Office 365 - Change all emails to first.lastname@domain but keep the login email

Thank you for your reply Michev
these users are in cloud only
unfortunately i did not find any way to do the firstname.lastname from the link provided

You're supposed to prepare a CSV with that data and use it as input. If you want to do it all "dynamically" you can use something like this:

Get-User -RecipientTypeDetails UserMailbox | % { Set-Mailbox $_.UserPrincipalName -WindowsEmailAddress "$($_.FirstName)`.$($_.LastName)@domain.com" -WhatIf}

This of course is a very simple example which lacks any error checking, and should be used just to illustrate the idea.

Thank you,

eventually i was able to solve it without csv:

Get-User -RecipientTypeDetails "UserMailbox" -ResultSize Unlimited | Select-Object firstname , lastname, WindowsEmailAddress | ForEach-Object {

        $newUPN = '{0}.{1}@domain.com' -f $_.firstname,$_.lastname
        $user = $_.WindowsEmailAddress

        Try{                
             #Set-Mailbox -Identity $_.WindowsEmailAddress -WinldowsEmailAddress $newUPN
             Write-Host $newUPN
           }
        Catch{
            Write-Output "####################"
            Write-Output $user
            Write-Output $ErrorMessage = $_.Exception.Message
            Write-Output $FailedItem = $_.Exception.ItemName
            Write-Output "####################"

You definitely should add some additional checks, to address scenarios where FirstName and/or LastName are empty, etc. But yeah, that's the general idea, the rest is just proper coding :)

Yes you are right! I will re-check again

Thank you so much for your help