@brennen I went through a bunch of them some years ago, but wound up with Mutt just because Thunderbird and Evolution were so, so buggy, and everything else seemed very half-arsed. Since then, though, I've found a fairly minimal graphical client called Geary and I've always been impressed with it.

If you're looking for tag-based mail, Mailpile is probably the closest thing that gives you a Gmail-like experience, but every time I've tried to run it it's felt very alpha. It's been that way for literally four years now.