Understanding Exchange Migration

When migrating Exchange mailboxes, Migration Wizard copies directory and mailbox information from the source Exchange server and directory service (Exchange Directory or Active Directory) to the target Exchange 2000 server and Active Directory forest. The steps Migration Wizard performs to accomplish these tasks are based on Active Directory searches.

Searching for User Objects in Active Directory

Migration Wizard searches the target Active Directory for user objects that match the mailboxes selected for migration. For each security identifier (SID) not found in Active Directory, Migration Wizard creates a disabled user object that corresponds to the account you are migrating.

Most matches are based on Windows SIDs. In both Windows NT 4.0 and Windows 2000, each user account has a SID. In addition, Exchange 5.5 uses the SID to associate mailboxes with Windows NT 4.0 user accounts.

If Migration Wizard finds a user object in Active Directory that matches the mailbox to be migrated, Migration Wizard:

• Connects to the source directory (Exchange Directory or Active Directory).
• Copies attributes from the source user object.
• Merges directory information from the source user object with the user object in the target Active Directory forest.
• Creates a mailbox on the target Exchange 2000 server.
• Connects to the source Exchange 2000 server.
• Copies mailbox content from the source mailbox to the new mailbox on the target Exchange 2000 server.

If you migrate mailboxes to a new Active Directory forest but you keep the user objects in the current domain or forest, Migration Wizard will not find the appropriate SIDs in the target Active Directory. In this case, Migration Wizard:

• Creates a disabled user object in the target Active Directory.
• Copies directory information from the source user object to the disabled user object in the target Active Directory.
• Creates a mailbox on the target Exchange 2000 server.
• Connects to the source Exchange 2000 server.
• Copies mailbox content from the existing mailbox to the new mailbox on the target Exchange 2000 server.
• Gives the source user object rights to access the target Exchange 2000 mailbox.

Important   A trust relationship must exist between the source and target domains to allow the source user object to access its new Exchange 2000 mailbox.

Note   The Windows Account Creation and Association screen in Migration Wizard lists the mail accounts you selected for migration. If an existing user object is located in Active Directory, the existing user object's distinguished name is shown in the Existing Windows Account column. If a disabled user object is created for the mailbox account, the disabled user object's distinguished name is shown in the New Windows Account column.

Searching for Contacts in Active Directory

After searching for user objects, Migration Wizard searches Active Directory for contact objects that match the mailboxes selected for migration. When a match is found, Migration Wizard:

• Reads directory information from the contact.
• Merges the information from the contact's attributes with the attributes for the new user object.
• Deletes the contact object.

The directory information from the contact object is merged with the user object's attributes based on the following rules:

• The target Active Directory is the most recent directory service.
• An attribute will not be overwritten if the target value already exists.
• Source multi-valued attributes are preserved.
• An attribute will not migrate if it is not part of the target schema.

If Migration Wizard does not find any contacts, it considers the search process to be complete (no new objects are created).

For more information about matching, see Selecting Which Accounts to Migrate.