fixed.kpn.net has no MX records.
Question and response
Question
dig fixed.kpn.net. MX
Answer
The response has no answer records.
Authority
fixed.kpn.net. 3600 SOA ns7.kpn.net. zonemaster.kpn.com. 2020081801 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0