Desktop Email Storage, definitely.
I'd like to archive all my emails conveniently in a DB like SQL Server through some guaranteed means (synchronization or queues) . Then view and search them though a pretty UI like OWA or Sharepoint.
I found some interesting bits of code at http://www.blueclaw-db.com/read_email_access_outlook.htm and some serverside Exchange software at http://www.gfi.com/mailarchiver/.