[Mailman-Users] Delivery errors and spam grading

Stephen J. Turnbull turnbull.stephen.fw at u.tsukuba.ac.jp
Mon Mar 18 08:39:02 EDT 2019

Davide Marchi writes:

 > 1) How is it possible from Mailman monitor the delivery errors? Only 
 > sysadmin mail server from the logs?

That depends on what you mean by "monitor" and "delivery errors".  If
you mean mail refused by some system (typically the final recipient)
and returned to Mailman, that is what we call "bounces".  Mailman can
be configured on the [Bounce processing] screen to send mail to the
list owner (only, not moderators or the site administrator) four types
of notifications about bounces.  The default is usually appropriate.

In some cases recipient systems don't identify the bounced recipient.
In that case you can use VERP as described below, which arranges that
Mailman receives all bounces in such a way that the recipient can be
identified (a special-purpose return address is allocated per

There is no web-based monitor in Mailman 2.  These notifications are
sent by email to the list owner.  However, if your email provider uses
a web-based manager like cPanel, you may have some access to this
information (I don't use cPanel, so I don't know what features it
provides for monitoring system health).

If you mean any other kind of delivery failure that is detected by the
Mailman host, but is not returned to Mailman, then it is simply
impossible for Mailman to even be aware of them, and you would have to
check the MTA (mail server) logs.  And of course there are delivery
errors that happen and never are returned to the Mailman host at all
(you find out about these because subscribers tell you).  There's
nothing that can be done about those by Mailman, either.

 > 2) Is it possible avoid spam grading

You should set DMARC Moderation Action to Munge From in the [Privacy
options -- Sender filters] screen.  (Strictly speaking this isn't spam
filtering, it's mitigating breakage induced by incompetent email
providers.)  And of course you should filter incoming mail for spam
(and if you have any human users besides root on the Mailman host,
outgoing mail too -- this is why it's a good idea to have a dedicated
host for Mailman!)  The MTA should be set up to use DKIM and SPF.

 > increasing the number of sending sessions/decreasing individual
 > emails sent per session?

It's not obvious to me that this is very useful: most of the big
providers count the number of times a message is received by any
method.  They don't care if you do it one at a time (although they may
shut you down before any mail is delivered if they are counting the
recipients per session).  The usual reason for throttling is because
Mailman's provider doesn't like accepting huge numbers of addressees
from Mailman, not because you have tons of subscribers at one

Only very crudely, in a site-wide way or very drastically per-list.
The site-wide option works with Mailman's internal "SMTPDirect"
DELIVERY_MODULE (which is the default).  Set SMTP_MAX_RCPTS to some
"reasonable" figure in mm_cfg.py.  This applies to all outgoing

Alternatively, you can set VERP_INTERVAL=1 in mm_cfg.py, which ensures
that every message is a one-subscriber-per-SMTP-session sitewide, or
for each list you can enable Personalization in the [Non-digest
options] which has the same effect for one list.  (You probably should
also disable the Digestable option in [Digest options].


More information about the Mailman-Users mailing list