Apex domains cannot have CNAME records.
Question and response
Question
dig mxeuc.freshdesk.com. NS
Answer
mxeuc.freshdesk.com. 5 NS ns-1537.awsdns-00.co.uk.
mxeuc.freshdesk.com. 5 NS ns-905.awsdns-49.net.
mxeuc.freshdesk.com. 5 NS ns-199.awsdns-24.com.
mxeuc.freshdesk.com. 5 NS ns-1496.awsdns-59.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0