Looking for some expertise on a Watchguard XTM product. I have one in place that uses the SMTP Incoming Proxy. I have an external company that I will be using for an online store application that requires the ability to send mail through my internal mail server (Exchange 2007 on an SBS 2008 server). I've configured the Exchange server to allow the relay, but I seem to be getting hooked on at the Watchguard box. What I have is the originating IP address of the external server that needs to be allowed to relay mail from my internal server.