mgt.OCS.RU has no MX records.
Question and response
Question
dig mgt.OCS.RU. MX
Answer
The response has no answer records.
Authority
OCS.RU. 3600 SOA ns.OCS.RU. admin.OCS.RU. 2026030501 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0