This example has a Send Result field where the Results are shown. This is where the plug-in can give you feedback on what it is doing. If an error occurs, it will report the error in the results field which can help you fix any issues you may be having. It will also report its successes so that you know everything is going as planned. If you have "Get Transcript" set to true on the settings layout, you will also see the interaction between SMTPit Pro and your mail server in the Result field.
Take a look at this article.