Zoe provides a web-based search interface and archive for your email.
From my brief look at it, it seems pretty useful.
For security reasons, you don't want to run Zoe without a firewall which will block incoming connections to Zoe on your machine, otherwise anyone would be able to read your emails!
If you currently use Outlook or Outlook Express, you might want to read about Converting Outlook Express Email.
Zoe can be found at: http://guests.evectors.it/zoe/itstories/home.php?data=stories