title: Multipart email with text and calendar: Outlook doesn't recognize ics
body: <p>I have problems with Outlook 2007. When sending a "multipart/alternative" email with a "text/calendar" part, Outlook recognizes the calendar event, that's how it has to be.
  But when adding a "text/plain" part, Outlook only displays the plain text, the calendar part is missing (but it's present in the source code of the email).</p>
  
  <p>The source looks like this:</p>
  
  <pre><code>[...]
  Content-Type: multipart/alternative;
  boundary="_=_swift_v4_138243630552664dd1bc83e_=_"
  
  --_=_swift_v4_138243630552664dd1bc83e_=_
  Content-Type: text/plain; charset=utf-8
  Content-Transfer-Encoding: quoted-printable
  
  [...the plain message...]
  
  --_=_swift_v4_138243630552664dd1bc83e_=_
  Content-Type: text/calendar; charset=utf-8
  Content-Transfer-Encoding: quoted-printable
  
  BEGIN:VCALENDAR
  VERSION:2.0
  PRODID:-//GourmetPortal//NONSGML rr//DE
  BEGIN:VEVENT
  UID:res-Burkert
  CREATED:20131030T113000Z
  ORGANIZER;CN=3DSven Burkert:MAILTO:[...]
  SUMMARY:[...]
  DESCRIPTION:[...]
  DTSTART:20131030T113000Z
  END:VEVENT
  END:VCALENDAR
  
  --_=_swift_v4_138243630552664dd1bc83e_=_--
  </code></pre>