From: John Doe <example@example.com>
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary='XXXXboundary_text'
--XXXXboundary_text
Content-Type: text/plain
this is the body text
--XXXXboundary_text
Content-Type: text/plain
Content-Disposition: attachment;
filename='test.txt'
this is the attachment text
--XXXXboundary_text--