Mail box box

A clever play on words!

A "mail box" is a container used to receive and store mail, typically located at the entrance of a residence or business.

But, I'm assuming you're referring to a "box within a box" scenario, where you have a box that contains another box, which is often used to describe a nested or layered structure.

In this case, the outer box is the "mail box" that contains the inner box, which could be used to store smaller items or packages.

Am I correct in my understanding?