For the storage conscious:

Have you have ever wanted to find out how much storage space your Outlook mailbox has taken up on the corresponding email server? If so, there is a simple way to figure out the quantity in Outlook 2007. 

Here is how:

1. In Outlook, Click Tools.
2. Click Mailbox Cleanup -> A dialog box will appear that gives other options like finding files over a specific size, Deleted Items size, and more.
3. Click View Mailbox Size -> You can view the details of local & server storage used.
4. On the Server Data tab, you can view the space left on the server. [If you have sub-folders, the space total will be cumulative]