To check the mail quota usage for a particular folder in your mailbox, perform the following steps:
Select the folder to check the quota usage and click the folder properties icon from the mail toolbar.
Alternatively, right-click the folder to check the quota usage and select Folder Properties from the drop-down list of options.
The Folder Properties dialog box appears and displays the folder properties:
Folder Name: Name of the folder selected.
Storage Use: Amount of disk space in the folder.
A large shaded portion in the bar graph shows the total amount of quota used by all the folders. The overall mail quota.
A smaller shaded portion in the bar graph indicates the amount of disk space in the selected folder.
Messages Stored: Number of messages in the folder.
A large shaded portion in the bar graph shows the total number of messages in all folders.
A smaller shaded portion in the bar graph indicates the number of messages in the selected folder.
Click OK.