How do ESPs suspend or warn bad senders?

**ESP** enforcement typically escalates progressively. First warnings notify senders of policy violations or concerning metrics. If problems persist, sending limits may reduce volume. Continued issues lead to temporary suspension, then permanent termination.

Common triggers: complaint rates exceeding thresholds (often 0.1%), high bounce rates indicating list quality issues, **spam trap** hits suggesting purchased lists, content violations (**phishing**, prohibited content), or authentication failures.

Process varies by **ESP**. Some enforce automatically based on metrics; others involve human review. Appeals processes allow senders to explain circumstances and request reinstatement. Severe violations (**phishing**, **malware**) typically result in immediate termination without appeal.