As an admin, the RingCentral app’s domain allow/block list feature will enable you to decide who you want your users to communicate with externally. This is by either allowing or blocking external guest domain and webmail accounts.
To manage your domain/allow block list, navigate to Settings > Administration, and then click Manage at the far right of Domain allow/block list.
The External guest communications toggle lets you decide if you want to continue accepting external guests. Changing this toggle doesn’t affect the allow or block status of domains and webmail accounts already on the list. This means that if you turn this toggle off, guests on the allow list can still communicate with your users.
Note: Admins can change the allow or block status of domains and webmail accounts added on the list even when the External guest communications toggle is turned off.