Intermittently messages are not delivered and no non-delivery report (NDR) is generated in Microsoft Exchange Server 2019 or Exchange Server 2016. You eventually find that the missing messages are landed in the Poison message queue.
In addition, the following events are logged in the application log:
Time: DateTimeID: 1051Level: WarningSource: MSExchange ExtensibilityMachine:Message: Agent 'Mailbox Rules Agent' caused an unhandled exception 'NotInBagPropertyErrorException: [0x66a5000b] SendReadNotifications' while handling event 'OnPromotedMessage'
Time: DateTimeID: 25012Level: ErrorSource: MSExchangeTransportDeliveryMachine:Message: An unhandled exception was thrown while processing data from client IP address <IPAddress>. SMTP state transitions: WaitingForGreeting -> GreetingReceived (EhloProcessed)GreetingReceived -> WaitingForGreeting (XAnonymousTlsProcessed)WaitingForGreeting -> GreetingReceived (EhloProcessed)GreetingReceived -> GreetingReceived (XExpsProcessed)GreetingReceived -> GreetingReceived (XSessionParamsProcessed)GreetingReceived -> MailTransactionStarted (MailProcessed)MailTransactionStarted -> WaitingForMoreRecipientsOrData (RcptProcessed)WaitingForMoreRecipientsOrData -> ReceivingBdatChunks (BdatProcessed)ReceivingBdatChunks -> ReceivingBdatChunks (BdatProcessed). Exception System.ExInvalidOperationException: Agent 'Mailbox Rules Agent' encountered an unexpected error while handling event 'OnPromotedMessage'. ---> Microsoft.Exchange.Data.Storage.NotInBagPropertyErrorException: [0x66a5000b] SendReadNotifications
Time: DateTimeID: 10003Level: ErrorSource: MSExchangeTransportDeliveryMachine:Message: The transport process failed during message processing with the following call stack: System.ExInvalidOperationException: Agent 'Mailbox Rules Agent' encountered an unexpected error while handling event 'OnPromotedMessage'. ---> Microsoft.Exchange.Data.Storage.NotInBagPropertyErrorException: [0x66a5000b] SendReadNotifications