email library

email function does not work,

$this->load->library('email');
$this->email->from('[email protected]', 'Admin');
$this->email->to('[email protected]');
$this->email->subject('Email Test');
$this->email->message('Testing the email class.');
if($this->email->send()){
echo 'Email enviado';
}
else{
show_error($this->email->print_debugger());
}

the error is
"
An Error Was Encountered
Unable to send email using PHP mail(). Your server might not be configured to send mail using this method.
"

what do i have to configure?
thanks