Open Rate: The percentage of recipients who open your email. Click-Through Rate (CTR): The percentage of recipients who click on links within your email. Conversion Rate: The percentage of recipients who take the desired action, such as requesting a sample or making a purchase. Feedback: Customer feedback on the sample product, which can provide insights into product improvements and customer satisfaction. Sales Metrics: Track the number of sample-to-purchase conversions and overall sales generated from the campaign.