system.inbound.secure-email.nl has no CNAME records.
Question and response
Question
dig system.inbound.secure-email.nl. NS
Answer
The response has no answer records.
Authority
secure-email.nl. 3484 SOA ns1.yourdomainprovider.net. hostmaster.secure-email.nl. 2026011203 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0