-->

Saturday, January 6, 2018

Exchange - Force Using The GAL In Outlook Cache Mode

My Exchange environment consists of two Resource Forests (one in the US and one in Europe) with one Accounts Forest that syncs MailContacts with MIM.
User accounts are created and edited by our ServiceNow application, which often changes primary SMTP addresses making the OAB (Offline Address Book) out of date quite often.

Outlook clients in cache mode don't download the OAB regularly (it's every 24 hours or so) which causes NDRs a lot when sending cross-forest because Outlook can't resolve the contact. Microsoft should fix this BTW!

There's three ways to fix this:

You can run Outlook in online mode, like I do because my mailbox is tiny (email is not a data repository!) but some users have giant mailboxes so that might not be practical.

Or, you can have users empty their Outlook autocomplete cache often - not practical at all, but a quick fix.

Or, we can force Outlook to use the online GAL, instead of downloading the OAB.

**Note** This can put extra strain on the network, but I've personally never seen any adverse affects since the GAL isn't all that big, and who still runs slow networks these days?

**Note** If Outlook clients were to ever run in Offline mode (like on an airplane), they will not be able to resolve contacts; so those traveling salespeople should still use the OAB

Follow these steps to force the GAL:

1. Close all open Outlook windows (and the SFB/Lync client if it's running)

2. Download "HKCU-Policies-OAB-0.reg" from my Google Drive

- This will create and set the DownloadOAB reg key in CurrentUsers/Policies to "0" which is disabled

3. Double-click the "HKCU-Policies-OAB-0.reg" file, click yes to import. Click OK.

4. Download "HKCU-Software-OAB-0.reg"  from my Google Drive

- This will create and set the DownloadOAB reg key in CurrentUsers/Software to "0" which is disabled

5. Double-click the "HKCU-Software-OAB-0.reg" file, click yes to import. Click OK.

6. Download "deletoab.bat" file from my Google Drive

7. Right-click, run the "deletoab.bat" file as admin

- This will delete the OAB directory and files in the user's Appdata\Outlook folder.

8. Navigate to the following folder: %localAppData%\microsoft\outlook and verify that "Offline Address Books" is gone.
 
9. Open Outlook, make sure Offline mode is not on and search for a name to see that it works.


If you have a lot of clients that need this change, you can set it up as a GPO to push it out - I'll write a post on how to do that at a later date.

No comments:

Post a Comment