Microsoft Exchange Server 5.5 and later, including service packs, provides messaging and collaboration features to the corporate computing environment. Microsoft Exchange implements the Messaging Application Programming Interface (MAPI) and directory access functions for much of its functionality, though newer technologies such as Collaboration Data Objects (CDO) and Active Directory Service Interfaces (ADSI) are more easily integrated into the architecture of n-tier applications.
The Microsoft Exchange Server architecture includes two primary data stores: the directory and the information store.
The directory serves as the central repository of user information for Microsoft Exchange Server within an organization. The directory consists of a directory information tree, which holds the actual information, and a directory schema, which describes the relationships between directory elements. Information is stored in the directory using a hierarchical object model.
The Microsoft Exchange Server directory contains objects that are the principal means for applications to find and access services, mailboxes, recipients, public folders, and other addressable objects within the messaging system. For example, if a directory object represents a public folder with its own destination address, users and applications can send messages directly to the public folder through the messaging system.
The information store is the default message store provided for Microsoft Exchange Server. The information store consists of four implementations of MAPI message stores: the public information store, the private information store, the offline information store, and the personal folder store. The information store organization of public folders, private folders, and messages is referred to as the organization hierarchy. Another implementation of a MAPI message store is configured when a user works offline. It is called the offline folder store and mirrors the structure of the mailbox while offline.
Programmers can use ADSI to access information in the Microsoft Exchange Server directory and information store. Both the directory and the information store are hierarchical and object-oriented, allowing for easy programmatic access.
For more information about Exchange, see the site http://www.microsoft.com/exchange.