Exchange 2000 Server - Server Access

Check for a network problem on the server.
Verify that Chat Service is not paused or stopped on the server.
Go to the chat community's General tab and check the Maximum total connections value. If this number is not large enough, Chat Service will deny connections from all clients. You can modify this setting without stopping and restarting Chat Service.
Note The maximum number of server connections represents the total number of anonymous, authenticated, and unknown connections on the server.
Tip You can also check the total number of connections by logging on to a chat client as a sysop and using the Lusers command.

Go to the community's General tab and check the Maximum anonymous connections value. If this number is not large enough, Chat Service will deny all connections from anonymous clients. You can modify this setting without stopping and restarting Chat Service.
Check User Classes to determine whether a user class is preventing anonymous clients from connecting to the community. Specifically, check the Logon method setting in the Access tab of the class.

Go to the community's General tab and check the Maximum total connections value. If this number is not large enough, Chat Service will deny connections from all clients. You can modify this setting without stopping and restarting Chat Service.
Check User Classes to determine whether a user class is preventing authenticated users from connecting to the server. Specifically, check the Logon method setting in the Access tab of the class.
Verify that the authentication package you are using is configured and working properly. See the documentation in your authentication package for information.

Check Banned Users to determine whether a ban is in effect for users from this domain.
Check User Classes to determine whether a user class is banning users from this domain.