Firstly, to ensure that the process works properly:
Log in to your domain provider’s site.
Find your domain and go to the management screen.
You may have previously used some custom NameServers. You will need to remove these, by choosing to delete, or not use them.
Go to the DNS management screen, and remove all the records that are there (some providers may force you to leave a single MX record in place)
Now you are ready to connect your custom domain. To do this, skip to this tutorial.
