Re: [dmarc-ietf] Tree Walk Damage

As a participant, I fully disagree with the second paragraph of this.
The justification for changing the mechanism is that in cases where
the mechanisms differ, the tree walk produces results that are more
likely to represent the intent of the sending side than consulting the
PSL does.  This has been borne out by cases we have actually seen,
which says to me that the change is the right thing to do.

It is certainly possible that we will find cases where the PSL gives a
better answer than the tree walk does.  We can construct such cases in
theory, but haven't found real-world ones yet, and that's telling.
Moreover, if, as I think we have done, we have made the situation
better overall, we have done the right thing, and we simply need to
document what organizations can do with their DMARC policies to fix
things if they fall into such a tiny corner case.

Barry

On Wed, May 3, 2023 at 6:46 AM Douglas Foster
<dougfoster.emailstandards@gmail.com> wrote:
>
> I have opened issue 113 to formally document my strong objections to the current tree walk:
>
> Current DMARC policies are configured based on RFC7489 and the PSL, and evaluators obtain results based on those implementation decisions. Domain owners may have many reasons to want an alternative to the PSL: (1) The PSL may contain errors that impact the domain owner's mail flow. (2) The PSL is implemented in different iterations by different evaluators. (3) The RFC7489 / PSL algorithm does not allow for partitioned alignment within an organization.
>
> Nonetheless, an evaluator has no justification for implementing an algorithm which produces different results unless the domain owner indicates that he prefers usage of that different algorithm. This can be accomplished by tagging his DMARC policies to indicate which of the four possible roles applies to a particular policy: Org Top, Subdomain, Org Top-and-Bottom (single label registry), and Org Bottom (bottom layer of a multiple-layer private registry), and DMARCbis should define those tags The current upward-walk proposal will cause damage by directing evaluators to apply an undesired and often incorrect re-interpretation of domain owner intent and associated alignment boundaries.
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