Kartar.Net

A new spam strategy for me

• Tuesday September 26th, 2006

I get a lot of email. Mountains of the stuff. A fair chunk of it is spam. A consequence of having some older email addresses that still forward mail to me. As a result I spend quite a bit of time perfecting spam defenses. I used amavisd-new, dspam, grey-listing, SpamAssassin, SPF, DK/DKIM, p0f, bogofilter and Anomy and anti-virus all mingled together and tuned to an inch of their lives. My mail server burns some serious memory and CPU and has the world’s most damned complicated Postfix configuration. Recently, however, I threw my hands in the air and said “Enough!” Another approach was needed. So I started doing some investigation and discovered qpmstpd - which is a very fast SMTP proxy written in Perl that comes with plug-ins for a variety of purposes - again all written in Perl. It sits in front of my Postfix and processes mail for spam and then submits it to the queue. After some initial tweaking it worked perfectly and the resulting configuration has greatly - greatly - simplified my mail configuration. The reduction in Postfix complexity alone (I nearly needed a flowchart to work out where mail was routed and injected) makes life considerably easier. The simplified anti-spam configuration in qpsmtpd is also much easier to manage. Initial testing also reveals only a slight increase in spam slipping through and that’ll reduce as I tune SpamAssassin with some more training. Performance is also much improved and my box isn’t sucking up anywhere near as much memory and CPU - which might prolong the lifespan of the box. I did need to add a new plug-in to do SMTP authentication for qpsmtpd. Luckily I found an older, not functional, plug-in that I adapted and fixed. You can find the updated auth_smtpd plug-in at the qpsmtpd wiki. Enjoy.