Add @onmicrosoft e-mail address on every mailbox with PowerShell

$users = Get-Mailbox -ResultSize Unlimited -Filter {EmailAddresses -notlike “*@contoso.mail.onmicrosoft.com*”}
foreach ($user in $users) {

$alias=$user.alias

$email=$alias + “@contoso.mail.onmicrosoft.com”

Set-mailbox $user.Identity -EmailAddresses @{add=$email}
}