Mailmate has a trial version that works fine for 30 days. I actually did try it, though I ended up going for AirMail instead... and then went back to Mail.app!

Mailmate has a trial version that works fine for 30 days. I actually did try it, though I ended up going for AirMail instead... and then went back to Mail.app! I don't mind paying $20 or more for a great email client - I mind paying that for a shitty email client that fails at even basic stuff like, you know, receiving emails.