Apple Mail Server on 10.2.2 Help Needed

HELP PLEASE!! I have recently bought for our company a Apple Macintosh Xserve. I have set the Xserve up with basic file sharing using 10.2.2 Jaguar server and now need to set up mail using the built in Apple Mail Server. I'm looking for someone to provide me a step by step idiots guide on setting up the mail server including all necessary steps to be taken in regard to security spamming etc. I am more than happy to pay for this if anyone is able and willing to help. The setup we have is as follows our ISP provides an ADSL connection and hosts our domain name, we have 5 static IP address and the ISP has setup a MX record to point all mail sent to our domain to be forwarded to one of the static IP's. Connected to our router is a Watchguard Soho firewall, this is configured with the static public IP our mail is sent to. We have set the firewall to pass all mail traffic on port 25 to the private IP address (192.168.111.2) of the Xserve. (Our client machines receive there IP from the built in DHCP server in the Watchguard Firewall but the Xserve's private IP is static) What I now need to know is how and what I need to configure on the Xserve step by step to get mail correctly working. I understand the setting up of users and groups and enabling then to have an email address but that is about it. I have been told that I need to configure DNS etc as my server is on a private IP???? I hope someone is able to help and as I said I am more than happy to pay anyone that could provide a guide. I have tried other sources and have only found other people who seem to be struggling like myself!! :cry: