This is how the user owa forwarding has been disabled using the Exchange admin center.
To disable Forwarding from the OWA of all user we require following steps.
Go to Exchange admin center of global admin credentials.
Click on the Permission tab and then User Roles
Click on the Default Role Assignment Policy a pop up window will appear.
Uncheck the MyBasicOptions and then save
This will disable the forwarding of the user from the OWA.
Forwarding of the user will get disable and he wont be able to apply from his account.
For any other concerns related to Office 365 plan and subscriptions. You can reach out to us by submitting a ticket on our portal https://cloud.foetron.com/ or you can directly mail us at firstname.lastname@example.org. Check out our website www.foetron.com to know about the services offered by us.