mail.restream.rt.ru has no CNAME records.
Question and response
Question
dig mail.restream.rt.ru. NS
Answer
The response has no answer records.
Authority
restream.rt.ru. 600 SOA ns1.restream.rt.ru. postmaster.restream.rt.ru. 2025102300 28800 7200 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0