I'm receiving the following in my application event log.
Exchange Server Information Store has encountered an error while executing a full-text index query ("and(subject:string("SearchQueryStxProbe*", mode="and"), folderid:string("5642D8B75123CF4193D7F0C9F53C3C6300000000010D0000"))"). Error information: System.TimeoutException: Failed to open a channel.
at Microsoft.Exchange.Search.OperatorSchema.PagingImsFlowExecutor.ExecuteServiceCall(IProcessingEngineChannel& serviceProxy, Action`1 call, Int32 retryCount)
at Microsoft.Exchange.Search.OperatorSchema.PagingImsFlowExecutor.ExecuteSearchFlow(String flowName, Dictionary`2 inputData)
at Microsoft.Exchange.Search.OperatorSchema.PagingImsFlowExecutor.<ExecuteInternal>d__1f.MoveNext()
at Microsoft.Exchange.Search.OperatorSchema.PagingImsFlowExecutor.<ExecuteSimple>d__a.MoveNext()
at Microsoft.Exchange.Server.Storage.FullTextIndex.FullTextIndexQuery.ExecutePagedFullTextIndexQuery(Guid databaseGuid, Guid mailboxGuid, Int32 mailboxNumber, String query, CultureInfo culture, Guid correlationId, Boolean needConversationId, QueryLoggingContext loggingContext, PagedQueryResults pagedQueryResults)
at Microsoft.Exchange.Server.Storage.StoreCommonServices.StoreFullTextIndexQuery.ExecuteOnePage(Context context, MailboxState mailboxState, Boolean needConversationDocumentId, SearchExecutionDiagnostics diagnostics)