To: foo@example.com
Subject: multipart
Date: Sun, 01 Jan 2000 00:00:00 +0000
From: =?UTF-8?Q?"Peter M=C3=BCller"?= <peter-mueller@example.com>
Content-type: multipart/alternative; boundary="crazy-multipart"
MIME-version: 1.0

multipart message
--crazy-multipart
Content-type: text/plain

The first part 
is horizontal

--crazy-multipart
Content-type: text/x-vertical

T s p i v
h e a s e
e c r   r
  o t   t
  n     i
  d     c
        a
        l
--crazy-multipart--