Spam rejected messages

I want to set up my spam filtering to reject messages that it thinks are spam. (This is on Mac OS X Server 10.4 -- latest). In the system I used on a different system, when it rejected a message, it would append why it was rejected and it would also allow the sender to add a "password" (which the appened text gave) and resend the message. If the spam filter saw the password it would allow the message to go through. With this system, if a human sent a message that the spam filter rejected, they knew it, knew why, and were told how to send the message again and have it not be rejected. I had a few grumbles from users but I felt safe knowing that messages were not being just rejected and the senders not know why or what to do about it. Does Spam Assassin with Mac OS X have this ability? I have not seen it described in the Mac OS X manuals and books. I'm assuming that I could bypass the stock Mac OS X set up and do this directly with Spam Assassin set up but I'm not sure where to start. Any help and advice would be appreciated. Thank you, pedz