Apex domains cannot have CNAME records.
Question and response
Question
dig mail-messaging.com. NS
Answer
mail-messaging.com. 5 NS ns-1318.awsdns-36.org.
mail-messaging.com. 5 NS ns-1790.awsdns-31.co.uk.
mail-messaging.com. 5 NS ns-235.awsdns-29.com.
mail-messaging.com. 5 NS ns-792.awsdns-35.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0