mx.corp.nic.ru has no MX records.
Question and response
Question
dig mx.corp.nic.ru. MX
Answer
The response has no answer records.
Authority
corp.nic.ru. 600 SOA pdns.infra.nic.ru. noc-dns.nic.ru. 2023101302 14400 3600 2592000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0