I have a mail server that handles several domains. One of these domains has decided to use Postini. For those not familiar with Postini, you set your MX records to use their mail servers. They filter mail, and deliver you only the clean virus/spam free mail. The idea is to only allow incoming mail from their mail servers so spammers are unable to send to your mail server directly. This is fairly simple to do with standard restriction classes for a dedicated mail server. I am not sure how to accomplish this on a shared mail server. Ideally I would like to instruct postfix to accept mail from anywhere for all domains except one domain (the one using Postini) and only allow mail destined for that specific domain to originate from Postini's mail servers. Any ideas would be greatly appreciated.
Thanks, Barry