mail.KES.RU has no CNAME records.
Question and response
Question
dig mail.KES.RU. NS
Answer
The response has no answer records.
Authority
KES.RU. 4071 SOA ns.KES.RU. geo.ns.KES.RU. 2023081202 28880 7200 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0