You can use the arrow, Backspace and Delete keys to edit the text. Press Y or Enter to send the text now. Press N to return to editing mode. To abort the current message, press the Esc key at any time. Press Y to abort or N to return to the message.
Some levels ask for confirmation before aborting.
If you keep pressing Esc and answering Y when asked, you will eventually return to the main Mail options menu. Please note that this is only a notification of incoming mail and does not require immediate attention. Continue with whatever you were doing.