Okay, the server is running and most of the important emails were already migrated from the old mail server.
I now, change the IP address from the Class "C" private ip (192.168.0.xxx) to a Class "A" private ip (10.0.0.xxx), I also changed the ip's on the resolv.conf and /etc/hosts files. I transferred physically the server from my workarea to the server room, and upon testing, email doesn't work. I tried "telnet localhost 25" and tried sending test email but to no avail.
Are there any other files, which I need to reconfigure?