Not every email you send reaches a person. Some come straight back.
That returned message is a bounce, and the share of your sends that bounce is your email bounce rate. It is one of the simplest deliverability metrics to track, but it is also one of the most important, because mailbox providers use it as a quick signal of list quality.
A low bounce rate means your list is clean and your sending practices are sound. A high bounce rate means your messages are hitting dead addresses, full inboxes, or blocking systems — and your sender reputation is paying the price.
This guide covers the formula, the two types of bounces, realistic benchmarks, common causes, and how to keep the number low.
How to Calculate Email Bounce Rate
The formula is straightforward:
Bounce rate = (Bounced emails ÷ Emails sent) × 100
If you send 10,000 emails and 180 bounce, your bounce rate is 1.8%.
Most email service providers calculate this automatically. The thing to watch is the denominator. Some tools report bounce rate against emails delivered rather than emails sent, which produces a different, usually lower number. When you compare your rate to a benchmark, make sure you are using the same denominator.
You can also use an email bounce rate calculator to handle the arithmetic and compare your result against common thresholds.
Hard Bounces vs Soft Bounces
Not all bounces mean the same thing. The first thing to check when you see a bounce is whether it is hard or soft.
| Bounce type |
Meaning |
Common causes |
Action |
| Hard bounce |
Permanent delivery failure |
Invalid email, domain does not exist, account deleted |
Remove from list immediately |
| Soft bounce |
Temporary delivery failure |
Full mailbox, server down, message too large, rate limit |
Retry a few times, then suppress |
Hard Bounces
A hard bounce is a permanent rejection. The address, domain, or mailbox is not there any more. Continuing to send to hard-bounced addresses is one of the fastest ways to look like a spammer to mailbox providers.
Reputable ESPs suppress hard bounces automatically after the first occurrence. If yours does not, you should remove them yourself before the next send.
Soft Bounces
A soft bounce is a temporary problem. The address may be valid, but the message could not be delivered right now. Common reasons include:
- The recipient's mailbox is full.
- The receiving server is offline or busy.
- The message exceeds the recipient's size limit.
- Your sending IP is being rate-limited.
Most ESPs retry soft bounces over a day or two. If the same address soft-bounces repeatedly — typically four or five times — treat it as a hard bounce and suppress it.
For a deeper look at why mail gets rejected, see our guide to the 47 reasons your email was rejected.
What Is a Good Email Bounce Rate?
The answer depends on list quality and acquisition practices, but the ranges below are widely used by deliverability teams.
| Bounce rate |
Interpretation |
| Below 0.5% |
Excellent list hygiene |
| 0.5% – 2% |
Normal and healthy |
| 2% – 5% |
List quality issues; clean and validate |
| 5% – 10% |
High risk of throttling or spam-foldering |
| Above 10% |
Critical; sends may be blocked |
A single campaign above 2% is not a disaster, but a sustained pattern above that level will damage your reputation. If you cross 5%, most major providers will start treating your mail more aggressively.
These numbers sit alongside other deliverability signals such as spam complaint rate and inbox placement. Our email deliverability checklist explains how they work together.
Why Emails Bounce
Bounces usually fall into one of four categories.
1. Bad List Data
The most common cause is simply an invalid address. Typos at signup, expired free-email accounts, and stale lists all produce hard bounces. The older the list, the worse the problem.
2. Full or Inactive Mailboxes
A mailbox that has hit its storage limit will soft-bounce until the user clears space. Accounts that have been abandoned sometimes bounce as well.
3. Authentication or Policy Failures
If your SPF, DKIM or DMARC records are missing or misaligned, some receivers will reject your mail outright. This is especially true for bulk senders under the Gmail and Yahoo bulk sender requirements. We cover every authentication method in our guide to email authentication methods.
4. Content or Reputation Blocks
Even with a valid address, aggressive spam filters can reject your mail. Triggers include suspicious links, poor sender reputation, or content that looks like phishing. If you are seeing bounces alongside spam-folder placement, see our breakdown of what triggers email client spam filters.
How to Lower Your Bounce Rate
Bringing the number down is mostly about list hygiene and sender infrastructure.
- Use confirmed opt-in. A double opt-in step catches typos and fake addresses before they enter your list.
- Validate addresses at signup. Real-time email validation can reject malformed or role-based addresses immediately.
- Remove hard bounces immediately. Do not wait for a second attempt.
- Suppress chronic soft bounces. After a few retries, treat them as undeliverable.
- Clean your list regularly. Run a re-engagement or sunsetting campaign for inactive subscribers.
- Keep authentication records current. Maintain SPF, DKIM and DMARC, and monitor them through Postmaster Tools.
- Never buy or scrape lists. Purchased lists are full of invalid, spam-trap and inactive addresses.
For more on maintaining a healthy list, read our guide to email list growth and health metrics.
Bounce Rate in Your Reporting
Bounce rate belongs in every campaign report, but it is most useful when tracked over time rather than in isolation.
- Calculate it consistently using emails sent as the denominator.
- Split it into hard and soft bounces.
- Track it by source to see which signup channels produce the cleanest lists.
- Watch trends month over month; a rising bounce rate is an early warning of list decay.
Pair it with email deliverability metrics and your spam complaint rate for a fuller picture of sender health.
Key Takeaways
- Bounce rate is (bounced emails ÷ emails sent) × 100.
- Hard bounces are permanent; remove those addresses immediately.
- Soft bounces are temporary; retry a few times, then suppress.
- A healthy bounce rate is under 2%; anything above 5% needs urgent attention.
- The main fixes are confirmed opt-in, real-time validation, regular list cleaning, and correct authentication.
- Bounce rate is a deliverability signal; ignore it and your inbox placement will fall.
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