Here's a mistake you don't want to make: Give an Exchange 2000 server the same name as your SMTP domain.
For example, if your company's name is Widgetking, and your SMTP domain is Widgetking.com, don't name your Exchange server Widgetking as well. If you do, the server won't be able to receive mail from other servers in the organization.
On the Exchange 2000 server, you'll see events similar to the following:
Event Source: MSExchangeTransport
Event Category: Categorizer
Event ID: 9006
Description: The FQDN of a remote server is also configured as a local domain on this SMTP virtual server. This is causing 5.4.8 NDRs. Please remove 'yourdomain.com' from your recipient policies.
Of course, removing your SMTP domain from the server is rarely an option. Your only practical choice is to rename the server.
This problem can also occur in mixed Exchange 5.5/2000 environments. And if an Exchange 5.5 server is the culprit, it can really cause a problem. Renaming an Exchange 5.5 server has a direct effect on its directory services.
While Microsoft lists this problem as being an Exchange 2000 issue, play it safe even if you've implemented Exchange 2003. After all, there are many safe choices for a computer name.