[Mozilla Enterprise] ESR mailing list forwarding gives rise to DMARC "failures"

[Paul Kosinski]

Yes, I know that SPF, DKIM and DMARC can cause problems with mailing
lists, but people have been working on it for years. I just thought that
Mozilla was sophisticated enough to have implemented a workaround.

The ISC BIND users mailing list, for example, uses Mailman and in their
configuration the DMARC handler, modifies the "From:" address and adds
"Reply-To:" like so:

  Paul Kosinski via bind-users <bind-users at lists.isc.org>
  Reply-to: Paul Kosinski <bind at iment.com>

The ClamAV users mailing list does something similar, also changing
"From:", adding "Reply-to:", but also adding a "Cc:" like so:

  From: Paul Kosinski via clamav-users <clamav-users at lists.clamav.net>
  Reply-To: ClamAV users ML <clamav-users at lists.clamav.net>
  Cc: Paul Kosinski <clamav-users at iment.com>

Topicbox also uses the "From:" "via" workaround. It's a shame that
Mozilla doesn't do something to mitigate its DMARC problem.

P.S. Since DMARC info is supplied by the DNS server and applies to the
whole domain, I don't see offhand what to do that would accommodate
Mozilla's rather lame mailing list mechanism.



On Sun, 14 Jul 2019 16:45:59 -0500
Don Wright <wmail at wricomp.com> wrote:

> Paul Kosinski wrote:
> >Here's another example of a DMARC "failure" when mail (from me) is
> >passed on to an ESR subscriber.
> 
> 
> DMARC is fundamentally broken[1] with regard to mailing lists as it
> only checks the From: and not the Sender: field. Mitigating
> DMARC-induced problems is a frequent topic on the mailman-users
> support mailing list.[2]
> 
> 
> [1] https://en.wikipedia.org/wiki/DMARC#Mailing_lists
> [2] https://mail.python.org/mailman/listinfo/mailman-users