When the coding machines were implemented, processing speeds were estimated at 300,000 letters per hour. The system never quite delivered these peak efficiencies. The state-of-the-art machinery was nicknamed the 'Redfern Mangler' and the post frequently damaged by the machinery.  

By 1972 Redfern Mail Exchange had experienced a 10% fall in productivity, and had become infamous for industrial strikes, mail delays, and equipment failure.