mail37.RT.RU has no CNAME records.
Question and response
Question
dig mail37.RT.RU. NS
Answer
The response has no answer records.
Authority
rt.ru. 34 SOA ns1.rostelecom.ru. hostmaster.rt.ru. 2026022502 600 7200 1209600 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0