What is a good email bounce rate?
Bounce rate is the share of sent messages a receiving server refused. Hard bounces mean the address does not exist and are permanent; soft bounces are temporary and resolve on retry. Only the hard rate matters for reputation, and above roughly 2% providers start treating you as someone who does not maintain a list.
Written by the SieveGuard team from the checks our own free tools run. Last reviewed .
Hard and soft are not degrees of the same thing
They are separate problems with separate causes and separate remedies, and averaging them into one percentage is how people end up fixing the wrong one.
| Hard bounce | Soft bounce | |
|---|---|---|
| Means | The address does not exist | The address exists but could not accept right now |
| SMTP class | 5xx | 4xx |
| Typical | 550 5.1.1 user unknown | 452 4.2.2 mailbox full |
| Retry? | Never | Yes, with backoff |
| Counts against reputation | Heavily | Barely, unless persistent |
| Action | Suppress on the first occurrence | Retry, then suppress after repeated failure |
The distinction is carried in the response itself — the first digit of the SMTP reply and the enhanced status code beside it. Any sending platform worth using classifies on that rather than on the human-readable text, and the codes decode cleanly once you know which is which.
Where the thresholds actually sit
Providers publish complaint-rate ceilings far more readily than bounce ceilings, so the numbers below are a mix of stated policy and consistently reported ESP enforcement. Treat the first row as a hard fact and the rest as operating guidance.
| Rate | Reading | What happens |
|---|---|---|
| Under 0.5% | Healthy | A well-maintained list on confirmed signups |
| 0.5% – 2% | Acceptable | Normal drift as addresses age out. Clean periodically |
| 2% – 5% | Flagged | ESPs warn; providers begin discounting your sending |
| Above 5% | At risk | Account suspension is a realistic outcome at most ESPs |
| Above 10% | Bought or scraped | Rebuild the list. There is no cleaning route back |
Two things worth separating from the number. Gmail states a complaint ceiling of 0.3%, which is a different metric and a much smaller budget — see sender reputation. And a low bounce rate on a large old list can hide a spam-trap problem, because a recycled trap is a real, deliverable mailbox. It never bounces.
Why the rate matters more than the bounces
A hard bounce costs you nothing on its own. Addresses die, people leave companies, domains lapse. What a provider reads is the rate, because it answers a question about you rather than about the address:
0.3% hard bounces → "this sender removes dead addresses" 6.0% hard bounces → "this sender is mailing a list they did not build"
That inference is the whole mechanism. Someone mailing addresses they collected themselves, with consent, has few dead ones. Someone mailing a purchased file has many. The rate distinguishes them without the provider needing to know anything else, which is exactly why it is weighted.
What actually drives it up
- Purchased or scraped lists. The largest cause by a distance, and the only one with no remedy short of not sending to it. Also carries spam traps, which are worse than bounces because they never announce themselves.
- Typos at signup.
gmial.com,hotmial.com,yaho.com. Entirely preventable at the point of entry and completely unfixable afterwards. - Natural decay. Roughly 2% of a B2B list goes stale per month as people change jobs. A list untouched for a year is substantially dead through no fault of anyone.
- Sending to catch-all domains. These accept everything at SMTP time and bounce later, or silently discard. Your bounce rate looks fine while the mail goes nowhere.
- Not suppressing. Re-sending to an address that already hard-bounced is the avoidable one, and it compounds: the same dead address inflates every send.
Getting it down
At the point of entry — where it is cheap
Validating at signup costs one API call and prevents the address ever entering the list. Syntax, then whether the domain has MX records at all, then whether the mailbox accepts mail. Catching a typo here is worth more than any amount of cleaning later, because the address never contributes to a rate.
On the existing list — before the next big send
Verify the list, suppress the confirmed-dead, and segment the unknowns rather than treating them as good. Do this before a campaign rather than after: the send is what converts a bad list into a reputation problem.
Continuously — the part people skip
Suppress on the first hard bounce, automatically, with no manual step. Then re-verify periodically, because a list decays whether or not you mail it. Quarterly is reasonable for B2B; annually is not.
What not to do
Do not send a re-engagement campaign to a list you suspect is dead. That is a large send to unverified addresses, which is the exact shape of the problem you are trying to solve. Verify first, then re-engage the survivors.
Sources
FAQ
What is a good email bounce rate?+
Under 0.5% for a list built from confirmed signups. Up to 2% is acceptable drift. Above 2% ESPs start flagging you, above 5% suspension becomes realistic, and above 10% the list was almost certainly bought rather than built.
What is the difference between a hard and a soft bounce?+
A hard bounce is a permanent 5xx refusal — the address does not exist, and it should be suppressed on the first occurrence. A soft bounce is a temporary 4xx, such as a full mailbox, and it usually resolves on retry. Only the hard rate meaningfully affects reputation.
Does one hard bounce hurt my reputation?+
No. Individual bounces are normal and expected — addresses die constantly. What providers read is the rate, because it tells them whether you maintain your list. A single bounce says nothing; six percent says you are mailing a list you did not build.
Why did my bounce rate spike suddenly?+
Usually a new list segment entering the send, an import that was never verified, or a suppression list that stopped being applied. Compare the bouncing addresses against your most recent import date — the pattern is normally obvious once you group by acquisition source.
Can I lower it by removing bounced addresses after the fact?+
Only for future sends, which is the point. Suppressing is what stops the same dead address inflating every subsequent campaign. It does not undo the damage from sends that already happened; that recovers through weeks of clean sending.
Do catch-all domains show up as bounces?+
Usually not, and that is the problem. A catch-all accepts everything at SMTP time, so a non-existent address there either bounces much later or is silently discarded. Your bounce rate looks healthy while the mail reaches nobody.
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