cb0ba762_BrotherMailer___Glossary__Definition
[Term] Bounce backs [Definition] 
An email that never arrives in the recipient's inbox. The email is sent back, or bounced back, to the sender with an error message. There are two types of bounce back: 1) Soft bounce is used to describe an e-mail that has bounced back to the sender undelivered after it has already been accepted by the recipient's mail server. 2) Hard bounce is used to describe an e-mail that has bounced back to the sender undelivered without having been accepted by the recipient's mail server.
BrotherMailer - Glossary
Definition