[plug] Mail domain auth

[James Henstridge]

On Fri, 24 Oct 2025 at 07:57, Harry McNally via plug <plug at plug.org.au> wrote:
> Hi James
>
> I just spotted that Valerie of the Internet Resiliency movement has the list working like this.
>
> Subject:    [IRC] Meetup in Utrecht?
> Date:        Thu, 23 Oct 2025 19:17:53 +0300
> From:        Valerie Aurora via IRC <irc at lists.bowshock.nl>
> Reply-To:   Valerie Aurora <val at bowshock.nl>
> To:            IRC <irc at lists.bowshock.nl>
>
> That list:
>
> IRC mailing list
> IRC at lists.bowshock.nl
> https://lists.bowshock.nl/mailman/listinfo/irc
> Documentation and FAQ https://bowshock.nl/irc/
>
> Munge all the things might be the new approach.

This is the type of "from" header munging I'm talking about. It looks
like Valerie's domain is set up with a quarantine DMARC policy, so
would be munged by our list's current configuration:

$ host -t TXT _dmarc.bowshock.nl
_dmarc.bowshock.nl descriptive text "v=DMARC1;p=quarantine;"

If it is doing the same for posts by other users (e.g. those with
gmail.com addresses), then they would indeed be doing the header
munging unconditionally rather than just as a mitigation against
stricter DMARC policies.

James.