A bounce email, also known as a bounce-back or non-delivery report, is an automated message sent to the sender of an email when it is unable to be delivered to the intended recipient. This can occur for various reasons, such as an invalid email address, a full inbox, or a server error. Bounce emails serve as a notification to the sender that their message was not successfully delivered and may include information on why it was bounced. They are commonly used to help manage email delivery and ensure that important messages reach their intended destination.