 talks about authentication extensions:

   3.1.4.3.  Alignment and Extension Technologies

   If DMARC is extended to include the use of other authentication
   mechanisms, the extensions will need to allow for domain identifier
   extraction so that alignment with the RFC5322.From domain can be
   verified.

This would be a simple first step consideration -- A new ATPS tag

  atps=0  default, extension disabled allowed backward compatibility.
  atps=1  Valid alignment allows a valid 3rd party signature (no checks).
  atps=2  Valid alignment allows a valid 3rd party signature with ATPS
          (Authorized 3rd Party Signer) checking, RFC6541.

atps=1 basically declares a relaxed MUST SIGN policy. atps=2 means the 3rd party signer must be authorized using RFC6541. Pete Resnick is exploring a May-Resign protocol idea, so we add
an option for it.

  atps=3  Valid alignment allows a valid 3rd party signature using
          the May-Resign header method.

--
HLS


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