the unfortunate mishap of sending an e-mail to the ABSOLUTE WRONG person by mistake. This is especially likely if you are forwarding an e-mail from said WRONG PERSON to a friend, in order to provide your friend with a sound example of the type of idiocy you described so eloquently in the e-mail. Since you are forwarding, you end up replying, and VOILA! the WRONG PERSON has an email that says, "Look what this bitch said to me?" and scrolls down only to find the very same e-mail she sent you yesterday.
When i received a reply from my customer, telling me he would not be needing my services, i scrolled down only to find the e-mail i MEANT to forward to my manager, wherein i called the customer a Fucktard (see Fucktard for definition).