mail.oborona.net has no MX records.
Question and response
Question
dig mail.oborona.net. MX
Answer
The response has no answer records.
Authority
oborona.net. 3600 SOA ns1.oborona.net. admin.oborona.net. 2026010701 86400 86400 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0