On Mail Activity tab
Shift + L: Go to last seen email
Up, Down, Space Bar: Preview email
Page Up/Down: Scroll email list up/down
"A" or Cmd + A: Select all emails
"N" or Ctrl/Cmd + N: Compose new email
"Q" or Ctrl/Cmd + Q: Mark as read emails
Ctrl/Cmd + Enter: Send email
Alt/Option + Q: Focus on quick search
Escape: Close preview email/ Close context menu
On compose email text editor
Ctrl-C: Copy
Ctrl-V: Paste
Ctrl-X: Cut
Ctrl-Z: Undo
Ctrl-A: Select all