and when they made tips for better etiquette, use sentence case, it is a rule, one of the only ones we've got. one place where it is still normal to write all communications with the caps lock key on is the united states navy. since the mid-19th century, all official naval messages were typed in upper case, that is in part because the navy was the adopter of the teletype machine, and so it ended up being all caps all the time. for decades, all military communications have been in capital letters, no sentence case, all caps, but now, the navy announced it will no longer use all caps. sentence case is the accepted form of communication and all naval personnel are hereby authorized to use mixed case, shift at will, except, apparently in the subject line of any official message. they will stay all caps, but