Apex domains cannot have CNAME records.
Question and response
Question
dig mailhy.com. NS
Answer
mailhy.com. 5 NS ns1.mailhy.com.
mailhy.com. 5 NS ns2.mailhy.com.
Authority
The response has no authority records.
Additional
ns1.mailhy.com. 5 A 54.251.169.98
ns2.mailhy.com. 5 A 54.183.62.139
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0