Apex domains cannot have CNAME records.
Question and response
Question
dig mailsrv365.net. NS
Answer
mailsrv365.net. 5 NS ns-382.awsdns-47.com.
mailsrv365.net. 5 NS ns-1797.awsdns-32.co.uk.
mailsrv365.net. 5 NS ns-1358.awsdns-41.org.
mailsrv365.net. 5 NS ns-610.awsdns-12.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0