smtp.omkcmail.ru has no MX records.
Question and response
Question
dig smtp.omkcmail.ru. MX
Answer
The response has no answer records.
Authority
omkcmail.ru. 3600 SOA ns.omkc.ru. noc.omkc.ru. 2025031101 14400 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0