“A soft bounce is a temporary deliverability problem, such as a full inbox or a server that is down. It’s okay for you to resend emails to these addresses because there is a good chance they will go through on the second or third attempt. A hard bounce is a permanent deliverability problem, such as an invalid email address.”
Stay abreast of email bounce rates, something considered essential in email list management. You’ll improve your ROI if you continually avoid sending emails to addresses that bounce back. Don’t worry about figuring out every bounce code, simply manage hard and soft bounces alike.