You can delete messages that you don't need anymore to help keep your inbox manageable. Once a message has been permanently deleted, it can never be retrieved.
Select Home > Messages.
There are two ways to delete messages:
Check the box(es) to the left side of the message(s) to be deleted, or
Open the message and click the Delete button.
Click OK when the "Are you sure you want permanently delete this message?"
Click Delete again.