[Mailman-Users] DMARC and Reply-To lines with from_is_list munging.

[John Levine]

>Arguably, the correct response to DMARC filtering _should_ be the MIME
>encapsulation of list mail, with appropriate RFC 2369 headers added to
>the enclosing MIME structure leaving the content un-munged, with all
>information from the original poster intact.  Arguably, MUAs should be
>transparent to this.  Arguably, this would have been the best design for
>the operation of mailing lists in email-space from the git-go.

Unfortunately, this argument falls over when you note that spammers
and phishers can encapsulate their paypal.com phishes and add list
headers, too.  

The correct response is either for senders to stop publishing DMARC
policies that don't match the way their users use mail (fat chance),
or for recipient systems to skip the DMARC checks on mail from sources
that are known to send mail that recipients want but that doesn't
match DMARC's narrow authentication model, e.g., mailing lists and the
Wall Street Journal's mail-an-article button.

Failing that, all we have left is hacks, none of which are satisfactory.

R's,
John