Change Primary SMTP address without changing the login name on Office 365

I came across a problem the other day where a user wanted to change their primary Email address on Office 365 without changing their Logon ID.

Basically, they wanted to change the users’ email address from user@domain.onmicrosoft.com to user@domain.com. However, they also wanted the user to keep using user@domain.onmicrosoft.com as their Microsoft Online Services ID (Login ID).

We fixed it up with a few simple Powershell commands.

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Firstly, log on to Office 365 using Powershell.

Then run the following Powershell command (where username is obviously the persons username you want to change):
Set-Mailbox username -WindowsEmailAddress username@domain.com

Voila, it’s done!