Well don't send messages to a list from an address that you don't want to receive responses to... After sending an offlist response:
This is probably because this is an internal account that no one is supposed to be sending mail to. If you are sending it mail, you are probably a low-life, bottom feeding scum sucking spammer who will burn in hell. NO addresses at this domain EVER want to hear from you.
What part of that don't you understand?
<nanog@adns.net>: Message rejected by recipient.
I believe this particular case has been brought to the attention of the list before, no? That said, I remember hearing that Level3 tried not to do the smaller stuff directly, but that situation may be different now. -- "Since when is skepticism un-American? Dissent's not treason but they talk like it's the same..." (Sleater-Kinney - "Combat Rock")