E-mail would have really had what it takes to be an alternative to letters, but no! You have to make the login so complicated and then there are thousands of providers and you have to decide on one AT THE BEGINNING...
.. and with that they have already squandered their chance. In my environment, e-mail was too complicated for most people (with the providers and then looking for e-mail addresses, etc.) Today, none of them use it anymore. Me neither. Hope for fax now.