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On a Microsoft Exchange Server 2007 server, after you set the value of the CalendarItemRetrievalOption parameter to Custom for the IMAP4 service, you may find that the IMAP4 service crashes intermittently. When this problem occurs, all IMAP clients cannot access their mailboxes. Additionally, the following error message is logged in the event log:
Event Type: Error Event Source: MSExchange Common Event Category: General Event ID: 4999 Description:Watson report about to be sent to dw20.exe for process id: <process id>, with parameters: E12, c-buddy-RTL-AMD64, <version>, M.E.Imap4, M.E.D.Storage, M.E.D.S.ImapItemConverter.GetHeaders, System.NullReferenceException, <version>. ErrorReportingEnabled: False
To resolve this problem, install Update Rollup 7 for Exchange 2007 Service Pack 1. For more information about Update Rollup 7 for Exchange Server 2007 Service Pack 1, see the following Exchange Help topic: