You send a meeting request to external recipients in a Microsoft Exchange Server 2007 environment.
You have the Reminder feature turned off.
In this scenario, the external recipients receive the meeting request with the Reminder feature turned on. Therefore, the reminder unexpectedly notifies the recipients of the meeting at the default of 15 minutes before the meeting starts.
By default, outgoing meeting requests are converted to iCal items. During this conversion, Exchange Server 2007 incorrectly resets the default reminder, even if you have the Reminder feature turned off.
To resolve this problem, install the following update rollup:
971534 Description of Update Rollup 1 for Exchange Server 2007 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.