Hello, Last we have migrated from Exchange 2000 to Exchange 2007. The Exchange 2007 server is now the only Exchange server in the organization. Now when I change the Mailbox Features properties of a User mailbox, I get the following error: -------------------------------------------------------- Microsoft Exchange Error -------------------------------------------------------- The following error(s) occurred while saving changes: set-casmailbox Failed Error: Active Directory operation failed on <servername>. This error could have been caused by user input or by the Active Directory server being unavailable. Please retry at a later time. Additional information: Additional information: The requested search operation is only supported for base searches. Active directory response: 00002120: SvcErr: DSID-03140264, problem 5012 (DIR_ERROR), data 0 . An operation error occurred. -------------------------------------------------------- OK -------------------------------------------------------- Both domain controllers are up and running. The Microsoft Exchange Best Practices Analyzer dont find any errors on the connections to the domain controllers. Have someone information about this error? And better a solution for this? Kind regards, Wilfred