"...Freeware Microsoft Outlook plug-in Xobni (that's inbox backwards) adds a handful of killer features to its new Outlook sidebar. Among those features: Email analytics, extraordinarily useful contact cards, fast search, threaded (Gmail-like) conversations, and more. The video above gives an excellent overview, so give it a look. Seeing as Xobni has successfully made Outlook appear exciting (which is no easy feat), this freeware, Windows-only plug-in looks like a winner. Currently Xobni is in a closed beta..."
This isn't directly related to Windows Mobile, but since most people using a Windows Mobile device are also using some version of Outlook, I thought this product would be of interest to you. It's still in a closed beta (I signed up to be notified when it's not), but you can
check out the Xobni site for more details (and let them know what email client you're using if it's not Outlook).