I am working on an issue with Outlook Anywhere in Exchange 2013 where external and also internal users cannot connect. This is a new server co-existing with an Exchange 2010 server that will soon be decommissioned.

When I run an Outlook Connectivity test on testexchangeconnectivity.com I get the following error. I am not seeing anything in the application or system logs. I already applied CU 8 and am seeing the same results. External is a TMG and publishing to CAS 2013 server, which then proxy to CAS 2010

Testexchangeconnectivity.com
Attempting to ping RPC proxy <external Exchange URL>.
RPC Proxy can't be pinged.

Additional Details

An unexpected network-level exception was encountered. Exception details:
Message: The remote server returned an error: (500) Internal Server Error.
Type: Microsoft.Exchange.Tools.ExRca.Extensions.MapiTransportException
Stack trace:
at Microsoft.Exchange.Tools.ExRca.Extensions.MapiRpcTestClient.PingProtocolProxy(String endpointIdentifier)
at Microsoft.Exchange.Tools.ExRca.Tests.MapiPingProxyTest.PerformTestReally()
Exception details:
Message: The remote server returned an error: (500) Internal Server Error.
Type: System.Net.WebException
Stack trace:
at System.Net.HttpWebRequest.GetResponse()
at RpcPingLib.RpcPing.PingProxy(String internalServerFqdn, String endpoint)
at Microsoft.Exchange.Tools.ExRca.Extensions.MapiRpcTestClient.PingProtocolProxy(String endpointIdentifier)
Elapsed Time: 290 ms.

Outlook internal

When i autoconfigure outlook all is setup OK and client and Outlook works. Do i enable the use HTTPS on fast network. Close Outlook and start again i get a login prompt where i not can login does not accept credentials as in OWA i can login with these credentials. Do i change in the HOSTS file autodisover and webmail back to CAS 2010 it also works

SetupServer Internal Hostname External Hostname Auth.(Int.) Auth. (Ext.) Auth. IIS Last modified on: 
2010-EXC01  webmail.contoso.com Ntlm Ntlm Ntlm 11/04/2013 10:34:55 
2010-EXC02  webmail.contoso.com Ntlm Ntlm Ntlm 11/04/2013 10:34:55 
2013-EXC13 webmail.contoso.com webmail.contoso.com Ntlm Ntlm Basic Ntlm Negotiate 04/13/2015 17:40:09 
2013-EXC14 webmail.contoso.com webmail.contoso.com Ntlm Ntlm Basic Ntlm Negotiate 04/13/2015 17:40:32 

• Edited by dirkverhagen123 8 hours 41 minutes ago

Hi 

Can you please check your URLs for outlook anywhere? 
Do you have a 3rd party SSL certificate in place?
Get-ExchangeCertificate

After checking all the above if you find anything wrong then please change them to correct settings
Also recycle the app pool and see the results 

Hi Sathish,

see url's are set as above all on webmail.contoso.com

3rd part cert and its valid and applied to IIS

in iis logs i see MSRPC  500

iisreset has been done on 2010 servers.

HI

If all of your authentication, bindings, certificates, firewall settings and url's are fine and based on the error it might be an issue with rpc proxy component

It seems that RPC proxy component has corrupted on the CAS server
You can attempt a reboot off production hours and see if it helps you

Or you will need to  re-install RPC proxy component and test the URL again:
I have seen in few cases where reinstalling will end up as a fix 

Good Luck