Mail to Fax gateway Many technologies exist which allow faxing right from your worksta- tion. Many are proprietary or OS specific. On the other hand, elec- tronic mail is now well established with open standards -- anyone can email. An email to fax gateway provides a global solution to the fax problem. Now anyone can fax, from anywhere, using any operating sys- tem. An email to fax gateway introduces a new problem, however: now anyone can fax, from anywhere, using any operating system. The email to fax gateway of Linuxconf is not a faxing system but a sophisticated gateway. This gateway has many access controls and strategies for giv- ing you control on who may fax and from where. 11.. PPrriinncciipplleess Here is a basic explanation of how it works, from a user's standpoint. 11..11.. HHooww ttoo mmaaiill There are three email address formats which allows one to send faxes. +o phone@fax.your_domain 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. +o name@phone.fax.your_domain This format encodes both the phone number and the recipient's name. For example, many will encode an email-fax like this jacques.gelinas@999-9999.fax.solucorp.qc.ca This lets the fax gateway extract both the phone number and the full name, so a nice front page may be built. +o alias@fax.your_domain 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. 11..22.. TThhee aattttaacchhmmeennttss 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. 22.. SSeettuupp Configuring the mail to fax gateway involves few operations. Mostly, for the mail to get through, there is some DNS work to do, and you must set access control policies. 22..11.. DDNNSS mmaannaaggeemmeenntt You must provide "email advertising" or MX records for the fax gateway. You need to add two pseudo hosts in your domain. Each host will contain a pointer to the fax gateway server in the email advertising section. +o fax.your_domain This pseudo host takes care of directing the email-fax of the form phone@fax.your_domain and alias@fax.your_domain. +o *.fax.your_domain This one takes care of the form name@phone.fax.your_domain. 22..22.. SSeettttiinngg sseennddmmaaiill The fax gateway must run sendmail. It does not need to be the official mail server of your company; although there are some relationships. See the "access control details" later in this help document. The email to fax gateway must be enabled before generating the sendmail.cf. Fill in the dialog "mail to fax gateway/basic information." Check out the help screen. Generate the sendmail.cf (linuxconf will tell you to if you forget). 22..33.. AAcccceessss ccoonnttrrooll This topic defines who can fax where. By default, access is denied to everyone. Configuring this is mandatory. 22..33..11.. AAcccceessss rruulleess aanndd ggrroouuppss The mail to fax gateway may use several criteria to accept or reject a request. A rule is one combination of criteria that may be reused to control access to the various fax zones and fax aliases below. 22..33..22.. FFaaxx uusseerrss Some fax destinations are only available to specific users. You define them here. 22..33..33.. FFaaxx zzoonneess A fax zone associate a fax rule with a phone area. 22..33..44.. FFaaxx aalliiaasseess A fax alias associates a name with a phone number and a fax rule. This lets users fax to a name instead of to a phone number. 33.. AAcccceessss ccoonnttrrooll ddeettaaiillss As noted earlier, the email to fax gateway is universally available. The mail protocol has been designed to go through. Unless one pays attention, any mail to fax gateway is reachable from anywhere in the world. To make matters worse, this is generally just what most people need. To cope with that, the linuxconf email to fax gateway supports various schemes to limit access to this facility. Here they are: 33..11.. LLooccaall ffaaxxeess Whenever a mail message goes through a mail gateway, a new line is added in the envelope of the mail. This line tell us which gateway managed the message and when each received it. By counting the number of "Received" lines in the envelope, the fax gateway can tell if the mail originated from the local network or not. Linuxconf proposes this as a strategy to differentiate between faxes from the inside and faxes coming from the Internet. 33..11..11.. LLooccaall ffaaxxeess aanndd tthhee IInntteerrnneett Be aware that this is not 100% foolproof. If the email to fax gateway is visible from the Internet, anyone can telnet to it and inject a message in it. This will look like a local fax. To make sure the concept of "local faxes" is meaningful, you need some firewalling mechanism which isolates the fax gateway from the Internet. Then, the only way to reach it from outside would be to use at least another mail gateway. This would be detected as a non-local fax. 33..11..22.. TThhee ffaaxx ggaatteewwaayy iiss nnoott tthhee mmaaiill sseerrvveerr The email to fax gateway is not always the mail server of the organization. However, it is simpler if it is. If this is the case, the following solution may be used: +o Select the fax gateway as the smtp server for the email client you are using. In this way, it will receive all the messages firsthand. It will also be able to differentiate local messages from the others. +o Set the mail server of the fax gateway to your real mail server. Then, all messsages which are not faxes will be routed to the real mail server. 33..22.. FFaaxx uusseerrss You can define a list of users who can fax to various locations. A user is identified by his email address. You can also enter his PGP public signature. With this, the email to fax gateway will be able to certify that a fax message really came from the fax user. You can selectively tell if PGP signatures are needed for different fax destinations.