Reverse proxy for mailserver (SMTP + HTTP for web client)

Question

I'm looking at doing some reverse proxy work for a mail server with corresponding web client. Both servers are running on the same machine, this is not a server with a high load. :)

The solution I've discussed with friends is having the mail server/web client on our internal network. Then to put a reverse proxy on the DMZ to service both SMTP and web client HTTP-traffic to the mail server on the internal network.

From what I understand this is the recommended secure solution?

So far I've thought for the SMTP-proxy part of using postfix which will receive mail, do some spamhause and similar anti-spam measures and if it all checks out, send the mail to the mail server on the inside. The mail server on the inside will send all outgoing mail to the proxy which will then send it out on the Internet.

For the web client I'm not sure exactly which software I should be running on the proxy machine, I've been thinking about using Squid -- but that's basically based on the fact that I know squid is a http proxy. The web client data will be sent out over SSL.

Reading around some here on Serverfault I've seen other people using Apache with mod_proxy+mod_security for similar situations.

Am I thinking correctly for this solution?
What software would you guys use and with which modules?

Thanks in advance for the help! :)

Solution

http://www.postfix.org/VIRTUAL_README.html

Postfix has support for domain-based forwarding built in. You can use this to either delivery mail to virtual hosts on the same server as Postfix or to servers on your internal network.