[Mailman-Developers] anti-spam filter

Barry Warsaw barry at list.org
Fri Apr 19 16:39:40 CEST 2013


On Apr 19, 2013, at 11:48 AM, Ian Eiloart wrote:

>I think Mailman supports SMTP/LMTP calls to discover whether a sender is
>permitted to post to a list, doesn't it?

MM3's LMTP server currently only does a limited sanity check on the messages.
E.g. does the To: field name an existing mailing list[1]

>Exim doesn't handle Milters, but can do the calls forward. Provided Mailman
>is making the judgement, and issuing L/SMTP rejects at L/SMTP time before
>accepting the message, Exim is fine.

As a side note, right now only Postfix is officially supported, mostly because
that's what I use so I can easily debug it.  I would love to have
contributions to support at least Exim and Sendmail out of the box.  If you're
an expert willing to contribute that code, please get in touch.

>Content filtering *could* also be done at L/SMTP time. I think that where the
>Mailman and the MTA installations are managed by the same person or
>organisation, then the better place to have content filtering performed is at
>the MTA, but there might be exceptions to this.

Currently, I'm trying to keep the processing that the LMTP server does at
acceptance time to a minimum, just because I'm concerned about its single
threaded performance.  While it does async I/O, and it runs in a separate
process, time consuming processing for a single message will still block
acceptance of all other messages.

The answer to this is to somehow multiplex the LMTP server, but ideally
without using multiple threads (MM3 is currently single threaded everywhere).
In any case, this would also be interesting to work on.

-Barry

[1] I just noticed https://bugs.launchpad.net/mailman/+bug/1170726


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