Apex domains cannot have CNAME records.
Question and response
Question
dig xsend3.email. NS
Answer
xsend3.email. 5 NS ns-988.awsdns-59.net.
xsend3.email. 5 NS ns-1528.awsdns-63.org.
xsend3.email. 5 NS ns-1977.awsdns-55.co.uk.
xsend3.email. 5 NS ns-46.awsdns-05.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0