You apparently don't actually use email. Why not just remove your email client? You could use the QuickFilter to show only unread messages. Then ctrl+a will select all your displayed unread messages. The delete key will dispatch them - but don't press this just yet. Both selection and deletion actions may take some time with such a huge backlog. Delete will move them to trash. If you do this, you may also want, after the deletion process has finished, to right-click Trash and choose the option to empty it. Alternatively, if you hold down shift whilst pressing the del key, they should instead be deleted permanently, and probably more quickly as there is no transfer to another folder. How do you know there is nothing of value in there?