When they were first introduced, public folders were the cornerstone
of the Microsoft collaboration strategy for Exchange. Many of the
features public folders provide are very interesting, among which are
support for electronic forms and the ability to replicate data to
multiple replicas so that data would be close (in network terms) to end
users. Time and technology have left public folders in their
slipstream, and the features that seemed so attractive in the past are
now relics of the way we used to work.
Even so, a great deal of
public folders remain in use. For the most part, these public folders
act as read-only repositories for documents that large numbers of users
need to access, such as company policies and procedures, project
documentation, and so on. Other solutions exist for such needs, but up
to now, none has been able to offer the tight integration that exists
between Microsoft Outlook and public folders. Compare the ease with
which someone can publish a document in a public folder by dragging and
dropping it from his personal folders (online or in a PST) to the
gyrations that are often necessary to publish on a website. Given that
so many people regard Outlook as their work hub, it’s not surprising
that public folders still remain in use. The advent of site mailboxes
might force companies to reassess public folders but only if they can
afford to deploy Outlook 2013 and Microsoft SharePoint 2013, both of
which are prerequisites for successful deployment of site mailboxes.
Public folders are, after all, free because they are included in the
Exchange base functionality. Modernizing part of their base
functionality to bring public folders back into the Exchange
mainstream, including making them available for the first time to
Exchange Online, makes a lot of sense.
Modernization means that Exchange 2013 public folders are:
Managed through the Exchange Administration Center (EAC).
Stored in mailbox databases rather than in separate public folder databases.
Protected
by native high availability in Exchange rather than by using a
completely different (and not always well-understood) replication
mechanism.
Older public folders can still be
present inside an Exchange 2013 organization, but only if they are
already in use when an organization upgrades from Exchange 2010 or
Exchange 2007.The transformation of earlier public
folders into the newer, mailbox-based variety takes a lot of planning
and work. You cannot deploy the old-style public folders in a new
Exchange 2013 organization in which public folders have never been used
before. In addition, you cannot manage the old-style public folders
through Exchange Administration Center (EAC). Instead, you use the
separate Microsoft Management Console (MMC)–based public folder
management console available in the Exchange toolbox or Exchange
Management Shell (EMS).
Older public folders are organized in a hierarchy that is
split into system public folders and user-visible public folders.
Although some system public folders remain in Exchange 2013 to support
features such as the recovery of deleted public folders, modern system
folders do not store user-accessible data such as the Offline Address
Book (OAB) and Free/Busy information. The basic principles for the new
architecture are as follows:
Public
folders are stored in public folder mailboxes in regular mailbox
databases. Think of public folder mailboxes as containers for public
folders similar to the way databases are containers for mailboxes and
user mailboxes are containers for folders.
A
public folder hierarchy still exists, but only a single writeable copy
of the hierarchy is maintained for the entire organization. The
writeable copy of the hierarchy is stored in the first public folder
mailbox created within the organization. You cannot change the mailbox
that holds the writeable copy of the hierarchy.
The
public folder hierarchy is held as a set of items in the public folder
mailbox. Each item is just a few kilobytes in size, meaning that even
the hierarchy can be safely accommodated by a public folder mailbox.
After
the first public folder mailbox is created, all subsequent public
folder mailboxes hold a read-only copy of the hierarchy. These copies
are secondary to the primary, writeable copy and are updated by
reference to the primary copy.
Clients
connect to their home hierarchy on their home site. The Client Access
Server (CAS) is responsible for routing client connections to the
correct home hierarchy.
In
addition to the folder hierarchy, public folder mailboxes also hold
folder content. No replicas exist, and clients always connect to the
single copy of content. Replication clashes caused by edits being
applied to an item in multiple replicas as seen in the older
implementation do not occur in the new public folders.
Public
folders are protected just as user mailboxes are by creating multiple
copies of the databases that host public folder mailboxes in a Database
Availability Group (DAG).
Because other
collaborative solutions existed, organizations that began using
Exchange in the recent past might not use public folders at all. Those
that do can migrate their current public folder infrastructure to the
new equivalent in a one-time migration operation. You cannot run
old-style public folders alongside their modern equivalents. Migration
is intended to be a one-time operation that moves the public folder
hierarchy, content, and electronic forms over to populate a new set of
public folder mailboxes and then switches client connections over to
use the new public folder mailboxes.
Users whose mailboxes are on
Exchange 2007 or Exchange 2010 servers cannot access modern public
folders. You must migrate user mailboxes to Exchange 2013 before
attempting to switch public folder implementations. To facilitate
preparation, users whose mailboxes have been moved to Exchange 2013 can
access public folders on Exchange 2007 or Exchange 2010 servers.
2. Creating public folder mailboxes
Assuming that you do not migrate data from old-style public
folders and want to use public folders with Exchange 2013, you must
create one or more public folder mailboxes and then build out the
hierarchy with some new public folders. The first step is to create a
public folder mailbox. Open the Public Folders section of EAC, choose
Public Folder Mailboxes, and then click Create (Figure 1).
Because this is the first public folder mailbox in the organization, it
will hold the primary or writeable copy of the hierarchy.
Remember
that you cannot change the mailbox that holds the primary copy of the
hierarchy. Therefore, it is important for this mailbox to be protected
by being placed in a database within a DAG that has multiple copies,
mostly because if the mailbox holding the primary copy of the hierarchy
is offline for any reason, users will not be able to post new items to
public folders in that mailbox or create new public folders,
administrators might not be able to perform some operations against
public folders, and the synchronization of the public folder hierarchy
to other mailboxes cannot occur. Users will still have view-only access
to public folders stored in other mailboxes.
It is a good idea to
follow a naming convention for public folder mailboxes so that the
right mailbox can be located easily. For instance, you might decide to
create public folder mailboxes on a departmental or geographical basis
so that all the folders belonging to a particular department are held
in a specific folder mailbox or to distribute the public folder load on
a site basis. In this case, create a suitable folder to act as the base
of your deployment and put it into a database that you know is part of
a DAG so that the hierarchy is protected from the start.
Behind
the scenes, Exchange creates a mailbox that is marked to be used for
public folders and copies the public folder hierarchy to the new
mailbox. All the properties you’d expect for a mailbox are present and
can be managed with the Set-Mailbox command. Public folder mailboxes
are hidden from address lists and have a disabled Microsoft Windows
account. Although they have an email address, you cannot send messages
to the mailboxes by using the address because public folder mailboxes
are intended to store folders rather than content, so Exchange will
reject the messages. To see the set of known public folder mailboxes
with EMS, use the following command:
Get-Mailbox –PublicFolder
Note that RecipientTypeDetail is PublicFolderMailbox.
Follow the same process to create as many public folder mailboxes as you think you’ll need (Figure 2).
You can add public folder mailboxes as you need them, but some thought
should be given to how to distribute public folders across mailboxes so
that they are stored and accessed most effectively.
To
see a list of the public folders that are held in a particular public
folder mailbox, run the Get-PublicFolder cmdlet and specify the ResidentFolders
parameter together with the name of the mailbox that you want to
examine, For instance, this command generates a list of all the folders
in the PFMBX1 public folder mailbox. Note the use of the Recurse parameter to request Exchange to return details of child folders.
Get-PublicFolder –Mailbox 'PFMBX1' -ResidentFolders -Recurse
