About MS Exchange Directory

Microsoft Exchange server stores information about its numerous objects (such as mail recipients, gateways, etc.) in a large hierarchy called Directory. There are hundreds (if not thousands) of objects there. For example, each user mailbox is represented by an object in the Directory, as well as each gateway, addressing template, etc. The Directory plays very important role for MS Exchange server storing all configuration data. Thus, in a certain sense it may be compared with Windows NT Registry. The Directory plays the same role for MS Exchange server as Registry plays for Windows NT operating system.

Architecturally the MS Exchange Directory consists of the following two components:

Directory Database
Directory Service Agent (DSA)

The database stores all relevant data and the DSA is a tool which is used to access and modify this data. The directory service agent may be used programmatically.

Directory database contains two separate but related sub-components:

Directory Information Tree (DIT) - a collection of objects with their properties which collectively describe current MS Exchange Server configuration.
Directory Schema - abstract description of object types possible in this directory with a list of properties and definitions of parent-child relationships. Directory schema does not contain any physical objects but rather describes their types. Real objects are stored in the Directory Information Tree.

How would I access properties of objects stored in the Directory? How can I view and modify them? Let us consider available options.

Exchange Administrator gives you a tree-like view on many of the directory objects. For example, you can view and modify recipients easily.
Directory API (DAPI) allows for programmatic access to directory objects.
Regular MAPI interfaces also allow programmatically view and modify object properties.
MS Exchange Directory can also be accessed via Active Directory Service Interfaces (ADSI). This book does not cover ADSI.