_spf.root.nl has no MX records.
Question and response
Question
dig _spf.root.nl. MX
Answer
The response has no answer records.
Authority
root.nl. 3597 SOA ns.echelon.nl. hostmaster.echelon.nl. 2026010601 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0