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When a counter proposal message that uses iCalendar format is sent from a mail server that is not running Microsoft Exchange to a server that is running Exchange Server 2007, the recipient on the Exchange Server 2007 computer receives the following error message when the recipient tries to open the message in Microsoft Office Outlook 2007:
Cannot open this item. You must specify a time.
Note A counter proposal message is a response for a meeting request. The counter proposal message is typically used when you have tentatively accepted a meeting, and you want to propose a new time for a meeting request.
The non-Exchange mail system does not provide some Exchange-specific properties in the header of a counter proposal message, such as the start time or the end time. However, Exchange Server 2007 relies on these properties. If these properties are not available, the Exchange server displays the message incorrectly. Therefore, Outlook cannot open the message.
To resolve this problem, install Update Rollup 5 for Exchange 2007 Service Pack 1.
For more information about Update Rollup 5 for Exchange 2007 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:
953467 Description of Update Rollup 5 for Exchange Server 2007 Service Pack 1
For more information about Exchange iCalendar standards compliance, visit the following Microsoft Developer Network (MSDN) Web site: