emails and regular mails

What is the difference between regular mails and e-mails?As we know, regular mails have been usded for thousands of years,it is very inconvenience,for it took a long time to receive. Besides, it costs you some money. While e-mails is very convenience, it take you only a few seconds to arrive the receiver and it is free to send .so more and more people use e-mails rather than regular mails.Some people think that it will be replace the regular mails.
In my opinion, the email will be more and more popular in the future, but it can not replace the regular mails because it can not send everything though it is very convenience to send letters.But,except letters,we sometimes want to sent other thingsto our friends which e-mails is impossible to send.
    So we can draw an conclution that emails can not replace regular mails.People will use email to sent letter and use the regular to send other things.