Back in the day, I ran my own email server, and dealing with spam was a constant pain in the butt. I wrote a spam filter, based on source addresses, "spammy" k

Back in the day, I ran my own email server, and dealing with spam was a constant pain in the butt. I wrote a spam filter, based on source addresses, "spammy" keywords and such, but it was about as effective as you would expect. Most spam had to be classified manually. When I first read "A Plan For Spam", I sat down and wrote a Bayes classifier (pretty much a straightforward implementation of his proposal) in a couple of hours. Due to running my own server, I had a ready-made corpus of hand-curated spam and ham on which to train the classifier. It worked astonishingly well, and I ran that classifier unmodified for another couple of years, until SpamAssassin became good.