_netrange2.zenbox.pl has no MX records.
Question and response
Question
dig _netrange2.zenbox.pl. MX
Answer
The response has no answer records.
Authority
zenbox.pl. 600 SOA ns1.zenbox.pl. hostmaster.zenbox.pl. 2026012800 600 3600 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0