Certainly, one of the problems with email is that it is free for the sender. If sending an email required even a small amount of "postage", even a thousandth of a cent, it would solve a lot of problems. (Perhaps, the receiver would get the bulk of this "postage", with the service provider creating the infrastructure getting a commission.)

The problem with it is that there is no easy way for anyone who is willing to pay a thousandth of a cent to send an email to someone to pay it. Despite how much the internet has boomed in the last thirty years, there is still no good way for individual consumers to send and receive micropayments worldwide.