Why closed?
See my followup - since your blacklist is public knowledge to both trusted folks and untrusted folks, you're giving up the very information that you don't want spammers to know: how to get past your filters.
What benefit to spammers get from seeing the list? They know their site is blacklisted and buy a new domain? It'll soon be blacklisted again, plus baysean (sp) filtering in Drupal may keep the new one off anyway.
One purchase from a piece of spam mail sent to 100,000 users creates enough profit to buy a new domain, yes, and when you can buy 'em for less than $10, this doesn't really scale. The cost is not prohibitive enough. -- Morbus Iff ( you are nothing without your robot car, NOTHING! ) Culture: http://www.disobey.com/ and http://www.gamegrene.com/ Spidering Hacks: http://amazon.com/exec/obidos/ASIN/0596005776/disobeycom icq: 2927491 / aim: akaMorbus / yahoo: morbus_iff / jabber.org: morbus