Configuring the remote domain for the SMTP mail relay server in WIN 2003

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This article describes how to configure a remote domain for the Internet Information Services (IIS) Simple Mail Transfer Protocol (SMTP) mail relay server.

IIS in Windows Server 2003 includes a full-featured SMTP virtual server that you can use to deliver messages on your internal network. The SMTP virtual server can also be used to accept messages from the Internet. Although the SMTP service does not provide an easily accessible message retrieval mechanism, it is important for accepting mail from the Internet and relaying mail to SMTP/POP3 servers. You can configure the SMTP virtual server to accept messages for the domain to which the computer belongs, and for other domains.

Using a stand-alone server running the SMTP service is a good security measure because it acts as the isolation layer between an enterprise mail server and an inbound connection from the Internet. A stand-alone computer that is based on Windows Server 2003 isolates the server from the Active Directory security boundary of the internal network. You can configure a stand-alone SMTP virtual server to use the corporate mail server as a smart host. You can then configure a stand-alone SMTP virtual server to relay messages that are sent only to remote domains. In this case, all other messages will be rejected and not relayed.

How to configure a stand-alone IIS SMTP server to relay to a remote domain

Start Internet Information Services Manager or open the Internet Information Services (IIS) snap-in.

Expand the server name, where the server name is the name of the server, and then expand the default SMTP virtual server.

Right-click the field, point to New, and then click Field.

Click Remote, and then click Next.

Type the name of the new remote domain in the name box.

You can specify a single field, or you can use an asterisk (*) as a wildcard character (the asterisk must be at the beginning of the name and you want to separate the asterisk from the rest of the name with a period) to specify multiple fields. For example, if you need a remote domain to receive messages from other domains. com and all of its subdomains, you can use the name *. other domain. com.

Click Finish.

In the right pane, right-click the new remote domain that you just created, and then click Properties.

Click the General tab.

Under Select the appropriate settings for the remote domain, click the Allow inbound mail relay to this domain check box to select it so that the SMTP server can be used as a mail relay.

Under routing domain, click Forward all mail to smart host, and then type the IP address or fully qualified domain name (FQDN) of the corporate mail server for the internal network. If you use an IP address, be sure to enclose the IP address in parentheses "[]". For example, [nnn.nnn.nnn.nnn].

Click OK.

Stop and start the SMTP virtual server. To do this, right-click the default SMTP virtual server, and then start alone.

Troubleshoot

After the remote domain is configured, all messages sent to the remote domain name will be relayed to the smart host you configured. Messages that cannot be delivered are stored in the Inetpubmailrootbadmail folder.