Soon lists of addresses become available from budding young entrepreneurs on CD-ROMs. Also, businesses learn what times most people send personal mail and they time their deliveries so that their promotional literature arrives at the Post Office first. If you needed the results of a laboratory test from the other side of the country to determine which treatment is more likely to cure a medical problem your daughter has, what are the chances of your doctor getting the results. She is much more likely to be discarding a boxful of junk mail every day and the lab results will be recycled into paper towels without her ever seeing it. Email is very much like Dumbolia's new postal system.
Email boxes have a finite size.
If a message arrives that will make you exceed your quota then than message is held for a while and then bounced back to the sender. If the sender's email box is full, nothing can be done with the message except discard it. The one difference is that the electrons are not recycled. The sending of spam is very much like Dumbolia's business-support plan. When an email message is sent, you don't have to individually send to each recipient.