It's why I say that electronic media is public. You said earlier that lateness was one of the biggest issues employers faced nowadays. We have lines open for questions, folks. REally think of a compelling benefit for the person and start with that benefit. Keep it very short ending with an action request.
Snail mail is probably somewhat unusual today for personal communication.
I often think e-mail gets misinterpreted. If you have a disagreement or a problem with another person it is inappropriate to use email to communicate that problem. Meet with the person privately. This seems very impersonal and somewhat lazy to me. There's something far more beneficial in that face to face, personal contact.