The USPS and Staples agreed in October to allow Staples employees to sell postal packaging and accept mail that is later picked up fromthe stores by postal workers.
The yearlong pilot program was launched in 82 Staples stores in California, Georgia, Pennsylvania and Massachusetts.
USPS spokeswoman Darleen Reid said, "The 82 store locations will be transitioned into the U.S. Postal Service's long-established Approved Shipper Program by Aug. 29."
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In the pilot program, Staples sold only USPS shipping services and products. However, in the approved shipper program, Staples, likeother retailers, will offer some postal agency products alongside those of other shippers.
"Staples will continue to explore and test productsand services that meet our customers' needs," Carrie McElwee, a Staples spokeswoman said in an email.
In March, Staples said it would close up to 225 stores in the United States and Canada—12 percent of its North America outlets—as it loses customers to mass market chains and e-retailers.
The Postal Service has also been plagued by financial troubles as more people pay their bills and communicate electronically instead of sending stamped mail, and as it struggles to pay into a health fund for itsfuture retirees, as mandated by a 2006 law.