I am designing an OWA implementation for a client using Exchange 2003. The client is using a PostFix server to receive all Internet e-mail before forwarding to their Exchange environment. We want to implement OWA and put up a FE server in their DMZ. TechNet article "Configuring an Internet Firewall" (http://technet.microsoft.com/en-us/library/aa995743.aspx) suggests that the FE server needs to receive TCP ports 443, 993, 995, and 25. I would like this server to receive 443, 993, and 995 and leave the Postfix server receiving traffic on port 25. I think that the FE server's 'Smart Host' could be setup to receive from the Postfix server. However, I would like to confirm this.Thank You!

You'd need to allow 25 inbound from the postfix server's IP only.

Thank you! That is what I thought and will try it.God bless!