we have multiple remote sites that use OpenDNS for direct internet access. The remote sites have no server infrastructure to run DNS. I have a headquarters with a handful of servers i need the clients to connect to. conditional forwarder would be a perfect scenario here on the MX (i just added via wishlist). not sure if anyone is doing something similar with a different solution.
I would add the DNS from HQ as secondary DNS. Then make sure the machines are joined to the domain at HQ. I am assuming you have internal domains that you are trying to resolve at the remote sites with this fix.