Outlook may be slower to resolve names because there are no .oab files locally
Article
Applies to:
Outlook 2019, Outlook 2016, Outlook 2013, Microsoft Outlook 2010, Microsoft Office Outlook 2007, Microsoft Office Outlook 2003, Outlook for Microsoft 365
Original KB number: 2746896
Symptoms
In Microsoft Outlook, when you attempt to resolve the email address for someone in your Microsoft Exchange organization, the process may take longer than expected. Or, if you are working offline, you are unable to resolve any names for people in your Exchange organization.
Cause
This problem occurs if Outlook is not using local Offline Address Book (OAB) files to resolve names. Instead, Outlook is performing name resolution using the online Global Address List (GAL). If you are in Online mode, this is to be expected. However, if you are in Cached mode, the default configuration is to always download the OAB locally and use it for name resolution.
Resolution
To resolve this problem, download the Offline Address Book using the following steps (depending on the Outlook version).
Outlook 2010 or later versions
Select the Send/Receive tab on the Ribbon.
Select Send/Receive Groups and then select Download Address Book.
Select OK.
Outlook 2007 or Outlook 2003
On the Tools menu, point to Send/Receive, and then select Download Address Book.
Select OK.
See the following article if you are unable to download the OAB.
If the OAB does not automatically download and you have to manually download the OAB each time (using the above steps), check for the existence of the DownloadOAB value in the registry. The following article provides complete details on this registry value.
Use the following steps to determine if you are using the online GAL for name resolution instead of local .oab files.
Start Outlook.
Select the Address Book icon.
In the Address Book dialog box, right-click drop-down under Address Book and select Properties (The screenshot for this step is listed below).
In the Global Address List dialog box, examine the text in The current server is: box (The screenshot for this step is listed below).
If you see a local file path, as shown in the above figure, you are downloading the .oab files locally.
If you see the name of a server, you are currently not downloading .oab files locally.
The location of the files on your computer varies according to your Outlook version and the version of Windows on which Outlook is installed. The default location for .oab files is provided below.
<guid> in the above folder path varies between Exchange organizations. The folder name, for example, will look like 0a1f33a0-dbeb-4007-92e3-57926c848000
This module examines how clients connect to Microsoft 365. It also provides instruction on how to configure name resolution and Outlook clients, and how to troubleshoot client connectivity.