Outlook uses .pst files to store data locally on users' computers or network shares. Unlike offline store (.ost) files (which are used by Outlook in Cached Exchange Mode to store a copy of the mailbox for offline access), .pst files aren't synchronized with the user's Exchange mailbox. If a user moves messages to a .pst file, those messages are removed from the mailbox.

Using .pst files to manage messaging data can result in the following issues:

• Unmanaged files   Generally, .pst files are created by users and reside on their computers or network shares. They aren't managed by your organization. As a result, users can create several .pst files containing the same or different messages and store them in different locations, with no organizational control.
  
  
• Increased discovery costs   Lawsuits and some business or regulatory requirements sometimes result in discovery requests. Locating messaging data that resides in .pst files on users' computers can be a costly manual effort. Because tracking unmanaged .pst files can be difficult, .pst data may be undiscoverable in many cases. This could possibly expose your organization to legal and financial risks.
  
  
• Inability to apply messaging retention policies   Messaging retention policies can't be applied to messages located in .pst files. As a result, depending on business or applicable regulations, your organization may not be in compliance.
  
  
• Risk of data theft   Messaging data stored in .pst files is vulnerable to data theft. For example, .pst files are often stored in portable devices such as laptops, removable hard drives, and portable media such as USB drives, CDs, and DVDs.
  
  
• Fragmented view of messaging data   Users who store information in .pst files don't get a uniform view of their data. Messages stored in .pst files are generally available only on the computer where the .pst file resides. As a result, if users access their mailboxes using Outlook Web App or Outlook on another computer, the messages stored in their .pst files are inaccessible.
  
  

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In Microsoft Exchange Server 2010, personal archives provide users an alternative storage location in which to store historical messaging data. A personal archive is an additional mailbox (called an archive mailbox) enabled for a mailbox user. Outlook 2010, Outlook 2007, and Outlook Web App users have seamless access to their archive mailbox. Using either of these client applications, users can view an archive mailbox and move or copy messages between their primary mailbox and the archive. Personal archives present a consistent view of messaging data to users and eliminate the user overhead required to manage .pst files. Eliminating the use of .pst files significantly reduces your organization's exposure to the risks outlined in the previous section.

In Exchange 2010 Service Pack 1 (SP1), you can provision a user's personal archive on the same mailbox database as the user's primary mailbox, another mailbox database on the same Mailbox server, or a mailbox database on another Mailbox server in the same Active Directory site. This provides flexibility to use tiered storage architecture and to store archive mailboxes on a different storage subsystem, such as near-line storage. In cross-premises Exchange 2010 deployments, you can also provision a cloud-based archive for mailboxes located on your on-premises Mailbox servers.

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The following table lists the client applications that can be used to access archive mailboxes.

Client access to archive mailboxes

Client	Access to archive mailbox
Outlook 2010, Outlook 2007, and Outlook Web App	Yes. Outlook 2010, Outlook 2007 and Outlook Web App users can copy or move items from their primary mailbox to their archive mailbox, and can also use retention policies to move items to the archive. Note: Outlook 2010 and Outlook 2007 users can also copy or move items from .pst files to their archive mailbox. Outlook 2007 users require the Office 2007 Cumulative Update for February 2011. Some differences in archive support exist between Outlook 2010 and Outlook 2007. For more information, see Exchange Team Blog article, see Yes Virginia, there is Exchange 2010 archive support in Outlook 2007.
Outlook 2003 and older clients	No.
Microsoft Exchange ActiveSync	No.

Note:
Personal archives are a premium feature and require an Exchange Enterprise client access license (CAL). For details about how to license Exchange, see Exchange Server Licensing. For details about the versions of Microsoft Outlook required to access an archive mailbox, see License requirements for Personal Archive and retention policies.

Outlook doesn't create a local copy of the archive mailbox on a user's computer, even if it's configured to use Cached Exchange Mode. Users can access an archive mailbox in online mode only.

Delegate Access

There are several ways to move messages to archive mailboxes:

• Move or copy messages manually   Mailbox users can manually move or copy messages from their primary mailbox or a .pst file to their archive mailbox. The archive mailbox appears as another mailbox or .pst file in Outlook and Outlook Web App.
  
  
• Move or copy messages using Inbox rules   Mailbox users can create Inbox rules in Outlook or Outlook Web App to automatically move messages to a folder in their archive mailbox. To learn more, see Learn About Inbox Rules.
  
  
• Move messages using retention policies   You can use retention policies to automatically move messages to the archive. Users can also apply a personal tag to move messages to the archive. For details about archive and retention policies, see Archive and Retention Policies later in this topic.
  
  

  Note:
  Personal tags are available only in Outlook 2010 and Outlook Web App.

• Import messages from .pst files   In Exchange 2010 SP1, you can use a mailbox import request to import messages from a .pst file to a user's archive or primary mailbox. For details, see Understanding Mailbox Import and Export Requests. Tools used to locate .pst files within an organization are available from Microsoft partners. For a list of Microsoft partners for archiving, see "Archive and Compliance Partners" in Independent Software Vendors.
  
  

Archive and Retention Policies

In Exchange 2010, you can apply archive policies to a mailbox to automatically move messages from a user's primary mailbox to the archive mailbox after a specified period. Archive policies are implemented by creating retention tags that use the Move to Archive retention action.

Messages are moved to a folder in the archive mailbox that has the same name as the source folder in the primary mailbox. If a folder with the same name doesn't exist in the archive mailbox, it is created when the Managed Folder Assistant moves a message. Re-creating the same folder hierarchy in the archive mailbox allows users to find messages easily.

To learn more about retention policies, retention tags, and the Move to Archive retention action, see Understanding Retention Tags and Retention Policies.

Important:
You can't apply a managed folder mailbox policy to mailboxes that have a personal archive. Managed content settings created for managed folders can't use the Move to archive action. To learn more about managed folders, see Understanding Managed Folders.

Default Archive and Retention Policy

Exchange Setup creates the default archive and retention policy Default Archive and Retention Policy. This policy contains retention tags that have the Move to Archive action, as shown in the following table.

Default archive and retention policy

Retention tag name	Tag type	Description
Default 2 year move to archive	Default	Messages are automatically moved to the archive mailbox after two years. Applies to items in the entire mailbox that don't have a retention tag applied explicitly or inherited from the folder.
Personal 1 year move to archive	Personal	Messages are automatically moved to the archive mailbox after one year.
Personal 5 year move to archive	Personal	Messages are automatically moved to the archive mailbox after five years.
Personal never move to archive	Personal	Messages are never moved to the archive mailbox.
Recoverable Items 14 days move to archive	Personal	Messages are moved from the Recoverable Items folder of the user's primary mailbox to the Recoverable Items folder of the archive mailbox. Users attempting to recover deleted items in the archive must use the Recover Deleted Items feature on the archive mailbox.

If you enable a personal archive for a mailbox user and the mailbox doesn't already have a retention policy assigned, the default archive and retention policy is automatically assigned. After the Managed Folder Assistant processes the mailbox, these tags become available to the user, who can then tag folders or messages to be moved to the archive mailbox. By default, e-mail messages from the entire mailbox are moved after two years.

Before provisioning archive mailboxes for your users, we recommend that you inform them about the archive policies that will be applied to their mailbox and provide subsequent training or documentation to meet their needs. This should include details about the following:

• Functionality available within the archive, the default archive and retention policies.
  
  
• Information about when messages may be moved automatically to the archive.
  
  
• Information about the folder hierarchy created in the archive mailbox.
  
  
• How to apply personal tags (displayed in the Archive policy menu in Outlook and Outlook Web App).
  
  

Note:

If you apply a retention policy to users who have an archive mailbox, the retention policy replaces the default archive and retention policy. You can create one or more retention tags with the Move to Archive action, and then link the tags to the retention policy. You can also add the default Move to Archive tags (which are created by Setup and linked to the Default Archive and Retention Policy) to any retention policies you create.

In Exchange 2010 SP1, the default archive and retention policy contains additional retention tags with the Delete and Allow Recovery action. To learn more, see Understanding Retention Tags and Retention Policies.

For information about compliance and archiving in Outlook 2010, see Plan for compliance and archiving in Outlook 2010.

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Archive mailboxes are designed so that users can store historical messaging data outside their primary mailbox. Often, users use .pst files due to low mailbox storage quotas and the restrictions imposed when these quotas are exceeded. For example, users can be prevented from sending messages when their mailbox size exceeds the Prohibit send quota. Similarly, users can be prevented from sending and receiving messages when their mailbox size exceeds the Prohibit send and receive quota.

To eliminate the need for .pst files, you can provide an archive mailbox with storage limits that meet the user's requirements. However, you may still want to retain some control of the storage quotas and growth of archive mailboxes to help monitor costs and expansion.

To help with this control, you can configure archive mailboxes with an archive warning quota and an archive quota. When an archive mailbox exceeds the specified archive warning quota, a warning event is logged in the Application event log. When an archive mailbox exceeds the specified archive quota, messages are no longer moved to the archive, a warning event is logged in the Application event log, and a quota message is sent to the mailbox user. By default, in Exchange 2010 SP1, the archive warning quota is set to 45 gigabytes (GB) and the archive quota is set to 50 GB. In Exchange 2010 release to manufacturing (RTM), both quotas are set to Unlimited.

The following table lists the events logged and warning messages sent when the archive warning quota and archive quota are met.

Archive quota alerts

For details about how to configure archive quotas, see Configure Archive Quotas for a Personal (On-Premises) Archive.

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This section explains the functionality between personal archives and various Exchange features:

• Exchange Search   The ability to quickly search messages becomes even more critical with archive mailboxes. For Exchange Search, there's no difference between the primary and archive mailbox. Content in both mailboxes is indexed. Because the archive mailbox isn't cached on a user's computer (even when using Outlook in Cached Exchange Mode), search results for the archive are always provided by Exchange Search. When searching the entire mailbox in Outlook 2010, search results include the users' primary and archive mailbox.
  
  To learn more about Exchange Search, see Understanding Exchange Search.
  
  
• Multi-Mailbox Search   When a discovery manager uses Multi-Mailbox Search to perform a discovery search, users' archive mailboxes are also searched. There's no option to exclude archive mailboxes when creating a discovery search from the Exchange Control Panel (ECP). When using the Exchange Management Shell to create a discovery search, you can exclude the archive by using the DoNotIncludeArchive switch. For details, see New-MailboxSearch.
  
  

  Note:
  You can't use Multi-Mailbox Search to search a disconnected mailbox.

  To learn more about Multi-Mailbox Search, see Understanding Multi-Mailbox Search.
  
  
• Litigation hold   When you put a mailbox on litigation hold, the hold is placed on both the primary and the archive mailbox. To learn more about litigation hold, see Understanding Litigation Hold.
  
  
• Recoverable Items folder   The archive mailbox contains its own Recoverable Items folder, and is subject to the same Recoverable Items folder quotas as the primary mailbox. To learn more about recoverable items, see Understanding Recoverable Items.
  
  

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In Exchange 2010, creating and managing archive mailboxes is integrated with common mailbox management tasks, such as the following:

• Creating an archive mailbox   You can create an archive mailbox when creating a mailbox, or you can enable an archive mailbox for an existing mailbox. For details, see Create a Personal (On-Premises) or Cloud-Based Archive for a New Mailbox and Enable a Personal (On-Premises) or Cloud-Based Archive for an Existing Mailbox.
  
  
• Moving an archive mailbox   You can move a user's archive mailbox to another mailbox database on the same Mailbox server or to another server. In Exchange 2010 SP1, you can move a user's archive mailbox independent of the primary mailbox. In Exchange 2010 RTM, a user's archive mailbox resides on the same Mailbox server as the primary mailbox. To move a user's archive mailbox, you must create a mailbox move request. For details, see Create a Local Move Request.
  
  
• Disabling an archive mailbox   You may want to disable a user's archive mailbox for troubleshooting purposes or if you're moving the primary mailbox to a version of Exchange that doesn't support personal archives. Disabling an archive is similar to disabling a primary mailbox. For details, see Disable a Personal (On-Premises) or Cloud-Based Archive for a Mailbox. A disabled archive mailbox is retained in the mailbox database until the deleted mailbox retention period for that database is reached. During this period, you can reconnect the archive to a mailbox user. When the deleted mailbox retention period is reached, the disconnected archive mailbox is purged from the mailbox database.
  
  
• Retrieving mailbox statistics and folder statistics   You can retrieve mailbox statistics and mailbox folder statistics for a user's archive mailbox by using the Archive switch with the Get-MailboxStatistics and Get-MailboxFolderStatistics cmdlets.
  
  

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