I agree with a little of both....If the porpose of ISOMEDIAs scans was to find SMTP relays and block them, I'm all for it. There are a ton servers out there with SMTP open, that allow relaying (spoofing e-mails, spam, ect..). They are probable trying to help prevent spam which I am all for. Sure its irritating to be scanned, but if you run a tight ship, you have nothing to worry about. Its called layered security. Let them scan the crap out of your external router and firewall depending on policies, and log at the internal router. If a good policy is in place, little should be getting past the filtering of your external router, and nothing past the firewall. Do you have the right to scan them back and block them, sure, and by all means block them...