Process %1: %2 failed. The exception returned is %3. The remote server returned an error: 4%. The request information is 5%. The Availability service could not successfully retrieve Schedule+ free/busy data for one or more legacy Exchange mailboxes. To find the root cause of this error, increase the diagnostic logging level of the MSExchange Availability service.

This Error event indicates that the Microsoft® Exchange Availability service could not successfully retrieve Schedule+ Free Busy data for one or more legacy Exchange mailboxes. A legacy Exchange mailbox refers to a mailbox that resides on an Exchange 2000 or Exchange 2003 server. The Exchange Availability service is responsible for retrieving Schedule+ Free Busy data for a set of mailboxes. If the mailbox resides on a computer that is running Exchange 2007 Server, the Availability service retrieves the data from the mailbox itself. However, if the mailbox resides on Exchange 2000 or Exchange 2003 server, the Availability service retrieves the data from Public Folders. This event occurs when the Exchange Availability service does not retrieve the data from Public Folders.

The description of this event will usually include the URL to the target public folder and one of the following HTTP errors:

• 401   If you see this HTTP error, Integrated Windows authentication is probably disabled on the /public virtual directory. This is often the case when the Exchange 2007 Availability service tries to make a connection with the /public virtual directory in IIS on an Exchange 2003 Mailbox server, which is configured to use Forms-based Authentication (FBA). When FBA is enabled, all other authentication methods, including Integrated Windows Authentication, are automatically disabled.

• 403   If you see this HTTP error, the Client Access server may be offline, or it does not contain a replica. This error might also occur if Secure Sockets Layer (SSL) is enabled on the /public virtual directory of the Mailbox server that the Availability service is connecting to. This is typically true when Exchange 2003 Mailbox servers are configured to use Forms-based Authentication and when Exchange 2007 is deployed with both the Mailbox and Client Access server roles installed on the same computer. While connections between the Outlook client and the Availability service use HTTPS over port 443, connections between the Availability service and the /public virtual directory use HTTP over port 80.

• 404   This HTTP error can occur if the /public virtual directory was not found.

If you cannot resolve this error using the options suggested here, contact Microsoft Product Support Services. For more information, see the Troubleshooting Free/Busy Information for Outlook 2007 topic in Exchange Help.

If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.