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When to Run a
Pull Mail Server
Suppose you want to provide e-mail services
to a small office, clients of an ISP, or some other group of users. The push
mail servers that come with all Linux systems, and that are described in
you to set up a server to receive incoming e-mail addressed to your users. The
question then becomes: How do you provide access to the mail that the mail
server computer is collecting? There are two main approaches to this
problem: You can provide users with login accounts on the
mail server computer and allow users to read mail locally, using Linux e-mail
programs like pine , mutt , or KMail (known technically as mail user
agents, or MUAs ). These programs can
read the incoming mail spools directly, so they don't need any special support
software. This approach requires users to either sit at the mail server
computer proper or log into it remotely, using protocols like Telnet, Secure
Shell (SSH), or some form of X-based remote login. (
Maintaining Remote Login Servers, and
Access with X and VNC Servers, discuss such servers in more detail.) You can run a pull mail server, which allows
users to run mail readers on their own computers in order to read the mail
that's been collected on the mail server. The mail readers function as pull
mail clients to the mail server computer's pull mail server program. The pull
mail server program effectively takes the role of the local
mail reader, filling in for the remote mail reader used by the user.The first option was common when UNIX systems
served as the only real computers in organizations, and users accessed the UNIX
computers through dumb terminal hardware. Today, though, users prefer to use
GUI programs, often running in Windows or MacOS, to read their mail. Although
there are local GUI mail readers that run on Linux, they require that the user
run an X server, which is uncommon on Windows and MacOS systems. For this and
other reasons, the second approach is usually more convenient for users who sit
at Windows or MacOS computers.From the user's point of view, the mail
reader needs to be configured with the hostname or IP address of the pull mail
server, and mail can be checked by launching the mail reader and clicking a
button. Many mail readers can periodically check for new e-mail, so the button
click may not even be necessary.Thus, running a pull mail server makes sense
when you want to provide access to your e-mail server for users who want to run
mail readers on their own computers, without logging in to the mail server
using tools like Telnet or SSH. Pull mail servers are commonly used on local
corporate and educational networks, as well as by ISPs, who use it to provide
e-mail to subscribers. These servers can support just a handful of users or
many thousands of them when given adequate hard disks, network connections, and
other hardware resources.
