mail.vectranet.pl has no CNAME records.
Question and response
Question
dig mail.vectranet.pl. NS
Answer
The response has no answer records.
Authority
vectranet.pl. 3503 SOA ns.multimedia.pl. ns.multimedia.pl. 2480 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0