When the delivery of an email to an email address is not possible, the email sever will return a message to the corresponding mail delivery system. This response is called a bounce. There is a distinction between soft bounces and hard bounces. A soft bounce is a rejection when the email address is only temporarily unreachable, e.g. when the inbox is full. A hard bounce happens when the email is permanently undeliverable, e.g. because the email address does no longer exist or the delivery was blocked by the mail server. Modern marketing automation solutions enable an automated bounce management which deletes hard bounce addresses as well as regular soft bounce addresses from the mailing list.