A high speed sheet-material separating and feeder system is disclosed which handles a wide range of mixed thicknesses and sizes of envelopes and sheets. In a free running mode, the system can conservatively handle 30,000 pieces of mail per hour. The sheets are stacked at one end of the system, and are fed to a first of two separator mechanisms. The first separator mechanism is adjusted for thicker sheets of the range. Sheets leaving the first separator are then fed to the second of the two separator mechanisms. The second separator is adjusted for thinner sheets of the range. Sheets leaving the second separator are ejected one at a time, in seriatim, where they then can be fed to other sheet handling equipment for processing.