internet.jettel.pl has no MX records.
Question and response
Question
dig internet.jettel.pl. MX
Answer
The response has no answer records.
Authority
internet.jettel.pl. 3600 SOA dns1.jettel.pl. biuro.jettel.pl. 2018110601 28800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0