I receive a notification about certification that is about to expire but I don’t know this subdomain: wp53
the full domain is: wp53.moonloop-records.com
I have the domain : moonloop-records.com hosted on my server but not the subdomain
You have your own name server ns1.moonloop-records.com. Did you use other name servers? There are some free hoster, there it's possible that everyone can create subdomains if the domain is registered.