Behavioral methods: greytrapping

greytrapping: they send to junk addresses

Pioneered by Bob Beck and the OpenBSD spamd team

  1. Create a list of bogus addresses

  2. Any IP address which sends mail to known bogus addresses get blacklisted for 24 hours

    Blacklisted hosts get e-x-t-r-e-m-e-l-y s-l-o-w SMTP responses

Shifts the load back to the sender