
IMPORTANT: When you send using First-Class Mail International, you must write "AIRMAIL/PAR AVION" on the address side of your postcard, letter, or large envelope.

embassy in another country (APO/FPO/DPO mail), see How to Send a Letter or Postcard: Domestic. See more on addresses in the International Mail Manual.

Size & Weight Requirements – Postcards & Envelopes to another country costs the same as sending a letter. Sending a regular-sized, rectangular postcard from the U.S. Postcards: Standard postcards are usually made of thick paper (cardstock), are between 5-1/2" to 6" long and 3-1/2" to 4-1/4" high, and are no more than 0.016" thick. If your large envelope is nonrectangular, rigid (can't bend), or lumpy (not uniformly thick), you'll have to pay the package price. If you want to send letter-sized correspondence without folding it, you can use a large envelope (called a 'flat") the postage for international flats starts at $2.60. You’ll also have to pay more if your envelopes are square or vertical (taller than they are wide). ( See additional postage in Step 4.) Nonmachinable items include envelopes that are lumpy or rigid, or have clasps, string, or buttons. TIP: If your letter can’t fit through USPS ® mail processing equipment, it’s "nonmachinable" and you’ll have to pay $0.30 more to send it. 10 envelope is 9-1/2" long x 4-1/8" high.) You can fold what you put in your envelope, but it needs to stay flat-no more than 1/4" thick. Letter envelopes for international mail can be 11-1/2" long x 6-1/8" high. letters, international letters must be rectangular and made of paper to qualify for letter prices.
