goodness knows its about time. I get between 50 and 200 emails a day depending on what's going on. It's dropped a lot since instant messaging really took off. I thought I had tried every possible way of working with email and had arrived at the best system for me but then I kind of stumbled on a new approach and it's really working. I think it was using categories to manage my contacts that lead me to accidentally do this to email as well. In 2007 you can have up to 25 unique flag colours and as many categories as you like.
It might just be the way I think about work but I found it much easier to work with email like this because new email arriving goes into the 'none' category and since this is collapsed, I don't worry about it right now.
It is more efficient to do all email to do with the same project rather than context switching on every email and it is really easy to categorise new email from time to time. Just expand the 'none' category and then drag each mail into the right category group. Outlook 2007 automatically applies the category to the mail when you do this.
This has a few advantages for me:
A lot of people use rules and stuff but I stopped doing that a few years ago, letting everything fall into one big folder of email (my inbox). The only other rule I have is to colour mail from my boss pink in the view. Now all my mail is colour coded and grouped by project, it is easier to deal with. I also only ever file email once I've dealt with it so my inbox represents outstanding issues and I can't shuffle a mail into folders and forget about it without dealing with it.
I also use the same categories to colour code my diary so I can see how much time I'm spending on each project. Using consistent colours for meetings and emails by project seems to help my mind process it.
Also if this interests you, you might like the post about how I use OneNote, tasks and my diary to dump stress at the end of a week.