I'm a bit surprised I haven't seen others post this (though maybe I just missed it). But mail deletion used to be tolerable because you could click anywhere in the mail box to select the bottom most mail.

So, as a work-around for the lack of a "Delete All" function, you could position the delete confirmation's "Yes" button right over the bottom part of the mail area. Then, you could delete one and then alternate between double-clicking on yes (the second click passed through to the mail area and selected the next mail), and clicking delete again.

It was a bit annoying, but workable.

Now, you can't even do that. You have to specifically click each mail and then delete and then "yes" and click only on the actual next mail, including scrolling, etc.

This is a very annoying step backward.