mail3.nport.ru has no NS records.
NS records for this zone are defined at nport.ru.
NS records for this zone are defined at nport.ru.
Question and response
Question
dig mail3.nport.ru. NS
Answer
The response has no answer records.
Authority
nport.ru. 3600 SOA ns1.snparking.ru. hostmaster.nport.ru. 2020011684 10800 3600 3600000 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0