Web server protection with Exchange 2013 CU13 and having issue with Authentication pop windows

Hi Guys,

I have two Running Exchange 2013 CU13 Server and i am using Sophos Web server Protection for virtual web server for Exchange 2013. I have a problem with if i start to use More than One Real Web server I start to have a issue with External and mac clients.

The Password Pop UP windows Always Pop UP and even i enter the user name and password it does not accept it and the Pop window always comes up and this is always happening only with External clients and the Mac Outlook clients.

I have exact the Same Configuration on my Both Exchange 2013 Server.

Server A and Server B both Uses NTML for authorization.

When i use only one real Web-server then all works Fine and even i can make any server A or Server B as a client facing and all works fine for internal , external and mac clients.

So basically the Load balancing or High Avalabilty of Exchange server having issue for the mac and external Clients.

I am adding some configuration of my Webserver protection which might be helpful for someone to make suggestion to solve this issue.

Please let me know if you have some suggestion for me. I will be really Grateful of any Comment