Comment by c0balt

To add to this, most emails are likely within the organization and/or between public institution.

E-Mail was (last time I checked) not an approved medium for delivery of important documents as it does not (per design) have a mandatory receipt of the message being delivered. So a citizens does not need to worry a lot about this for important documents/mail.

(Fax was so popular for public institutions in Germany because it satisfied this standard. It meant it usually was the lowest barrier option and you could rely on it for all (un)important documents)