My hard drive died in my home computer about two weeks ago. Rather than reinstall Windows XP SP2, I went ahead and installed Windows Vista 64-bit. Everything has been great, with the exception of not being able to connect to my corporate Exchange server (running SP2 on SBS 2003). I was able to connect from this same computer when my machine was XP with Outlook 2007, so I figured the problem had to lie somewhere with Vista. I have all the patches for Vista and Office 2007 as of today (July 10, 2007), especially KB933493 and KB933493.
I wasn’t seeing any errors in the event logs, so I enabled Outlook’s logging by selecting Enable Logging (troubleshooting) from Outlook’s Tools – Options – Other – Advanced Options menu.
I’ve worked on this problem off and on, and hadn’t been able to make any headway, when I happened to find out about the Windows scaling factor. Once I turned it off in Vista, Outlook in cached mode connected to my Exchange server with no problem whatsoever!
You can disable/change the autotuning level by running the following command from a cmd prompt as an administrator
netsh int tcp set global autotuninglevel=disable
Obviously I didn’t want to leave the autotuninglevel=disable if I could make Outlook 2007 work with it enabled. To re-enable the autotuninglevel, type
netsh int tcp set global autotuninglevel=normal
some people have reported setting autotuninglevel=high allows Outlook to work correctly as well. I’m going to try it when I get home tonight, and I’ll let you know how it works out tomorrow.
To see which autotuninglevel you’re currently at, type
netsh interface tcp show global
According to KB935400, possible values are:
disabled -Fix the receive window at the default value.
highlyrestricted -Allow for the receive window to grow beyond the default value, but do so very conservatively.
restricted – Allow for the receive window to grow beyond the default value, but limit such growth in some scenarios.
normal – Allow for the receive window to grow to accommodate almost all scenarios.
experimental – Allow for the receive window to grow to accommodate extreme scenarios.
Note The experimental value can decrease performance in common scenarios. This value should be used only for research purposes.
[updated July 10, 2007]
I changed the autotuninglevel back to normal, then rebooted my machine. I had no problems connecting to my corporate Exchange server via 2007. Perhaps the need to disable the autotuninglevel is necessary only when the cached connection is first initiated.