This tutorial shows how to set up Zimbra Collaboration Suite - Open Source Edition on CentOS. This tutorial covers installation of CentOS, dependencies for ZCS and setup of Split DNS when working behind a firewall. This tutorial is based on the way I set this server up and is only a suggestion. It carries no guarantees and it is highly suggested that you do this on a test server first to verify functionality. If you don't have a test server available you should download VMWare Server 1.0 and perform this tutorial on a test virtual server.