At a customer site users were experiencing “:-( Something went wrong” errors in OWA (2013). The RPC endpoint was also broken, blocking a migration to Office 365.

Initial checks showed a few errors on the 2013 frontend server:

[Eas] Marking ClientAccess 2010 server NLEX01.domain.local (https://nlex01.domain.local/Microsoft-Server-ActiveSync) as unhealthy due to exception: System.Net.WebException: The remote server returned an error: (503) Server Unavailable.
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.Exchange.HttpProxy.ProtocolPingStrategyBase.Ping(Uri url)

[Autodiscover] Marking ClientAccess 2010 server NLEX01.domain.local (https://nlex01.domain.local/Autodiscover) as unhealthy due to exception: System.Net.WebException: The remote server returned an error: (503) Server Unavailable.
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.Exchange.HttpProxy.ProtocolPingStrategyBase.Ping(Uri url)

[RpcHttp] Marking ClientAccess 2010 server NLEX01.domain.local (https://nlex01.domain.local/rpc/rpcproxy.dll) as unhealthy due to exception: System.Net.WebException: The remote server returned an error: (503) Server Unavailable.
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.Exchange.HttpProxy.ProtocolPingStrategyBase.Ping(Uri url)

[Owa] Marking ClientAccess 2010 server NLEX01.domain.local (https://nlex01.domain.local/owa) as unhealthy due to exception: System.Net.WebException: The remote server returned an error: (503) Server Unavailable.
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.Exchange.HttpProxy.ProtocolPingStrategyBase.Ping(Uri url)

The issue ended up being twofold;

1. somehow the SCCM client on the Exchange backend had replaced the local server certificate that IIS uses, this certificate wasn’t accepted by the frontend server
2. for some reason NTLM (Windows) Authentication was switched off on the Virtual Directories on the backend machine.