mxsin.de.kpn-eurorings.net has no MX records.
Question and response
Question
dig mxsin.de.kpn-eurorings.net. MX
Answer
The response has no answer records.
Authority
kpn-eurorings.net. 3600 SOA ns1.kpn.net. zonemaster.kpn.com. 2026022601 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0