As a result of a long-running cron job, I have over 1,000 messages in my user's mailbox. What's the easiest way to delete them?
It depends if you have ftp access. If so, just use Nautilus to do a good deal more than any other ftp client. I also use it and Bluefish to edit pages on my websites.
There should be a Mail folder where you can view and delete any and all files.
I find it so much easier than File Manager in cPanel.