PreviewPane Object (Outlook)
Displays content in a "single pane mode" by showing only the Preview Pane view.
Microsoft Outlook utilizes responsive design by enabling this auto-resizing feature using the PreviewPane object. This happens when the user resizes the Outlook window so small that there is only room to display a single pane. Use the PreviewPane object when the user has a small device, such as a tablet or phone, and the device rotates the Outlook window to display in portrait mode. Introduced in Office 2016.