PHPMailer

When creating an e-mail that consists of a multipart/mixed Content-Type,
including a body part and one or more attachments, the Content-Type header
of the body part is set to multipart/mixed, when it should be set to
text/plain or text/html, depending on the actual type of the body part.

I've created a workaround that includes setting a new variable when calling
IsHTML(), and then checking that variable in CreateBody(), but I know there
is a better way. Suggestions are welcome until a real fix is in place.