Outlook AddIn to determine why a receiver got an email.
Uses:
Microsoft.Office.Tools.Outlook.OutlookAddInBase to implement Outlook Add-In.
Microsoft.Office.Tools.Ribbon.RibbonBase for the Ribbon.
Microsoft.Office.Outlook.Application to get Outlook application instance.
Microsoft.Office.Outlook.ExchangeUser to get AddressEntry for an Exchange user.
Microsoft.Office.Outlook.ExchangeDistributionList to get AddressEntry for an Exchange distribution list.
Microsoft.Office.AddressEntries as collection of AddressEntry objects.