Distinguished Name

Distinguished Name is the native address format for recipients in Microsoft Exchange Server.

What is Distinguished Name?

The native address format for recipients in Microsoft Exchange Server. Also, one of the addressing formats for objects within Active Directory in Microsoft Windows 2000. Distinguished names are part of the X.500 directory specifications and are used for locating and accessing objects using the Lightweight Directory Access Protocol (LDAP).

How It Works

In Active Directory for Windows 2000, every object in the directory has a unique name. Three kinds of names can be used to define a specific object in Active Directory:

  • A distinguished name, which specifies the complete path to the object through the hierarchy of containers
  • A relative distinguished name (RDN), which is the portion of the name that is an attribute of the object itself
  • A user principal name (UPN), which is the name used when a user logs on to the network

For example, consider a user object within Active Directory. A user object is an example of a leaf object because it cannot contain other objects. User objects such as Jeff Smith are identified using common names (CNs). A container is a directory object that can contain other objects. In Active Directory, containers are referred to as organizational units (OUs) because they are used to organize other objects into hierarchies of containers. For example, the user Jeff Smith would typically be contained within the Users container. At the top of the container hierarchy are the containers that represent different components of the domain itself. These components are called domain components (DCs). For example, if user Jeff Smith exists in the microsoft.com domain, the distinguished name for this user is represented by the path

DC=com,DC=microsoft,OU=Users,CN=Jeff Smith

In Microsoft Exchange Server, distinguished names are used to identify recipients. Exchange automatically creates a distinguished name for every recipient object in its directory database, including objects such as mailboxes, distribution lists, and public folders. For example, if a user Jeff Smith has a mailbox named JeffS located on an Exchange server in Redmond at the organization Microsoft, the distinguished name for this user would be represented internally as


The Message Transfer Agent (MTA) uses a recipient’s distinguished name to determine how to route messages to that recipient within an Exchange organization.


Exchange Server also automatically generates X.400 addresses for every object in the directory. Don’t delete these addresses, even if you have no X.400 Connectors installed in your sites, because if Exchange Server cannot use a recipient’s distinguished name for any reason, it uses the recipient’s X.400 address for message routing.