Volition

The next best way I've found to cut down on the amount of spam I get is to take my mail server off the air. This is only slightly as crazy as it sounds.

Typically, mail servers will keep retrying to deliver email for up to five days, won't start reporting any delivery problems for up to four hours and tend to process their queue at some regular faction of an hour. In addition, it seems that many spammers use direct delivery (that is, sending directly from their computer to your mail server) as it is easier than finding an open relay.

So the trick is to work out the maximum interval a mail server can be offline while keeping the amount of "undeliverable" warning messages that valid senders get to a tolerable minimum. The longer the mail server is offline, the less spam gets through and if the spammer's software flags the recipients' addresses as being undeliverable, those addresses might even get removed from the spammer's list. Rock!

The downside however is that mail only gets delivered every so often because your mail server is usually offline. It is also a pretty unfriendly thing to do to legitimate people's mail servers and in the end spammers will just start using open relays again if the practice becomes too widespread.

Sigh.