I cannot remove unwanted emails.

I Click the FIRST email on the list to delete > scroll to the last on the list, and press Shift key and HOLD > I click on the last one on the list. The list is " shaded ".I click Delete.

The problem is no matter how I try to delete these shaded emails, the program does not respond - no pop ups, nothing. I have always been able to clean up my inbox previously using this method. I currently have almost 18K messages and need to clean it up quickly.