4. Now edit the default email address. Because mine is set as an alternate UPN I can click the SMTP address and click 'Edit'.
6. Click 'Next' to apply changes immediately.
7. Click 'Edit' to make the changes.
8. This dialog shows the Power Shell script along with any warnings. I have an invalid recipient name from my old Exchange 2003 organisation that I must get round to changing! ;-)
9. All done and applied. I like how the 'True' display lets you know that you did apply the policy.