mail.runnet.ru has no NS records.
NS records for this zone are defined at runnet.ru.
NS records for this zone are defined at runnet.ru.
Question and response
Question
dig mail.runnet.ru. NS
Answer
The response has no answer records.
Authority
runnet.ru. 600 SOA ns.runnet.ru. hostmaster.runnet.ru. 2025121500 10800 1800 1209600 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0