[Mailman-Users] Mailman and recipient spam filtering

[Rich Kulawiec]

On Mon, Apr 04, 2016 at 05:30:13PM -0700, Andrew Daviel wrote:
> I have an incident where a rejection message was forwarded to a
> list, and on to other members. I don't know if that was even
> mailman, but it got me thinking.

First, that's because the system which originated the rejection is broken.

All mail systems doing anti-spam/anti-virus/anti-whatever
should *always* reject (if they're going to reject) during the
SMTP conversation (a) because that's most effective and efficient
and (b) because that avoids generating a bounce message, which in
turn avoids backscatter such as you've described.

Second, anything coming back should go to the Sender:, which I
believe defaults to:

	LISTNAME-bounces at LISTHOST

I believe that LISTNAME-bounces, in turn, should be sent by the MTA
in play to:

	"|/usr/local/mailman/mail/mailman bounces LISTNAME"

(although I have it set up like this in the sendmail aliases file:

	LISTNAME-bounces:        "|/usr/local/mailman/mail/mailman bounces LISTNAME", postmaster at LISTHOST

so that the local postmaster gets a copy of the bounce for examination.)

This doesn't necessarily yield the desired outcome, e.g., it may
result in incrementing the bounce count for a subscriber when that
shouldn't really happen, but at least it avoids forwarding backscatter
to an entire mailing list.

---rsk