Had the following a few times now – Outlook Anywhere not working for Exchange 2010 SP1 when the Authentication method is set to Negotiate.
Event logs show the following;
Process ID: 5200
Process name: w3wp.exe
Account name: IIS APPPOOL\DefaultAppPool
Exception type: ConfigurationErrorsException
Exception message: Could not load file or assembly ‘WindowsLiveID, Version=0.0.0.0, Culture=neutral, PublicKeyToken=283dd9fa4b2406c5’ or one of its dependencies. The system cannot find the file specified.
In short, change from Negotiate to NTLM as Negotiate introduces the WindowsLiveID provider, and this causes Outlook to fail authentication (in short).
If NTLM is already enabled (or Basic) then make sure that the WindowsLiveID provider isn’t being inherited (look in IIS Manager under /RCP in the “Modules” bit