In Outlook, Global Address List is not default while composing new message or in Address Book. "All Rooms" is showing as default. In OWA, the behaviour is OK (GAL is default). My Exchange 2007 was upgraded from 2003. Any solution is much appreciated. Thanks.

Hello, Generally, we can manually set the default address book by the following steps via Outlook UI: 1. In Outlook, press Ctrl + Shift + B keys. 2. Click Tools, Options. Make sure “Global Address List” is selected. Thanks, Simon

Thank you Simon, appreciate your input. However setting in every clients (Outlooks) in the whole organization is not desired solution. Would be the best if we could set in Exchange server or through GPO or through Office Customization Tool (can be pushed through ConfigMgr). Hope we will have better solutions :)

Hello, Firstly, I would like to inform the default settings for the Address Book are not set by Exchange Server. They are created when installing the Outlook client. Based on my research, the default settings for the Address Book are controlled by the following registry key in Windows. HKEY_USERS\<USERSID>\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\<PROFILENAME>\9207f3e0a3b11019908b08002b2a56c2 Therefore, I suggest we first check if there are any group policy to affect these registry keys. Hope that helps. Thanks, Simon

Thank you, I'll have a look on the applied GPO objects and look for the culprit, if none, hope it is ok to add a GPO to modify this reg value.