Enabling the Reservation Mode setting for your organization will prevent tenants from adding invitees to their room reservations. In this workflow, tenants use Robin to book a room and then can invite their guests through their normal calendars. This will reduce the number of off-domain calendar invites sent throughout the day to mitigate rate limit errors.
As a Robin Admin, navigate to Manage > Organization > scroll down to Event Customizations. From here, toggle Enabled next to Reservation Mode.