How to disable email forwarding for all users

Once logged in:

Click on the Domain Settings icon at the top.
Click on the User Defaults tab on the left.
Disable the Forward all email to another address option in the bottom-left.
Click the Propagate button at the top, then:
1. Check the Forward all email to another address box.
2. In the Push To drop down, select All Users.
3. Click Propagate.

Now, all email addresses (or usernames) for this domain are unable to setup email forwards within the secure.myvcgmail.com mail portal.