There are three classes of SMTP domains you may want to accept messages for: Local domains, non-local domains and shared domains. See this article for more info on this, and read on.
Local Domain: All of your Exchange 2000 servers accept messages for all domains listed in all Recipient Policies. Start by creating a Recipient Policy that includes SMTP:@domain (e.g., SMTP;@tntsoftware.com) for the address. Check the checkbox for the SMTP domain and the checkbox for This Exchange Organization is responsible for all mail delivery to this address. See this article for information on creating Recipient Policies. Additional information can be found here.
Non-Local Domain: Non-Local Domains are also called Relay Domains. An example of a non-local domain would be the pre-existing domain for a recently acquired company. Another example would be if your company underwent an organizational name change. Start by creating an SMTP connector to the non-local domain. When you do this, check the Allow messages to be relayed to this domain checkbox on the Address Space tab on the Properties dialog for the SMTP connector. Note that the specified source bridgehead server(s) will be the servers that accept messages for this domain. See this article for details on how to configure an SMTP connector.
Shared domain: If you are sharing a domain with another SMTP server and you want Exchange 2000 to receive messages for that domain, you set up an SMTP connector for this domain. Then, add the domain to your Recipient Policies, making sure that the checkbox for This Exchange Organization is responsible for all mail delivery to this address is not checked.
Once you've determined the type of domain you're hosting, configuration is quick and easy.
This was first published in August 2002