mail2.netart.pl has no MX records.
Question and response
Question
dig mail2.netart.pl. MX
Answer
The response has no answer records.
Authority
netart.pl. 3600 SOA ns1.nazwa.pl. biuro.nazwa.pl. 2008133737 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0