Many organisations still have the odd traditional fax machine connected but rarely used. However, when it is needed it is often found not to be connected, not working and not much use!
So the ability to test a traditional fax easily and at no real cost is welcome. If this interests you, check out PDF24 Fax. It is easy and quick to set up a free account and no credit card is required. For the 'free' tier one gets the ability to send 5 faxes per month. For 5 Euro a month, one gets the ability to receive faxes by email, send 40 pages a month and get an inbound fax number.