title: php formatted html shows up in Yahoo mail but not gmail
body: <p>I am using MAMP (LAMP stack development environment) to send emails using PHP.</p>
  
  <p>The code is below:</p>
  
  <pre><code>$out_message = '
  &lt;html&gt;
  &lt;head&gt;
  &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /&gt;
  &lt;title&gt;You have requested an appointment with the Smile Zone&lt;/title&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
  &lt;p style="font-family:Arial, Helvetica, sans-serif;"&gt;&lt;strong&gt;Dear '.$details_name.'&lt;/strong&gt;&lt;/p&gt;
  &lt;p style="font-family:Arial, Helvetica, sans-serif"&gt;You have requested an appointment!&lt;/p&gt;
  &lt;p style="padding:10px;"&gt;&lt;strong&gt;Please note that this appointment is currently unconfirmed&lt;/strong&gt;&lt;/p&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  ';
  
  //now for the client side:
  $out_to = 'john@gmail.com';
  $out_subject = 'My Subject';
  
  // To send HTML mail, the Content-type header must be set
  $headers  = 'MIME-Version: 1.0' . "\r\n";
  $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
  
  // Additional headers
  $headers .= "To: John &lt;john@gmail.com&gt; \r\n";
  $headers .= 'From: The Smile Zone &lt;noreply@smile-zone.com&gt;' . "\r\n";
  
  $success2 = mail($out_to, $out_subject, $out_message, $headers);
  </code></pre>
  
  <p>When I send this email and view in Apple Mail, it appears as it should, however in GMail, in the browser all I get is the raw source.</p>
  
  <p>Why is this?</p>