mail.mysint.ru has no CNAME records.
Question and response
Question
dig mail.mysint.ru. NS
Answer
The response has no answer records.
Authority
MYSINT.RU. 7113 SOA ns1.reg.RU. hostmaster.ns1.reg.RU. 1769501548 14400 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0