Here is a basic explanation of how it works, from a user's standpoint.
There are three email address formats which allows one to send faxes.
This is the simple case. It lacks the ability to
encode the recipient's name on the fax front page. If your
fax contains text information, this is ok.
This format encodes both the phone number and the recipient's
name. For example, many will encode an email-fax like this
This lets the fax gateway extract both the phone number
and the full name, so a nice front page may be built.
Linuxconf lets you define a list of aliases for faxes. This is handy
when a lot of people need to fax to the same person.
The mail to fax gateway will support email attachment and will
try to convert them to formats managed by the fax engine you are
using. Often a fax will be an empty email with a nice attachment
in PostScript or another suitable format.