about email library

I set follow code here

PHP Code:

$config['protocol'] = 'sendmail';
$config['mailpath'] = '/usr/sbin/sendmail';
$config['charset'] = 'iso-8859-1';
$config['wordwrap'] = TRUE;

$this->email->initialize($config); 


it error :

Exit status code: 1
Unable to open a socket to Sendmail. Please check settings.
Unable to send email using PHP Sendmail. Your server might not be configured to send mail using this method.