TB has big UX problems not mentioned: Search works poorly (Misses too many results to be useful), messages you typed have weird paragraph spacings, and reading multi-message threads is a mess.
Which UX problems? When I read
> Thunderbird’s robust functionality is its superpower, but a dated interface shouldn’t be a barrier to entry for newer users.
I started preparing for the worst.
Search doesn't work on mobile for me at all. On Desktop, I always have to fiddle with filters to find the message I want.
Search does miss a lot of stuff. I hope they never get rid of the option for storing messages in MBOX because I find I have to grep through my messages all the time.