I think this means that your FSMO PDC was unavailable to check account validation. Check your PDC is up and running and try again. Same error with Exchange 5.5 on NT4 if the NT PDC is unavailable, maybe the same rules apply here? Ian. "Suleyman Alkan" <suleyman.alkan@xxxxxxxxxx> on 09/05/2001 13:04:53 Please respond to win2kforum@xxxxxxxxxxxxx To: win2kforum@xxxxxxxxxxxxx cc: (bcc: Ian Paterson/P'Boro/UK/LEO) Subject: [win2kforum] No mapping hie everybody i have a problem with my win2k server i wanna make this server to the domain abc.com (abc.com domain controller is a win2k server also) and get this message "the following error occured attempting to join the domain "abc.com" No mapping between account names and security IDs was done" i reinstall the server, couldn't solve this problem. do you have any suggestion? ----- To unsubscribe, send a message to win2kforum-request@xxxxxxxxxxxxx and put "unsubscribe" in the subject of the message. To reach the administrator(s), send a message to win2kforum-admins@xxxxxxxxxxxxxx ----- To unsubscribe, send a message to win2kforum-request@xxxxxxxxxxxxx and put "unsubscribe" in the subject of the message. To reach the administrator(s), send a message to win2kforum-admins@xxxxxxxxxxxxxx