public function export(string $fingerprint): string
    {
        $gnupg = new \Crypt_GPG($this->options);
        try {
            $gnupg->addEncryptKey($fingerprint);
            return $gnupg->exportPublicKey($fingerprint, true);
        } catch (\PEAR_Exception $ex) {
            throw new GPGMailerException(
                'Could not export fingerprint "' . $fingerprint . '": ' .
                    $ex->getMessage(),
                $ex->getCode(),
                $ex
            );
        }
    }