What would happen if you filed a FPL from AFPEx when departing an airfield that is connected to the AFTN? Will they be aware of your FPL, or will you still have to fax a copy to the tower?
As the departure airfield is listed in the addressees they should get a copy of it. One look will show the plan has already been properly addressed and so they will just process it locally. If you fax a plan through then addressing remains their responsibility.