I'm not an authority in the area of message encodings
for email-based services since I have no first-hand experience
with such, but I think you should look at multipart/report
(e.g., from RFC 1892, 1894) as background for notification.
Internet Fax uses multipart/report in delivery status notifications
and message disposition notifications as a way of reporting
the status of a fax back to the sending user.
It might be advantageous to use a similar or even compatible
mechanism for delivering back 'print status' to someone who
invokes a remote print job.