Yeah, Gmail has probably the best spam filtering of any mail service in the world. But! You can do pretty well at it, too, if you feel like putting in the effo

Yeah, Gmail has probably the best spam filtering of any mail service in the world. But! You can do pretty well at it, too, if you feel like putting in the effort. I host email for some clients, and most of my sysadmin time these days is spent dealing with spam in some fashion or another. 1. Greylisting. Greylisting is fantastic, and the package you're looking for here is sqlgrey. It's easy to use and admin and it has sensible defaults. You can pretty much just drop it in and immediately get an 80% reduction in spam. 2. Use the right MTA stack: currently I think that's Postfix and Dovecot. Postfix and Dovecot go together like ice cream and apple pie. Postfix is far easier to admin and configure than Sendmail, and Dovecot has good support for managesieve, which'll be important in a moment. 3. Install SpamAssassin and AMaViS. Getting it working correctly with Postfix in a multi-domain environment, so that each user can have their own SA settings, is a little bit tricky, but totally worth it. AMaViS by default wants to manage SA's settings. Don't let it. 4. Install the managesieve, password, and sauserprefs plugins. Now you can change your email password, your filters, and your SpamAssassin preferences right from the webmail interface. 5. Configure SpamAssassin to label messages "[SPAM]" (it also sets the X-Spam-Flag header) on junk messages, and then set up a default filter in managesieve to redirect those things to Junk folder. Bam, no missing emails, no cluttered inbox. Use imap on your favorite devices. 6. A couple of extras, like Fail2Ban, will help too. You can modify Fail2Ban to watch your mail.log for frequent attempts at nonexistent user accounts and then iptables those spammers. As with most things, you can spend as much additional time as you'd like fine tuning this, writing some custom software, and so on. But, the above will get you about 98% of the way to Gmail's level of spam filtering in about a day's worth of work.