I know this will sound like an ad, but... If you use Outlook, you need Lookout, a plugin for Outlook that indexes your mail store (whether it's local or stored on an Exchange or IMAP server), attachments, your contact list, your calendar and even your filesystem and offers lightning-fast full-text search. If you're still filing email into a zillion different folders, you need to get on with your life, install Lookout, and get your head around a three-folder lifestyle: inbox, trash and "keepers."
Oh, and in case you're frustrated by the anemic "about us" page, know that Lookout is a product of Eric Hahn and the Inventures Group. Hahn has deep, deep roots in email -- he was VP of Engineering at cc:mail, and went on to found Collabra, which became the core of Netscape's collaboration products.