Tenant personalized nameservers, if designed with the tenant operator, will be accessible to all zones belonging to any account that is an element of the tenant. Through API only. Quad9 provides very able performance, way too, with DNSPerf currently ranking the service seventh out of 12 Public DNS resolvers https://mautic-installation22221.bleepblogs.com/27164970/5-tips-about-anti-spam-filter-you-can-use-today