Every marketing email is sent with the provider's subscription tracking enabled. Designer emails should include the Footer module, whose Unsubscribe Text and Unsubscribe Link (default text Unsubscribe, underlined, editable) point to the unsubscribe link, and the default email footer also carries No longer want to receive these emails? Unsubscribe. When a recipient clicks it:

• the provider records the unsubscribe and suppresses future marketing emails to that address (they are dropped rather than delivered);
• Sprwt logs an unsubscribe event, which appears in the campaign's Unsubscribed statistic.

Separately, registered customers can untick the receive email box in their Profile, and admins can turn off Receive Email? on a contact or the This user receive EMAIL? box on a customer; anyone with that flag off is excluded from every campaign and flow. In the current version an unsubscribe click does not automatically untick the customer's Receive Email flag in Sprwt – the block happens at the sending provider – so a customer may still show as Can Receive Email: Yes in a list even though they no longer receive emails.