[rt-users] Spam control

[Hans-Martin Mosner]

Robert Grasso wrote:
> We are a small company, with some hundreds customers registered for
support;
> so we chose to protect RT using TMDA http://tmda.net/ . This is an
> open-source challenge-response system. This allows us to have a
completely
> spam-free database. Whenever a new customer does not reply to the
challenge,
> the mail is delivered by hand; in our configuration, this is an unusual
> issue.


I don't know your special situation, but from my own experience I can say
that challenge-response systems create even more spam for completely
unrelated users when their address has been used as the sender address in
spam. When I get this kind of backscatter spam, I usually block the
challenge sender.
Please consider using other facilities such as RBLs for spam reduction
first.

Wouldn't it be much better, since you know who your customers are, to
whitelist them and return a mail rejection message in the SMTP dialog when
an unlisted sender tries to send mail to your RT mail address? That
approach only creates backscatter when the mail is getting in via an open
relay host, and it's that host's responsibility to fix it...

Cheers,
Hans-Martin