Insurance limits vary from country to country. The USPS will not reimburse mailers in amounts higher than proven value. Don't over-insure packages. MAIL Certified and Registered mail is often confused. Both must be sent first-class and can have a Return Receipt Card, but the similarities end there.
Registered mail is the most secure method of sending valuables through the mail system.
It provides the sender with written evidence of mailing. This service is offered for both domestic and international mail. Costs include a registry fee in addition to postage. A value must be declared for the mail at the time of mailing. The registry fee for domestic mail will be determined by the declared value.