Start Internet Services Manager from the Administrative Tools menu.
In the Internet Information Services console, right-click the Default SMTP Server node, and then click Properties.
Click the Access tab, and then click Authentication.
If you click to select the Anonymous access check box and do not select any of the other checkboxes, all users and computers will be able to access the IIS SMTP server. This effectively disables authentication. If you click to select either or both the Basic Authentication or the Windows security package check boxes and do not click to select the Anonymous access check box, authentication will be required before access is granted to the IIS 5.0 SMTP server. In this case, if the user or computer does not successfully authenticate, the user or computer cannot send mail to the server. Select either or both of these options, click to clear the Anonymous access check box, and then click OK.
Click Relay.
You have several available options in the Relay Restriction dialog box. The default option is Only the list below. Note that there are no entries in the default configuration. By default, the Allow all computers which successfully authenticate to relay, regardless of the list above option is enabled. This allows users and computers that can authenticate with the server to relay through the server. Note that if you allow only anonymous access, the server will not be able to authenticate users or computers.
Click Add. You can allow a single computer, a group of computers, or an entire domain to relay through the server by making the appropriate selection in the Computer dialog box. Click Cancel if you do not want to make a change.
In the Relay Restrictions dialog box, click OK.
