For the clients that don't use our Name Servers, but have CNAMES for www and cdn, we could check if those cnames point to our expected domain (currently geo1.presslabs.net).
Not sure it's possible to implement this. It's not just clients that use geo1.presslabs.net but also ezoic users that have a CNAME instead of the PolicyRecord.
For the clients that don't use our Name Servers, but have CNAMES for www and cdn, we could check if those cnames point to our expected domain (currently geo1.presslabs.net).