If you provide external access to Microsoft Office 2007 R2 Communicator Web Access Server for your users, you need to make sure your users are enabled for remote user access.
If your users are not enabled for remote user access and they attempt to access OCS 2007 R2 externally, they will get an “Cannot sign in because your user account does not permit external access to Microsoft Office Communicator Web Access server. Contact your system administrator.” error message.
