Getting Overwhelmed with eMail

:thanks:I am an organizational consultant and I have an organizational dilema I feel I should be able to solve...but I don't know enough about the mechanics of Gmail to build a solution. It was hard enough just to break down the chaos into a question.
How do I keep the disparate email I get from 4 big client companies (over 200 staff each) filed discretely and retrievably without some Herculean effort on my part or my interns's part? We are talking about no less than 800 missives a fortnight that will have to be read and commented upon in a timely manner, i.e. in two weeks.
I already know more than I thought I coud about folders, message filters, and the egometric performance hit an application tales from a kludge solution. I do not see this in anyway becoming a production vehicle anywhere, hence the klude in MS Basic.
Can anyone point me to a better approach?
Rick Rooney
...and thanks for reading this far:thanks: