Developer reply by SecondWheel
Rated 1 out of 5 stars
Not maintained
HI there -- I haven't abandoned it, but I haven't had the time to untangle the API changes in Thunderbird yet. Fortunately, it looks like Mozilla has been improving their API documentation, so hopefully I'll be able to get a new release sorted out. Thanks for your patience!
To create your own collections, you must have a Mozilla Add-ons account.