I have worked with Outlook since 2000 and have not seen a way that you can selectively send read receipts to people unless you do it on a per message basis. I have a Office Resource book and was unable to find any mention of being able to do this. It is either off, on, or per message. I would suggest some memory exercises for your user =)
Also, Outlook receipts only work if you send mail to another Outlook using client.