There were two problems here.
* The $msgdata->fullmessage was always formatted as HTML even if the
$msgdata->fullmessageformat was set to the original template's format.
* The plain text part of the emailed message contained HTML code.
The patch makes sure that the original template is always formatted into
HTML and then converted to plain text before setting the text/plain
multipart of the sent email.
Andrew Nicols