The Move Mailbox wizard and the Move-Mailbox cmdlet allow you to move mailboxes in the following scenarios:

• Upgrade   When you upgrade an existing Microsoft Exchange Server 2003 or Exchange 2000 Server organization to Exchange Server 2007, you will move mailboxes from the existing Exchange servers to an Exchange 2007 server that has the Mailbox server role installed. You can perform these moves within a single Exchange forest or across forests.
  
• Load balancing   To balance the server load among existing Exchange 2007, Exchange 2003, and Exchange 2000 servers, you can move mailboxes. For example, you may want to move all mailboxes in which the size is greater than a specified limit.
  
• Realignment   You can move mailboxes to realign based on specific values. For example, you may want to move a mailbox from one database to a database that has a larger mailbox size limit.
  
• Investigating an issue   If you need to investigate an issue with a mailbox, you can move that mailbox to a different server. For example, you can move all mailboxes that have corrupted messages to one server.
  
• Physical location changes   You can move mailboxes to a server that is in a different Active Directory site. For example, if a user moves to a different physical location, you can move that user's mailbox to a server that is in a site nearer to the new location.
  
• Database move   You can move an entire database file to a new location, and then use the Move-Mailbox cmdlet to change the configuration information in Active Directory so that the mailboxes all point to the new location of the database. You can perform this type of database move only within a single forest, not across forests.
  
• Merge mailboxes   You can merge the contents of one mailbox into another mailbox.
  
• Cross-forest move after an acquisition or merger   After an organizational change such as an acquisition or merger, you may have two separate Exchange forests operating together in a cross-forest scenario. Later, you may want to move mailboxes into a single forest. You can use the Move-Mailbox cmdlet to move mailboxes in this scenario. To reduce the amount of time that users cannot access their mailboxes in a cross-forest move, you can use the Move-Mailbox cmdlet with the AllowMerge parameter.
  
• Cross-forest move before a divestiture   Before an organizational change such as a divestiture, you may want to move a group of mailboxes to a separate forest. You can use the Move-Mailbox cmdlet to move mailboxes from the existing forest to a new forest. To reduce the amount of time that users cannot access their mailboxes in a cross-forest move, you can use the Move-Mailbox cmdlet with the AllowMerge parameter.
  
• Separation of administrative roles   A company may want to separate the administration of Microsoft Exchange from the administration of Microsoft Windows accounts. To do this, you can move mailboxes from a single forest into a resource forest scenario. With this scenario, the Microsoft Exchange mailboxes reside in one forest and their associated Windows user accounts reside in a separate forest.
  
• Outsourcing e-mail administration   A company may want to outsource the administration of e-mail and retain the administration of Windows user accounts. To do this, you can move mailboxes from a single forest into a resource forest scenario. With this scenario, the Microsoft Exchange mailboxes reside in one forest and their associated Windows user accounts reside in a separate forest.
  
• Integrating e-mail and user account administration   A company may want to change from a separated or outsourced e-mail administration model to a model in which e-mail and user accounts can be managed from within the same forest. To do this, you can move mailboxes from a resource forest scenario to a single forest. With this scenario, the Microsoft Exchange mailboxes and Windows user accounts reside in the same forest.
  

To move mailboxes from Exchange 2003 or Exchange 2000 directly to Exchange 2007, you can use the Move Mailbox wizard or the Move-Mailbox cmdlet. You cannot use the Exchange System Manager or Active Directory Users and Computers to move mailboxes from Exchange 2003 or Exchange 2000 to Exchange 2007.

You cannot move mailboxes directly from Microsoft Exchange Server version 5.5 to Exchange 2007. To move mailboxes from Exchange Server 5.5 to Exchange 2007, you must first move the mailboxes to either Exchange 2003 or Exchange 2000 servers, and then move the mailboxes to Exchange 2007. For more information about moving mailboxes from Exchange Server 5.5 to Exchange 2000, see Migrating Mailboxes from Microsoft Exchange Server 5.5 to Microsoft Exchange 2000 Server. For more information about moving mailboxes from Exchange Server 5.5 to Exchange 2003, see How to Use Exchange Task Wizard to Move Mailboxes.

If you move a mailbox from Exchange 2003 or Exchange 2000 to Exchange 2007, and the mailbox is part of an e-mail address policy, the e-mail addresses for that mailbox will be automatically updated based on the configuration of the e-mail address policy. If the mailbox had a primary Simple Mail Transfer Protocol (SMTP) address that differs from the e-mail address enforced by the e-mail address policy, that SMTP address will become a secondary SMTP address and the e-mail address generated by the e-mail address policy will become the primary SMTP address. This behavior is different from Exchange 2003 and Exchange 2000. In Exchange 2003 or Exchange 2000, the e-mail address policy is not applied to a mailbox when it is moved. To prevent accidentally changing the primary SMTP address of a mailbox in an Exchange 2007 environment, you must configure the mailbox so that is does not automatically update e-mail addresses based on e-mail address policy. To configure Exchange 2003 or Exchange 2000 mailboxes, in Active Directory Users and Computers, right-click the recipient, and then select Properties. On the E-mail Addresses tab, clear the Automatically update e-mail addresses based on e-mail address policy check box.

If you have a forest with a previous version of Exchange that contains only Windows 2000 Server domain controllers (not Windows Server 2003 domain controllers), you cannot use the Move-Mailbox cmdlet to move mailboxes to an Exchange 2007 forest. The Move-Mailbox cmdlet can communicate with only Windows Server 2003 domain controllers. To move mailboxes you must have at least one Windows Server 2003 domain controller in both the source and the destination forests.

Table 1 lists the supported mailbox moves and the tools to use for each type of move.

Table 1   Supported mailbox move scenarios

Moving mailboxes	To Exchange 2000	To Exchange 2003	To Exchange 2007
From Exchange 2000	Use the Exchange Task Wizard in Exchange 2000 Server.	Use the Exchange Task Wizard in Exchange Server 2003.	Use the Move-Mailbox cmdlet or the Move Mailbox wizard in Exchange 2007
From Exchange 2003	Use the Exchange Task Wizard in Exchange 2003.	Use the Exchange Task Wizard in Exchange 2003.	Use the Move-Mailbox cmdlet or the Move Mailbox wizard in Exchange 2007.
From Exchange 2007	Use the Move-Mailbox cmdlet or the Move Mailbox wizard in Exchange 2007 within the same forest. Note: Moving a mailbox from an Exchange 2007 server in one forest to an Exchange 2000 server in another forest is not supported.	Use the Move-Mailbox cmdlet or the Move Mailbox wizard in Exchange 2007.	Use the Move-Mailbox cmdlet or the Move Mailbox wizard in Exchange 2007.

In addition to the default user mailboxes, you can create shared mailboxes and resource mailboxes in Exchange 2007. A shared mailbox is a mailbox to which multiple users can log on. A resource mailbox is a mailbox that represents a type of resource, such as a conference room or video equipment. Resource mailboxes have additional properties in Active Directory that user mailboxes and shared mailboxes do not have, such as capacity.

Exchange 2003 and Exchange 2000 do not have resource mailboxes. Instead, you must use shared mailboxes to represent resources. If you move a shared mailbox from Exchange 2003 or Exchange 2000 to Exchange 2007, the Move-Mailbox cmdlet creates the mailbox as a shared Exchange 2007 mailbox. After you move the mailbox to Exchange 2007, you can convert it to a resource mailbox. For more information about how to convert a shared mailbox to a resource mailbox, see How to Convert a Mailbox.

After you move a mailbox, a user may experience a long delay when accessing the moved mailbox using Microsoft Outlook Web Access. The delay can last several minutes if the following conditions are true:

• This is the first time the user has accessed the mailbox using Outlook Web Access since the mailbox was moved.
  
• The user's Outlook Web Access view is not sorted by the date messages were received.
  
• The mailbox size is greater than 1 gigabyte (GB).
  

Outlook Web Access uses message tables in the Exchange database to retrieve sorted views of messages. Exchange automatically creates the message table for the view that is sorted by the date messages were received. For any other view, Exchange does not create the message table until a client requests it. When a user who has a large mailbox and who has a view that sorts mail by anything other than the date messages were received uses Outlook Web Access for the first time after a mailbox move, Outlook Web Access requests a message table from Exchange. Building that message table can take several minutes.

Exchange Server 5.5, Exchange 2000 Server, and Exchange Server 2003 maintain single-instance storage of messages. If a message is sent to one recipient, and if the message is copied to 20 other recipients who reside in the same mailbox store, Exchange maintains only one copy of the message in its database. Exchange then creates pointers that link both the original recipient and the 20 additional recipients to the original message. If the original recipient and the 20 additional recipients are moved to another mailbox store, only one copy of the message is maintained in the new mailbox store. 

The new mailbox store can be on another server in the same site or in an administrative group. If the server is in another site, single-instance storage is retained only if you use the Move Mailbox Wizard in Exchange Server 2003 Service Pack 1 (SP1) or later versions. The Move Mailbox wizard includes a Cross Administrative Group Move feature that lets you move mailboxes across administrative groups.

For earlier versions of Exchange, you had to use the ExMerge toolUsing ExMerge causes the loss of single-instance storage. For information about ExMerge, see the Microsoft Knowledge Base article 174197, Microsoft Exchange Mailbox Merge program (Exmerge.exe) information.

For example, assume the following configuration:

Server 1 Mailbox Store 1: Users A, B, and CServer 2 Mailbox Store 1: User D

When User A sends the same message to User B, User C, and User D, a single instance of the message is created on server 1 for all three users, because they are on the same server. Even the message that is in User A's Sent Items folder is a single instance of the message that is in the Inboxes of User B and User C. Because User D is on a different server, a message is sent to server 2 that will be stored on that server.

Note:
If a message is sent to a user who is on the same server but on a different mailbox store than the sender, that mailbox store will also contain the message.

During a move of users, each incoming message is checked against its internally assigned IDs, which cannot be viewed with a client. If Exchange determines that the incoming message is a duplicate, a pointer is set up for that existing message that points to the newly moved user. Assume that User B is moved to server 2. A single instance of the message will be created for User B based on the copy of the message that User D has. This is true if user D has not deleted the message. If User D has already deleted the message, a single instance of the message will be created based on the copy of the message that is in User D's Deleted Items folder. If User D also deleted the message copy in the Deleted Items folder, a new message is created and sent to server 2.

The same process occurs if User B and User C are moved to server 2. Exchange will maintain a single instance of the message for User B and User C. This is based on the message that is in the Inbox of User D. If User D has already deleted the message, a single instance of the message is created based on the message that is in User D's Deleted Items folder. If User D has already emptied the Deleted Items folder, a new message is created and sent to server 2.

For more information about how to move a mailbox within a single Microsoft Exchange forest, see How to Move a Mailbox Within a Single Forest.

For more information about how to move a mailbox across different Microsoft Exchange forests, see How to Move a Mailbox Across Forests.

For more information about how to merge mailboxes, see How to Merge Mailboxes.

For information about managing Autodiscovery, see Managing the Autodiscover Service.