mx2.amu.edu.pl has no CNAME records.
Question and response
Question
dig mx2.amu.edu.pl. NS
Answer
The response has no answer records.
Authority
amu.edu.pl. 3202 SOA dns.amu.edu.pl. dnsadm.amu.edu.pl. 2026012027 43200 3600 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0