How to Verify the Inbound Port and IP Address

To configure your SMTP virtual server to receive Internet mail, you must perform the following tasks:

Configure the inbound port as 25 and specify the IP address Other servers on the Internet expect to connect to your SMTP virtual server on port 25. By default, all SMTP virtual servers use this port. For detailed instructions, see the procedure below.
Verify that your SMTP virtual server allows anonymous access To receive Internet mail, your SMTP virtual server must permit anonymous access. Other servers on the Internet expect to communicate anonymously with your SMTP virtual server to send Internet mail to your users. For detailed instructions, see How to Verify an SMTP Virtual Server Is Configured to Allow Anonymous Access.
Verify that default relay restrictions are configured on your SMTP virtual server By default, the SMTP virtual server allows only authenticated users to relay e-mail messages. This setting prevents unauthorized users from using your Exchange server to send e-mail messages to external domains. For detailed instructions, see How to Verify an SMTP Virtual Server Is Not Set to Open Relay.

Procedure

In Exchange System Manager, in the Properties dialog box of the SMTP virtual server, on the General tab, click Advanced.

The Advanced dialog box appears (see the following figure). By default, your SMTP virtual server uses an IP address of All Unassigned, which means that the virtual server listens for requests on all available IP addresses. You can keep the default IP address, or click Edit to change the address. By default, your SMTP virtual server uses TCP port 25. It is recommended that you do not modify the default port assignment.

Advanced dialog box