The following information will be helpful for anyone using mail programs from Microsoft:
Mail messages opened from xTuple are processed as .eml files. If you are using Outlook 2003 or Outlook 2007, then you must apply the latest updates and certain registry changes so that Outlook will recognize .eml files. Outlook 2010 supports .eml files natively. More information is available here: http://www.msoutlook.info/question/354.
Exchange 2010 has IMAP services disabled by default. Read your installation instructions on Exchange to enable IMAP service. You can also start with online resources published by Microsoft here: http://technet.microsoft.com/en-us/library/bb124022.aspx.