[Mailman-Developers] Fixing DMARC problems with .invalid munge

[John Levine]

>>  From: Marissa <mmeyer at yahoo.com.invalid>
>
>I have some sympathy for this approach, as I mentioned over in mailman-users.
>It violates RFCs so I'm not sure Mailman should adopt it, but it's worth
>experimenting with, and I'm glad you (John) are doing so, and providing
>feedback here.

I know the guy who wrote the RFC, and I'm reasonably sure he'd forgive
us under the circumstances.  There is, after all, plenty of mail from
addresses like donotreply at bigbank.com already, and this does the same
thing with slightly different and syntax.  Note that putting the
list's address in From: is also an RFC violation since the list isn't
the author by any normal understanding of the term.

>Message wrapping is the safest but equally unsatisfying.  It's pretty clear to
>me that there are *no* good solution today to DMARC's affect on mailing lists,
>only less bad ones.

The good solution is for the members of the DMARC group to set up and
use a shared DMARC-bypass whitelist for mailing lists and other
legitimate mail sources that don't match DMARC's narrow security model.
I'm working on it, but in the meantime, .INVALID has the advantage of
reminding people where the source of the problem lies.

R's,
John