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Modify GAL synchronization to prevent Outlook 2010 contact issues

By modifying GAL synchronization, Exchange admins can prevent or fix problems with Outlook 2010 contacts.

How can I fix GAL synchronization in Outlook 2010 so it doesn't cause problems with my contacts?

I recently discovered a peculiar Outlook 2010 bug -- or feature, depending on who you ask. I opened one of my Outlook contacts and saw that most of the contact information had been edited or crossed out.

I noticed a few problems when I looked at the Notes section from one of my Outlook contacts. The Initials section had the letter "T" crossed out and was replaced with the letter "L." Likewise, the phrase "United States of America" had been crossed out and was replaced with "United States." This caught me by total surprise because I had never seen a problem like this before, so I thought it might be helpful to share a fix.

Basically, the problem stems from Outlook 2010's Global Address List (GAL) synchronization feature.

A quick note about GAL synchronization

GAL synchronization issues only occur in Outlook 2010. Microsoft replaced GAL synchronization in Outlook 2013 with a feature called GAL Aggregation and Favorites. GAL synchronization will occur only if it was enabled in Outlook 2010 prior to upgrading to Outlook 2013.

Outlook 2010 automatically compares users' contacts against entries before the GAL synchronization occurs. If a user's contact has the same SMTP address as a contact listed in the GAL, then the user's contact is updated with the GAL data.

Assuming the user's contact and corresponding GAL contact have no discrepancies, the user's contact is merely augmented. Any contact data that exists in the GAL but isn't present in the user's contact is copied from the GAL to the user's contact.

If there are discrepancies between a user's contact and contact information stored in the GAL, Outlook deals with the mismatch in one of two ways. The first is it simply edits the contact in a manner similar to what I described earlier. The other way it deals with the mismatch applies only to phone numbers. If a user's contact and the corresponding GAL contact contain two different phone numbers or the same phone number listed in two different formats, Outlook will attempt to preserve both numbers. In the case of a business phone number mismatch, the phone number stored in the user's contact will be moved from the Business field to the Business 2 field. The Business phone number stored in the GAL is copied to the Business field.

How to fix a GAL synchronization problem

GAL synchronization has the potential to be problematic, but there are easy ways to address this problem. Although GAL synchronization is uni-directional, it's possible for a user to manually correct their contacts after GAL synchronization has occurred.

The best way to prevent this problem (or to prevent it from occurring again after a user manually corrects their contacts) is to edit a Group Policy to disable GAL synchronization. Before doing so, you'll have to load the Outlook 2010 administrative templates.

To block GAL synchronization, open the Group Policy Management console and open the Group Policy you want to edit. Navigate through the Group Policy tree to:

User Configuration \ Administrative Templates \ Microsoft Outlook 2010 \ Outlook Social Connector.

Double-click on the Block Global Address List Synchronization option. When the dialog box for this setting opens, click Enable, followed by Apply and OK.

Globally disabling GAL synchronization might not always be the best option. In some cases, it's better to configure GAL synchronization to prompt users for permission before updating their contacts. This requires you to edit the Windows registry, which can be dangerous. Create a full backup prior to doing so.

To have Outlook prompt the user for permission before synchronizing GAL, open the Registry Editor and navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\SocialConnector.

Locate the ScheduleContactGalSync registry key. If this key does not exist, create it as a DWORD and assign it with a value of 2. A value of 1 allows automatic GAL synchronizations, and a value of 0 prevents GAL synchronizations from occurring.

About the author:
Brien Posey is a ten-time Microsoft MVP with two decades of IT experience. Before becoming a freelance technical writer, Brien worked as a chief information officer at a national chain of hospitals and healthcare facilities. He has also served as a network administrator for some of the nation's largest insurance companies and for the Department of Defense at Fort Knox.

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