mail.netsolution.com.pl has no CNAME records.
Question and response
Question
dig mail.netsolution.com.pl. NS
Answer
The response has no answer records.
Authority
netsolution.com.pl. 3368 SOA ns1.netserwer24.pl. hostmaster.netsolution.com.pl. 2025020601 3600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0