A hard bounce is a permanent delivery failure, often due to an invalid address. Learn common causes of hard bounces and how to handle them.
A hard bounce is a permanent email delivery failure. It usually means the address does not exist, the domain is invalid, or the receiving system has a permanent block that prevents delivery.
Hard bounces are particularly harmful if you keep sending to the same addresses because they signal poor list quality to inbox providers. Most sending systems recommend suppressing hard-bouncing addresses immediately.
To reduce hard bounces, validate addresses at collection time, use double opt-in where appropriate, and regularly clean lists. If hard bounces spike suddenly, check recent list sources and confirm that your domain authentication and sending setup haven’t changed.