Follow below steps to configure SMTP Server:
Click Start, point to All Programs, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
In IIS Manager, expand the server name that contains the SMTP server that you want to configure.
Right-click the SMTP virtual server that you want to configure, and then click Properties.
On the Access tab, under Access control, click Authentication.
In the Authentication dialog box, under Select acceptable authentication methods for this resource, verify that Anonymous access is selected.
On the Access tab, under Relay restrictions, click Relay.
To enable relaying from any server, under Select which computer may relay through this virtual server, select All except the list below.
To accept relaying from one or more specific servers, follow these steps:
Under Select which computer may relay through this virtual server, select Only the list below.
Click Add, and then add servers one at a time by IP address, or in groups by using a subnet or domain.
Click OK to close the Computer dialog box.
Click OK to close the Relay Restrictions dialog box.
Click OK to close the Properties dialog box.