Outlook keeps asking for credentials when connecting to Exchange 2010 server
Strange behavior occurred after installation of Update Rollup 3 for Exchange 2010, where Outlook users were constantly asked to provide credentials despite they were logged onto domain.
The problem was in Internet Information Server (IIS) RPC virtual application folder on which suddenly Windows authentication method was disabled.
After we enabled Windows authentication, it worked for 5 minutes and then authentication was automatically disabled again.
Second restart of HUB/CAS and MAILBOX server solved the problem.