Email Floodgate Protection

Definition

Floodgate protection prevents automated email systems from sending excessive volumes when a trigger event fires many times in rapid succession or when a configuration error would cause unintended sends. Common scenarios requiring floodgate protection include a data import that triggers welcome emails for thousands of subscribers simultaneously, a website outage that triggers multiple error notifications per subscriber, a loop where a trigger event fires repeatedly for the same subscriber, or a calendar event like Black Friday that concentrates sends into a narrow window.

Protection Mechanisms

• Rate limiting that caps sends per minute or per hour regardless of trigger volume
• Per-subscriber frequency capping that prevents multiple triggered sends within a defined window
• Circuit breaker patterns that pause sending when error rates or send volumes exceed thresholds
• Deduplication that prevents the same trigger from firing multiple times for the same event
• Queue management that prioritises triggers based on time sensitivity

Best Practices

• Implement floodgate protection at the infrastructure level rather than relying on campaign-level settings alone
• Test floodgate mechanisms with simulated volume spikes during platform deployment
• Set alert thresholds that notify the team when floodgate protection activates
• Document floodgate configuration so it can be reviewed and updated as send volumes grow
• Include floodgate protection in ESP evaluation criteria