How can I delete the send queue for eNewsletter?

Today I had an issue that it's probably too late to "fix", but I'd love to know for the future. I recently moved the mail server that eNewsletter typically sends through. Today I created a new newsletter for the first time since this server move. I did a test message that did not arrive, so I went and looked at the SMTP server settings, and indeed I needed to change them. A newsletter that I had sent in November, but that apparently had gotten "stuck", suddenly started sending. By the time I realized what was up, and that it was sending to about 3000 users, I didn't know how to stop it! It's almost finished by now, but is there a way that I can stop a message in the future? I didn't not know where to look for the "queue". I could see that "x" messages were in the queue, but no way to keep it from sending. I could see the location to change the queue "time", but no way to just cancel the queue entirely. There is a "cancel" option when you are editing, but I think that is just to cancel the edit, and not cancel the queue.