Re: [dmarc-ietf] Proposed text for p=reject and indirect mail flows

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

I’m just not sure how we determine what is high-value.

comcast.com: p=reject
comcast.net: p=none
xfinity.com: p=quarantine

The top one is corporate, middle is consumer, bottom is consumer (but not actually used) & customer comms (sub-domains).  They’re all used in various ways for internal messaging.  Should I tell our corporate admins that they need to no longer publish p=reject?  They’re violating the RFC by doing so?  There are very few consumer-oriented messages that originate from comcast.com.  Are we doing it right?  It makes things a little harder when one of our employees wants to use a mailing list.  But that still feels like the right thing to do.

If it’s not obvious, I’m having a hard time with “MUST NOT”, and dictating to domain owners what is in their best interests, regardless of our perceived value of their domain.

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

From: dmarc <[e-mail]> On Behalf Of Barry Leiba
Sent: Wednesday, March 29, 2023 10:15 AM
To: Todd Herr <todd.herr=[e-mail]>
Cc: [e-mail]
Subject: Re: [dmarc-ietf] Proposed text for p=reject and indirect mail flows

I'm very much against text such as this, as I think it encourages deployments that are contrary to interoperability and to the intent of p=reject.

I contend that p=reject (as with the similar construct in the older ADSP) was intended for high-value domains and transactional mail, and that it was never intended for use in domains where general users send general email.

I stand by the MUST NOT that I proposed.

Barry


On Wed, Mar 29, 2023 at 10:33 PM Todd Herr <todd.herr=[e-mail]<mailto:[e-mail]>> wrote:
On Tue, Mar 28, 2023 at 9:06 PM Pete Resnick <[e-mail]<mailto:[e-mail]>> wrote:

If you agree that interoperability is increased, then I'd suggest that you actually do agree that the proposed text is appropriate.


I don't know that I agree that interoperability is increased...

I'm having trouble squaring proposed language that says "Domain owners MUST NOT publish p=reject because it breaks interoperability" with the following language from section 5.8:


Mail Receivers **MAY** choose to accept email that fails the DMARC

mechanism check even if the published Domain Owner Assessment Policy

is "reject". In particular, because of the considerations discussed

in [@!RFC7960], it is important that Mail Receivers **SHOULD NOT** reject

messages solely because of a published policy of "reject", but that

they apply other knowledge and analysis to avoid situations such as

rejection of legitimate messages sent in ways that DMARC cannot
describe, harm to the operation of mailing lists, and similar.

It seems inconsistent to state with certainty that authorized mail will be rejected due to authentication breakage when there is no requirement that a reject policy be honored (and we have plenty of evidence that Mail Receivers are following the 'SHOULD NOT reject messages' guidance).

Language that would be more consistent in guidance to the domain owners might look something like this:

After careful analysis of the aggregate report data as described in section 5.5.5
(Collect and Analyze Reports), Domain Owners **MAY** choose to change their
policy from 'none' to 'quarantine' or 'reject'. If, in the Domain Owner's judgement,
unauthorized and deceptive use of its domain name in the RFC5322.From field puts
at risk the trust it has built with its recipients, then it is **RECOMMENDED** that
the Domain Owner make use of the p and/or sp tags to set policy to 'quarantine' or
'reject' for those streams most at risk of loss of trust.

If going that route, probably want to consider expanding on 5.5.5, too; I need to think about it some more.

--
Todd Herr | Technical Director, Standards and Ecosystem
e: [e-mail]<mailto:[e-mail]>
m: 703.220.4153

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