There are times when your office mailbox size needs to be less than specified limit as per company’s policy and all employees have to adhere to that. So if you want to determine the folder size of your mailbox or inbox then you can do the following.
Right click the folder for which the size the needs to be determined.
For example in the above snapshot, if you want to know the folder size inbox then select inbox on right click the folder and select properties from the menu.
The above folder property dialog box would be displayed and on clicking Folder Size button the following dialog box appears displaying the folder(s) size.
This way you can make sure and check regularly that you do not exceed the specified mailbox size.