I actually noticed this a couple weeks ago, then forgot about it, but then was reminded of it again today.
Edgewall Software, which makes the excellent Trac issue tracking and Genshi template systems, is working on a new buzzword-compliant web mail server called
Posterity. It's not nearly as sophisticated yet as, say, GMail. But it's still looking pretty good.
The Posterity wiki has a
screenshots page with two screenshots. Of interest is
the second screenshot. Anyone who knows my name or would recognize my e-mail address should understand why it amuses me =D