How do ESPs decide to throttle or suspend accounts?

ESPs apply enforcement based on multiple risk signals:

Complaint rate thresholds trigger warnings when rates exceed platform limits, typically around 0.1-0.5%. Sustained high rates lead to throttling or suspension.

Bounce rate spikes indicating bad list quality prompt investigation and potential sending limits.

Spamtrap hits often trigger immediate suspension pending investigation, as traps indicate serious list problems.

Volume anomalies where sending patterns suddenly change may trigger manual review.

ISP feedback where providers complain directly to ESPs about specific senders results in enforcement action.

ESP enforcement is like the shipping company's internal discipline process. Captains who damage the company's reputation face warnings, restrictions, and eventual termination if problems persist.