Hackish way of referring to the postal service, analogizing it to a very slow, low-reliability network. Usenet sig blocks sometimes include a “Paper-Net:” header just before the sender's postal address; common variants of this are “Papernet” and “P-Net”. Note that the standard netiquette guidelines discourage this practice as a waste of bandwidth, since netters are quite unlikely to casually use postal addresses. Compare voice-net, snail-mail.