function apop ($login,$pass) {
        //  Attempts an APOP login. If this fails, it'll
        //  try a standard login. YOUR SERVER MUST SUPPORT
        //  THE USE OF THE APOP COMMAND!
        //  (apop is optional per rfc1939)

        if(!isset($this->FP)) {
            $this->ERROR = "POP3 apop: " . _("No connection to server");
            return false;
        } elseif(!$this->ALLOWAPOP) {
            $retVal = $this->login($login,$pass);
            return $retVal;
        } elseif(empty($login)) {
            $this->ERROR = "POP3 apop: " . _("No login ID submitted");
            return false;
        } elseif(empty($pass)) {
            $this->ERROR = "POP3 apop: " . _("No password submitted");
            return false;
        } else {
            $banner = $this->BANNER;
            if( (!$banner) or (empty($banner)) ) {
                $this->ERROR = "POP3 apop: " . _("No server banner") . ' - ' . _("abort");
                $retVal = $this->login($login,$pass);
                return $retVal;
            } else {
                $AuthString = $banner;
                $AuthString .= $pass;
                $APOPString = md5($AuthString);
                $cmd = "APOP $login $APOPString";
                $reply = $this->send_cmd($cmd);
                if(!$this->is_ok($reply)) {
                    $this->ERROR = "POP3 apop: " . _("apop authentication failed") . ' - ' . _("abort");
                    $retVal = $this->login($login,$pass);
                    return $retVal;
                } else {
                    //  Auth successful.
                    $count = $this->last("count");
                    $this->COUNT = $count;
                    return $count;
                }
            }
        }
    }