smtp.nea.net.pl has no MX records.
Question and response
Question
dig smtp.nea.net.pl. MX
Answer
The response has no answer records.
Authority
nea.net.pl. 3600 SOA dns1.bestmedia.com.pl. admin.bestmedia.com.pl. 2020072400 10800 1800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0