_spfout.mf.surf.net has no MX records.
Question and response
Question
dig _spfout.mf.surf.net. MX
Answer
The response has no answer records.
Authority
surf.net. 3600 SOA ns1.surfnet.nl. dns-beheer.surf.nl. 2026030615 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0