Office 365, Email, Exchange, How does changing NetID impact the Exchange service?
What happens to my Exchange username and email address when I change my NetID?
The Exchange username will be updated within 2 business days. You should continue to use your original username until it fails to work, and then you should switch to the new username.
Please note that your Active Directory password will remain the same during a NetID change. Your email address will be updated to reflect the new NetID, and you will continue to receive mail at the old address for one year.