I’ve been using Mozilla Thunderbird for a very long time now and the main reason for me to stick with it was the built-in spam filter which always did a very good job. But one thing always bothered me: As soon as the computer is under a little stress, Thunderbird will stop identifying spam correctly or forgets to move the mails to the junk folder while actually identifying it correctly. By stress I don’t necessarily mean long and cpu intense tasks, but simple things like opening Firefox or watching a movie. It happened about 5 times a day and I was soon annoyed by my Thunderbird 1.5, however, I took it like a man, because it still filtered and moved about 150-200 international spam emails per day. That’s a pretty good percentage and it would be even better, if it would just move those other 5 into the designated folder after tagging them correctly as spam.

Ultimately, still irritated by this inconsistent behaviour, I recently updated my Thunderbird client to the current beta version Thunderbird 2 Beta 2 hoping for a fix since technically it seems like a rather simple thing to correct. The new Thunderbird now looks nice and new and some features have been added - stuff I wasn’t really looking for, I’m a humble person ;-)

After about a week of testing I have to say that it has gotten a lot worse. Using my old training data, Thundebird now misses about three times the amount of spam emails. While the old version only failed to move spam to the correct folder (displaying the new mail message) most of the time, the new version really has a problem identifying obvious spam emails - no matter what the cpu load says. It’s annoying and disappointing, as far as that can be said for free software.

Now I’m thinking about migrating to Office Outlook, I’ve heard positive opinions about its junk filters, but I don’t think that it’s trainable bayesian. Maybe I’ll give that a try or I’ll go back to Thunderbird 1.5 and live with its erratic behaviour. Years ago, when the world was still a better place, I used to have Outlook Express in combination with the K9 anti spam gateway and it was great up to a certain volume of spam mail or training data. Outlook Express was nice because it’s a simple and fast application and if you’re not too naive, it doesn’t need to be a security risk to your computer. However, it’s old and I don’t believe it’s still being officially supported by Microsoft.

I’ll just keep on searching.