Half a year ago I mentioned greylisting as an option to fight spam. A few months ago NetBSD.org enabled greylisting and it made a huge difference in the amount of spam and viruses being forwarded to me. Now I finally got around to deploying postgrey on the Global Wire mail infrastructure.
Greylisting is so simple that it seems strange that it is as effective as it is. I’m certainly going to enjoy it as long as it keeps working. Unfortunately I don’t expect that to be more than a year…
For implementations of greylisting on different platforms, have a look at greylisting.org.