Thanks for reply, you think like this (last three lines)?
Mail::Send(
$mail_id_lang,
'new_order',
sprintf(Mail::l('New order : #%d - %s', $mail_id_lang), $order->id, $order->reference),
$template_vars,
$merchant_mail,
null,
$configuration['PS_SHOP_EMAIL'],
$configuration['PS_SHOP_NAME'],
null,
null,
$dir_mail,
null,
$id_shop,
null,
$replyTo,
$replyToName
);
And $replyTo and $replayToName I should define in mail.php, isn't it?