A hard bounce indicates a permanent reason an email cannot be delivered pertaining to the e-mail address information. They are e-mail addresses that cannot be reached due to such reasons as mistyped e-mail address, closed domain name, misconfigured e-mail or server that does not receive your e-mail technically.
A soft bounce, on the other hand, indicates a temporary reason. It is an email that reached the recipient’s mail server but bounced back before it made it to the recipient.
Hard bounce and soft bounce replies are sent by the e-mail server of the recipient as soon as you send the e-mail. Furthermore, these replies are reflected in your INBOX account reports.