Rejecting at SMTP time (Re: [Techtalk] Testing home mail server)

[Mary]

On Wed, Feb 09, 2005, conor.daly at cod.utvinternet.com wrote:
> I'm just testing my home smtp server.  It's running exim and using the
> eximconfig rule and filter set available from http://www.jcdigita.com/eximconfig
> The idea is that it will reject loads of spam at smtp time rather than loading
> spamassassin with junk.

What are the reasons you're doing this? The most common one is "the
bounce will go straight back to the spammer because it's happening at
SMTP time, and they will realise my address is spam immune!"

This tends not to be true if it's a relay connecting to you (and it
usually is now with spammers): the relay will either ignore the error or
just generate a bounce like usual, which will probably go to some poor
schmoe whose email address was randomly inserted into the envelope from
ie:

 1. Spammer sends spam to relay with envelope from of
    <poorschmoe at example.com>
 2. Spammer disconnects from relay
 3. Relay connects to you and tries to send spam with envelope from of
    <poorschmoe at example.com>
 4. You reject mail
 5. Relay is not originator so generates bounce and sends it to
    <poorschmoe at example.com>.

(Note that <poorschmoe at example.com> can be any address at all, and may
not be associated with the relay or the spammer at all.)

I tend to prefer to accept and silently drop spam (and double for
viruses!) for that reason: reject-at-SMTP-time is not some kind of
magical direct link between you and the spammers.

I can understand wanting to keep mail out of SpamAssassin though. It's a
greedy little beast: has driven my UML machine to the wall on a few
occasions.

-Mary