[MallyMal]

OK, I just bought an Xserve with the intent of hosting websites. I have found documentation that allows me to host multiple sites on one server. However, how can I give those sites unique e-mail addresses?

It says in the documentation that Apple does not support e-mail virtual domains. So, how can I get each of my clients a unique e-mail address?

Also, how can get e-mail aliases?

[Rickster]

Use a different mail server.

Sendmail is included in your OS X Server installation, and supposedly it's preconfigured to deliver messages such that you can still use AppleMailServer for POP/IMAP serving. You just need to switch it so SMTP services use it instead of AppleMailServer... I think the Admin Guide tells you how.