Configure SMTP on IIS (Windows 2003)

Step 1: Verify the Installation of the SMTP Service
In Control Panel, open Add/Remove Programs, click Add/Remove Windows Components. Click the Internet Information Services (IIS) component, click Details, and then verify that the SMTP Service check box is selected.
If it is not selected, click to select it, click OK, and then follow the installation directions that are displayed.

Step 2: Configure the SMTP Service to Relay for Internal Domains
Depending on the scenario, it may be necessary to configure the SMTP service to relay inbound messages for your internal domains.
Click Start, point to Programs, click Administrative Tools, and then click Internet Services Manager.
Expand the tree under the server name, and then expand the Default SMTP Virtual Server. By default, you should have a Local (Default) domain with the fully qualified domain name of the server.

Configure the domain for inbound:
Right-click the Domains icon, click New, and then click Domain.
Click Remote, click Next, and then type the forwarder.gm.com in the Name box. Click Finish.

Configure the domain for relay
In the properties for the domain that you just created, click to select the Allow the Incoming Mail to be Relayed to this Domain check box.
If this is being set up for a internal domain, you should specify the server that receives e-mail for the domain name by the IP address in the Route domain dialog box.
Click the forward all e-mail to smart host option, and then type the IP address of the server that is responsible for e-mail for that domain in square brackets. IP of forwarder.yourcompany.com is:
[168.208.12.12]
Note: Typing the IP address of the server in brackets is necessary so that the server recognizes this is an IP address and not to attempt a DNS lookup.
Click OK.