10mx.zoner.com has no CNAME records.
Question and response
Question
dig 10mx.zoner.com. NS
Answer
The response has no answer records.
Authority
zoner.com. 2479 SOA ns1.regzone.cz. administrator.czechia.cz. 2026022508 10800 1800 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0