Apex domains cannot have CNAME records.
Question and response
Question
dig perfit-mail.net. NS
Answer
perfit-mail.net. 5 NS ns-522.awsdns-01.net.
perfit-mail.net. 5 NS ns-429.awsdns-53.com.
perfit-mail.net. 5 NS ns-2042.awsdns-63.co.uk.
perfit-mail.net. 5 NS ns-1136.awsdns-14.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0