Apex domains cannot have CNAME records.
Question and response
Question
dig email-messaging.com. NS
Answer
email-messaging.com. 5 NS ns-1783.awsdns-30.co.uk.
email-messaging.com. 5 NS ns-958.awsdns-55.net.
email-messaging.com. 5 NS ns-460.awsdns-57.com.
email-messaging.com. 5 NS ns-1460.awsdns-54.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0