If you're writing emails to people who might not view them on a display with the same width as yours, you probably want to send the messages as "flowed" (as per RFC 2646) in order to let the recipient's device disregard the line breaks in your message and rewrap the text for readability. In `message-mode', you can do that by turning on the `use-hard-newlines' minor mode. However, you probably want some of your newlines to stay put, for paragraph breaks, and for content where you really do want to break the lines yourself. You can do that with `use-hard-newlines', but it doesn't show you where it's going to put "hard" newlines and where it's going to put "soft" ones. That's where `messages-are-flowing' comes in. It marks all "hard" newlines with a `⏎' symbol, so that you can have an idea about what parts of your message might be reflowed when the recipient reads it. To activate `messages-are-flowing', add the following to your .emacs: (with-eval-after-load "message" (add-hook 'message-mode-hook 'messages-are-flowing-use-and-mark-hard-newlines))