mx2.RBC.RU has no NS records.
NS records for this zone are defined at RBC.RU.
NS records for this zone are defined at RBC.RU.
Question and response
Question
dig mx2.RBC.RU. NS
Answer
The response has no answer records.
Authority
RBC.RU. 60 SOA ns.RBC.RU. noc.RBC.RU. 2026022503 3600 1200 604800 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0