Apex domains cannot have CNAME records.
Question and response
Question
dig email-platform.com. NS
Answer
email-platform.com. 3 NS ns-1542.awsdns-00.co.uk.
email-platform.com. 3 NS ns-958.awsdns-55.net.
email-platform.com. 3 NS ns-143.awsdns-17.com.
email-platform.com. 3 NS ns-1504.awsdns-60.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0