Moodle 2.4.3 show the home page with SSO

On a Moodle 2.4.3 on Windows 2008 R2 server with IIS. SSO is set up using NTLM.

I want external users out there on the world wide web to be able to see the home page of Moodle before they log in. Currently as soon as we put the web address in, it starts prompting for your windows log on credentials and will not display the home page without them.

I got it to work for a Moodle 2.4.2, but I think that was a fluke, the support document page seems to suggest what I did should not work (anonymous access turned on in IIS under authentication) makes the home page visible and the SSO worked. On a Moodle 2.4.3 if I turn anonymous on the SSO breaks.

Is it possible external users see home page and NTLM SSO working on a Moodle 2.4.3?

Thanks