prtg.systemec.nl has no CNAME records.
Question and response
Question
dig prtg.systemec.nl. NS
Answer
The response has no answer records.
Authority
systemec.nl. 1779 SOA ns.systemec.nl. postmaster.systemec.nl. 2026020503 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0