Not sure if anyone else has seen this, but ever since we updated our Exchange 2010 to SP2 RU1 we are getting loads of errors in the Event logs.
The users all seem to be able to connect fine, but it logs this error every time someone connects to their mailbox in our second (non-internet-facing) AD site. No errors are logged if the user has a mailbox in our internet facing AD site. These seem to be a little misleading, since the sign-in does not actually fail, it just gets proxied.
Event Viewer Details:
Source: MSExchange OWA
Task Category: Proxy
Event ID: 136
Details:
The sign-in to Outlook Web App failed. User ExchangeDN has a mailbox on 14.2.247.0 server version. However, no Client Access server or front-end server with a matching version was found to handle the request.
For users on Exchange 2007 and above, you can configure the Outlook Web Access URL for redirection using the externalURL parameter on the Exchange /owa virtual directory.