Open a Message for Reading
If the Preview Pane is visible, a single click on a message will display it in the preview right below the list. In order to open a message in full view or a new window (depending on your settings), double-click it with the mouse. Another way to open a message in a new browser tab or window is to right-click on the subject and then choose “Open Link in New Tab/Window” from the browser’s context menu.
Selecting a message in the list will also activate toolbar buttons that offer further actions related to the selected message, such as replying, forwarding or deleting it.