Deactivate Offline Address Book Download

When configuring an Outlook profile to use Cached Mode, the client software uses a unique address book to resolve email addresses and other information. This address book is named Offline Address Book (OAB) and is built and provided by the Exchange Organisation hosting the mailbox. The client downloads OAB changes when Outlook starts and checks for further OAB changes in intervals. 

OAB provides address resolver capabilities when there is no network connection to Exchange Server or a domain controller. In addition to resolver capabilities, the OAB contains other important information, e.g., send-as permissions and information regarding public folders.

For security reasons, it might be necessary to disallow the download of the Offline Address Book by an Outlook Client. In this case, you control the download functionality with the Windows System Registry. You can disable the OAB download using the following registry key:

Path: HKEY_CURRENT_USER\Software\Microsoft\Office\VERSION\Outlook\Cached Mode
Value type: REG_DWORD
Value name: DownloadOAB
Value: 0 
to not download the OAB

Replace with the appropriate Office version number.

With a deactivated OAB, download name resolution in Outlook Cached Mode requires network access to an Exchange Server.

Links 

• Administering the offline address book in Outlook

Enjoy Exchange Server.