Close the SMTP relay

This sample configuration based upon the domain "nevada.ch" and a private network adressed by "192.168.1.0/255.255.255.0".

Doubleclick on "Internet Mail Service" in the "Microsoft Exchange Andministrator" found under "NEVADA/NEVADA/Configurations/Connections".

Open the "Routing" Tab.

Select "Reroute incoming SMTP mail".

Click on the "Routing Restrictions...." tab.

Check the "Hosts and clients that sucsessfully authenticate" radio-button and also the "Hosts and clients with these IP addresses" radio-button.

Now use the top "Add..." button to add new hosts.

Insert the IP-Address of your private subnet or hosts with the "Mask" of 255.255.255.255 which will have full access to the mail services. Never insert here the IP address of the firewall or router.

After clicking on the "OK" button in the "Add/Edit Host" window, the "Routing Restriction" windows should be simular like this:

By closing the "Routing Restriction" windows, the "Microsoft Exchange Andministrator" mentions that these changes will be active after a restart of the Exchange Server.

Open the "Services" window and restart the "Microsoft Exchange Message Transfer Agent". Windows will ask you to also restart the "Microsoft Exchange Internet Mail Service" which is ok and should be accepted.

Now only E-Mail traffic to and from your domain, in this case "nevada.ch", will be routed by your server.