smtp server: virtual domains?

Hello,
I have one physical server, one static ip, and one network. However, I would like to serve email services for more than one domain, but without the domains leaking any kind of information about the other. For example, for smtp, for the domain being accessed, I only want that domain showing up in the email headers and not the other domains.

I hope I made that understandable. Right now I'm using postfix on a linux system. Is there a way I could do this with postfix? a different mail server? or, is this possible at all?

Thanks
-Mike

its a seems standard feature on all the mail servers ive worked with...but i've never worked with postfix. sorry! i just wanted to let you know it was doable