You’ll find instructions on how to set your invites to auto-confirm in this <a href=”http://oit.utk.edu/exchange/faq/faq_outlook_calendar.php#Outlook_2003_273″>Outlook 2003 Calendar FAQ</a> (see response 8 under the Outlook 2003 section). I would suggest following these steps to turn off this feature.
If you set up a mailbox to automatically process the meeting invites, an actual acceptance email is not sent. Instead the user will get a pop-up saying “your meeting was successfully booked.” Either you set it up to automatically process so users get this pop-up confirmation, or you tell it not to automatically process and someone will have to go in and manually process all meeting invites which will send a confirmation email. There is no automatic process option that does not send the pop-up. This is a feature you cannot change.