(For Windows 2008 R2 Enterprise and Exchange Serevr 2010 SP1) I have Exchange Server installed on my single server (thus it is my web server, DC and Exchnage Server for all roles). Outlook can connect to the server from the LAN and synch mail, but it fails from the WAN using Outlook Anywhere (nee RPC over HTTP). So I ran the testexchangeconnectivity.com test for RPC over HTTP, and everything was just fine, excpet for the last test, which returned the dreaded: "The RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime process." Since my CAS, Hub and Mailbox servers are all one and the same, there can't be any internal firewall issue. And since I can access Outllok Web App from the WAN, this proves that ports 80 and 443 are open (which I believe is all the ports that RPC over HTTP needs). My installation was all defaults, except that I specified that the sever was Internet-facing and provided my external mail address (mail.contoso.com). Since my Windows corporate domain is also my web site and mail site, my Windows AD domain is named constoso.com. Since I wanted to use the same URL inside the office (and NOT use dc.contoso.com, but rather use mail.contoso.com as I would outside the office), I modified the internal addresses for all CAS providers to https://mail.contoso.com/blabla. I have read up on ""The RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime process."", and know that it is common, but I have no idea how to diagnose the cause and fix it. Help greatly appreciated. TIA - mlavie

I should have specified that when I get the error message from testexchnageconnectivity.com, it is listed under the announcement: Attempting to ping RPC endpoint 6001 (Exchange Information Store) on server mail.contoso.com.

Could someone at least point me to an article with exact instruction how to diagnose this problem dependably. All I can find are blogs with lists of possible causes, with no definitive way of diagnosing the problem. TIA mlavie

Has this been answered? I have the exact same issue! I have also checked and RPC over HTTP is enabled on my 2011 SMB server running Exchange 2010 . Help