Binary package of Ximian (Novell) Evolution (X11 version) for Mac OS X, with native Mac OS X installer.
I hate to downrate this simply because it's older, but sf won't let me post a review without a rating, and frankly, this is probably of limited use to current Mac users. The package is PPC-only, so won't work with Snow Leopard and higher. I have no reason to think that it isn't fantastic on earlier versions of Mac OS, but no particular reason to think it doesn't brick systems, either. Best of luck if you have an older or PPC system.