Ultra lightweight email client

I'm looking for a clean lightweight email client. I've found Mailpeek but it doesn't support SSL. Popcorn looked promising but was never finished and is no longer developed.

Does anyone know of a good lightweight mail client? I don't want a lot of features; I just need it to support SSL, be able to receive mail, be able to send mail, and be able to minimize to tray (with new mail notification).

Open source would be best but freeware is also acceptable.