If this had been sent properly, the list of email addresses would have been in the Bcc field rather than the To field. If that had been the case, it looks like the Bcc addresses would not have been included in the "--original message--" body of the bounced email.
In general, is it best to...
The eMail Bounce Handler processed a single bounced message and added several legitimate email addresses to my list as "hard bounces."
The original message was sent to multiple people, only one of which was a bad address. The bounced reply "Delivery Status Notification..." included the...