mail function -- not functioning for me!

PHP 4.0.1pl2 Mac OS X 1.2 Apache 1.3.12 I have been trying to get a simple mail function to work with PHP -- I want to use it to create a feedback form, eventually. I copied the code from a book, and they say it should work. But, of course, it is not. the actuall code will follow, but I don't think it's an error in the code, because when I put a deliberate error in, php DOES generate an error message for me. Otherwise, no error messages. I think the problem lies in the interaction between PHP and sendmail. The server tells me sendmail is in /usr/sbin and that it is running. This is the path I put in the php.ini, on the "sendmail_path =" line. This line is not commented. I have tried various e-mail send-to addresses, just in case. I know PHP is tracking vars, because it displays the "thank you" message correctly. I also, therefore, know that is not a problem of file location, etc. **CODE FOR HTML FORM** <HTML> <HEAD> <TITLE>Feedback</TITLE> </HEAD> <BODY> <FORM method="POST" action="/php/sendfeedback.php"> <P>Your Name:<br> <INPUT type="text" name="sender_name" size=30></p> <P>Your E-Mail Address:<br> <INPUT type="text" name="sender_email" size=30></p> <P>Your Message:<br> <textarea name="message" cols=30 rows=5></textarea> </p> <INPUT type="submit" value="Send This Form"> </FORM> </BODY> </HTML> **END OF HTML CODE** **CODE FOR PROCESSING SCRIPT** <?php $msg = "Sender's Full Name:\t$sender_name\n"; $msg .= "Sender's E-Mail:\t$sender_email\n"; $msg .= "Sender's Message:\t$message\n\n"; // use two newline characters at the end of your content, // or to insert additional spacing $mailheaders = "From: ASD Web Site <> \n"; $mailheaders .= "Reply-To: $sender_email\n\n"; mail("turnbull@enol.com", "Feedback Form", $msg, $mailheaders); echo "<H1 align=center>Thank You, $sender_name</h1>"; echo "<p align=center>We appreciate your feedback.</p>"; ?> **END OF PHP SCRIPT** Any ideas? Dave