Ive been using the default mail app for quite some time now but i keep reading abt how lousy it is, i think it works fine for my usage.
I did play around with other mail clients once. This is due to either the mail app itself going bonkers on me or the server settings from my hosting provider got screwed up after they migrated their servers and did alot of changes on their side.
I used inky for some time but in the end, decided to use gmail for all of my accts. Gmails filtering is the best ive seen so far.
I think Inky was free the last time i used it, not sure about it now.