How to remove queued newsletters from CRON

Hi!

I had a semi-successful first newsletter sending event yesterday. The dashboard still shows that 896 letters are waiting to be sent via CRON (disabled). How do I cancel this cron? I switched from php mailer to smtp and want to resend the newsletter to people who did not get it. However right now when I press send, it says that everyone has already got that newsletter.

Screenshot with statistics: http://i.imgur.com/H1r9kx4.png