Use PayPal.com/Shipping (Single or Multiple orders) or PayPal.com/ShipNow (Single orders) and send the shipping label to your customer as an email attachment.
Discuss, with your customer, the shipping information, such as shipping method, shipping costs, and determine who will pay for the costs. If you and your customer have determined that you pay for the costs, you can send them the amount.
See what return services the preferred shipping carrier has. They also have return services for future orders, such as USPS's Priority Return Service.
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