The following article contains illustrated steps on how to update or change a user's Primary Login Name or UPN. When chaining the primary login for a user, the address must be unique and cannot exists within your organization.
Example: Jane Doe - firstname.lastname@example.org wants to be changed to Jane Smith - email@example.com.
The Name will appear in the Global Address List or GAL unchanged until the GAL updates at 12 AM.
Changing a user's Login Name
1. Open your web browser of choice and navigate to your Administrative Control Panel, at https://cp.securembox.com, and sign in using your administrative login.
2. Next, select User List under My Users, to populate your user list, highlight your desired user from within the list and click Edit User.
3. Once the User Record populates, you will see the user's primary Login address at the top. Simply Change the name and click the Update Login link.
Please note that the new login address does not auto fill within the Alias Listing. If the login is to receive email then the address must be added as an alias.
How to Add an E-mail Alias to an Exchange User