Bounce Rate explained: hard vs soft bounce and what to do about it
Bounce rate is the percentage of emails that fail to deliver. Learn the difference between hard and soft bounces, acceptable rates, and how to keep your list clean.
Bounce rate is the percentage of sent emails that cannot be delivered to the recipient’s inbox. The formula is: (number of bounces / number of sent emails) x 100.
Bounces are email marketing’s equivalent of returned mail. Some letters come back because the address doesn’t exist. Others because the mailbox is full. Both count, but the consequences are vastly different.
Hard bounce vs soft bounce
Hard bounce — permanent failure
A hard bounce means the email can never be delivered to that address:
- The email address doesn’t exist (typo, deleted account)
- The domain doesn’t exist
- The recipient’s server has permanently blocked your sender
Action: Remove hard bounces from your list immediately. Most email platforms do this automatically. Continuing to send to hard bounces is the fastest way to destroy your sender reputation.
Soft bounce — temporary failure
A soft bounce means the email temporarily couldn’t be delivered:
- The recipient’s inbox is full
- The recipient’s server is down
- The email is too large
- The recipient’s server is throttling you
Action: Email platforms typically retry 2-3 times over 24-72 hours. If an address soft bounces 3-5 times in a row, treat it as a hard bounce and remove it.
What is an acceptable bounce rate?
| Level | Rate | Assessment |
|---|---|---|
| Good | < 0.5% | Clean list, good hygiene |
| Acceptable | 0.5-2% | Normal for most lists |
| Problematic | 2-5% | Cleaning needed |
| Critical | > 5% | Immediate blacklisting risk |
New lists — especially those imported from CRMs or events — often have high bounce rates on the first send. Use an email verification tool like NeverBounce or ZeroBounce to validate addresses before you send.
How bounces affect your reputation
Email providers like Gmail, Outlook, and Yahoo monitor your bounce rate. A consistently high rate sends a clear signal: this sender doesn’t maintain their list, which is typical spam behavior.
The consequences escalate:
- Your emails start landing in the spam folder
- Your sending speed gets throttled
- In the worst case, your domain or IP gets blacklisted
Correct SPF, DKIM, and DMARC setup helps your overall deliverability, but it doesn’t fix a bounce problem. Bounces are about list quality.
How to keep your bounce rate low
- Use double opt-in — it eliminates typos and fake addresses at signup
- Verify imported lists — run them through a validation tool before sending
- Clean regularly — remove inactive contacts who haven’t engaged in 6+ months
- Monitor per campaign — a sudden spike in bounces can indicate a technical issue or a bad imported segment
- Warm up new domains — new sender domains that send high volume from day one trigger spam filters. Read more about email warmup
A low bounce rate is the foundation for good email deliverability. Without it, everything else — subject lines, content, segmentation — is wasted effort.