I am working on configuring the Mail Exchange settings for PacificyearlyMeeting.org, and am tracking things like DNS reverse lookup, and other necessary configuration steps. The number of considerations is quite confusing, but I have found a great tool that checks for multiple problems and explains what each test means. The tool is called the MX Toolbox Super Tool, and it has been really informative.
To use the MX ToolBox Super Tool, simply enter the IP address or domain name of the server in question and let the tool scan for mis-configurations, blacklisting, etc. When something seems confusing or unknown, click the link next to the error or warning for an explanation. This tool has been educational!