'''If the 'Message Pane' is enabled then:''' '''''Using Mouse:''''' A single click on email in Message List will open and display message in Message Pane. A double click would open email in a new tab or window depending upon settings. '''''Using keyboard:''''' If you have focus on the Message List and use the keyboard arrow keys to navigate to another message in list then this is the same as if you clicked on the message and therefore it will open and display in Message Pane. It is the means of using the keyboard as an alternative to select emails. Very useful if your mouse has gone awol and suddenly does not work. '''If the 'Message Pane' is not enabled then:''' '''''Using Mouse:''''' A single click using mouse on email in Message List will just highlight the email allowing other actions to perform like drag and drop, but it will not open the email. A double click would open email in a new tab or window depending upon settings. '''''Using keyboard:''''' If you have focus on the Message List and use the keyboard arrow keys to navigate to another message in list then this is the same, it merely selects /highlights the email in the list, it does not open the email. Pressing 'Enter/Return' key opens in a new tab or window. This is a means of only using keyboard to open emails. ''' Basically:''' If you want to use the arrow keys to navigate up and/or down the Message List and not open email in Message Pane then you need to disable the Message Pane. '''To disable/enable Message Pane:''' # Quick method press key F8 # OR grab the top edge of Message Pane and drag down until it disappears Or drag up to reappear. # OR use View > Layout > select 'Message Pane'.