Hi Greg! The problem is RPC over HTTP connections NOT RPC connections. I don't define any static ports for RPC connection. I have a strange behaviuor if I access my Exchange front-end through "RPC over HTTP": 1) Administrator can access 2) All other user cannot access. Outlook gives an error message "Invalid Bookmark". What is that? How can I solve this problem? Externally connect through RPC over HTTP does not work! Best Regrads Mustafa