The best way to avoid getting Spam in your inbox is by preventing it from getting to your server in the first place. That is where “greylisting” comes in.

I recently installed a Greylisting daemon called Postgrey on my Ubuntu Linux mail server and it is awesome. It has reduced the amount of Spam that makes it to my Postfix mail server by at least 90%. The result? My server wastes far less resources on categorizing mail (Spamassassin is awesome, but its a resource hog). And much less Spam in my inboxes.

For a technical explanation of greylisting, checkout www.greylisting.org.

Whether you run Sendmail, Qmail, Exim, or Postfix, I highly recommend checking out the range of greylisting daemons that are available. It is time well spent.

If you run a Microsoft Exchange server, there are commercial greylisting solutions available. But your most secure, and likely most affordable, solution is to put a Linux or BSD based server between your Exchange server and the Internet.