Apex domains cannot have CNAME records.
Question and response
Question
dig mtaspg.email. NS
Answer
mtaspg.email. 5 NS ns-1759.awsdns-27.co.uk.
mtaspg.email. 5 NS ns-837.awsdns-40.net.
mtaspg.email. 5 NS ns-239.awsdns-29.com.
mtaspg.email. 5 NS ns-1238.awsdns-26.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0