Hi @Gary Nicholson​ this is determined by your Operating System.

If you log on to the Server (assuming you're running a Windows environment).

Start > Run

type cmd and click OK

type in ipconfig /all and press Enter

You will see the DNS Servers that are configured for that Server.

I would recommend contacting your IT Department if you need additional information.

Thanks @cory​, that's what I suspected. The bad DNS server has been fixed now so we didn't have to make any changes.