mx.siberia.net has no NS records.
NS records for this zone are defined at siberia.net.
NS records for this zone are defined at siberia.net.
Question and response
Question
dig mx.siberia.net. NS
Answer
The response has no answer records.
Authority
siberia.net. 300 SOA a.ns.avantel.ru. linux-admins.avantel.ru. 2024112601 10800 3600 604800 10800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0