In Mail, focus on a message and press enter to open it. Interact with the message text, stop interacting once, then press vo-left arrow. You will find a group of four unlabeled buttons with no help tags. Oddly, if you don't follow the above steps, these buttons rarely, if ever, appear. You might also find the buttons if you interact with the Message Headers Group once the message is open, then stop interacting and vo-right.