Exchange Server 2003 Service Pack 1 (SP1) introduces new site-consolidation functionality that uses the Move Mailbox Wizard to move (or migrate) mailboxes between Exchange servers that are located on different sites or administrative group/routing group pairs while the Exchange organization is in mixed mode. Although this functionality is new, Exchange 2003 and Exchange 2000 Server support mailbox moves between servers in different administrative groups if the Exchange organization is in native mode.
This site-consolidation feature might seem like a minor enhancement, albeit of great use and importance during consolidation and migration exercises, but don't underestimate its complexity. Let's look at the prerequisites, processes, and behind-the-scenes activity associated with cross-administrative group mailbox moves. In the interests of brevity, I'll deal exclusively with mailbox migrations and their effect on distribution lists (DLs) in cross- administrative group scenarios. In a future article, I'll discuss the considerations for moving DLs, Contacts, and Outlook client profiles.
Mailbox-Move Requirements
Before you can perform cross-administrative group mailbox migrations, you need to perform several steps, either manually or by following the guidelines defined in the new Exchange 2003 SP1 Exchange Server Deployment Tools (ExDeploy), which Figure 1 shows. (You can download the most recent version of ExDeploy from http://www.microsoft.com/exchange/downloads/2003.asp, or you can find the tools on the Exchange 2003 CD-ROM.) ExDeploy is a set of compiled Help files that guides you through the Exchange 2003 installation and migration process. First, you need to deploy at least one Exchange 2003 server in the organization, which you can do by using the Deploy the first Exchange 2003 server ExDeploy option. You need to deploy this Exchange 2003 server before you select the Consolidate Sites in Exchange Mixed Mode ExDeploy option.
When you move Exchange Server 5.5 mailboxes across administrative group boundaries, the target server must be running Exchange 2003 SP1 because other versions of Exchange don't support this scenario. However, other Exchange versions can exist in the target administrative group as long as you don't try to move mailboxes onto those servers. You can relocate mailboxes from the target Exchange 2003 SP1 server to any other server in the same administrative group at a later time. You don't need specific Exchange versions later than Exchange 5.5 SP3 in the source administrative groups.
You also need to upgrade Exchange 2003 Active Directory Connector (ADC) servers to use the ADC that ships with Exchange 2003 SP1 before attempting any cross-administrative group mailbox moves. If you don't, the Microsoft Management Console (MMC) Exchange System Manager (ESM) snap-in prevents any such moves. I discuss this particular requirement in more detail later.
As with any migration, two-way connection agreements (CAs) must exist for every Exchange 5.5 site; this requirement is especially important for cross-administrative group mailbox moves. After you move a mailbox between administrative groups, the ADC performs cleanup processing to adjust the DL contents and old stub (hidden) mailboxes. Stub mailboxes are retained in the source administrative group until you purge all references to them throughout the organization. I'll discuss this cleanup process in more detail later.
If your Exchange organization is in mixed mode but you don't have any Exchange 5.5 servers in the organization, any attempt to perform a cross-administrative group mailbox move will fail and you'll be instructed to switch your Exchange organization to native mode to perform a more conventional mailbox move. Native-mode moves are more straightforward than mixed-mode moves because problems with the legacyExchangeDN attribute don't arise in native-mode moves.
You need to apply a hotfix for the Directory Service/Information Store (DS/IS) consistency adjuster on all Exchange 5.5 public folder servers in the Exchange organization before you can migrate mailboxes or DLs between administrative groups. The hotfix is required because ACLs on a public folder can become invalid following a cross-administrative group mailbox-move operation since the distinguished name (DN) associated with the mailbox changes during such a move. If the hotfix isn't applied, the DS/IS consistency adjuster removes entries in the ACL that don't correspond to a valid mailbox. However, after the hotfix is applied, the DS/IS consistency adjuster also checks the X.500 proxy addresses of objects in the Exchange 5.5 DS for a match, which maintains the integrity of the ACL because a cross-administrative group mailbox move adds an X.500 proxy that matches the previous DN of the Exchange 5.5 object. (For more information about this hotfix, see the Microsoft article "An update is required for mixed-mode site consolidation with Exchange Server 5.5" at http://support.microsoft.com/?kbid=836489.)
After you install the hotfix, wait a few minutes so that replication can occur before you try to move any mailboxes. I tried to perform a cross-administrative group mailbox move immediately after installing the hotfix, and I received the error message that Figure 2 shows. As a best practice, apply the hotfix several days in advance of your first planned cross- administrative group mailbox move, especially for Exchange organizations that are distributed across a wide area.