Link to an article by Victoria Law:
“Captive Audience: How Companies Make Millions Charging Prisoners to Send an Email”
This article buries at the end the official rationale for banning conventional mail (smuggling in drugs). But it also provides a simple explanation of new methods by which prisoners and their friends and families are exploited by the prison-industrial complex.
Bonus links: “9 Surprising Industries Profiting Handsomely from America’s Insane Prison System” and “This System Is a Moral Horror” and …And the Poor Get Prison