To correct my last post, we are not reduced to using a list, as we have
already anticipated this situation with the PSD flag.

The solution to the sub-lease situation is for the parent domain to publish
psd=y.

We may need two PSD flag, one for
"I am a real PSD and never send mail and should not be used for alignment"
and a second one for
"I am a lease-granter but I send my own mail, but I should not be used for
alignment".
I think we can get by with one flag, but am open to either possibility.

About sister domains, we have already litigated the question of sister
domains.   Under RFC 7489, they are considered aligned, although perhaps
not in your implementation.  If we change that interpretation, we change
DMARC versions, but I heard no enthusiasm for doing so.

The broken alignment calculation is an artifact of one proposed revision of
the tree walk.   It is neither the necessary algorithm nor the best one.

DF


On Sat, Jan 22, 2022 at 11:32 AM Dotzero <[email protected]> wrote:

>
>
> On Sat, Jan 22, 2022 at 11:02 AM Douglas Foster <
> [email protected]> wrote:
>
>> If a.b.example.com is considered aligned with c.example.com under
>> RFC7489, but will be considered unaligned under DMARCbis, then we have a
>> pretty significant incompatibility and need to move to DMARCv2.
>>
>> In the current example of comparing a.b.example.com and c.example.com to
>> each other:  if there is a shared DMARC policy at example.com, why would
>> we not consider the two names in alignment?
>>
>
> The alignment is because of the parent domain, not because of the sibling
> domains. A distinctly different situation.
>
>>
>> In the case of organizations that lease subdomains, do both the
>> subdomains and the parent domain send email and publish DMARC policies?
>>  If so, then we are back to needing a PSL.
>>
>
> The practice can/will vary. There isn't a need for a PSL if alignment is
> not allowed based on a sibling domain's published policy. There would still
> be potential problems with alignment based on the parent domain but nowhere
> near as ugly.
>
> Michael Hammer
>
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