Apex domains cannot have CNAME records.
Question and response
Question
dig mailchannels.net. NS
Answer
mailchannels.net. 5 NS ns-988.awsdns-59.net.
mailchannels.net. 5 NS ns-242.awsdns-30.com.
mailchannels.net. 5 NS ns-1837.awsdns-37.co.uk.
mailchannels.net. 5 NS ns-1131.awsdns-13.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0