Apex domains cannot have CNAME records.
Question and response
Question
dig inboxskills.net. NS
Answer
inboxskills.net. 5 NS ns-1379.awsdns-44.org.
inboxskills.net. 5 NS ns-2008.awsdns-59.co.uk.
inboxskills.net. 5 NS ns-117.awsdns-14.com.
inboxskills.net. 5 NS ns-557.awsdns-05.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0