You are so welcome; good luck
Honestly, before my job went to the electronic faxing, my little office space had the big fax machine. There were days I would walk into my (locked) office and find dozens of personal information for one of the residents. He use using the fax machine as his own personal business, even though he wasn't supposed to (I worked at a retirement community, and this was a resident who was trying to secure some business or something back where he used to live). It didn't matter what the guy was doing, but he had copies of bank checks and accounts come through this machine, as well as applications with social security numbers. I questioned it to some people in leadership (my bosses) about the legitimacy of keeping the files "in view of others" and they said "put everything in an envelope when you see it, lock it in the lockbox in your office, and when he comes to retrieve the paperwork, it'll be fine". So that's what I did even though anyone with a key to my office (quite a few people because it was shared), could see this guy's information. Which is why going to that email fax service saved everyone.
That is what the program we were using is almost like - a registered email service going over VoIP. Yes, it was temperamental some days because we never got notifications a fax came through, as it would appear in a desktop folder, but sometimes it never came through at all. Depending on what type of document you were sending (how many pages), it might fail as well. At least 8 times out of 10, it worked, so can't complain on that.
Ming - one of the things I could suggest too, before you get super involved, would be try "faxing" someone you know personally who might still have a fax line. But use your email as the sending.
What I would do is:
1) log in to your email.
2) compose an email to a fax line, and use the fax number as the "to" and put something in the subject line
3) Body of the email do some salutations and what not
4) attach any document you might need to provide (a fake Word doc or whatever. Even a scanned document you use your scanner for)
5) Send that when you're done and see what happens.
That's the premise anyway, of what we were doing with our faxes.
I remember when I had a flip phone, I would text my friend with his email address as the "to" and he'd see my text in his email. He would respond with long messages back, so I would have to tell him "keep it short because it's going to text on my phone and I can't see it all", so he learned when he saw my mobile number as the sender, I was texting him.
The same thing might work for faxing? Like I said, at least that's the idea of whatever service we were using. Except responses would come back to our fax number. Outgoing faxes were email generated to whatever business, incoming faxes were pushed in to a folder on the network.