_spf.ia.surf.nl has no MX records.
Question and response
Question
dig _spf.ia.surf.nl. MX
Answer
The response has no answer records.
Authority
ia.surf.nl. 3600 SOA ns1.surfnet.nl. hostmaster.surfnet.nl. 2603061648 7200 600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0