I am working in a Project were we plan to replace the existing ISA server with IIS ARR, for Lync and Exchange. But when testing reverse proxy for Lync and Exchange with IIS ARR in my test lab I just realized that it turns out that IIS ARR is not that happy about configuring reverse proxy to internal servernames with underscore in the servername (e.g.: lync_frontend.mydomain.local). I get an error message when trying to configure the Server Farms' server address. Maybe somebody else have experienced the same problem and maybe has a workaround for this?