mx.sferamail.pro has no NS records.
NS records for this zone are defined at sferamail.pro.
NS records for this zone are defined at sferamail.pro.
Question and response
Question
dig mx.sferamail.pro. NS
Answer
The response has no answer records.
Authority
sferamail.pro. 86400 SOA dns.sfera.net. hostmaster.server.sfera.net. 2023031653 86400 14400 3600000 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0