ns3.kpn.net has no MX records.
Question and response
Question
dig ns3.kpn.net. MX
Answer
The response has no answer records.
Authority
kpn.net. 300 SOA ns1.kpn.net. zonemaster.kpn.com. 2026021903 28800 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0