smtp.poczta.ostnet.pl has no MX records.
Question and response
Question
dig smtp.poczta.ostnet.pl. MX
Answer
The response has no answer records.
Authority
poczta.ostnet.pl. 60 SOA dnsmaster.ostnet.pl. mgradzki.ost.net.pl. 2026021201 180 180 86244 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0