When do you use E-mail?

You use E-mails inorder to send a quick message to someone in order to usually recieve a instant repsonse. Also, it is common to use E-mail in a work situation, as it is much quicker than actually finding the person and then having a conversation with them. Also, it is more efficient to use E-mails to talk to someone abroad, as it is free unlike the expensive phone calls it would take to talk to them over international phone lines.