Review for ThunderSec by Arjan
Rated 4 out of 5 stars
Just installed, and immediately proved it's working on the first spam message received.
Only downside is that it will display its classification errors in classic view only. I use the Thunderbird Conversations addon, and the warning about spam doesn't show up there.
Nevertheless, a good add-on.
To create your own collections, you must have a Mozilla Add-ons account.