What is Hard Bounce?
A hard bounce is the failed delivery of an email. It indicates a permanent reason an email cannot be delivered. Hard bounces
immediately and automatically remove active subscribers email addresses that will not be included in future marketing campaigns. Common reasons email addresses may hard bounce include a non-existent recipient email address, the Domain name does not exist, or the recipient email server has blocked delivery. Other causes for a hard bounce include an obsolete mailbox, incorrect destination or sender address, message or mailing list length, or routing and connection failures.