Comercial Solutions

If you're willing to spend a small amount of money, we highly recommend Postini . For about $1 per mailbox per month, they will filter your email upstream and only send you the mail that passes through. This is configured by publishing them as your MX, and then you configure your firewall to only let SMTP connections through if they originate from Postini's network. This means, you will have experts care for your spam problem.