Last but not least email is much cheaper than postal letters. You only have to pay the local telephone cost for connecting to the Internet server. Sending mail to your neighbour or to the other end of the world makes no difference in charges, and the transfer from your computer to the server goes very fast. Email can also be exchanged with networks other than the Internet. These advantages makes email an important and useful tool for communication.
Experts expect it to grow, especially in business.
For journalists it will become a tool at least as important as the telephone. One reason to do so is to secure your sources. Another question is trust. For Internet experienced people it's easy to fake mails by using others' email accounts. Therefore journalists have to be able to trace a mail to be as sure as possible about the source.