Choosing a good DNS blacklist to fight email spam
I just came across this page with DNSBL stats. There you can see the acuracy of the relatively new zen.spamhaus.org blacklist is very high. It also has 0% wrong classifications. If you haven’t already done so, you should really add this dns blacklist to your mail server.
If you are using Plesk, it’s very easy. Just go to your mail server settings, activate MAPS spam protection and enter zen.spamhaus.org as the server. It’s that easy!
One word of warning: when you use the same server to send email, you might end up being blocked by the zen blacklist. In that case you are in an ip range that isp’s submitted as “should-not-send-email”. I have not looked into this problem yet, but I feel obligated to tell you this little downside.