I have a complex Tailscale-based network setup that includes blocking all Google hostnames. Unfortunately RCS on iOS doesn’t work when sending photos.

I’d like to set up a Tailscale App Connector using hostnames, but if they’re using IP addresses I can work with those as well (subnet routing).

I’ve scoured AT&T’s website and App Privacy Report on iOS (which doesn’t show DNS names for Messages, Phone apps) but I do know they switched to Google as their RCS provider at one point.

Update: Resolved by allowlisting rcs-copper-us.googleapis.com specifically, but I also added all of telephony.goog to unblock rcs.telephony.goog. A simple tcpdump got me the DNS requests for those domains.