mx.utels.ua has no NS records.
NS records for this zone are defined at utels.ua.
NS records for this zone are defined at utels.ua.
Question and response
Question
dig mx.utels.ua. NS
Answer
The response has no answer records.
Authority
utels.ua. 1800 SOA mary.ns.cloudflare.com. dns.cloudflare.com. 2399267929 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0