A letter sorting machine (LSM) system of the invention has a plurality of LSMs, each having a feeder, a reader, horizontal convey paths, bins with a push-out mechanism, an elevator mechanism, a separating mechanism for separating the postal matter from the trays, a destination label printer, and a bundling machine. These LSMs are connected to a centralized system controller. The centralized system controller has a computer and a magnetic disk for storing a schedule for determining the mode of each LSM.The computer reads out the schedule table from the magnetic disk and controls the modes of the LSM for performing the primary or secondary sortation according to the kinds and amount of the postal matter to be sorted.