sender78.mlgnr.com has no MX records.
Question and response
Question
dig sender78.mlgnr.com. MX
Answer
The response has no answer records.
Authority
mlgnr.com. 300 SOA ns3-l2.nic.ru. admin.mlgnr.com. 2020073310 10800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0