In the Folders pane, right-click the backend server farm you want to work with and click New » Backend Server.

Ensure Enable This Backend Server is selected.

Type the name associated with the new backend server.

To enforce MAC address checking, click the Enforce MAC Address Checking checkbox.

If you selected MAC address checking, enter the RSOE MAC address using the IEEE 802 MAC-48 format. To get the MAC address in the correct format, look in the Relay Server Outbound Enabler console or log. Multiple MAC addresses separated by an exclamation mark (!) are reported by the Outbound Enabler if multiple adapters are currently active on your backend server computer. Select the most permanent one for the Relay Server to check against. The ipconfig /all command on Windows provides a detailed listing of your network adapters together with associated MAC addresses.

Specify the security token that is used by the Relay Server to authenticate the backend server connection. You can use a maximum of 2048 characters.

If desired, type a description of the backend server in the Description field.

Click Apply to continue adding backend servers or OK to add the backend server and close the Create Backend Server window.