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Metrics & Analytics

Email Bounce Rate

The percentage of sent emails that could not be delivered and were returned by the recipient's server.

Definition

Email bounce rate measures the percentage of emails that could not be delivered and were returned (bounced) by the receiving mail server. Calculated as (bounced emails / total sent) × 100, it indicates list quality and delivery problems. Bounces are categorized as hard bounces (permanent failures) or soft bounces (temporary issues).

Why It Matters

High bounce rates damage sender reputation and deliverability. ISPs monitor bounce rates as a signal of list quality - consistently high bounces suggest purchased lists or poor hygiene. Keeping bounce rate below 2% is essential for maintaining good deliverability.

How It Works

When an email cannot be delivered, the receiving server returns a bounce notification to the sender. Hard bounces occur for permanent reasons (address does not exist). Soft bounces happen for temporary reasons (full mailbox, server down). Your ESP tracks these and should automatically suppress hard bounces.

Best Practices

  • 1Remove hard bounces immediately and permanently
  • 2Monitor soft bounces and remove after multiple failures
  • 3Use double opt-in to verify addresses before adding to list
  • 4Clean your list regularly with verification services
  • 5Keep bounce rate below 2% (ideally under 0.5%)

Frequently Asked Questions

Industry standard is below 2%. Under 0.5% is excellent. Above 5% indicates a serious list quality problem that requires immediate attention. New lists or lists that have not been emailed recently may have higher initial bounce rates.

Not immediately - soft bounces are often temporary. Most ESPs retry soft bounces a few times. If an address soft bounces repeatedly over several campaigns, then remove it. One soft bounce should not trigger removal.