[Mailman-Developers] Building plug-ins for mailman.

[Ian Eiloart]

> On 15 Feb 2015, at 11:21, Stephen J. Turnbull <stephen at xemacs.org> wrote:
> 
> In principle, I agree with Patrick.  Mailman is not the right place
> for DNSBL support or Spamassassin support.  This is not just because
> it's already done in the MTA and/or HTTPd, but also because the MTA
> and HTTPd are better places in any case because they can reject
> without receiving the whole content (which can be very large,
> especially in case of a DoS attack).

I don’t think Exim can. Once it has the sender and recipient addresses, it can either reject the email or ask to receive the whole of the message: headers and body. The exception is when the message exceeds the servers message size limit: but that’s pretty crude. As far as I know it can’t inspect any part of the message until it’s received the whole lot. I’m not sure that the SMTP protocol allows anything different.

However, recent versions of Exim now feature "cut through" routing. They can pass the message to (for example) a list server, and reject the message if the list server rejects the message. This avoids accepting and later bouncing the message, and is a nice feature. However, it doesn’t work well if the message has more than one recipient (in this case, the list).

It’s nice to be able to push spam checking further down the line, because it’s possible that different lists might want different configurations. For example, a health professionals’ list might want to be more liberal about references to body parts, and a finance professionals’ list might want to be more liberal about references to unexpected inheritance!

> Nevertheless, this is a frequently requested feature because many
> Mailman list owners and even site admins lack shell access and access
> to MTA and HTTPd configurations.  I don't much like it (I'd rather
> tell the list admins to get a better host), but OTOH many can't or
> won't, so we may as well give them what they ask for.

-- 
Ian Eiloart
Postmaster, University of Sussex
+44 (0) 1273 87-3148