The telephone may not be the best means to deliver a lengthy or detailed message. The telephone also may not be the best means of introducing yourself to a prospective employer or business connection. The telephone lends itself to familiarity, a lack of formality. Your first communication with a prospective employer might best be made by way of the old-fashioned letter through the post, followed up with a phone call. On the other hand, information of a timely fashion can be dealt with best by e-mail, provided the receiver has regular, easy access to this channel of communication.
Most large corporations do.
Urgent messages should be handled over the phone, to assure their being received. It is very important to recognize the various kinds of interference that can hinder effective communication. Your message to that prospective employer is probably of the utmost importance to you, so it should be followed up with some sort of written communication restating the message. Also, there is a greater chance of miscommunication whenever either you or the receiver of your message is ill or tired. Both conditions impinge on our ability to communicate and to understand a message accurately.