Re: [dmarc-ietf] Ticket #55 - Clarify legal and privacy implications of failure reports

Alessandro Vesely <vesely@tana.it> Sun, 03 January 2021 10:49 UTC

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From: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [dmarc-ietf] Ticket #55 - Clarify legal and privacy implications of failure reports
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On Sat 02/Jan/2021 19:53:41 +0100 Douglas Foster wrote:
> Regarding this section:
> 
>     Experience with DMARC has revealed some issues of interoperability
>     with email in general that require due consideration before
>     deployment, particularly with configurations that can cause mail to
>     be rejected.  These are discussed in Section 9.
> 
> I suggest replacing it with a scope statement, such as this:
> 
> DMARC checks are applicable when a message is received directly from
> the domain owner, or received indirectly from a mediator without
> in-transit modification.  As discussed in Section 9, these two
> criteria do not cover all legitimate email flows.   When a message is
> received indirectly with modification, DMARC cannot produce a usable
> result, and the message should be evaluated using alternate criteria.
>   When messages may have been forwarded with modifications, the
> algorithm for distinguishing between authorized and unauthorized
> messages becomes difficult to define.


I disagree.  Limiting the applicability of DMARC is not going to boost its 
actionable usage.  The above wording boils down to suggesting a sequence of 
operations as follows:

1:  check SPF.  If not pass then the message is indirect.

2:  check DKIM.  If not pass then the message is with modification.  Hence 
DMARC results are not usable.


That would nullify the whole protocol.


Best
Ale
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