Default role membership

I seem to recall that I somewhere configured a default role for all New users.
I want all New users to automatically be a member of "External" role, I think I did configured it during installation, but it is not working anymore.
Am I totally wrong or do you have any way I can set this?

The only thing I can think of is that you can configure which SharePoint group users are automatically added to with the Membership Request web part.