These days as we upgrade to new Outlook clients (above Outlook 2007+), we can ditch public folders and use only Web-Based distribution of OAL. On our good old days we just have to update new Offline Address Book in Exchange Management Console and in few minutes Outlook can be updated with new updates. (Technically Outlook updates new address book every 8 hours).
But with web-based distribution of Offline Address List, updating the Offline Address Book is not enough to push the updates to Outlook right away. Trying to update OAL in Outlook manually will not get the new updates. To make this faster, Exchange (IIS) file distribution service needs to be updated with new file.
To update OAL delta file in File Distribution Service (in IIS), run the following command in Exchange Management Console. (Note, you have to run this against each CAS server in your Exchange Org.)
Update-FileDistributionService –Identity <CAS Server Name> –Type “OAB”
That’s after running above command, you can manually update the OAL in your Outlook. (File –> Account Settings –> Offline Address List).