Greylist seletivo consultando blacklists

Para quem como eu não gosta de usar blacklists externos, essa
iniciativa é interessante:

http://code.google.com/p/gross


Gross is a greylisting server. The features that make gross stand out
from other greylisters are:

* it's blazingly fast
* it's amazingly resource efficient
* it can be configured to query DNSBL databases, and enforce
greylisting only for hosts that are found on those databases
* it can be replicated and run parallel on two servers
* It supports Sun Java System Messaging Server and Postfix