A Linux Email Server
Marcel Gagné
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Electronic mail is a strange beast. In the past few years, I've set up a number of electronic mail and Internet gateways. Some of my customers are smaller companies with a few employees and no desire to pay huge amounts of money for a 24x7 ISDN or DSL connection. They want to try out the Internet and email, and see how it fits into their corporate model without investing in a lot of hardware and software.
For companies such as these, Linux is made to order. Out of the box, your favorite Linux distribution comes with everything necessary to set up a complete Internet/intranet solution -- from email to Web servers and even firewalls. Best of all, in the spirit of Linux and open source, all the software is free!
Defining the Network
Imagine a local network consisting of the hot new Linux system and six PCs. The Linux server is at address 192.168.1.100, and the PCs are at addresses 192.168.1.31 through 192.168.1.36. The private internal network addressing scheme as defined in RFC1918 is used. I'll call the Linux server "mailserv". The fully qualified domain name is mailserv.mycompany.com.
Each PC has its own mail client. All mail traffic goes through the Linux server. For this article, I'll create a local mail server. For this example, I used a RedHat 6.0 system. There should be little here that does not directly relate to your specific distribution. Any RPM-based distribution (Caldera, TurboLinux, Mandrake) will behave in a similar manner.
The Components
As I mentioned, the Linux distribution will come with all the things you need to get up and running. On the server end, those things are a mail transport agent, or MTA, (Sendmail), and a local delivery agent, or LDA (usually a program called "deliver").
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