mx.tviinet.ru has no NS records.
NS records for this zone are defined at tviinet.ru.
NS records for this zone are defined at tviinet.ru.
Question and response
Question
dig mx.tviinet.ru. NS
Answer
The response has no answer records.
Authority
tviinet.ru. 3600 SOA ns1.tviinet.ru. root.tviinet.ru. 2025051335 3600 600 360000 3600
Additional
. 0 OPT [{Extended_DNS_Error: PROHIBITED}] ; payload 1232, xrcode 0, version 0, flags 0