Hi Kyle, just getting back to this now.

Kyle Meyer <kyle@kyleam.com> writes:

> Liam Hupfer writes:

>> I noticed some messages involving debbugs end up with “via <list name>”
>> in the From header, but not others.
>
> My understanding is that this From rewriting is due to how the admins
> have configured Mailman.
>
>   <https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/handlers/docs/dmarc-mitigations.html>
>
> Here’s a previous discussion related to this on guix-devel:
>
>   <https://yhetil.org/guix-devel/87pn2kyo2c.fsf@kyleam.com/T/#u>
>
>> As far as I can tell, these rewritten From headers don’t show up in
>> the archives at lists.gnu.org or debbugs.gnu.org.
>
> I don’t know what the underlying setup is there, but my guess is that
> those services get the messages before the rewrite.  yhetil.org receives
> messages as any regular list subscriber would.
>
> If you look through other archives (e.g.,
> <https://www.mail-archive.com/bug-guix@gnu.org/>), you’ll spot some
> “via” senders.

Yup, I see them on emacs-devel as well. I think you’re exactly right about all
of this (as well as the bit about different configurations (no DKIM)
likely causing the differing behavior given a particular sender).

I did some more digging and found that Konstantin Ryabitsev’s [Subspace
mailing list server announcement] discusses appeasing DMARC. He argues
that mailing lists shouldn’t have to munge the From header assuming they
set the envelope-from address to the list domain and don’t fiddle with
any DKIM-signed content. I’m inclined to take the kernel.org list
administrator at his word on the subject.

So I guess I would have to convince the Mailman 2 maintainers to expose
this DMARC mitigation policy (or lack thereof) as an option, and then
convince the GNU sysadmins to upgrade. No idea how feasible that is.

For now, I set `p=none' in my DMARC record. Not ideal, but I don’t think
I’m at much risk of impersonation anyway.

Thanks for pointing me in the right direction!

—Liam


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