Re: [dmarc-ietf] auth-res vs. dmarc

[Todd Herr <[e-mail]>]

On Tue, Dec 29, 2020 at 11:38 AM Michael Thomas <[e-mail]> wrote:

> Mail from this list is being set to DMARC=fail in the authentication
> results even with _DMARC is set to "p=none". My mail provider -- google --
> is the one that is creating that auth-res. I just looked through DMARC and
> AUTH-RES (rfc 7601) and couldn't find any guidance as to what qualifies as
> "fail". Did I overlook something?
>
Your use of the phrase "set to DMARC=fail" indicates to me that you are
interpreting the Authentication-Results header in ways that are different
from my understanding of it.

My understanding of the Authentication-Results header is that it captures
the results of any authentication checks (SPF, DKIM, DMARC) that were
performed on the message. DMARC validation results are independent of the
DMARC policy record, in that any validation result (pass, fail, other) is
possible for any policy value, even p=none.

The intent of the p= value is for the domain owner to communicate a request
for message handling by the entity evaluation the DMARC results; a policy
of p=none means "please treat this message the same as you would have if
you hadn't performed a DMARC check on it, regardless of the result obtained
from the check".

My feeling is that failure should be reserved only in the case where both
> SPF and DKIM fail and that the p= > none. What I'd *really* like from a UI
> standpoint is the p= value passed along as well so I can decide to decorate
> reject differently from quarantine and none.
>
 A typical domain owner with a non-trivial email infrastructure and an
eventual goal of getting to p=reject will start with p=none, and will
consume aggregate and failure reports, and will use the data in those
reports to address any shortcomings in their authentication practices.
Aggregate reports containing DMARC failure verdicts will be quite useful to
the domain owner, to ferret out those cases where Mike in Marketing has
contracted with a third party to send mail on behalf of the domain, or
where Ellen the Engineer has a server running off the side of her desk,
sending reports to $ARBITRARY_MAILBOXES and ensure that such mailstreams
are properly authenticated before updating the DMARC policy to p=quarantine
or p=reject. It's not uncommon for some domains to be at p=none for months,
perhaps twelve or more, depending on their mailing practices and cadences
before making the switch. Domain owners won't move to p=reject until
they're sure that enforcement of such a policy won't have a negative impact
on their mail flow.

-- 

*Todd Herr* | Sr. Technical Program Manager
*e:* [e-mail]
*p:* 703.220.4153


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