Apex domains cannot have CNAME records.
Question and response
Question
dig xsend5.email. NS
Answer
xsend5.email. 5 NS ns-97.awsdns-12.com.
xsend5.email. 5 NS ns-1066.awsdns-05.org.
xsend5.email. 5 NS ns-730.awsdns-27.net.
xsend5.email. 5 NS ns-1816.awsdns-35.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0