Australia Post has warned the day will soon come when it delivers its last letter, with the rising cost to provide the service outstripping demand.

While snail mail enthusiasts are clamouring to keep the art of letter writing alive, the volume of letters we're sending each other has dropped off a cliff, to levels not seen since the late 1930s.

So what might a post-post world look like, and how will the record of history we leave behind change without letters?