Avoid automatic subscription to group forum email notifications

Hi 

is there a way to avoid the subscription to the forums?

After the site subscription we have a procedure that automatically assigns the user to a role and automatically make the user as a member of a group where there are some forums.

After that the users are already subscribed to the forums email notifications.

Is there a way to avoid this behavior trough the control panel settings?

Is there a rest api endpoint to remove the forum email subscriptions for a specific user?

Thanks