www.wcss.pl has no MX records.
Question and response
Question
dig www.wcss.pl. MX
Answer
www.wcss.pl. 5 CNAME portal.wcss.pl.
Authority
wcss.pl. 10800 SOA wask.wask.wroc.pl. admin.wask.wroc.pl. 2026021601 28800 7200 604800 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0