The reasonable thing to do is just block everything from their domain or that includes their name.
However that's no fun. What is fun is whipping up a python script and using a service like Tropo to respond to every single message with a phone call to tell them that the email is unwanted. Of course, to ensure that they can effectively identify the offending mail, the script should read it to them in it's entirety and ask them to press a button to acknowledge that they've understood and will stop. If the call gets... disconnected for any reason, it should call back and start over until it gets it's acknowledgement.