15mx.zoner.com has no CNAME records.
Question and response
Question
dig 15mx.zoner.com. NS
Answer
The response has no answer records.
Authority
zoner.com. 3600 SOA ns1.regzone.cz. administrator.czechia.cz. 2026030306 10800 1800 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0