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Chapter 11. Administration Issues with Electronic Mail
Electronic mail transport has been one of
the most prominent uses of networking since networks were devised.
Email started as a simple service that copied a file from one machine
to another and appended it to the recipient's
mailbox file. The concept remains the same,
although an ever-growing net, with its complex routing requirements
and its ever increasing load of messages, has made a more elaborate
scheme necessary.
Various
standards of mail exchange have been devised. Sites on the Internet
adhere to one laid out in RFC 822, augmented by some RFCs that
describe a machine-independent way of transferring just about
anything, including graphics, sound files, and
special characters sets, by email.[1]
CCITT has defined another standard, X.400. It is still used in some
large corporate and government environments, but is progressively
being retired.[1] Read RFC 1437 if
you don't believe this statement!
Quite a number of mail
transport programs have been implemented for Unix systems. One of the
best known is sendmail, which was developed by Eric Allman at the
University of California at Berkeley. Eric Allman now offers sendmail
through a commercial venture, but the program remains free software.
sendmail is supplied as the standard mail transfer agent (or MTA) in
some Linux distributions. We describe sendmail configuration in Chapter 12.sendmail
supports a set of configuration files that have to be customized for
your system. Apart from the information that is required to make the
mail subsystem run (such as the local hostname), there are many
parameters that may be tuned. sendmail's main
configuration file is very hard to understand at first. It looks as
if your cat has taken a nap on your keyboard with the Shift key
pressed. Luckily, modern configuration techniques take away a lot of
the head scratching.When
users retrieve mail on their personal systems, they need another
protocol to use to contact the mail server. In Chapter 15 we discuss a powerful and increasingly
popular type of server called IMAP.In this chapter, we deal with what email is and what issues
administrators have to deal with. Chapter 12
provides instructions on setting up sendmail for the first time. The
information included should help smaller sites become operational,
but there are several more options and you can spend many happy hours
in front of your computer configuring the fanciest features.For more
information about issues specific to electronic mail on Linux, please
refer to the Electronic Mail HOWTO by Guylhem
Aznar. The source distribution of sendmail also contains extensive
documentation that should answer most questions on setting it up.
