title: Relaying not allowed message when sending mail with PHP function
body: <p>I'm using wamp server and trying to send email with the PHP function <code>mail('me@ISPdomain.com','my subject','my body');</code> ,<br>
  with the following settings in <code>php.ini</code>:  </p>
  
  <pre><code>SMTP = 'ISP's SMTP server'  
  smtp_port = 25 
  </code></pre>
  
  <p>But I get the message:  </p>
  
  <pre><code>Warning: mail() [function.mail]: SMTP server response: 550 5.7.1 Relaying not allowed. Please use SMTP Authentication.
  </code></pre>
  
  <p>How can this be solved?</p>