How to Configure an SMTP Virtual Server to Resolve Anonymous Email Addresses
After you have restricted access to a receiving bridgehead server, you must configure the SMTP virtual server on the bridgehead to resolve anonymous e-mail addresses.
Before configuring an SMTP virtual server to resolve anonymous e-mail addresses, it is recommended that you review the topic Synchronizing Multiple Exchange 2003 Forests.
Procedure
To configure an SMTP virtual server to resolve anonymous e-mail addresses
Open Exchange System Manager.
In the console tree, expand Servers, expand < Bridgehead Server Name >, expand Protocols, and then expand SMTP.
Right-click the SMTP virtual server you want, and then click Properties.
On the Access tab, click Authentication.
In Authentication, ensure that the Anonymous access check box is selected, and then select the Resolve anonymous e-mail check box.