Hello, I would like to develop a SPAM fighting extension of the Thunderbird email client. On the contrary of existing plugins, this new plugin would allow each end-user to report SPAM directly to the right ISP instead of delegating it to a centralized service. This solution distributes the cost between all the spam reporters. For that, I need to know which ISP hosts a given IP. Of course, I can write a wrapper of the http://www.db.ripe.net/whois portal. However I'm searching a more efficient way. For example, we could use a compressed database file on ripe.net (or on bittorrent network) and local caching on each email client. I would like to discuss this with the list and provide the most efficient solution for everyone. Thanks for your advise. Regards.