Email bounce rate is the percentage of your sent messages that bounced. It is the first of the two numbers AWS reviews your Amazon SES account on. The other is the complaint rate.
How it is calculated
AWS counts only hard bounces, and only those to domains you have not verified. Temporary failures such as a full mailbox, and bounces caused by blocked IP addresses, do not count. Bounces SES generated because an address was already on your suppression list are left out as well.
AWS also does not use a fixed period. It looks at what it calls a representative volume, so a rate worked out from your own counts will not always match its figure. See soft bounces for what stays out of the rate.
The SES thresholds
| Bounce rate | Complaint rate | |
|---|---|---|
| Account put under review | 5% | 0.1% |
| Sending can be paused | 10% | 0.5% |
These are the figures AWS documents. Check the current AWS documentation before you rely on them, since AWS can change them. AWS recommends staying below 5% on its reputation page, and its enforcement FAQ advises below 2% for best results. Treat the review line as an emergency and aim to stay well under it. See SES account review for what happens when you cross it.
What pushes it up
- A list that was bought, scraped or left untouched for years.
- Sign-up forms that accept typos.
- Sending to old inactive addresses after a long gap.
- A new sender, or a new domain, with little history.
Bringing it down
Confirm addresses with a double opt-in. Remove hard bounces at once, which SES does by default through the suppression list. Retire addresses that have not engaged in a long time. After a change to your sending, such as a new list or a new product, watch the rate for the first day rather than the first month.
A rate that is a fraction of a percent most days and climbs for an hour is easy to miss on a dashboard you open once a week. That is the case for alerts over charts.
Common questions
What is a good bounce rate for email?
As low as you can get it. AWS reviews at 5%, but a well-kept list bounces far less than that. Treat 5% as the point of trouble, not the target.
Does website bounce rate mean the same thing?
No. A website bounce is a visitor who leaves after one page. An email bounce is a message that could not be delivered. The two have nothing to do with each other.
Why does my SES bounce rate differ from another tool's?
Tools differ in what they count and over what period. AWS counts only hard bounces to domains you have not verified, over a representative volume rather than a fixed period, and says you cannot reproduce its figure from CloudWatch send and bounce counts.