title: Outlook shows email html as though it were plain text, too many line breaks
body: <p>I can generate emails in php and send them so that they are correctly shown as html in Gmail and Apple mail and other client.
  I also do not get any formatting errors from spam assassin.</p>
  
  <p>However, one receiver using Outlook 14 on Mac OS X receives the emails as though the html part were plain text. The same thing happens if I disable spam assassin on his hosting account. Here is the source of such an email when it is received by the user (edited to remove domain names and email addresses and shorten the message body):</p>
  
  <pre><code>Return-path: &lt;_www@[domain].com&gt;
  Envelope-to: info@[domain].com
  Delivery-date: Tue, 29 Jul 2014 01:39:03 -0700
  Received: from [domain].com ([212.85.69.251]:50283)
  by biz61.inmotionhosting.com with esmtp (Exim 4.82)
  (envelope-from &lt;_www@[domain].com&gt;)
  id 1XC2w3-0003s4-C7
  for info@[domain].com; Tue, 29 Jul 2014 01:39:03 -0700
  Received: by [domain].com (Postfix, from userid 70)
  id 693E248D80BC; Tue, 29 Jul 2014 10:39:02 +0200 (CEST)
  To: info@[domain].com
  Subject: test2 - ignore - Link
  From: Action Sports &lt;noreply@[domain].com&gt;
  Reply-to: [my-email]@[domain].com
  Cc: [my-email]@[domain].com
  Sender: info@[domain].com
  MIME-Version: 1.0
  Content-Type: multipart/alternative; boundary=c4d5d00c4725d9ed0b3c8b
  Message-Id: &lt;20140729083902.693E248D80BC@[domain].com&gt;
  Date: Tue, 29 Jul 2014 10:39:02 +0200 (CEST)
  
  --c4d5d00c4725d9ed0b3c8b
  
  Content-type: text/plain; charset=utf-8
  
  
  testing - ignore
  
  
  
  
  
  --c4d5d00c4725d9ed0b3c8b
  
  Content-type: text/html; charset=utf-8
  
  
  
  &lt;html&gt;&lt;head&gt;&lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
  &lt;style TYPE="text/css"&gt;
  &lt;!--
  table{
  border-collapse:collapse;
  border:1px solid #888;
  }
  
  table td, table th{
  border:1px solid #888;
  padding:3px;
  }
  --&gt;
  &lt;/style&gt;&lt;/head&gt;
  &lt;body&gt;
  
  testing - ignore 
  &lt;br&gt;
  
  
  
  &lt;/body&gt;
  &lt;/html&gt;
  
  
  
  --c4d5d00c4725d9ed0b3c8b--
  </code></pre>
  
  <p>Here is what Outlook displays as the human readable content of the mail when opened normally in a new window:</p>
  
  <pre><code>[ at the top is the normal outlook header, followed by the following blank line: ]
  
  Content-type: text/html; charset=utf-8
  
  
  
  &lt;html&gt;&lt;head&gt;&lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
  &lt;style TYPE="text/css"&gt;
  &lt;!--
  table{
  border-collapse:collapse;
  border:1px solid #888;
  }
  
  table td, table th{
  border:1px solid #888;
  padding:3px;
  }
  --&gt;
  &lt;/style&gt;&lt;/head&gt;
  &lt;body&gt;
  
  testing - ignore
  &lt;br&gt;
  
  
  &lt;/body&gt;
  &lt;/html&gt;
  
  
  
  [the message ends with about 4 empty lines]
  </code></pre>
  
  <p>If I send the same email to my Gmail account, it looks ok and has less empty lines if I view the source.</p>
  
  <p>I now believe the extra empty lines are causing outlook to misunderstand that the last part is supposed to be displayed as HTML. What is causing the extra empty lines?</p>
  
  <p>Am I supposed to use <code>\r\n</code> line breaks in the header but <code>\n</code> line breaks in the message body?</p>