mms.metroport.pl has no MX records.
Question and response
Question
dig mms.metroport.pl. MX
Answer
The response has no answer records.
Authority
metroport.pl. 3600 SOA metroport.pl. dns.insite.pl. 2014041895 3600 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0