I don't like that anyone can access login page of smartermail and attempt to login. So looking to use IIS Basic Authentication to add a layer of protection. After spending couple of hours, I couldn't get it working, because when you add SmarterMail as an IIS website, IIS acts as reverseproxy and that somehow breaks things. 

I know my IIS settings are correct because I was able to secure a static website using same procedure, just not the SmarterMail website.

Has anyone been able to successfully secure their SmarterMail IIS site using IIS Basic Authentication?