fetch-same-username-from-upn.ps

# Get users with same username part of UPN
$users = get-azureaduser -all:$true

foreach($user in $users)
{
    # do we have more users with the same username-part of the UPN?
    $username = $user.userprincipalname.split("@")[0]
    if ( ($users | ? {$_.userprincipalname -like "$($username)@*"} | Measure-Object).count -gt 1)
    {
        write-output "$($user.userprincipalname)`t$($user.mailnickname)"
    }
}