Beginning just this morning (July 12) when I open received messages (from my inbox) they open as if they are messages to be sent, and in a strange format that is completely different from the plain text and images I've seen for decades. There are boxes with colored lines around elements of the message and an unexpected black-on-white formatting toolbar which is bizarre given that the message I've opened is received and not a new message to be sent. I've not been able to find guidance for what to do to fix this. I have the same issue on separate computers, one running Windows 10 and one running Windows 11.

Edit 1:26 pm Maybe the gremlins left early for the weekend?? the problem totally disappeared. Messages open as before, not as messages to be sent, no more weird boxes, toolbar gone. On both computers, with no changes to settings.