Maybe it was delivered on a polo pony

While it may be the case that "neither snow, nor rain, nor heat, nor gloom of night, nor the winds of change, nor a nation challenged, will stay us from the swift completion of our appointed rounds" if the mail is late, it may be very late. A postcard mailed from Montana finally got delivered 47 years after it was hand cancelled on July 5, 1962. No one in the Postal Service is exactly taking responsibility for what happened, much less willing to speculate over why it happened. While emails sometimes get bogged down in that series of tubes that runs around the world and even to Mars, it still remains faster than snail mail.