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Mail Servers

In addition to Web server software, you'll also want mail server software. Your intranet would be severely limited without it, as electronic mail is such an integral part of the Internet and intranets. Before you choose a mail server, do your homework; you'll find notable differences in the installation processes and features of various mail server programs.

If you have a UNIX system, the mail server Sendmail probably was pre-installed on your machine. Sendmail, a popular, free (for UNIX users), and powerful software program is extremely complex: The configurations are endless. Sendmail uses SMTP (simple mail transfer protocol) and is considered one of the most difficult UNIX utilities to learn. However, many of the functions you'll need, such as mail forwarding, are already configured for you. If you want to customize Sendmail, get a good manual, because not only is it hard to configure, but there is a dearth of experts and consultants to advise users. The O'Reilly company offers one in its Nutshell series; to order the book, visit http://www.ora.com/www/item/sendmail.html.

If Sendmail is not your first choice, talk to your operating system vendor about other packages available for your platform. There may be less powerful but easier-to-configure mail server software packages available specifically for your machine. As far as UNIX is concerned, I've heard rumors that other mail server software is available, but I must confess I don't know anyone who uses anything other than Sendmail.

Before I look at some of the other mail server software programs available, I'll explore how a mail server communicates with its clients. When a user sends a message, a mail server accepts the message and requests to put the mail in someone's mailbox. If the user to whom the message is addressed does not have an account, the server will tell the machine sending mail to return the mail. This procedure is performed by one of two protocols: SMTP or POP (Post Office Protocol). The protocol used depends on the mail server package. Sendmail uses SMTP, but other packages, some of which I'll look at here, use POP. Because POP is basically the protocol that delivers mail on your system, whereas SMTP is what delivers the mail across the Web, users can utilize SMTP without POP, but they cannot use POP without SMTP. Think of SMTP as the central distribution point and POP as the local carrier. Sendmail basically delivers mail as far as the individual machine and POP delivers it to the individual user.

When looking at the various mail server packages, pay attention to the features that differentiate them. First, consider the ease with which you can install and configure a particular package. Mail servers are notorious for being cryptic and difficult to install. Second, check each mail package's capability to control the individual parameters of the users. If some of the users of your intranet are not too technical, you might want to have a preferences panel on the mail program that will allow them to configure their options. Central configuration files can help tailor an "average user's" configuration. Finally, as always, make sure that your mail server package comes with manuals and technical support contacts. A few mail server software programs and their main features follow.

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