Client Components

A client may be located on a Microsoft Exchange Server computer or on a user's workstation. Client applications expand the capabilities of Microsoft Exchange Server. They employ services of Microsoft Exchange Server, but provide no services of their own. The Microsoft Exchange Client or a client application communicates with Microsoft Exchange Server through MAPI.

The following diagram shows a typical arrangement of client components on the user's workstation.

Microsoft Exchange Client components

The Microsoft Exchange Client computer contains the following components:

• Microsoft Exchange Client Provides e-mail delivery through user mailboxes, and provides information sharing through public folders.
• Client extension Adds functionality to an existing client. Added buttons or menu options — not a new user interface — invoke this new functionality
• Client application Any application other than the Microsoft Exchange Client or Schedule+ that accesses services of Microsoft Exchange Server.

MAPI is used by clients, services, and applications to access Microsoft Exchange Server directory and information store objects. Although Microsoft Exchange Server offers several different programming interfaces, the majority of operations performed in a Microsoft Exchange Server environment use MAPI functions. For more information, see the MAPI Programmer's Reference.