Thursday, August 17, 2006

more on anti-spam

In response to my last entry about anti-spam measures and the difficulty of blocking SPAM at the SMTP protocol level I received a few responses. Brian May pointed out that the exiscan-acl feature of Exim allows such blocking, and Johannes Berg referred me to his web site http://johannes.sipsolutions.net/Projects for information on how he implemented Exim SPAM blocking at the SMTP level.

It seems that this is not possible in Postfix at this time. The only way I know of to do this in Postfix would be to have a SMTP proxy in front of the Postfix server that implements the anti-SPAM features. I have considered doing this in the past but not had enough time.

Also a comment on my blog criticises SORBS for blocking Tor (an anonymous Internet system). As I don't want to receive anonymous email and none of the companies I work for want to receive it either this is something I consider a feature not a bug!

4 comments:

chithanh said...

The criticism is not about blocking anonymous email. As explained in the abuse-faq, SORBS is blocking Tor servers regardless of their exit policy. So even if outgoing Tor connections on port 25 are disallowed (which is the default), SORBS may still block anything that comes from this server.

Chris Samuel said...

Postfix works for this just fine, I've been doing just that for years with it!

Thanks for permitting comments without having to sign up for an account by the way, it's very much appreciated!

Chris

Hez said...

Have you tried qpsmtpd? It is quite simple to setup, and the many plugins make it quite flexible.

Giacomo said...

Is milter not enough? milter is designed for sendmail, but also courier-mta, postfix and other have support for milter. Milter is a SMTP level filter protocol, originally designed for sendmail, and spamassassin and clamav supports also milter.