As you can see in the screen below we don't see any incoming mails.
Incident is created but the incoming email is not attached.
Also not stored in Journal db table.
In emailservice.frslog, I found
System.ServiceModel.FaultException: Unhandled system exception: System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.Exception: DataValue.ConvertValueToType: unsupported date/time format: 20.07.2016 14:45:13.
The customer had different Date/Time Format Settings on the Server.(yyyy.mm.dd)