How do I automatically trigger email notifications?

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I want to be able to generate an automatic email when a candidates status is changed.   For example, when the status is changed from "offer accepted" to "employed" or from "Final Interview" to "Generate Offer".   Each status change generating an appropriate email.  

I see in admin how I can create the email, however I do not see how a status change automatically triggers this email being sent.   Can I do this?  How?