Open your DealMachine mobile app or log on with your computer to Dealmachine.com
Click the menu button in the top left (mobile only).
Scroll down until you see "Stop All Sending" and turn it ON.
Turning this option ON, would automatically move all of your leads back to the PENDING APPROVAL status and stops any future mail from going out.
Before turning this feature on, it would be best to build a list of leads you would want to keep on their current status so you could go back and put them(to their old status) back when needed.