Change UserPrincipalName + Suffix With a scheduled Windows task

You have completed the domain work in relation to your O365 tenancy, however the usernames replicated to AAD are in “username@old” format.

Most organizations have inherited a “username@old-domain.local” suffix. Time goes on and the organization changes its name, amalgamates, etc, for whatever reason, effectively changes its name.

The target of the script is the group a on-prem active directory group.

The following script will serve to allow you to run the script wrapped in a scheduled task in order to change the full upn for the usernames in the group with from “username@old-company.local”(no joke intended), through to “” format.

I have used the script on a nightly basis but do not see the reason to run it more frequently.

Import-Module ActiveDirectory
$group = "O365 Users"
$newsuffix = ""
$users = get-adgroupmember -Identity $group |Get-ADUser |sort userprincipalname
$from = ""
$to = ""
$tofailedrecipient = ""

foreach ($user in $users){
    $upn = (($user.givenname)+"."+($user.surname)+"@"+$newsuffix).tostring()
    $upnfromad = ($user.userprincipalname).tostring()
    if ($upn -notmatch $upnfromad) {
            $emailbody = "<HTML><HEAD><META http-equiv=""Content-Type"" content=""text/html; charset=iso-8859-1"" /><TITLE></TITLE></HEAD>"
            $emailbody = "<BODY bgcolor=""#FFFFFF"" style=""font-size: Small; font-family: Arial; color: #000000""><P>"
            $emailbody += "<p>The following UPNs have been updated:</p>"
            Set-ADUser -Identity $user.SamAccountName -UserPrincipalName "$($user.GivenName).$($user.Surname)@$newsuffix"
            $emailbody += $upn
            $emailbody += "<br>"
            $successMessageParameters = @{
                        Subject = "The following addresses have been updated - $((Get-Date).ToShortDateString())"
                        Body = $emailbody
                        From = $from
                        To = $to
                        SmtpServer = "x.x.x.x"
                        BodyAsHTML = $true
            $emailbody += "<p>Regards,</p>"
            $emailbody += "<p>Your friendly Office 365 team</p>"
            Send-MailMessage @successMessageParameters
        Catch [Exception] {
            $ErrorMessage = $_.Exception.Message
            $failedMessageParameters = @{
                        Subject = "The following error was encountered when attempting to update the UPN's"
                        Body = ("'$ErrorMessage'") | Out-String
                        From = $from
                        To = $tofailedrecipient
                        SmtpServer = "x.x.x.x"
            Send-MailMessage @failedMessageParameters -BodyAsHtml