I am new to Zimbra/hosting email and I have a configuration question. I want to setup my Zimbra server on the local network behind my firewall. My domain name is hosted on the web, and the public IP resides on my firewall. I can create the appropriate MX/A records for the domain and point them to the public IP, and I can setup DNS on my firewall if necessary. What do I need to do to make Zimbra work with this configuration?