_spf.true.nl has no MX records.
Question and response
Question
dig _spf.true.nl. MX
Answer
The response has no answer records.
Authority
true.nl. 86400 SOA auth01.dns.trueserver.nl. hostmaster.true.nl. 2024052756 86400 3600 604800 86400
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0