You receive a "The messaging interface has returned an unknown error " error message when you try to use Outlook to make a change to a recurring appointment in the Calendar of your Hotmail account or of your MSN e-mail account

When you try to use Microsoft Outlook to make a change to a recurring appointment in the Calendar of your Hotmail account or of your MSN e-mail account, you receive the following error message:If you try again to make the change to the recurring appointment, you then receive the following error message:Additionally, if you close the appointment and do not save the change, the change appears in the Calendar of your Hotmail account or of your MSN e-mail account in Outlook. However, the change does not appear in the Calendar when you use your Web browser to open your Hotmail account or your MSN e-mail account.

This issue occurs when you try to make a change to a single occurrence of a recurring appointment. This issue does not occur if you make the change to all occurrences of a recurring appointment.

When only one occurrence of a recurring appointment in the calendar is changed, the change is referred to as an "exception." Exceptions are not supported in the current version (1.5) of the Microsoft Office Outlook Connector. Although the change is reflected in the Calendar view in Outlook, the change is not sent to the Hotmail e-mail server or to the MSN e-mail server.

Note This problem does not occur when you use a Microsoft Exchange Server account. This issue is limited to Hotmail accounts and to MSN accounts.