E-mail today (e-mail, "soap") – need, the postal address it is necessary to the people living in the different cities and persons interested to communicate, and about those who build the business, to speak and it is not necessary.
Sometimes it is very important to define who possesses a certain mailbox. For example, someone sent you the letter with the rough contents or, on the contrary, very tempting offer, and his personality at least owing to natural human curiosity became interesting to you.