Answer 1

A soft bounce means that the email address was valid and the email message reached the recipient's mail server. However, it bounced back because: The mailbox was full (the user is over their quota) The server was down. The message was too large for the recipient's inbox

 A hard bounce is an e-mail message that has been returned to the sender because the recipient's address is invalid. A hard bounce might occur because the domain name doesn't exist or because the recipient is unknown.