Good email search engine

[gateway]

(sorry for a little bit of a tangent, but)
Kind of a cool project by MIT which reinforces the inexact and confusing world of digital ID (and thus the inherent problems associated with email searching):
http://personas.media.mit.edu/ *

"In a world where fortunes are sought through data-mining vast information repositories, the computer is our indispensable but far from infallible assistant. Personas demonstrates the computer's uncanny insights and its inadvertent errors, such as the mischaracterizations caused by the inability to separate data from multiple owners of the same name."

*I've heard Personas has trouble running in Firefox with tabs open in case you try it (which you should be cause it's fun and pretty, although if there isn't enough of a footprint, it won't find anything)