This situation however is extremely rare since the default maintenance time on Exchange is at AM and updates and downloads are usually performed during working hours.

Even though Outlook is the last in the chain, it is often the first level where the troubleshooting takes place as usually this is where the request is coming from.

There are various Registry settings available to control or modify the update and download behavior of the Offline Address Book in Outlook.

Use Cached Exchange Mode but without OABTo always work with the Online Address Book, even when you have Cached Exchange Mode enabled, you can set the following Registry key and value.

You’ll have to rename them all to or, in the case of Outlook 2010 or Outlook 2013, rename the folder containing the oab-files to to reset the local Offline Address Book.

Renaming just a single or some of the files will result in an OAB corruption. A benefit of manually deleting the oab-file is that before they are being re-downloaded, you are working with the Online Address Book.

If the key name doesn’t exist, Outlook uses a value of 8.

Prompt before for full download As the OAB can be quite large in some environments, it could be wise to be prompted when Outlook wants to download the full OAB.

Finding out which GUID represents which mail account isn’t very straightforward but looking at the “Date modified” value of the folder should give you a good indication if you don’t want to simply delete all folders or rename them to

You’ll find the following 6 oab-files in this location which make up the full Offline Address Book: If you are still using Outlook 2002/XP or previous, the file names won’t have a “u” in front of their name.

In that case the whole OAB is being downloaded again.

In a later section, it is explained how to modify this.

I use Outlook where I have the Global Address List (GAL) online from an Exchange Server.