Applies to: Exchange Server 2013
Topic Last Modified: 2013-02-20
Public folders are designed for shared access and provide an easy and effective way to collect, organize, and share information with other people in your workgroup or organization. Public folders help organize content in a deep hierarchy that’s easy to browse. Users will see the full hierarchy in Outlook, which makes it easy for them to browse for the content they’re interested in.
|Public folders are available in the following Outlook clients: Outlook Web App for Exchange 2013, Outlook 2007, Outlook 2010, Outlook 2013, and Outlook for Mac.|
Public folders can also be used as an archiving method for distribution groups. When you mail-enable a public folder and add it as a member of the distribution group, email sent to the group is automatically added to the public folder for later reference.
Public folders aren’t designed for the following purposes:
- Data archiving. Users who have mailbox limits sometimes
use public folders instead of mailboxes to archive data. This
practice isn't recommended because it affects storage in public
folders and undermines the goal of mailbox limits. Instead, we
recommend that you use In-Place Archiving
as your archiving solution.
- Document sharing and collaboration. Public folders don't
provide versioning or other document management features, such as
controlled check-in and check-out functionality and automatic
notifications of content changes. Instead, we recommend that you
use SharePoint as your documentation sharing
To learn more about public folders and other collaboration methods in Exchange 2013, see Collaboration.
To browse some frequently asked questions about public folders in Exchange 2013, see FAQ: Public Folders.
For a list of public folder management tasks, see Public Folder Procedures.
Looking for the Exchange Online version of this topic? See Public Folders in Exchange Online.
Public folder architecture
In Exchange 2013, public folders were re-engineered using mailbox infrastructure to take advantage of the existing high availability and storage technologies of the mailbox database. Public folder architecture uses specially designed mailboxes to store both the public folder hierarchy and the content. This also means that there’s no longer a public folder database. High availability for the public folder mailboxes is provided by a database availability group (DAG). To learn more about DAGs, see Database Availability Groups.
The main architectural components of public folders are the public folder mailboxes, which can reside in one or more mailbox databases.
Public folder mailboxes
There are two types of public folder mailboxes: the primary hierarchy mailbox and secondary hierarchy mailboxes. Both types of mailboxes can contain content:
- Primary hierarchy mailbox The primary
hierarchy mailbox is the one writable copy of the public folder
hierarchy. The public folder hierarchy is copied to all other
public folder mailboxes, but these will be read-only copies.
- Secondary hierarchy mailboxes Secondary
hierarchy mailboxes contain public folder content as well and a
read-only copy of the public folder hierarchy.
There are two ways you can manage public folder mailboxes:
- In the Exchange admin center (EAC), navigate to Public
folders > Public folder mailboxes.
- In the Exchange Management Shell, use the *-Mailbox set
of cmdlets. The following parameters have been added to the
cmdlet to support public folder mailboxes:
- PublicFolder This parameter is used
with the New-Mailbox cmdlet to create a public folder
mailbox. When you create a public folder mailbox, a new mailbox is
created with the mailbox type of
PublicFolder. For more information, see Create a Public Folder Mailbox.
- HoldForMigration This parameter is used
only if you are migrating public folders from a previous version to
Exchange 2013. For more information, see Migrate Public folders from
previous versions later in this topic.
- IsExcludedFromServingHierarchy This
parameter prevents users from accessing the public folder hierarchy
on the specified public folder mailbox. For load-balancing
purposes, users are equally distributed across public folder
mailboxes by default. When this parameter is set on a public folder
mailbox, that mailbox isn't included in this automatic load
balancing and won't be accessed by users to retrieve the public
folder hierarchy. However, if you set the
DefaultPublicFolderMailbox property on a user mailbox to a
specific public folder mailbox, the user will still access the
specified public folder mailbox even if the
IsExcludedFromServingHierarchy parameter is set for that
public folder mailbox.
- PublicFolder This parameter is used with the New-Mailbox cmdlet to create a public folder mailbox. When you create a public folder mailbox, a new mailbox is created with the mailbox type of
Public folder hierarchy
The public folder hierarchy contains the folders’ properties and organizational information, including tree structure. Each public folder mailbox contains a copy of the public folder hierarchy. There’s only one writeable copy of the hierarchy, which is in the primary public folder mailbox. For a specific folder, the hierarchy information is used to identify the following:
- Permissions on the folder
- The folder’s position in the public folder tree, including its
parent and child folders
|The hierarchy doesn’t store information about email addresses for mail-enabled public folders. The email addresses are stored on the directory object in Active Directory.|
The public folder hierarchy synchronization process uses Incremental Change Synchronization (ICS), which provides a mechanism to monitor and synchronize changes to an Exchange store hierarchy or content. The changes include creating, modifying, and deleting folders and messages. When users are connected to and using content mailboxes, synchronization occurs every 15 minutes. If no users are connected to content mailbox, synchronization will be triggered less often (every 24 hours).If a write operation such as a creating a folder is performed on the primary hierarchy, synchronization is triggered immediately (synchronously) to the content mailbox.
|Because there’s only one writeable copy of the hierarchy, folder creation is proxied to the hierarchy mailbox by the content mailbox users are connected to.|
In a large organization, when you create a new public
folder mailbox, the hierarchy needs to synchronize to that public
folder before users can connect to it. Otherwise, users may see an
incomplete public folder structure when connecting with Outlook. To
allow time for this synchronization to occur without users
attempting to connect to the new public folder mailbox, set the
IsExcludedFromServingHierarchy parameter on the
New-Mailbox cmdlet when creating the public folder mailbox.
This parameter prevents users from connecting to the newly created
public folder mailbox. When synchronization is complete, run the
cmdlet with the IsExcludedFromServingHierarchy parameter set
false, indicating that the public folder mailbox is
ready to be connected to. You can use also the Get-PublicFolderMailboxDiagnostics
cmdlet to view the sync status by the SyncInfo and the
For more information, see Create a Public Folder.
Public folder content
Public folder content can include email messages, posts, documents, and eForms. The content is stored in the public folder mailbox but isn’t replicated across multiple public folders mailboxes. All users access the same public folder mailbox for the same set of content. Although a full text search of public folder content is available, public folder content isn’t searchable across public folders and the content isn’t indexed by Exchange Search.
Although there are many advantages to using Exchange 2013 public folders, there are some things to consider before implementing them in your organization:
- It’s very important that you carefully plan you public folder
deployment. Because there’s only one replica of any particular
public folder, planning is critical to avoid severe delays in
accessing the folders. For example, you can plan to separate
heavily used public folders across multiple public folder mailboxes
for load balancing purposes.
- Exchange 2013 no longer supports public folder databases.
Therefore, there’s no coexistence with legacy public folders. As a
result, Exchange 2013 is unable to read from the hierarchy stored
in a public folder database on Exchange 2010 or Exchange 2007
- Outlook Web App is supported, but with limitations. You can add
and remove favorite public folders and perform item-level
operations such as creating, editing, deleting posts, and replying
to posts. However, you can’t create or delete public folders from
Outlook Web App.
- Although a full text search of public folder content is
available, public folder content isn’t searchable across public
folders and the content isn’t indexed by Exchange Search.
- You must use Outlook 2007 or later to access public folders on
Exchange 2013 servers.
- Retention policies aren’t supported for public folder
Migrate public folders from previous versions
If you already have Exchange 2010 SP3 or Exchange 2007 SP3 RU10 public folders in your organization prior to installing Exchange 2013, you must migrate those public folders to Exchange 2013. To do this, use the PublicFolderMigrationRequst cmdlets. For more information, see Migrate Public Folders to Exchange 2013 From Previous Versions.
Due to the changes in how public folders are stored, legacy Exchange mailboxes are unable to access the public folder hierarchy on Exchange 2013 servers. However, user mailboxes on Exchange 2013 servers can connect to legacy public folders. Exchange 2013 public folders and legacy public folders can’t exist in your Exchange organization simultaneously. This effectively means that there’s no coexistence between versions. Migrating public folders to Exchange Server 2013 is currently a one-time cutover process.
For this reason, it’s recommended that prior to migrating your public folders, you should first migrate your legacy mailboxes to Exchange 2013. For more information about migrating mailboxes, see Mailbox Moves in Exchange 2013.
Public folder moves
You can move public folders to a different public
folder mailbox, and you can move public folder mailboxes to
different mailbox databases. To move public folders to different
public folder mailboxes, use the PublicFolderMoveRequest set
of cmdlets. Subfolders under the public folder that’s being moved
won’t be moved by default. If you want to move a branch of public
folders, you can use the
script that’s installed by default with Exchange 2013. For more
information, see Move a Public Folder to
a Different Public Folder Mailbox.
In addition to moving public folders, you can move public folder mailboxes to different mailbox databases by using the MoveRequest set of cmdlets. This is the same set of cmdlets that are used for moving regular mailboxes. For more information, see Move a Public Folder Mailbox to a Different Mailbox Database.
PublicFolderMoveRequest cmdlets and the MoveRequest cmdlets use the Mailbox Replication Service to move public folders asynchronously. That means that the cmdlet doesn’t do the actual work and, during most of the move, the public folder and public folder mailboxes will still be available to users. Because the Mailbox Replication Service performs mailbox moves, import and export requests, and public folder move requests, it’s important to consider throttling and workload management.
Public folder quotas
When created, public folder mailboxes automatically
inherit the size limits of the mailbox database defaults. As a
result, to accurately evaluate the current storage quota status
when using the Get-Mailbox cmdlet,
you must review at the UseDatabaseQuotaDefaults property in
addition to the ProhibitSendQuota,
ProhibitSendReceiveQuota, and IssueWarningQuota
properties. If the UseDatabaseQuotaDefaults property is set
true, the per-mailbox settings are ignored and the
mailbox database limits are used. If this property is set to
true and the ProhibitSendQuota,
ProhibitSendReceiveQuota, and IssueWarningQuota
properties are set to
unlimited, the mailbox size
isn’t really unlimited. Instead, you must use the
Get-MailboxDatabase cmdlet and review the mailbox database
storage limits to find out what the limits for the mailbox are. If
the UseDatabaseQuotaDefaults property is set to
false, the per-mailbox settings are used. In Exchange
2013, the default mailbox database quota limits are as follows:
- Issue warning quota: 1.9 GB
- Prohibit send quota: 2 GB
- Prohibit receive quota: 2.3 GB
To find the mailbox database quotas, run the Get-MailboxDatabase cmdlet.
To set the quotas on a public folder mailbox, use the Set-OrganizationConfig cmdlet.
Exchange 2013 public folders are built on mailbox infrastructure and use the same mechanisms for availability and redundancy. Every public folder mailbox can have multiple redundant copies with automatic failover, just like regular mailboxes. To learn more, see High Availability and Site Resilience.
In addition to the overall disaster recovery scenario, you can also restore public folders in the following situations:
- Soft-deleted public folder restore The
public folder was deleted but is still within the retention
- Soft-deleted public folder mailbox
restore The public folder mailbox was deleted
and is still within the mailbox retention period.
- Public folder mailbox restore from a recovery
database You can recover an individual public
folder mailbox from backup when the deleted mailbox retention
period has elapsed. You then extract data from the restored mailbox
and copy it to a target folder or merge it with another
In all of these situations, the public folder or public folder mailbox is recoverable by using the MailboxRestoreRequest cmdlets.
For more information, see Restore Public Folders and Public Folder Mailboxes from Failed Moves.