Smart temporary mail address

NTT Develops "privango" e-mail System
as Junk Mail Countermeasure (press release):
http://www.ntt.co.jp/news/news04e/0411/041129.html

Expiration date, sender's address and/or sender's domain is encoded in a mail address. NTT says these conditions are *encyrpted* in a address, but I'm not certain. It seems that the length of addresses is not enough for such conditions.

This is my temporary mail address that expires on Jan 1th, 2005:
shibaten.uvh3y5d5rbykodc@privango.jp