The e-mail is a very interesting technology but also one of the areas of the Internet with more security flaws. I remember a 16 year old kid came up with a much better protocol but, for some weird reason, her ideas were dismissed and never implemented.

"So an email that does not reach its recipient is automatically returned with an error message. This implies that no message is playing ghost in the mail network cemetery."

Yeah, and that also happens when your ISP refuses to send an e-mail, even when the recipient's address is correct.