Review for ThreadBubble by PebbleChamp
Rated 1 out of 5 stars
Umm, this add-on is not necessary. Thunderbird already has the capability of doing this w/o the add-on. All you have to do is go to: Tools->Options->Advanced->Config Editor, and then change the value of mailnews.thread_pane_column_unthreads to FALSE.
To create your own collections, you must have a Mozilla Add-ons account.