sp.mynet.com.pl has no CNAME records.
Question and response
Question
dig sp.mynet.com.pl. NS
Answer
The response has no answer records.
Authority
mynet.com.pl. 177 SOA ns1.mynet.com.pl. dns.mynet.com.pl. 2024102902 86400 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0