mail.rostelecom-cc.ru has no MX records.
Question and response
Question
dig mail.rostelecom-cc.ru. MX
Answer
The response has no answer records.
Authority
rostelecom-cc.ru. 3600 SOA ns.rostelecom-cc.ru. dns.rostelecom-cc.ru. 2829247454 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0