FoIP, also called IP faxing, is a method of sending faxes over the Internet.
To fax over IP, you must find a voice-over-IP provider that support the T.38 data transmission protocol. You will then need to set the right settings and configuration for your VoIP line and then connect the phone line to your fax machine.
2-Using the fax-to-email method: the fax message is scanned producing a binary image file, which can then be sent to a email addres as email attachment to the fax service which forwards it to a real fax machine.
3-Sending the fax over a VoIP channel: simply involves sending a fax message using a machine connected to a VoIP network.
You can send IP faxes using a VoIP server ,it doesn't automatically work seamlessly for transmitting faxes. It typically requires some modifications, which you can make by installing a piece of software.