One thing not mentioned is to send it to yourself. That seems to trigger most of the emotional/regret glands associated with the send button, it stores the content of the message verbatim, and you can review it in the morning and really send it if you feel the same way. I also have Eudora configured so that it only sends mail once and hour so that even though I have hit the send button I typically have some time to experience the "l'esprit d'escalier" or "I wish I had said this instead" triggered by the send button.