In connection with caching DNS records on servers, it is necessary to inform clients whether the response that is sent to them comes from the caching server or whether the response comes directly from the authoritative DNS server. To do this, use the flag in the DNS message header. The answer that the caching DNS server (that mediates the query) accepted from the relevant authoritative server is also marked as non-authoritative. Thus, only the one we obtained directly without any intermediary is marked as authoritative.
At this point, it should be emphasized again that the authoritative response flag does not mean that the domain is actually delegated to this DNS server. The crucial part is that the administrator has added this domain to the server and created a zone for it. The servers do not verify in any way whether the domain is really delegated to them. A problem, such as that described in the DNS Protocol Recursive and Non-Recursive Queries article, may arise.