Fax machines are inherently more secure that t'internet
It is highly difficult to hack into a fax machine (you have to physically cut the line - you cannot "T" into a fax communication because it's bidirectional with the same frequencies used on both sides so you usually have to insert a hybrid in-line to separate Tx from Rx), and it is impossible to do so from outside the country.
And if you do manage to hack the machine, you'll only get the real-time faxes sent to & from that particular machine from that time on, not a database of the past 10 years' email correspondence from all users on the server.
All the security and reliability issues mentioned are due to failings in the way faxes are used and is no different to Internet based communications. Yes, an unattended fax machine is a security risk. So is an unattended logged-in terminal, or an unattended printer or an unattended filing cabinet. And if the fax does not get to the person it is supposed to get to, that's a failing of the way it is managed, not the fax. Exactly the same can happen to an email (or snail-mail) - e.g. when the recipient has left or away on holiday, or when they delete your email without reading because it's buried amongst last night's spam, or when it is sent to the wrong email address and not forwarded to the correct person. Or when the email server crashes after receiving the email and gets restored using last weeks' backups.
The fax machine sends back confirmation that the fax was correctly received and printed which works 99% of the time (if it is out of paper or has a mechanical jam it will send back an error to the originating machine, but a few other failures can occur that result in an "OK" response with nothing printed). It cannot confirm that anyone bothered reading the fax, any more than your email receipt confirmation means that anyone actually read the contents of your email rather than e.g. the confirmation being automatically generated by a computer running an email client behind an empty desk (which like the fax, would be a problem with the configuration and/or policy, not emails in general).