I have a Plesk Parallels control panel for a webpage where the DNS records don't route outside the host.
The DNS settings seem to work ONLY for domains that are within that provider.
This is a screenshot from the DNS page:
Only the sd4.example.com and sd2.example.com don't work. They are A and CNAME records that point to an external web-app.
Notice that sd3.example.com is a CNAME that does work, but it points to another domain that is using the same host/ip as the top level domain.
Note: Whatever subdomain I type, it serves me with the Parallels "Web Server's Default Page".