SMTP virtual servers have two roles in the Exchange organisation. They handle mail transport and they handle mail submission. This means that servers use SMTP to deliver messages and clients use SMTP to submit messages.

When you install the first Exchange 2000 Server in an organisation, a default SMTP virtual server is created. The default SMTP virtual server is used for mail transport and for mail submission.
In most cases you won't need to create an additional SMTP virtual server. However, if you're hosting multiple domains and you want to have more than one default domain, you may want to create additional SMTP virtual servers to service these domains. Another reason to create additional SMTP virtual servers is for fault tolerance. When you have several SMTP virtual servers, one of the servers can go offline without stopping message delivery in the Exchange organisation.

By default, SMTP virtual servers deliver messages to other servers without authenticating themselves. This mode of authentication is referred to as anonymous. You can also configure SMTP virtual servers to use basic or integrated Windows authentication. However, you'll rarely use an authentication method other than anonymous with SMTP virtual servers. In fact, one of the only times you'll use basic or integrated Windows authentication with an SMTP virtual server is when the server must deliver all e-mail to a specific server or e-mail address in another domain. That is, the server delivers mail to only one destination and doesn't deliver mail to other destinations.

If you need to configure authentication for e-mail delivered to a particular server and also need to deliver mail to other servers, you should configure an Exchange connector to send mail to that specific server and use anonymous authentication for all other mail.

To view or change the outbound security settings for an SMTP virtual server, complete the following steps:

1. Start System Manager. If administrative groups are enabled, expand the administrative group in which the server you want to use is located.
2. In the console tree, navigate to the Protocols container. Expand Servers, expand the server you want to work with, and then expand Protocols.
3. In the console tree, expand SMTP. Right-click the virtual server that you want to work with, and then select Properties.
4. In the Delivery tab, click Outbound Security. To use standard delivery for outgoing messages, click Anonymous Access.
5. To set basic authentication for outgoing messages, click Basic Authentication. Under User Name and Password, type the account name and password that are required to connect to the remote server.
6. To set integrated Windows authentication for outgoing messages, select Integrated Windows Authentication, and then under Account and Password, type the Windows account name and password that are required to connect to the remote server.
7. Click OK twice.