Frontend\Modules\Mailmotor\Validator\Constraints\EmailSubscriptionValidator::validate PHP Method

    public function validate($value, Constraint $constraint)
    {
        try {
            // The email is already in our mailing list
            if ($this->subscriber->isSubscribed($value)) {
                $this->context->buildViolation($constraint->alreadySubscribedMessage)->addViolation();
            }
            // fallback for when no mail-engine is chosen in the Backend
        } catch (NotImplementedException $e) {
            // do nothing
        }
    }