I have seen some elaborate email folder structures in my time. Some I would even describe as works of art. So much so that they could probably fetch a decent price at a Christie's auction. These elaborate folder structures, beautiful as they may be, are also, at the risk of offending, a colossal waste of time.
With the full-text searching capabilities of today's modern email platforms, email folders make very little sense. If you need to find an email, just search for it like you would search for a web page on Google. Modern email platforms even have their own search syntax to help you find the appropriate email.
In my "How To Work Efficiently" seminar, I suggest having just one folder named "Processed." (That's right, ONE folder.) Every email that is still pending action remains in the inbox, every other email goes in the "Processed' folder. Part two of this "How To Handle Email Efficiently" post will be a lot easier to implement if you limit the number of folders you use to somewhere between one and five.
If you are still reluctant to move away from your email folder work of art, consider how much time you spend just looking for the right folder to drop emails into. If you summed up all this email folder search time, I guarantee you would be surprised by just how much time is being wasted looking for appropriate folders.
Now, I can hear the masses muttering "I can't move to a single folder, how would I find an email sent from John Doe last month if I don't have a folder for John Doe?" My answer "from:(john doe) received:last month" in the search box (Microsoft Outlook 2007 - Similar syntax exists for almost every modern email platform).