I am having some issues getting my Exchange server to allow me to relay. I am running a single stand-alone exchange 2010 server.
The way this works - I have my voice mail server (Windows server 2012). When a VM is left, an email is generated and sent to a defined address in my PBX. As long as the user is in my email domain, no problem. The problem arises when I attempt to send to an external domain (testing with gmail).
So, the VM server utilizes IIS 6.0 and the SMTP virtual server. The basic setup for the PBX is to set a SmartHost in the outbound delivery. Here I define my Exchange server.
For relay, I decided NOT to just open up the relay, but to authenticate. Easy enough. I've created a whole new AD account and created a mailbox for it. In IIS 6 on the VM server, I created new remote domain "gmail.com" and edited ti's properties. I entered my Exchange server as the smart host. I went ahead and setup integrated Windows authentication and put in the username and password of the newly created user.
Runing my tests result in a 5.7.1 user does not have permissions to send to this mailbox, and I can confirm that we are authenticating (by running wireshark on both the VM server and the exchange server).