I am trying to setup Xeams as a firewall for incoming email only to an Exchange 2010 SBS Server. I am using a separate box for Xeams plugged into the same network switch as the exchange server running at IP 192.168.27.11. I added the Xeams computer to the domain. Pointed the firewall to send port 25 to the Xeams box (192.168.27.5). Gave Domain admin and Exchange admin access to Xeams. Xeams can ping the exchange server. The exchange server is always listening on port 25 and works fine without Xeams.

I setup Xeams SMTP Proxy only since I only want to filter inbound messages. Proxy port 25, Bind to 192.168.27.5, Server Host 192.168.27.11, Server port 25

I was able to setup Active Directory Integration and have the users added to Xeams.

Here is the problem.

No emails are received. Ran Xeams diagnostics and Server Communications shows 'Xeams could not connect to your corporate SMTP server'. All other tests, except Open Relay, passed. Open relay always fails when Server Communications fails.

Any suggestions would be greatly appreciated.

Found the answer to this for any who may run into this issue.

The problem was Exchange 2010 refusing the connection.

By default Exchange 2010 does not allow inbound unauthenticated mail by default.  This applies to All mail, not just mail from your application.  This is because Microsoft expects you to use an Edge Transport server.  if you do not, you need to adjust your default receive connector to allow "anonymous".  This will allow inbound mail and will not make you an open relay.

You can find this setting in the Exchange Management Console>Server Configuration>Hub Transport>Receive Connections-Default xxxx>Permission Groups: check the Anonymous Users box>OK