There were several going around in the "warez" scene in the mid-90s.
It didn't require a script, either. When mailing lists and other automatic email sources let you add destination addresses without closing the confirmation loop by sending a test email, you can denial-of-service email addresses with just an SMTP client.
The really nasty part about this attack is that it's not just bandwidth amplification. Normal amplification attacks go away when the attacker decides to stop sending packets. With mailing subscriptions, the badly-configured mailing lists keep sending the attack on their own.