Abstract: The present disclosure involves a system for storing and processing articles such as mail flats which cannot be processed on standard letter mail equipment. The system includes mechanical carriers for transporting and remaining with the articles throughout the processing cycle. A recirculation buffer subsystem provides temporary high density random storage which dynamically allocates the system output resources through computer control. In the buffer, the destination-encoded carriers are kept continuously moving in a closed serpentine path. Based upon system priorities, selected carriers may be taken out of buffer storage independently of the other carriers and the former reassigned to output accumulation racks where they remain until outputted from the system. The recirculation buffer subsystem provides a balance between system input and output, thereby substantially improving efficiency and providing savings in cost and space requirements.