So I just need a stream and proxy_pass it to our Exchange? (I'm new to Nginx, haven't seen stream config before; we're using SSL for everything).

Also, is it possible to have a combination? The deal is: the current setup in our company is only 1 public IP address for a couple of services. Which used to be fine, since SSL was only used for Exchange (and our firewall was configured to only send the HTTP-traffic to the Nginx, and HTTPS to Exchange). But now, I need to able to split it out, based on the names ( apps.domain.ext and mail.domain.ext ).