Definition
Bounce rate: The share of sent messages that were rejected by the receiving server, usually reported separately for hard and soft bounces. A hard bounce rate under 2% per send is the common ceiling, and a well kept list stays under 1%.
How to calculate email bounce rate
Divide bounces by messages sent, for one campaign or over a rolling window. If you send 10,000 messages and 150 hard-bounce, your hard bounce rate is 1.5%.
Platforms define the inputs differently. Some divide by sent, some by delivered plus bounced, and many count only hard bounces toward the account rate. Amazon SES, for example, counts hard bounces and leaves out temporary failures. Check your own platform's definition before comparing numbers.
What a high bounce rate does to deliverability
Mailbox providers see a wave of unknown-user rejections as the signature of an old, bought or scraped list, and they filter the rest of your mail more strictly. That hits every recipient, including the good ones.
Sending platforms enforce their own limits. Amazon SES places an account under review at a 5% bounce rate and can pause sending at 10%, and other platforms run similar internal checks.
How to lower your bounce rate
Verify addresses where they enter: at the signup form, at import and before the first send to any new list. Re-verify any segment you have not mailed in a few months, because addresses die on their own.
Suppress every hard bounce immediately, and treat repeated soft bounces from the same address as a hard bounce. Never re-import an old file over your suppression list.
How RocketVerifier handles it
Verify a list before a send and every address marked deliverable is backed by our bounce guarantee. Connect SendGrid, Mailgun, Amazon SES or Postmark and every hard bounce of an address a job marked deliverable within 30 days is refunded automatically, 1 credit each, and the address is added to your suppression list. Without a connected platform, file a claim from the job page and get 1 credit back for every bounce above 4% of the job's deliverable addresses within 30 days.