Apex domains cannot have CNAME records.
Question and response
Question
dig mailpoint.cz. NS
Answer
mailpoint.cz. 1 NS sns.cybersales.cz.
mailpoint.cz. 1 NS ns.cybersales.cz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0