When a new email address is added to our company's Exchange server it doesn't show up immediately on my Outlook, and I suspect that it's because of the "cached mode".

When I disable cached mode and restart outlook I see the new address fine. But when I restore cached mode and restart outlook it's missing again. So I guess the cache wasn't updated by this move.

I tried deleting the .nk2 file in %appdata%\Microsoft\Outlook, but that didn't help.

How can I force Outlook to clear its address book cache?


This should be a server-level setting. Your Exchange admin should be able to configure the time interval between updates for your Offline address book downloads. It's possible that you're looking for the new users before your interval period has expired. To additionally complicate things, the OAB on the server is by default generated once per day, at midnight. Depending on the size of your organization and changes to default settings, it could take days before a new user can make its way into the OAB and onto your local copy.

It's also possible that there's an issue with client-server communication such that OAB downloads aren't happening.

If you go to Tools --> Send/Receive --> Download Address Book, does it successfully update? That will rule out a communications issue in receiving differential OAB updates.

MSKB 841273 is pretty exhaustive. There's a lot of server-side info there that won't help you, but there are some client-side settings you can change to monitor & adjust Outlook's OAB-fetching behavior.


I wrote this for my IT Dept for that same problem:

ISSUE: You have an Outlook client in cached mode that is not updating the OAB (Offline Address Book).

RESOLUTION: Remove/rename *.oab files in their %userprofile%\Local Settings\Application Data\Microsoft\Outlook. Next time you start Outlook it will re-download the address book and create new OAB files. The problem was the oab files got corrupt and would not catch new updates. If it continues to happen, try excluding these oab files from your anti-virus scanner.

(Another possible location for oab files: %userprofile%\AppData\Local\Microsoft\Outlook\Offline Address Books)

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