What is CFNL (Communication forwarding on not logged in)?

The Communication forwarding on not logged in administration empowers a served subscriber to divert incoming communications which are addressed to the served subscriber’s address, to another subscriber in the case where the served user is not logged in. The CFNL service work on all communications, or on those related to determining basic services.
As a service supplier option, a subscription option can be given to empower the served subscriber to get a sign when the served user logs out, that the CFNL service has been enacted.