If the registration flow doesn't ask for Accept Mail in Luminate, then a blank value will be sent down to LCRM. This is because Luminate CRM only accepts yes or no, so when it receives a blank value, it assumes the answer is no and that change will sync up to Luminate and change the mail opt-in to false. This is intended behavior, so when it comes to creating events in Luminate Online while integrated with Luminate CRM, then you will need to include the Accept Mail opt-in option in the registration flow.