But you can train yourself never, ever to click Send without double-checking the To line and the Cc line.
And if you’re writing an e-mail in a state of agitation, you can learn the habit of filling in the To line last, or preceding it with x’s until you’re sure, or addressing it to yourself, so that it can’t slip out of your fingers without your review.
I learned these habits after a mistaken Send of a reply that was meant to be a behind-the-hand whispered forward to a friend. Instead, the person I was talking about got my unfavorable and not at all diplomatically worded comments straight from me. Happened to be a division manager of the company I worked for. Mistake you don’t make twice.