_spf.amu.edu.pl has no MX records.
Question and response
Question
dig _spf.amu.edu.pl. MX
Answer
The response has no answer records.
Authority
amu.edu.pl. 3600 SOA dns.amu.edu.pl. dnsadm.amu.edu.pl. 2026012027 43200 3600 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0