What is a return receipt mail

sample receipt

Available for an additional fee, only when purchased at the time of mailing.
Available for Priority Mail Express, Priority Mail, First-Class Mail, or First-Class Package Service* items when purchased at the time of mailing with Certified Mail, Registered Mail, Collect on Delivery (COD), Signature Confirmation Restricted Delivery, or insurance (more than $500).
Available for USPS Retail Ground, Media Mail, or Library Mail items when purchased at the time of mailing with COD or insurance (more than $500).