When I do a test on MXToolbox.com our DAG servers are responding with the internal FQDN of the server that received the request. When I attempt the change the FQDN on the Default Frontend (servername) I get an error that it can not be changed because Exchange Servers are selected. Even if I uncheck Exchange servers I still can not change the FQDN. Having said that I don't really want to uncheck that as I am worried it will break communication between the servers.
How do you get the mailbox/cas DAG to respond with the correct external URL?