SlackBuildsOrg/network/efax-gtk

It is a GTK+ front end for the efax program who can be used to send
and receive faxes with a fax modem, and to view, print and manage
faxes received. It also has a socket interface to provide a "virtual
printer" for sending faxes from word processors and similar programs,
and can automatically e-mail a received fax to a designated user, and
automatically print a received fax. It is specially nice for a single
user's use, as probably he/she doesn't usually need a fax server
(i.e. hylafax).

See README.SLACKWARE file in efax-gtk's docs directory for
configuration notes.