It isn't clear from that page, but this is actually the latest version of IBM Domino, i.e. the server for Lotus Notes.

IBM still have a large number of corporate customers on Notes/Domino and they've been talking for a while about how to integrate email with other "social" apps for file sharing etc.

This is obviously server-based and so means e-mail without the Notes client, but I believe that it's still built on a Domino server underneath.