the problem should be the queue database. If you stop the ExchangeTransport Service, delete or rename the queue database and then restart the Transport Service, the issue could be resolved.
Please follow the steps below:
1). Stop Msexchange transport service manually on it.
2). Go to path below: c:\program files\Microsoft\Exchange Server\TransportRoles\Data\Queue on mailbox server.(by default for EX13)
3). Rename mail.que to mail.que.old
4). Startup Msexchangetransport service manually on server.