_spf.cal.pl has no MX records.
Question and response
Question
dig _spf.cal.pl. MX
Answer
The response has no answer records.
Authority
cal.pl. 3600 SOA ns1.cal.pl. hostmaster.cal.pl. 2026021405 3600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0