Verify Outlook Cached\Online Mode

I had a situation recently where a 2003 client was supposed to be in cached mode but behaved as if it were in online mode.

We found that the registry had been modified and set to online mode from the registry and not from GPO or GUI.

Here is where you can check to verify.

HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\ProfileName\13dbb0c8aa05101a9bb000aa002fc45a36601 holds the cached mode settings

    • dword: 04 00 00 00 disables,
    • dword: 84 01 00 00 enabled Cached Mode

Random issue with Outlook 2003 accessing Exchange 2010.

Possible Symptom

  • Slow or hangs when accessing shared calendar or public folder information from outlook 2003
  • Delay in email
  • Errors
    • “Unable to open your default e-mail folders. The Microsoft Exchange Server computer is not available. Either there are network problems or the Microsoft Exchange Server computer is down for maintenance.”
    • “Unable to expand the folder. The set of folders could not be opened.”


3 Possible causes

  1. RPC Throttling
    • Here is a very good article on it
    • In a nutshell you need to set a policy that will increase “RCAMaxConcurrency”
      • As a testing step run this:
        Get-ThrottlingPolicy | set-ThrottlingPolicy –RCAMaxConcurrency $null
      • If it does resolve the issue follow the article above to set a new policy correctly and revert the test setting
        Get-ThrottlingPolicy | set-ThrottlingPolicy -RCAMaxConcurrency 20
  2. UDP notification
    • Solution is to put the 2003 Outlook client in cached mode.
  3. Genuine network issues (here are some general tips)
    1. Check cabling
    2. Check Switch Logs
    3. Try to isolate client to server to eliminate network issues as a cause.
    4. Disable TOE and RSS on NICS
    5. Check that the NIC and the switches are running the same speed and duplex
    6. Use a sniffer to inspect traffic.