- Declining Engagement: When you notice a consistent drop in engagement metrics such as open rates and CTR, it's a clear sign. - Increased Unsubscribes: If people are unsubscribing at a higher rate, it's a warning sign. - Spam Complaints: More spam complaints are a sure indicator that your emails are not being well-received. - Deliverability Issues: When your emails start landing in spam folders more frequently, it might be a sign that you've crossed the Limit Phi.