Three boxes running fast across the globe

On Monday, at noon, I shipped three boxes
with things belonging to my son from a
small local post office half across the globe.
Each box cost about 50 US dollars in
shipping.
My estimate is that the boxes were picked
up at that local post office on Tuesday morning.

On Friday morning I was sitting in the
living room with little Kate in my arms,
when the outside door bell rang twice.
I didn't even know how to open the outside
door.
Kate's parents were sleeping.

Then the inside door bell rang, so I
understood something had to be done.
Calling out for my son, I carefully opened
the door.
There stood a postman who wanted to
deliver my three boxes!