Command + 1: Go to Important
Command + 2: Go to Batch
Command + 3: Go to Set Aside
Command + 4: Go to Today's Reminders
Command + 0: Go to More, where you can type to filter to any other view
Command + N: Compose a new message
Command + S: Sync all accounts
In the message list:
Up arrow: Focus on previous message. If the first message is currently focused, then it removes focus from the message.
Down arrow: Focus on next message. If no message is currently focused, then it focuses on the first message in the list.
Command + Down arrow: Expand collapsed messages and focus on the first of those messages. If there are no collapsed messages below the currently focused on, it will just focus on the next message.
Enter: Expands the currently focused message if there is more of it to show.
Escape: Collapse currently focused message, or if the currently focused message is not expanded, remove focus from the message.
Spacebar: Scroll down by one page.
A: Open the action menu for the currently focused message. From there you can type to filter the list, and hit return to move the message.
Command + “.”: Complete the currently focused message.
Command + Delete: Delete, sending the currently focused message to trash.
R: Open quick reply for the currently focused message.
Command + Enter: Send the reply when your cursor is in the quick reply box.
Command + Shift + F: Forward the currently focused message.
Command + Shift + R: Open a reply for the currently focused message in a new compose window.
In the action menu:
Up arrow: Focus on the result above the currently focused one.
Down arrow: Focus the result below the currently focused one.
Enter / Return: Select the currently focused result, taking the specified action.
Escape: Close the action menu.