Hard bounce is a concept used in email marketing to describe the result of an attempt to deliver an email to a specific recipient. It is a bounce rate, which differentiates from the soft bounce.

A hard bounce occurs when the email address is non-existent, invalid or misspelled. These are usually permanent errors so it is important to constantly review email lists to maintain their quality and avoid sender reputation issues. The metric that measures the proportion of emails that bounce is called Bounce Rate.