name server is considered authoritative for a domain name when it has the best source of information that can be found inside a given zone. Authoritative servers usually include a SOA (Start of Authority) record in their zone file for a domain name. For instance, if a zone file says: "@ IN SOA dns1.namesecure.com", this means that dns1.namesecure.com is considered authoritative for the domain. Only one SOA record can be contained in a zone file.
For DNS, describes a DNS server hosting a zone, or a zone containing a name or record. When a DNS server is configured to host a zone, it is said to be authoritative for names that do exist or could exist within that zone. A DNS server is allowed to respond authoritatively to queries for domain names for which it is authoritative. A zone is said to be authoritative for a name if the name exists or could exist within a zone, and it is said to be authoritiative for a record if the owner name of the record exists or could exist within a zone. See also: DNS Server; domain name; Domain Name System (DNS); name server (NS) resource record; start-of-authority (SOA) resource record; zone