Iis 7.5 Dot Charachter Login Problem

[robotica2]

I have IIS 7.5 installed on my Windows 2008 R2 Server.

the web site using Windows authentication is deployed on the server.

 

Users whose login names contain only letters can access to the web site from Internet or from the same domain IIS 7.5 belongs to without any problem.

 

The problem is users whose login name containes dot charachter(for example firstname.lastname).

These users can access only from the machines that resides inside the same domain as IIS 7.5.(but not from Internat).

 

Any solutions?