The Offline Address Book (Part 1)

If you would like to read the first part of this article series please go to:


When Outlook users are running in cached mode or otherwise disconnected from t heir Exchange infrastructure, they rely on the Offline Address Book (OAB) to provide them with access to one or more address lists that are always available when they are connected directly to Exchange. Since a large majority of deployments now use Outlook in cached mode, correct access to the OAB is a key feature of those Exchange deployments.

Due to the way that the OAB rebuild and download schedules are configured by default, it is quite possible that a user may query why a new user is not available in the address book, or perhaps why a modified user (such as after a name change) still has the old details showing despite the configuration change having taken place. Such issues can occur without taking into consideration any errors that may be present within the OAB rebuild process.

Historically, the OAB has been distributed to Outlook clients via the public folder feature of Exchange. Specifically, a system public folder is used with replicas of this public folder spread throughout the Exchange infrastructure for resilience. This is the method supported by Outlook 2003 and earlier versions of the Outlook client. Prior to the release of Exchange 2007, Microsoft announced that it was effectively de-emphasizing the role of public folders and therefore needed a way to distribute the OAB without using system public folders. As a result, the web-based distribution model was designed and can be used when Outlook 2007 or Outlook 2010 is deployed to your users. The web-based distribution method makes much more efficient use of bandwidth and additionally it is possible to control the locations where users can download the OAB. Having said this, it is still perfectly valid to have both the public folder and web-based distribution methods used to distribute your OAB.

In this article we’ll be taking a look at how the OAB is generated and downloaded to the Outlook clients, allowing you to understand the overall process and at the same time giving you the ability to examine the various components of the system when you are troubleshooting issues. We’ll be focusing on the web-based distribution method since the public folder distribution method has been around for a long time and is documented in many different articles available on the Internet.

Generation Server

It’s the Microsoft Exchange System Attendant service running on the mailbox server role that first produces the OAB data. The specific mailbox server that produces the initial data depends on which server has been configured to generate the OAB. This can be determined by examining the properties of the Offline Address Book object in the Exchange Management Console. To do this, navigate to the Organization Configuration node and then select the Mailbox node underneath. Once the Mailbox node has been selected, click the Offline Address Book tab and you should be presented with a screen similar to the one shown in Figure 1. In Figure 1 you can clearly see that in this particular example there is a single OAB called Default Offline Address Book; this is the default OAB created when Exchange 2010 is first installed. You can also see that the mailbox server responsible for generating this OAB is called LABMBX.

Figure 1: Offline Address Book Object

Offline Address Book Properties

Before we go on to examine how the OAB is generated and distributed, let’s first have a look at the properties of the Offline Address Book object and examine the various attributes. To do this, simply right-click the Default Offline Address Book object and click Properties from the context menu, or choose Properties from the action pane. The result is the window shown in Figure 2.

Figure 2: Default Offline Address Book General Tab

In Figure 2 the name of the OAB can be seen along with other information such as the name of the generation server, whether this OAB is the default OAB and also when this object was last modified. Additionally, you can also see that this OAB is scheduled to be updated daily at 5am. Understanding the default update schedule time is important since this forms the basis of delays in new or modified users appearing in the address books of cached mode Outlook users. For example, if a new user and associated mailbox is created by the helpdesk at 9am one day, that user’s mailbox will not be included in the OAB data on the mailbox server until 5am the following morning. There will be an additional delay before that user finally appears in the OAB on each other user’s cached mode Outlook session since Outlook must download the new OAB files after they have been made available on the Client Access Server responsible for web-based distribution. We will look at these other processes later in this article.

The Address Lists tab of the Default Offline Address Book is shown in Figure 3. This allows you to control whether you want the default Global Address List to appear in the OAB and, if you have created any, whether any other address lists are also to appear in the same OAB.

Figure 3: Default Offline Address Book Address Lists Tab

Finally there is the Distribution tab that can be seen in Figure 4. The Client Support area of this tab allows you to specify the different OAB versions that will be generated. If you have older versions of Exchange, such as Exchange 5.5 or Exchange 2000, or older versions of Outlook such as Outlook 98 SP1 still available within your organization, you may need to provide support for version 2 of the OAB. Newer versions of Outlook will make use of versions 3 and 4 and these are selected by default. Interestingly, it can be seen that it is possible to clear all three client support check-boxes and therefore you might assume that in such a case no OAB files will be generated. In this scenario, if no particular client support option is chosen, version 4 of the OAB will be generated.

Figure 4: Default Offline Address Book Distribution Tab

An important configuration area shown in Figure 4 is the ability to enable web-based or public folder distribution. Historically, public folders have been used to distribute the OAB to client machines running Outlook. With Outlook 2007 and Outlook 2010, web-based distribution is now available. We will look deeper at the web-based distribution method later in this article.

Don’t forget you can always use the Exchange Management Shell to view the OAB properties if you prefer. For example, to get a list of the OABs within the Exchange organization we can simply use the Get-OfflineAddressBook cmdlet. Since we know that the name of the only OAB currently configured within the Exchange organization is Default Offline Address Book, we can use the following cmdlet to examine the properties:

Get-OfflineAddressBook –Identity “Default Offline Address Book” | fl

You can see the results of running this cmdlet in Figure 5. In Figure 5, you can see the same information that we have already seen within the Exchange Management Console, such as the generation server name, the supported versions, the rebuild schedule and so on.

Figure 5: Properties of the Default Offline Address Book


That completes part one of this article. Admittedly we haven’t gone too deep so far but it’s important to provide the background information to the OAB, particularly if you are new to Exchange 2010. In the next part of this article we’ll start to look at the actual OAB generation process and cover what you can expect to see during this process.

If you would like to read the first part of this article series please go to:

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