I second using GTD. I have the book in print, audio, and Kindle and often give it as a gift.
Heather, here are a couple of quick tips to purge large amounts of Email quickly:
1. Set your inbox to be arranged by Type. You can then go through an eliminate all the Out of Office messages, obslete meeting requests, meeting cancellation notices, etc.
2. Set your inbox to be arranged by From. Then you can eliminate all of the newsletters, conference announcements, training course marketing, agency spam, and so forth in one fell swoop. Then you can go through and eliminate unnecessary personal Emails from friends and/or spouses.
Just these two steps should reduce your inbox by 30-40 percent, guaranteed or your money back.
Then you go through and archive all the old and one-off conversations that are official government business. That should get your inbox 50 percent smaller.
Then go to Amazon and order Getting Things Done.
Best of luck,