I have Exchange 2010 in hosting setup like:

• TMG 2010 as load balancer
• Exchange 2010 x 2 (CAS,MAILBOX,HUB on each server)
• AD1, AD2 machines
• File witness

All people currently connect thru OWA or POP3/SMTP and that works fine. The problem is autodiscovery doesn't work and RPC in terms of setting up Outlook doesn't work too. It doesn't work if I am connected with VPN or not. The thing is it used to work. Before reinstall of my machine 2 days ago I was able to get mails successfully thru Outlook that was set up using autodiscovery (but I was getting reports setting up of new clients wasn't working - so not sure why my outlook continued to work).

I used https://www.testexchangeconnectivity.com to track it down and basically the message is more or less this:

Attempting to ping RPC endpoint 6004 (NSPI Proxy Interface) on server autodiscover.domain.pl.
The attempt to ping the endpoint failed.

Additional Details
The RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime process.

I tried different solutions like disabling IP v6, followed couple of links and did all they proposed and it's still at the very same point:

C:\Users\admin>netstat -a | find "6001"
  TCP    0.0.0.0:6001           EXCHANGE2:0            LISTENING
  TCP    [::]:6001              EXCHANGE2:0            LISTENING

C:\Users\admin>netstat -a | find "6002"

C:\Users\admin>netstat -a | find "6003"

C:\Users\admin>netstat -a | find "6004"

I followed (and few others):

• http://helewix.com/blog/index.php/Microsoft-Solutions/2011/02/10/exchange-2010-how-to-open-ports-6001-6002-and-6004-on-your-server-for-telnet-to-work-and-rpc-to-be-able-to-connect-2
• http://blogs.technet.com/b/exchange/archive/2008/06/20/3405633.aspx
• http://messagexchange.blogspot.com/2008/12/outlook-anywhere-failing-rpc-end-points.html

Although most relate to Exchange 2007 and I have Exchange 2010 but there's not much things I can find on Exchange 2010 for the current problem. After applying all of those solutions error 6004 changed into error 6001 which doesn't bring me to my problems any closer.

At this point even thou error was 6001 and 6004 was no more the 6004 port was still closed while 6001 stayed open.

Attempting to ping RPC endpoint 6001 (Exchange Information Store) on server autodiscover.domain.pl.
The attempt to ping the endpoint failed.

Additional Details
The RPC_S_SERVER_UNAVAILABLE error (0x6ba) was thrown by the RPC Runtime process.

C:\Users\admin>netstat -a | find "6001"
  TCP    0.0.0.0:6001           EXCHANGE2:0            LISTENING
  TCP    [::]:6001              EXCHANGE2:0            LISTENING

C:\Users\admin>netstat -a | find "6002"

C:\Users\admin>netstat -a | find "6003"

C:\Users\admin>netstat -a | find "6004"

So I reverted back to square one. I suspect it's a problem with TMG but really can't be sure. I tried multiple combinations but all fail.