The best mode of ensuring that items posted get to the named addresses is through

Explanation

Registered mail is a mail service that allows the sender of a mail to get an electronic verification about the package being sent or that a delivery attempt was made.

The sender gets a receipt when the item is mailed, and the receiver must sign to confirm that it was indeed received.

It is one of the most secure ways of sending packages

With the registered mail, you are required to make a trip to the Post Office to drop off your package. This means you cannot deposit your package in a collection box.