Email bounce rate measures messages that could not be delivered, while unsubscribe rate measures recipients who opt out of future marketing messages. Both help reveal list quality, delivery problems and mismatches between subscriber expectations and campaign content.
Bounce rate #
Bounce rate = Bounced emails ÷ Emails attempted or sent × 100, using the provider’s stated denominator. If 40 of 2,000 attempted messages bounce, the rate is 2% when attempted sends are the denominator.
Hard and soft bounces #
A hard bounce generally indicates a permanent problem, such as an invalid address. A soft bounce is usually temporary, such as a full mailbox or temporary server issue. Provider definitions and retry policies differ; follow the sending platform’s instructions and suppress addresses when appropriate.
Unsubscribe rate #
Unsubscribe rate = Unsubscribes ÷ Delivered emails × 100, if delivered emails are the chosen denominator. For 10 unsubscribes from 2,000 delivered emails, the rate is 0.5%. State the denominator in reports because tools may calculate the metric differently.
How to diagnose changes #
- Check whether list sources or sign-up practices changed.
- Review frequency and whether content matches the promise at sign-up.
- Inspect subject lines and campaign relevance.
- Check authentication, domain reputation and provider rejection messages when bounces rise.
- Honor unsubscribe requests promptly and keep suppression records reliable.
Do not hide the signal #
Removing an unsubscribe link or making it difficult to opt out harms trust and may violate applicable rules. An easy unsubscribe process helps ensure that the list reflects people who still want the messages.
Example #
If bounce rate rises after importing a new list, pause further sends to that source and investigate consent, address quality and collection methods. If unsubscribes rise after a change in frequency, compare subscriber expectations and the value of recent content.
FAQs #
Is every soft bounce permanent? #
No. Some are temporary, but repeated failures should be handled according to provider rules.
Is an unsubscribe always a bad result? #
Not necessarily. It can reflect a preference change and helps keep the audience aligned with the content. A sudden increase, however, deserves investigation.
Conclusion #
Bounce and unsubscribe trends are useful diagnostics for list quality and relevance. Pair them with Email Deliverability Fundamentals and Email Lists and Permission-Based Marketing.
