[Microsoft Outlook] reading pane had been disabled

Problem
One day I found out my reading panel had been disabled in Microsoft Outlook.

It is very inconvenient for me, because I cannot preview my email anymore.

Root Cause
Because of corporate's security policy, it disabled all employees' reading panel in everyone's Microsoft Outlook.

Solution
1. Start => type in "regedit" => enter

2. Find the registry : HKEY_CURRENT_USER\Software\Policies\Microsoft\office\14.0\Outlook\options

3. Change the value of property, disablereadingpane, from 1 to 0

4. Restart Microsoft Outlook

Reference
[1] http://www.slipstick.com/outlook/rules/disable-outlooks-reading-pane/