On the service desk that we use to communicate with customers, we can register customer's emails into the system.
If an email arrives from a registered customer, the request is logged and they get an automated response to let them know we are 'on it'.
But, what happens if the customer accidentally sends a support request from an unregistered email?
If the system is set up to only allow requests from registered emails, the request would not be logged.
However, they won't know that the request is not logged and may get annoyed if no one gets back to them.
Ideally they would get an automated response saying you are not registered with us instead of 'radio silence'.
So, what happens when a customer sends a request to Service Desk, via email, from an unregistered address?
The docs on "Who can send requests?" seem to ignore the fact that anyone can, technically, send a request to the service desk. Whether the request is actually handled is a different matter.