I have a tree under Win2003. Parent domain aaa.com (Exhange 2003 installed) and child domain bbb.aaa.com (no Exchange installed). I want admin@xxxxxxxxxxx to have the ability to create e-mail boxes users@xxxxxxxx I've done /domainprep for bbb.aaa.com, and installed Exchange System Manager, all was OK. Now I am trying to make Exchange Recipient Update Service (RUS) for bbb.aaa.com,expecting that email boxes will appear in bbb.aaa.com, but it doesn't work! On creating RUS, I get an error: The RPC (child domain bbb.aaa.com) server is unavailable. Facility: Win32 ID no: c00706ba Exchange System Manager Does anyone have any experience in solving this problem? PS. I have found article http://support.microsoft.com/kb/271328/en-us but is not confident that it is my case.