Re: [dmarc-ietf] Ratchets - Disallow PCT 1-99

[John Levine <[e-mail]>]

It appears that Alessandro Vesely  <[e-mail]> 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.

>  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.

Also remember that ARC is supposed eventually to remove the need for anti-DMARC munging.

R's,
John