This page provides background information on open relaying is and why it is a problem. Use a machine on a network - other than the University of Maryland . You can receive email, but you can no longer send email to non-University of Maryland email addresses. University faculty go on sabbatical all over the world.
University students go home for holidays.
Both groups often wish to avoid the time quotas that heavy use of the University dialups has made necessary. They all want to send and receive mail using their University email accounts. The most reliable method for doing so is for them to use the mail servers dedicated to those email accounts. The issue of relaying creating problems has been around for a long time. ISP 2's users complain, either to ISP 1 directly or through their own ISP 2.