That was the feature ported from Cyberoam UTM. Very nice one, where client doesn't have to register account with external DNS server if they are happy with .ddns.cyberoam.com FQDN hostname.
Obviously Sophos registered myfirewall.co domain for the same purpose, but it looks like that their DNS servers are accepting registrations but still denying requests.
That was the feature ported from Cyberoam UTM. Very nice one, where client doesn't have to register account with external DNS server if they are happy with .ddns.cyberoam.com FQDN hostname.
Obviously Sophos registered myfirewall.co domain for the same purpose, but it looks like that their DNS servers are accepting registrations but still denying requests.