These are the nameservers returned with
dig +short caulus-kaulille.be NS
Online tools such as DNS Checker shows different records depending on the server queried.
So the domain is definitely not served through Netlify.
Querying Google Dig shows the same results as above and shows an A record of
22.214.171.124 Zoho Toolkit shows none (at the time I checked.) This A record is present in
dig @een.dnssrv.nl caulus-kaulille.be A) but does not appear in the
microsoftonline.com servers (try
dig @ns2.bdm.microsoftonline.com. caulus-kaulille.be A). EDIT Using DNS Checker to search A records shows a mixture of hit and miss.
Hope this helps.