You are concerned that these poor unsophisticated third world people won't listen to anyone else because their own country and culture cannot compete with Proctor and Gamble and Soap Opera and Dallas and the like. It may or may not be true. The universal declaration of human rights rather pretentiously probclaims the right of every person to send, receive, and obtain information from any source. Of course that was drafted in a less nationalistic era. I used to like it, but now I try to avoid it.
Mail is a last resort.
However, once a mailer has touched and delivered any recipient of a queued message file the ability to retract such a message is about zero. Other issues which might further complicate the canceling would be, using the Tenex case as a real world example, local users whose mail files which are directly appended by the senders user agent, while the other recipients in network land, are routed thru the mailer. Peter Neumann at Stanford Research International has been keeping tracking of failures in high-risk systems for some time. I've attatched Peter's annotated bibliography of these system failures. However, these courses are usually elective, and while they may be well attended, are taken by a minority of students graduating with CS degrees.