Did you know that the Modern UI Mail application that comes with Windows 8 allows you to pin mail accounts to the Start Screen?
Pin Individual Email Account To The Start Screen in Windows 8
Press the Windows key to switch over to the Start Screen and launch the Mail app.
In the bottom left hand corner you will see a list of email accounts that you have set up to use with the app.
Simply right click on the one you wish to pin to the Start Menu, and choose Pin to Start from the app bar that appears on the bottom of the screen.
You will then be given a chance to change the text that will appear on the tile. Once you are satisfied, go ahead and click Pin to Start.
The benefit of doing this is that each mailbox then has its own tile, with its own notifications.