E-mail, Snail Mail and Kid Mail

Ponderings on the different types of mail systems that are in use today and how the idea of what defines mail and a mail system have evolved.

Mail:
1. Materials, such as letters and packages, handled by the postal system.
2. A system by which letters, packages, and other postal materials are transported.

E-Mail (technology inspired, abbreviation for electronic mail):
1. A system for sending and receiving messages electronically over a computer network, as between personal computers.
2. A message or messages sent or received by such a system.

Snail Mail (a technology inspired retronym):
1. Conventional post, as opposed to e-mail.
2. The conventional postal system.

Kid Mail (obviously not inspired by technology but more likely by economy):
A folder system of relaying daily paper notices to parents/staff. (schools.lwsd.org/Discovery/glossary.htm)

In southeast Michigan kid mail is very common and is even used by parents to send notes to other parents through their kids; however, kid mail must be a regional concept as I was hard pressed to find the above definition.

Where does the evolution of mail leave pen pals? Should e-mail pals be called keyboard pals? Or have text messages, instant messages and chat rooms taken over?