FortiAuthenticator Push Notifications

We are setting up two factor authentication using FortiAuthenticator and enable Push Notification. We need to be able to do this on the internal network, guest network and public WAN. Is the best way to do this is to use a FQDN in the public IP/FQDN setting and use DNS routing for each of those to get it to work? Using a public IP address only works on the Public WAN.