If you have multiple items to delete in the Deleted Items folder, use one of the three methods listed below to select multiple items all at once.
Selecting Consecutive Items
Select the first item in the list, hold down the Shift key on the keyboard and then select the last item in the list. This will select all items in-between. Clicking 
on the toolbar will permanently delete all the selected items.
Selecting Nonconsecutive Items
To select items in nonconsecutive order, select the first item, hold down the Ctrl key on the keyboard and then select all other items. Clicking on the toolbar will permanently delete all the selected items.
Selecting All Items
To permanently delete all items in the Deleted Items folder, select the Tools menu and select Empty "Deleted Items" Folder.