Configuring Public Folder Referrals
In a large organization with multiple public folder replicas in multiple locations, you need to consider how clients access public
folder data. By default, when a user accesses a public folder using
Outlook or another client, his or her default public folder database
determines which public folder replica the client should access. If the
content exists on the Exchange server that handles the client request,
the client accesses the local replica. Otherwise, Exchange redirects
the client through a referral process to another public folder database
that has a copy of the requested content.
The request and referral process works like this:
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Outlook requests content in a public folder. If the content exists
in the user's default public folder database, Exchange connects Outlook
to that replica and Outlook retrieves the content. Otherwise, Exchange
returns a replica list to Outlook sorted by relative priority.
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Outlook attempts to access each replica in the list, starting with
the replica with the highest relative priority. If that replica
contains the desired content, Outlook retrieves the content. Otherwise,
Outlook continues through the replica list until it has tried to access
all replicas in the list. If Outlook fails to find a replica with the
requested content, it displays an error to the user.
By default, Exchange and Outlook use the infrastructure provided by
Active Directory to determine relative priority of replicas. In Active
Directory, you use subnets to represent the physical structures of a
network. Links between sites, referred to as site links,
have an associated cost, which sets the relative priority of the link.
Active Directory uses this relative priority to route requests and data
across site links. Typically, the site link or set of site links with
the lowest cost is used.
Note
A good resource for learning more about site-based routing is Windows Server 2008 Inside Out
(Microsoft Press, 2008). See Chapter 32, "Configuring Active Directory
Sites and Replication," and Chapter 37, "Active Directory Site
Administration."
Ideally, if you are having problems with replica referrals,
you should work with a Windows administrator to resolve the problem.
Explain the problems you are seeing—or that users are experiencing—to
help the administrator resolve the problem by better optimizing the way
site links are used. Keep in mind that site link costs primarily are
used for routing Active Directory replication traffic and
communications, and it might not be possible to make changes to improve
performance for public folder referrals.
Note
In mixed environments where you have exchange Server 2010 and
supported earlier releases of exchange, Microsoft recommends assigning
users a default public folder database on a server running exchange
Server 2010. When a client is referred to a server running exchange
2003 Server, exchange and Outlook manage public folder referrals using
routing group connectors and the related configuration settings.
An alternative to using Active Directory site link costs is to create a custom
list that assigns a server referral cost. However, Microsoft recommends
using a custom list of referrals only in a limited number of
situations, such as when you have specific requirements that cannot be
resolved using Active Directory site link costs.
When you create a custom list of referrals, you set the referral
cost of each server with a public folder database. The referral cost is
a value between 1 and 100. The server with the lowest referral cost is
first on the referral list, the server with the second lowest referral
cost is listed second on the referral list, and so on. Because each
public folder database has its own custom list, the user's default
public folder database settings determine which custom list of
referrals is used. It is important to note that even if you set the
maximum referral value of 100, the server may still be used for
referrals.
To view and manage the public folder referral configuration of a particular public folder database, follow these steps:
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In the Exchange Management Console, right-click the public folder database, and then select Properties.
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In the Properties dialog box, on the Public Folder Referral tab,
you'll see the current referral configuration and any custom list that
has been created (if applicable).
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If you want the database to use Active Directory site link costs for
referrals, accept the default selection of Use Active Directory Site
Costs and then click OK.
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If you want the database to use a custom list for referrals, select
Use Custom List and then add referral servers to the list by clicking
Add, specifying a referral server, assigning a referral cost, and then
clicking OK.
You can configure custom referrals using the Set-PublicFolderDatabase cmdlet in the Exchange Management Shell. Example 4 provides the syntax and usage. When you set –UseCustomReferralServerList to $false, Exchange stops using and clears out the custom referral lists.
Example 4. Using Set-PublicFolderDatabase to configure custom referrals
Syntax
Set-PublicFolderDatabase -Identity PublicFolderDatabaseIdentity
[-UseCustomReferralServerList <$true | $false>]
[-CustomReferralServerList ServerA:Cost, ServerB:Cost, ...]
Usage for enabling custom referrals
Set-PublicFolderDatabase
-Identity "CORPSVR127\Fourth Storage Group\Public DB"
-UseCustomReferralServerList $true
-CustomReferralServerList "MailServer27:10","MailServer72:20"
Usage for disabling custom referrals
Set-PublicFolderDatabase
-Identity "CORPSVR127\Fourth Storage Group\Public DB"
-UseCustomReferralServerList $false
Recovering Deleted Items from Public Folder Databases
You can recover deleted items from public folder databases without
restoring from backup as long as you've set a deleted item retention
period for the public folder database from which the items were deleted
and the retention period for this database hasn't expired. If both of
these conditions are met, you can recover deleted items by completing
the following steps:
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Log on to the domain using either an account with administrative
privileges in the domain or an account with full control over the
public folder from which you need to recover items.
Tip
Outlook displays public folders only when you fully expand the
folder list in the left pane. In Outlook 2007 and later, you'll find a
Folder List button in the lower right corner of the left pane. Click
this button to expand the folder list. You also can press Ctrl+6 to
display the expanded folder list in Outlook 2010.
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After starting Outlook, access the Public Folders node, and then
select the public folder from which you need to recover an item.
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On the Tools menu or on the Folder pane, select Recover Deleted Items. The Recover Deleted Items From dialog box appears.
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Select the items you want to recover, and then click the Recover Selected Items button.
