Soft bounce rate refers to the percentage of email messages that are not delivered to the intended recipient due to temporary issues, such as a full inbox or a server error. Unlike a hard bounce, which indicates a permanent delivery failure, a soft bounce can occur when the recipient’s email address is valid but the message cannot be delivered at that moment. This can be caused by a variety of factors, including technical problems or the recipient’s email server being down. A high soft bounce rate can indicate issues with email deliverability and may require further investigation to ensure successful communication with recipients.