Perhaps it's a pointless semantic distinction.  I think of DMARC as a mechanism 
for expressing policy about authentication, not an authentication method.

I still don't understand what you think is unprotected.

Scott K

On October 31, 2021 4:48:10 PM UTC, Douglas Foster 
<[email protected]> wrote:
>DMARC is an authentication test also.   The authentication of the first
>identifier (SPF or DKIM) serves as a proxy to authenticate the second
>identifer (FROM), which is conditioned on a satisfactory relationship
>(equal or aligned) between the two domains.
>
>You began to address the issue in your recent post, which included this:
>
>I think that if we changed the relaxed definition to the same as or a
>sub-domain of the From domain it would avoid potential issues like that
>without practical impact.  I don't think I have ever seen legitimate mail
>where Mail From or DKIM signing domain wasn't either the same or a
>sub-domain of From that were in the same org domain.
>
>
>You still need a way to protect the PSL names themselves, and this
>paragraph does not do so.
>
>Exact match to the authenticated domain is always sufficient to
>authenticate the FROM domain.
>
>>From a trust standpoint, the greatest trust occurs when the authenticated
>identifier (SPF or DKIM) is the parent of the second identifier (FROM).
>Based on my observed data, I agree that the norm is for FROM to be the
>parent or the equal, rarely the child.   I should be able to provide some
>data.   I will not have data about cousin relationships (unit1.example.com
>aligned with unit2.example.com).
>
>Doug
>
>On Sun, Oct 31, 2021 at 11:30 AM Scott Kitterman <[email protected]>
>wrote:
>
>> Neither SPF nor DKIM use the PSL, so I still don't understand.  What do
>> you mean by "authentication testing"?
>>
>> Scott K
>>
>>

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