I am pretty sure that MIME::Lite does not allow you to distinguish between the envelope "mail from:" and the header "FROM: ", and there in lies your problem. According to the RFC, the DSN (delivery status notification) must go to the original sender (the envelope from and not the internal message header from). It is possible (perhaps not with MIME:Lite), to send a message with a different outside from than the inside from. I can't recommend a better package for you without knowing your and/or your client's needs.

Cheers L~R