public function send(Message $message, string $fingerprint)
    {
        if ($this->serverKeyFingerprint) {
            $this->mailer->send(
                // Encrypted, signed
                $this->encryptAndSign($message, $fingerprint)
            );
        } else {
            $this->mailer->send(
                // Encrypted, unsigned
                $this->encrypt($message, $fingerprint)
            );
        }
    }