I've been looking at the SmartZone WiFi calling documentation and understand that the premise is as long as the ePDG hostname/IP is provided, SmartZone will collect more detailed statistics as well as provide better prioritization for wifi calls.
Is there official guidance on the ePDG hosts to configure for popular carriers (at least in the USA, like T-Mobile, Sprint, Verizon, and AT&T)? The documentation provides one domain name that seems to correspond to AT&T.