Change the layout, theme and sidebar

1. Open Settings › Appearance.
2. Under Layout, choose Email beside the list or Full width, like Gmail.
3. Pick Spacing and how many Lines of preview to show.
4. Choose Light, Dark or Follow the Mac, and a text size.

The sidebar

• Drag items to put them in any order.
• Right-click an item and choose Hide from sidebar.
• More holds Snoozed, Scheduled, Reminders, Muted, New senders, Calendar and Contacts.
• ⌘\ hides or shows the whole sidebar.