Internet e-mail also is unauthenticated, which means anyone can send messages pretending to be someone else. This forgery is so astonishingly easy that it's amazing that no one has come up with a way to prevent it. Most mailing lists are managed by programs. You're on the list. Imagine if someone collected e-mail addresses from mailing lists and subscribed those people to other mailing lists.
Some mailing lists are high volume, with dozens or even hundreds of messages a day.
If this happened to you, you would probably receive a thousand messages or more every hour. If the attacker planned his attack for late night on a Friday, he would create maximum damage as people slept while their mailboxes filled up. This technique is a great weapon because you not only infuriate the folks you target, you clog up, slow down, and possibly stall access lines. Once the mailboxes start to fill up, things get even worse. Mail starts bouncing back, and some mailing lists go into an infinite loop, forwarding bounced mail, which bounces back, and so on.