<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 &TC;; 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 &TC;; 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 &TC;; 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>