Default global address list is not updating
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.
This allows you to abort the update process when you are for instance on a slow or expensive connection.
In this guide, the relevant timings are explained and instructions are given in how you can directly force an update and resync, which can be very handy when troubleshooting or when you work in an Exchange environment which sees a lot of user mailbox mutations.
In a later section, it is explained how to modify this.
There are various Registry settings available to control or modify the update and download behavior of the Offline Address Book in Outlook.
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.