nsauth1.introweb.nl has no CNAME records.
Question and response
Question
dig nsauth1.introweb.nl. NS
Answer
The response has no answer records.
Authority
introweb.nl. 1709 SOA nsauth1.introweb.nl. postmaster.introweb.nl. 2020070802 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0