Unfortunately once a campaign has been sent, it cannot be stopped or edited since the content has already been sent to the servers.

We serve content using a cloud computing environment. Once published, because of the infrastructure complexity, we can't go into the servers and make changes to campaigns that have already been pushed out for sending.

What You Can Do in the Future

It's best to make 100% sure you've done all your testing and proofing before you hit the send button. Recruit people to proof the campaign for you. Check every single link just to be sure they work. Once you the campaign sent, there's absolutely no going back. We cannot even stop the campaign in the database.