To check the mail quota usage for a particular folder in your mailbox, perform the following steps:
In two-pane layout, select the folder to check the quota usage and click Folder Properties from the mail toolbar.
In three-pane layout, select the folder to check the quota usage and select Folder Properties or Sharing from the Folder Actions drop-down list above the folder list and click Folder Properties.
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: The folder name for which the quota information is being displayed.
Storage Use: The storage used appears in the form of a bar chart:
Total storage used: A large shaded portion in the bar graph shows the total amount of quota used by all the folders. The overall mail quota.
Storage used by this folder: A smaller shaded portion in the bar graph indicates the amount of disk space in the selected folder.
Messages Stored: A status bar that shows the number of messages stored in your mailbox.
Total number of messages: A large shaded portion in the bar graph shows the total number of Email messages in all folders.
Number of messages in this folder: A smaller shaded portion in the bar graph indicates the number of Email messages in the selected folder.
Click OK.