title: send_mass_emails with EmailMultiAlternatives
body: <p>I try to build a newsletter application and want to send 50 emails with one connection. <strong>send_mass_mail()</strong> looks perfect but I can't figure out how I call this in combination with EmailMultiAlternatives.</p>
  
  <p>This is my code that sends only one email with one connection:</p>
  
  <pre><code>html_content = render_to_string('newsletter.html', {'newsletter': n,})               
  text_content = "..."                      
  msg = EmailMultiAlternatives("subject", text_content, "from@bla", ["to@bla"])                                      
  msg.attach_alternative(html_content, "text/html")                                                                                                                                                                               
  msg.send()  
  </code></pre>
  
  <p>a working example with the code above and send_mass_mail would be great, thanks!</p>