Your email bounce rate is one of the few numbers that mailbox providers can see about you, and it tells them a great deal. A low rate says you know your recipients. A high rate says you are mailing addresses you collected carelessly, bought, scraped or never cleaned. Because providers use this signal when deciding how to treat your mail, a rising bounce rate is usually the earliest warning of a deliverability problem. This guide explains what the bounce rate is, how to calculate it correctly, the difference between hard and soft bounces and why it matters, what counts as a healthy number, why you should be careful with industry benchmarks, the common causes of high bounce rates, a practical plan for reducing it and how to monitor it over time. For the technical meaning of individual rejection codes, see our guides to SMTP bounce codes and email bounce-backs.
What is an email bounce rate?
The bounce rate is the share of the messages you sent that were rejected by the recipient's mail system and returned to you. A bounce is different from a message that reaches the inbox, the spam folder or is silently dropped. It is a definite rejection, either at the moment of delivery or shortly after, reported by the receiving server with a code and a reason.
How to calculate your email bounce rate
The formula is simple:
Bounce rate = (number of bounced emails ÷ number of emails sent) × 100
For example, if you send 20,000 messages and 300 bounce, the rate is 300 divided by 20,000, which is 1.5 percent. Some reports use "delivered" instead of "sent" as the denominator, which gives a slightly different figure, so check how your sending platform defines it before comparing numbers. Calculate separately for hard and soft bounces, per campaign and per sending domain or address, because an average can hide a bad segment. Our email analytics shows bounce counts by type so you can do this without a spreadsheet.
Hard bounces and soft bounces
| Type | Meaning | Common causes | What to do |
|---|---|---|---|
| Hard bounce | Permanent failure; the message can never be delivered | Address does not exist, domain does not exist, recipient server blocks your mail permanently | Suppress immediately; never retry |
| Soft bounce | Temporary failure; the message may be delivered later | Full mailbox, server temporarily unavailable, message too large, temporary rate limiting | Retry for a limited time; suppress after repeated failures |
| Block bounce | The receiver refuses mail because of your reputation, IP address or content | Blocklists, authentication failures, spam-like content | Investigate the cause; see blocked messages |
The classification of bounces is not always clean, since receiving servers use codes inconsistently. A good sending platform reads the code and text and makes its best judgment.
What is a good email bounce rate?
There is no single correct figure. Guidance you will see commonly keeps the hard bounce rate very low, often cited as below about two percent, with lower being better, and treats rates much above that as a problem. Treat any number like this as a rule of thumb, not a standard. Different mailbox providers and sending platforms set their own thresholds, which they may change, and some will pause an account at a rate well within what blog posts call acceptable. The practical goals are:
- Keep hard bounces as close to zero as you can, since they are almost entirely avoidable.
- Look at the trend. A jump from 0.3 percent to 1.5 percent in one send is a stronger warning than a stable 1.2 percent.
- Compare against your own history and segments, not a generic average.
- Read your sending platform's policy, because a threshold that triggers a review may be lower than you expect.
A word on benchmarks
Industry benchmark tables circulate widely, but they mix senders of very different list quality and use different definitions. We deliberately do not publish a benchmark table here. Your own baseline is a better guide.
Why a high bounce rate is a problem
- Providers treat it as a sign of poor list management and may filter or block your mail.
- Your sending platform may suspend your account to protect its reputation.
- You may hit spam traps, which can lead to blocklisting. See spam traps.
- You waste sending capacity and money.
- Real customers who mistyped their address never receive what they asked for.
Common causes of high bounce rates
- Old lists. People change jobs and abandon mailboxes. A list that has not been mailed for a year decays.
- Typos at sign-up. Missing letters in popular domains are very common.
- Bought or scraped lists. Almost always full of invalid addresses and traps.
- No validation or confirmation. Forms that accept anything let bad data in.
- Fake sign-ups and bots. Forms without protection collect junk.
- Sending errors. A broken merge field or a wrong domain can generate failures.
- Authentication and DNS problems. Missing SPF or DKIM, or a poor sending reputation, produce block bounces. See authenticating your domain.
- Content or volume spikes that trigger rate limits.
How to reduce your email bounce rate
- Validate at the point of collection. Check syntax and domain records on sign-up forms, and offer a "did you mean" suggestion for typos. Use the free email validator or the validation API.
- Use double opt-in where it fits. A confirmation link proves the address works. See double opt-in.
- Suppress hard bounces automatically and after repeated soft bounces.
- Clean the list regularly, especially before large sends or after a long gap. See email list cleaning.
- Never use purchased lists.
- Protect your forms with rate limits and bot checks.
- Fix authentication and reverse DNS, and check blocklists. See blacklist checks.
- Ramp volume gradually with a new domain or address. See email warm-up.
A worked example
Suppose you send a monthly newsletter to 50,000 subscribers. One month the report shows 1,500 bounces, a rate of three percent. Instead of reacting to the total, split it. If 1,100 are hard bounces to addresses that do not exist and 400 are soft bounces from full mailboxes, the hard rate is 2.2 percent and the soft rate 0.8 percent. Next, group the hard bounces by source. If most come from contacts imported last quarter from an event, you have found the cause, and the fix is to validate that segment and suppress the failures. If instead they are spread across years of sign-ups, the list has aged, and a full validation pass is due. If the bounces cluster at a single mailbox provider and carry a policy message, you are looking at a block, which needs a different response entirely.
Then compare with last month. A rate that was 0.4 percent and is now three percent calls for investigation before the next send. Make the habit routine: look at the split, the source and the trend after every campaign, and the bounce rate will stop being a surprise.
Monitoring your bounce rate
- Review bounce rate per send, not only monthly averages.
- Set an alert for sudden increases.
- Look at bounce reasons: a cluster from one provider suggests a block, a scattering suggests bad data.
- Watch it alongside complaints and engagement. See Google Postmaster Tools and reputation monitoring.
- Use webhooks to capture bounce events in your own system. See webhooks.
Catch bad addresses at the door Validate sign-ups, suppress bounces automatically and watch the trend in analytics.
References and further reading
Frequently asked questions
What is email bounce rate?
The share of sent messages that were rejected by the recipient's mail system and returned, expressed as a percentage.
How do I calculate email bounce rate?
Divide the number of bounced emails by the number sent and multiply by 100. Check whether your platform uses sent or delivered as the denominator.
What is a good email bounce rate?
Keep hard bounces as close to zero as possible. A figure under about two percent is a commonly cited rule of thumb, but thresholds vary by provider and platform, and the trend matters more.
What is the difference between hard and soft bounces?
A hard bounce is a permanent failure such as a nonexistent address. A soft bounce is temporary, such as a full mailbox, and may succeed on a later attempt.
How can I reduce my bounce rate?
Validate addresses at sign-up, use double opt-in, suppress hard bounces, clean the list regularly, avoid purchased lists and fix authentication problems.