A Volunteer Factual Dispatch is a type of communication system used by V.F.D. They are much like telegrams in the way they are written and are presumably sent by radio waves. Upon receiving, they are printed out in the form of a letter by special machines found at V.F.D bases and on V.F.D. vessels.
The only time a factual dispatch was mentioned was in The Grim Grotto. Captain Widdershins of the Queequeg had Violet attempt to repair his machine for sending messages, as he had thought that the network was not operating. Violet found that there was nothing wrong with the machine itself, but that the Fire-Starting Side of V.F.D.'s agents probably sliced the wires of many machines in order to break off communication within V.F.D.
Quigley Quagmire and Kit Snicket managed to send a dispatch to the Baudelaries in a secret message that stated to meet them at Briny Beach for a taxi (though Quigley decided to continue searching for his siblings). The message was recived after Violet and Klaus managed to save Sunny from the poison spores of the Medusoid Mycelium mushroom.