@Compass I kind of get that... unfortunately I just don't have the time to read all the answers (not even speaking of all the comments) and that makes me a little sad...

My university's IS department has dropped to a new low. We have just been told that "To help protect the integrity of the university’s IT systems and services, all email messages received from external email addresses currently contain a tag [Spam?] within the subject line."

Yup, instead of leasing expensive spam filters, mark it all as possible spam and let the user do it. That'll work. Do that.