From: Craig on
I'll be trying this... ;-)

The author of JunQuilla addresses how to take advantage of TB 3.x's junk
filtering.

> Thunderbird since version 3 has had experimental support for junk
> filtering in newsgroups. The feature basically works fine, but the
> user interface mostly fights against your attempts to use it. I�d
> like to give brief instructions here for anyone who wants to try it.
>
> You�ll need to install my addon JunQuilla to enable one critical
> piece of user interface. JunQuilla supports a folder property that
> lets you selectively enable or disable junk processing for a tree of
> folders. So after you�ve installed JunQuilla, enable processing of
> junk for a newsgroup

<http://mesquilla.com/2010/07/21/junk-management-for-newsgroups-in-thunderbird-3/>

--
-Craig