I need to do both some light and heavy mail processing with Postfix, and I'm no expert at all, so before hiring someone to implement this, I want to understand more about it.
One the one hand I need to implement a blacklist to "quarantine" all incoming mail from certain senders. I think this can be implemented with a simple milter with a database/file backend.
By quarantine, I mean e-mail matching the blacklist will be forwarded to another Postfix instance in the same server.
Then, mail needs to be processed with some specific rules, like "given a specific sender, add some text to the subject", and so on.
After that, some bayesian processing needs to take place (I'm not exactly sure, but I believe this will be the intensive part).
Finally, the mail will be forwarded elsewhere.
As I said, I know next to nothing about the subject, but I'm thinking I'll need three Postfix instances, (1) for main receiving, (2) for quarantined mail, (3) for the fully processed mail that's ready to be forwarded.
Edit: I'm considering 3 instances because the main one needs to be able to receive thousands of e-mails for thousands of recipients without choking, but if content filters are fast enough, maybe I only need 2 (the quarantine one is required because it will be eventually moved to another machine)?.
Any thoughts on the process? Recommended libraries/programs?