title: Fix MIME_HTML_ONLY on email template
body: <p>I'm trying to fix <code>MIME_HTML_ONLY</code> to pass some spam filter, the email is sent from a php project and I use this  template</p>
  
  <pre><code>&lt;html&gt;    
      &lt;table width="100%" style="font-family: Verdana; color: #707070" cellpadding="0" cellspacing="0"&gt;
          &lt;tr&gt;
              &lt;td&gt;
                  &lt;table width="643" align="center"&gt;
                      &lt;tr style="text-align: center"&gt;
                          &lt;td style="padding: 0 20px;"&gt;
                              {% block top %}{% endblock %}
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr style="background-color: #005aff; text-align: center;"&gt;
                          &lt;td&gt;
                              &lt;img src="https://www.mydomain/dist/imgs/cabecera.png"  atl="cabecera-encueston" style="width: 643px; height: 100px;"&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td style="padding: 0 20px;"&gt;
                              {% block content %}{% endblock %}
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      {% if external is defined %}
                      &lt;tr&gt;
                          &lt;td style="padding: 0 20px;"&gt;
                              &lt;p style="text-align: left; font-size: 14px; color: #707070;  padding: 20px 20px 0; margin: 0; font-family: Arial, Helvetica, sans-serif;"&gt;
                                  Un saludo,&lt;br&gt;
                              &lt;/p&gt;
                              &lt;img src="https://www.mydomain/dist/imgs/firma.png" atl="firma" style="width: 643px; height: 100px"&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td style="padding: 0 20px;"&gt;
                              &lt;img src="https://www.mydomain/dist/imgs/siguenos.png" alt="siguenos" style="width: 643px; height: 56px"&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      {% endif %}
                      &lt;tr style="color: #ccc; text-align: center;"&gt;
                          &lt;td style="padding: 0 20px; text-alig: center;"&gt;
                              {% block footer %}{% endblock %}
                              &lt;p style="font-size: 12px;"&gt;&amp;copy; Encuestón S.L.&lt;/p&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                  &lt;/table&gt;
              &lt;/td&gt;
          &lt;/tr&gt;
      &lt;/table&gt;
  &lt;html&gt;
  </code></pre>
  
  <p>,
  I'm not sure to fix <code>MIME_HTML_ONLY</code> issue,I've to change the solution is "You should also includea text version of your message (text/plain)"  but how?</p>