To send out I assume? Really tricky sometimes... you can find that the device doesnt support the bit rate and it just fails. Also, does VOIP provider support fax?
For receiving I would get a supported SIP provider and utilise the fax to email service in 3CX.
For sending I would look into services that can do it online - you might find trying to set it up the way you're thinking is not worth the hassle.
Also, fax is for dinosaurs tbh.