Change a user name in Office 365
As the Office 365 admin, you may need to change the user name for someone in your organization, if, for example, someone gets married and their last name changes. When you change a user name, the user's primary email address, which is the same as the work or school account the user uses to log into Office 365, also changes.
This topic explains how to quickly change a user name and calls out a few things to keep in mind so your users can continue to connect their accounts to Outlook, SharePoint, and Lync on their computers and mobile devices.
What do you want to do?
Change a user name
Use this procedure to change a user name and email address.
Sign in to Office 365 with your work or school account.
Go to the Office 365 admin center.
Go to Users > Active users.
Select the user you want to edit, and select Edit.
Select the Details tabs, and change the user name.
Complete your changes, and then select Save.
Let the person know what their new user ID is. They’ll need it to sign in.
What else should your users know
Changing the user name triggers a re-provisioning of the user in Lync Online. If your users are on Lync Online, they will have to reschedule any Lync Online meetings, and tell their external contacts to update the old contact.
If the user has changed their password as well as their user name, they will be prompted to enter the new password on their mobile device on the next sync.