Office 365 change login from to

ajdratch used Ask the Experts™
I am setting up a client on Office 365. I'm doing the express migration.  All the accounts have sync’d.

I started migrating a couple of accounts and the migration works. Their mailbox is created and they have all their aliases assigned to their account.
The problem is the login user name is and I can’t change it.

Their primary SMTP address is It shows this is the primary address on-prem and when I look at their mailboxes in Exchange Admin Center online.
I need to figure out how to get this to change so their primary email address is also their login address before I can migrate any more users.
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
Most Valuable Expert 2015
Distinguished Expert 2018

Define "express" migration, did you opt-in to install the AAD Connect tool or just did the one-time sync? And if you installed it, did you make any changes to the default config and/or sync rules?

What is the value of the on-premises userPrincipalName attribute? If it's populated with the same suffix, it should be correctly synced to O365.
Server engineer
Change the UPN on onpremise object to

Since you cannot change an object which is synced with azure ad connect.

Thumb rule: UPN should match primary email address.

You have to do this before migrating a user.


I had the option for "Cutover" or "Express Migration." I choose Express Migration.

I did install AAD connection tool and it is running now. The only change i made to the default was specifying the OU to sync.

I can sync and migrate accounts and they will pick up all the user's email addresses but it will not change the username to match the Primary Address. The  username is still

The Windows domain is They do not own that so it is not getting migrated to Office 365. The user's principal name Their primary email address is firstname


I changed the UPN to match the email address in Attribute editor, ran the sync and it updated the login name.

This did work for users who were already sync'd.

I was on the phone with Office 365 support for over an hour and it was obvious they did not have any ideas.

Thanks so much
Saif ShaikhServer engineer

Welcome ..

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial