Option 1: Either what those providers has decided to do is
actually the right option or, because they are a family of 500
pound gorillas, they are going to get their way and we need to
go along. If that is the correct or preferred way of looking at
this, then we should modify our servers to do what they like or
to work around the problems they create. We can have a WG try
to make minor improvements in (in this case) DMARC, but with the
understanding that anything that modifies the contents of
"From:" violates the definition and semantics of that field as
identifying the human message originator and noting that we've
got "Sender:" and "Resent-*" fields that are intended for
situations in which the last entity to inject the message into
Internet mail is not the same as the human message originator
and that we, like a few centuries of postal services before us,
made a distinction between envelope and message header
information for a reason.
No idea how flexible mailman is, but how hard would it be to write some
code that
- detects if DMARC is in use
- if so copies the original From header and other headers worth preserving
to something like X-Original-From, etc.
- and rewrites the From to a constant string:
"This user mistakenly uses a DMARC protected system, see <some page that
describes what is wrong>" <no-such-user@no-domain.invalid>
Using a constant string maximizes the incentive to use a proper mail server.