mail.IS74.RU has no CNAME records.
Question and response
Question
dig mail.IS74.RU. NS
Answer
The response has no answer records.
Authority
is74.ru. 1800 SOA ns1.is74.ru. hostmaster.is74.ru. 2018362243 1800 600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0