Microsoft's Office Labs puts out projects that (hopefully) improve Office.  One such early project was "Search Commands" which helps users find Office commands that the Ribbon wants to hide from them. Here's another one, which purports to be a "pause button" for email, but actually offers a lot more than that.

It's called Email Prioritizer, and as Microsoft says:

Our latest prototype, Email Prioritizer, includes these features:

• A "Do Not Disturb" button that stops incoming mail delivery so you can work without interruptions.
  

• Email priorities are assigned to incoming mail so you can focus on the most important mail first. With a “0-3 stars” ranking system, you can focus on email messages that are most important to you. These priorities are based on algorithms from Microsoft Research.

Now, the "Do Not Disturb" button: that would go over like a lead balloon in most offices (except those with things like email-free Fridays). However, the prioritization of emails, now that we find interesting.


You obviously have to "train" the software to know what kind of priority to assign to each incoming email, but once done, it's pretty useful.

Of course, the problem with this: you need to be using Office 2007. Heavy sigh: it figures. Still, this could turn out to be a rather interesting add-in, if you're OK with trying pre-release software.