Review for ExQuilla for Exchange by Mikeyy
Rated 5 out of 5 stars
It's unfortunate that users don't read addon description. It's even more unfortunate that users trashtalk about paid addons.
Thunderbird lost most of it's support from Mozilla because they couldn't find way to monetize it. If you want good, complex and supported addon, you can't expect that for free.
Addons can be bad, not functional, lacking functions, crashy, buggy etc... but you can't trashtalk addon because you have to pay for it.
You as an user always have a choice of not using it.
To create your own collections, you must have a Mozilla Add-ons account.