Bounce / bounce rate
A bounce is when an email cannot be delivered; bounce rate is the share of emails that bounce.
Email & DNS~1 min read
In plain English
When an email doesn’t get delivered (bad address, full inbox, or block), that’s a bounce. A high bounce rate hurts your sender reputation and can get you blocked.
A bounce occurs when a message cannot be delivered to the recipient. Hard bounces (invalid address, domain doesn’t exist) are permanent; soft bounces (inbox full, temporary failure) may succeed on retry. Bounce rate is the percentage of sent emails that bounce.
High bounce rates signal to providers that your list or practices may be poor, which can lead to more spam filtering or blocking. Validating addresses and keeping lists clean helps keep bounce rates low.