mail.getresponse.pl has no CNAME records.
Question and response
Question
dig mail.getresponse.pl. NS
Answer
The response has no answer records.
Authority
getresponse.pl. 81 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2020010173 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0