Earlier versions of Exchange were integrated with the Windows NT security model, but rich directory information was contained in a separate database (Dir.edb). Exchange 2000 is the first release of Exchange relying completely on Active Directory. For coexistence, you can copy a set of mail account attributes between Dir.edb (on Exchange 5.5) and Active Directory. Active Directory Connector (ADC) coordinates replication.
You can migrate Exchange 5.5 mailboxes without using Active Directory Connector and connection agreements. Active Directory Connector is required only when:
Coexistence during migration is a viable solution when you want to ensure that users in Exchange 5.5 and Exchange 2000 organizations can exchange mail during the migration process.
When you connect Exchange 2000 and Exchange 5.5, the two systems coexist. However, message transfer and directory synchronization must occur during the coexistence period. You can use an SMTP connector for message transfer. For directory synchronization, you can use Active Directory Connector.
If you use Active Directory Connector when you migrate Exchange 5.5 mailboxes, adhere to the following guidelines:
Although inter-organizational connection agreements can only be configured to replicate in one direction, you can achieve coexistence by configuring two one-way inter-organizational connection agreements between the Exchange 5.5 server and Active Directory. Setting up two one-way ADC inter-organizational connection agreements that point in opposite directions enables the inter-organizational ADC to replicate the Exchange 5.5 directory information to Active Directory, and to stamp replicated objects with the X500 address of the Exchange 5.5 mailbox.
Note When you establish two one-way inter-organizational connection agreements, ensure that the target container of one connection agreement is not the source container of the second connection agreement.
Important If you use the inter-organizational Active Directory Connector for directory synchronization during coexistence, do so only during the migration process.
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