Please do not do this.

People in our office were doing this and eventually one of the messages hits a mzilbos that is full, bad address, whatever. It sends back an error message, and your system sends out your message again. Over and over, thousands of messages until either your box gets full, or you crash your server.

I don't allow automatic replies from our server anymore because of this, it's a nightmare to track down, because restarting the server will only cause it to happen again. When they get to checking the outbound que, if they are smart enough, you will have thousands of messages in there lines up, and they won't be happy.