First - Stop all political and administrative actions for the discontinuance of the mail on Saturdays. This underutilizes capital equipment by a fifth. A total waste.
Next stop all Postal Service advertising saving whatever the USPS there spending. The postal service should not have an interest in increasing demand for its services.
Finally, institute alternate days delivery; delivering to half of the routes on Mondays, Wednesdays, and Fridays; and delivering the other half of the routes on Tuesdays, Thursdays, and Saturdays. This will cut the delivery force in half -- a better savings in both personnel and fuel for the present need.