Configure MS Exchange
Configuring MS Exchange to send and receive internet emails isn't hard. Usually it involves four steps: a) setting up a send connector for outbound email, b) configuring the receive connector for inbound emails, c) adding your domain name to the accepted domains or the default policy and d) adding appropriate email addresses to your users mailboxes. These guides list the actions necessary to configure your Exchange server in a standard way so it works well with POPcon and the Internet.
Exchange Configuration guides
Step by step guides with many screenshots.
Configuration of Exchange 2010 Server (also for Windows 2011 SBS)
Configuration of Exchange 2007 Server (also for Windows 2008 SBS)