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.
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.
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.
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.
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.