I'm running a PHP page; the on screen results are fine, but it's supposed to be sending an email .... but that email isn't being received.   Any suggestions?

I would suggest that you start by splitting the problem in two - stage one is to check out the email from the command line [I happen to know that you're running on a system running a Unix derivative and should have a local SMTP daemon].   If you can't send emails from the command line, have a look at the sendmail configuration files ... and you might also like to see if you're sitting behind a firewall that doesn't allow your local SMTP client to connect in to the next SMTP server up the line.

Let's suppose that email is working from the command line, but still not from the PHP.  .... run a page with a call to the phpinfo function in it, and look at where the PHP is sending its email
requests, and how.    The three parameters to look at are:
    sendmail_from
    sendmail_path
    SMTP
You'll probably want to fix these via php.ini as they'll be server-wide.

Still not working, even though you can mail from the command line?  Check your PHP and make sure the from address is correct  

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