Review for Identity Chooser by Torsten Villnow
Rated 4 out of 5 stars
I very much like this add-on.
However, there is an issue with creating posts for a newsgroup: the name of the newsgroup is not automatically filled-in in the address of the post, as it is done by Thunderbird without this add-on activated.
To create your own collections, you must have a Mozilla Add-ons account.