[Bug 1539384] Re: Non-blocking DMARC mitigations should also be done for p=none

Mark Sapiro mark at msapiro.net
Thu Dec 29 18:12:51 EST 2016

Clearly we disagree on this and I don't think either of us will convince
the other to change.

Mailman is trying to enable list owners to cope with DMARC in a way that
minimizes negative impacts on lists and their subscribers. This is an
evolving landscape. Some Microsoft services already are treating mail
with the same address in From: and To: as suspicious which impacts mail
currently DMARC mitigated by Mailman (as well as mail from anonymous

There are initiatives in progress to enable a mailing list to certify
that outgoing mail passed DMARC when it was received by the list
(Authenticated Received Chain <https://datatracker.ietf.org/doc/draft-
ietf-dmarc-arc-protocol/> and <https://datatracker.ietf.org/doc/draft-
ietf-dmarc-arc-usage/>). Thus, Mailman's handling of these things will
likely change in the future.

However, Mailman 2.1's DMARC mitigations are not likely to change, and
for the near term at least Mailman 3 is not going to apply mitigatations
to p=none mail unless the list owner chooses to apply mitigations to all
mail (similar to from_is_list in MM 2.1). Mailman developers believe
this is the correct approach and is RFC compliant.

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  Non-blocking DMARC mitigations should also be done for p=none

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