Usps Shipping Envelopes Sizes. This article describes service requirements set by the United States Postal Service (USPS). USPS Flat Rate boxes provide a great cost-effective option for anyone who ships a substantial number of packages.
With flat-rate boxes and envelopes, weight Depending upon the shipment size, UPS's services can come at a higher price than those you'd find. To view your order status and tracking information, sign in to your USPS.com account, go to "Activity History", and select your Order#. Well you're in luck, because here they come.
Letter-size mail pieces are considered non-machinable and subject to a non-machinable surcharge if they are.
To ship with this service, you'll first need a free Flat Rate box from the USPS.
Priority Mail Express™ Flat Rate Legal Size Envelope. Stay flat, Compatible with USPS Express mail envelopes. Perfect for sending marketing material of correspondence without having to fold the contents of your package.