Checking the Size of Your Exchange Mailbox

This is only available for Outlook clients using MAPI

1. Right click on your Exchange Mailbox, which is the very top level, and choose 'Properties for Mailbox ' from the pop-up menu. 
2. On the Mailbox Properties window click the 'Folder Size' button. 
3. On the Folder Size window you will be able to view your total mailbox size in kilobytes (KB). You divide the total number by 1024 to figure out how many MB [megabytes] are being used. This window will also show you the size of each folder individually. If you don't need to know the exact size you can just remove the last 3 digits (e.g. 9000KB = 9MB)