When migrating Exchange 5.5 mailboxes, Migration Wizard copies directory and mailbox information from the Exchange 5.5 server on the external domain (source) to the Windows 2000 forest (target). The steps Migration Wizard performs to accomplish these tasks are based on Active Directory searches.
When you create a mailbox in Windows NT 4.0 and Exchange 5.5, you also associate a Windows NT 4.0 user account with a mailbox object in the Exchange directory. A Windows security identifier (SID) is the unique value that is used to make this association. Every user account on a network running Windows NT 4.0 has a SID.
Migration Wizard searches Active Directory for user objects with SIDs matching the SIDs associated with the Exchange 5.5 mailboxes selected for migration. For each SID not found in Active Directory, Migration Wizard creates a disabled user object corresponding to the account you are migrating.
If Migration Wizard finds a user object in Active Directory with a SID matching the account to be migrated, Migration Wizard:
If Migration Wizard does not find a user object in Active Directory with a SID matching the account to be migrated, it is because an account already exists in an external domain or a domain that is either a Windows NT 4.0 domain or a Windows 2000 domain in a separate forest. In this case, Migration Wizard:
Important A trust relationship must exist between the external domain and the Windows 2000 domain in order to allow the external account 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.
After searching for the SID, Migration Wizard searches Active Directory for contact objects with SMTP or X500 proxy addresses matching the mailboxes selected for migration. When a match is found, Migration Wizard:
The directory information from the contact object is merged with the user object's attributes based on the following rules: