woah
AtMail Open: Redefining Open Source Webmail
No AV, AS, Ajax Calendar, for Open Source version.
Also, I don't see CalDav/WebDav anywhere. Those are the future of messaging. Hope they can include it.
Seems pretty cool tho. I'm not gonna bash

Anything that provides users an OPTION (even better if it's a Open Source Option), is a great thing in my book.
Props to the atmail.org team!