SMTP Error for free.fr

Yes, I modified email.php according to instructions int the 'Newsletter Readme.txt' file ...

#-------[ 1. OPEN ]---------------
#
    include/email.php
#
#-------[ 2. FIND ]---------------
#
    function pun_mail($to, $subject, $message, $from = '')
#
#-------[ 3. REPLACE WITH ]-------
#
    function pun_mail($to, $subject, $message, $from = '', $html = false)
#
#-------[ 4. FIND ]---------------
#
    $headers = 'From: '.$from."\r\n".'Date: '.date('r')."\r\n".'MIME-Version: 1.0'."\r\n".'Content-transfer-encoding: 8bit'."\r\n".'Content-type: text/plain; charset='.$lang_common['lang_encoding']."\r\n".'X-Mailer: PunBB Mailer';
#
#-------[ 5. REPLACE WITH ]-------
#
    if($html)
    {
        // HTML headers (thank you php.net documentation)
        $headers  = 'MIME-Version: 1.0' . "\r\n";
        $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
        $headers .= 'From: '.$from."\r\n".'Date: '.date('r')."\r\n".'X-Mailer: PunBB Mailer';
    }
    else
    {
        $headers = 'From: '.$from."\r\n".'Date: '.date('r')."\r\n".'MIME-Version: 1.0'."\r\n".'Content-transfer-encoding: 8bit'."\r\n".'Content-type: text/plain; charset='.$lang_common['lang_encoding']."\r\n".'X-Mailer: PunBB Mailer';
    }

-------------------------------------------------------------------------------

The name of the free.fr smtp is smtp.free.fr ...

Actually It works without smtp host. I did not specified any one. I use the php function to send emails ... But do you know what are the limits of this choice ? (for How many emails suscribed in the newsletter can I send a message ?)