That is not the issue, the issue is that when the WHS Server tries to update the *.homeserver.com domain it uses the internal IP of the server instead of the external IP.
Here is a NSLOOKUP
Server: 216.216.33.3
Address: 216.216.33.3#53
Non-authoritative answer:
Name: the******.homeserver.com
Address: 192.168.4.4