Since upgrading from Exchange 2010 to Exchange 2013, users who are close to their mailbox limit do not get warning messages, because delivery of the warning message fails, with the following error in the event log:
The store driver failed to submit event <event number> mailbox <mailbox guid> MDB <database guid> and couldn't generate an NDR due to exception Microsoft.Exchange.MailboxTransport.StoreDriverCommon.InvalidSenderException
at Microsoft.Exchange.MailboxTransport.Shared.SubmissionItem.SubmissionItemUtils.CopySenderTo(SubmissionItemBase submissionItem, TransportMailItem message)
at Microsoft.Exchange.MailboxTransport.Submission.StoreDriverSubmission.MailItemSubmitter.GenerateNdrMailItem()
at Microsoft.Exchange.MailboxTransport.Submission.StoreDriverSubmission.MailItemSubmitter.<>c__DisplayClass1.<FailedSubmissionNdrWorker>b__0()
at Microsoft.Exchange.MailboxTransport.StoreDriverCommon.StorageExceptionHandler.RunUnderTableBasedExceptionHandler(IMessageConverter converter, StoreDriverDelegate workerFunction).
Is anyone able to suggest what the problem may be?