How to Train Thunderbird’s Junk Mail Filter
Junk, junk, and more junk—it seems that some days I get more spam email than I do legitimate email. At least I don’t get as much as Bill Gates, who reportedly receives four million emails a day, most of which are spam.1 If you put your email address out in the Internet space, it is likely at some point that your address will be harvested by spammers and you will become a victim of spam email. Ready to enter a contest that has a prize that looks too good to be true? It just might be that the contest you are entering will lead you down the primrose path to an inbox full of spam (not surprisingly, the entry form probably only asked for your email address). Luckily, Thunderbird has an excellent way to keep spam in check.
Thunderbird uses Bayesian filtering to classify junk mail, which is a system that requires some degree of user intervention and training (see the FAQ on the next page for an explanation of how Bayesian filtering works). In order to train Thunderbird to weed out spam, you have to manually mark messages as Junk by either clicking the Junk icon or going to File | Message | Mark | As Junk. But the important factor to remember here is that you also need to mark your "good" messages by going to Message | Mark | As Not Junk (note that no icon is available for this in the toolbar). That way, you train the filter on both ends and ensure that a better percentage of spam will be captured.
Thunderbird marks junk mail with a junk icon (see Figure 11-1). Note that if you change Thunderbird’s theme (See Chapter 13), the Junk icon will likely not look the same as it does in Thunderbird’s default theme.
Figure 11-1 The Junk icon.