ppnt01.packplast.com.pl has no MX records.
Question and response
Question
dig ppnt01.packplast.com.pl. MX
Answer
The response has no answer records.
Authority
com.pl. 3600 SOA a-dns.pl. dnsmaster.nask.pl. 1771766703 900 300 2592000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0