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22.

The <ulink url="http://www.debian.org/">Debian web site</ulink> contains a large quantity of documentation about Debian. In particular, see the <ulink url="http://www.debian.org/doc/FAQ/">Debian GNU/Linux FAQ</ulink> and the <ulink url="http://www.debian.org/doc/user-manuals#quick-reference">Debian Reference</ulink>. An index of more Debian documentation is available from the <ulink url="http://www.debian.org/doc/ddp">Debian Documentation Project</ulink>. The Debian community is self-supporting; to subscribe to one or more of the Debian mailing lists, see the <ulink url="http://www.debian.org/MailingLists/subscribe"> Mail List Subscription</ulink> page. Last, but not least, the <ulink url="http://lists.debian.org/">Debian Mailing List Archives</ulink> contain a wealth of information on Debian.

25.

Today, email is an important part of many people's life. As there are many options as to how to set it up, and as having it set up correctly is important for some Debian utilities, we will try to cover the basics in this section.

26.

There are three main functions that make up an e-mail system. First there is the <firstterm>Mail User Agent</firstterm> (MUA) which is the program a user actually uses to compose and read mails. Then there is the <firstterm>Mail Transfer Agent</firstterm> (MTA) that takes care of transferring messages from one computer to another. And last there is the <firstterm>Mail Delivery Agent</firstterm> (MDA) that takes care of delivering incoming mail to the user's inbox.

27.

These three functions can be performed by separate programs, but they can also be combined in one or two programs. It is also possible to have different programs handle these functions for different types of mail.

28.

On Linux and Unix systems <command>mutt</command> is historically a very popular MUA. Like most traditional Linux programs it is text based. It is often used in combination with <command>exim</command> or <command>sendmail</command> as MTA and <command>procmail</command> as MDA.

29.

With the increasing popularity of graphical desktop systems, the use of graphical e-mail programs like GNOME's <command>evolution</command>, KDE's <command>kmail</command> or Mozilla's <command>thunderbird</command> (in Debian available as <command>icedove</command><footnote> <para> The reason that <command>thunderbird</command> has been renamed to <command>icedove</command> in Debian has to do with licensing issues. Details are outside the scope of this manual. </para> </footnote>) is becoming more popular. These programs combine the function of a MUA, MTA and MDA, but can &mdash; and often are &mdash; also be used in combination with the traditional Linux tools.

30.

Default E-Mail Configuration

31.

Even if you are planning to use a graphical mail program, it is important that a traditional MTA/MDA is also installed and correctly set up on your Linux system. Reason is that various utilities running on the system<footnote> <para> Examples are: <command>cron</command>, <command>quota</command>, <command>logcheck</command>, <command>aide</command>, &hellip; </para> </footnote> can send important notices by e-mail to inform the system administrator of (potential) problems or changes.

32.

For this reason the packages <classname>exim4</classname> and <classname>mutt</classname> will be installed by default (provided you did not unselect the <quote>standard</quote> task during the installation). <classname>exim4</classname> is a combination MTA/MDA that is relatively small but very flexible. By default it will be configured to only handle e-mail local to the system itself and e-mails addressed to the system administrator (root account) will be delivered to the regular user account created during the installation<footnote> <para> The forwarding of mail for root to the regular user account is configured in <filename>/etc/aliases</filename>. If no regular user account was created, the mail will of course be delivered to the root account itself. </para> </footnote>.

33.

When system e-mails are delivered they are added to a file in <filename>/var/mail/<replaceable>account_name</replaceable></filename>. The e-mails can be read using <command>mutt</command>.