You can add the following options to First-Class Mail International®, (except for postcards) to …
Secure the contents.
Registered Mail™ for security for Priority Mail Flat Rate® Envelopes and Small Flat Rate Priced Boxes. Some countries have restrictions on Registered Mail.
Get proof of mailing.
Certificate of Mailing as a way of proving the date you sent it. Only available for First-Class Mail® that isn’t Registered Mail.
Get proof of delivery.
Return Receipt with the recipient’s signature sent by postcard. Must be combined with insurance and Registered Mail. Some countries don’t allow return receipts.
Get only authorized recipients to sign for the delivery.
Restricted Delivery to limit who can receive the delivery. Must be combined with Registered Mail and a return receipt. Some countries do not accept restricted delivery.
Learn more about extra services ›
Postcards
- Must be rectangular.
- Minimum size is 5 1/2" long x 3 1/2" high x 0.007" thick.
- Maximum size is 6" long x 4 1/4" high x 0.016" thick.
- Postcards that are over 6" long x 4 1/4" high x 0.016" thick will be charged as a letter or large envelope, depending on size.
Letters
- Must be rectangular.
- Minimum size is 5 1/2" long x 3 1/2" high x 0.007" thick.
- Maximum size is 11 1/2" long x 6 1/8" high x 1/4 thick.
- Maximum weight of 3.5 oz.
- Letters will be charged a nonmachinable surcharge if it’s a square letter of 5" x 5" or larger, it doesn’t bend easily, has clasps or similar closure devices, has an address parallel to the shorter dimension of the letter, contains bulky items like pens, or the length divided by height is less than 1.3 or more than 2.5.
- Most hazardous materials cannot be shipped.
Large Envelopes
- Must be rectangular.
- Minimum size is either more than 11 1/2" long x 6 1/8" high OR 1/4" thick.
- Maximum size is 15" long x 12" high x 3/4" thick.
- Large envelopes that exceed these dimensions will be charged package rates.
- Can weigh up to 64 oz.
- Most hazardous materials cannot be shipped.
Packages
- Maximum weight is 64 oz.
- Maximum length is 24" (36” for rolls).
- Maximum combined length, height, and width is 36" (42” for rolls).
- Most hazardous materials cannot be shipped.
- With few exceptions, cigarettes and smokeless tobacco shipments cannot be mailed.
See tobacco restrictions and guidelines ›
Find out what you can send internationally ›
Get additional information in the International Mail Manual ›
