And that still defends against the biggest howler with email, that in raw form it is a post card, not a enveloped letter. The issue if trusting that the sender

And that still defends against the biggest howler with email, that in raw form it is a post card, not a enveloped letter. The issue if trusting that the sender is who is being claimed is a very different issue, and one that i don't think anyone had solved yet beyond cumbersome exchange procedures (possibly involving locked suitcases).