What is Bounce Rate?

Bounce rate is one of the most closely watched metrics in email operations because it directly signals the health of your sending practices. When you send a message and the receiving server cannot deliver it, the server generates a bounce notification (a Non-Delivery Report or NDR) that describes the failure. Hard bounces indicate a permanent problem, such as an address that does not exist, and should result in immediate suppression of that address. Soft bounces indicate a temporary condition, such as a mailbox at capacity, and the sending system should retry with appropriate backoff logic.

Mailbox providers like Gmail, Outlook, and Yahoo track bounce rates as a key input to sender reputation scoring. A sender that consistently generates high bounce rates is likely sending to unverified or purchased lists, a hallmark of spam. Even legitimate senders can experience reputation damage if they fail to remove invalid addresses promptly. Industry best practice is to implement real-time bounce processing that automatically suppresses hard-bounced addresses and monitors soft-bounce patterns for addresses that should be retired.

Afterdraft minimizes bounce rates through a multi-layered approach. Before sending, its address validation engine checks syntax, DNS records, and mailbox existence to flag risky addresses. During sending, real-time bounce processing immediately suppresses hard-bounced addresses across all AI agents. Post-send analytics surface bounce trends by domain, campaign, and time period, enabling you to identify and address list quality issues before they escalate into reputation problems.