A soft bounce is an e-mail message that gets as far as the recipient's mail server but is bounced back undelivered before it gets to the intended recipient. A soft bounce might occur because the recipient's inbox is full. A soft bounce message may be deliverable at another time or may be forwarded manually by the network administrator in charge of redirecting mail on the recipient's domain. On the other hand, a hard bounce is an e-mail message that has been returned to the sender because the recipient's address is invalid.
See bounce e-mail .