Oscommerce website gives an emailing error.

I am using oscommerce on my commerce website. I am getting the following message at the point where the site send an email to a customer, like sending password to the customer. The site is on Windows 2003 with IIS 6.

Warning: mail() [function.mail]: Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in e:\webaddress\shop\includes\classes\email.php on line 500

The related code on line 500 is: return mail($to, $subject, $this->output, 'From: '.$from.$this->lf.implode($this->lf, $this->headers).$this->lf.implode($this->lf, $xtra_headers));

The following is the subsequent codes around line 500.

if (EMAIL_TRANSPORT == 'smtp') {
       return mail($to, $subject, $this->output, 'From: '.$from.$this->lf.implode($this->lf, $this->headers).$this->lf.implode($this->lf, $xtra_headers));

       
       
        /*
        require_once(DIR_WS_CLASSES . "class.phpmailer.php");

            $pMail = PHPMailer();
            
            $pMail->From     = $from_addr;
            $pMail->FromName = $from_name;
                        
            $pMail->IsSMTP();
            $pMail->Host     = localhost;      // replace with your smtp server
                        
            $pMail->Subject = $subject;
            $pMail->Body    = $this->output;
            $pMail->AddAddress($to_addr, $to_name);
            $pMail->IsHTML(true);
                        
            return $pMail->Send();
            
            $pMail->ClearAddresses();
            $pMail->ClearAttachments();
            */
            
      } else {
        return mail($to, $subject, $this->output, 'From: '.$from.$this->lf.implode($this->lf, $this->headers).$this->lf.implode($this->lf, $xtra_headers));
      }
    }
 


Can someone help? Many thanks.