Email bounce rate is the rate at which an email was unable to be delivered to a recipient’s inbox. A high bounce rate generally means your lists are out-of-date or purchased, or they include many invalid email addresses. In email, not all bounces are bad, so it’s important to distinguish between hard and soft bounces before taking an email address off your list. A hard bounce means there is a very high likelihood that the email address is no longer valid. A soft bounce means that the email may be valid but is temporarily not deliverable (full email box, etc.).