As part of the deal brokered with the Communications Workers Union (CWU), existing rules that limit the number of unaddressed flyers, leaflets and letters to three per household have been lifted.
The CWU had previously stated that unlimited mail would make mailbags too heavy but the Royal Mail has pushed for the revenue boosting move in the face of mounting competition.
Royal Mail currently enjoys about 25% of the unaddressed mail market but is looking to take business from rivals.
The deal also sees postal workers awarded a 6.9% pay rise over the next three years. It also ends the threat of further strikes.
Postal workers staged a series of walkouts in the autumn in a dispute over jobs, pay and modernisation.
A truce was called in November that put a stop to the planned Christmas stoppages and the two have been locked in talks since the turn of the year.