Like others, I wrestle with a large volume of email, especially at work. I've tried a couple of different systems, but this is the best I've found and recommend checking out the video at YouTube:
Inbox Zero (Merlin Mann)
The basic idea is that you process your emails to reduce your inbox to zero. Much less filing of emails and when you do, into just a few categories (in my case: trash, archive, defer, follow up).