[berkes]

I've used thunderbird for over 20 years and used many others inbetween: sylpheed, the bat, evolution, kmail, Pegasus.

I still have Thunderbird installed and configured for the odd "advanced task", but my daily driver has been Geary for over 10 years now. Precisely because its so much better looking than thunderbird.

Looks, done properly, are an important part of a good UX. For me, less clutter, more whitespace, clearer focus, works far better than the "widgets thrown onto a square" that Thunderbird is (I have ADHD, it may contribute to this preference for clean, simple, focused design)