At worst, disable airport/unplug your ethernet cable - then delete the message.
The forums say you can put files offline and then any emails will go into the outbox that will temporarily appear until the end of the session. To send the emails you're then supposed to put the files online again. I've tried this numerous times but I don't get an outbox so the email goes and hides somewhere. When I click send again it automatically puts the files back online and the email comes out of hiding and is sent. Do you think there's a problem with my laptop? Anyone else have this problem?Adding to my own post, whatever possessed Apple to do away with the Outbox in Mail? Goodness me, that has saved many an awkward and potentially embarrassing (or worse) situation from developing. To Audioi I would suggest that a change of email application might just be a sensible solution. Incidentally, Thunderbird does not send to Outbox either.