Add first name + first letter of last name alias to all users in exchange

exchange_create_firstl_alias.ps1

Get-Mailbox -resultsize unlimited |ForEach-Object {
  $u = $_ | Get-User
  if ($u.Lastname.length -gt 1 -and $u.FirstName.length -gt 0) {
    $new = (($u.FirstName) + ($u.LastName.Substring(0,1))).tolower() + "@example.com"
    Set-Mailbox $_.id -EmailAddress @{add=$new}
  }
}