Clearing the Trash on Logout
The default action when deleting a message via the webmail interface is to move the message into the Trash folder. Messages must be deleted from the Trash folder before space is freed up from your mailbox account.
The following steps below will explain how to configure your Trash folder to be emptied automatically upon logging out of webmail.
Step by Step
Click the "Settings" button in the main navigation:
Click on "Server Settings" from the list of sections:
Check the "Clear Trash on logout" checkbox and then click the "Save" button: