Thanks for the suggestion. I tried your suggestion but the Outlook calendar still wasn't displaying appointments properly, so I expect that's why it still didn't update Outlook properly.
The problem is that Outlook is confused. When viewing the calendar, dates are bolded for appointments that were created in the original mailbox (blackberry email address). When you click on the bolded dates, no appointment details (description, time, etc) are displayed for that date.
Since I've changed the default service to my own domain. In Outlook, for any newly created appointments, none of the calendar dates are in bold. But when I do click on the date of the appointment, it at least shows the appointment details.
On the device, all appointments appear ok. The problem is that appointments are not displaying properly within Outlook anymore. Any other suggestions?