I don't know why this doesn't seem possible. In fact, I've never seen an email client, even the most base, where you couldn't do a 'select all' on a folder, and then delete.
Am I missing something here? Is there no way to do a select all, or a select all on a search, and then do something with the contents?
Essentially, I want to delete all messages from a single mailbox that are before a certain date. Why is this hard?
(note, that I'm just aping my employee's comments)