On Thu 22/Jul/2021 20:51:05 +0200 John Levine wrote:
It appears that Alessandro Vesely <[email protected]> said:
On Wed 21/Jul/2021 20:05:41 +0200 Matthäus Wander wrote:
Alessandro Vesely wrote on 2021-07-21 19:41:
Some lists operate the evasion hack, a.k.a. From: munging, only if the sender
has p=quarantine or p=reject, some do it unconditionally, some only if the
mail is outbound, some only if the receiver is mail.ru. Behavior doesn't seem
to be settled yet.
We should add a section on From: munging in the spec.
It's explained as mitigation in RFC7960:
<https://datatracker.ietf.org/doc/html/rfc7960#section-4.1.3.1>
What's seems to be missing is a recommendation to not change DMARC validation
behavior subject to p= or other conditions. A conditional validation makes
p=none less useful for monitoring of potential delivery problems.
I agree that it's easier to deal with From: munging when it's done uniformly on
all messages.
Lists change messages in all sorts of ways, not just for DMARC, and if
you want to try to unmunge them (mostly a losing battle in my
experience) you end up with an ever growing list of patterns and
replacements.
Yeah, for example X-Mailman-Original-DKIM-Signature. It still seems to be
manageable, though.
However, I'm not sure whether to actually RECOMMEND to do so.
That's simple: no. I can't imagine why we would expect list operators to take
list
management instructions from the people who screwed up their lists in the first
place.
:-)
Yet, From: munging itself resulted from cooperation between dmarcers and MLM
people, didn't it?
Also remember that ARC is supposed eventually to remove the need for anti-DMARC
munging.
What I imagine can happen is that receivers who can work out how to trust ARC
will unmunge messages based on Original-From:, Author:, or similar field when
ARC validates it. Unmunging based on undoing list changes is an alternative.
Neither method seems to reliably work every time for every one. Therefore,
From: munging is going to stay.
Best
Ale
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