On Mon 08/Aug/2022 14:45:25 +0200 John Levine wrote:
Actually, small receivers can simply trust selected, DMARC-aligned
mailing lists and restore the original From: in the cases where MLM
saved it (w/o ARC). This kind of hack could be set up really quick. >
Please please can we stop doing this. Trying to unmunge rewritten From:
headers is totally out of scope for this group, and even if it weren't
it does not scale
Symptomatic treatment is out of scope?
Telling people to screw up their lists to avoid damage we caused is blaming
the victim. To make an overwrought analogy, it's like the politicians in
the US telling schools to add reinforced steel doors to keep out crazy
people with guns.
Not quite. Lists are already screwed up, AFAICS. The disturbing symptom
is the munged From: address.
Why doesn't it scale?
Because there are more ways for a forwarder to change a message than you or
I can describe.
That critic applies to my draft, not to unmunging in general. The only
change we care about here is the From: field. While there are many ways to
munge it, there is a simple way to restore it:
IF message is dmarc=pass AND From: domain belongs to $MAILING_LIST_SET
IF Author: is set
RENAME From: Munged-From:
COPY Author: From:
Et voilà!
Isn't that exactly the same problem that ARC poses?
It's similar, but the difference is that ARC actually deals with the
problem and this doesn't. ARC answers the question the recipients care
about, "was this message aligned before it was forwarded?" Your approach
doesn't, and can't if the original message was aligned using SPF.
ARC's added value is only meaningful for receivers whose reputation system
is so sophisticated that that info matters. That is, for global mailbox
providers.
Best
Ale
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