Open Rates: Higher open rates may indicate that your frequency is appropriate and your subject lines are effective. Click-Through Rates (CTR): Monitor your CTR to see if your content is engaging and driving action. Unsubscribe Rates: A rising unsubscribe rate may signal that you’re emailing too often. Spam Complaints: High spam complaints can indicate that your emails are not welcome or relevant. Conversion Rates: Track how well your emails are converting to sales or other goals.