Mac OS Download Page To download the Mac OS X (FirstClass client version 11) click here. To download the Mac OS 9 (FirstClass client version 8.1) click here. Once the installation is complete click here. When the Login screen appears, simply enter your user ID and password and click Login.            For more information about the Mac OS 9 FirstClass click here. For more information about the Mac OS X FirstClass click here. Visit the FirstClass web site to download international clients.