Freeze the peaches overnight the night before shipping. This will temporarily stop their ripening to ensure that they do not spoil before reaching the destination.
Pack the peaches in a dry, airtight plastic container on the day that you want to ship them, without washing them. The postal service requires that fresh fruits be mailed in dry form.
Take the peaches in the plastic container and a cloth or rag to your local post office. Select a medium or large Priority Mail Flat Rate Box, usually available in the post office lobby. Assemble the Priority Mail box following the written instructions. Priority Mail shipping will ensure faster delivery of your fruit, reducing the chance of spoilage.
Spread the medium-size cloth along the bottom of the inside of the Priority Mail box. Seal the airtight plastic container with the peaches, and place it inside the box on top of the medium-size cloth. The cloth lining will prevent leakage of fruit juice if your peaches spoil and the juice leaks from the container.
Seal and address the Priority Mail box and present it to a postal service employee to obtain valid postage and to ship the package. Packages that weigh more than 13 ounces must be presented for shipping, according to postal service regulations.