How do I stop a scheduled email campaign from going out?

Go to Marketing → Email Campaigns and find the campaign marked Scheduled.

• Click Cancel on its row and confirm with Cancel campaign, or
• open it and click Cancel schedule in the blue bar.

A cancelled campaign is not sent. You can also cancel a campaign that is already sending: anyone not yet emailed will not get it, but emails already sent cannot be recalled. Cancelled campaigns can be deleted from the list.