Have to recommend Postbox as well. It is the only mail client that could integrate with my school's terrible email server, which saved me from using their broke

Have to recommend Postbox as well. It is the only mail client that could integrate with my school's terrible email server, which saved me from using their broken web client. Postbox has a clean (but not exactly minimal) interface, a nice way of displaying conversations, great attachment handling, is super stable, and has been around a long time.