mx.okinform.ru has no CNAME records.
Question and response
Question
dig mx.okinform.ru. NS
Answer
The response has no answer records.
Authority
ru. 3600 SOA a.dns.ripn.net. hostmaster.ripn.net. 4067929 86400 14400 2592000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0