When you have Cached Exchange Mode enabled, Outlook by will by default cache the main Global Address List as well.
This is called the Offline Address Book and is being generated on the Exchange server.
Full OAB download threshold To modify the threshold at which Outlook will download the full OAB rather than the incremental update, you can set the following Registry value Key: As the value, set at which relative size a full OAB download should take place rather than an incremental update.For instance, setting the value to 4 will trigger a full download when the incremental update is larger than one-fourth the size of the full OAB.When the value is set to 0, Outlook will use 16 to prevent a “divide by 0” error.If the key name doesn’t exist, Outlook uses a value of 8.Key: Note: As Outlook 2010 an Outlook 2013 can connect to multiple Exchange servers in a single mail profile, there is an additional “Offline Address Books” subdirectory which contains folders with GUID references which contain the actual oab-files.
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
The command for the manual update procedure can be found here: Outlook will automatically download updates only unless the size of the changes is larger than 12.5% (one-eighth) of the total OAB size.
In that case the whole OAB is being downloaded again.
OAB Update schedule To change the OAB Update Schedule via the Exchange Management Console: Organization Configuration-Rather than changing the default schedule, you can also force an update and redistribution of the Offline Address Book.
This is great for testing or when it is important that changes are published immediately (note that users must still update the OAB manually or wait a OAB sync interval to see the changes).
This means that in the worst possible scenario, an update to the Address Book won’t become available to the user until 48 hours after the change.