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. 1720 SOA ns1.is74.ru. hostmaster.is74.ru. 2018362258 1800 600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0