Xiant:

Xiant is dedicated to producing tools that make your time at the computer as productive as possible. Though we are launching our first products, our tech roots are second to none. Xiant Filer was created by technology innovator/Microsoft co-founder Paul G. Allen and engineers at Xiant, whose challenge was to ease management of overflowing Microsoft Office Outlook inboxes. Xiant has even more tools under development to help you be productive, organized, and connected with your stuff.

Xiant Filer

E-mail is a crucial productivity tool. As our dependency on e-mail grows and its volume increases, our mailboxes become increasingly difficult to manage. Quickly finding messages in a bloated inbox—from various senders and in multiple conversation threads—can prove difficult, if not impossible. And while there are many solutions out there to help manage and organize e-mail, each one typically requires an investment in time and effort that could be better spent on more important tasks.
If you use Microsoft Office Outlook as your e-mail application, the beta release of the Xiant Filer add-in can instantly help you more efficiently manage your e-mail.

So, if you need/want such a thing, here it is.

But please, dear God. Don't use this. In fact, don't use Outlook. I'm not saying Paul Allen is a bit out of touch, but releasing a utility for yesterday's email application these days is somewhat, well, out of touch. I realize a lot of people still use Outlook. But if this guy had his head in the right place, he'd be helping people remove the single-PC lock of such legacy applications. Your data should be available everywhere. Sorting it in a single place doesn't really obviate the underlying inefficiency of using such an application.