Can't delete message stuck in outbox

My wife tried to send a message to several hundred recipients last night and the .Mac mail server choked on it. The problem is that the list of intended recipients is so long that it goes off the bottom of the screen and I can't close the window. We have to force quit Mail to exit it (the red button to close the message window is greyed out) and, even though I deleted the outgoing server Mail is trying to use from the accounts list, it keeps trying to send the message. Does anyone know how I can get rid of this thing?

For a hilarious Exposé screenshot, you can go to files.me.com/holtfam/whts6e

Help. Thanks.

Message was edited by: montreal1