On the other hand, if something like "[EMAIL PROTECTED]" would be sufficient for all my mail relays, and those of subdomains under concordia.ca, that would be fine, except it's no different than the scenario I described in the first message I wrote in this thread.
How about the relay must be an MX for a subscribed address? You'd need something that collected MX's periodically for subscribers.
The more fundamental problem is to prove to the DNSBL that the relay has a live, active admin who pays attention to the announcements, not one who set up the box and left the company a month ago.
