Notification setting destination must be a valid email

{
  "error": {
    "type": "request_error",
    "code": "email_notification_setting_incorrect",
    "detail": "An email notification setting destination must be a valid email address.",
    "documentation_url": "https://developer.paddle.com/errors/notifications/email_notification_setting_incorrect"
  },
  "meta": {
    "request_id": "00000000-0000-0000-0000-000000000000"
  }
}