Directory

Applications use directory objects to find and gain access to services, mailboxes, recipients, public folders, and other objects that are addressable within the messaging system. Applications you develop must frequently access the directory to look up information about objects in a Microsoft Exchange Server system.

The directory consists of two components: the directory database and the directory service agent. The directory database stores the information provided by the directory. The directory service agent manipulates information in the directory database and handles directory requests from applications and services.

Microsoft Exchange Server directory functionality is implemented through two separate, but related structures:

• The directory information tree (DIT), which describes how objects in the directory are logically configured to represent an organization into which Microsoft Exchange Server is installed.
• The directory schema, which defines the directory's object classes and their inheritance structures.

In Microsoft Exchange Server, directory objects defined by other messaging systems (such as SMTP and X.400) are referred to as external objects and are accessible from within the Microsoft Exchange Server messaging environment.

Applications access directory information through two mechanisms:

• Microsoft Exchange Server directory access functions, which are most often used for setting up and maintaining applications and by server applications where appropriate.
• MAPI address book functions from both server- and client-based applications. MAPI address book functions can also be used to write information to the directory and to create objects of selected classes in the directory.

Subject to a small amount of latency time needed for the directory replication process, every Microsoft Exchange Server directory within an organization has the same directory objects. Administrators and applications can frequently add, delete, and modify directory objects, and changes to one copy of the directory will be periodically propagated to all other copies of the directory on all other servers. The directory exchange agent synchronizes directory contents with directories on other servers.

Maintaining synchronization on directories that reside in different messaging systems is an important administration and design issue. No periodic synchronization mechanism for a specific subset of directory objects is provided. However, you can design a utility that runs as a service of Windows NT Server.

For detailed information about the directory, see the Microsoft Exchange Server documentation in the "Database and Messaging Services" section of the Microsoft Platform SDK.