MailItem.Delete Method (Outlook)
Removes the item from the folder that contains the item.
The Delete method deletes a single item in a collection. To delete all items in the Items collection of a folder, you must delete each item starting with the last item in the folder. For example, in the items collection of a folder, AllItems, if there are n number of items in the folder, start deleting the item at AllItems.Item(n), decrementing the index each time until you delete AllItems.Item(1).
The Delete method moves the item from the containing folder to the Deleted Items folder. If the containing folder is the Deleted Items folder, the Delete method removes the item permanently.