The Root Zone Database represents the delegation details of top-level domains, including gTLDs such as “.COM, and country-code TLDs such as “.UK. As the manager of the DNS root zone, IANA is responsible for coordinating these delegations...

MX Lookup will list MX records for a domain in priority order. The MX lookup is done against the domain's authoritative name server. Diagnostics will connect to the mail server, verify reverse DNS records, Open Relay check, blacklist check ...