in windows live mail, how do I cancel / eliminate error message re not sent mail ?

I had a connection problem with my standard e-mail account (sent mail did not go out); since resolved, but one of sent e-mails keeps coming up as error message each time I open the account ("do you now want to send" ?); when I choose "yes" I again get the same message, but all I want to do is cancel / remove this original send e-mail ..... Can anybody help?? Thanks.