The United States Postal Service offers both residential and business clients a simple way to ship packages with its Priority Mail flat rate boxes and Priority Mail Express boxes. Priority Mail flat-rate boxes take one to three days to ship, depending on the destination, and come with free online tracking and package insurance up to $50. Priority Mail Express boxes have guaranteed overnight delivery 365 days a year, as well as free tracking and insurance up to $100.
TL;DR (Too Long; Didn't Read)
You can send packages in several sizes including padded and legal envelopes and small, medium and large boxes up to 70 pounds.
Choose Your Boxes
Several types of Priority Mail flat rate packages are available, including padded and legal envelopes and small, medium and large boxes. Priority Mail Express packages include padded and legal envelopes, as well as top-loading and side-loading boxes. The Priority Mail flat rate and Express boxes are available for free at all USPS post offices and branches. You can also order the boxes at no cost by submitting a request on the USPS website.
Prep Your Shipment
Check the list of restricted items on the USPS website. These items include hazardous materials, ammunition, gasoline and explosives. Assuming your item is not on that list, include enough packing material to keep the items safe while in transit. When you seal the box, the flaps must lie flat and close completely. Tape the box shut and do not use twine or string. Your item or items can weigh up to 70 pounds.
Print a Label
Once packed, the Priority Mail package needs a mailing label. You can purchase and print out a label through the USPS website or you can buy a label at a USPS post office counter or self-serve kiosk. Be sure to print the address legibly using a pen or permanent marker, and include the additional four zip code digits if you know them. If the package is fragile or breakable, label the box as such. If mailing to a military APO, FPO or DPO, fill out a customs form. Military packages sent in the large Priority Mail flat rate box receive a discount.
Mail Your Parcel
You can drop off the flat rate box at your local post office. The USPS offers a search feature on its website to find the post office closest to you. If you don’t want to leave your home or office, schedule a free online pickup through the USPS website and your postal carrier will pick up the box from your mailbox or front porch. Businesses can leave the package at the office reception desk for pick-up. To set up a free pickup on the USPS website, choose a date, enter in the type of package and the weight, and indicate where you will leave the package for the mail carrier.