[SaF] USPS Priority boxes

[TEESEEBEE]

            I need to know who currently manufacturers Priority Mail boxes 
for the United States Postal Service.  Is the manufacturer obligated to a 
long-term contract?  Does the manufacturer also produce the cardboard used to 
build the boxes?  If not, who does?  Is the cardboard made from recycled 
paper products?  Thanks for any resources to this and related information.