How do I delete 150,000 old emails by date?

Diartemis wrote:

Over the years, have accumulated over 100,000 old emails. How can I quickly delete the ones that are over two years old?

Shift key will help you "select all" between the two references points— then use the Command Delete key...(?)

(much like the Command key allows you to select more than one email)

Mail User Guide for Mac

In addition, if the mail is scattered around several mailboxes, you can create a Rule to delete all mail older than some fixed date.