n01getsout

Evolution is an office productivity pack, including an email client, an address book, a calendar (that supports the open iCal standard), a to-do list, and Palm Pilot support. While it is mostly developed by Novell, it remains open source. Evolution supports Microsoft Exchange servers and Groupwise. They are working to bring more integration with the Gnome desktop.

Or if you only need an email client, try Claws Mail.