Problem Definition

When customer has set "Anyone can create a customer request via email" it is not possible to set a default reporter for the tickets raised from an unknown email address.
One use case is to notify the default reporter that a new ticket from an unknown address has been created so the default reporter can reassign it to a registered user if the customer has sent the message from an unregistered address or to forward the ticket that were sent to the service desk by mistake to the right department.

Suggested Solution

Add an option when activating "Anyone can create a customer request via email" : When creating a ticket from an unknown address, user can choose whether to create the ticket with a default reporter or with a new user.