In a Microsoft Exchange Server 2013 environment, the OWA application pool crashes several times a day. In this situation, the following event is logged:
Date Time Error server.domain.com 4999 MSExchange Common General N/A Watson report about to be sent for process id: process id , with parameters: E12, BuildType, VersionNumber, w3wp#MSExchangeOWAAppPool, M.Exchange.Services, M.E.S.C.T.ParticipantInformationDictionary.GetParticipant, S.C.Generic.KeyNotFoundException, XXXX, VersionNumber. ErrorReportingEnabled: True
This issue occurs because Exchange Server expects all meeting participants to be rendered. However, for some special meetings, some participants may not be rendered successfully. When this issue occurs, a KeyNotFound exception is displayed, and the OWA application pool crashes.