Before planning the development of a client application, you might want to consider extending the Microsoft Exchange client application. Microsoft Exchange provides a large number of features that enable users to view, search and sort information in the information store. It also provides a development platform for electronic mail, messaging, and workgroup applications that can handle a broad spectrum of information sharing tasks.
Instead of recreating features that are already provided in Microsoft Exchange, you can leverage the existing features and user interface of Microsoft Exchange and add your own custom features, also known as "extensions." You can override the default behavior of almost any feature of Microsoft Exchange. The use of extensions can save a considerable amount of development effort that would otherwise be devoted to creating a custom user interface and custom features.
Additionally, extending the Microsoft Exchange client benefits users by integrating capabilities from many different ISVs into a single user interface, rather than having multiple interfaces through which users accomplish their information sharing tasks.
Microsoft Exchange client extensions can run on any platform that is running the Microsoft Exchange client. This includes Microsoft® Windows® 3.1, Windows® for Workgroups 3.1, Windows NT®, and Windows® 95 operating systems. Since the Microsoft Exchange client is included with Windows 95, any extension you develop can run on any computer running Windows 95 — it is not necessary for the user to purchase a separate product to use your extension on Windows 95.