<sect1 id="services-mail-overview">

    <title>Overview</title>

    <para>
        The mail service provides the software required to let you
        send/receive mail messages to/from others. The mail service is
        supported by three basic components: the Mail Transfer Agent
        (MTA), the Mail Delivery Agent (MDA) and the Mail User Agent
        (MUA). The MTA is the program your mail client sends mail
        messages to. The MDA, on the other hand, is the program your
        mail client reads mail message from (i.e., this is the program
        that lets you access your mailbox).  The saslauthd daemon is
        used by the MDA to authenticate user's credentials (e.g., the
        information required to grant access to an specific mailbox)
        and in some cases by the MTA to authenticate users before
        sending mail to it.  The MTA will listen on all network
        interfaces it is attached to and will receive mail sent to
        specific users inside specific domain names.
    </para>

    <para>
        Inside &TCD; there is support for different MTAs (e.g.,
        Sendmail, Postfix and Exim).  By default, the
        <application>Sendmail</application> program is used as mail
        transfer agent, however, we want to use Postfix for our
        configuration. This way, to use Postfix as default mail
        transfer agent and not Sendmail, it is required to use the
        <command>alternatives</command> command.  This command will
        present you a menu to chose between available mail transfer
        agents installed in the system, so you can choose Posfix as
        default option. Now that you've made Postfix the default mail
        transfer agent, you can saftly remove the sendmail package to
        avoid unused software to remain inside the computer.
    </para>

    <para>
        Inside &TCD; there is support for different MDA (e.g., Cyrus
        IMPA and Dovecot). By default, the Dovecot program is used as
        mail delivery agent (which doesn't require any intermediate
        daemon for athentication), however, we want to use Cyrus IMAP
        for our configuration (which does require an intermediate
        daemon called saslauthd for authentication).
    </para>

    <para>
        Inside &TCD; there is support for different MUA (e.g.,
        Evolution, Thunderbird and Mutt). By default, the Evolution
        program is used and we stay with it :).
    </para>

    <para>
        In this chapter we describe how to configure each one of these
        components to let you send/receive e-mails to/from your
        friends.
    </para>

</sect1>