Spam complaints are a critical metric to monitor. High spam complaint rates can damage your sender reputation and lead to your emails being blocked. To handle spam complaints effectively: - Provide an Easy Unsubscribe Option: Make it simple for recipients to opt-out of your emails. - Respect Unsubscribe Requests: Immediately remove users who unsubscribe from your list. - Analyze Feedback: Review complaints to understand why recipients are marking your emails as spam and make necessary adjustments.