On Thu, 2 Jan 2020 15:30:28 -0800
Rick Moen <rick@???> wrote:

> Because GMail
> enforces at the time of receipt the declared DMARC policies of what
> is asserted to be the source domain of an arriving mail, and because
> yahoo.com has an r=reject DMARC policy and its declared roster of
> authorised origins for yahoo.com mail doesn't include Dng's MTA host,
> Gmail 55x-rejects Gmail User's copy. He/she never sees Yahoo User's
> posting. Worse, Mailman takes note of the 55x rejetion, and
> increments GMail User's bounce score, in effect sanctioning Gmail
> User for Yahoo User's domain's (IMO) problem-causing antiforgery
> procedures.
>
> After a few such incidents, Gmail User gets his/her delivery disabled
> and eventually unsubscribed.

Thank you for the lesson. It all, and I think the above in particular,
is just the thing I needed to learn to approach the admins of the list
I've had such problems with.

Now I can move away from "nefarious shadowbanning" to actual
troubleshooting.

(This topic is new to me. I always thought email was wholly
unreliable and we'd one day just use PGP for actual authenticity.)