I am having a weird problem joining an Exchange 5.5 site using a new Win2K server (SP2)running Exchange 5.5. When I attempt to join the site, I get the message DS_E_COMMUNICATIONS_PROBLEM. And I can go no further. Connectivity with the existing Exchange server in the site seems fine. There are 400 users mailboxes on it and no problems there. I have also found that Sys Admins cannot use the Exchange Admin tool to connect to this server either - same message as above. I put a sniffer on the LAN and picked up RPC traffic between the two servers. The sniffer found the existing exchange server to be "rejecting an RPC connection for an "unspecified reason"" I have found some docs on the Technet site, but nothing relates to this problem. Has anyone else seen this behavior? SB