Thunderbird junk mail filter problems

You may be interested in the JunQuilla extension for Thunderbird. It requires Thunderbird 3.0 or later.

It has the ability to show the bayesian junk rating of your messages as a percentage (among other things).

Info here: http://mesquilla.com/extensions/junquilla/

I assume you've seen this article: Junk Mail Controls. There's also a link to this somewhat old article: Junk messages not moved. This forum thread may prove helpful to you as well: Enable junk filter logging.

Good luck!

See http://kb.mozillazine.org/Junk_Mail_Controls#Tweaking_the_Junk_Mail_Controls

In Thunderbird:
You can change the preference using Tools -> Options -> Advanced -> General -> Config Editor. Enter "junk" in the Filter field to show only the preferences that contain "junk" in their name, and then double-click on mail.adaptivefilters.junk_threshold, enter a value lower than the default 90 in the edit field and press the OK button. Many users report good results with values of 30 or lower.