PHP / Cronjob mail function

I have a website on the Internet and I want to use CronJob to send newsletters every Monday. Now I am using PHP for this and I am stuck. I have a mail () function that sends mail to every address in the file.

Here is my CronJob file. I changed the date to every day, just for debugging.

0 9 * * *   php -f /home/a4770799/public_html/mail/newsletter.php

      

        
        
        
      

    

Here is my PHP file. This is the whole file.

<?php
  $subject = "Weekly Newsletter";
  $msg = "This is a weekly newsletter debugging test.";
  $headers = "From: noreply@test.com" . "\r\n" .
             "Reply-To: example@test.com" . "\r\n";
  $linesofmail = file("mail_address_list.txt");
  foreach ($linesofmail as $line_num => $line) {
    mail ($line, $subject, $msg, $headers);
  }
?>

      

        
        
        
      

    

What could be the problem? I would love it if someone could explain this problem to me and not just give me the code.