I'm getting the same redirect at the wbcp. I'm going on vacation for two weeks and my mailbox is already full. Help!

OK, I'll try to help you. But don't forget to attach your mailbox number and password for it when you have such a request.
but you can also do it on your own
You should login to your cpanel, select MAIL- ADD/REMOVE ACCOUNTS-(THE REQUIRED ACCOUNT) AND THERE PLEASE PRESS THE BUTTON "CLEAR MAILBOX "
That's all