[Mailman-Users] Excessive bounces to list members on my list

[Stephen J. Turnbull]

Gregori Kurtzman, DDS writes:

Your address <drimplants at aol.com.dmarc.invalid> is invalid, I hope
you're reading the list.

 > Need some insight and help. I have recently taken over a list that
 > is using mailman v 2.1.14. And we are getting a lot of bounce
 > notices regarding members and de-activation's of their
 > subscriptions due to this.  In the bounce notices I get as list
 > manager I see the following  'This message failed DMARC Evaluation"
 > Also members are complaining they see no messages coming from the
 > list or even their own posts.

Yahoo! and AOL have decided that you are not allowed to forward
messages from their members, and enforce it using a DMARC policy which
requests that receiving mail servers bounce the mail, effectively
causing a denial of service attack on their own users.  Large services
like Yahoo, AOL, and Hotmail seem to be respecting the policy despite
the adverse effect on their users (ie, getting unsubscribed).  GMail
seems to have a more nuanced response so that at least some mailing
lists get through.

The problem occurs with posts *by* users with Yahoo and AOL addresses,
although it is experienced by your entire subscriber base (that is,
any subscriber at a service which respects the DMARC policy).

There is no generally satisfactory way for mailing lists to deal with
this.  Several options and a lot of discussion are in the threads with
"DMARC" or "Yahoo" in the subject at

    http://www.mail-archive.com/mailman-users%40python.org/

tl;dr summary is

    http://www.mail-archive.com/mailman-users%40python.org/msg63959.html

The most palatable option for most list operators seems likely to be
setting the "from_is_list" option, but that requires Mailman >= 2.1.16
(avoid 2.1.17, IIRC it has a related bug that needs to be patched for
from_is_list to work properly, and 2.1.18 is not quite released yet,
but should come out literally any day now).

Whatever option you adopt for your list, your AOL and Yahoo users
should be advised that their email provider's policy is causing the
problem, and that they can defend themselves by switching providers
(GMail seems to be handling the situation best at the moment).  You
probably don't want to *advocate* switching, but that's up to you.
However, it *is* an effective remedy for the subscriber, if they are
willing to pay the (often substantial) annoyance cost of switching
email addresses.

Regards