I've used it for decades and still recommend it to others (mainly becauce I never invested in trying enough other cross-platform alternatives), but 'great' wouldn't be a word I'd use to describe it, there are just so many little quirks and annoyances, to the point I often have the feeling using it is constantly working around and/or ignoring those.
To me there is not a single client which isn't off somehow, missing something. I feel like nobody really loves mail client development, because email kinda sucks. Mail just needs to die IMO. You wouldn't design something like email today. I wouldn't want to support all the legacy "features" either. It's a wonder someone is caring about these clients at all.
It's not like mail is going anywhere soon. Look at the fax. There is many decades of infuriating mail client dependecy ahead.
Yes, by "great" I guess I meant "great in comparison to other desktop email clients". KMail for example comes with its own set of quirks and annoyances, many that are similar to Thunderbird's with regards to general UX.
I've used it for decades and still recommend it to others (mainly becauce I never invested in trying enough other cross-platform alternatives), but 'great' wouldn't be a word I'd use to describe it, there are just so many little quirks and annoyances, to the point I often have the feeling using it is constantly working around and/or ignoring those.