_spf.vdx.nl has no MX records.
Question and response
Question
dig _spf.vdx.nl. MX
Answer
The response has no answer records.
Authority
vdx.nl. 86400 SOA ns1.dn-s.nl. hostmaster.vdx.nl. 2021010100 600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0