Thunderbird:Help Documentation:Dealing with Junk E-mail: Difference between revisions

The filter improves as it watches how you sort your e-mail, and with time the filter will reach nearly 100% classification accuracy.  More important, however, is that the filter is intentionally conservative in what it marks as junk mail.  If Thunderbird can't quite decide whether an e-mail is junk or not, it will mark it as not spam.  It's that simple -- after training, the filter simply doesn't create false positives.