Don't send to works exactly like Send to but as an exclusion list. Pick one or more groups (for example All Users With Active Subscription or one of your Lists); anyone who matches those groups is removed from the audience built by Send to, even if they also match a Send-to group. The exclusion groups can use their own Trigger Date, Trigger Compare Value and Trigger Checkouts Count values, which appear under the Don't send to box when needed.

Example: Send to All Users, Don't send to Delivery tomorrow sends to every customer except those receiving a delivery tomorrow. Exclusions are stored with the campaign and shown in the Review step and on the campaign page.