Outlook 2003 is Microsoft's personal information management software.
Microsoft Outlook is a personal information manager (PIM) from Microsoft, available both as a separate application as well as a part of the Microsoft Office suite. It includes an email client, calendar and other personal information organization tools.
This version introduces new objects, methods and properties for use in VBA. It is also the last version to feature the classic toolbars most Office users are familiar with, replacing them with the new user interface (UI) called The Ribbon.
outlook-2003 should be used for questions specific to the Outlook 2003 version of the program, to let SO users know your version. There is also a outlook-vba tag if you are asking about VBA.
Links:
