protected function authLogin()
    {
        $in = "AUTH LOGIN" . $this->CRLF;
        $code = $this->pushStack($in);
        if ($code !== '334'){
            throw new CodeException('334', $code, array_pop($this->resultStack));
        }
        $in = base64_encode($this->username) . $this->CRLF;
        $code = $this->pushStack($in);
        if ($code !== '334'){
            throw new CodeException('334', $code, array_pop($this->resultStack));
        }
        $in = base64_encode($this->password) . $this->CRLF;
        $code = $this->pushStack($in);
        if ($code !== '235'){
            throw new CodeException('235', $code, array_pop($this->resultStack));
        }
        return $this;
    }