This information applies to SmarterMail and the SmarterMail web-based email interface.
When you delete a message from anywhere other than the Deleted Items folder, it will first move the message to the Deleted Items folder. The Deleted Items folder is a special folder that acts like the Recycle Bin on a Windows/Mac desktop. It's there to prevent you from accidentally deleting an email message and allows you to restore the message(s) if needed.
To permanently delete the message(s) and free up email disk space, select the Deleted Items folder and perform the delete operation again on the messages stored here. This will remove the email from the servers.
You will not be able to undo this operation.