mx10.orlen.pl has no CNAME records.
Question and response
Question
dig mx10.orlen.pl. NS
Answer
The response has no answer records.
Authority
orlen.pl. 761 SOA dns1.orlen.pl. help.orlen.pl. 2019071919 86400 14400 2592000 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0