Email bounce rate is the share of sent messages that were not delivered. The formula is simple, but the thresholds people quote depend on who is counting. Amazon SES publishes the clearest numbers: stay below 2%, expect a review at 5%, and a possible sending pause at 10%. Google’s sender guidelines set a spam rate threshold instead of a bounce one.
The short version
Divide bounced messages by attempted deliveries and multiply by 100. Keep the total under 2% and hard bounces under 1%. If the rate climbs past 2%, split the data by source, receiver and bounce reason, and pause the riskiest source first.
How to calculate email bounce rate
The Suped guide gives the formula as bounced messages divided by attempted deliveries, times 100. The denominator counts only messages handed to the delivery system, so pre-send suppressions are excluded. Count each message once, by its final outcome, rather than once for every SMTP retry.
A worked example, with invented numbers and our own arithmetic: if you attempt 5,000 deliveries and 90 bounce, the rate is 90 divided by 5,000, which is 1.8%. That is inside the 2% line. At 160 bounces the same send would be 3.2% and would call for investigation.
| Bounce type | What it is | Counts toward the Amazon SES rate? |
|---|---|---|
| Hard bounce | A permanent failure, such as an address that does not exist | Yes, when sent to a domain you have not verified |
| Soft bounce | A temporary failure, such as a full mailbox | No |
| Blocked IP bounce | The receiver refused the sending address | No |
| Policy rejection | A refusal for authentication or policy reasons | Not an invalid address by default, so handle it as a deliverability issue |
Our guide to hard and soft bounces explains how to tell the two apart from the SMTP code.
What thresholds are actually published
| Source | Level | What it says |
|---|---|---|
| Amazon SES | Below 2% | Recommended for best results, because higher rates can affect delivery |
| Amazon SES | 5% or more | The account is placed under review |
| Amazon SES | 10% or more | Sending might be paused until the cause is fixed |
| Suped guide | Under 1% hard bounces | Suggested target, and suppress an invalid address after one clear hard bounce |
| MailReach guide | Above 3% | Pause and clean the list, in the context of warming a new domain |
Amazon says its rate uses a representative volume, an amount of email that reflects your typical sending, rather than a fixed period. It also says the pause threshold uses the word might, so a 10% rate does not guarantee a pause. Other platforms and mailbox providers publish different numbers or none, so treat 2% as a working target and not as a universal rule.
Why a bounce rate rises
Most spikes trace to the list. Stale addresses, typos and a bad source all produce hard bounces, and a new segment of unverified contacts is the usual trigger. Our guides to B2B email verification and cold email lead sourcing cover cleaning a list and judging where it came from. Catch-all domains add uncertainty, which is the subject of the piece on catch-all addresses.
Not every bounce means a dead address. A refusal for authentication reasons looks like a bounce but is a record problem, as described in our guide to the 554 5.7.5 error. Check the bounce code before you suppress a contact.
How to bring a high rate down
- Suppress an invalid address after one clear hard bounce.
- Verify new segments before the first send.
- Split the data by source, receiver and bounce reason to find the cause.
- Pause the riskiest source first, and stop a new segment if non-existent-address failures approach 4%, a guardrail from the Suped guide.
- Treat a spike of about twice your normal volume as a reason to pause that segment.
Bounce rate is only half the picture. A low bounce rate with a high spam complaint rate still damages delivery, and Google asks senders to keep complaints below 0.1%. Our guide to why emails go to spam covers that side.
Questions about email bounce rate
What is a good email bounce rate?
Below 2% is the figure Amazon SES recommends, and the Suped guide calls under 2% healthy. Hard bounces alone should sit under 1%. These are sending platform and vendor guardrails, not thresholds published by Gmail.
How is email bounce rate calculated?
Divide bounced messages by attempted deliveries and multiply by 100. Count only messages handed to the delivery system, exclude pre-send suppressions, and count each message once by its final outcome instead of once per retry.
At what bounce rate does Amazon SES take action?
SES recommends staying below 2%. At 5% or greater it places the account under review, and at 10% or greater it might pause sending until the cause is fixed. It measures hard bounces to domains you have not verified.
Do soft bounces count toward bounce rate?
It depends on who is counting. Amazon SES leaves temporary failures such as a full mailbox out of its rate, while other guides track total, hard and soft rates separately. Retry soft bounces within limits, then suppress an address that keeps failing.
Does a policy rejection mean the address is invalid?
Not necessarily. A refusal for authentication or policy reasons, such as a DMARC failure, is a deliverability problem rather than a dead address. Check the bounce code before you suppress the address, or you may lose a valid contact.
Bottom line
Calculate the rate the same way every time, aim for under 2%, and treat a climb as a prompt to find the source rather than to send less. The published thresholds belong to specific platforms, so check the rules of the one you actually use.
Related reading
- Hard bounce vs soft bounce: telling the two apart and what each costs
- B2B email verification: cleaning a list before it bounces
- Why do my emails go to spam: the other half of deliverability
