Colleagues,

I am of the belief that if and when DKIM2 reaches a state of widespread
adoption, there is no longer a need for Domain Owners signing with DKIM2 to
participate in DMARC, a belief I expressed during the IETF 122 meeting. I
did not hear consensus for my belief, but I still don't understand the
reasons that I might be in the weeds on this, so I'm asking for
further clarification here, perhaps in small words so that I can better
understand.

Let me preface my remarks here by saying that, as I am co-editor for
DMARCbis, it might be assumed that I'm trying to protect my turf by asking
this question, and that I'm pursuing some quest to wreck DKIM2 because of
that. I assure you that nothing could be further from the truth; rather,
I'm interested in making the email ecosystem better by whatever means make
it better.

Here is what I currently understand to be true:

   - DMARC provides the ability for a Domain Owner to request handling for
   messages that fail email validation (SPF and DKIM) and to receive reports
   about use of its domain
   - DKIM2, as currently described, allows and even encourages receivers to
   reject messages that fail DKIM2 validation

To my mind, such rejection removes the need for a Domain Owner to express a
preference, as the decision will be made independently of any such
preference. Moreover it removes the need for any kind of reporting, as a
Domain Owner will know from the rejections which messages that it
authorized failed to authenticate and presumably why, and the Domain Owner
will never see the rejections of unauthorized messages that did not
originate at the behest of the Domain Owner, with the latter class of
rejections being ones that the Domain Owner wouldn't find actionable,
anyway.

So, assuming a future world where a DKIM2 specification includes the text
"Mail Receivers SHOULD reject any message that fails DKIM2 validation" or
similar,  and DKIM2 is widely adopted by mailbox providers and MTA vendors,
I have some questions about that world:

   - Why would a Mail Receiver accept a message that fails DKIM2 validation?
   - Why would a Domain Owner publish a DMARC policy record when it's
   sending mail that is DKIM2-signed?
   - What would anyone hope to gain by issuing or consuming DMARC reports
   showing messages that failed DKIM2 validation but were accepted in spite of
   such failure?

Thanks, and safe travels back from Bangkok to those who were there in
person.

-- 
Todd Herr
Some Guy in VA LLC
t...@someguyinva.com
703-220-4153
Book Time With Me: https://calendar.app.google/tGDuDzbThBdTp3Wx8
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