UPN issue.

In effort to migrate our Exchange 2010 users to O365, we have discovered we have a lot of users with duplicated UPNs.  

For ex, in the attached, the user login using adlopez but her User Logon Name in AD is "alopez".  There is also another users with that User Logon Name.  

2 questions:

1. Can I just rename and enter adlopez in the User Logon Name field without causing any issue?
2. Is User Logon Name is the same as UPN?

Thanks.
adlopez.png
nav2567Asked:
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☁ François Peroux ☁Infrastructure Consultant - Cloud Solutions | Consultant Infrastructure - Solutions CloudCommented:
Hello,

The best practice in your case is to use a specific tool for your scenario. IdFix tool will help you to proceed and change duplicate attributes as UPN.

You can find this tool here : https://www.microsoft.com/en-us/download/details.aspx?id=36832.

Let me know !
nav2567Author Commented:
Thanks.

Do you know the answer of my questions?
☁ François Peroux ☁Infrastructure Consultant - Cloud Solutions | Consultant Infrastructure - Solutions CloudCommented:
1. Yes you can rename it. Sometimes, it could arrive that a new profile is created on the user machine (but not in all case). Juste be prepared if this occurred.

2. It's a long story, here some details :

Legacy User Logon Name
The User Logon Name (Pre-Windows 2000) is the legacy format from Windows NT and is often referred to using the raw attribute name of sAMAccountName. This field is limited to a maximum of 20 characters and is used in conjunction with the legacy (or NetBIOS) domain name.

User Logon Name
The User Logon Name is a the newer username format which is often mistakenly referred to as the User Principal Name (UPN).  That term is used to indicate the entire user name and domain name format.comprised of the User Logon Name and the UPN Suffix which is shown in the drop-down menu in the screenshot below.

You can find more details about it here : http://blog.schertz.name/2012/08/understanding-active-directory-naming-formats/

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Adam BrownSr Solutions ArchitectCommented:
There should be no impact on changing the UPN (which is what the User Logon name is called) unless you are already syncing AD with Office 365 (In which case, you may need to manually reassign the log on name in the cloud to match the users, and possibly some other things). User profiles are mapped to the user's SSID, which does not change as long as the user has the same account object in AD. If you delete a user permanently and create a new account for them, that would cause new profile creation, but making changes to the login name(s) will not.
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