Bounce rate
Bounce rate is the percentage of sent emails that couldn't be delivered and were returned by the receiving server, split into hard bounces (permanent failures) and soft bounces (temporary ones).
How bounce rate is calculated
Bounce rate = bounced emails ÷ emails sent × 100. A bounce is a non-delivery report from the receiving server. Keeping this number low is essential: a high bounce rate signals a poorly maintained list and quickly erodes sender reputation.
Hard bounces vs soft bounces
- Hard bounce — a permanent failure: the address doesn't exist or the domain is invalid. Remove these immediately and never mail them again.
- Soft bounce — a temporary failure: the mailbox is full, the server is down, or the message is too large. Retried automatically; only remove after repeated failures.
How to keep bounce rate low
- Use double opt-in so invalid addresses never enter your list
- Validate new addresses at the point of capture
- Purge hard bounces automatically after every send
- Re-engage or remove long-dormant contacts before they decay
- Avoid purchased or scraped lists, which are full of dead addresses and traps
Frequently asked questions
What's an acceptable bounce rate?
Aim to stay under about 2%. Consistently higher rates suggest list-hygiene problems and will drag down deliverability.
Should I remove soft bounces?
Not on the first failure — they're often temporary. But if an address soft-bounces repeatedly across several sends, treat it like a hard bounce and remove it.
Do bounces hurt my reputation?
Yes. Repeatedly mailing invalid addresses tells providers your list is dirty, which lowers reputation and inbox placement for everyone on it.
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