mail.vs77100.com has no CNAME records.
Question and response
Question
dig mail.vs77100.com. NS
Answer
The response has no answer records.
Authority
vs77100.com. 6152 SOA ns1.onlydomains.com. root.onlydomains.com. 2022090301 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0