How Often Outlook Download Offline Address Book !full! May 2026

: The Exchange server (or Exchange Online/Microsoft 365) generates a fresh copy of the OAB from the Global Address List (GAL). In modern versions like Exchange 2016/2019 and Exchange Online, this usually happens every 8 hours .

: Outlook checks for and downloads these server updates once a day (every 24 hours). how often outlook download offline address book

If an administrator makes a change right after a server generation cycle, and your Outlook client has also just finished its 24-hour check, it can take roughly two days for those cycles to align and show the update. How to Force an Immediate Update : The Exchange server (or Exchange Online/Microsoft 365)

If you can't wait for the automatic sync, you can manually trigger a download to see the most recent changes immediately: Administering the offline address book in Outlook If an administrator makes a change right after

The delay occurs because the update happens in two distinct phases:

By default, Microsoft Outlook automatically downloads the Offline Address Book (OAB) if the application is left running constantly. However, the total time it takes for a change in the corporate directory (like a new hire or updated title) to appear on your computer can be as long as 48 hours due to the two-step synchronization process between the server and your Outlook client. Why Does It Take So Long?