Measuring campaign success involves tracking various key performance indicators (KPIs). The most common KPIs include: - Open Rates: The percentage of recipients who open the email. - Click-Through Rates (CTR): The percentage of recipients who click on one or more links in the email. - Conversion Rates: The percentage of recipients who complete a desired action, such as making a purchase or filling out a form. - Bounce Rates: The percentage of emails that could not be delivered to the recipient's inbox.