exchange server or any mail server

How can I setup creating multiple account just like microsoft outlook but uses only INTRANET. We are using Calypso but security is not very tight and I want in the future to connect to Internet. How can I configure Microsoft Exchange Server. I don’t have any experience on using it. Can you please tell me in a step by step way in creating multiple email account with single ISP and setting it up in the exchange server. What current version should I use?