mx.mynet.pl has no CNAME records.
Question and response
Question
dig mx.mynet.pl. NS
Answer
The response has no answer records.
Authority
mynet.pl. 3131 SOA ns1.ogicom.pl. admin.ogicom.pl. 2025120409 10800 1800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0