I think Sam's approach of generating a "corrupted message" report and attaching the original mail as a file is perfectly alright. What I want to try is to change the content-type of the attached message into "message/rfc822". Most mail clients can handle this mime type and just open a new message window for the attached message.
No can do. A MIME content type of message/rfc822 must be a valid MIME
message. And we already know it's not.