Apex domains cannot have CNAME records.
Question and response
Question
dig medm.email. NS
Answer
medm.email. 1 NS ns-1575.awsdns-04.co.uk.
medm.email. 1 NS ns-1207.awsdns-22.org.
medm.email. 1 NS ns-471.awsdns-58.com.
medm.email. 1 NS ns-960.awsdns-56.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0