|Can't they support it another way?|
Ports normally refer to tcp/ip port numbers. An IP address along with a port number is normally required. Many things could block ports (with good reason), firewalls, router's, modems maybe and ISP's may block ports.
What port number do you need open?
Ask them for a different way to register, even stupid MS can do that!
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10