[tim_iles]

The expected behaviour is that navigating away will not submit the data. That's pretty much consistent across all interfaces I know, with the exception of saving as draft, which still does not "submit" the data to the human recipient on the other end.

However, I do agree that clearing the message can have its uses, but as it's a secondary action, it deserves a far less prominent position for the button (e.g. maybe as an option on the long-touch menu, but at least not where you'd expect the Send button to be). On this app, it's in the primary action space and doesn't ask confirmation before wiping your message.