mail.linkenglishschool.com has no CNAME records.
Question and response
Question
dig mail.linkenglishschool.com. NS
Answer
The response has no answer records.
Authority
linkenglishschool.com. 2376 SOA ns35.domaincontrol.com. dns.jomax.net. 2023062100 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0