How i set up the tracking option "Request delivery receipt" as a default to all my organization outbound emails?

This is a client-side option, so it needs to be configured on each client/device. If you are managing all the involved devices, you can rollout GPO/reg keys or use the cloud policy service to configure the corresponding option in Outlook. This will still not cover any other email clients, such as the mobile apps.

Alternatively, you can explore a server-side solution that automatically adds the Disposition-Notification-To header to any outgoing messages. Unfortunately, such functionality is not available by default in Exchange Online, so you will have to route messages through a different MTA first. Best you can do with the built-in tools is create a mail flow rule that uses a hardcoded value for Disposition-Notification-To, meaning all receipts will be send back to a single address.