Ahh! bounce e-mails. Still confused about that one? No problem, it’s really something that doesn’t hold interest until you get a message in your inbox saying a certain e-mail is “undeliverable” and has therefore “bounced.”
Simply put, bounce e-mail is electronic mail that gets returned to the sender because it cannot be delivered for one reason or another. It’s like a check that can’t be cashed in.
Hard bounce e-mail is an e-mail that is cannot be delivered permanently. This can be because the address is invalid. Soft bounce on the other hand happens when the recipient’s inbox is full and has no capacity to include yours. Or to be less harsh, if the server is temporarily unavailable.