Large First-Class envelopes (flats) that exceed maximum dimensions or are rigid, non-rectangular, or not uniformly thick are charged package prices and shipped with USPS Ground Advantage.

The maximum size for a flat provides plenty of room to put lots of material in the envelope. But keep in mind that weight usually affects price – the higher the weight the higher the postage, especially for …

Cost of First-Class™ Stamps Letter Stamps Standard-sized, rectangular envelopes From $0.78 Square, Oversized, or Unusual Envelopes From $1.27 Postcard Stamps Standard-sized, rectangular …

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If you want to send letter-sized papers without folding them, you can use a large envelope (called a "flat"); the postage for flats starts at $1.63. If your large envelope is nonrectangular, rigid (can't bend), …

When a piece of First-Class Mail exceeds any one of the maximum measurements of a letter, it is classified and priced as a large envelope (flat). The maximum weight for letter-size pieces is 3.5 …

First-Class Mail ® is an affordable mail service for standard-sized, single-piece envelopes weighing up to 3.5 oz and large envelopes weighing up to 13 oz. Prices start at $0.78 at a Post Office.

If you've received a threatening letter in the mail or encountered cyberbullying, and the U.S. Mail ® has been used in any way, report the incident using the "Report Now" link at the bottom the page at …

What's the Date you plan to mail the item? What's the Time you plan to mail the item?

Media Mail ® is an economy shipping solution for media items. Available for sending small and large packages containing books, film, manuscripts, sound and video recordings, and computer media …