Is every code unique? If not, you can use Outlook to automate the process. If they are unique, you could still use Outlook, but it would require making a new 'rule' for every listing you do. There's plenty of guides on the Internet that tell you how to do this. Its the only free option I can think of. The downside of this is, they will only be sent once you launch Outlook, or have it running.
If your prepared to put your hand in your pocket, then there's loads of software which will do it for you. But it does come at a price...