Settings to implement Dagon Design Secure PHP Mailer

I'm trying to set up a simple standalone page on my site to test the Dagon Design Secure PHP Form Mailer.

Ultimately, the goal is to help a local non-profit publication solicit photos from their aging readership.

At the moment, I get the "Error sending message!" error message when I try the form. In the comments for the form, the scripter says:

If you believe you can use the PHP mail function and have already tried a different email address, create a small PHP file with the following contents (be sure to use your own email address):

<?php mail('you@domain.com', 'test subject', 'test message'); ?>

Open the file in your browser and then check your mail. If you did not receive the message, something is not set properly on your server, and the trouble is not with this script. Even if other mail scripts work for you, that does not mean this one will, as there are several methods to send mail in PHP.

I've created this tiny file, here, but nothing happens when I open it in my browser (by typing the address directly into the address bar). I've obviously replaced the mail address in the little script with my own e-mail address.

I'm obviously still learning about this stuff, and probably will need to learn a lot more before I'm done. But for right now: is there something I should configure to make this little mail test script work?