An email sending service embeds identifying information within emails sent on behalf of its service consumers. A recipient notifies their email provider that an email received from the service is a spam email (e.g., an unsolicited message). The email provider forwards a complaint, including a copy of the email, to the email sending service. The service utilizes the information embedded in the email to identify the responsible service consumer. The email sending service then takes corrective action as necessary to prevent or deter the identified service consumer from sending subsequent spam emails.