Ingesting into Office 365 may report an error: Items and SMTP Mailbox have to be filled in Items (4242465)

Issue
Sometimes the Office 365 Ingest Module log the following error:
2016-06-15 09:08:34Z|1048|100|ERROR| ProcessFailedResult|Error while ingesting Item with Id [a05f299c-7179-1803-84ce-a010e823a4c1] ItemRoutingId: [2075241] Error: [System.AggregateException: One or more errors occurred. ---> System.ApplicationException: [ (Primary)]: Unable to ingest. ---> System.NullReferenceException: Items and SMTP Mailbox have to be filled in Items Container.
at QUADROtech.ExchangeWebServices.EWS.IngestEWS.Ingest(IIngestContainer container)
at QUADROtech.ExchangeWebServices.IngestExecutor.IngestInternal(IIngestContainer container)
--- End of inner exception stack trace ---
at QUADROtech.ExchangeWebServices.IngestExecutor.IngestInternal(IIngestContainer container)
at QUADROtech.ExchangeWebServices.IngestExecutor.b__0()
at QUADROtech.ExchangeWebServices.Tasks.TaskExecutor.b__0()
at System.Threading.Tasks.Task.Execute()
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at QUADROtech.ExchangeWebServices.IngestExecutor.Ingest(IIngestContainer container)
at ArchiveShuttle.Modules.ExchangeModuleLibrary.WorkManager.QueueBatch(ExchangeImportToMailboxCommand command, ICollection`1 items, IIngestExecutor ingestExecutor)
---> (Inner Exception #0) System.ApplicationException: [ (Primary)]: Unable to ingest. ---> System.NullReferenceException: Items and SMTP Mailbox have to be filled in Items Container.
at QUADROtech.ExchangeWebServices.EWS.IngestEWS.Ingest(IIngestContainer container)
at QUADROtech.ExchangeWebServices.IngestExecutor.IngestInternal(IIngestContainer container)
--- End of inner exception stack trace ---
at QUADROtech.ExchangeWebServices.IngestExecutor.IngestInternal(IIngestContainer container)
at QUADROtech.ExchangeWebServices.IngestExecutor.b__0()
at QUADROtech.ExchangeWebServices.Tasks.TaskExecutor.b__0()
at System.Threading.Tasks.Task.Execute() ]
It is likely some items will ingest, and this error will be reported only for some batches of data.
Solution
The issue can sometimes be seen when using the Office 365 Leavers functionality. It is caused by the [user] object in the Archive Shuttle Directory Database not having a PrimarySMTPAddress set. This can be set manually using SQL if required, or an Office 365 Sync can be performed from the user interface.