Hi Alessandro, Is the boss's computer running windows 2000? I had a similar problem, and I entered the following registry modifications. This solved my problem. Please let me know if this works for you. Mark ------------------------------------ Mark Budman Systems Engineer Devry College of Technology 5860 Chedworth Way Mississauga, ON L5R 3W3 mbudman@xxxxxxxxxxxx (905) 502-5193x6235 / (800) 249-5777 ------------------------------------ If you are running Outlook 2000 and Windows 2000 and you are getting the message "Microsoft Exchange Address Book was unable to log on to the Microsoft Exchange Server computer. Contact your system administrator if the problem persists.", check for these registry entries on your client machine. If they are not there, add them and it will probably fix your problem.: Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\ClientProtocols] "ncacn_np"="rpcrt4.dll" "ncacn_ip_tcp"="rpcrt4.dll" "ncadg_ip_udp"="rpcrt4.dll" "ncacn_nb_tcp"="rpcrt4.dll" "ncacn_http"="rpcrt4.dll" Subject: Outlook 2000 connection problem From: "alessandro dell'anna" <alessandro.dellanna@xxxxxxxxxxxxx> Date: Thu, 9 May 2002 10:00:00 +0200 X-Message-Number: 8 Hi all, =A0 I=92ve just installed Outlook2000 an a fresh installed computer an a = local network with a fine working domain structure. I have 140 Mailbox = enabled user =A0on the Exchange 2000 server and all client Outlook works = fine.=20 Only 1 (but the client of the big BOSS ... ach !) client doesn=92t = start. I install the Microsoft Exchange Server service in the client, I = type the server name and the mailbox name but when I try to check the = connection the response is =93Unable to connect to the server=94. If I = change the username the results is the same. If I change computer and = type the same username all goes right. Note that the computer browse the = network correctly, open shared folder on the exchange server and so on = ....=20 =A0 Have you any ideas ? =A0 Alessandro Dell=92Anna =A0