Your System Administrator may instruct you to uninstall the Outlook plug-in for Classic Outlook Integration.
To uninstall the Outlook plug-in:
Note: The plug-in cannot be uninstalled when User Account Control (UAC) is enabled in Windows Vista or Windows 7. To uninstall the plugin, a user with administrator privileges must temporarily disable UAC. After uninstalling, the administrator can re-enable UAC.
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See Also:
Downloading the Outlook Plug-in for Classic Outlook Integration