Re: [dmarc-ietf] Amazon Comments to DMARC Extension to PSD

Scott Kitterman <sklist@kitterman.com> Wed, 17 July 2019 23:50 UTC

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Date: Wed, 17 Jul 2019 23:50:21 +0000
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To: dmarc@ietf.org
From: Scott Kitterman <sklist@kitterman.com>
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Subject: Re: [dmarc-ietf] Amazon Comments to DMARC Extension to PSD
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On July 17, 2019 10:23:11 PM UTC, "Flaim, Bobby" <flaim=40amazon.com@dmarc.ietf.org>; wrote:
>Amazon supports this draft and effort .
>
>This current DMARC extension (IETF DMARC PSD)
>draft<https://datatracker.ietf.org/doc/draft-ietf-dmarc-psd/> would
>make it easier for our direct customers (registrants) to setup a common
>DMARC policy for all their subdomains. With this extension they can set
>up the policy in one place, such as the SLD level (second level domain)
>and it will apply to any subdomain they create.  However, since
>feedback leakage can happen due to the nature of the IETF DMARC PSD
>solution, the following proposed alternative could be employed to
>address this issue.
>
>Is the DEMARC defined for dog.animals.com<http://dog.animals.com>?
>
>a.      Yes: then use it
>
>b.      No: then look for DMARC on animals.com<http://animals.com>
>
>Proposed Default Alternative:
>a.      Is the DEMARC defined for
>dog.animals.com<http://dog.animals.com>?
>
>a.      Yes: Then use it
>
>b.      No: Is using the PSD DMARC explicitly permitted by the
>dog.animals.com<http://dog.animals.com> owner in some TXT record (means
>“delegated explicitly to the PSD”)?
>1.      Yes: then look for DMARC onanimals.com<http://animals.com>
>1.      No: terminate
>
>The alternative proposal requires the registrant to explicitly set up
>the default.

How would that work for non-existent domains?

Appendix B describes options to address the issues.  I like that your suggestion doesn't leave it in the hands of the PSO to self assert if PSD DMARC is appropriate, but I wonder why dog.animals.com doesn't just publish a DMARC record?

Scott K