mail.mail.cal.pl has no CNAME records.
Question and response
Question
dig mail.mail.cal.pl. NS
Answer
The response has no answer records.
Authority
mail.cal.pl. 2 SOA ns1.cal.pl. hostmaster.mail.cal.pl. 2023102400 3600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0