If user's cannot connect to the Out'n About! for Outlook Server and you are sure the service is running, you probably have a firewall that is not allowing TCP/IP port 23079 inbound on the server.
Since there are so many firewall products available, we will only discuss the Windows Firewall built into Windows XP to Windows 10. If you are using another firewall product, contact your IT Administrator.
To manually allow incoming traffic on TCP port 23079 for an XP SP2 machine running as an Out'n About! for Outlook Server, open Windows Firewall in the Windows Control Panel, switch to the Exceptions tab and click the Add Port button. Then type 'Out'n About!' for the new exception and specify that TCP port 23079 be statically opened for unsolicited inbound traffic:
Now click OK and the new exception for Out'n About! is displayed in the firewall exceptions list.