mail.pk.ru has no CNAME records.
Question and response
Question
dig mail.pk.ru. NS
Answer
The response has no answer records.
Authority
pk.ru. 3261 SOA ns.vmts.ru. noc.vmts.ru. 2023040403 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0