Hi, A user had some weird problems in his Outlook (messages were sent, but nobody received them). In the Exchange 2010 server Application Event logs appeared some errors when he sent mails: Event ID: 1009, Source: MS Exchange Store Driver The store driver encountered a poison message during message submission. The submission will be stopped for event 8484834 on mailbox 8d6cb3e9-d56e-4625-81b8-9a340e9602b3 MDB 6bd95bc8-fa9e-4a6a-bf80-e7c234d52fb0. Exception is: System.InvalidOperationException: InternetMessageId was null on item FgcwlqtI7YNElGstEysiqFIAAATO97xGAAAAAD7QXCFvcRJPnhS/6agOSNoHAAcwlqtI7YNElGstEysiqFIAAAAAACYAAAcwlqtI7YNElGstEysiqFIAAATO57wAAAk= from mdb 6bd95bc8-fa9e-4a6a-bf80-e7c234d52fb0. at Microsoft.Exchange.MailboxTransport.StoreDriver.MailItemSubmitter.CreateMailItem(SubmissionInfo submissionInfo) at Microsoft.Exchange.MailboxTransport.StoreDriver.MailItemSubmitter.<>c__DisplayClass2.<Submit>b__0() at Microsoft.Exchange.MailboxTransport.StoreDriver.StorageExceptionHandler.RunUnderExceptionHandler(IMessageConverter converter, StoreDriverDelegate workerFunction) at Microsoft.Exchange.MailboxTransport.StoreDriver.MailItemSubmitter.Submit() at Microsoft.Exchange.MailboxTransport.StoreDriver.RpcSubmit.SubmitMessageImpl(SubmissionInfo submissionInfo). Followed by an error report: Event ID: 4999, Source: MSExchange Common Watson report about to be sent for process id: 2732, with parameters: E12, c-RTL-AMD64, 14.00.0682.000, edgetransport, M.Exchange.StoreDriver, M.E.M.S.MailItemSubmitter.CreateMailItem, M.E.M.StoreDriver.FailFast+UnexpectedSubmissionException, f2cd, 14.00.0682.001. ErrorReportingEnabled: True And: Event ID: 1009, Source: MSExchangeMailSubmission The Microsoft Exchange Mail Submission service is currently unable to contact any Hub Transport servers in the local Active Directory site. The servers may be too busy to accept new connections at this time. When searching the web for any source of this problem and/or solution, I only find references to check out the Poison queue for messages. But there is no such queue. Any idea's where to look? Setup: 2 x Exchange 2010 Standard in DAG with 2 databases on 2 x Windows 2008 Enterprise