_spf.4web.pl has no MX records.
Question and response
Question
dig _spf.4web.pl. MX
Answer
The response has no answer records.
Authority
_spf.4web.pl. 86400 SOA ns1.4web.pl. dnsadmin.4web.pl. 6 7200 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0