mx5.t21v.ru has no NS records.
NS records for this zone are defined at t21v.ru.
NS records for this zone are defined at t21v.ru.
Question and response
Question
dig mx5.t21v.ru. NS
Answer
The response has no answer records.
Authority
t21v.ru. 100 SOA ns1.t21v.ru. mail.t21v.ru. 2025112601 900 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0