RCS messaging has been a significant improvement over SMS/MMS. However, when sending a message from an iPhone over Wi-Fi on a DTTS-enabled policy, you will need to turn on a new official Enabler labeled “RCS Messaging” like this:
Enabler required
Allow-list required
The following domain (with subdomains) must be allowed:
rcs.telephony.goog
In your logs or SIEM you will see queries similar to these:
ca.sasktel.rcs.telephony.googfp.ca.rogers.rcs.telephony.googfp-ca-bell.rcs.telephony.googca.telus.rcs.telephony.goog[carrierX].rcs.telephony.goog
Across our client base we have seen over 130 unique subdomain queries to rcs.telephony.goog.
The Enabler contains the following IP address destinations for TCP ports 443 and 5223:
216.239.36.131
216.239.36.132
216.239.36.133
216.239.36.134
Once the Enabler is applied and the above domain is allow-listed (with subdomains) on each relevant policies, you will be able to send RCS messages over Wi-Fi from iOS to Android devices.