Creating multiple email accounts on diffrent domains without creating local users with postfix?

So I have trying to figure out how to configure postfix to handle multiple emails for different domains. So I would need for each domain: noreplay@domain1.com user1@domain1.com user2@domain1.com

but as well noreplay@domain2.com user1@domain2.com user2@domain2.com

Problem is I want these accounts to be separate. From my understanding in the /etc/postfix/virtual you would have: noreplay@domain1.com username noreplay@domain2.com username

However both of these accounts would go to the /var/mail/username

As well I don’t need for each user to have access to the server just there mail which all of them will be using a third-party client (most likely Thunderbird) to pull down the mail.

I’m not interested in third party solutions like Google Apps and stuff the redirects the mail I actually want to host it.

Any ideas? -Julian