Emails are being downloaded from the email server and a Journal.Email record is created, but no related Incident record.
The CI.Service "Service Desk" had been deleted . Therefore the Incident creation fails because "Service Desk" cannot longer be validated via the pick list called "Service Name List".
In the demo database which is the base for any customer database per default in the Incident object an Initialization Business rules called "Initialization Rule for Incident.Service (Default)" exists which sets the value "Service Desk" the required field Incident.Service. An inherited business rule exists also on the "Incident.WebSelfService.New"-form.
Both Business Rules needs to be changed to have a value which is part of the pick list called "Service Name List".