mail.INFRA-BRV.RU has no NS records.
NS records for this zone are defined at INFRA-BRV.RU.
NS records for this zone are defined at INFRA-BRV.RU.
Question and response
Question
dig mail.INFRA-BRV.RU. NS
Answer
The response has no answer records.
Authority
INFRA-BRV.RU. 1800 SOA kip.ns.cloudflare.com. dns.cloudflare.com. 2399637269 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0