Other efforts to stop Spam

Watching the logs closely after my Greylisting install made me notice just how many attempts are being made to deliver junk to my mail server. I thought I'd add some a few more checks to Postfix so the messages don't even make it to the Greylisting stage. The most effective ones are; requiring a fully qualified HELO string (you'd be surprised how many Spammers just use HELO localhost), and checking that the sender exists before accepting the message. This is done with reject_non_fqdn_hostname under smtpd_recipient_restrictions, and reject_unverified_sender under smtpd_sender_restrictions respectively. A good guide on how to set up sender verification can be found on the Postfix website.