On Sat 17/Sep/2022 04:46:58 +0200 John R Levine via mailop wrote:
On Fri, 16 Sep 2022, Brandon Long wrote:
For thirty years we all used mailing lists that didn't mess with the
author's name or address
but the reason we added the signature and linkage was because of bad
actors, and the number of "we always did it this way" things that
have fallen to our fight with bad actors has been quite large.
I think we both hope that ARC turns out to be an adequate band-aid to increase
the amount of legitimate mail that DMARC can handle so that the most painful
failures work again.
Yes, ARC can fix what DMARC broke. The only bit I haven't worked out yet is
how to decide whether to trust an ARC-signing domain. It is not a lightweight
decision, given the security implications. Those of us who run a personal MTA
have an obvious solution. But what about large mail sites?
Perhaps, a large mail site could keep a per-user list of ARC-trusted domains.
Since email messages are sent, using VERP, to a single recipient at a time,
verification would be straightforward. So, when a user knows that mailop.org,
say (if they ARC-signed messages), is trusted by her MX, at least for messages
where she's the only recipient, she could disable the From: munging option in
her list settings. Would that work?
I'd be happy to add the point of view of a large site on trust management to a
memo I'm drafting on this topic:
https://datatracker.ietf.org/doc/html/draft-vesely-dmarc-mlm-transform
Section 3 in particular.
Best
Ale
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