I've got an old crusty WHM/cPanel server which I'm trying to get rid of. I've got a new setup on shared hosting which is much cheaper in the long run.

The problem is that there are a bunch of websites on the server whose domains I don't have access to. They're currently pointing to name servers of my domain (ns.mydomain.com), but the new provider has their own name servers (ns.provider.com) which I have to use instead.

My initial idea was to set up a CNAME to point my name server to my provider's: ns.mydomain.com CNAME ns.provider.com, but I read in this question that this would be a bad idea. The accepted answer suggests using an A record instead, and I want to make sure how this would work.

Assuming ns.provider.com has an IP address of 123.123.123.123, is it just a matter of doing ns.mydomain.com A 123.123.123.123? Is there any way the provider could block those requests as the name server domain technically doesn't belong to them?