[Bimi] BIMI/DMARC & PSL vs Tree-walk

["Brotman, Alex" <[e-mail]>]

Hey folks,

With DMARCbis, the current draft illustrates a method by which the DMARC policy is discovered via a tree-walk instead of utilizing the PSL.  I'm not trying to hash out the decision for DMARCbis to do that, there's a different list for that.  I do have a couple of questions how this relates to BIMI.

Assumptions:
1) Message is coming from 5322.From domain "marketing.emails.example.org".  No DMARC or BIMI policy declared here
2) There exists a DMARC policy at example.org for p="reject" and a BIMI policy at example.org
3) There exists a DMARC policy at emails.example.org, p="none", no BIMI policy declared here
4) All authentication aligns/passes
5) 7489 would have found the DMARC policy at "example.org", DMARCbis will find policy at "emails.example.org" 

Questions:
1) Does it matter that the DMARC policy and BIMI policy live in different locations?
2) Do we care if the DMARC policy is different?  The apex domain is still p=reject.  However, by inheritance, the exact 5322.From domain is no longer protected by DMARC (with a policy of "none").  This wouldn't have happened with the PSL method.
3) If 1/2 are problematic, does BIMI need to consider a tree-walk method?  That seems like it may be less ideal as it may not protect the apex domain.
4) Or is this just not a problem at all?

Thanks

--
Alex Brotman
Sr. Engineer, Anti-Abuse & Messaging Policy
Comcast