Try changing in sources/subs/ Notifications.class.php this:
$this->register(2, 'email', array($this, '_send_email'), array('subject' => 'subject', 'body' => 'body'));
$this->register(3, 'email_daily', array($this, '_send_daily_email'), array('subject' => 'subject', 'body' => 'snippet'));
$this->register(4, 'email_weekly', array($this, '_send_weekly_email'), array('subject' => 'subject', 'body' => 'snippet'));
to:
$this->register(2, 'email', array($this, '_send_email'), array('subject' => 'subject', 'body' => 'body', 'suffix' => true));
$this->register(3, 'email_daily', array($this, '_send_daily_email'), array('subject' => 'subject', 'body' => 'snippet', 'suffix' => true));
$this->register(4, 'email_weekly', array($this, '_send_weekly_email'), array('subject' => 'subject', 'body' => 'snippet', 'suffix' => true));