Offline Address book(OAB) Generation in Exchange and Outlook 2010


Offline Address book allows user to download the address book offline into the local machine. It helps to query the address book when you are not connect to the network. It’s a complete copy of the global Address book.

lets understand how the OAB is generated, synchronized and available for distribution for the outlook users.

1. One Mailbox Server in the Organization is identified as OAB Generation Server. This is first mailbox server in the organization or any mailbox server assigned with the OAB generation role during the later stage.

2.  OABGen service running on the mailbox server helps to generate ,creates and updates OAB files. OABGen service is part of the System Attendant Service. All OAB Generated file by default will be located at path “\Program Files\Microsoft\Exchange Server\V14\ExchangeOAB”.

3. OABGen communicates with the active directory and generates the address book for all the mailbox, contact and other exchange resources in the Exchange organization.

4. OAB files in the mailbox server are compressed file with the extension .LZX format.

5. Till now we have learnt how the OAB files are generated and how is created. Now lets learn how OAB is distributed to the clients ?

6. There are two ways for Distribution in Exchange 2010. They are through web based distributions and through public folder distribution.

7. Web based distribution is only supported with outlook 2007 clients and higher. OAB distribution through public folder is supported by any version outlook.

8. Lets only talk about the web based distribution as we  don’t want to use public folder any more and most of the clients are outlook 2007 or outlook 2010.

9. OAB files are generated in Exchange 2010 Mailbox servers and outlook do not connect directory to the mailbox servers. The solution approach is to use Client Access Server role with web based distribution.

10. On the Client Access Role server, a virtual directory called OAB runs with in the default web site. This virtual helps in distributing the OAB

11. Do you think we got the complete answer ? No. How does the OAB virtual directory gets the OAB data files from the mailbox server ?

12. Answer to this is Microsoft Exchange File Distribution Service running on the Client access Server

13. Microsoft Exchange File Distribution Servers polls the OABGen Server and copies the OAB data from the mailbox servers to CAS server.  Once the complete OAB data is copied then if there is any update then only that data is synchronized with CAS server. The synchronization or pol frequency is 8 hrs by default and you can change it if required using PowerShell cmdlets.

13. You may curiously wanted to know how the Web based distribution looks like. hold CTRL key and right click on outlook Icon system tray and Select “Email auto configuration” option from the menu.

14. Enter the User email address and password and click on Test. On the result tab you should be able to see what the OAB URL your outlook is connected to download the OAB from Exchange.

This is the quick info on how the OAB work in Exchange 2010.  I hope this article helps you all Smile

6 thoughts on “Offline Address book(OAB) Generation in Exchange and Outlook 2010

  1. You really make it seem so easy with your presentation but I
    find this topic to be actually something which I think I would never understand.
    It seems too complex and very broad for me. I’m looking forward for your next post, I will try to get the hang of it!

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