Apex domains cannot have CNAME records.
Question and response
Question
dig sendsrv.com. NS
Answer
sendsrv.com. 4 NS ns2.nitric.co.za.
sendsrv.com. 4 NS ns3.nitric.co.za.
sendsrv.com. 4 NS ns1.nitric.co.za.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0