d-dns.PL has no MX records.
Question and response
Question
dig d-dns.PL. MX
Answer
The response has no answer records.
Authority
PL. 3600 SOA a-dns.PL. dnsmaster.nask.PL. 1771978204 900 300 2592000 3600
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0