mx4.v101.vh.net.pl has no CNAME records.
Question and response
Question
dig mx4.v101.vh.net.pl. NS
Answer
The response has no answer records.
Authority
v101.vh.net.pl. 10800 SOA ns1.domenomania.pl. root.v101.vh.net.pl. 2026020900 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0