sun2.pwr.wroc.pl has no MX records.
Question and response
Question
dig sun2.pwr.wroc.pl. MX
Answer
The response has no answer records.
Authority
pwr.wroc.pl. 2601 SOA dns.pwr.wroc.pl. dns.pwr.edu.pl. 2026013001 10800 3600 804800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0