Open the Deleted Items folder and make sure it does not contain any messages that you need.
Open the Edit menu and select Empty 'Deleted Items' Folder.
Deleted messages are stored in the Deleted Items folder. To save disk space or to really delete a message, you can clean out this folder.
Confirm the deletion by clicking Yes.
The messages are permanently deleted. You can click this folder to confirm it is empty.
Delete Individual Messages
You can also delete individual messages rather than all of the messages in the folder. To do so, open the folder, select the message(s) you want to delete, and click the Delete button. Confirm the deletion by clicking Yes.