Who is primarily responsible for covering postage due for short-paid packages?

The mailer is primarily responsible for covering postage due for short-paid packages. This responsibility stems from the principle that the sender of the package is the one who initiates the shipment and is therefore accountable for ensuring that the correct postage is affixed. When a package is sent with inadequate postage, it is the mailer’s obligation to ensure all postage fees are covered, as they determined the shipping method and rates before mailing. This responsibility supports the operational costs of the postal service and maintains the integrity of the mailing process.

While the recipient may sometimes be asked to pay any applicable postage due, it is not their responsibility to ensure that the package has the correct postage when it was sent. Similarly, while the post office provides the service of delivering mail, they are not responsible for postage shortfalls, and the sender solely refers to the party who initially dispatches the package. Thus, the correct answer highlights the mailer's role in managing and fulfilling postage requirements.