- International Mail Manual > 2 Conditions for Mailing > 240 First-Class Mail International > 242 Eligibility
Subject to applicable weight and size limits, only correspondence and nondutiable documents that are otherwise acceptable and not prohibited by the Postal Service or the country of destination may be mailed at the First-Class Mail International price.
No merchandise, whether dutiable or nondutiable, may be mailed using First-Class Mail International service. Items containing merchandise may be sent by Global Express Guaranteed service, Priority Mail Express International service, Priority Mail International service, or First-Class Package International Service; commercial mailers may also use IPA packages (small packets) and ISAL packages (small packets).
First-Class Mail International mailpieces are sealed against inspection.
Certificate of mailing service is available for purchase for First-Class Mail International items.
Registered Mail service is available for purchase for First-Class Mail International items, including for such items mailed as Free Matter for the Blind.
For First-Class Mail International items, return receipt service is available for purchase only for items that use Registered Mail service to certain destinations — see the Individual Country Listings for availability and 340 for preparation procedures.
