Most mail clients can be configured not to send messages immediately, but to hold them in the Outbox until you hit the main Send/Receive button. Also, I believ

Most mail clients can be configured not to send messages immediately, but to hold them in the Outbox until you hit the main Send/Receive button. Also, I believe Lotus Notes had the feature that enabled you to take a message back (it literally removed the unread message from the recipient's Inbox).