Like ttech says, the InMail utility is a pain in the tookus. You might get lucky, manually logging into mailboxes to see who's the culprit. You can set a max number of messages per mailbox with a max number of days until purge to try to prevent this from happening in the future (at least you can in the SL and SV). They might get a bit more time out of it, but they're running on borrowed time with the age of the Aspire.