Can't Send: Outbox empty, but 6 Unsent emails?, 'User account does not have right to send mail'

What could cause send failure?  Ver. 7.1.30617.0
When closing emClient, a dialog indicates there are unsent messages in the Outbox.
But the Outbox folder is empty.

This is a new error:
‘Sending email failed due to the following error: The user account which was used to submit this request does not have the right to send mail on behalf of the specified sending account., Cannot submit message.’

But messages do send from the Outlook.com web app.

Some of the other errors are:
8:18:36 AM account@hotmail.com [Exchange Web Services]  Synchronizing folder ‘account@hotmail.com/Calendar/US Holidays/’

8:20:27 AM    at Microsoft.Exchange.WebServices.Data.ServiceResponse.InternalThrowIfNecessary()

8:20:27 AM    at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.Execute()

8:20:27 AM    at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalCreateItems(IEnumerable1 items, FolderId parentFolderId, Nullable1 messageDisposition, Nullable`1 sendInvitationsMode, ServiceErrorHandling errorHandling)

8:20:27 AM    at Microsoft.Exchange.WebServices.Data.Item.InternalCreate(FolderId parentFolderId, Nullable1 messageDisposition, Nullable1 sendInvitationsMode)

8:20:27 AM    at Microsoft.Exchange.WebServices.Data.EmailMessage.InternalSend(FolderId parentFolderId, MessageDisposition messageDisposition)

8:20:27 AM    at MailClient.Protocols.Exchange.ExchangeGenericCommand.Execute(WorkerStatus status)

8:20:36 AM account@hotmail.com [Exchange Web Services]  Sending email: Test message

I can’t empty, the Empty Outbox to eliminate the old failed email send items.

Any advice greatly appreciated.

This must be rare.

Hi Edward,

There is a newer version 7.1.30719.0 of 18 July 2017.

Maybe your issue is solved in that version.

http://www.emclient.com/release-history

Thanks Hans,

The same errors are produced and no send with the new version7.1.30719.0.

9:15:13 AM   MailClient.Storage.Application.OperationException: Sending email failed due to the following error: The user account which was used to submit this request does not have the right to send mail on behalf of the specified sending account., Cannot submit message. —> Microsoft.Exchange.WebServices.Data.ServiceResponseException: The user account which was used to submit this request does not have the right to send mail on behalf of the specified sending account., Cannot submit message."

I will try to remove and re add the account later today.

Removing and reinstalling the account corrected this.
The auto configure seems to be better too now.