Faxing is a function that can only use analog phone lines and analog fax
modems. Accordingly, no fax software will function with cable modems or DSL
lines. With some DSL connections you can obtain a DSL line filter suitable
for connecting a standard analog voice line to the DSL line and can then
connect an analog fax modem to that line.

If you have no analog modem or phone line, you will need to use a fee based
Internet Fax Service. Several are listed here: http://www.savetz.com/fax/